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FORAMINIFERS OF THE PALMER DEEP REGION, ANTARCTIC PENINSULA, MODERN DISTRIBUTION AND PALEOCEANOGRAPHY OF THE LAST 13 KY
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University
By
Michael R. Sperling, M.S.
*****
The Ohio State University 2000
Dissertation Committee: Approved by Dr. Peter N. Webb
Dr. Lonnie G. Thompson Adviser Dr. Scott E. Ishman Department of Geological Sciences
Dr. Rosemary Askin
Dr. Gunter Faure UMI Number. 9994941
UMI
UMI Microform 9994941 Copyright 2001 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.
Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT
This research focused on foraminiferal assemblages from the Antarctic Peninsula, their composition in modem and Holocene sediments dependent on environmental conditions and postmortem processes, and their utility as paleoenvironmental proxies.
Additional independent proxies may be provided by chemical analysis of the shells and organic linings of benthic foraminifers in fixture studies as shown by reconnaissance investigations in this dissertation.
Two assemblages, living during the Austral autumn, have been recognized by the use of the vital stain Rose Bengal. The Bulimina aculeata assemblage, currently present in the Palmer Deep basins, has been proven to be robust to postmortem changes, and indicates open marine conditions during the austral summer, up-welling of Circumpolar
Deep Water (CDW) and increased primary productivity in the surface waters. The
Fursenkoina fusiformis assemblage seems to be opportunistic and thrives in environments that may be temporarily anoxic. These conditions seem to prevail in the Andvord drift and Gerlache Strait, recently bathed in Weddell Sea Transitional Water (WSTW), where the shallow water depth prevents deep-water circulation and hindering the oxygenation of the bottom waters. Additionally, a third assemblage is proposed in the research. It is hypothesized that the Miliammina arenacea assemblage lives during a different season of
II the year, since it is present only in the dead assemblages. The use of this assemblage as an indicator of hypersaline conditions, which may be generated by the formation of
Saline Shelf Water (SSW), is suggested.
The derived information about ecological adaptations of modem foraminifers was used for the interpretation of Holocene environments from the study area. The results confirm that the Antarctic Peninsula has been a region of rapid and variable climate fluctuation since the Last Glacial Maximum. Four major faunal turnovers have been recognized during the latest Pleistocene. The first occurrence of benthic foraminifers at
12.8 ky BP is interpreted as the time of final disintegration of an ice shelf over the study area. A rapid increase in diversity and abundances at 11.8 ky BP is thought to indicate the beginning of the Holocene in the Antarctic Peninsula region. The onset of the mid-
Holocene at 9 ky BP was accompanied by the last occurrence of the WSTW indicator F. fiisiformis in the Palmer Deep. Alternating dominance of the SSW indicator M. arenacea and CDW indicator B. aculeata during the last 3.4 ky points to variable and fast changing environmental conditions. The previously observed warming over the last 50 years in the study area may thus be a part of the natural climatic variability o f the Antarctic Peninsula.
Ill Dedicated to my wife Renate, and son Felix.
IV ACKNOWLEDGMENTS
I wish to thank my adviser. Dr. Peter N. Webb for his guidance and
encouragement throughout this research. I am grateful to Dr. Scott Ishman, Rosemarie
Askin, Gunter Faure, and Lonnie Thompson for stimulating discussions and reviews of
my dissertation draft. Thanks goes to Dr. Patrick Quilty, Eugene Domack, Amy Leventer,
Charlotte Sjunneskog, Fiona Taylor, and Stefanie Brachfeld for providing copies o f their
unpublished manuscripts. I also thank Thomas Janecek, at the Antarctic Marine Geology
Research Facility, for his assistance in obtaining core samples used in this research.
Thanks goes to ODP Scientific Party for data and samples from Leg 178 and to Prof. Dr.
Hemleben for samples from core MC529 of the Ionian Basin.
This research was financially supported in part from National Science Foundation
grants provided to Dr. Scott E. Ishman (DPP-9615669) and Dr. Peter N. Webb (DPP-
9420475). Additional support was provided through grants from the Friends of Orton
Hall and Geological Society of America. VITA
February 14, 1966...... Bom — Bad Kreuznach, Germany
1997 ...... M.S. Geology & Mineralogy — Eberhard Karls Universitat Tübingen, Germany
1997 — Present...... Ph.D. Candidate — The Ohio State University Columbus, Ohio
PUBLICATIONS
Sperling, M., 1998. Benthic foraminifers as indicators of oxygen-depleted waters associated with the Holocene eastern Mediterranean Sea sapropel SI. In: Abstracts with Programs — Geological Society of America. Vol. 30, no. 7. p. 27.
Sperling, M., 1998. Modem benthic foraminifers from the Palmer Deep Basins. In: „Holocene Paleonvironmental Change Along the Antarctic Peninsula: A Test of the Solar / Bi-Polar Signal". LMG98-02 Post-Cruise Report, USAP 1998, pp. 11- 14.
Sperling, M., & ODP Scientific Party, 1999. Paleoclimatic changes in the Bellingshausen Sea during the Holocene as recorded by benthic foraminifers from ODP LEG 178. In: Programme & Abstracts — 8th International Symposium, Victoria University Wellington, New Zealand, p. 289.
FIELDS OF STUDY
Major Field: Geological Sciences
VI LIST OF TABLES
Table Page
2.1. Varimax Principal Component Scores of living benthic foraminiferal Q-mode assemblages from the study area. Dominant and associated species (scores > 0.8) are outlined ...... 55
2.2. Varimax Principal Component Loadings of living benthic foraminiferal Q-mode assemblages from the study area. The highest loading for each station is outlined ...... 56
2.3. Varimax Principal Component Scores of benthic foraminiferal Q-mode assemblages from the study area. Dominant and associated species (scores > 0.8) are outlined ...... 60
2.4. Varimax Principal Component Loadings of benthic foraminiferal Q-mode assemblages from the Palmer Deep region. The highest loading for each station is outlined ...... 61
2.5. Proposed assemblages in the study area, named after the underlined species. Taxa in brackets are removed from the potential fossil data se t...... 69
2.6. Average standing stock (living tests), benthic foraminiferal accumulation rates (BEAR, dead tests), and Preservation Index (PI) of the most abundant agglutinated species from the study area, ordered by increasing preservation potential...... 78
2.7. Average standing stock (living tests), benthic foraminiferal accumulation rates (BEAR, dead tests), and Preservation Index (PI) of the most abundant calcareous species from the study area, ordered by increasing preservation potential ...... 82
3.1. Listing of selected references recording foraminiferal organic linings with taxonomic classification ...... 88
Vll 3.2. Characteristics o f the three types of linings encountered in this study. Note that diameter, breath, and # o f chamber are estimates and not based on statistically proven data. It is suggested that C. lobatulus and T. intermedia can be distinguished from each other by these parameters...... I l l
3.3. Occurrences of linings and foraminiferal counts of composite samples. Counts o f foraminiferal tests were performed on one set o f samples. The total number of tests counted in each interval are shown in brackets. Backup samples were treated with HF to investigate the occurrences of linings ...... 114
4.1. Energy Dispersive Spectral analysis of the outer test walls of Haplophragmoides sp., T. intermedia M. arenacea, F. fiisiformis, and B. aculeata. Note that Haplophragmoides sp. and T. intermedia have high iron contents in living (8.77-10.04 Mol/%) and low in dead specimens (0.09-2.73 Mol/%) ...... 129
5.1. Species composition of Holocene foraminiferal Q-mode assemblages o f cores 1098 and 1099 from the Palmer Deep basins. Principal Component Number, and with dominant and important associated species outlined are given ...... 161
5.2. Benthic foraminiferal accumulation rates (BEAR), standing stock (living specimens), and preservation index (PI, standing stock/BFAR X 100) from surface samples...... 169
6.1. Benthic foraminiferal accumulation rates (BFAR) and foraminiferal diversity o f JPC18 from the Andvord drift and JPC28 from the Gerlache Strait. Modem BFAR and diversity from surface samples o f Andvord drift are given for comparison ...... 206
6.2. Species composition of Late Holocene foraminiferal Q-mode and R-mode assemblages o f core JPC18 from the Andvord Drift. Principal Component No., dominant and important associated species (outlined) are given ...... 210
6.3. Species composition of Late Holocene foraminiferal Q-mode and R-mode assemblages o f core JPC18 from the Andvord Drift. Principal Component No., dominant and important associated species (outlined) are given ...... 215
vm LIST OF FIGURES
Figure Page
1.1. Mean annual summer sea-level temperatures for the Antarctic Peninsula. After Reynolds (1981) ...... 3
1.2. Deep water mass distribution in along the western side of the Antarctic Peninsula and distribution of dominant benthic foraminifer assemblages (From Ishman & Domack, 1994)...... 5
1.3. Generalized surface sediment type distributions for the western side of the Antarctic Peninsula (from Anderson et al., 1980, in: Ishman & Domack, 1994) ...... 7
1.4. Top: Location of Palmer Deep (from Barker et al., 1999). Bottom: Bathymetric map o f the study area. ODP Legs 1098 and 1099 are indicated. Map after Leventer ef a/. (1996)...... 10
1.5. Bathymetry o f the southern Gerlache Strait. Glacial drainage pattern and divides and position of cores NBP99/3 JPC 18 and JPC28 are indicated. After Harris et al., 1999 ...... 12
2.1. Hypothetical scheme showing variation of microhabitat depth of infaunal taxa as a function of the depth o f a critical level in the sediment. Figure from Sen Gupta (1 9 9 9 )...... 30
2.2. Simplified relationship between biocoenoses and thanatocoenoses (based on Murray, 1991)...... 32
2.3. Sketch showing habitats of benthic foraminifers and various postmortem processes that may lead to mixed faunas. Figure from Sen Gupta (1999)...... 34
2.4. Foraminiferal numbers (FN) from core PD22 of Andvord Bay. Data are from Domack et al. (1 9 9 3 )...... 36
2.5. Map of the study area showing surface sample locations. Palmer Deep transects PDl-3, Andvord drift transect ADI and positions of grab sample and long sediment core stations ...... 40
ix 2.6. Overview of the foraminiferal parameters utilized in this study: Standing stock, BFAR, Preservation index. Diversity, biocoenoses and thanatocoenoses ...... 44
2.7. Standing stock (# of living specimens/cm^yf% top), benthic foraminiferal accumulation rates (BFAR, bottom), and diversity (#species) o f foraminiferal assemblages from the surface samples. Lines are second order polynomial trend lines ...... 46
2.8. Palmer Deep Transect 1, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. Note the transition from F. earlandi dominated to B. aculeata dominated assemblages and the peaks of F. earlandi "Live" between 0.5 und 1 cm core depth ...... 48
2.9. Palmer Deep Transect 2, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. The most abundant species F. earlandi / 3. pseudopunctata o f each station are rare in the dead assemblages, whereas B. aculeata shows a reverse phenomenon ...... 49
2.10. Palmer Deep Transect 3, showing vertical distribution of he most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. In station G33 B. pseudopunctata and F. earlandi show peak abundances at the very top ...... 50
2.11. Andvord drift transect, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. "Live" F. Jusiformis and B. pseudopunctata are abundant at the uppermost centimeter, but diminish down core ...... 51
2.12. Vertical distribution of the most abundant foraminifers in G79 (Top), and of N. iridea, P. bulloides, and H. canariensis in G21, G37, and G67, respectively (per cm^). Note that "Live" G. biora and C. parkerianus are most abundant at the sediment surface and decrease exponentially down core ...... 52
X 2.13. Spatial distribution of PC A assemblages in the study area. Top: Biocoenoses. Bottom: Thanatocoenoses (potfossil). Note that the B. aculeata / B. pseudopuncta assemblages occupy the Palmer Deep basins and that the Fursenkoina spp. live assemblages are replaced by the M arenacea dead assemblage. T. intermedia dead (PC3) is dominant in the Andvord drift...... 57
2.14. Vertical distribution of the most abundant agglutinated species in GC15 from Palmer Deep basin I and KC27 from basin II (per cm^). M arenacea fluctuates with no apparent core depth trend...... 63
2.15. Vertical distribution of the most abundant agglutinated species in KC17 from Palmer Deep basin III and JPC18 from the Andvord drift (per cm^). KC17 depicts exponential decreases o f P. eltaninae and H. parkerae down core. The vertical distribution of M arenacea and T. intermedia seems to be independent of the core depth in KC17 and JPC28...... 64
2.16. Vertical distribution of the most abundant calcareous species in GC14 from Palmer Deep basin I and KC27 from basin II (per cm^). Note that B. aculeata is by far the most numerous species and has the most continuous record ...... 66
2.17. Vertical distribution of the most abundant calcareous species in KC26 from Palmer Deep basin III and JPC18 from Andvord drift (per cm^). B. pseudopunctata is present in KC26 only in the upper 0.8 m ...... 67
3.1. Percentages of Rotaliina (Calcareous taxa) in cores JPC28 from the Gerlache Strait, 1099 from Pahner Deep basin III, and 1098 from basin 1, and composite samples (S) selected for HF treatment. Lines have been smoothed by four-point average...... 103
3.2. 1-5: Acid resistant remains of calcareous foraminifers. 1, B. aculeatea\ 2, P. bulloides', 3, B. pseudopunctata', ;4, left: F. fiisiformis', right: C. lobatulus (megalospheric); 5, N. iridea. Palmer Deep basin I, G21.6: S. biformis. Palmer Deep basin I, GC15 (1.85 m ) ...... 106
3.3. 1, 3-5, 7: C. lobatulus microspheric linings, Gerlache Strait, JPC28 lower section. 2,6: C. lobatulus calcareous tests; 2, Bismark Strait, G58, outer shell partially dissolved; 6, Andvord drift, G68, note the pores at the apertural sid e ...... 107
XI 3.4. 1,3-6: C. lobatulus linings (megalospheric); Gerlache Strait, JPC 28, lower interval; 2, apertural view, 3, detail section o f 2. 2: T. intermedia lining, Gerlache Strait, JPC 28, lower interval...... 108
3.5. 1-2: T. intermedia, apertural view . 1, lining with pyrite framboids in the last three chambers; 2, agglutinated test 3-6: T. intermedia, dorsal view. 3, lining with damaged final chamber; 4, agglutinated test with broken rim; 5, translucent agglutinated test with visible lining; 6, outer shell removed with HF. 1,2,5-6: Gerlache Strait, JPC28 upper interval; 2,4: Palmer Deep basin 1, 1098b (18.67 m bsf)...... 109
3.6. 1-2: T. intermedia agglutinated test. 1, apertural side view; 2, detail section of 1 showing exposed lining. 3: T. intermedia lining with impressions of inorganic test material on lining. Palmer Deep basin I, 1098b (18.67 mbsf) ...... 110
3.7. Number of linings and tests of T. intermedia (per cc), and occurrences o f C. lobatulus and S. biformis linings in core GC15 firom Palmer Deep basin I. Note that linings have been investigated in backup samples. Linings o f T. intermedia, present in almost every sample, become more abundant below 1.3 m core depth. C. lobatulus and S. biformis were encountered in very low numbers, thus only the occurrences are shown ...... 113
4.1. Schematic in situ disintegration model of agglutinated foraminifers in surface samples firom the study area. The disintegration processes are thought to occur above and within the sulfate reduction zone. Iron oxides, presumably used by agglutinated foraminifers as cement and outer wall material, are converted to ironsulfides, resulting in bleaching and destruction of the agglutinated tests. The sulfate reduction zone is positioned in variable sediment depths in the study area, indicated by the occurrence of firamboidal pyrite crystals...... 120
4.2. SEM images of M. arenacea, Haplophragmoides sp., and T. intermedia, and examples o f spectra derived by energy dispersive X-ray spectrometer (EDS). Note that iron content o f M. arenacea was below detection limit (-0.5 Mol/%) ...... 126
5.1. Bathymetric map of the study area. Position of surface samples (small gray dots) and ODP sites 1098 and 1099 are indicated. Map after Leventer et al. (1 9 9 6 )...... 138
XU 5.2. Synthesis o f the Antarctic Peninsula glacial development and associated environmental changes since the Last Glacial Maximum. From Taylor & Sjunneskog (submitted) ...... 139
5.3. Schematic model explaining fluctuations in magnetic susceptibili^ during the Late Holocene in the study area. Note the 200 years interval of low primary productivity (Leventer gf u/. 1996) ...... 142
5.4. Lithostratigraphic column for 1098, summarizing lithology percent biogenic component for 1098A, 1098B, and 1098C. Magnetic susceptibility data are from Hole 1098B ...... 144
5.5. Lithostratigraphic column for 1099, summarizing lithology, percent biogenic component, and magnetic susceptibility data of 1099Aand 1099B...... 145
5.6. Age model of core 1098b (from Domack et al., in press). Ages given are corrected ages. Note the loss of almost 1000 years at the base o f turbidite 2 ...... 149
5.7. Sedimentological data for core 1099 include dry weight (<63 pm), occurrence o f clasts (<355 pm), gypsum and mollusks. Magnetic susceptibility data (MS) from Barker et al., (1999). Mud turbidites are characterized by low to negligible dry weight, clast rich intervals indicate sandy turbidites or diamictons...... 152
5.8. Occurrences of foraminifers in core 1098 from Palmer Deep basin I. Turbidite units Tl-3 and the diamicton unit are indicated...... 154
5.9. Figure 5.9. Benthic foraminiferal accumulation rates (BFAR) and diversity from the 1098 (Palmer Deep basin I). Thicker black lines indicate a four-point smoothing, reference lines modem values from surface samples. Age model after Domack etal. (in press)...... 156
5.10. Occurrences of foraminifers in core 1099 from Palmer Deep basin III. Turbidites and the proposed diamicton are indicated...... 158
5.11. Diversity and benthic foraminiferal accumulation rates (BFAR) from the Palmer Deep basin III (core 1099). Thicker black lines indicate a four-point smoothing. Reference lines show modem values from surface samples. Age model after Domack et al. (in press)...... 159
X lll 5.12. Q-mode foraminiferal assemblages (3-component model) firom core 1098 of Palmer Deep Basin I. Thick black lines are four-point average trend lines. Loadings higher than 0.4 indicate the dominance of a component. Early/mid-Holocene and mid-/late Holocene boundaries as suggested by Domack et al. (in press) are indicated...... 162
5.13. Q-mode foraminiferal assemblages (3-component model) fi-om core 1099 of Palmer Deep basin III. Thick black line is four-point average trend line. Loadings higher than 0.4 indicate the dominance of a component. The early/mid-Holocene boundary as suggested by Domack et al. (in press) and the possible diamicton are indicated...... 164
5.14. Diversity and benthic foraminiferal accumulation rates (BFAR) of core 1098 fi"om Palmer Deep basin I and core 1099 firom basin III. Lines have been smoothed by four-point running average, age model after Domack et al. (in press). Early/mid- Holocene and mid-/late Holocene boundaries as suggested by Domack et al. (in press) are indicated...... 165
5.15. Foraminiferal test accumulation rates of the most abundant species in 1098 firom Palmer Deep basin I and 1099 firom Palmer Deep basin III. Thick black lines indicate values firom 1098, grey lines specify values firom 1099, both smoothed by four-point running average. Vertical reference lines indicate modem values firom surface samples. Age model firom Domack et al. (in press)...... 167
5.16. Q-mode foraminiferal assemblages (3-component model) firom Palmer Deep basin I (1098) and III (1099). Lines have been smoothed by four-point (1098) and two- point (1099) moving average. Age model firom Domack et al. (in p ress.)...... 173
5.17. Q-mode foraminiferal assemblages firom core 1098 of Palmer Deep basin I and summer insolation at solstices calculated after Berger (1978) for the GISP2 and Palmer Deep latitudes ...... 176
5.18. Comparison of the benthic, planktic and sedimentary record of core 1098 fi’om the Palmer Deep basin I. CDW: circumpolar deep water, WSTW: Weddell sea transitional water, SSW: saline shelf water, MS: magnetic susceptibility, MAR: mass accumulation rates, IRD: ice rafted debris. Diatom data firom Sjunneskog & Taylor (submitted) and Taylor & Sjunneskog (submitted), MS data firom Brachfeld et al. (submitted), age model, MAR and IRD data firom Domack et a/, (in press)...... 179
xiv 5.19. Q-mode foraminiferal assemblages (3-component model) firom 1098 o f Palmer Deep basin I. Lines have been smoothed by four-point moving average. Loadings higher than 0.4 indicate the dominance of a component. Age model firom Domack et al. (in press.)...... 183
5.20. Comparison of the 1098 record firom Palmer Deep basin I with the Andvord drift record (JPC18, chapter 6). Note that activity of the CDW indicator B. aculeata is confined to the late Holocene in both locations. During the mid-Holocene, the Weddell Sea Transitional Water (WSTW) and Saline Shelf Water (SSW) were prevalent in the study area, as indicated by F.fiisiformis and M arenacea^ respectively...... 190
6.1. Location and bathymetry of study area in southern Gerlache Strait, Antarctic Peninsula. Glacial drainage patterns and divides are after Williams et al. (1989), the map after Harris et al. (1999). Positions of NBP 99/3 cores JPC 18 in the Andvord drift and JPC28 in the Gerlache Strait are indicated...... 193
6.2. Stratigraphie columns and dry weight values (>63 um) o f JPC 18 and JPC28. Occurrences of dropstones, fecal pellets and niussels firagments are indicated. Note the uniform fluctuations o f the dry weight, which suggests that sedimentation processes remained relatively constant...... 200
6.3. Proposed age models o f JPC 18 and JPC28. Magnetic susceptibility data have been used to fit the age model o f 1098 (Domack et al., in press). Mid-/late Holocene boundary in 1098 as suggested by Domack et al. (in press) is indicated...... 201
6.4. Occurrences of foraminifers in JPC18 from Andvord drift. Note the continuous record o f M. arenacea and T. intermedia, and the occurrence of the Palmer Deep basin fauna including B. aculeata and B. pseudopunctata in the upper 10 m o f the core ...... 203
6.5. Records of benthic foraminiferal accumulation rates (BFAR) and diversity from the Andvord drift (JPC 18). Thicker black lines indicate a four-point smoothing, reference lines modem values from surface samples. The proposed age model is given for comparison, the mid-/late Holocene boundary (Domack et al., in press) indicated...... 205
XV 6.6. Occurrences of foraminifers in JPC28, grouped by their distribution down core. Note the continuous record o f M arenacea and T. intermedia and the increasing number of species down core ...... 207
6.7. Records of benthic foraminiferal accumulation rates (BFAR) and diversity from the Gerlache Strait (JPC28). Reference lines indicate modem values in surface samples from the nearby Andvord drift. Black lines indicate four-point smoothing. The mid-/late Holocene boundary (Domack et al., in press) is indicated...... 208
6.8. Q-mode foraminiferal assemblages (3-component model) from core JPC 18 o f Andvord Bay. Thicker black lines indicate a six- point smoothing. Loadings higher than 0.4 indicate the dominance of a component. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated...... 211
6.9. R-mode foraminiferal assemblages (3-component model) from core JPC18 o f Andvord drift. Thicker black lines indicate a four- point smoothing. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated...... 211
6.10. Q-mode foraminiferal assemblages (3-component model) from core JPC28 o f Gerlache Strait. Thicker black lines indicate a six- point smoothing. Loadings higher than 0.4 indicate the dominance of a component. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated...... 216
6.11. R-mode foraminiferal assemblages (2-component model) from core JPC28 o f Gerlache Strait. Thicker black lines indicate a four-point smoothing. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated. Note high scores of B. aculeata (RPC2) during the late Holocene and latest mid-Holocene ...... 217
6.12. BFAR and diversity from the Andvord Drift and Gerlache Strait plotted against the preliminary age model. Lines have been smoothed by four-point running average, references lines indicate modem values from surface samples in the Andvord drift ...... 220
XVI 6.13. Down-core fluctuations of WSTW and CDW faunas from the Andvord drift (JPC18) and southern Gerlache Strait (JPC28). Mid-/late Holocene boundary as proposed by Domack et al. (in press) in the Palmer Deep is indicated. Lines have been smoothed by six-point (WSTW faunas) and four-point average (CDW faunas)...... 224
6.14. Paleoclimate synthesis of the Andvord drift and Gerlache Strait. Lines have been smoothed according to methods used in previous figures. Reference lines indicate modem values of BFAR and diversity in the Andvord drift...... 230
7.1. Top: scanning electron microscope images of euhedral gypsum crystals from ODP core 1098b (28.6 m core depth) from Palmer Deep basin I. Bottom: Profiles of interstitial water chemistry, total organic carbon (TOC) in core 1098c (Barker et al., 1999) and occurrence of gypsum in core 1098b ...... 235
7.2. Bathymetric map of the study area. Dots indicate cores ODP 1098b, LMG98/2 KC27, and PD92-05 (PD05). Map after Leventer er fl/. (1 9 9 6 )...... 240
7.3. Top: 1, Gypsum of rose-like crystal aggregation from core PD05; 2, Detail picture of 1, showing the diatom fiustules in gypsum. Bottom: Abundances of Rotaliina (calcareous foraminifers) and occurrence of gypsum in cores KC27 and PD05 from frie sill between Palmer Deep basins II and III...... 242
7.4. Top: gypsum from core MC529 from the Ionian Sea. Bottom: dominant calcareous foraminifers and weight percentage of gypsum in core MC528 from the Ionian Basin (eastem Mediterranean). Position of sapropel SI is indicated...... 245
8.1. Top: spatial distribution of biocoenoses in the study area, and proposed deep-water mass distribution. Bottom: downcore distribution o f the most abundant foraminifers in cores G 33-34 ...... 249
8.2. Down core distribution of the most abundant benthic foraminifers in core 1099 from Palmer Deep basin III. Note the differentiated pattern in the “diamicton”,M. arenacea appears evenly distributed, but B. aculeata and F. fusiformis show high frequency fluctuations ...... 253
x v ii 8.3. Proposed seasonal assemblages of the Palmer Deep region. 1. B. aculeata, 2. B. pseudopunctata, 3. P. eltaninae, 4. B. bulloides, 5. F. earlandi, 6. R. subdentaliniformis, 7. M. arenacea, 8. F. fusiformis, 9. T. intermedia, 10. S. biformis...... 255
8.4. Comparison of the 1098 record from Palmer Deep basin I with the Andvord drift record (JPC18, see chapter 18). Note that activity o f the CDW indicator B. aculeata is confined to the late Holocene in both locations. During the mid-Holocene, the Weddell Sea Transitional Water (WSTW) and Saline Shelf Water (SSW) were prevalent in the study area, as indicated by F. fusiformis and M arenacea, respectively...... 259
8.5. Synthesis and comparison with other climate records. 1. Shevenell etal. (1996), 2. Taylor & Sjunneskog (submitted), Sjunneskog & Taylor (submitted), Domack et al. (in press), 3. this study (Chapter 5), 4. this study (chapter 6), Yoon et al. (2000), Bjôrck et a/. (1991)...... 261
B 1. 1. Portatrochammina eltaninae Echols. 2. Trochammina interrmedia Rhumbler. 3. Spiroplectammina biformis (Parker & Jones). 4. Haplophragmoides parkerae (Uchio). 5. Reophax dentaliniformis Brady. 6. Reophax subdentaliniformis Parr. 7. Miliammina arenacea (Chapman)...... 280
B2. \. Astrononion echolsi Kennett, 1967. 2. Pullenia bulloides (d'Orbigny). 3. Bolivina pseudopunctata Hoeglund. 4. Fursenkoina fusiformis. 5. Fursenkoina earlandi (Parr). 6. Bulimina aculeata d'Orbigny. 7. Globocassidulina biora (Crespin). 8. Nonionella iridea Heron & Earland...... 282
xvm TABLE OF CONTENTS
A bstract...... ii
Dedication...... iv
Acknowledgments ...... v
V ita...... vi
List of Tables...... vil
List of Figures ...... ix
Chapters:
1. Introduction ...... 1
1.1. Setting ...... 1 Topography and Climate ...... 1 Geology and Tectonics ...... 2 Oceanography ...... 4 Sediment distribution ...... 6 Glacial history of the Antarctic Peninsula...... 6 The Palmer Deep basins...... 9 The Andvord drift ...... 11 1.2. Benthic foraminifers...... 13 Previous work ...... 13 Antarctic foraminifers...... 15 Post-burial taphonomic changes ...... 16 Organic foraminiferal linings ...... 17 Biomineralization of benthic foraminifers...... 18 Holocene foraminifers ...... 20 1.3. Methodology (Overview) ...... 21 Sample selection ...... 21 Sample processing ...... 22 Processing o f foraminiferal data ...... 24
XIX 2 . Modem foraminifers firom the Palmer Deep region ...... 25
2.1. Summary...... 25 2.2. Introduction ...... 27 The use o f Rose Bengal ...... 27 Microhabitat o f benthic foraminifers...... 28 Biocoenosis and thanatocoenosis ...... 31 Fossilization potential...... 35 Statistical treatment of foraminiferal assemblages...... 37 2.3. Objectives...... 38 2.4. Material & Methods...... 39 Field collection ...... 39 Foraminiferal data acquisition and processing...... 41 2.5. Results...... 45 Standing stock, BFAR, and diversity ...... 45 Vertical distribution of living (Rose Bengal stained) foraminifers 47 Vertical distribution of dead foraminifers...... 53 Q-mode Principal Component Analysis (PCA)...... 54 Long sediment cores ...... 62 2.6. Discussion & Conclusions ...... 68 Preservation potential o f agglutinated foraminifers ...... 76 Dissolution resistance of calcareous foraminifers...... 79 Fossil assemblages: How much information will be preserved?...... 81
3. Organic foraminiferal linings ...... 85
3.1. Summary...... 85 3.2. Introduction ...... 96 3.3. Classification...... 90 3.4. Methods...... 91 Previous methods — a damage report ...... 91 Proposed standardized methods...... 95 3.5. Objectives...... 101 3.6. Results...... 104 Taxonom y ...... 104 Linings in Holocene sediments ...... 112 3.7. Discussion & Conclusions ...... 115
4. Biomineralization in foraminifers...... 117 4.1. Summary...... 117 4.2. Introduction ...... 118 4.3. Material and Methods...... 123 4.4. Results...... 125
XX Iron content of agglutinating foraminifers ...... 125 Mg/Ca ratios of calcareous foraminifers ...... 128 4.4. Discussion & conclusions ...... 128 Outer wall material of agglutinated foraminifers ...... 128 The role o f iron in the stability o f agglutinated tests ...... 130 Iron in agglutinated tests: possible paleoenvironmental applications ... 131 Mg/Ca ratios of calcareous foraminifers ...... 132
5. The Holocene of the Palmer Deep basins ...... 134 5.1. Summary...... 134 5.2. Introduction ...... 135 5.3. Objectives...... 141 5.4. Material and Methods...... 143 5.5. Results...... 151 Stratigraphy of core 1099 (Palmer Deep basin III)...... 151 Occurrences, diversities and BFAR...... 153 Principal component analysis...... 160 5.5. Discussion ...... 163 Diversity and BFAR...... 163 Principal component analysis...... 170 5.6. Paleoclimate synthesis...... 175 The bipolar insolation signal ...... 175 Comparison with other proxies from core 1098 ...... 177 The Younger Dry as (12.7-11.6ky B P ) ...... 181 Early Holocene (11.6 to 9ky B P )...... 185 Mid-Holocene (9-3.4 ky BP)...... 188 The late Holocene (3.4 — present)...... 189
6. The Holocene of the Andvord drift and Gerlache Strait...... 191 6.1. Summary...... 191 6.2. Introduction ...... 192 6.3. Objectives...... 196 6.4. Material...... 197 6.5. Results...... 198 Stratigraphies and age m odels ...... 198 Foraminiferal occurrences, diversity and BFAR...... 202 Principal Component Analysis...... 209 6.5. Discussion & Conclusions ...... 218 BFAR and Diversity...... 218 Statistical Analysis...... 222 Paleoclimate Synthesis...... 227
7. Possible authigenic gypsum from the Palmer Deep basins ...... 231 7.1. Summary ...... 231 7.2. Introduction ...... 232
xxi 7.3. Previously reported gypsum from marine sediments ...... 233 7.4. Objectives ...... 239 7.5. Materials & Methods ...... 239 7.6. Results ...... 241 7.7. Discussion & Conclusions ...... 241
8. Summary ...... 246 8.1. Questions as outlined in the dissertation proposal ...... 247 8.2. Modem foraminifers ...... 254 8.3. Holocene foraminifers ...... 256 8.4. Recommendations and future work ...... 258
APPENDICES
A. Surface sample locations, environmental parameters, foraminiferal counts, diversity, standing stock, and benthic foraminiferal accumulation rates used in chapter 2. Sedimentation rates are from Leventer et al. (1996), Domack & McLennan (1996), and Kirbyet al. (1 9 9 8 ) ...... 267
B. List of abbreviated benthic foraminiferal systematics for modem and Holocene samples from the Antarctic Peninsula including species name, original citation and SEM images of important species. The list does not include poorly represented species or obviously reworked shallow water form s ...... 276
C. Foraminiferal counts (#/cc) of cores GC14 / GC15 (Palmer Deep basin I), KC26 (Palmer Deep Basin II), and KC17 / KC27 (Palmer Deep basin III). The list does not include poorly represented or obviously reworked shallow water form s...... 284
D. Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BFAR) (#/cm^lty'^), Varimax Principal Component Loadings o f Holocene benthic foraminiferal Q-mode assemblages, and occurences o f gypsum in core GDP 1098b from the Palmer Deep basin I. List includes ordy species used in the potential fossil data se t ...... 299
E. Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BFAR) (#/cm^Ity'^), Varimax Principal Component Loadings o f Holocene benthic foraminiferal Q-mode assemblages, and occurences o f gypsum in core GDP 1099a/b from the Palmer Deep basin III. List includes only species used in the potential fossil data set 323
x x ii F. Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BFAR) (#/cm^ky'*), Varimax Principal Component Loadings of Holocene benthic foraminiferal Q-mode assemblages, and Varimax Principal Component Scores o f Holocene benthic foraminiferal R-mode assemblages of core NBP99/3 JPC18 from the Andvord drift. List includes only species used in the potential fossil data se t...... 332
G. Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BFAR) (#/cm^ky'^), Varimax Principal Component Loadings of Holocene benthic foraminiferal Q-mode assemblages, and Varimax Principal Component Scores o f Holocene benthic foraminiferal R-mode assemblages of core NBP99/3 JPC28 from the Gerlache Strait. List includes only species used in the potential fossil data se t...... 344
LIST OF REFERENCES...... 350
xxm C H A P T E R 1
INTRODUCTION
1.1. Setting
The Antarctic Peninsula is a glaciated mountain region of West Antarctica, which extends 1,930 km north toward South America. It was originally named Palmer Land for
Nathaniel B. Palmer, an U.S. captain who explored the region in 1820. By international agreement in 1964 it was named the Antarctic Peninsula.
Topography and Climate
The Antarctic Peninsula is a long, dissected plateau, standing at -900 m elevation at its northern end (63.5°S) and rising to 1750 m at 64°S at its southern end (Elliot, 1997).
The central plateau is bordered by longitudinal Çords and islands. The recent ice cover is relatively thin mostly a few hundred meters thick. Ice shelves are small and sparse, and few large icebergs are produced (Barker et al., 1999). The glaciers drain rapidly through steep icefalls at the heads of Qords. The greatest relief is in the inner-sheH region where
Qords reach water depths >1000 m, presmnably overdeepened by grounded ice (Barker et al., 1999). The Peninsula’s geographical setting of high mountains, small glaciers and steep
temperature gradients (Fig. 1.1) causes it to respond rapidly to climate fluctuations (e.g.
Pudsey et al., 1994). The Antarctic Peninsula acts as a major barrier to tropospheric
circulation, and its ice sheet currently receives almost four times the average Antarctic
continental sno'wfall (Reynolds, 1981; Drewry & Morris, 1992). However, modem
meltwater-influenced sediments are known only from the South Shetland Islands (Bart &
Anderson, 1995), and the climatic regime elsewhere is polar. Evidence exists that
grounded ice reached the continental shelf edge during the last glacial maximum,
although the exact extension is unknown (Ingolfsson et al., 1998). The coastal zone of
the Antarctic Peninsula is an area of unusual high rates of primary productivity during
spring blooms with a duration of less than two months (e.g. Leventer et al., 1996). Spring
phytoplankton blooms increase the downward flux of organic matter causing a strong
seasonal signal to the benthos even in the deep-sea (Deuser & Ross, 1989).
Geology and Tectonics
The setting of the Antarctic Peninsula is characterized by a mixture of calc-
alkaline plutonic and volcanic rocks, metasediments of an old accretionary prism, and
gneissic basement, reflecting a long history of subduction at the Pacific margin of
Gondwana (Birkenmajer, 1998; Hathway, 2000). The youngest exposed sediments
onshore are terrigenous and volcaniclastic sediments of mainly late Mesozoic age (Barker et al., 1999b). The subduction at this margin ended at 3-6 Ma with the progressive collision of segments of the Phoenix-Antarctic ridge crest at the trench (Larter & Barker,
1991a). The uplift of the outer margin continued after subduction in the collision segment
2 DRAKE PASSAGE
100 km
Study area JAMES ROSS ISLAND
BELLINGSHAUSEN 10 65' SEA a
ADELAIDE ISLAND
LARSEN ICE SHELF MARGUERITE BAY< 13
14
15 70°S WEDDELL # W s i l ^ O'BLUFF'^i ' SEA ■ALEXANDER 15 Xk ISLAND
8(f 75' 60 55 50'
Figure 1.1. Mean annual summer sea-level temperatures for the Antarctic Peninsula. After Reynolds (1981). (Barker et al., 1999). Links between subduction, uplift of the Antarctic Peninsula, and the onset of glaciation have been suggested (Elliot, 1997). The creation of a 2 km-high ridge of mountains is thought to have affected precipitation and local climate suffîciently to cause the development of an ice sheet (Barker et al., 1999).
Oceano graph V
Two deep water masses are prevalent in the study area. The Circumpolar Deep
Water (CWD) dominates the continental shelf to the southwest of Andvord Island (Fig.
1.2., Ishman & Domack, 1994). The CDW was described with a temperature range of
0.9°-2.1°C as relatively warm (e.g. Domack et al., 1993). The Bransfield region is dominated by Weddell Sea Transitional Water (WSTW) (Ishman & Domack, 1994), which is colder (-1.6 °-1.5 °C). A recent study showed little indication of significant exchange from the Bransfield Strait and the west Antarctic Peninsula shelf (Smith et al.,
1999). The latter authors observed a subdivision of the CDW into an upper and lower unit with a depth of 200-400 and >800 m, respectively. The relative shallowness of the upper
CDW is thought to cause a water mass structure that is essentially oceanic in origin
(Smith et al., 1999). The absence of cold and dense shelf bottom water along the
Antarctic Peninsula was thought to be due the presence of the upper CDW, which reduces the winter ice formation and the accompanying brine rejection (Smith et al.,
1999). The authors observed that the upper CDW mixes with the Saline Shelf Water, which provides a consistent deep source of salt and low oxygen water for the continental shelf of the west Antarctic Peninsula. 70°W Fursenkoina spp. Assemblage ELEPHANT
11)11 Bulimina aculeata Assemblage
SOUTHERN PACIFIC OCEAN
WEDDELL SEA TRANSITIONAL WATER
WEDDELL SEA
ADELAIDE I. MAP RONNE-RLCHfŒH ICE SHELF AMEHY ICE fÂARCUERITE BAY SHELF n (ALEXANDER BO®W ) WILKINS I.S. ' " 70^VNÇ / ROSS ICE SH ELF
Figure 1.2. Deep water mass distribution in along the western side of the Antarctic Peninsula and distribution of dominant benthic foraminifer assemblages (from Ishman & Domack, 1994). Sediment distribution
The distribution of modem sediments on the western side of the Antarctic
Peninsula has been described by several authors (Griffith & Anderson, 1989; Kennedy &
Anderson, 1986). The surface sediments of the area are composed of biogenic siliceous and hemipelagic muds that accumulated at extremely high rates of up to 0.52 cm/yr
(Domack et al., 1993, Leventer et al., 1996). Coarse grained sediments are distributed in close proximity to coastal and sea-ice settings (Fig. 5.3), since little sediment is currently being produced by the small tidewater glaciers in the region (Griffith & Anderson, 1989).
Primary productivity is high related to spring ice melting (e.g. Leventer et al., 1996), resulting in dominance of fine grained material and comparatively high Total Organic
Contents (TOC) in the sediment (e.g. Domack et al., 1993).
Glacial History of the Antarctic Peninsula
Onshore glacial evidence has been published by Birkenmajer (1992) and Elliot
(1997). The authors suggested early or middle Eocene as well as early and late Oligocene glaciations on the South Shetland Islands (northern Antarctic Peninsula). Late Miocene glacial deposits are found on Seymour Island. A late Miocene age for sediments on the
Weddell Sea margin was suggested, as well as a middle Miocene onset of glaciation on the Pacific margin (Bart & Anderson, 1995). It was assumed that the glacial history of the
Antarctic Peninsula is shorter than East Antarctica's, possibly providing a high-resolution record of glaciation back to 10 Ma (Barker et al., 1999). Siliceous Mud/Ooze ELEPHANT L Sand Gravel
SOUTHERN PACIFIC OCEAN
ANVERS
SiM/Oc^ WEDDELL SEA
LARSEN ICE SHELF MAP AREA.. HONNE-FILCHNER ICE SHELF AMEHY ICE SHELF
(ALEXANDER AhfTARCTlCA _ _ iM/O/% ) V/ILKINS I.S 70°V\L<.«^GEORGE VI LS. ROSS ICE SHELF
Figure 1.3. Generalized surface sediment type distributions for the western side of the Antarctic Peninsula (from Anderson et al., 1980, in: Ishman & Domack, 1994). SIM = siliceous mud; O = siliceous ooze; Or = gravel; S = sand; and M = mud. The Antarctic Peninsula was recognized as an important area for studying past
glaciation cycles because of its close proximity to the Antarctic Convergence and its
polar to sub-polar climatic gradient (Domack et al., 1995; Domack & Me Clennen, 1996;
Kirby et al., 1998). The sediments that accumulated since the Last Glacial Maximum
(LGM) on the peninsula shelf and Qords indicate development of glaciers and
paleoclimate evolution during the Holocene (Domack et al., 1991; 1993; 1995; Pudseyet
al., 1994; Leventer et aZ., 1996; Kirby et al., 1998).
During the last 50 years, the study area has undergone a marked increase
(~+2.5°C) in annual mean temperatures (summary in Leventeret al. 1996), resulting in sea-ice free conditions for at least 4 months per year and the disintegration of the northern parts of the Peninsula’s Ice Shelf (e.g. Doake et al., 1998). The same authors recognized a period of warming around 3 ky BP, which is thought to represent the tail end of the mid Holocene climate optimum in the study area. Much in debate are the environmental changes in the study area since the LGM (summary in Ingolfsson et al.,
1998). Evidence for a more extensive ice cover than today can be found all along the
Antarctic Peninsula (Ingolfsson et al., 1998), but the extension and timing of the deglaciation is poorly known. Apparently, the study area has experienced major climatic fluctuations, as opposed to the previous view that the Holocene was a period of relative stability. Oscillating glaciers may have destroyed evidence of earlier events making the interpretation of terrestrial records difficult. Ice-cores from the Antarctic Peninsula exist but are primarily from high altitudes and provide short duration records (e.g. Thompson et al., 1994). The Palmer Deep basins
Previous research in the Antarctic Peninsula focused on the outer shelf (Pudsey et al., 1994) and fjords (Domack et at., 1993; 1995, Shevenell et aL, 1996). Little work has been done on settings that mark an intermediary position between the full glacial conditions of the shelf edge grounding and interglacial conditions of the Qord heads. One such setting is the Palmer Deep, where relatively thick Holocene sediment accumulations
(-50-250 m) were recently discovered (Kirby et al., 1998, Rebesco et al., 1998). The
Palmer Deep region is located at the inner continental shelf west of the Antarctic
Peninsula (Fig. 1.4). It consists of three fault-bounded basins oriented in SW-NE direction. Basin I is the shallowest (~ 1000 mbsf.) and smallest seafloor depression in the north. Previous studies in the Palmer Deep, based on short core records (< 12 m), demonstrated a climatic optimum before 2.5 ky BP (Leventer et al., 1996, Kirby et al.,
1998). Drilling of ODP Leg 178 Site 1098b yielded an unparalleled Holocene record for the southern ocean (Domack et al., in press; Sjunneskog & Taylor, submitted; Taylor &
Sjunneskog, submitted), providing the first record from the Antarctic Peninsula that spans the entire sequence from the termination of the LGM to the present. In chapter 5 of this dissertation the benthic foraminifers of ODP cores 1098b and core 1099 from the adjacent basin m are investigated, using benthic foraminiferal accumulation rates and statistical analysis of assemblages as proxies for paleocanography and paleoclimatology. 300 : 300 :
6 4 S
^ . ' Palmer Deep ' 600 30Q-;
so km
66 67 W 65 63
Palmer Deep basins
*{. site
64" 30' W 64" 20' W 64" 10'W
Figure 1.4. Top: Location of Palmer Deep (from Barker et al., 1999). Bottom: Bathymetric map of the study area. ODP Legs 1098 and 1099 are indicated. Map after Leventer et al. ( 1996).
10 The Andvord drift
Previous studies suggested that currently very little sediment is produced by
tidewater glaciers along the Pacific margin of the Antarctic Peninsula (e.g. Griffith &
Anderson, 1989), resulting in a very thin postglacial sediment cover. Recent high
resolution seismic surveys however reveal more than 40 m of Holocene sediment cover
in the southern Gerlache Strait and in front of Andvord Bay (Harris et al., 1999). These
authors claim the discovery of a “new type of inner shelf, glacial marine deposystem”
called the “Andvord drift” at the entrance of Andvord Bay (Fig. 1.5). Although deposited
in only 300-500 m water depth, the fine-grained sediments are similar to deep-sea
deposits (Harris et aL, 1999). The term “drift” applied in glacial geology is defined as all
rock material that is transported by a glacier or by running water emanating from the
glacier (Bates & Jackson, 1980). The rate of carbon accumulation in the Andvord drift
was compared to the highest rates reported for the southwestern Ross Sea (Harris et at.,
1999). Because the processes contributing to sedimentation of the drift reflect a
combination of physical and biological processes, it was suggested that the Andvord drift contains an exceptional high-resolution record of these processes (Harris et aL, 1999). So far, the drift has been studied only at a distal, low-resolution site spanning the last ~3 ky
(Domack et aL, 1993). The recovery of a core from the center of the drift where the
sediment thickness exceeds 40 m would clearly provide a much higher resolution record, and would contribute to our knowledge of paleoclimate development in the region, as suggested by Leventer et aL, (1996). In chapter 6 of this dissertation the benthic foraminiferal assemblages from the Andvord drift are used as proxies for paleocanography and paleoclimatology.
11 CO o _ Scuth Shetland W8fS JPC28 Islands ^ • bànd s StLdy sfCe .0 ' .
d?-JPC18^ Arr^ers Island hicnc Wïencké Islaiid:
Lcrsen S
Lemalce Island
CO J g- s
AmofCitcc Stuc,- >-T site 10 km
63° 00’ W 62° 40" W 62* 20'W
Figure 1.5. Bathymetry of the southern Gerlache Strait. Glacial drainage pattern and divides and position of cores NBP99/3 JPG 18 and JPC28 are indicated. After Harriset aL, 1999.
12 1.2. Benthic Foraminifers
Previous work
Benthic foraminifers are widely employed as paleoenvironmental proxies because of their wide distribution in most marine settings. Known since the Cambrian, foraminifers diversified rapidly and are present in a variety of environments, from shallow brackish or hypersaline waters to the deep parts of the ocean (Sen Gupta, 1999). Benthic foraminifers were considered to reflect temperature, salinity, and depth of their environment. The correlation between benthic foraminifers and climate resulted in the recognition of tropical, subtropical, boreal, and polar bioprovinces (Boltovskoy, 1976, Murray, 1991).
The connection between benthic foraminiferal distribution and salinity was used to identify normal marine, hyper- and hyposaline environments (Boltovskoy, 1976). The relationship of foraminiferal distribution and water depth is under debate (Murray, 1991,
Van der Zwaan et al., 1999), although benthic foraminifers have been widely used for paleobathymetric studies.
In addition to the large-scale investigations, it has become evident that oxygen and food supplies (organic flux) are important parameters influencing the small-scale
(e.g. within one basin) distribution of benthic foraminifers. Oxygen and organic flux distribution into the deep ocean are dependent on primary productivity in the surface waters and/or bottom water distribution. Subsequently, a variety of studies used benthic foraminiferal assemblages for paleoceanographic and paleotrophic studies (e.g.
Mackensen et at., 1990; Ishman & Domack, 1994; Schmiedl & Mackensen, 1997;
Schmiedl et al., 1997; Sen Gupta, 1999).
13 On a micro scale (e.g. at one locality) Jorissen (1995) introduced the so-called
TROX model, proposing that the benthic foraminiferal in-sediment distribution is determined by the combination of organic flux and oxygenation. The TROX model explains variations in the microhabitat depth of benthic foraminifers, that is, the sediment depth living specimens prefer under certain conditions (for discussion see chapter 2).
Antarctic foraminifers
The Antarctic plays an essential role in controlling paleoproductivity and bottom water circulation in the world’s oceans. High productivity zones at low latitudes (Keir,
1988) might cause an increase in storage of CO 2 in the deep ocean and may explain the drop in atmospheric CO2 during glacials (Samtheim & Winn, 1990). Additionally, the
Antarctic Ocean is one of the earth’s two principal sources of oceanic bottom waters
(Foster & Weiss, 1988; Foldvik & Gammelsrod, 1988). Changes in the Antarctic production of bottom waters are likely to alter global ocean circulation pattern and climate. Benthic foraminifers are abundant and important faunal constituents of deep-sea sediments and record information concerning both paleoproductivity and bottom water circulation (e.g. Herguera & Berger, 1991; Schmiedl & Mackensen, 1997, Kwiek et aL,
1999; Faul et aL, 2000) (Fig 1.6).
Surface waters in the study area are strongly affected by spring melting of sea ice, and diatom productivity is therefore very seasonal (Krebs, 1983). The coastal zones of
Antarctica are areas of unusually high rates of primary productivity during spring blooms with duration of less than two months (Kellogg & Kellogg, 1986). Spring phytoplankton blooms increase the downward flux of organic matter causing a strong seasonal signal to
14 Sca-ice ë ^Mclhvater
Eutrophic -X - ■ Oligotrophic Foraminiferal Proxies: Diversity High Low Benthic foraminiferal accumulation rates (BFAR) High Low
Dominance of Calcareous taxa Agglutinated taxa
Fig. 1.6. Simplified ecology of Antarctic benthic foraminifers. the benthos even in the deep-sea (Deuser, 1986). During the spring blooms it is possible
that the seafloor becomes temporarily eutrophic and opportunistic benthic species thrive.
During most of the time, however, primary productivity is reduced, and the organic flux
to the seafloor low. Mackensen et al. (1990, 1993, 1995) proposed that the assemblage
composition of benthic foraminifers during oligotrophic conditions is strongly influenced
by physical and chemical characteristics of the ambient water masses. The faunal
composition and spatial distribution of benthic foraminifers in the prevalent water masses
is investigated in chapter 2.
Post-burial taphonomic changes
Some of the post-burial processes that may lead from an ideal dead assemblage
(equivalent to the living assemblages) to a thanatocoenosis (dead assemblage) were
incorporated into the concept of Mackensen et al. (1990). They defined the model of a
potential fossil assemblage, which includes the disintegration of agglutinated taxa.
Agglutinated species construct their shells of foreign particles cemented together by the
foraminifer (Sen Gupta, 1999). Most agglutinated foraminifers disintegrate rapidly after
death due to the loss of cement and therefore display a strong down-core decrease in
Quaternary cores. It is evident that a detailed study of the preservation potential of
agglutinated species of the study area would aid in excluding unwanted preservation effects in the interpretation of fossil assemblages, and is carried out in chapter 2.
Mackensen et al. (1990, p. 250) mentioned that the potential fossil concept “does not consider ongoing calcite dissolution with continuous burial below accumulating
sediments”. Recent dissolution of calcareous tests is clearly active in the study area; most
16 samples yielded severely etched calcareous specimens (Appendix B, fig. B2). The potential fossil concept should, therefore, also incorporate consideration of the dissolution resistance of calcareous foraminifers as well. The dissolution resistance of calcareous foraminifers differs at the generic level (Corliss & Honjo, 1981). Partial dissolution may remove the more susceptible species and change the composition of the fossil assemblages, thereby altering the paleoecological record (Thunell & Honjo, 1981;
Hemleben et aL, 1984; Kucera et al., 1997; Goldstein et al., 1999; Henriksson &
Malmgren 1999; Murray & Alve, 1999). In Chapter 2 of this dissertation the dissolution resistance of the major benthic species is investigated in order to define robust assemblages that are likely to survive postmortem processes. Attention was given to post sampling processes, since it was noted by Schnitker et al., (1980) that calcareous microfossils can be an ephemeral constituent of a sediment sample under certain storage conditions.
Organic foraminiferal linings
Internal foraminiferal organic linings consist of a semitransparent to brown- colored series of individual chambers linked by a foramen (de Vernal et aL, 1992). The chemistry of Unings has yet to be determined, though there are indications that it may vary from species to species (Banner et al., 1973). Arenaceous species, for instance, yield linings composed of a glycoprotein complex (“tectin”, Hedley, 1963). Not all foraminifers possess preservable linings (Stancliffe, 1996), and little has been done to identify linings to the species level. In chapter 3 the composition of organic foraminiferal lining assemblages from modem and Holocene sediments from the Palmer Deep area is
17 investigated. Future studies of the chemical composition of organic linings are expected to increase our knowledge in the growing field of molecular biology, contributing to long debated issues such as generic and family relationships, classification, evolutionary derivation of major groups, bipolarity of foraminifers, and macro-/ micro-evolution.
Furthermore, it may be possible to use the chemistry of organic linings as paleoclimate proxies and for time control. The ratios (5^^C) derived from foraminiferal calcite have been frequently used as proxies of paleoproductivity or deep- water circulation (Mackensen et aL, 1993; McCorkle & Keigwin, 1994; Bickert et aL,
1999; Faul et aL, 2000; Schonfeld & Zahn, 2000). Linings are chemically resistant and provide information in instances where disintegration has removed their outer mineral shells. Foraminiferal calcite is one of the preferred sources for chronologies
(Leventer et aL, 1996; Domack et aL, in press).
The acid-insoluble organic (AIO) fraction of marine sediments is often used for
chronologies due to the paucity of biogenic carbonate in many polar areas (Licht et aL, 1998). Establishing of a chronology based on linings of a single species rather than using the AIO fraction (which contains a mixture of organic matter of different ages and origin) may therefore enhance the accuracy of the dates.
Biomineralization of benthic foraminifers
Agglutinated foraminifers have been largely ignored in paleoclimatic research in comparison to their calcareous counterparts, due to the difficulties inherent in studying their tests. Since the first major work by Hedley (1963), little has been done until recently in studying biomineralization of agglutinated foraminifers. Scanning electron microscope
18 (SEM) interfaced with an energy dispersive X-ray spectrometer (EDS) provides the micropaleontologist with a reliable and fast chemical analysis during the imaging of specimens (Commeau et al, 1985; Bertram & Cown, 1998, Allen et al.. 1999). Evidence derived from these investigations support the long-standing assumption that certain agglutinated species are able to select wall material (grains, cement) (Allen et aL, 1999).
The influence of environmental conditions on the compositions of inorganic constituents of foraminifera is unknown. Mineralization of the organic cement of iron has been proven for certain agglutinating foraminifers (Hedley, 1963; Murray, 1973; Bertram & Cowen,
1998). There is considerable interest in the biochemical cycling of iron in the world’s oceans (Johnson et aL, 1997; Wells et aL, 1995). Iron plays an important role in controlling primary productivity in the ocean under certain circumstances (e.g. de Baar et aL, 1990). Future studies of iron uptake by benthic foraminifers in relation to environmental conditions may provide valuable insights in the biochemistry of cycling of iron over time. Furthermore, iron content may be one of the factors that influence the test stability of agglutinated foraminifers. In chapter 4, the iron contents of benthic foraminifers is investigated quantitatively, with special emphasis on the relationship between iron content and resistance to postmortem disintegration (preservation potential) of agglutinated foraminifers.
One of the most established and reliable climate proxies is derived from the oxygen isotopic composition (ô^^O) of benthic and planktonic foraminifers (Shackleton
& Opdyke, 1977; Shackleton et aL, 1995; Kennett et aL, 1995; Asioli et aL, 1999; Lee &
Slowey, 1999; Shackleton, 2000). However, the utility of records for the purpose of paleothermometry is limited, since 5^*0 ratios from deep-sea foraminifera are primarily
19 determined by the global continental ice volume (Lear et aL, 2000). An independent temperature proxy that allows the extraction of the global ice budget from the deep-sea
record is therefore needed. Magnesium (Mg) is one of the main cation constituents of seawater; the Mg/Ca ratio is thought to be constant both in the water column and during the last 500 ky (Broecker & Peng, 1982), unlike the 5^*0 of seawater. Chave (1954) showed that the magnesium content of the biomineralized calcite of foraminifers was positively correlated with ambient water temperature. The main advantage of Mg paleothermometry is that it is measured on the same biotic carrier as 0^*0, thereby avoiding biological fractionation processes (vital effects) that occur when different faunal groups are used (Nürnberg, 2000). Nürnberg points out that, by combining the 5**0 with
Mg/Ca, both global continental ice volume and paleotemperatures can be determined. Mg paleothermometry of benthic and planktonic foraminifers has been recently validated in a number of time-scales and oceanographic settings (Rathbum & De Deckker, 1995;
Mitsuguchi et aL, 1996; Hastings et aL, 1998; Lea et aL, 2000). In Chapter 4 of this dissertation the results of a reconnaissance study of benthic foraminiferal Mg/Ca ratios are provided, and test the utility of this promising paieothermometer in the particular setting of the Antarctic Peninsula.
Holocene foraminifers
The results on ecology, post-burial taphonomic changes, and biomineralization of modem benthic foraminifers are used for the interpretation of Holocene assemblages. In chapter 5 of this dissertation, the benthic assemblages of ODP cores 1098 and 1099 from the Palmer Deep basins are investigated. Core JPC18 from the center of the Andvord drift
20 was collected during the NDP99/3 cruise and presumably spans the late and mid-
Holocene. In chapter 6 of this dissertation the benthic foraminiferal of NDP99/3 JPC18
are investigated. In both chapters, benthic foraminiferal accumulation rates and statistical
analysis of benthic assemblages are used as paleoceanographic and paleoclimatic proxies.
1.3. Methology (Overview)
Sample selection
Sampling of modem surface samples was conducted during the 1998 field season to the Pacific sector of the Antarctic Peninsula. Material available for this study was collected during the LMG Gould cruise LMG98-2 by the author. The sites chosen for this
study were supplementary to the long sediment cores retrieved from the study area.
Thirty-four surface samples (hereafter referred to as G19-78, fig. 1.1) were collected using a Smith-Mclntyre grab sampler. The disadvantages of this tool for micropaleontological research are that the sediment/water interface may be disturbed; the uppermost sediment layer may be removed, and short core length (> ~ 12 cm).
The tool of choice for this kind of work, a professionally built multiple corer, was not available. This systematic flaw has to be kept in mind in the interpretation of epifaunal species, which are living at the sediment/water interface. The grab samples were sub-sampled onboard into 0-0.5 cm, 0.5-1 cm, 1-2 cm, 2-3 cm etc. sections, the volume of sediment noted, and samples stored in watertight containers. The samples of the upper six centimeters were stained in a Rose Bengal alcohol solution for the recognition of living (protoplasm containing) specimens.
21 Holocene samples were taken from 4 cores. Core 1098b from Palmer Deep basin I
and 1099a/b from Palmer Deep basin I o f ODP LEG 178 were retrieved during the 1998
field season. Cores JPC18 from the Andvord drift and 28 from the Gerlache Strait were
recovered by the NDP99/3 cruise the following year.
Sample processing
Little attention has been given to the potential danger o f micro fossil damage during
storage and processing. The effect o f the processing technique used in extracting microfossil faunas has been rarely considered. One o f the few exceptions is Hodginson's
(1991) “Microfossil processing: a damage report”. It was noted earlier that storage, for
instance, could lead to the destruction of micro fossils and therefore can bias interpretations (Schnitker, et aL, 1980). Goldstein & Watkins (1999) noted that drying destroyed delicate agglutinated tests.
Sediment composition and porewater chemistry are presumably the main factors that influence the susceptibility o f microfossils to post-sampling destruction. The
following procedures and recommendations apply to sediments similar to those encountered in the study area.
The general methods used in this study are outlined below. Chapter specific methods are explained in more detail in each chapter. A standardized procedure was applied to all samples. After the samples were received, they were washed as soon as possible, but not later than 3 months. Schnitker et al. (1980) pointed out that microfossils might be “an ephemeral portion” o f the sample if the sediment is exposed to oxygen and
22 desiccation. Sediments from the study area consist of diatomaceous mud and ooze with low carbonate (1-3%) and moderate TOC content (2-3 %, Barker et al., 1999) which may contribute to post-sampling dissolution of calcareous fossils.
The samples were washed through a 63 pm sieve, using water without solvents and moderate water pressure to prevent damage to fragile species. The use of dispersants such as Calgon was avoided, since the possibility could not be excluded that this would result in the destruction of certain weakly cemented agglutinated foraminifers. The > 63 pm fractions were dried at room temperature, and the dry weight was recorded. Oven- drying procedures used by several authors (e.g. Murray & Alve, 1999) were avoided.
Approximately every 5* sample was investigated qualitatively while still wet, and counted after drying, since the disintegration of agglutinated foraminifers during drying is a possibility. The comparison did not yield any major differences, thus dry-picking was chosen for the standard technique. A few samples were kept wet and embedded in Epo^g
Resin (see chapter 4), but no additional taxa were observed.
AH foraminifers from the dried samples were identified and counted under a Wild binocular. Another storage problem should be mentioned. Preliminary observations by the author point to a possible disintegration of calcareous foraminifers even after drying.
Presumably, pyrite within the tests was oxidized and resulted in the production of sulfuric acid and dissolution of the skeletal carbonate. The general recommendation that follows from these investigations is that samples should be kept wet and processed as soon as possible and also investigated as soon as possible.
23 Processing of foraminiferal data
The benthic foraminifera were identified according to the classification scheme of
Loeblich & Tappan (1988). The identified species, taxonomic notes and their abbreviated
synonymy are listed in Appendix B.
Counts are generally given in “number of tests per cm^ of wet sediment (#/cm^
hereafter)”. The standard approach “number of tests per g of dried sediment” was not
carried out mainly because of damage concerns. Sediments from the study area are
unlithified soft muds with high water contents and can be washed without solvents and
with minimum water pressure, thereby limiting damage to delicate microfossils. The
sediments revealed only minor changes in composition, e.g. the fluctuations of the
sediment density of ODP core 1098b from Palmer Deep basin I were small.
Consequently, the numbers of tests calculated per gram and per cm^ were similar.
Two foraminiferal proxies were calculated in this study. The diversity is expressed as the number of species in a given sample. Benthic foraminiferal accumulation rates (BFAR hereafter) have been calculated as the number of dead tests per cm^ky'\ based on sedimentation rates published in Le venter et al. (1996), Domack et al. (1999), Harris et al. (1999), and Domacket al, (in press).
Statistical analysis was performed on the potential fossil data set following the methods described in Mackensen et al. (1990). Q-mode PCA was carried out using a commercially distributed statistics package (SYSTAT ™ Vm, 1998), to keep the data set comparable to previous studies from Antarctica.
24 C H A P T E R 2
MODERN FORAMINIFERS FROM THE PALMER DEEP REGION
2.1. Summary
Ecological preferences, preservation potential of agglutinated species, and dissolution resistance of calcareous species determine the faunal composition of benthic foraminifers from the Palmer Deep. Due to postmortem disintegration processes, the thanatocoenoses (dead assemblages) usually consist of few species. The comparison between the total (including weakly cemented agglutinated) and the potential fossil
(corrected by the removal of agglutinated species) assemblages shows that statistical analysis may define similar assemblages in the fossil record.
The thanatocoenoses differ considerably from the biocoenoses (living assemblages). It is proposed that this is due to a strong seasonality of benthic foraminifers in the study area. Two living assemblages from the sampling season can be defined in this study. The B. aculeata assemblage, currently present in the Palmer Deep basins, has been proven to be robust to postmortem changes, and will be used to indicate open marine conditions during the austral summer, up-welling of Circumpolar Deep Water
(CDW) and increased primary productivity in the surface waters.
25 The F. fusiformis assemblage seems to be opportunistic and thrive=s in environments that may be temporarily anoxic. These conditions seem to prevail im the
Andvord drift and Gerlache Strait, recently bathed in Weddell Sea Transitional Water
(WSTW), where the shallow water depth prevents deep-water circulation and hindering the oxygenation of the bottom waters. Despite its low dissolution resistance, F. fusiformis occurred in large numbers in Holocene sediments from Andvord drift, suggesting that strong productivity may outweigh dissolution.
Additionally, two more assemblages are proposed. It is suggested that these live during different parts of the year, since they are present only in the thanatocoenoses. The
M. arenacea assemblage occupies the shallower parts of the Palmer Deep and the adjacent Gerlache Strait to the east. Due to proximity to the coast, sea-ice persists longer than over the deep parts of the Palmer Basins. Until more information about ecolo*gical preferences of M. arenacea becomes available, it is suggested that this taxon can be used as an indicator of hypersaline conditions, which may be generated by the formation
Saline Shelf Water (SSW). Due to the excellent preservation potential of M. aremacea this assemblage is robust in Holocene sediments.
There is some indication that the T. intermedia assemblage may be adapted to low salinities, which occur during the spring melting of sea-ice. The associated speci«es S. biformis, noted for its ability to live in low salinities, has a low preservation potemtial.
The T. intermedia assemblage may therefore appear monospecific in the fossil record..
26 2.2. ûitroduction
Benthic foraminifers are widely employed as proxies in reconstructing paleoenvironments because of their wide distribution in most marine settings. Known since the Cambrian, foraminifers diversified rapidly and are present in a variety of environments, from shallow brackish or hypersaline waters to the deep parts of the ocean
(Sen Gupta, 1999). Benthic foraminiferal assemblages were considered to reflect temperature, salinity, and depth of their environment. In this chapter the composition and spatial distribution of modem benthic foraminifers from the study area is investigated.
Special emphasis is placed on postmortem processes that may influence the assemblage generation. The information derived was used for the interpretation of Holocene assemblages (chapter 5-6).
The use of Rose Bengal
The surface samples were stained in Rose Bengal alcohol solution for the recognition of cytoplasm, which is thought to indicate the presence of living specimens.
Although the use of Rose Bengal as a means of recognizing living foraminifers has been under some debate (Bernhard 1993; Jorissenet al., 1995, Bernhard, in press), it is still the method of choice for the treatment of larger samples (Wollenburg & Mackensen, 1999;
Murray & Bowser, 2000). Problems occur mostly with deep infaunal species, which may accept stain long after death due to oxygen depletion below the sulfate reduction horizon
(Jorissenet al. 1995). Abundances of stained specimens from deep in the sediment must be carefully considered.
27 Another setback that may arise is that foreign tissue from bacteria inside empty foraminifers may result in a weak pink coloration. Only tests that exhibit a bright red coloration have been counted as living in order to avoid such artifacts. Agglutinated species with cement containing iron oxides may present special problems. The iron content results in a red-brown coloration of the tests, hindering the recognition of stained protoplasm. The tests had to be broken apart in these instances. This has been done in only a couple of cases in order not to destroy the complete collection. It is therefore possible that these species are somewhat underrepresented in the biocoenoses counts.
Species presenting this problem include Haplophragmoides parkerae, Haplophragmoides canariensis, and Haplophragmoides sp. A solution to this problem is the use of Epoxy
Resin, which makes the agglutinated tests translucent without destroying the tests.
Internal organic linings can stain the foraminiferal test (Bernhard, in press), but in case of this study no stained linings were observed.
Microhabitat of benthic foraminifers
A variety of terms have been proposed to describe the vertical distribution of living benthic foraminifers in the sediment (Sen Gupta, 1999). For the purpose of this study, the classification of Corliss (1991) will be applied, since it is widely used in the literature and enables the rapid characterization of the vertical distribution pattern. The following terms apply when the conditions are ideal, that is, when oxygen and food are plentiful. If one or both of these factors are limited, benthic foraminifers change their microhabitat as outlined below.
28 The term epifauna is used for species found exclusively in the uppermost centimeter of the substrate. Taxa confined to the 0-2 cm interval are referred to as shallow infauna. An intermediate infauna dwells between 1-4 cm. Living species below four cm are labeled as deep infauna.
Two major factors are believed to control the microhabitat of benthic foraminifers. Bottom-water oxygenation may be an important factor in determining the lower vertical limit in eutrophic sediments. Although several species have been found alive in temporary states of anoxia (Bernhard, 1993; Bernhard et al., 1999), it is unlikely that the majority of foraminifers can survive permanently without oxygen. Evidence for this is the total absence of foraminifers after prolonged laboratory anoxia (Bernhard &
Reimers, 1991), and their absence in Mediterranean anoxic sediments (sapropels) (e.g.
Stachowitsch & Pearson, 1991). Benthic assemblages are confined to the uppermost sediment centimeter if oxygen is limited (Fig. 2.1), and consist of species with a deep to intermediate infaunal life style under ideal conditions {Jorissen et at., 1995). Food availability is thought to play a major role in the oligotrophic regions of the oceans.
The small quantity of food that reaches the seafloor is almost completely consumed at the sediment-water interface (Reimers et al., 1986). In this case, when food is limited, foraminifers are usually confined to the uppermost sediment centimeter and consist of epifaunal and shallow infaunal taxa (Jorissen et al., 1995). Based on these considerations, the authors proposed the TROX model to explain variations in the microhabitat depth. This simple model will be utilized to evaluate trophic conditions in the study area (Fig. 2.1).
29 oligotrophic mesotrophic eutrophic
. pxiç. -. zô h é
a œ
epifeuna
shallow-dwelling infaune
deep-dwelling infauna
Food Oxygen
Figure 2.1. Hypothetical scheme showing variation of microhabitat depth of infaunal taxa as a function of the depth of a critical Level in the sediment. Figure from Sen Gupta (1999, reproduced by courtesy of De Stigter).
30 Biocoenosis and thanatocoenosis
The definitions for biocoenosis and thanatocoenosis as used in this study are given in figure 2.2, since they differ from their usual meanings in geological research.
The biocoenosis or living assemblage in geology is a concept. Only very rarely is it possible to identify biocoenoses in the fossil record, exceptions are fossil lagerstatten
(e.g. Burgess shale), where instantaneous sedimentation processes preserved the assemblages. With the use of cytoplasm staining techniques (e.g. Rose Bengal) it is possible to recognize living specimens in modem samples, thus enabling the micropaleontologist to define natural ecological units.
The ideal thanatocoenosis or dead assemblage (Murray, 1991) is hypothetical as well, since postmortem alteration through bioturbation, disintegration of agglutinated or dissolution of calcareous foraminifers sets in immediately. The thanatocoenosis in geology is usually defined as an assemblage brought together by sedimentation processes rather than life processes. Bottom ciurents or ice rafting may export foraminiferal tests into the study area. However, the author favors the view that these processes play only a minor role in the deep-sea environment of the Palmer Deep area. The sediments that accumulated since the last deglaciation consist of very fine grained diatomaceous muds and oozes (Barker et al., 1999), which excludes the presence of strong bottom currents.
Ice rafting derived debris is a small constituent of the sediment (see chapter 5-6). It is therefore assumed that the number of tests transported by ice rafting is also small. This is supported by very rare or absent shallow water foraminifers in modem and Holocene samples.
31 I life processes, dependent on food and oxygen supply, salinity
Living assemblages (biocoenoses)
"(b) A group of organisms that live closely together and form a natural écologie unit.’
(Glossary of Geology, 1980)
I death
Ideal dead assemblages (hypothetical, equivalent to living assemblages)
I postmortem changes: transportation, bioturbation, dissolution, disintegration
Dead assemblages (thanatocoenoses)
"(b) A group of fossils that may represent the biocoenosis of an area "
(Glossary of Geology, 1980)
I artifacts during sampling, storage and processing
Artificial thanatocoenoses
Figure 2.2. Simplified relationship between biocoenoses and thanatocoenoses (based on Murray, 1991).
32 Bioturbation leads, through time averaging, to a mixed surface sediment layer with temporally mixed assemblages (Fig. 2.3). The surface layer of mixed sediment is thought to act as a low-pass filter that damps high frequency fluctuations (Martin, 1995).
It was noted by Murray (1991) that the influence of bioturbation is inversely proportional to the sedimentation rate. A typical Holocene (the last 12000 years) deep-sea sequence is about 30 cm thick. The assemblages of the last 2000 years are constantly mixed under the assumption that bioturbation effects the upper 5 cm. The modem sedimentation rates in the Palmer Deep vary from 0.13 to 0.39 cm/yr (Appendix A). Bioturbation would theoretically affect aissemblages only of the last 13-40 years. The influence of bioturbation may thus be neglected in case of the Palmer Deep environment, due to the extraordinarily high sedimentation rates. It is thus assumed that transportation and bioturbation play only a minor role in the assemblage generation, and that the thanatocoenoses in the study area can be used as a good approximation of the biocoenoses.
The last step. Heading from a thanatocoenosis to an artificial assemblage through sampling, storage, or processing artifacts has been rarely investigated. The chosen sampling tool can alterr the faunal compositions. The grab-sampler used in this study to retrieve surface samples may disturb the sediment/water interface and fail to recover the uppermost sediment layer. The tool of choice for this kind of work, a professionally built multiple-corer, was not available. This systematic flaw has to be kept in mind in the interpretation of epifaumal species, which are living at the sediment/water interface.
33 import by bottom currents, •export by bottom currents; gravity
; test production by epnfaucta shallow-dwelling Infauna
####
Figure 2.3. Sketch showing habitats of benthic foraminifers and various postmortem processes that may lead to mixed faunas. Figure from Sen Gupta (1999, reproduced by courtesy of De Stitger).
34 Desiccation o f marine samples during storage may lead to disintegration of foraminifers (Schnitker et al., 1980). Indication exists that storage artifacts are a possibility in samples from the study area (Osterman et at., submitted). The extend of storage disintegration of foraminiferal assemblages is investigated in a laboratory experiment (see Chapter 7).
Fossilization potential
Some of the processes that may lead from an ideal dead assemblage to a thanatocoenosis were incorporated into the concept of Mackensen et at. (1990). The authors defined the model of a potential fossil assemblage, which includes considering the disintegration of agglutinated taxa. Agglutinated species construct their shells of foreign particles cemented together by the foraminifer (Sen Gupta, 1999).
It is well known that most agglutinated foraminifers disintegrate rapidly after death, displaying a strong down core decrease in Quatemary cores. Possible impacts of the disintegration of agglutinated species are illustrated by the following study from literature (Fig. 2.4). A down core decrease in Foraminiferal Numbers (FN) in core PD88-
22 (hereafter PD22) from Andvord Bay was interpreted as due to increasing sedimentation rates (Domack et al., 1993). The authors used assemblages that were not corrected by removal of agglutinated species with low preservation potential.
The down core decrease is diminished if the concept of a potential fossil assemblage is applied and only agglutinated taxa are included into the data set that are known to possess a high preservation potential. It suggests that the disintegration of agglutinated species causing the decrease in FN as an alternative explanation. Moreover,
35 the ecological signal seems to have been improved, since the FN (potential fossil) shows a cyclical pattern, with high abundances at 200, 480, and 780 cm core depth. As with any other proxy, however, final proof will have to be provided by cross checking with one or more other independent proxies.
It is evident that a detailed study of the preservation potential of agglutinated species is beneficial for excluding unwanted preservation effects in the interpretation of fossil assemblages.
300 PD88-22 AndvortBay (N=ii) 250
200 Potential fossil
g 150 Uncorrected
100
50
0 0 100 200 300 400 500600 700 800 900 Core depth (cm)
Figure 2.4. Foraminiferal niunbers (FN) from core PD22 of Andvord Bay. Data are from Domack et al. (1993).
36 Mackensen et al. (1990, p. 250) mentioned that the potential fossil concept “does not consider ongoing calcite dissolution with continuous burial below accumulating sediments”. Dissolution of calcareous tests is clearly active in the study area as indicated by severely etched calcareous specimens in most modem samples (Appendix B, fig. B2).
In some cases, even live individuals with signs of partial dissolution were observed. The potential fossil concept should therefore incorporate a reflection on the dissolution resistance of calcareous foraminifers as well. Differential dissolution resistance of calcareous foraminifers was previously reported by several authors (summary in Sen
Gupta, 1999).
Statistical treatment of foraminiferal assemblages
Quantitative analytical methods are widely used in foraminiferal research to enhance the desired ecological signal, suppress noise, and simplify a complicated data set
(Sen Gupta, 1999). Principal Components Analysis (PCA hereafter) is the simplest of the so-called eigenvector analytical techniques. This method will ideally produce as many new principal components (PC hereafter) as there were original entities in the data, which would explain 100% o f the variance. It is usually not desirable to create a large number of principal components, since it would interfere with the goal of simplification. Most studies rely on 3-5 principal components.
Q-mode PCA was carried out using a commercially distributed statistics package
(SYSTAT ™ vm, 1998) to keep the data set comparable to previous studies from
Antarctica. The dead and living assemblages combined are commonly used for statistical analyses (e.g. Ishman & Domack, 1995). However, Murray (1991) noted that the living 37 and dead assemblages may differ considerably due to seasonality of the biocoenoses and postmortem alterations. A separate statistical treatment of biocoenoses and thanatocoenoses may thus allow recognition of seasonal assemblages, whereas the use of total assemblages would result in loss of information in this matter.
In order to minimize preservation artifacts due to rapid disintegration of agglutinated tests, the concept of a potential fossil assemblage (Mackensen, 1990;
Mackensen et al., 1995) was applied. Harlofif & Mackensen (1997) define this concept as
“the best available prediction of the assemblage which remain fossilized firom a dead assemblage on Quatemary time scales”.
2.3. Objectives e Biocoenoses and thanatocoenoses of the surface samples and their spatial distribution
win be defined by the use of Rose BengaL The identified preferred microhabitat
depth of the dominant taxa wfll be used to evaluate trophic conditions in the study
area.
The vertical distribution of dead tests in the surface samples wfll be examined to
evaluate the fossilization potential of foraminifers. Exponential decreases down core,
or high living/dead ratios may indicate a low preservation potential of a species, and
longer sediment cores wfll be used to test the derived conclusions.
38 A potential fossil data set will be established, consisting of species with sufficient
fossilization potential The comparison between the total assemblages (incL weakly
cemented agglutinated) and the potential fossil (corrected by the removal of
agglutinated species) assemblages wiH be used to evaluate whether statistical analysis
defines similar assemblages in the fossil record.
2.4. Material & Methods
Field collection
Material available for this study was collected during the LMG Gould cruise
LMG98-2 by the author. Thirty-four grab samples (hereafter referred to as G19-78,
appendix A) were collected using a Smith-Mclntyre grab sampler. The grab samples
were sub-sampled onboard into 0-0.5 cm, 0.5-1 cm, 1-2 cm, 2-3 cm etc. sections, the
volume of sediment noted, and samples stored in watertight containers. The samples of
the upper six centimeters were preserved in alcohol solution and stained with Rose
Bengal for the recognition of “living” (cytoplasm-containing) specimens.
Three kasten cores (hereafter referred to as KC17, KC26, and KC27, fig. 2.5) were
collected during the L.M. Gould cruise LMG98-2 using a stainless steel box core, three m
long and 10 cm by 10 cm wide. Each kasten core was sub-sampled onboard in five cm
intervals, the volume of sediment noted, and samples stored in watertight containers. The
top three samples of each kasten core were stained in Rose BengaL Two gravity cores
(hereafter referred to as GC14, GC15, fig 2.5) were retrieved during the LM Gould cruise
LMG98-2 using a 500 pound weight attached to an 11.4 cm diameter PVC pipe of 3 m
39 Anvers Island Andvord JPC 8
GC15
GC14 Palmer Deep < 2
o
64°30'W 64°00'W 63°30'W 63°00'W
Figure 2.5. Map of the study area showing surface sample locations, Palmer Deep transects PDl-3, Andvord drift transects ADI and positions of grab sample and long sediment core stations. length. The cores were not opened onboard. Thus, the cores could not be sampled onboard and the top samples were not stained. The gravity cores were sub- sampled in five centimeter intervals five months after the cruise.
Jumbo piston core NBP/99-3 JPC18 (hereafter referred to as JPC18, fig 2.5) was available for this study from the Andvord drift. JPC 18 was incorporated in this Chapter because no longer core was retrieved from that area during the LMG98/2 cruise. JPC18 was sampled in five centimeter intervals one year after recovery. Finally, core PB92-05
(hereafter referred to as PD05) from the sill between Palmer Deep basins U and HI was investigated in order to evaluate the impacts of post-sampling loss of foraminiferal tests in other cores named above. PD05 was sampled in five centimeter intervals shortly after retrieval, and samples were stored for almost seven years before processing by the author.
Foraminiferal data acquisition and processing
The samples were washed through a 63 pm sieve, using water without solvents and moderate water pressure to prevent damage to fragile species. The > 63 pm fractions were dried at room temperature, and the dry weight noted. Subsequently, all foraminifers were identified and counted under a Wild binocular microscope. In case of the Rose
Bengal treated samples, stained (referred to below as living) and empty tests (referred to below as dead) were counted separately.
Large stick-like agglutinated species of the family Astrorhizidae were often found broken into two or more pieces despite the gentle washing methods used. In these cases three pieces were counted as one specimen, in order to estimate the original number of tests. Species subjected to this method include Reophax dentaliniformis, Reophax
41 subdentaliniformis, and Saccorhiza sp. Some calcareous tests were found equally broken in two pieces, and were counted accordingly as one specimen. Species exposed to this method include the fragile and elongate Bolivina pseudopunctata and Fursenkoina earlandi.
A special phenomenon was present in one of the most abundant species, Bulimina aculeata. In some cases only the ultimate (last added to the test) chamber was found in the samples. Apparently, this part of the test has the highest resistance towards postmortem destruction in this particular species. Therefore, the ultimate chamber of B. aculeata has been counted as one specimen, when encountered without the rest of the test.
The standing stock, defined as the number of living tests per cm^yr'^ was calculated. One shortcoming of this approach was that samples from one season only were available. Thus the calculated standing stock may underestimate the actual annual production rate. However, since the food supply during most of the other seasons is restricted due to sea-ice cover, it is reasonable to assume that the bulk of the benthic production takes place during the austral summer.
Benthic foraminiferal accumulation rates (BFAR hereafter) have been calculated as the number of dead tests per cm^yr'* based on sedimentation rates published in
Leventer et al. (1996), Domack et al. (1999), and Harris et al. (1999). This was carried out for the dead (not corrected) and dead (potential fossil = corrected by removal of agglutinated species with low preservation potential) assemblages as well.
42 A preservation index in this study was defined as the standing stock / BFAR ratio.
The goal of this approach was to quantify the disintegration resistance of agglutinated
and dissolution resistance of calcareous foraminifers. Diversities were expressed as
species per sample. The derived diversity values were used for further characterization of
the assemblages.
Statistical analysis was performed on two data sets. The first includes the
biocoenoses (total) and thanatocoenoses (total) which were not corrected by removal of
agglutinated species. The second set was calculated by removing all agglutinated
foraminifers except M. arenacea and Trochammina intermedia from the data. M.
arenacea is known to be resistant to early diagenetic processes (Mackensen et al., 1993).
Nothing is known from literature about the preservation potential of T. intermedia, but
since this species is present throughout cores spanning most of the Holocene in the study
area (see chapter 5-6), it was incorporated into the potfossil data-set. In order to evaluate
the loss of information due to the removal of agglutinated species, both the biocoenoses
and thanatocoenoses have been determined for total and potential fossil assemblages.
Two assemblages were investigated for their spatial distribution. The biocoenoses
(total) used were not corrected by removal of agglutinated species. It is reasonable to
assume that disintegration processes did not have an impact on the composition of the
living assemblages. The thanatocoenoses (potential fossil), corrected by the removal of
agglutinated species were also investigated. It seems possible that the disintegration of
agglutinated species had already altered the faunal composition. Furthermore, the
potential fossil assemblages most likely represent the remaining species present in
Holocene material.
43 Standing stock number of living tests cm^yr'^
BFAR number of dead tests cm^yr'^
Preservation Index Standing stock x 100 BFAR
Diversity Number of species / sample
Biocoenoses (total) not corrected by removal of agglutinated species
Biocoenoses (potential fossil) corrected by removal of agglutinated species
Thanatocoenoses (total) not corrected by removal of agglutinated species
Thanatocoenoses (potential fossil) = corrected by removal of agglutinated species
Figure 2.6. Overview of the foraminiferal parameters utilized in this study: Standing stock, BFAR, Preservation index. Diversity, biocoenoses and thanatocoenoses.
44 2.3. Results
Standing stock. BFAR. and diversity
The standing stock varies between 0 (Andvord drift) and 54 living specimens per cm^yr'^ (average 12.2) (Appendix A). The highest values were observed in Palmer Deep basins I and H, exceeding 30 living specimens per cm^yr'\ Despite these high abundances, the standing stocks display no strong trend with increasing water depth (Fig.
2.7).
The benthic foraminiferal accumulation rates (BFAR) vary between 0.4 (Andvord drift) and 10.9 (Palmer Deep basin I) tests per cm^yr'^ (average 4.1). Notable is a slight increase of BFAR (total) with increasing water depth. A similar trend was present in
BFAR (potential fossil), which were corrected by removal of agglutinated species with low preservation potential. The highest value occurred at one station in the Palmer Deep basin (8.5 tests per cm^yr'^), the lowest in the Andvord drift (0.3 tests per cm^yr**).
Between 0 (Andvord drift) and 19 species (Palmer Deep basin DI) were encountered in the biocoenoses, with no apparent water depth trend. Average diversity of the biocoenoses was 8.7. The thanatocoenoses exhibited more diversity, varying between
7 (Andvord drift) and 23 (Palmer Deep basin DI). The average was 11.8.
45 Standing stock (N = 37) 40 - 35 - 30 - \ 2 5 - S 20 - i 15 -
10 -
200 400 600 800 1000 1200 1400
BFAR (N=37) # total 10 - O potfossil
S É
• #
200 400 600 800 1000 1200 1400
Diversity (N =36) Biocoenoses o Thanatocoenoses
20 -
CD
• #
200 400 600 800 1000 1200 1400 Water depth (mbsL)
Figure 2.7. Standing stock (# of living specimens/cm^yr'\ top), benthic foraminiferal accumulation rates (BFAR, bottom), and diversity (# of species) of foraminiferal assemblages from the surface samples. Lines are second order polynomial trend lines.
46 Vertical distribution of living (Rose Bengal stained) foraminifers
Figures 2.8-2.11 show the vertical distribution of the most abundant species along three transects in the Palmer Deep basins and one in the Andvord drift (at the outlet of the
Andvord Bay). The species counts for each station are listed in Appendix A.
hi the Palmer Deep basins, B. aculeata, F. earlandi and B. pseudopunctata show a consistent pattern of peak abundances between 0.5 - 1 cm below the sediment surface.
One station (G33, fig. 2.10) however depicts the highest abundances of F. earlandi and
B. pseudopunctata at the very top (0 - 0.5 cm). In the Andvord drift, F. fusiformis, B. pseudopunctata, and T. intermedia show peak abundances between 0.5 - 1 cm (Fig. 2.11).
Below two cm, the number of stained specimens generally drops to low numbers.
Two stations from the Palmer Deep basins (G52, fig. 2.8; G34, fig. 2.10) show peaks of
B. pseudopunctata at 2 cm. A limited number of stained M. arenacea tests found in the
Andvord drift show maximum abundances in the upper two cm (Fig. 2.11). Stained specimens of M. arenacea were rare in the Palmer Deep basins.
Abundant agglutinated species found in the uppermost 0.5 cm include the
Reophax subdentaliniformis, Haplophragmoides parkerae, and Portatrochammina eltaninae from the Palmer Deep basins. No calcareous species with peaks in the uppermost 0.5 cm were recovered from this region. In the Andvord drift,
Spiroplectammina biformis is present in place of H. parkerae. Only one station (079, fig.
2.12) from Paradise Harbor yielded calcareous species (Globocassidulina biora and
Cassidulinoides parkerianus) showing maximum abundances in the upper 0.5 cm.
47 G53 0 Specimens 6 0 6 4 0 4 (300mbsl) 0 -I 4 - J
CN = 7) 1 Live Liv( Dead
Dead
K earlandl M. arenacea H. parkerae R. subdentaliniformis
G52 8 0 4 (650 mbsl) 0 J _L
I (N = 7) Live Live Dead
Dead Dead
n earlandl B. pseudopct. B. aculeata M. arenacea
G51 4 0 2 (959 mbsl) 0 J i •Live Live Dead (N = 7) Live Dead
Dead
B. aculeata earlandl H. parkeraeE
Figure 2.8. Palmer Deep Transect I, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. Note the transition from F. earlandi dominated to B. aculeata dominated assemblages and the peaks of F. earlandi "Live" between 0.5 und 1 cm core depth.
48 G54 0 Specimens 10 0 4 0 (270 mbsl)o
1 g-Dcad Dead (N = 7) 2 Dead Live
-( I
S 5 E earlandi H. parkerae M. arenacea B. pseudopct. G48 10 0 8 (1050 mbsl) 0 •Live Live
Dead
Dead
4 4 -I
B. pseudopct B. aculeata II. parkerae P. eltcninae G21 0 30 0 6 0 4 (950 mbsl)o J -i •Live Live
(N = 7) Dead Dead ( I
Dead -#-6 B. pseudopct. B. aculeata H. parkerae P. eltaninae
Figure 2.9. Palmer Deep Transect 2, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. The most abundant species F. earlandi / B. pseudopunctata of each station are rare in the dead assemblages, whereas B. aculeata shows a reverse phenomenon.
49 G31 0 Specimens 6 0 (400 mbsl) 0 ^ "— *■
” I '-Dead (N = 7) Dead
Dead
A/, arenacea H. parkerae F. earlandi B. pseudopct
G33 0 8 0 (440 mbsl) 0
(N = 7) Dead Dead
Vf. arenacea B. pseudopct F. earlandl B. aculeata
G34 0 6 10 0 (745 mbsl) Dead I (N = 7) Live 2
3
4 Dead 5 B. pseudopunct B. aculeata P. eltaninae M. arenacea
Figure 2.10. Palmer Deep Transect 3, showing vertical distribution of he most abundant species (per cm^). The species are ordered according to their abundances, with the most abundant to the left. In station G33 B. pseudopunctata and F. earlandi show peak abundances at the very top.
50 G65 0 Specimens 6 4 0 2 (358 mbsl) o 4_8_:--- 1__I__I J _L Dead Dead Live
Live Dead
4 I
M. arenacea R fusiformis T. intermedia G66 0 (400 mbsl) 0
(N = 7) 1
Dead
Dead
E fusiformis M. arenacea T. intermedia P. eltaninae G67 0 4 0 2 0 (430 mbsl) 0
(N = 7)
Dead Dead 4 O—Dead
Dead
S. biformis M. arenacea T. intermedia R. subdentaliniformis
Figure 2.11. Audvord drift transect, showing vertical distribution of the most abundant species (per cm^). The species are ordered according to their abundances, with the most abtmdant to the left. "Live" F. fusiformis and B. pseudopunctata are abundant at the uppermost centimeter, but diminish down core.
51 G79 Specimens 12 10 0.0 1.2 0.0 1.2 (256 mbsl) o -1 4 _ •Live Liv. Live, Dead Dead (N = 7) Dead
5 3 H p-Dead <
R. subdentalinifms. \f. arenacea G biora C. parkerianus
G21 0.0 1.2 G37 0 G67 0 2 (950 mbsl) (1270 mbsl) (430 mbsl) Live Dead Dead Live Dead (N = 7) Live (N = 7)
iridea P. bulloides H. canariensis
Figure 2.12. Vertical distribution of the most abundant foraminifers in G79 (Top), and of N. iridea, P. bulloides, and H. canariensis in G21, G37, and G67, respectively (per cm^). Note that "Live" G. biora and C. parkerianus are most abundant at the sediment surface and decrease exponentially down core.
52 Few samples yielded additional species in moderate numbers (Fig. 2.12).
Nonionella iridea was found in the Palmer Deep basin I (G21) with peak abundances from 0.5 - 1 cm. Pullenia bulloides occurs slightly deeper in the sediment in Palmer Deep basin HI (G37). The agglutinated species Haplophragmoides canariensis seems to thrive at the sediment surface in the Andvord drift (G67, fig. 2.11).
Vertical distribution of dead foraminifers
The vertical distribution of the most abundant species in the surface samples is shown in figures 2.8-2.11. The agglutinated assemblages of the upper two cm of the surface samples are diverse and abundant. However, from peak abundances around one cm, most agglutinated species diminish to near zero down core. The only agglutinated species not showing this trend are M. arenacea and T. intermedia. Samples of the Palmer
Deep transect 3 (Fig. 2.10) depicts increasing numbers of M. arenacea with sediment depth. The same is true for T. intermedia in the Andvord drift transect (Fig. 2.11).
The calcareous foraminifers show two major trends. In the Palmer Deep basins, the thin walled and fragile species B. pseudopunctata and F. fusiformis occur in variable numbers. In the Andvord drift both disappear within a few centimeters (Fig. 2.11). In contrast, B. aculeata generally increases in abundance with increasing sediment depth.
Few stations yielded sufficient numbers of other calcareous species. N. iridea and P. bulloides also seem to decrease with increasing sediment depth (Fig. 2.12).
53 Q-mode Principal Component Analysis (PCA)
Three live and three dead benthic assemblages are defined in this study by Q- mode principal component analysis (PCA). The assemblages are addressed by their most important species.
Biocoenoses (total)
The 3 Principal Component (PC) model explains 72.1 % of the variance within the data (Table 2.1). F. fusiformis Live PCI accounts for 30.59 % of the total variance of the biocoenoses. High loadings (> 0.6) are found exclusively in Flandres Bay and
Andvord drift in water depths ranging from 222 to 550 m (Table 2.2, fig. 2.13). In addition to F. fusiformis this assemblage contains R. subdentaliniformis as an associated species.
B. pseudopunctata Live PC2 explains 22.39 % of the total variance of the biocoenoses. High loadings occur solely in the Palmer Deep basins in a depth range of
745 to 1340 mbsl. Other important species include B. aculeata, P. bulloides, and the associated P. eltaninae.
F. earlandi Live PC3 covers 19.08 % of the total variance of the biocoenoses. It shows a somewhat patchy distribution in the shallower areas (270 to 960 mbsl) surrounding the Palmer Deep basins. This assemblage includes B. pseudopunctata and R. subdentaliniformis as dominant species.
54 Biocoenoses Total Potential fossil
S pecies PCI PC2 PC3 PCI PC2 PC3
Adercotryma glomerata -0.29 -0.43 0 3 6 Animobaculiles agglitinans ------Astrononion echolsi -0.35 -0.40 0.06 031 0 3 7 0 3 3 Bolivina pseudopunctata 0.55 339 235 1 0.47 0.66 3.77 Bulimina aculeata -0.46 2.03 -I.IO 0.40 232 0.03 Cassidulinoides parkerianus -032 -0.49 0.15 03 6 031 0 3 1
Cibicides lobatulus ------Cibrostonioides sp. -039 -0.44 -0.18 ---
Cibrostomoides subglobosum ------Fursenkoina earlandi -0.60 -1.13 3.49 1 -0.71 -2.14 1.44 Fursenkoina fusiformis 1 436 -032 0.45 1 3.94 0.10 0.46 Globocassidulina biora -037 -0.49 0.19 0 3 0 033 0 3 0 Globocassidulina crassa rossensis -030 -0.49 0.09 0.14 0 3 7 0 3 5 Haplophragmoides canariensis -0.42 -0.13 0 3 0 - -- Haplophragmoides gutrifera -0.39 -0.46 0.19 - -- Haplophragmoides parkerea -034 0.15 0 3 8 - - - Haplophragmoides pilufera ------Haplophragmoides sp. ------Miliammina arenacea 0.69 -0.44 0.20 0.66 0 3 0 031 Hodosaria spp. - - - 0 3 0 0.22 0 3 4 Nonionella bradii -034 0.47 0.20 0.20 0.22 0 3 6 Nonionella iridea -031 0.47 0.20 0.26 0.22 0 3 6 Portatrochammina challengeri -030 0.46 0.24 --- Portatrochammina eltaninae 0.07 0.92 -1.00 -- - Pullenia bulloides -0.45 1.67 0.98 0.43 2.40 0.19
Pullenia subcarinata -- - 0.33 0.16 0 3 4 Reophax dentalinifomiis -039 0.03 0.21 - -- Reophax subdentaliniformis 1 0.86 0.06 136 1 - -- Reophax sp. ------Saccamina sp. ------Saccorhiza ramosa ------Spiroplectanmiina biformis -0.23 0.45 0.24 - -- Textularia spp. -0.29 0.47 0.17 --- Trifarina angulosa ------Trochammina intermedia -0.20 0.30 0 3 0 0.13 0.06 0.28 Trochammina sp. I ------Trochammina sp. II ------
variance explained (%) 30.6 22.4 19.1 32.4 17.2 31.0
Table 2.1. Varimax Principal Component Scores of living benthic foraminiferal Q-mode assemblages from the study area. Dominant and associated species (scores > 0.8) are outlined. 55 Biocoenoses Total Potential fossil
Station PCI PC2 PC3 PCI PC2 PC3
Palmer Deep basin III G22 -0.05 1 0.86 -0.11 -0.06 1 0.80 0.45 Palmer Deep basin 1 G31 -0.04 0.14 0.92 -0.09 -058 0.77
Palmer Deep basin I G33 0.01 0.51 0.81 - 0 .0 2 -0.07 0.96 Palmer Deep basin I G34 0.13 1 0.68 0.60 0.09 0.12 0.96 Palmer Deep basin II G35 -- - - — Palmer Deep basin 11 G37 0.01 0.91 0.16 0.65 0.68 1
Palmer Deep basin 11 G38 - — - - Bandres Bay G44 0^1 0.44 0-51 1 0.19 0.91 Bandres Bay G45 -- Bandres Bay G46 0.96 -0.04 0.06 0.99 1 -0.03 -0.01 Palmer Deep basin 1 G48 0.01 0.40 0.15 0.17 0.27 0.86 1 Palmer Deep basin 11 G49 -0.04 0.76 0.00 -0.06 1 0.73 0.40
Palmer Deep basin 1 G51 0.07 0.46 0.88 - 0.01 -0.11 0.95 Palmer Deep basin 1 G52 -0.08 -0.01 0.88 -0.13 -0.45 0.61 Palmer Deep basin I G53 -0.05 -0.09 0.86 -0.15 -0.45 050 Palmer Deep basin 1 G54 -0.12 -0.22 0.78 -0.17 -052 058 Bismark Strait G58 0.13 0.68 050 0.13 0.13 0.91 Andvord drift G62 0.96 -0.10 -0.08 0.98 -0.03 -0.09 Andvord drift G64 0.98 -0.05 -0.01 0.99 -0.03 -0.01 Andvord drift G65 0.96 0.14 0.11 0.96 0.01 0.23 Andvord drift G66 0.95 -0.10 -0.10 0.97 -0.03 -0.10 Andvord drift G67 0.69 0.01 -0.09 0.95 -0.03 0.00 Andvord drift G68 0.20 0.08 0.06 0.17 -0.04 0.12 Andvord drift G69 0.96 0.01 -0.06 0.99 -0.02 0.02 Andvord drift G71 0.97 -0.05 -0.05 0.99 -0.02 -0.03 Andvord drift G72 0.96 -0.04 -0.05 0.99 -0.02 0.00 Gerlache Strait G76 0.62 0.14 053 0.89 0.06 0.41 Paradise Harbor G77 0.84 0.05 053 0.88 -0.10 0.19 Paradise Harbor G78 0.94 -0.03 -0.03 0.96 -0.01 0.00 Paradise Harbor G79 0.19 -0.02 059 0.09 -0.19 0.17 1
Palmer Deep basin 1 KOI -0.13 0.64 -054 - 0.11 0.78 0.12
Palmer Deep basin 111 K17 -0.10 0.71 -0.32 - 0.12 0.89 0.19 Palmer Deep basin 111 K26 0.08 0.78 0.42 0.09 0.29 0.91 Palmer Deep basin H K27 0.01 0.93 0.12 -0.03 0.76 0.61
Table 2.2. Varimax Principal Component Loadings of living benthic foraminiferal Q- mode assemblages from the study area. The highest loading for each station is outlined.
56 Q-mode Faunas
Anvers Island
Palm er
q:. p., earlandi ~~^É7psSudopuwictata 7 ' ,. (PC3) (PC3)
2—S blJ
6 4 “3 0 ’W 6 4 ‘>00’\V 6 3 °3 0 '\V 6 3 ° 0 0 'W
Q-mode Faunas T intermedia J A Thanatocoenoses (PC31 (potential fossil) Anvers Island
Palm er D eep
n M. arenacea (PCI) B. acideatcc
° 3 0 'W 6 4 "0 0 '\V 6 3 -3 0 'W 6 3 ° 0 0 ’\V
Figure 2.13. Spatial distribution of PCA assemblages in the study area. Top; Biocoenoses. Bottom: Thanatocoenoses (potential fossil). Note that the B. acideata / B. pseudopuncta assemblages occupy the Palmer Deep basins and that the Fursenkoina spp. live assemblages are replaced by the M. arenacea dead assemblage. T. intermedia dead (PC3) is dominant in the Andvord drift.
57 Biocoenoses (potential fossil
Though corrected by the removal of agglutinated species with low preservation
potential, the assemblages of the biocoenoses (potential fossil) closely resemble those of
the biocoenoses in composition (Table 2.1) and spatial extent (Table 2.2).
F. fusiformis liv e PCI (potential fossil) assemblage accounts for 32.4 % of the
variance and has only one dominant species. It resembles closely F. fusiformis Live PCI.
B. aculeata Live PC2 (potential fossil) includes 17.2 % of the total variance and can be regarded as the equivalent of B. pseudopunctata Live PC2, though B. pseudopunctata has much lower loadings in the former (0.66 vs. 3.29). B. pseudopunctata Live PC3 (potential fossil) consists of B. pseudopunctata and F. earlandi as dominant species. It explains 31
% of the total variance within the data and is similar to the F. earlandi Live PC3.
Thanatocoenoses (total)
The 3 PC model accounts for 87.6 % of the total variance within the data (Table
2.3). M. arenacea Dead PCI explains 30.7 % of the total variance of the thanatocoenoses.
In addition to M. arenacea, this assemblage contains F. earlandi as an associated species.
This assemblage has no equivalent in the biocoenoses.
Dead PC2 is dominated by B. aculeata and B. pseudopunctata, including P. eltaninae as an associated species. It explains 35.6 % of the total variance and resembles
B. pseudopunctata Live PC2, except for lower loadings of B. pseudopunctata (1.82 vs.
3.29), and P. bulloides (0.05 vs. 1.67). T. intermedia Dead PC3 accounts for 21.3 % of
58 the total variance. Other important species include the dominant S. biformis and the associated species F. fusiformis, M. arenacea and P. eltaninae. This assemblage has no direct equivalent in the biocoenoses.
Thanatocoenoses (potential fossil)
The 3 PC model accounts for 87.6 % of the total variance within the data. Though corrected by the removal of agglutinated species with low preservation potential, the potential fossil assemblages closely resemble the uncorrected in composition (Table 2.3) and spatial extend (Table 2.4). M. arenacea Dead PCI (potential fossil) is dominated by
M. arenacea and accounts for 34.8 % of the total variance within the thanatocoenoses
(potential fossil). It can be regarded as the equivalent of the M. arenacea Dead PCI assemblage. High loadings are found to the north of the Palmer Deep basins (Fig. 2.13).
B. aculeata PC2 Dead (potential fossil) is the equivalent of the B. aculeata Dead PC2 assemblage, explaining 38.4 % of the total variance. The Palmer Deep basins are uniformly occupied with this assemblage (Fig.2.13). T. intermedia PC3 Dead (potential fossil) assemblage includes 19.9 % of the total variance, and can be regarded as the equivalent of the T. intermedia Dead PC3 assemblage. Associated species are F. fusiformis and M. arenacea. T. intermedia Dead PC3 (potential fossil) is dominant in the
Andvord drift.
59 Thanatocoenoses Total Potential fossil
Species PCI PC2 PCS PCI PC2 PCS
Adercotryma glomerata .0.24 4)31 4). 17 Ammobaculites agglitinans -o.n 4)31 4)38 - - - Astrononion echolsi 0.06 4)32 4)31 4)06 4)32 4)48 Bolivina pseudopunctata 0.05 1.82 -0.43 4).18 1.13 4)31 Bulimina aculeata -0J.4 538 4)36 4)34 3.74 4)36 Cassidulinoides parkerianus -0.13 4)33 4)32 4)31 4)39 4)38 Cibicides lobatulus -0.12 4)33 4)38 4)30 4)39 4)37 Cibrostomoides sp. -O .n 4)31 4)37 -- - Cibrostomoides subglobosum -0.144)32 4)39 --- Fursenkoina earlandi 1 0.98 4).19 -1.06 0.70 4)32 -1.10 Fursenkoina fusiformis -0.55 4)31 1.74 1 4).71 4)38 1.64 1 Globocassidulina biora -0.16 4)32 4)32 4)32 4)38 4)32 Globocassidulina crassa rossensis -0.164)31 4).19 4).18 -039 4)36 Haplophragmoides canariensis -0.16 4)34 4)37 - - - Haplophragmoides guttifera -0.16 4)31 4)38 - -- Haplophragmoides parkerea 035 036 4)64 - - - Haplophragmoides pilufera 4). 15 4)31 4)39 - - - Haplophragmoides sp. -O .n 4)30 4)37 - -- Miliammina arenacea 1 5.66 ! 0.10 133 1 1 3.80 0.05 108 1 Neogloboquadrina pachyderma ■O.IZ 4)31 4).41 4)19 4)31 -0.39 Hodosaria spp. -0.15 4)32 4)38 -0.22 -039 4)37 Nonionella bradii -0.154)33 4)35 4)30 -039 -036 Nonionella iridea -O.n 4)30 4)35 4)33 -038 4)34 Portatrochammina challengeri 4).29 4)31 0.02 - - - Portatrochammina eltaninae 4)68 1 131 j 1.28 1 --- Pullenia bulloides -0.22 0.05 4)34 4)37 4).ll 4)32 Pullenia subcarinata -0.15 4)32 4)38 4)32 4)39 4)37 Reophax dentaliniformis 0.14 4)35 4)31 -- - Reophax subdentaliniformis 039 4)34 039 -- - Reophax sp. 4).12 4)32 4).40 --- Saccamina sp. 4).14 4)33 4)39 --- Saccorhiza ramosa 4).10 4)32 4)42 --- Spiroplectammina biformis -134 4)33 1 3.73 1 -- - Textularia spp. -0.26 4)39 0.35 -- - Trifarina angulosa 4).ll 4)32 4)40 4).19 4)39 4)38 Trochammina intermedia 4)38 4).09| 3.21 1 4).9S -0.09 3-20 1 Trochammina sp. I 4).I5 4)30 4)38 - - - Trochammina sp. U 4).I5 4)32 4)38 - - -
variance explained (%) 30.7 35.6 21.3 34.8 38.4 19.9
Table 2.3. Varimax Principal Component Scores of benthic foraminiferal Q-mode assemblages from the study area. Dominant and associated species (scores > 0.8) are outlined. Note that the original assemblages are traceable in the potfossil data set, even though the agglutinated taxa with low preservation potential have been removed. 60 Thanotocoenoses Total Potential fossil
Station PCI PC2 PC3 PCI PC2 PC3
Palmer Deep basin I GI9 0.03 1.00 0.01 0.00 1.00 0.00 Palmer Deep basin I G20 0 3 4 0.88 0.10 030 0.92 0.12 Palmer Deep basin II G21 0.07 0.99 0.00 0.04 1.00 41.01 Palmer Deep basin III G22 4).05 0.98 0.00 41.05 0.99 41.07 Palmer Deep basin I G31 0.93 0.08 038 0.93 0.05 035 Palmer Deep basin 1 G33 0.91 031 0.23 0.93 0.29 033 Palmer Deep basin I G34 0.09 0.97 41.06 0.05 0.99 41.07 Palmer Deep basin II G35 0.01 0.97 0.00 41.01 0.98 41.03 Palmer Deep basin II G37 0.04 0.96 41.05 0.00 1.00 41.05 Palmer Deep basin II G38 -0.02 0.98 0.00 41.04 0.99 41.07 Handres Bay G44 0.92 0.06 034 0.90 0.05 0.41 Flandres Bay G45 0.93 0.02 031 0.92 0.02 036 Flandres Bay G46 0.93 0.04 032 0.93 0.01 033 Palmer Deep basin I G48 41.04 0.75 0.08 41.07 0.99 0.07 Palmer Deep basin II G49 41.08 0.96 0.04 41.07 0.99 41.07 Palmer Deep basin 1 G51 OJI 0.93 41.03 0.28 0.95 41.04 Palmer Deep basin I G52 0.60 0.76 0.05 0.60 0.78 0.05 Palmer Deep basin I G53 0.86 0.07 0.12 0.87 0.00 0.13 Palmer Deep basin I G54 0.89 0.04 0.18 0.91 41.02 0.18 Bismark Strait GS8 0.95 0.01 036 0.95 0.01 0.29 Andvord drift G62 0J8 0.00 0.85 0.35 41.02 0.93 Andvord drift G64 0.41 41.02 0.86 0.44 41.02 0.88 Andvord drift G65 0.84 0.03 032 1 0.85 0.01 032 Andvord drift G66 0.69 0.03 0.63 0.65 0.00 0.75 Andvord drift G67 0.23 0.00 0.91 0.49 41.01 0.81 Andvord drift G68 0.28 0.01 0.90 032 41.01 0.78 Andvord drift G69 1 0.76 0.02 0.61 1 0.87 0.00 0.49 Andvord drift G71 0.46 41.03 0.73 0.65 41.02 0.69 Andvord drift G72 0.33 41.03 0.92 0.43 41.02 0.89 Gerlache Strait G76 1 0.82 41.02 0.34 0.92 0.01 036 Paradise Harbor G77 0.43 0.03 0.83 0.67 41.04 0.66 Paradise Harbor G78 0.22 0.01 0.86 0.33 41.05 0.78 Paradise Harbor G79 1 0.79 41.03 0.33 1 0.93 0.00 034 Palmer Deep basin I KO 1 0.06 0.77 033 0.18 0.89 0.24 Palmer Deep basin III K17 41.01 0.93 41.07 41.08 034 41.01 Palmer Deep basin III K26 0.00 035 41.09 41.06 0.93 41.08 Palmer Deep basin II K27 41.03 0.93 41.07 41.06 0.97 41.07
Table 2.4. Varimax Principal Component Loadings of benthic foraminiferal Q-mode assemblages from the Palmer Deep region. The highest loading for each station is outlined. 61 Long sediment cores
The vertical distributions of the most abundant species in longer sediment cores
from the study area are shown in figures 2.14-2.17, and listed in Appendix D. The study
of the longer cores in context of modem samples has been necessary since the grab-
sampler used could retrieve only the uppermost 10-20 cm of the seafloor. Disintegration processes may proceed well below 20 cm.
Agglutinated foraminifers
P. eltaninae drops to low numbers below 0.25 m in core GC15 Palmer Deep basin
I (Fig. 2.14). In Palmer Deep basin II (Fig.2.14), and HI (Fig. 2.15) high numbers of P. eltaninae, R. subdentaliniformis (included in Reophax spp.), and H. parkerae occur within the uppermost centimeter, then decrease to near zero within few decimeters down core.
A similar pattern is present in core JPC18 from the Andvord drift (Fig. 2.15). P. eltaninae and S. biformis diminish within the upper 2 m. In contrast to this overall decrease in abundances, M. arenacea and T. intermedia occur in variable numbers and do not show a sediment depth related trend in cores mentioned above.
62 GC15 Palmer Basin I (1030 mbsl) (N = 48)
0 Specimens 4 0.0 15 3.0 0 0.0 4-----'---- 1---- .----1 4.— '------L
n 0.8
M. arenacea T. intermedia P. eltaninae
KC27 Palmer Basin H (1364 mbsl) (N=48)
10 0 5 10 0 0.0 4
0.4
0.8 -
1 0 -
1 4 -
P. eltaninaeM. arenacea P. eltaninaeM.
Figure 2.14. Vertical distribution of the most abundant agglutinated species in GC15 from Palmer Deep basin I and KC27 from basin II (per cm^). M. arenacea fluctuates in both cores with no apparent core depth trend.
63 KC17 Palmer Basin III (1016 mbsl) 0 Specimens 6 0
(N = 56)
\T. arenacea T. intennedia P. eltaninae fl. parkerae
JPC 18 Andvord Bay (400 mbsl) 0 4 0 2 4 J I
(N = 56)
M. arenacea T. intermedia P. eltaninae S. biformis
Figure 2.15. Vertical distribution of the most abundant agglutinated species in KCI7 from Palmer Deep basin III and JPC18 from the Andvord drift (per cm ). K.CI7 depicts exponential decreases of P. eltaninae and H. parkerae down core. The vertical distribution of Af. arenacea and T. intermedia seems to be independent of the core depth inKCI7andJPC28. 64 Calcareous foraminifers
The most abundant calcareous species of core GC14 from Palmer Deep basin I is
B. aculeata, followed by B. pseudopunctata (Fig. 2.16). The latter does not occur within the uppermost 20 cm. F. fusiformis occurs in insignificant numbers. None of these species depict a core depth related trend.
In core KC27 from Palmer Deep basin II (Fig. 2.16) B. aculeata and P. bulloides are the most abundant species, occuring first around 1.5 m core depth. B. pseudopunctata is present only in the upper 0.4 m of the core. No calcareous foraminifers were observed below 1.5 m core depth.
B. aculeata is also the most abundant calcareous species in Palmer Deep basin IH
(Fig. 2.17). P. bulloides accompanies B. aculeata, whereas B. pseudopunctata vanishes below 0.8 m.
The upper 2.8 m of core JPC18 from the Andvord drift yielded calcareous foraminifers in almost every sample (Fig. 2.17). The most abundant is F. fusiformis, with two prominent peaks at 0.6 and 2.5 m core depth. Connected with those peaks are occurences of B. pseudopunctata, B. aculeata, and N. iridea, which are otherwise absent in most of the core.
65 GC14 Palmer Basin I (1040 mbsl) 0 Specimens 20 0 40 0
(N = 48 ) 0.4
cn 0.8
2.0
B. pseudopunct.pseudopunct B. aculeata F. fusiformis AC pachyderma
KC27 Palmer Basin EE o 20 0 40 0.0 3.0 (1364 mbsl) I
0.8 -
12 -
2.0 -
2.4-1 B. pseudopunct P. bulloides
Figure 2.16. Vertical distribution of the most abundant calcareous species in GC14 from Palmer Deep basin I and KC27 from basin II (per cm'*). Note that B. aculeata is by far the most numerous species and has the most continuous record.
66 KC26 0 Specimens 20 0 80 0 10 Palmer Basin III I (1388 mbsl)
0.4 7 (N = 48) > GO c . 0.8 - >
:> 2.0 -
2.4-1 B. pseudopunct. B. aculeata
JPC 18 Andvord Bay (400 mbsl)
(N=56)
B. pseudopunct. B. aculeata F. fusiformis
Figure 2.17. Vertical distribution of the most abundant calcareous species in KC26 from Palmer Deep basin III and JPC18 from Andvord drift (per cm^). B. pseudopunctata is present in KC26 only in the upper 0.8 m. Note the pronounced peaks of F. fusiformis in JPC18 from the Andvord drift. 67 2.4. Discussion & Conclusions
Scott and Medioli (1980) suggested that using total assemblages best approximates fossil assemblages in paleoenvironmental studies. This may however be true where biocoenosis and thanatocoenosis bear a close resemblance. In the case of this study, with considerable differences between both, a separate treatment is recommended.
Four major assemblages are proposed below (Table 2.5), based on the statistical analysis.
B. aculeata assemblage
The B. aculeata assemblage occurs solely in the Palmer Deep basins.
Characteristics of this assemblage are high percentages of calcareous species, high standing stocks (# of living specimens at time of sampling per cm^), and high benthic foraminiferal accumulation rates (BFAR, # /cm^yr'^). Living specimens of this assemblage become abundant below 950 m water depth. The reason for the apparent depth limitation of this assemblage could be the extent of the Circumpolar Deep Water
(CDW), which may not be present in the shallower parts of the study area. Ishman &
Domack (1994) described a B. aculeata assemblage from the Bellingshausen Sea, similar to the assemblage defined in this study. They linked the extent of this assemblage to the upwelling of warm and nutrient-rich CDW, causing increased primary productivity.
However, Ishman & Domack used dead & living assemblages combined for their statistical analyses, so there are differences compared to the results of this study. M. arenacea was incorporated into their B. aculeata assemblage, whereas M. arenacea is not an important component in both the thanatocoenoses and biocoenoses of the B. aculeata assemblage defined in this study. 68 Assemblage Equivalent to
B. aculeata Live PC2 (total). Live PC2 (potential fossil). B. pseudopunctata Dead PC2 (total). Dead PC2 (potential fossil) P. bulloides (JP. eltaninae)
F. fusiformis Live PCI (total). Live PCI (potential fossil) {R. subdentaliniformis) Dead PC3 (total)?. Dead PC3 (potential fossil)?
T. intermedia Dead PC3 (total). Dead PC3 (potential fossil) (S. biformis)
M. arenacea Dead PCI (total). Dead PCI (potential fossil) F. earlandi Live PC3 (total)?. Live PC3 (potential fossil)?
Table 2.5. Proposed assemblages in the study area, named after the underlined species. Taxa in brackets are removed from the potential fossil data set.
69 B. aculeata is considered a detritus feeder, showing a characteristic epifaunal or shallow infaunal life style (SenGupta, 1999). High abundances of living B. aculeata in the uppermost sediment centimeter (Fig. 2.9) suggest that this species feed on fresh phytodetritus rather than older organic matter found deeper in the sediment. Kitazato
(1989) observed surface maxima for B. aculeata combined with one or several maxima deeper in the sediment, which may point towards a tolerance of B. aculeata to lower oxygen levels, and/or lower food availability deeper in the sediment (SenGupta, 1999). B. aculeata was also found in oxygen depleted environments (Ohga & Kitazato, 1997).
Not much is known about environmental adaptations of the other dominant species of the B. aculeata assemblage. It was noted that the genus Bolivina might be in general adapted to low-oxygen conditions (Bernhard, 1989). B. pseudopunctata (as
Bolivinellina pseudopunctata) was reported from temporarily anoxic Norwegian fjords
(Alve & Olsgard 1999), together with F. fusiformis (as S. fusiformis). B. pseudopunctata is also an associated species in the B. aculeata assemblage described by Ishman and
Domack (1994) from the Bellingshausen Sea. Analysis of the microhabitat suggests that
B. pseudopunctata feeds on detritus as well, as indicated by the shallow infaunal lifestyle
(Fig. 2.9).
Species associated with the B. aculeata assemblage defined in this study include
P. bulloides and P. eltaninae. P. bulloides was reported from the Pacific ocean below
2200 m water depth (Burke, 1981), the western North Atlantic below 3800 m water depth at the CDW — ABW transition (Phleger et al., 1953), and Norwegian fjords (Mackensen,
1985), suggesting to some authors that P. bulloides is a dissolution resistant species. The
70 results from the surface samples from the Palmer Deep may however imply that P.
bulloides is not very resistant to corrosive conditions, since high numbers of stained
specimens are not matched with an equivalent number of dead tests. The down core
distribution of living specimens of P. bulloides points to a shallow infaunal Hfe style and
phytodetritus feeding, similar to B. pseudopunctata and B. aculeata.
Ecological information from literature about P. eltaninae is scarce. Echols (1971)
used total assemblages (dead and live combined) to define a P. eltaninae association in
the South Orkney and South Sandwich Islands below 1058 m water depth adapted to the
AABW. This observation is consistent with results from the study area. High abundances
of P. eltaninae occur only in the deeper parts of the Palmer Basins. Microhabitat analysis
implies a shallow infaunal lifestyle (Fig. 2.9).
In conclusion, the B. aculeata assemblage defined in this study, including B. pseudopunctata, P. bulloides, and P. eltaninae, is likely to be adapted to open-marine conditions, up-welling of CDW, high primary productivity, and subsequently, large input of fresh phytodetritus. It is thus suggested to use the occurrence of this assemblage in the fossil record as an indicator of the aforementioned conditions, which recently prevailed in the Palmer Deep basins.
F. fusiformis assemblage
The P. fusiformis assemblage is dominant in the biocoenoses of the Andvord drift area (Fig. 2.13). Standing stocks and BFAR are generally much lower than from the B. aculeata assemblage. Stained specimens of F. fusiformis are abundant below 500 m water depth, whereas live R. subdentaliniformis are quite evenly distributed in all water depths.
71 F. fusiformis (as Stainforthia fusiformis) was reported from Norwegian Qords (Alve,
1990) and believed to survive dysoxic conditions. Jorissen et al. (1992) found extremely high abundances of F. fusiformis (as S. fusiformis) following anoxic periods in the
Adriatic Sea.
Murray (1991) summarized benthic recolonisation following volcanic activity from the northernmost part of the Antarctic Peninsula. He found that after an ash-fall out the area was colonized by rich faunas, dominated first by N. bradii and subsequently by
F. fusiformis (as S. fusiformis).
N. bradii accompanies F. fiisiformis in Andvord Bay, but only in very limited numbers. F. fusiformis (as S. fusiformis) was also reported as being able to sequester chloroplasts (Bernhard & Alve, 1996) that may provide oxygen to the host in oxygen depleted environments. The authors found also that F. fusiformis changes its microhabitat in response to changes in oxygenation. Apparently F. fusiformis prefers to live just above the dysoxic boundary. According to the TROX model (Jorissen et al., 1995), infaunal species such as F. fusiformis remain in the uppermost sediment centimeter if oxygen is limited. Recent research from Harris et al. (1999) points to high organic flux to the seafloor in the Andvord drift area. The high organic content depletes oxygen in the sediment and results in the shallow infaunal life style of F. fusiformis.
It is important to note that F. fusiformis (as S. fusiformis', Alve, 1995) seems to be sensitive towards salinities lower than 3 l%o. The associated species of the F. fusiformis assemblage R. subdentaliniformis was also mentioned by Bernhard (1993) for its ability to survive temporary anoxia. R. subdentaliniformis is adapted to an epifaunal life style, as indicated by its peak abundances at the uppermost 0.5 cm in the study area (Fig. 2.11).
72 The even spatial distribution suggests that R. subdentaliniformis is a generalist in the study area, rather independent of water depth or water mass distribution, and thus not very useful for paleoecological reconstructions.
The F. fusiformis assemblage bears some resemblance in composition and spatial extent to the Fursenkoina spp. assemblage described by Ishman and Domack (1994).
They linked the distribution of this assemblage to the extent of the Weddell Sea
Transitional Water (WSTW). The WSTW is therefore a likely provider for the organic matter that accumulates in the Gerlache Strait. It is therefore assumed that the F. fusiformis assemblage defined in this study is likely to be adapted to high organic contents, normal salinities, and intrusions of the WSTW into the study area.
T. intermedia assemblage
S. biformis is actually the most abundant species of this assemblage but because of its low preservation potential the assemblage was named after T. intermedia, which is the most abundant species with sufficient preservation potential. This dead assemblage is abundant in the area that is covered by F. fusiformis Live PCI (Fig. 2.13). The T. intermedia assemblage contains mainly agglutinated taxa. The typical detritus feeder from the Palmer Deep basins such as B. aculeata are very scarce or absent. There is no direct equivalent of the T. intermedia assemblage in the biocoenoses. Subsequently, the standing stocks of the dominant species are very low. S. biformis is especially rare, only three stations from the Andvord drift yielded stained specimens.
Not much is known about the ecological preferences of T. intermedia. Ishman
(1990) reported it from Marguerite Bay, together with S. biformis, in organic rich
73 sediments. Alve and Nagy (1990) claimed that S. biformis in Norwegian Qords tolerates
even lower oxygen contents (<0.5 ml/IOa) than F. Jusiformis, and salinities as low as 19.6
%o. Given this, the T. intermedia assemblage has likely different ecological adaptations
than F. fursenkoina Live PCI despite the same spatial extent.
The generally low standing stock, BFAR, and the restriction to mostly
agglutinated taxa suggests that the T. intermedia assemblage may occur when conditions
are unfavorable to other species. Possible conditions include salinity fluctuations, which
can not be tolerated by calcareous foraminifers such as F. fusiformsis. A seasonal study
of benthic foraminifers, during, for instance, times of sea ice cover, may confirm the
aforementioned hypothesis.
M. arenacea assemblage
The M. arenacea assemblage does not occur in the biocoenoses. Thus, it cannot
be proven that the important species of this assemblage actually lived together. The M.
arenacea dead PCI (potfossil) assemblage occurs in areas that are covered by F. fusiformis live PCI (Fig. 2.13). The associated species F. earlandi occurs in large numbers in the biocoenoses, but stained M. arenacea are scarce or absent.
It is thus likely that M. arenacea multiplies earlier in the year, and that the Af. arenacea assemblage may be considered a mixture of annual assemblages rather than a true biocoenosis. Moreover, F earlandi seems to have a very low preservation potential
(see chapter 2.4.2). Thus, F. earlandi may not show up in the fossil record. Unless detailed seasonal data become available that changes this view, the M. arenacea assemblage will therefore be considered monospecific in the fossil record. Two studies defined M. arenacea associations in the Southern Oceans (Murray, 1991). Echols (1971) 74 reported Af. arenacea and F. earlandi from the South Orkney and South Sandwich
Islands, and Osterman & Kellog (1979) in the Ross Sea. An adaptation of Af. arenacea to salinities of 34.45-35.19 %o and temperatures of —1.9 to 0.6 °C was proposed (Murray,
1991). However, all the aforementioned studies used total (living and dead combined) assemblages rather than biocoenoses. Thereby, there is little ecological information available about Af. arenacea, and whether the species actually lived under those conditions.
Other species of the genus Miiiammina are known to survive and even thrive under polyhaline conditions. Miiiammina fusca is reported from hypersaline lagoons
(Alve, 1995). It is therefore hypothesized that Af. arenacea may have a similar ecological adaptation. Evidence for this may be the fact that only a very limited number of live Af. arenacea were found in the study area, but high numbers of dead tests. It is suggested, therefore that this species multiplies when conditions were intolerable for other species.
During the autumn season, when sea-ice is generated, the underlying surface waters become hypersaline and super-cooled, and sink to the seafloor.
Since other dominant species in the study area require normal marine salinity, only Af. arenacea could survive, and subsequently, due to the absence of food competition, occur in large numbers. This would explain the almost monospecific occurrence of Af. arenacea in the thanatocoenosis. Until more detailed seasonal information about Af. arenacea is available, the use of this species as indicative for high salinities is proposed.
75 Preservation potential of agglutinated, foraminifers
The agglutinated taxa of the upper two cm of the surface samples are diverse and abundant. However, from peak abundances, around one cm, most agglutinated species diminish near to zero down core. For example, H. parkerae in station G31 from Palmer
Basin DI (Fig. 2.10) shows peak abundance in the upper 0.5 cm, then decreases exponentially down core. A similar pattern is present in the distribution of P. eltaninae,
R. subdentaliniformis, and S. biformis. The only agglutinated species to escape this trend are M. arenacea and T. intermedia. The stations of Palmer transect 3 depict increasing numbers of M. arenacea with sediment depth (Fig. 2.5, 2.10). The same is true for T. intermedia in the Andvord Bay transect (2.11).
The explanation for this pattern may be a recent change in the benthic assemblages and/or the rapid disintegration of agglutinated tests. Le venter et al. (1996) proposed solar driven 200-year climatic cycles in the Palmer Deep area. If the reason for the disappearance of the agglutinated species was the proposed climate change, longer sediment cores should show their recurrence at greater depths. To answer this question, longer cores from the study area have been investigated. Cores K17, K27, K26, G14,
G15, and JPC18 are more than 2 meters long.
The records are long enough to cover at least three of the proposed 200-year cycles, given that the maximum sedimentation rates in the study area of 0.35 cm per year
(Leventer et al. 1996). None of the aforementioned cores showed a recurrence of P. eltaninae, R. subdententaliniformis, and H. parkerae at greater sediment depths (Figs
2.14-2.17), indicating that their vertical distribution is strongly influenced by disintegration rather than ecological changes.
76 A second group is constituted by P. eltaninae and S. biformis, which seems to
persist deeper in the sediment. In JPC 18 (Fig. 2.15) they are both relatively abundant
down to 1.8 m sediment depth, and below that limit scarce or absent. The distribution of
M. arenacea and T. intermedia on the other hand do not show a clear depth-related
distribution pattern. They occur in variable numbers throughout all cores investigated. It is concluded that they are not strongly influenced by disintegration and may thus be
useful for paleoecological reconstructions. That some disintegration of T. intermedia took place is indicated by the occurrence of internal linings without the mineral test in core
GC15 (see chapter 3). The effect may be negligible, since the number of linings is very low, compared with the number of mineral tests of T. intermedia.
In order to quantify the preservation potential of agglutinated species, preservation indices have been calculated, based on average Standing stock and BFAR of single species from the surface samples (Table 2.6).
Most agglutinated species are below 50 % theoretical preservation. Only three species are above this level, T. intermedia, P. eltaninae and S. biformis, which is consistent with the conclusions derived above. A discrepancy is that T. intermedia withstands disintegration much better than predicted, and the reason for its unusual preservation potential may be the possession of thick organic linings (see chapter 3). M. arenacea depicts unusual 125 % preservation, which gives further indication that the production of this species was much higher earlier in the year and that the preservation potential of this species must be outstanding. It is thus proposed that all agglutinated
77 Standing stock BFAR PI (#/cm^ ky"') (#/cm^ ky'^) (%)
M. arenacea 308 392 127.11
S. biformis 40 35 87.97 T. intermedia 138 79 57.51 P. eltaniae 422 215 50.88
Textularia spp. 33 12 35.68 H. parkerae 569 126 22.09 R. dentaliniformis 173 26 15.17 P. challengeri 26 3 12.94 H. guttifera 26 3 12.63 H. pilufera 19 2 10.64 H. canariensis 190 10 5.40 R. subdentaliniformis 915 42 4.59
Table 2.6. Average standing stock Giving tests), benthic foraminiferal accumulation rates (BFAR, dead tests), and Preservation Index (PI) of the most abundant agglutinated species from the study area, ordered by increasing preservation potential. BFAR were calculated using the upper five sediment centimeter of the surface samples and published sedimentation rates. The standing stock has been converted to #/1000 years for direct comparison with the BFAR.
78 species except M. arenacea and T. intermedia should be excluded from the interpretation
of Holocene assemblages from the study area. Possible reasons for the differences in
preservation potential of agglutinated species are discussed in chapter 4 of this
dissertation.
Dissolution resistance of calcareous foraminifers
Dissolution effects of calcareous tests may be a serious concern for interpreting
foraminiferal assemblages from Antarctica (Li et al., 2000). Most calcareous specimens
from the surface samples investigated in this study exhibit signs of partial dissolution,
resulting in the dull white color of tests. Also there is a suspicious lack of calcareous
epifauna, although linings of at least one species have been observed (see chapter 3). The
removal of calcareous species from the thanatocoenosis results in residues of agglutinated
taxa, which hinders paleoecological reconstructions. Until recently, it was a common
view that calcareous benthic foraminifers cannot live under conditions that are corrosive
to their tests. A recent study from Green et al. (1998) however suggests that calcareous
foraminifers can indeed occupy substrates that are corrosive to their tests, however postmortem dissolution destroys most of the empty specimens in short time.
This supports earlier assumptions by Ward (1987), who found high numbers of
living F. earlandi but few dead specimens in McMurdo Sound. She concluded that this is due to the ability of this species to secrete tests in carbonate undersaturated waters and that the dead tests are almost entirely removed by postmortem dissolution. Dissolution in this case may be caused by the influence of a Calcium Compensation Depth (CCD), or corrosive pore waters in the sediment.
79 Dissolution resistance scale
The vertical distribution of the most abundant calcareous species of the study area
has been investigated to quantify dissolution resistance of single calcareous species. Four
major calcareous genera are present in the surface samples. B. aculeata was considered dissolution resistant by previous studies (Mackensen et al. 1993). This thick-walled species shows relatively low numbers of living tests, but is very abundant in the thanatocoenoses. In contrast B. pseudopunctata and Fursenkoina spp. depict very high numbers of living tests that are not matched by proportional numbers in the thanatocoenoses. This pattern might be caused by a recent migration of those species in the year of sampling.
However, a previous investigation in the study area by Ishman & Domack (1994) shows similar assemblages, thus the recent change can be ruled out. Thereby it is proposed that B. aculeata has the highest dissolution resistance, whereas species like B. pseudopunctata and F. fusiformis are less resistant. A third class of dissolution resistance is defined. Abundant linings of Cibicides lobatulus have been found in samples that yielded no calcareous tests of this species (Chapter 3). Apparently, dissolution removed the tests completely, even in samples containing other calcareous taxa. In the same class falls the planktonic foraminifer N. pachyderma. Planktonic foraminifers have in general a much lower resistance towards dissolution (Sen Gupta, 1999)
To quantify the dissolution resistance scale, the preservation indices for the major calcareous species have been calculated (Table 2.7). Species with high standing stocks such as Fursenkoina spp and B. pseudopunctata show comparatively low BFAR values, resulting in less than 8 % preservation of the original numbers.
80 In contrast, the more similar BFAR and standing stock values of B. aculeata account for the highest PI value (67 %) of all calcareous species in the study area. F. fusiformis seems to be the least resistant species. An average of 1408 living F. fusiformis resulted in only 34 fossil specimens per cm^kyr'\ In other words, only 2.43 % of F. fusiformis are preserved postmortem under current conditions.
In conclusion, observations based on the vertical distribution can be used to evaluate and quantify the preservation potential of calcareous species. Furthermore, it is recommended to use the dissolution resistance scale for the interpretation of fossil assemblages. If, for instance, an assemblage yielded only B. aculeata, it is stiU possible that the less resistant species were originally present. On the other hand, the presence of
F. fusiformis or N. pachyderma should indicate that dissolution did not markedly alter the assemblages.
Fossil assemblages: How much information will be preserved?
The scores of benthic Q-mode assemblages are listed in table 2.8 for comparison.
Three data sets have been calculated, biocoenoses, thanatocoenoses, and biocoenoses / thanatocoenoses combined. All three data sets have been calculated for the total and the potential fossil version.
81 Standing stock BFAR PI (#/cm^ ky‘^) ( # W ky-^) (%)
B. aculeata 946 634 67.04
A. echolsi 85 23 26.45 G. biora 38 4 9.30 P. bulloides 479 39 8.07 B. pseudopunctata 3016 232 7.70 G. crassa 81 5 6.28 F. earlandi 1344 83 6.14 N. bradii 31 1 3.53 F. fusiformis 1408 34 2.38
C. lobatulus -- <2.38 N. pachyderma - - <2.38
Table 2.7. Average standing stock (living tests), benthic foraminiferal accumulation rates (BFAR, dead tests), and Preservation Index (PI) of the most abundant calcareous species from the study area, ordered by increasing preservation potential. BFAR were calculated using the upper five sediment centimeter of the surface samples and published sedimentation rates. The standing stock has been converted to #/1000 years for direct comparison with the BFAR.
82 The B. aculeata assemblage shows few changes in all data sets. The removal of
the agglutinated P. eltaninae does not hinder recognition of this assemblage in the
statistical analyses. P. bulloides, an important species in the biocoenoses, is diminished in
the thanatocoenoses, which is most likely due to its low dissolution resistance.
The same process applies for B. pseudopunctata, dominant in the live
assemblages, but less important in the dead assemblages. Although diagenetic processes
may lead to a monospecific composition, it is predicted that the B. aculeata assemblage is
traceable in Holocene sediments by its dominant species.
The F. Jusiformis assemblage incorporates R subdentaliniformis, which has a low
preservation potential, and disintegrates rapidly within the first couple of centimeters.
Therefore, this assemblage will probably appear monospecific in Holocene sediments
from the study area. More difficult to estimate are the impacts of calcium carbonate
dissolution on F. fusiformis, which has a low resistance. If only a small number of tests
are present, F. fusiformis may be completely removed by dissolution, as indicated by its
absence of in the lower parts of the surface samples from the Andvord drift. However, F. fusiformis is at times very abundant below 0.4 mbsf in core JPCI8 from Andvord Bay
(Fig. 2.17). How can this be explained? The most likely explanation may be that this
species is able to occur in large blooms, in which case the production may exceed
dissolution. It is therefore concluded that the F. Jusiformis, despite the low dissolution
resistance of its dominant species, may be recognizable in the fossil record.
The T. intermedia assemblage is hypothetical at this point. The statistical analysis
of the thanatocoenoses overlaps it with the F. fusiformis assemblage and the results from
the biocoenoses suggest a difference in seasonal productivity. The other dominant species
83 of r. intermedia assemblage, S. biformis, has a relatively high preservation potential.
Despite this, S. biformis becomes rare in longer sediment cores from the region, and may be completely removed from the fossil record. It is thus concluded that the T. intermedia assemblage may appear monospecific in Holocene sediments.
The M. djrenacea assemblage is hypothetical as well. The associated species F. earlandi may be removed by dissolution, therefore, also the M. arenacea assemblage may appear monospecific in the fossil record.
The F. earlandi Live PCS assemblage is likely not to be preserved in the fossil record, since its dominant species F. earlandi and B. pseudopunctata have low dissolution resistance. In addition, the associated species R. subdentaliniformis disintegrates rapidly.
84 C H A P T E R S
ORGANIC FORAMINIFERAL LININGS
3.1. Summary
In this study, the composition of organic foraminiferal lining assemblages from modem and Holocene sediments from the Palmer Deep area is investigated. New methods for the retrieval and preservation of linings are proposed. Epoxy Resin can be used to preserve linings for a fast qualitative evaluatioit A modified palynological treatment is suggested for quantitative approaches.
Three different types of linings were recognized, and the taxonomic affinities to the species level were defined by chemical removal of the mineral test of handpicked specimens. The linings observed belong mainly to Trochammina intermedia, which is possibly the first report of linings from this species. Additionally, the recognition of megalospheric and microspheric linings produced by Cibicides lobatulus are considered the first report of linings from this species from the Southern Hemisphere.
Future studies of the chemical composition of organic linings are expected to increase our knowledge in the growing field of molecular biology, contributing to long debated issues such as generic and family relationships, classification, evolutionary
85 derivation of major groups, bipolarity of foraminifers, and macro-/ micro-evolution.
Additionally, carbon isotope ratios of linings might be used as a proxy of paleoproductivity or for enhancing the precision of the radiocarbon dating of marine sediments.
3.2. Introduction
Foraminiferal organic linings consist of a semitransparent to brown-colored series of individual chambers linked by a foramen (de Vernal et al., 1992). Biological functions of linings include providing a skeletal test template, a barrier to external environments, a shield against solar radiation, and a control for nutrient and excretion transfer (Banner et al., 1973). The chemistry of linings has yet to be determined, though there are indications that it may vary from species to species (Banner et al., 1973). Arenaceous species, for instance, yield linings composed of a glycoprotein complex (“tectin”, Hedley,
1963). Linings are chemically resistant and thus not dependent on pore water chemistry, and provide information where dissolution has removed their mineral outer shells (tests hereafter). Not all foraminifers possess preservable Linings (Stancliffe, 1996), and little has been done on identification to the species level.
The size of linings in relation to their tests has been under discussion since their first illustration by Ehrenberg (1854). Woods (1955) illustrated the lining of Bolivina and an unidentified piano-spiral "microforaminifer". The main obstacle in evaluating the full potential of linings for paleoecological research lies in the different preparation methods used by the micropaleontologist and palynologist.
86 In palynological studies, the fraction larger than 125 pm may be dismissed, whereas until recently only the fraction larger than 125 pm was used by the micropaleontologist. For these reasons the term "microforaminifers" was introduced.
However, recent studies proved that foraminiferal tests may constitute an important part of the fauna even in the > ~ 36 pm fraction.
De Vernal et al. (1992) pointed out that linings are flexible while wet and thus pass easily through smaller sieve sizes than their actual size. Given that the most widely utilized sieve size for recovery of foraminiferal tests today by the micropaleontologist is
63 pm, the recovery of linings should thus be undertaken with a smaller sieve size.
In palynological studies, the sample is treated with hydrofluoric acid (HP), which destroys all agglutinated tests composed of silica, thus the palynologist does not have the entire foraminiferal assemblage available. Other rigorous treatments include centrifuging of the residue. Not surprisingly, fragmentated linings, often broken into units of 1-2 chambers are produced (Traverse & Ginsburg, 1966). Standardized methods that enable quantitative assessment are thus needed in order to exploit the full potential of foraminiferal organic linings.
The number of studies that utilize linings for paleoecological research is limited
(Table 3.1). Muller (1959) reported linings of the genus Cibicides and Planulina and their distribution in recent Orinoco delta sediments. One of the first quantitative attempts to use linings for paleoecological reconstructions was made by Traverse & Ginsburg (1966) on modem sediments from the Great Bahamas Bank, based on the number of
"microforaminifera per gram" without taxonomic identification. Cohen & Gruber (1968)
87 Wetzel (1957) cf. Rotnliidnc, cf. Tc.sliihii iiiliic Rccoijniml "inicroforaminifers" in earlier wtirk.i (c.g, Wison & llofineisler, 1952; Grayson, 1956), Nonlicni Gcnnany, Crelaccous
Muller (1959) Cibicides, Plaimliini, (Oiiiiit/uehciiliiui ) Dissolved individual megalospheric lests, Noled lliai H olivina, Cassiilutina , h'poniiles, Chbiiietiim , Gtobomlalia , Nonion, Plamilinii, and Siphonia did not possess linings, Orinoeo della, modem surface samples
Traverse & Ginsburg ( 1966) planispiral & iroclmiil "microforaminifers" Noted that taxonomic identification was nut attempted. Used microforaminifera per gram as proxy. One of the troehoid "microforaminifer" resembles linings of T, inlcrmciiia. Great Itahama Bank, modem surface samples
Cohen & Guber ( 1968) Ammonia Hmnctes Dissolved individual tests. Noted that few additional species yielded unconnected un identifiable remains, I'loria Everglades, modem surface samples
Stancliffe (1989) morphotypes Proposed informal classification of linings. British Oxfordian sediments
00 00 dc Vernal etal. (1992) Hiiliminella eiesontissima, Melonis zanilamee, Dissolved individual tests. Noted that Bucelia, Hidiminn, Cussiduiina, EpsUomineita, Enrsenkoina, EiphitHum excovolinn, Cibiciiles iobalnlns, lloenbindino, Islondiella, Nonionetia, Oridorsalis , and PuUenia did not yield linings. Definition and Cibicides wiiellerssloifi of lining/shell ratio to calculate dissolution index, Davis Strait, North Atlantik, Holocene
Steinsund & Hald (1994) Cibicides hbatulns Noted that linings weren oflcit visible through partial in sllii dissolution of the lest. Whole linings o f C, Iobalnlns without tests were reported, Barents Sea, modem surface samples
Mathison & Chmura (1995) Ammonia beccari, Miiiammina fnsca ('!) Direct taxonomic identification was not attemped but derived from a study of foraminifers (Scott el al., 1991). This procedure may explain a considerable confusion in taxonomy. The agglutinated M .fn sa was described as a calcareous Rotalidae, Since no figures were provided it is (ptestionable whether jV./it.va/ was actually the origin of the linings, Mississippi Delta, modem surface samples
Murray & Alve (1999) Ammonia bcccliarii The existence of other iining-bearing species is mentioned, but not specified, Skagerrak-Kattegat, modem surface samples
Table 3. 1, Listing of selected references recording foraminiferal organic linings with taxomomic classification dissolved specimens of several calcareous species, but only linings of Ammonia limnites
were recovered. De Vernal et al. (1992) dissolved hand-picked specimens of several
genera from the North Atlantic, and described linings of Buliminella elegantissima.
Mêlants zandamee, Elphidium excavatum, Cibicides lobatulus, and Cibicides
wuellerstorfi. De Vernal et al. (1992) defined a dissolution index based on the organic
lining/calcareous shell ratio, and applied it to Holocene assemblages, which may be the
only attempt to apply quantitative lining assessment data to Quaternary paleoclimatic
research.
Another possible application of organic linings involves radiocarbon dating. Bulk
organic matter has thus been frequently used for radiocarbon dating, although reservoir corrections are reported to be as large as 22,970 years (Andrews et al., 1999). Bulk
organic matter contains a variety of organisms with presumably varying vital effects as
well as reworked material, which in part explains the large variability of the reservoir correction. It is hypothesized that, by measuring the carbon ratios of linings of a single foraminiferal species, the precision of the radiocarbon method applied to marine sediments might be considerably refined.
Additionally, linings could be used in the growing field of molecular biology, unraveling issues such as bipolarity of foraminifers, evolution rates, and taxonomic problems. Molecular investigations of foraminiferal organic tissue have already challenged fundamental paradigms in foraminiferal research. For instance, the discovery of “naked” foraminifers (Pawlowskiet al., 1999) contradicts the traditional definition of foraminifers as shelled protists. The proposed reclassification of the foraminiferal genus
Miiiammina (Fahmi et al., 1997) questions the classical taxonomy based on test
89 composition/structure. Even more impact is expected by the recent discovery of Darling et al. (2000) that morphospecies of planktonic foraminifers defined by the micropaleontologist may not be genetically continuous species with a single environmental preference. This challenges the traditional extensive use of those morphospecies for paleoclimate reconstruction. Since linings are preservable in sediments of Quaternary and older ages (Stancliffe, 1996), their potential for extending our knowledge of such issues is evident.
3.3. Classification
Early attempts at classification of foraminiferal linings (e.g. Macko, 1963) have been rejected by Loeblich & Tappan (1965) who argued that the additional taxa created would “merely add to an already burdensome foraminiferal taxonomy”. Deâk (1964) proposed the supragenetic term Scytinascia for all linings, which was subsequently used by a few authors. Pantic & Bajraktarevic (1988) described "Nannoforaminifera”, assigning some specimens to the family and even generic level. Stancliffe (1989, 1996) proposed an informal classification based on the chamber arrangement of the linings and introduced uniserial, biserial, planispiral, and trochospiral morphotypes. Schemes similar to the latter are commonly used by palynologists.
However, in the opinion of the author, the chamber alignment alone does not yield major information about the classification of a certain species. Trochospiral forms, for instance, are produced by both calcareous and agglutinated foraminifers, which may be adapted to a variety of environments. In order to utilize linings for paleoenvironmental research a classification on at least the family level is necessary.
90 It is proposed that the appropriate way to do this is the direct comparison of foraminiferal mineral outer test with their inner organic lining recovered from the chemical removal of the shells (Cohen & Guber, 1968; de Vernal et al., 1992). In
Mesozoic and Paleozoic strata this proposal raises some difficulties. Sediments of this age have frequently undergone diagenesis or early metamorphism, with the result that either the linings or the shells or both are destroyed. A direct comparison of both is rarely possible.
Tertiary and especially Quaternary sediments on the other hand are often unlithified and yield better preservation conditions for foraminiferal linings and shells, as indicated by abundant reports of foraminiferal linings and tests in the same sample (e.g.
Murray & Alve, 1999). Future classification schemes should be based on the direct comparison of linings with foraminiferal tests, after which the foraminiferal taxonomy can be applied to the linings. The chemical removal of the foraminifer shells is proposed as a method to provide this crucial information.
3.4. Methods
Previous methods — a damage report
The foraminiferal linings observed in this study appeared delicate and soft bodied.
The degree of lining disintegration increases with increase in the size of the test. The higher resistance of small linings to processing may be one of the reasons for the original description as “microforaminifers” or “nannoforaminifers”. Traverse & Ginsburg (1966) for instance recognized that small linings (“microforaminifers”) are better preserved, but failed to make a causal connection between their observation of numerous small
91 firagments of 1-2 chambers and the centrifuging procedures employed in their methods.
Dependent on the species, those fragments are 5-25 um in diameter, another apparent reason why the misleading term "microforaminifer" was applied by the palynologist. The major processing methods that may contribute to the damage of linings are outlined below.
Storage
An unsealed sample container, which allows the gradual dehydration of the sample will alter the lining assemblage composition. The foraminiferal linings encountered in this study frequently disintegrated when the sample dried, after which only the most resistant smaller specimens survived. Other linings, mostly larger ones, were lost completely. Drying of the washed sample in an oven is a common method used in foraminiferal research (e.g. Murray, 1999), and can be expected to cause even more damage. The sample must be kept wet at all times, and storage in alcohol solution will prevent bacterial destruction.
Sieving
Wet sieving is the most common method of retrieving microfossils from unlithified Quaternary sediments. Hodgkinson (1991) pointed out that sieving may lead to the partial destruction of microfossil linings. Large linings were often found in a fragmented condition despite the use of low water pressure during wet sieving. For further quantitative investigations, the sample treatment with formaldehyde is suggested, which is known to strengthen soft organic tissue (personal communication J. Mitchell,
92 2000). As mentioned earlier. De Vernal et al. (1992) pointed out that linings are flexible while wet and thus pass easily through smaller sieve sizes than their actual size. Given that the most widely utilized sieve size today is 63 pm, the recovery of linings should thus be accomplished with a smaller size screen. Preliminary observations suggest that the 36 pm sieve retained the vast majority of undamaged linings of adult specimens in the study area.
Centrifuging
Centrifuging of the residue is a common method of concentrating microfossils in palynological studies. Hodgkinson (1991) suggested that centrifuging is size selective and biases assemblage composition, and should be only used for taxonomic research.
Given the aforementioned delicate nature of linings, it is not surprising that fragmented linings, often broken into units of 1-2 chambers, were reported after centrifuging (e.g.
Traverse & Ginsburg, 1966).
Chemical methods
The dispersant known as ”Calgon” (sodium hexametaphosphate) is frequently used to clean foraminiferal mineral tests. “Calgon” was not used in this study, to avoid possible impacts of “Calgon” on lining stability.
Hydrochloric acid (HCl) is frequently utilized in palynological processing to dissolve any carbonate in the sample before the treatment with hydrofluoric acid (HF).
The strength commonly used is 10%. Handpicked foraminifers that were dissolved with
10% HCl showed violent outgasing of CO 2 from the calcareous test with partial
93 destruction of the soft lining. A weaker solution (~ 1% HCl) was found to be more suitable for the recovery of whole linings. The HCl treatment may be omitted entirely, in which case the carbonate of the foraminiferal tests is converted to fluorite by the HF treatment (Grayson, 1956; Stancliffe & Matsuoka, 1991). The latter authors pointed out the advantages of this approach to the micropaleontologist; the remineralized tests are well preserved with no evidence of the chemical processing and are translucent to the transmitted light of a palynological microscope. The morphological relationship between foraminiferal tests and linings can thus be directly investigated.
Oxidative treatments such as nitric acid and acétylation (e.g. Traverse &
Ginsburg, 1996) are used in palynological studies to destroy kerogen types and miscellaneous organic matter, and concentrate palynomorphs (Woods et al., 1996).
However, it cannot be taken for granted that all linings survive oxidative treatment only because some species are known to withstand this procedure. Possible impacts of oxidants on lining stability should thus be determined.
The traditional standard methods employed in foraminiferal analyses raise many potential obstacles to the recovery of undamaged linings. It is thus not surprising that there has been a poor correlation of micropaleontological and palynological results to date.
94 Proposed standardized methods
To overcome the shortcomings of previous methods, the author proposes new, specific methods for the recovery of foraminiferal linings as outlined below.
The use of Epoxy Resin
In order to facilitate fast qualitative investigations of the lining assemblage composition Epoxy Resin embedding was used following wet sieving. The Epoxy Resin used in this research is produced by Struers (http://www.struers.com/) under the trade name Epo-fix. Epo-Fix is an old product that has been used only in the metallographic field until recently. It has very good sectioning properties, good adherence to the sample, very low viscosity, easy curing in molds (no orientation problems), and quick cure times.
By adding Epodye (a fluorescent dye) it was noted that identification of pores and cracks is made: easy (http://www.struers.com/).
The samples investigated here consisted mainly of diatomaceous mud and ooze.
The > 63 |xm fraction was usually very small (~ 0.01 g). De Vernal et al. (1992) pointed out that linings are flexible while wet and thus pass easily through a 125 pm sieve. In order to separate the mineral tests of foraminifers, which are mostly larger than 125 pm, from linings, the samples were wet-sieved with 63 :m and 125 :m sieves. The fraction 63 pm - 125 pm was treated with Epoxy Resin.
Embedding in Epoxy Resin allows a more complete recovery of the lining. The use of Epoxy Resin also aids in the preservation of certain small complete foraminiferal tests, which are at times extremely fragile. Combined with this benefit is the ability to recognize stained protoplasm. Usually, a drop of water is added to the test, after which
95 the stain is visible. Calcareous taxa such as B. pseudopunctata and F. earlandi, however, are often so fragile that at times this procedure resulted in the total disintegration of the test. Epoxy Resin both preserves the tests, and renders the stain visible.
Agglutinated taxa, whose red-brownish tests may hinder the recognition of protoplasm, become translucent in Epoxy Resin, thereby making the stain visible.
Finally, chemical investigations of foraminiferal tests can be carried out with the same sample, since Epoxy Resin is frequently used as the embedding medium for SEM analysis (personal communication J. Mitchell, 2000).
The 63 pm fraction may not allow a 100% recovery of the linings, but will permit retrieval of most of the undamaged adult specimens. The sieve size is somewhat larger than necessary to retrieve juvenile or fragmented specimens, but has been chosen since most of the siliceous ooze passed through and the remaining material was reduced to trace quantities. A drawback of this method is that it cannot be applied directly to samples with high percentages of sand-size clasts. In these cases, heavy liquid separation has to be used first to remove the bulk of the clastic material. After several experimental runs the following basic technique was developed.
96 1) Keep sample wet at all times to prevent disintegration of linings. Note the volume of
the sediment sample. The dry weight, necessary to calculate “forams/g”, must be
calculated from a secondary sample split, if desired. In this study, 5-10 cc of sediment
generally yielded a representative sampling of the lining assemblage.
2) Wash sample through nested 63 pm and 125 pm sieves with low water pressure.
Dehydrate the 63 pm - 125 pm fraction with 98% alcohol solution and store in
watertight container. The > 125 pm fraction can be dried and used for normal
micropaleontological counts. The 63 pm - 125 pm fraction may be investigated for
mineral foraminiferal tests either wet or after the application of Epoxy Resin.
3) Pour 63 pm - 125 pm fraction onto a plastic cup (e.g. from snap-cap vial). Allow
alcohol to evaporate, but prevent sample from drying completely. The Epoxy Resin
will not harden thoroughly if the sample is too wet. Pour Epoxy Resin over the
sample until it is at least 5mm covered. If an air bubble free sample is preferred put
sample into a vacuum chamber. Let sample harden for at least 24 hours. The bottom
side of the Epoxy Resin sample can be directly investigated under a binocular
microscope. If desired, the sample can be ground to a thin section, and investigated
from the top side.
97 Palynological preparation techniques
A limited number of samples were treated utilizing modified palynological methods described below in order to test the reliability of Epoxy Resin to preserve foraminiferal linings. First attempts did not lead to a concentration of linings after HP treatment. Apparently, decanting during the washing processes resulted in loss of material. The use of a 36 pm or smaller sieve during decanting is highly recommended to avoid the loss of floating linings. Furthermore, the relatively organic rich sediments (-1-2
%) from the study area yielded large quantities of amorphous organic matter, which hindered the recognition of foraminiferal linings. A gentle wet sieving through a 36 pm sieve before the HF treatment solved this problem. After several experimental runs the following basic technique was applied and is recommended in future foraminiferal lining research.
98 1) Keep sample wet at all times to prevent disintegration of linings. Note the volume of
the sediment sample. The dry weight, necessary to calculate “forams/g”, must be
calculated from backup samples, if desired. In this study, 5-10 cc of sediment
generally yielded a representative sampling of the lining assemblage.
2) Wash sample through 36 jxm and 125 pm sieves with low water pressure and without
additional solvents. Store the 36 pm - 125 pm fraction in watertight container in 98%
alcohol solution. The >125 pm fractions should be routinely examined, though they
did not yield any linings in this study.
3) Pour the 36 pm to 125 pm sample into a HF and HCl resistant beaker and place it
under a fume hood. After settling of the sample, decant the excess alcohol. From here,
two different approaches are possible. If the removal of calcareous tests is desired,
acidize the sample with HCL (1 %), and allow reaction for at least 24 hours. A
stronger solution usually results in violent reaction of the foraminiferal calcite and the
subsequent destruction of many linings. If reaction is not complete add small amounts
of fresh acid and allow standing for longer periods. If the recovery of calcareous tests
is preferred, omit the HCl treatment. Calcite will be converted to CaF by the
subsequent HF treatment, which preserves calcareous shells (see Stancliffe &
Matsuoka, 1991).
99 4) After allowing a settling time of at least 20 min between washings, pour off liquid
and wash residue twice with distilled water. Use a 36 :m sieve during pouring in order
to recover floating material.
5) Add three times its volume of HF (48%), cover with a lid and allow reaction to
continue for 24 hours. If reaction is not complete add small amounts of fresh acid and
let stand for longer periods.
6) Pour off acid and wash residue at least three times (see 4). Add three times its volume
of HCl (10%), heat the sample on a hot plate for 20 min. When the liquid starts to
vaporize, let sample cool for at least 5 min and pour off acid. Repeat the HCL
treatment at least once more. Wash residue at least three times (see 4). Use a 36 :m
sieve during pouring to recover floating linings. Avoid centrifuging.
7) Store the residue in 98% alcohol solution. Drop a small amount of residue in the
center of a glass slide and allow alcohol to evaporate, but prevent sample from drying
completely. Add 1-3 drops of mounting material and disperse uniformly. Cover with
cover glass and put slide into a vacuum chamber.
100 3.5. Objectives
Identification of linings
Tests of the important calcareous species from the study area were carefully decalcified with HCl (1%) applied by a fine brush to prevent violent outgasing of CO 2 .
The purpose here was to define presence and taxonomic affinities of the linings to the species level. Benthic foraminifers were represented by the following species:
Astrononion echolsi, Bolivina pseudopunctata, Bulimina aculeata, Cassidulinoides parkerianus, Cibicides lobatulus, Fursenkoina earlandi, Fursenkoina fusiformis,
Globocassidulina biora, Globocassidulina crassa rossensis, Nonionella iridea,
Nonionella bradii, Pullenia bulloides, and Trifarina angulosa. Planktonic foraminifers were represented by Neogloboquadrina pachyderma.
A similar approach was intended for the agglutinated species. Handpicked specimens were dissolved with HF, however no linings were retrieved, presumably due to loss during decanting.
Linings in Holocene sediments
Backup samples of core GC15 from the Palmer Deep basin I were selected for
Epoxy Resin treatment. Samples of this core were investigated for foraminiferal assemblages 18 months earlier by the author (For results see chapter 3), so that direct qualitative and quantitative comparison between linings encountered in Epoxy Resin and mineral tests from previous microfossil processing was possible.
101 For a reconnaissance study, backup samples of cores JPC28 from the Gerlache
Strait, ODP site 1099 from Palmer Deep basin IH, and ODP site 1098 from basin 1 1098, were grouped into composite samples (Fig. 3.1) and treated with HF as outlined above.
The composite samples were defined based on observations from the foraminiferal assemblages from previous microfossil processing. The treatment of many samples together as composites was necessary for two reasons; the number of foraminiferal tests and their linings is generally low in sediments from the study area, 5-10 cc were usually necessary to gain sufficient numbers, and the backup samples rarely exceeded 0.5 cc in volume. HF treatment is time consuming, it was therefore decided to process the samples of one section together for a thorough qualitative study.
Two sections were selected from core JPC28. The upper (JPC28-S1, fig. 3.1) contains few or no calcareous foraminifers (Rotaliina, fig. 3.1). The lower unit (JPC28-
S2, fig. 3.1) is rich in calcareous foraminifers. The purpose here was to evaluate whether those sections differ in their lining assemblage content. In 1099 the upper 11m show high frequency fluctuations of calcareous foraminifers (Rotaliina), whereby low values might be caused by partial calcite dissolution. If that is the case, linings of calcareous species may be more abundant.
The turbidite T1 of core 1098 is almost devoid of foraminifer mineral tests, and only a few small specimens of T. intermedia and juvenile tests of other species were observed. The composite sample of turbidite T1 was used as a case study to determine whether linings survive redeposition in mudflows.
102 JPC 28 1099 1098 Gerlache Strait Palmer Deep basin HI Palmer Deep basin 1
Rotaliina Rotaliina Rotaliina ro/ fo/. fo/
0 20 40 60 80 100 0 20 40 60 SO 100 0 20 40 60 80 100
21 O JPC28-S1
23 - 10 -
12 - 24 - 1099-Sl a . 14 - 1098-Sl -§ 25 - JPC28-S2 16 -
I 18 - 26 - Turbidite TI 20 - 27 - 10 - 22 -
24 - 28 -
12 - 26 - 29 - 28 -
14 -* 30 -J 30 ->
Figure 3.1. Percentages of Rotaliina (Calcareous taxa) in cores JPC28 from the Gerlache Strait, 1099 from Palmer Deep basin El, and 1098 from basin 1, and composite samples (S) selected for HF treatment. Lines have been smoothed by four-point average.
103 3.6. Results
Taxonomy
Most calcareous species listed above yielded acid resistant remains after removing the shells with 1% HCl applied by a fine brush. However, most of those remains were found to be much thinner than earlier described linings. Recovery of preserved chambers or original chamber arrangement was thus rarely possible. Acid resistant remains of B. aculeata and P. bulloides disintegrated during décalcification to unidentifiable amorphous matter (Fig. 3.2, 1-2). In some cases, remains of B. pseudopunctata and F. fusiformis resembled the calcareous form (Fig. 3.2, 3-4). From one species, N. iridea, a single, small (-25 pm diameter) lining was recovered. None of these thin linings were found in either the wet sieving (Epoxy Resin) or the HF processing, and it is assumed that stirring or sieving led to the complete destruction.
Only one calcareous species, C. lobatulus, yielded Linings with the "usual" size and thickness necessary to withstand processing. Calcareous tests of C. lobatulus are plano-convex trochospiral and the linings of this species bear a clear morphological similarity to the intact test (Fig. 3.3,1-2).
Linings recovered from chemical removal of the calcareous test revealed dimorphism in C. lobatulus. The large microspheric form is characterized by a small proloculus, high breadth and triangular shape of chambers (Fig. 3.3, 1,7). The small megalospheric form has a characteristic large, ball shaped proloculus (Fig. 3.4, 1,3,5-6).
The terms megalospheric and microspheric refer to the size of the proloculus, not the size of the entire test (Goldstein, 1999).
104 Linings from both varieties of C. lobatulus have pores on the apertural side (Fig.
3.3, 7; 3.4, 3-4) and resemble the calcareous test (Fig. 3.3, 6). The size of linings from C. lobatulus varied from an estimated 60-200 pm diameter, and megalospheric forms appeared to be generally smaller than their microspheric counterparts. Linings of C. lobatulus were found mostly with open spacing between chambers, with spacing in the microspheric linings even wider than in the megalospheric forms (Fig. 3.3, 3-4).
Of the numerous agglutinated species observed in surface samples, only T. intermedia yielded linings. One single lining of S. biformis is not discussed at this point.
Tests of T. intermedia are plano-convex trochospiral, but of lesser breath than C. lobatulus, and can be mistaken for planispiral if only one side is investigated (Fig. 3.5, 1).
Linings of T. intermedia were generally found with closed spacing between chambers when embedded in epoxy, whereas linings floating in alcohol were encountered with open spacing. Presumably, the desiccation of the alcohol causes the linings of T. intermedia to contract.
The influence of the lining on the stability of the outer agglutinated layer of T. intermedia was evident. A specimen prepared for SEM analysis showed a broken rim inside the first whorl (Fig. 3.5, 4), or partially deflated chambers (Fig. 3.6, 1-2), presumably due to the deflation of the lining in vacuum. Some linings of T. intermedia showed little dimple-like impressions on the lining wall which mark the position of attached agglutinated material (Fig. 3.5, 3-4) or framboidal pyrite crystals inside the chambers (Fig. 3.5, 1).
105 i..^ % A... F T ' 100 |im ^-•, .. lôûiint..
100 nm "< J' 100 um
Figure 3.2. 1-5: Acid resistant remains of calcareous foraminifers. 1, B. aciileaiea; 2, P. bulloides-, 3, B. pseudopunctata-, 4, left: F. fusiformis-, right: C. lobatulus (megalospheric); 5, N. iridea. Palmer Deep basin I, G21. 6: S. biformis. Palmer Deep basin I, GC15 (1.85m).
106 100 iim
200 um
Figure 3.3. 1, 3-5, 7: C. lobatulus microspheric linings, Gerlache Strait, JPC28 lower section. 2, 6: C. lobatulus calcareous tests; 2, Bismark Strait, G58, outer shell partially dissolved; 6, Andvord drift, G68, note the pores at the apertural side.
107 10
Figure 3.4. I, 3-6: C. lobatulus linings (megalospheric); Gerlache Strait, JPC 28, lower interval; 2, apertural view, 3, detail section of 2. 2: T. intermedia lining, Gerlache Strait, JPC 28, lower interval
108 Figure 3.5. 1-2: T. intermedia, apertural view. 1, lining with pyrite firamboids in the last three chambers; 2, agglutinated test. 3-6: T. intermedia, dorsal view. 3, lining with damaged final chamber; 4, agglutinated test with broken rim; 5, translucent agglutinated test with visible lining; 6, outer shell removed with HF. 1,2,5-6: Gerlache Strait, JPC28 upper interval; 2,4: Palmer Deep basin I, 1098b (18.67 mbsf)
109 Figure 3.6. 1-2: T. intermedia agglutinated test. I, apertural side view; 2, detail section of 1 showing exposed lining. 3: T. intermedia lining with impressions of inorganic test material on lining. Palmer Deep basin I, 1098b (18.67 mbsf).
110 The three major types of linings were identified by their shape, diameter, diameter/breath ratio, and chamber spacing (Table 3.2). Linings of C. lobatulus
(microspheric) are large when complete (-200 pm) and always found with open spacing between individual chambers. C. lobatulus (megalospheric) are smaller (—125 pm), with a very characteristic, large rounded proloculus, and closer spacing between chambers. T. intermedia linings are even smaller (-80 pm), with closed space between individual chambers, numerous chambers and the highest diameter/breath ratio. A further distinction can be made with the aid of the SEM, which shows the pores on the apertural side of C. lobatulus.
C. lobatulus C. lobatulus T. intermedia microspheric megalospheric (undifferentiated)
morphotype plano-convex plano-convex plano-convex trochospiral trochospiral trochospiral
max diameter (am) 250 125 80 max breath (um) 60 80 10 diameter/breath ratio 4.2 1.6 8 max # of chambers 10 14 19
chamber spacing open, chambers mostly open mostly closed often crumbled, defragmented units abundant
Table 3.2. Characteristics of the three types of linings encountered in this study. Note that diameter, breath, and # of chamber are estimates and not based on statistically proven data. It is suggested that C. lobatulus and T. intermedia can be distinguished from each other by these parameters. I ll Linings in Holocene sediments
Retrieved by wet sieving (Epoxy Resin)
Counts of T. intermedia and C. lobatulus tests and linings of core GC15 from
Palmer Deep Basin I are shown in figure 3.2. The foraminiferal test counts are from previous foraminiferal processing. The lining counts were derived from wet sieving and subsequent Epoxy Resin treatment of backup samples. It has to be pointed out that couints from Epoxy Resin may not be quantitatively precise, since large diatoms frustules or clasts may obscure an unverifiable number of linings.
Linings of C. lobatulus (megalo- and microspheric forms) were found in small numbers (<3), thus only the occurences are shown (Fig. 3.7). Calcareous tests o f C. lobatulus were not recovered in GC15, but linings were present in 7 out of 23 samples.
Linings of T. intermedia were more abundant, with a down-core increase below 1.3 m core depth. The correlation between T. intermedia linings and tests was poor in the upper
1.7 m of GCI5, and improved below. A single lining of a previously unknown agglutinated species, S. biformis, was found at 1.85 m core depth.
112 G C 1 5 Palmer Deep basin I
(1000 mbsl) Specimens per cc Occurences 0 5 10 15 N = 23
C. lo b a tu lu s T. in te r m e d ia megalospheric 0.5 - ^ tests C lo b a tu lu s microspheric
9
s. biformis T. in te r m e d ia linings
o'
2.5
Figure 3.7. Number of linings and tests of T. intermedia (per cc), and occurences of C. lobatulus and S. biformis linings in core GC15 from Palmer Deep basin I. Note that linings have been investigated in backup samples. Linings of T. intermedia, present in almost every sample, become more abundant below 1.3 m core depth. C. lobatulus and S. biformis were encountered in very low numbers, thus only the occurences are depicted
113 Retrieved after HF treatment
For a reconnaissance study, backup samples of cores JPC28 from the Gerlache
Strait, 1099 from Palmer Deep basin HI, and 1098 from basin I, were grouped into composite samples (Fig. 3.1.) and treated with the modified HF method. AH three types of foraminiferal linings were found in each interval Table 3.3. shows the occurrence of linings found in the palynological processing, and number of mineral tests after previous microfossfl. processing. C. lobatulus linings were present in samples that did not yield calcareous tests of this species.
Tests Tests Linings Linings Linings CL lobatulus T. intermedia C. lobatulus C. lobatulus T. intermedia megalosptenc miarospiienc
1098-Sl (Tl, 25- 27.5 m) X (N=28) X X X
JPC28-S1 (0-4.48 m) X(N=2) X(N=285) X X X
JPC28-S2 (8.32-13.67m) X (N=12) X (N=524) X X X
1099-Sl (0-15 m) X(N=46) X X X
X = present
Table 3.3. Occurrences of linings and foraminiferal counts of composite samples. Counts of foraminiferal tests were performed on one set of samples. The total number of tests counted in each interval are shown in brackets. Backup samples were treated with HF to investigate the occurrences of linings.
114 3.7. Discussion & Conclusions
Three types of Unings were found in the sediments of the study area. These are clearly distinguishable from each other by their chamber arrangement, number of chambers, size of proloculus, breath and diameter. Megalospheric and microspheric forms of C. lobatulus differ considerably shown by artificial décalcification of handpicked tests revealing that they are the same species. Linings of T. intermedia produced smaller linings with a much higher diameter/breath ratio.
There is an apparent relationship between the lining size and durability. The large microspheric form of C. lobatulus was frequently found with wide spacing between the chambers, and fragments of 1-3 chambers were abundant. The smaller megalospheric form of C. lobatulus exhibited closer spacing between chambers and produced only few fragments. The smallest taxa T. intermedia was almost always present with closed spacing between chambers, and fragments were rare.
The wet sieving Epoxy Resin method proposed here allowed recovery of the species described above for qualitative purposes. Linings from C. lobatulus were retrieved from backup samples of core GC15, although no calcareous tests of this species were found in split samples. The presence of a previously undiscovered lining of the species S. biformis in one of the Epoxy Resin samples indicates the potential of this method for a more complete recovery of lining assemblages.
115 A quantitative analysis of the HF treated samples was not attempted at this time.
The HF treatment yielded the identified lining-bearing species in all intervals. All three
types of linings were present in the turbidite of 1098. This might indicate that linings
survive redeposition during mudflows. Alternatively, linings might have been transported
with the test, undergone diagenetic dissolution with only linings surviving. The two
intervals of JPC28 were not distinguishable on the base of the qualitative analysis of the
lining assemblages. All three types of hnings were present in the upper (few calcareous
foraminifers), and in the lower composite sample (abundant calcareous specimens). A quantitative analysis may be used to characterize the samples. Tests ofT. intermedia, for
instance, were more abundant in the lower (N=524) than in the upper interval (N=285) of
JPC28, and it is expected that the linings of T. intermedia show a similar relationship.
The comparatively high numbers of T. intermedia in most Holocene samples from
the study area highlights the potential use of linings as proxies for paleoproductivity and for radiocarbon dating.
116 C H A P T E R 4
BIOMINERALIZATION IN FORAMINIFERS
4.1. Summary
S canning electron microscope (SE M ) interfaced with an energy dispersive X-ray spectrometer (ED S) was used for investigations of external wall composition. The results revealed that iron content is one of the essential factors determining the resistance of agglutinated foraminifers towards postmortem disintegration (preservation potential).
Iron in tests of agglutinated foraminifers is progressively lost after the death of the specimen, resulting in loss of strength, and in case of Haplophragmoides sp., total disintegration. M. arenacea does not incorporate iron bearing minerals into its shell, providing further evidence that certain foramioifers can select and precipitate specific wall material It also suggests that the absence of iron in tests of M. arenacea is responsible for its outstanding preservation potential in Holocene sediments from the study area.
117 4.2. Introduction
Agglutinated foraminifers
Geochemical information preserved in the fossil tests of foraminifera has been frequently used for paleoenvironmental studies. Agglutinated foraminifers have been largely ignored in comparison to their calcareous counterparts, due to the difiBculties inherent in studying their tests. Since the first major work by Hedley (1963) little has been done until recently in studying biominerahzation of agglutinated foraminifers.
Scanning electron microscope (SEM) interfaced with an energy dispersive X-ray spectrometer (EDS) provides the micropaleontologist with a reliable and fast chemical analysis during the imaging of specimens (Commeau et al., 1985; Bertram & Cown,
1998, AHen et at., 1999). Evidence derived from these investigation support the long
standing assumption that certain agglutinated foraminifers are able to select specific wall material (grains, cement) (Allen et aL, 1999).
Agglutinated foraminifers cement grains onto an organic layer to form their test wall The grains integrated into the test are composed of material available in the local environment, such as detridal minerals, clays, and siliceous and calcareous fossils.
Cements may be composed of organic materials, calcite, silica and ferruginous material
Mineralization of the organic cement of calcium and iron is known m agglutinating foraminifers (Hedley, 1963; Murray, 1973; Bertram & Cowen, 1998). Only foraminiferal tests that are stable in their chemical environment wfll become part of the fossil record.
Umraveling the factors that influence the test stability of agglutinated foraminifers is therefore crucial
118 Towe (1967) found that the ferruginous material in the cement of
Haplophragmoides canariensis is art extremely fine-grained, amorphous oxide. It was noted that the tests of agglutinated foraminifers lose strength during the artificial removal of iron. Furthermore, Towe obserrved that specimens of white coloration of H. canariensis are less resistant towards disintegration than tests with a red coloration and concluded that the organic cement naay undergo a biochemical change during ontogeny resulting in durable “red” individuals.
Specimens collected firom modem surface samples firom the study area depicted a sim ilar relation between test coloration and stability (Fig. 4.1). The uppermost 2 sediment centimeter are occupied by diverse living agglutinated assemblages. Most specimens showed a bright orange brown to red. brown coloration. The first specimens of gray-white coloration occurred few centimeters below the sediment surface. It is hypothesized that the red brown coloration is caused by iron bearing minerals in the outer wall, and that the color change indicates a loss of iron,, referred to as “bleaching” in the following. Deeper in the sediment, diversity and abundances of agglutinated assemblages diminished and partially disintegrated gray-white specimens or specimens without the outer wall appeared. The first firamboidal (raspberry-like) pyrite crystals occurred few a centimeters below this level Assemblages found within and below this interval are greatly reduced in diversity and abundance, disintegrated specimens were abundant, and tests with red- brown coloration rare. The fossil agglutinated assemblages finally are reduced to only M. arenacea and T. intermedia.
119 Core depth (cm)
0 q red-brown color o f livings test high diversity and abundances ©
4 - first disintegration features bleached tests 6 - decline in diversity and abundances
8 - Sulfate Reduction Zone 2 CHjO + SO / •+ 2 H* = > H,S + 2 CO, + 2 H,0 2 FeO(OH) + 2 H,S = > FeS, -f- 2 H,0 + Fe" * + 2 Off ; 10
most tests are bleached 12 outer wall abundantly missing broken tests abundant drastically reduced diversity and abundances 14 first occurence o f framboidal pyrite
16 -
fossil assemblages reduced to M. arenacea and 71 intermedia
Figure 4.1. Schematic in situ disintegration model of agglutinated foraminifers in surface samples from the study area. Note that red brown specimens are abundant and diverse near the surface, and decline down core. The disintegration processes are thought to occur above and within the sulfate reduction zone. Iron oxides, presumably used by agglutinated foraminifers as cement and outer wall material, are converted to ironsulfides, resulting in bleaching and destruction of the agglutinated tests. The sulfate reduction zone is positioned in variable sediment depths in the study area, indicated by the occurrence of framboidal pyrite crystals.
120 Based on their resistance towards postmortem disintegration, three groups of modem agglutinated foraminifers were defined (Chapter 2). The first group is abundant and diverse in the uppermost sediment centimeter, and is characterized by a red-brown coloration of the test, presumably due to ferruginous constituents in the outer wall It was observed that those forms rapidly disintegrate down core. A typical example for the first group is Haplophragmoides sp., which is investigated in this study. The second group consists of T. intermedia, which shows a similar red brown coloration when living and abundant bleaching features in dead specimens. Unlike the first group, T. intermedia is found in Holocene sediments (see chapter 5-6), illustrating that this species has a much higher resistance towards postmortem disintegration. Another species in Holocene sediments is M. arenacea, which differs by showing a bright white coloration in living and dead specimens. The white coloration is thought to indicate a lack of iron in its outer wall Hedley (1963) noted, however that coloration of agglutinated tests may not be a guide to its ferragiuous nature, but his assumption was based on qualitative analysis using
Prussian Blue.
It is postulated that the coloration of agglutinated tests is connected to the iron content of certain agglutinated foraminifers, and that their stability is weakened by the postmortem removal of the iron. The hypothesis was tested by measuring iron contents of the agglutinated outer walls of Haplophragmoides sp., T. intermedia, and M. arenacea.
Quantifying of the iron contents of specimens of different coloration and preservation by
EDS analysis evaluated whether a relation between test, color, iron content and stabflity existed.
121 Calcareous foraminifers
The mineral composition of calcareous foraminifer tests can by modified by environmental conditions during life. The most established paleoclimate proxy for the last 500 ky is derived from the oxygen isotopic composition (^*0) of deep-sea benthic foraminifers. The values of marine carbonates however are controlled by both water temperature and continental ice voltune. We are therefore in need of independent temperature proxies to extract the global ice budget from the deep-sea record.
Magnesium is one of the main cation constituents of seawater; the Mg/Ca ratio is thought to be constant both in the water column and during the last 500 ky (Broecker & Peng,
1982). Chave (1954) showed that the magnesium content of the biomineralized calcite of foraminifers was positively correlated with ambient water temperature. Mitsuguchi et al.
(1996) pointed out that temperature may be one of the primary factors affecting coral
Mg/Ca ratios. Mg/Ca ratios of planktic foraminifers demonstrate great promise in reconstructing past surface water temperatures (e.g. Hastings et at. 1998) as well
However, only a limited number of studies of Mg/Ca ratios have been conducted on benthic foraminifers. The Mg uptake of foraminifers into their shells is assumed consistent within a taxonomic family (Blackmon & Todd, 1959). Izuka (1988) proved a positive correlation between water temperature and Mg/Ca ratios of benthic foraminifers using microprobe analysis.
Certain species were selected for EDS analysis of Mg/Ca ratios based upon their utility as paleoceanographic indicators. B. aculeata was reported to be linked to the
Circumpolar Deep Water (CDW) (Ishman & Domack, 1994). Fursenkoina fusiformis thrives in the realm of the WSTW (Ishman & Domack, 1994). WSTW and CDW are
122 characterized by differences in water temperature and, to a lesser degree, salinity. By measuring the Mg/Ca ratios of living B. aculeata and F. fusiformis tests it was tested whether a correlation between ambient water temperatures and Mg/Ca ratios exist.
Holocene specimens were used for a determination of the prevalent water masses during the early Holocene in the Palmer Deep basin I.
4.3. Material and Methods
Specimens from modem surface samples were collected during the LGM98/2 cruise from the Palmer Deep basins. Samples were stained with Rose Bengal for recognition of living benthic foraminifers. Stained tests are labeled as “living” and unstained specimens are presumed to have been “dead” at the time of sampling.
Specimens of three agglutinated species were selected for elemental analysis.
Haplophragmoides sp. is a typical species of the rapidly disintegrating group. T. intermedia, also with red brown test, depicted no apparent down core disintegration pattern (chapter 5,6). The same is true for M. arenacea, whose bright white tests appeared resistant as well
Three specimens of both Haplophragmoides sp. and T. intermedia were selected from the surface samples, a living specimen, and two more specimens with varying degrees of alteration. Three specimens of M. arenacea were selected, one living and one dead test from the surface samples, and one fossil specimen from ODP core 1098b (22.6 m core depth). The latter was selected because of hints of partial carbonate dissolution in
123 the mid-part of core 1098b (see chapter 5). Evidence for the ability of certain agglutinated species to secrete carbonate cement exists (Bender & Hemleben, 1988). If
M. arenacea precipitates carbonate cement, the specimen from the dissolution interval should show less calcium than the living specimen.
Specimens of B. aculeata and F. fusiformis were chosen for the purpose of evaluating Mg/Ca ratios. One living specimen each of B. aculeata from Palm er Deep basin I and of F. fusiformis of Andvord drift have been selected since those sites are bathed in CDW and WSTW, respectively. An additional two specimens of B. aculeata were chosen from core GC15 of P alm er Deep basin I (1.3 and 1.55 m core depth) for evaluating fossil Mg/Ca ratios.
Samples were placed in a scanning electron microscope (SEM) interfaced to an energy dispersive X-ray fluorescence spectrometer (EDS). The chamber wall components were analyzed for elemental composition by EDS. The light element detector used permitted detection of elements with atomic number greater than 4 at concentrations greater than approximately 0.05 weight percent. After some experimental runs, a collection spot size of 20 x 20 pm was selected. Weight and atomic percent of detected elements were calculated by using the Windows software procedure INC A 3.1. Carbon could not be identified, since the samples were carbon coated.
124 4.4. Results
Iron content o f ag^lutinatinp foraminifers
Test coloration of the selected agglutinated foraminifers was examined by using a wild binocular microscope.
Living specimens
Living specimens from the uppermost sediment centimeter were preserved in alcohol solution and recognized by staining with Rose Bengal (see chapter 2). T. intermedia and Haplophragmoides sp. have living tests which are orange brown to red brown. T. intermedia is smoothly finished and fine grained on the umbilical side, and comparatively coarsely agglutinated on the spiral side (Fig. 4.2, bottom). The last formed chamber of T. intermedia is completely white, indicating the absence of ferruginous constituents in this part of the test. The outer wall of Haplophragmoides sp. is smoothly finished and extremely fine-grained (Fig. 4.2, middle). The artificial breakup of selected tests revealed that the bright brown coloration of T. intermedia and Haplophragmoides sp. is clearly restricted to the outer waDL Af. arenacea is smoothly finished and has a finely agglutinated bright white test (Fig. 4.2, top). The artificial breakup o f selected tests did not reveal changes in coloration. Additionally, the artificial breakup revealed that tests of aU three species have a similar strength of the test.
125 M.arenacea
600 nm
Haplophragmoides
spectrum
T intermedia
Spectrum 1
Figure 4.2. SEM images of M. arenacea, Haplophragmoides sp., and T. intermedia, and examples of spectra derived by energy dispersive X-ray spectrometer (EDS). Note that iron content o f M. arenacea was below detection limit (-0.5 MoI/%). 126 Dead specimens
Dead specimens were taken from samples 5-6cm below sediment surface. T. intermedia and Haplophragmoides sp have dead tests that exhibit a dull brown to gray brown coloration, suggesting the loss of ferruginous constituents from the outer wall
Specimens of Haplophragmoides sp are often found in a fragmented state with the outer wall destroyed. Dead tests of M. arenacea did not reveal changes in coloration compared with living ones, and fragments were rare.
EDS analysis
Haplophragmoides sp
The orange brown living specimen of H. canariensis contained 10.04 Mol/% Fe in the outer wall, a dead specimen with gray coloration possessed 2.73 Mol/% Fe (Table
4.1). The iron content of a fragmented specimen that had partially lost its outer wall was close to the detection limit (0.14 Mol/%).
T. intermedia
A similar pattern is evident in T. intermedia. The living specimen has the highest iron content (8.77 Mol/%), whereas dead specimens showed depleted iron values (0.47-
0.09 Mol/% Fe).
127 M. arenacea
Iron was below detection limit in specimens of M. arenacea. Calcium was present in small amoimts in modem tests (0.8-0.82 Mol/%), and slightly lower in the fossil test (0.16 Mol/%).
Mg/Ca ratios of calcareous foraminifers
The Mg content of a living specimen of F. fusiformis was close to the detection limit (0.06 Mol/%, Table 4.1). The Mg content of a living specimen of B. aculeata was almost twice as high (0.11 Mol/%). The Mg/Ca (%o) ratios of living B. aculeata and F. fusiformis are 3.75 and 12.21, respectively. Unexpectedly, Si, Na, and A1 were discovered by the EDS analysis in the calcareous shells as wefl. The Mg values of fossil
B. aculeata were below the detection limit.
4.4. Discussion & conclusions
Outer wall material of agglutinated foraminifers
It should be noted that energy dispersive X-ray analysis (EDS) alone cannot identify the mineral phases present. However, possible mineral constituents of the walls of agglutinated foraminifers may be postulated by evaluating other elements present. The living test of T. intermedia has a red brown outer wall containing oxygen, silica and 8.77
Mol/% Fe, suggesting that an iron oxide may be the reason for the coloration. The other abundant mineral phase is likely quartz, since feldspar cations such as Na, K, Al, or Ca are absent or rare (Table 4.1). The living test of Haplophragmoides sp. also has a fine grained outer wall, orange-brown in coloration, with high iron content (10.04 Mol/%),
128 Agglutinated foramlnlfets
MoI/% Feature analyzed O Si Na A l Ca Fe M g K
Haplophragmoides sp. living 65.42 10.33 0.00 5.89 0.00 10.04 3.89 2 3 4
dead, bleached 72.54 10.90 0.00 8.34 0.00 2.73 3.95 0.00
dead, outer waH gone 74.74 20.89 1.35 1.08 0.62 0.14 0.00 0.15
T. intermedia Eving 64.04 19.21 0.00 0.19 0.00 8.77 0.00 0.30
dead, partly bleached 68.92 17.25 2.60 6.24 2.40 0.47 0.32 0.07
dead, bleached 75.67 16.57 3.48 2.26 032 0.09 0.00 0.07
Af. arenacea Eving 7 4 J 0 17.42 2.30 4.78 0.80 0.00 0.00 0.11
dead 62.02 29.26 1.97 2.55 0.82 0.00 0.00 0.72
fossil 75.80 20.45 1.81 0.63 0.16 0.00 0.00 0.15
Calcareous foraminifers
Mol/% Feature analyzed O Si Na Al Ca Fe M g Mg/Ca (%o)
F. fusiformis (Eving) 83.50 0 3 1 0.00 0.15 15.98 0.00 0.06 3.75
B. aculeata 89.80 0.40 0.39 0.23 9.01 0.00 0.11 1231 living
fossil (GC15, 130cm) Mg below detection Emit
fossil (GC15, 155cm) Mg below detection limit
Table 4.1. EDS analysis of the outer test walls of Haplophragmoides sp., T. intermedia M. arenacea, F. fusiformis, and B. aculeata. Note that Haplophragmoides sp. and T. intermedia have high iron contents in living (8.77-10.04 Mol/%) and low in dead specimens (0.09-2.73 Mol/%). The iron content of Af. arenacea was below the detection lim it.
129 pointing to the presence of an iron oxide as weDL Na and Ca are also absent in
Haplophragmoides sp outer wall, but the presence of Si, K and Al suggests the
occurrence of feldspar or and quartz.
In contrast to red-brown forms, the iron and magnesium contents of living, dead
and fossil M. arenacea (white coloration) were constantly below detection limit (Table
4.1), indicating that this species does not utilize mineral phases of these elements. The
presence of Si, Na, Al and Ca suggests that quartz and feldspar are the main mineral
phases in M. arenacea. The small amounts of Ca may alternatively point to the
occurrence of carbonate, but since the specimens were coated with carbon for SEM
analysis, the element itself could not be measured. Further investigations (e.g. by
microprobe analysis) are needed to identify mineral phases.
In summary, the investigations of the outer walls showed that the investigated
species have affinities to certain elements. M. arenacea does not utilize iron and
magnesium, and likely incorporates quartz and feldspar into its tests. Haplophragmoides
sp. and T. intermedia integrate iron into their tests, in form of a fine-grained outer layer
which covers the outer wall of quartz and feldspar.
The role of iron in the stabilitv of agglutinated tests
Hedley (1963) mentioned for certain agglutinated species that their white terminal chambers are more easily broken than the brown predecessors, and concluded that cementation (of iron?) was incomplete. The results presented in this chapter provide further evidence for the relation between test coloration and stability. The iron content of
130 the outer wall of agglutinated foraminifers is progressively lost after the death of the
specimen, resulting in coloration change from red-brown to gray-brown and loss of
stability. In case of Haplophragmoides sp. total disintegration is the result.
T. intermedia loses its iron as well, but retains durability, as indicated by abundant
tests in Holocene sediments (see chapter 5-6). Apparently, in case of T. intermedia, other
factors play a role. Most likely the possession of a thick internal organic lining (see
chapter 3) stabilizes and preserves the test. Af. arenacea on the other hand does not
incorporate iron into its shell and is thus less susceptible to disintegration processes.
Another factor influencing preservation potential includes the mechanical strength
of tests, but the artificial breakup did not reveal major differences between Af. arenacea,
Haplophragmoides sp., and T. intermedia. Iron content is therefore recognized as one of
the essential factors determining the resistance of agglutinated foraminifers to postmortem disintegration.
Iron in agglutinated tests: possible paleoenvironmental applications
r . intermedia is one of the most abundant Foraminifers in Holocene samples from the study area, present even in intervals where no other taxa, especially calcareous, occur
(chapter 5,6). Dissolution of calcareous fossils may be a serious concern (e.g. Corliss &
Henjo, 1981), and proxies for evaluating its extent are therefore needed. By measuring the iron content of T. intermedia, information about past acidity in the pore water might be obtained. Under current conditions, most of the iron of T. intermedia is lost after the death o f the specimen, and signs o f dissolution in calcareous foraminifers are abundant, presumably caused by a pH of -7.8 in the pore water.
131 The solubility of iron is considerable higher at pH’s lower than 8.5. A working
hypothesis for future studies is that during times of low pH’s and enhanced calcite
dissolution in the pore water, less iron is retained in tests of T. intermedia. Conversely,
during times of higher pH’s and enhanced calcite preservation conditions in the pore
water, higher remaining iron contents are to be expected. Using this assumed
relationship, it may be possible to clarify the mid-Holocene of the Palmer Deep basin I
record, where the absence of calcareous foraminifers might be interpreted as due to
intense calcite dissolution.
The incorporation of iron into agglutinated tests may also depend on biological
factors. There is considerable interest in the biochemistry cycling of iron in the world’s
oceans (Johnson et al., 1997; Wells et at., 1995). Iron plays an important role in
controlling primary productivity under certain circumstances (e.g. Gerringa et at., 2000).
Future studies of the iron uptake by benthic foraminifers in relation to primary
productivity and water chemistry may provide valuable insights in the biochemistry
cycling of iron.
Mg/Ca ratios of calcareous foraminifers
The results on temperature related incorporation of Mg into the test of F. fusiformis and B. aculeata are inconclusive at this time. Although surface specimens have
somewhat higher Mg contents than the fossil ones, the overall small amounts and large fluctuations of other constituents prevented any definite conclusions being made.
132 The calculated Mg/Ca ratios are similar to those published from other benthic species (Rathbum & De deckker, 1997). However, the presence of Si, Na, and Al indicated that the living tests were presumably contaminated by clay minerals, thus the observed Mg may be due to contamination as well If that be the case, the residual Mg contents would be likely below detection limit of the EDS method. The originally desired investigation via microprobe, which allows a lower detection limit, could not be carried out at the time due to hardware problems associated with the OSU microprobe.
133 CHAPTERS
THE HOLOCENE OF THE PALMER DEEP BASINS
5.1. Summary
A 12.8 ky long foraminiferal profile from the Palmer Deep records high
frequency fluctuations in paleoenvironmental conditions along the western Antarctic
Peninsula. Benthic foraminiferal assemblages are used as proxies to reconstruct deep-
water mass distribution and climate change during the Holocene in the Palmer Deep.
Alternating dominance of Bulimina aculeata, which indicates upwelling of
Circumpolar Deep Water (CDW) and open-marine conditions during the Austral
summer, and Miliammina arenacea, adapted to the Saline Shelf Waters (SSW) is noted
during the last 3.5ky. The mid-Holocene (3.5 - 9 Iqr BP) is characterized by the
dom inance of the SSW indicator Miliammina arenacea, which may be due to the
persistence of this water mass, or alternatively, to partial dissolution of the calcareous
foraminifers. The existence of a warmer mid-Holocene in the study area (Domack et aL,
in press, Taylor & Sjurmeskog, submitted) caimot unequivocally be confirmed or refuted
from the foraminiferal data at this point, due to uncertainties in age control or dissolution processes during the mid-Holocene.
134 The Younger Dryas (YD) and early Holocene are characterized by rapid faunal turnovers of the benthic assemblages. Comparison of the Palmer Basin oceanographic record with Greenland ice core data shows that a coimection with the North Atlantic thermohaline circulation is likely. In this scenario, the onset of the Yoimger Dryas is caused by a shut down of the deep-water circulation in the North Atlantic. The resulting elevated heat transport to the Southern Hemisphere is followed by the final disintegration of the ice shelf over the study area and the first occurrence of benthic foraminifers in the
Palmer Deep. After the termination of the YD, the deep-water circulation in the world’s oceans intensified and the upweDing of nutrient rich deep water triggered the first occurrence of diverse benthic assemblages in the Palmer Deep.
5.2. Introduction
Debate continues on the Holocene climatic history (e.g. Dansgaard et al., 1993;
Broecker, 1999). The mid-Holocene climatic optimum, Neoglacial and Yoimger Dryas are periods of significant climatic change during the last 13 ky in the Northern
Hemisphere, but their recognition remain controversial in Antarctica (e.g. Ingolfsson et a l, 1998; Blunier et a i, 1998). The timing of the onset of deglaciation in the Antarctic
Peninsula is not well known.
Previous studies suggested that the early stages of deglaciation were controlled by global sea-level rise (Ingolfeson et at., 1998). It was suggested that the ice retreated firom the inner continental shelf shortly before 11 ky BP (Pudsey et at., 1994). The deglaciation of many inner continental shelf areas was presumably considerably delayed (Ingolfeson
135 & Hjort, 1999). Déglaciation ages are range from 4.5 ky BP on James Ross Island (Hjort
et al., 1997), post-5.3 ky BP on Brabant Island (Hanson & Flint, 1989), and 6 ky BP on
Alexander Island (Clapperton & Sudgen, 1982). Ingolfrson et al. (1998) proposed a
drcmnh-Antarctic glacial readvance centered around 5-6 ky BP.
Also in debate are bipolar climate linkages during the Holocene. Hjort et al.
(1998) conclude that the deglaciation process in Antarctica was largely out of phase with
the Northern Hemisphere. They proposed a climatic optimum around 3-4 ky BP in
Antarctica, much later than in the Northern Hemisphere, and suggest a causal connection
with the Milankovitch insolation maximum for the southern latitudes. Stocker (1998)
provided evidence for a bipolar see-saw effect during the YD, when extremely cold
conditions in the Northern Hemisphere were accompanied with steady warming in
Antarctica. Domack & Leg 178 Scientific Party (1998) and Taylor et al. (1998), however,
identified climatic events such as the mid-Holocene climatic optimum, and the Little Ice
Age (LIA) in the Antarctic Peninsula, sim ilar to the those observed in the Northern
Hemisphere.
The Antarctic Peninsula was recognized as an important area for studying past climatic fluctuations because of its close proximity to the Antarctic Convergence and its polar to sub-polar climatic gradient (Domack & Ishman, 1993; Domack et al., 1995;
Domack & Me Clennen, 1996; Kirby et al., 1998). The sediments that accumulated since the Last Glacial Maximum (LGM) on the Peninsula’s continental shelf and m Qords indicate development of glaciers, and paleocHmate evolution during the Holocene
(Domack etal., 1991; 1993; Pudsey era/., 1994; Leventer era/., 1996; Kirby era/., 1998).
Previous research focused on the outer continental shelf (Pudsey et al., 1994; Latter &
136 Vanneste, 1995) and Çords (Domack et al., 1993; SheveneH et al., 1996). Little work has been done in environmental settings that mark an intermediary position between the full glacial conditions o f the shelf edge grounding line and interglacial conditions at the Qord heads.
One such setting is the Palm er Deep, where relatively thick Holocene sediment accumulations (-50-250 m) were recently discovered (e.g. Leventer et a i, 1996; Kirby et al., 1998, Rebesco et al., 1998). Previous studies in the Palmer Deep, based on short records (< 12 m), demonstrated a climatic optimum before 2.5 ky BP (Leventer et al.,
1996, Kirby et al., 1998). Recent studies described late Pleistocene to Holocene climate variability in the Antarctic Peninsula firom ODP Leg 178 site 1098 (Palmer Deep, Fig.
5.1) using diatoms, mass accumulation rates, and magnetic susceptibility as proxies for paleoproductivity (Sjimneskog & Taylor, submitted; Taylor & Sjurmeskog, submitted;
Domack et al., in press, Brachfeld et al., submitted). Four preliminary climatic zones in the Palmer were identified firom site 1098 (Fig. 5.2). A “deglaciation phase” (-13.2-11.5 ky BP) was deposited during glacial retreat at the end of the regional Last Glacial
Maximum, and is characterized by extremely high diatom abundances and high and variable mass accumulation rates (Taylor & Sjurmeskog, submitted; Domack et al., in press). A cold “climatic reversal” (11.5-9.0 ky BP) was recognized by enhanced ice rafted debris content of the sediments (Domack et al., in press), whereas diatom data point to higher primary production in the Palmer Deep than today during this period
(Taylor & Sjurmeskog, submitted). The mid-Holocene “climatic optimum” (9.0-3.7 ky
BP) was characterized by an open water diatom assemblage (Taylor & Sjurmeskog,
137 Palmer Deep basins
; ''8 0 0 : 600
64° 3 0 ’ W 64° 20’ W 64° 10’ W
Figure 5.1. Bathymetric map of the study area. Position of surface samples (small gray dots) and ODP sites 1098 and 1099 are indicated. Map after Leventeret al. (1 9 9 6 ).
138 Palmer Deep R o ss S e a Lallermand Fjord Livingstone gigqy island J a m e s diatom - sediment Terra Nova Bay/Vlctorla South Georgia Diatoms - sediment Island R o ss Land Island 0 L ow ered N eoglaclal Transition to M axim um Less stable D ecline of Amelioration Cooling, Humid Cooling 500 -I produclivily colder se a -lc e conditions penguin Cold, Instability warm, less 1000 conditions rookeries continental than optlmu O ptim um , 1500 - Sen ice dintom C old a n d high assciiiblngc arid 2000 - productivity 2500 3000 - Warm, high 3500 - P enguin O ptim um H um id? O ptim um TOC High diatom Cool H um id a n d optim um 4000 Open water abundance, w arm ; 4500 optim um 11 melting of Cold dry O ptim um II se a -lc e Continuous 5000 Cold and dry L ow er presence of 5500 produclivily Slightly p e n g u in s ™ 6000 - colder O ptim um Mid-Holoceiic E xtensive OJ ^ 6500 - VO optim um I se a -lc e cover, " i 7000 Open water Time O) variable dim 2 7500 diatom Optimum transgressive O 8000 - assem blage déglaciation 8500
9000 - Ice breakup Clim atic 9500 R ev ersal 10000 - 10500 - 11000 O ld est 11500 4 a b a n d o n e d 12000 ro o k eries 12500 Melting
13000 ■ Déglaciation 13500 - Figure 5. 2. Synthesis of the Antarctic Peninsula glacial development and associated 14000 - environmental changes since the Last Glacial Maximum. From Taylor & Sjunneskog (subm.). submitted), enhanced mass accumulation rates, reduced ice rated debris, and very low magnetic susceptibility (Domack et al., in press, Brachfeld et at., submitted). In the
“Neoglacial” (late Holocene, <3.7 kyr BP) climatic cooling was inferred by a reduced
diatom productivity (Sjunneskog & Taylor, submitted), greater concentrations of ice rafted debris (Domack et al., in press) and high and variable magnetic susceptibility
(Brachfeld et al., in press). Diatom assemblage analysis however suggested early seasonal warmth between 4.4 ky BP and 1.8 ky BP (Taylor & Sjunneskog, submitted).
The use of planktic (living in surface waters) diatom abundances as paleoclimatic indicators is based “on the simphfied view that warm, stable surface water, which often forms as a result of sea ice melt, (Estrada & Delgado, 1990), produces an environment suitable for diatom blooms” (Sjunneskog & Taylor, submitted). It was therefore concluded that diatom abundance in the sediment could be used as a projQ^ for marine primary productivity (Scherer et al., 1992). However, this simple model does not take the influence of oceanic currents on the deposition of planktic diatoms on the sea floor into account. Diatom shells (fiiistules) are easily transported by ocean currents, the presence in some terrestrial settings indicated that even aerial transport is possible.
High mass accumulation rates (Domack et al., in press) during the mid-Holocene were interpreted as due to a climatic optimum with enhanced biogenic productivity. Low mass accumulation rates were thought to indicate low productivity due to “Neoglacial” conditions (Domack et al., in press). In Antarctic waters, however, biogenic silica derived from org anism s such as diatoms is a major constituent of marine sediments (<75%,
Gersonde & Wefer, 1987). It is likely that mass accumulation rates in the area are mainly determined by the productivity of diatoms and other primary producers.
140 The late Holocene fluctuations of the magnetic susceptibility (MS) in cores from
the study area are also thought to be m ainly due to periodic (~ 200 year cycles) diatom
blooms (Leventer et al., 1996; Kirby et at., 1998). Strong winds and/or storms prevent
stratification of the upper 100 m of the water column, causing relatively low primary
productivity and dominance of terrigenous sedimentation (Fig. 5.3). MS lows are thought
to be produced by thermal wanning, which leads to weaker winds and increased melting
of sea ice. The resulting water column stratification promotes high primary productivity,
which dilutes the magnetic phase in the sediment (Brachfeld & Baneijee, 2000). The
three proxies diatoms, mass accumulation rates, and magnetic susceptibility may be thus
directly dependent of each other and be influenced by the flow regime of bottom water.
Benthic foraminifers on the other hand live within the sediment and are therefore much
less prone to redeposition than diatoms. In this chapter benthic foraminifers were used as
climate proxies to determine deep-water flow and paleoproductivity.
5.3. Objectives
The overall Objective is to establish a high-resolution record of benthic
productivity and paleoceanography using benthic accumulation rates, diversity and
statistical analysis of foraminiferal assemblages. Emphasis will be given on nature and timing of the Holocene climatic optimum in the Antarctic Peninsula.
141 High MS values:
Increased windiness and/or storm frequency Well mixed water column = > Limits Primary Productivity ==> Domination of Terrigenous sedimentation
Magnetic Susceptibilty (cgs X 1 0 ^ 20 30 40 50 60 70 80 90 100
9 8 Q. ■S & 200 years cycle
Low MS values:
Increased meltwater induced water column stratification ==> Diatom blooms = > Enhanced Primary Productivity = > Enhanced Biogenic Silica and Total Organic Carbon Contents
Figure 5.3. Schematic model explaining fluctuations in magnetic susceptibility dining the Late Holocene in the study area. Note the 200 years interval of low primary productivity (Leventer et al. 1996).
142 5.4. Material and Methods
Drilling at site 1098 of ODP LEG 178 from Palmer Deep basin I retrieved three
cores (a/b/c) from 1000 m water depth (Fig. 5.1). Cores a/b/c are each - 45 m long and
used to form a complete post-glacial record and a composite depth scale (Domack et al.,
in press; Acton et at., submitted). Sediments fromi core 1098b consist of alternating
massive muddy diatom oozes, laminated mud-bearing diatom oozes, and diatom-bearing
silty clays and clayey silts with generally low sand comtent (Fig. 5.4, Barker et al., 1999).
Three turbidites (T1-T3) were noted below a core de=pth of 25 m. Though generally rare,
a variety of macro-bioturbation features have been observed. Planolites type burrows are
oriented parallel to bedding, while a few long, open vertical burrows were observed
(Barker et al., 1999). Graded sands and silts associated with structureless intervals above
and slumped material below are interpreted as tmrbidites (Barker et al., 1999). An
increase in coarse clastic material and pebbles at the base of holes 1098 a/c was observed
(Barker et al., 1999), and interpreted as a diamicton representing the Last Glacial
Maximum (Taylor et al., 19989; Domack et al., in press).
Cores 1099 a/b of ODP LEG 178 (1099 hereafter) were retrieved in Palmer Deep
basin DI from 1400 m water depth. Sediments recowered at 1099 consist of alternating
massive muddy diatom oozes, laminated mud-bearing diatom oozes, and diatom-bearing
silty clays and clayey silts with a generally low sand content (Fig. 5.5, Barker et al.,
1999). The sediments from 1099 resemble those of L098 in exhibiting varying intensities
of bioturbation. Steep Fugichnia burrows were made by unknown organisms following the deposition of thin (1 cm) laminations and were intesrpreted as the upward escape
143 ODP Leg 1098 (Palmer Deep basin 10
1098 1098
iO 80 0 40 BO K am i
TEmjo fnbsf'TD 46.7 mbsf
Lan-4r«ited muddy diatom ooze Massive (bioturboted) muddy diatom oozo KWKWrtl Turbidto (muddy tSatom ooze/ datom dayey silt) Terrigenous turbidite Slump in lam'natod sediments Diomiot
Figure 5.4. Lithostratigraphic column for 1098, summarizing lithology and percent biogenic component for 1098A, 1098B, and 1098C. Magnetic susceptibility data are from Hole 1098B. Laminated oozes occur in packets 0.1-2.2 m thick, dominating the sequence from 9-23 mbsf and below 40 mbsf. Massive, bioturbated ooze occurs in units 0.1-1.9 m thick. From Barker et al. (1999).
144 ODP Leg 1099 (Palmer Deep Basin III)
1099A I 1099B Io I oCL CQ Q II
0 so 100 0 5001000 0 SO 100 1000 2000 I J !___ !___ I J L_ _ I I___ 60 ■
1H
7 0 - 2H
80
3H
90 4 ]4 H
40 -t 100 ' 5H
T.D. 107.5 mbsf Diamict Laminated muddy diatom ooze Massive (bioturbated) muddy diatom ooze Turbidite (muddy diatom ooze/ mm diatom clayey silt) Turbidite (sandy/silty base)
Figure 5.5. Lithostratigraphic column for 1099, summarizing lithology, percent biogenic component, and magnetic susceptibility data of 1099A and I099B. Laminated oozes occur in packets 0.1-2.2 m thick and dominate the sequence from 9 to 22 mbsf, between 35 to 40 mbsf, and below 87 mbsf. Massive, bioturbated ooze occurs in units 0.1-19 m thick. From Barker et al. (1999).
145 routes of burrowing organisms (Barker et al., 1999). Graded sands and silts associated
with structureless intervals above and slumped material below are interpreted as
turbidites (Barker etal., 1999).
Sedimentation in basin m was recognized as more affected by mass flow than
basin I (Kirby et al., 1998). Ice-rafted pebbles show two maxima, between 32-35 m and
below 80 m core depth. The former was interpreted as a glacial diamicton of unknown
age. Radiocarbon dating from the upper unit in basin DI (Kirby et al., 1998), suggests
that the base of the diamicton may predate the last glacial maximum.
Depositional processes proposed for include pelagic/hemipelagic settling and
sediment gravity flows from the steep sides of the Palmer Deep basin. The basins act as a
sediment trap, both for biogenic material sinking from the surface waters and for near-
bottom suspended sediment transported by turbidites or mass flows derived from
surrounding shallow water (Barker etal., 1999).
Core 1098 was sampled in 5 cm intervals for foraminiferal faunal analyses. Given
the average sedimentation rate of 0.25 cm yr-1 (Domack et al., 1999) in the Palmer Deep
Basin I, a theoretical time resolution of 20 years between two samples is provided.
Bioturbation effects approximately the upper 10 cm or more of modem samples (see chapter 2), which constantly mixed the sediment and the assemblages. The resolution achieve in this research is therefore around 40 years at best. A gap between 6.03 and 6.86 meters below sea floor (mbsf) in 1098b (Barker et al., 1999) had to be bridged with samples from core 1098c. Samples from the lowermost 2.5 m were taken from 1098c
146 since 1098b did not penetrate the diamicton. The upper 85 m of 1099 were sampled in 20 cm intervals for a reconnaissance study. Core 1099 covers a longer period than the 1098 record if the diamicton in 1099 represents the LGM.
The sediment samples were washed through a 63pm sieve and picked of all foraminifers. To minimize preservation effects due to rapid disintegration of agglutinated tests, the concept of a potential fossil assemblage (e.g. Mackensen et al., 1990) was applied to all foraminiferal proxies calculated in this research (for discussion see chapter
2). Harloff & Mackensen (1997) define this concept as “the best available prediction of the assemblage which remain fossilized from a dead assemblage on Quaternary time scales”. Accordingly, all agglutinated taxa except Af. arenacea and T. intermedia were removed firom the data set. Af. arenacea is known to be resistant against early diagenetic processes (Mackensen et a i, 1993). Little is known about the preservation potential of T. intermedia firom literature. It was incorporated into the data-set since this species proved resistant in surface samples (chapter 2).
To keep the data-set comparable to previous studies firom the Antarctic Peninsula,
Q-mode Principal Component Analyses (PGA) were carried out using a commercially distributed statistics package (SYSTAT TM VIII, 1998). The methods applied followed
Mackensen ef a/. (1990).
Benthic foraminiferal accumulation rates (BFAR) and diversities have been calculated as additional proxies, according to the methods described in chapter 2 of this dissertation.
147 Radiocarbon dating
For the purpose of this study the age model of Domack et al. (in press.) has been applied (Fig. 5.6) to the 1098 record. The sedimentation rates calculated therein range from 0.17-0.34 cm yr'^ for the upper 25 meters (above turbidite XI), 0.61 cm yr'^ between turbidites T1 and T2, 1.02 cm yr'^ between turbidites T2 and T3, and 0.3 cm yr'^ below turbidite T3. The age model developed also shows a loss of 1000 yr at the base of turbidite T2, presumably caused by erosion at the time of turbidity flow (Domack et at., in press.). The ages utilized in this research refer to ages corrected by reservoir effects as described by Domack et al. (in press).
Calcareous foraminifers are frequently used for radiocarbon dating (Andrews et al., 1999). Modem marine carbonates around Antarctica require a 1.2-1.3 ky ocean reservoir correction (Gordon & Harkness, 1992). The ocean reservoir correction in the deep ocean was most likely not a constant during the latest Quaternary (e.g. Broecker et al., 1999), and is dependent on the deep water circulation. Mixed samples of many species are usually used for radiocarbon dating, even though indication exists that radiocarbon ages may differ between coexisting foraminiferal species (Brocker et al.,
1999). The typical Holocene sediment in the Antarctic realm is diatomaceous mud, which generally lacks abundant calcareous foraminifers (Licht et al., 1999). Acid-insoluble organic matter has thus been frequently used for radiocarbon dating, although their reservoir corrections are substantially older than the values of marine carbonates.
Andrews et al. (1999) reported reservoir corrections as large as 22,970 years and concluded that the dating of acid-insoluble organic matter “will have to remain as the last
148 Age (ky BP) 4 6 8 10 12 14 0
5
10 o o 15 CL -0 20
n 25 Turbidite 1
3 0 Turbidite 2 35
4 0 Turbidite 3
4 5 Diamicton
Fig. 5.6. Age model of core 1098b (from Domack et al., in press). Ages given are corrected ages. Note the loss of almost 1000 years at the base of turbidite 2.
149 method o f last resort for the foreseeable future” (p. 214). Such a last resort method was necessary for dating core 1098, due to the general paucity of calcareous foraminifers. AH radiocarbon measurements were performed on acid-insoluble organic matter (Domack et at., in press). The derived timescale may therefore be preliminary and require further adjustments. Dating of organic linings o f foraminifers (for discussion of linings see chapter 3), instead of bulk organic matter, may enhance the precision of the radiocarbon method.
A detailed stratigraphy and age model of 1099 is not available at this time. The preliminary lithostratigraphy of 1099 shown in figure 5.5 is based on observations of the
Leg 178 shipboard party (Barker et at., 1999). Further lithological studies revealed major differences to these first interpretations. For instance, the section between 59-40 mbsf is now interpreted as a muddy turbidite (Domack et al., 1998). An approximate stratigraphy was established by utilizing investigations firom the sand size fraction (>63 pm) of the processed samples. Dry weight highs for the >63 pm fraction in this particular setting are thought to be caused by coarse grained turbidites, and values near zero caused by mud mass flows (Domack et al., 1998). Magnetic susceptibility (MS) data have been used as an approximate time control to correlate 1099 with the well dated 1098 record. Brachfeld
& Baneijee (2000) note that marine sediment cores recovered from the Palmer Deep region show remarkably similar MS profiles.
The transition from high and variable to uniformly low MS was thought to mark the end of the mid-Holocene (Domack et al., in press), and wfll be used as a tie point for the correlation of 1099 to the 1098 record.
150 5.5. Results
Stratigraphy o f core 1099 (Palmer Deen hasin TIT)
An approximate stratigraphy of core 1099 was established by utilizing investigations from the sand size fraction (>63 pm) of the processed samples. The dry weight shows two prominent highs, from 74.8-69.9 m and from 40-32 m core depth, corresponding to similar highs in MS (Fig. 5.7). The >63 pm fraction contains abundant large (>355 pm) clasts in these intervals. The nature of the clast rich intervals is to date unclear. The upper one was presumably deposited during the Last Glacial Maximum
(LGM) (Rebesco et al., 1998, Barker et al., 1999). The lower unit may be a sandy turbidite (Barker et al., 1999). It was suggested that the upper unit may be a turbidite as well (personal communication E. Domack, 2000).
Two intervals of very low dry weight values are present. The upper, ranging from
30-35 m core depth was recognized as a mudflow by Barker et al., (1999). The lower, from 60-43 m core depth was originally described as massive, bioturbated diatom ooze.
Domack et al. (1998) suggested that the lower interval may be a mud flow as well
The upper clast-rich interval at 40-32 m core depth will be interpreted as being deposited during the Last Glacial Maximum in order to establish a preliminary age model for core 1099 from Palmer Deep basin HE. It is furthermore assumed that the upper mud turbidite was an instantaneous geologic event. The removal of the mud turbidite from the
151 1099 Palmer Deep basin m (1400 mbsl)
MS D r y w e ig h t ( x 10"^ cgs) (g) 0.50
3.36 ky BP
Mud Turbidite
Diamicton ? Turbidite ? 2 40
Mud Turbidite
Turbidite ?
L egend I I Diatomaceous mud and ooze » Gypsum GRI Clasts (>355 um) ® MoIIusks
Figure 5.7. SedimentoIogicaL data for core 1099 include dry weight (<63: m), occurrence of clasts (< 355 : m), gypsum and mo Husks. Magnetic susceptibility data (MS) from B arker et al., (1999). Mud turbidites are characterized by low to negligible dry weight, clast rich intervals indicate sandy turbidites or diamictons. The mid-/ late Holocene boundary (data from Domack et al., in press) is indicated by the drop of the MS from high and variable to low and uniform values as suggested by Brachfeld & Baneqee (2000). 152 stratigraphie column wiH thus not cause much loss of time. There may, however, be a hiatus at the bottom caused by mudflow during deposition of the turbidite. A loss of time appears possible between the upper mud turbidite and the assumed diamicton.
A characteristic feature of the MS in marine cores firom the study area is a drop firom high to variable to uniformly low values (Brachfeld & Banerjee, 2(XX)). Domack et al. (in press) suggested that this marks the mid-/ late Holocene transition at 3.36 ky BP in the Palmer Deep. If one applies this hypothesis to the 1099 record of Palmer Deep basin m , the mid-/ late Holocene transition occurred at 9 m core depth (Fig. 5.7).
Consequently, the upper 9 m of 1099 experienced an average sedimentation rate of 0.254 cm/year. The derived sedimentation rate was used to establish an approximate age model for the upper 25 m of 1099.
Occurrences, diversities and BFAR
Palmer Deep basin I
The occurences of foraminifers in core 1098 fi’om Palm er Deep basin I are shown in figure 5.8. Starting at the bottom of the core, the first benthic foraminifers belonging to the species M. arenacea occur at 44.8 m core depth with the assemblages remaining monospecific until 42 m core depth. The section from 28 to 42 m depicts high diversities and abundances.
Above 28 m benthic foraminifers are mostly restricted again to M. arenacea, with a slow recovery of diverse assemblages above 14 m core depth. Judging by the occurences, four groups can be recognized based on their distribution downcore.
153 1098 % ^3 s 23 >3 ^4 % % - a %» 2 ? Palmer Deep % % % S* =£ % 2- % % 5 % s 2 ^ basin I i % I? . f t % % 3" S' 2 i a. GC (1000 mbsl) I % % 5' “^3 *
o "F o 0 a (N = 6 8 7 ) TTîo o 8 o 8 o 8 o O 8 O 8 o o o o
o 8
o o o o 3 -I S. Turbidite TI
5 -I o 8 e 0 § 8 0 o Turbidite T2 O OJbO 0 g o o O 8 o o O § § 8 e L/J 8 0 8 ° O 8 Os O 8 0 oow o § i S 0 o I o 9 Turbidite T3 8 § g g 0 ê o o ai 8o 0
D ia m ic to n
Figure 5.8. Occurrences of foraminifers in core 1098 from Palmer Deep basin I. Turbidite units T l-3 and the diamicton unit are indicated.
154 The agglutinated species M. arenacea and T. intermedia are present in most samples. In contrast, the agglutinated taxa C. subglobosum, Reophax spp., P. eltaninae,
H. parkerae, and Textulariina spp. are confined to the upper 8 m of the core. One calcareous group, consisting of B. aculeata, B. pseudopunctata, N. pachyderma, P. bulloides and A. echolsi is absent in the mid-part of 1098. A second calcareous group is largely confined to the lower part of 1098.
The samples firom cores 1098b/c yielded 13 benthic species after removing all agglutinated taxa with low preservation potential firom the data-set. The remaining species were used for the calculation of the proxies benthic foraminiferal accumulation rates (BFAR) and diversity. Sedimentation rates firom the age model of Domack et al. (in press) were used to calculated BFAR, which are expressed as number of specimens per cm^ky.
Diversity and BFAR of 1098, plotted against the age model, are shown in figure
5.9. From 12.8 to 11.6 ky BP diversity and BFAR are low, followed by high and variable values firom 11.6 to 9 ky BP. The period firom 9 to 3.5 ky BP is characterized by very low diversity, and slowly increasing BFAR. The diversity and BFAR were elevated during the past 3.5 ky, with a maximum occurring arotmd 400 years ago.
Diversity and BFAR seem to have been low during most of the mid-/late
Holocene, compared with modem values firom surface samples (note reference lines in figure 5.7). The high modem values were attained only twice during the Holocene, Le. prior to 9 ky BP and around 0.5 ky BP.
155 1098 Diversity BFAR Palmer Deep basin I (1000 mbsl) (# species) (#cm'^kyr'‘) 0 4 8 12 10 I0000 ' f t t I t t tt t It 1 . t . m (N = 687)
> OQa
1303
10 - Hiatus
12 -
Figure 5.9. Benthic foraminiferal accumulation rates (BFAR) and diversity from the 1098 (Palmer Deep basin I). Thicker black lines indicate a four-point smoothing, reference lines modem values from surface samples. Age model after Domack et al. (in press). The high modem values were reached only twice during the Holocene, prior to 9 ky BP and around 0.5 ky BP.
156 Palmer D eep b a sin m
Figure 5 .1 0 shows the occurrences of foraminifers in core 1099 Palmer Deep basin IH, and the sedimentological units described earlier. Few species occur below 75 m core depth. The lower mud turbidite contains very few occurrences of small taxa such as r. intermedia and F. fusiformis. Foraminifers are diverse in the proposed diamicton (40-
32 m core depth). The upper mud turbidite contains mainly small species, whereas larger such as M. arenacea and B. aculeata are rare. The upper 25 m show decreasing number of species.
The pattern is similar in both the diversity and BFAR data, the latter calculated with an average sedimentation rate of 0.254cm/yr. The mud turbidites are characterized by low values of both proxies, whereas the sandy turbidites/diamictons show elevated and variable diversity and BFAR. The deposition of the diamicton in 1099 concluded at
10.6 ky BP (Fig. 5.10) if the mud turbidite is extracted, and an average sedimentation rate of 0.254 cm/year assumed. Diversity and BFAR were both elevated from -10-8 ky BP, then decreased during the later Holocene. Holocene diversity values were mostly lower than those from modem environments from surface samples. In contrast, BFAR were elevated, compared with modem values.
157 1099 S: >1 Pi P Palmer Deep basin HI a a a 0 Q- a a « a 1 g Oa 5' §- S' (1400 mbsl) 2 #: a" a a a Ci a 1 à a' R % I t a a I S'
0 (N = 279) 5 -j o o ,0 0 o I i 8 o 0 8
o J -5—S- Mud Turbidite 30 i 8 ! O 8 8 9 8 9 9 0 33 i § I g S § g § 8 I 8 8 o i Diamicton ? on 3 40 d -8— §— 0— o— 8— 8 ------2------a. ■§. 45 d
S* 50 - cn Mud Turbidite O D3 - O o « o j 4 - "cr
. j 0 0 8 9 0 e o o o o 30 : -8- -e- o 8 o 0 0 33 j o 8 \ ° o o 0 0 Turbidite? 80 4 8 o 85
Figure 5.10. Occurrences of foraminifers in core 1099 from Palmer Deep basin DI. Turbidites and the proposed diamicton are indicated.
158 1099 Diversity BFAR Palmer Deep basin DI (1400 mbsl) (# species) (# cm'kyr') 12 10 10000
( N - 168)
ra -a
10 -
Diamicton ?
Figure 5.11. Diversity and benthic foraminiferal accumulation rates (BFAR) from the Palmer Deep basin III (core 1099). Thicker black lines indicate a four-point smoothing. Reference lines show modem values from surface samples. Age model after Domack et al. (in press).
159 Principal component analysis
Palmer Deep basin I
The benthic species of core 1098 from Palmer Deep basin I were grouped by Q- mode PCA into three principal components (QPC1-QPC3) that accotmt for 91.78 percent of the variance within the data (Table 5.1). Each principal component consists of one dominant and zero to one subsidiary species. Af. arenacea (QPC 1) accoimts for 72.49 % of the variance and is dominant dining the middle and early Holocene (Fig. 5.10). The B. aculeata (QPC2) assemblage explains 13.66 % of the total variance. This assemblage includes B. pseudopunctata as subsidary species and is dominant during the last 3.5 ky
(Fig. 5.12). The F. fusiformis (QPC3) assemblage includes 5.63% of the total variance is.
In addition to the dominant species F. fusiformis this assemblage consists of the subsidary species G. crassa and G. biora and occurs exclusively prior to 9 ky BP.
Three faunal turnovers are apparent. The first occurred at 11.5 ky BP and is marked by the first occurrence of F. fusiformis (QPC3). Another took place at the early/mid-Holocene transition at 9 ky BP with the last occurrence of the F. fusiformis
(QPC3) assemblage. The most recent, arotmd 4-3 ky BP at the mid-/late Holocene transition, is characterized by the change firom M. arenacea (QPC 1) to B. aculeata
(QPC2) dominated assemblages.
160 Q-mode assemblages
Palmer Deep basin I Palmer Deep basin III
1098 1 099
Species QPCl QPC2 QPC3 QPCl QPC2 QPC3
Astronamon echolsi -0J.9 -0 3 7 0.08 -0.36 -0.47 -030 Bolivina pseudopunctata -0 3 6 0.72 -0.09 -0.44 1 1 B utim ina aculeata -0 3 9 3.13 -0.05 -0.05 -0.60 Cibicides lobatulus -0 3 1 4)36 0.00 -- - EpistomineUa exigua - -- -0.37 -034 -0.44 Fursenkoina earlandi -030 -037 0.21 -0.35 4)30 4)31 Fursenkoina fiisiform is -0.16 -0.47 QË] -0.03 4)34 1 2.86 1 Globocassidulina biora -03.9 -0.41 032 -030 -0.42 -0.63 Globocassidulina crassa rossensis -033 -0.47 037 -0.33 -0.46 -0.48 M iliam m ina arenacea 0.14 0.09 1 33 0 1 ■0.15 -0.14 bfonionella iridea -0 3 1 -0.37 0.08 -0.36 -0 3 9 031 PuUenia bulloides -0 3 0 -0 3 S 0.04 -030 -0 3 6 -0.62 Trochammina intermedia -O.Oi -033 -2.91 -0.11 -0.45 -0.20 Trifarina angulosa -0 3 1 -036 0.00 -- -
variance explained (%) 72.49 13.66 5.63 31.89 31.12 16.33
Table 5.1. Species composition of Holocene foraminiferal Q-mode assemblages of cores 1098 and 1099 from the Palmer Deep basins. Dominant and important associated species are outlined.
161 O D P 1098 Palmer Deep basin I (1000 mbsl)
Q-mode PCI Q-mode PC2 Q-mode PC3 (N = 526) M. arenacea B. aculeata F. fusiformis (PC loadings) (PC loadings) (PC loadings)
- 0.2 0.2 0.6 - 0.2 0.2 0.6 - 0.2 0.2 0.6 1
fS X Î o_
2 - o' o s o
5 - > a . 6 - I X o_ ? o' C3 7 - o -O o
10 - Hiatus X
11 - or> o 12 -
13
Figure 5.12. Q-mode foraminiferal assemblages (3-component model) from core 1098 of Palmer Deep Basin I. Thick black lines are fourth moving average trend lines. Loadings higher than 0.4 indicate the dominance of a component. Early/mid-Holocene and mid- /late Holocene boundaries as suggested by Domack et al. (in press) are indicated.
162 Palm er D eep basin m
The benthic species of core 1099 firom Palmer Deep basin DI were grouped by Q- mode PCA into three principal components (QPC1-QPC3) that accounted for 79.34 percent of the variance within the data. Each principal component consists of one dominant and zero to one subsidiary species. Af. arenacea (QPC 1) accounts for 31.89 % of the variance and shows regularly spaced high firequency fluctuations during the mid-
/late Holocene (Fig. 5.11). The B. aculeata (QPC2) assemblage explains 31.12 % of the total variance. This assemblage includes B, pseudopunctata as subsidiary species and is dominant during most of the last 10 ky (Fig. 5.11). 16.33 % of the total variance is included in the F. fusiformis (QPC3) assemblage. In addition to the dominant species F. fusiformis, this assemblage consists of the subsidiary species B. pseudopunctata and occurs exclusively prior to 8 ky BP.
5.5. Discussion
Diversitv and BFAR
Diversity and benthic foraminiferal accumulation rates (BFAR) of 1098 and 1099 show large discrepancies (figure 5.14). Diversity and BFAR are considerably elevated during the mid-Holocene in 1099, compared with the 1098 record. A possible cause for the poor correlation may be contrasting deep-water circulation. Barker et al. (1999) suggested that the deeper basin DI, connected by a deep chaimel to the outer continental shelf, may have allowed an intensified deep-water circulation. An intensified circulation
163 ODP 1098 Palmer Deep basin III (1400 mbsl) Q-mode PCI Q-mode PC2 Q-mode PC3 M. arenacea B. aculeata F. fusiformis (N = 133) (PC loadings) (PC loadings) (PC loadings)
- 0.2 02 0.6 1 02 02 0.6 I -02 0 2 0.6 1
> ocn
10 4
Diamicton ?
Figure 5.13. Q-mode foraminiferal assemblages (3-component model) from core 1099 of Palmer Deep basin HI. Thick black line is fourth moving average trend line. Loadings higher than 0.4 indicate the dominance of a component. Early/mid-Holocene boundary as suggested by Domack et al. (in press) and possible diamicton, deposited by the Last Glacial Maximum (LGM) are indicated.
164 Diversity BFAR (# species) (#cm'‘ ky')
10 15 1 ICO 10000 1000000
I I I I I I I 1 I— L _ I t n ttui » » » » f *»* * ' ' ' *»»* \ 1098 S i 1 - S’ 1098 B asin I Basin I o_s o'rt n
.!•
]l six > \ CRO \ 1099 Basin III ? .}c "T3C3 --1 0 9 9 Basin III
9 -r 1 n to
11 - o' « (Bs 12 -
Figure 5.14. Diversity and benthic foraminiferal accumulation rates (BFAR) of core 1098 from Palmer Deep basin I and core 1099 from basin HI. Lines have been smoothed by four-point running average, age model after Domack et al. (in press). Early/mid- Holocene and mid-/late Holocene boundaries as suggested by Domack et al. (in press) are indicated. Note that diversity and BFAR of 1099 are elevated during the mid-Holocene in comparison to 1098, whereas during the early and late Holocene the fluctuations appear to be more synchronous.
165 might have provided more nutrients and oxygen for benthic foraminifers. Palmer Deep basin I (1000 mbsf) on the other hand is separated by a shallow sih (-700 m) firom the other Palmer Deep basins and may have experienced restricted deep-water circulation, resulting in oxygen or nutrient depletion, and/or increased salinities. Alternatively, the assumed sedimentation rates calculated for 1099 may be too high, which would result in high BFAR values. However, it would not explain the generally higher diversity in 1099 during the mid-Holocene. Since the diversity has been calculated excluding agglutinated species with low preservation potential (for discussion see chapter 2) it may imply that partial dissolution removed calcareous species firom the 1098 record. Foraminiferal test accumulation rates of the dominant species have been calculated to evaluate this possibility (Fig. 5.15).
Observations of surface samples firom the study area (Table 5.2) revealed that the agglutinated species M. arenacea has a high preservation potential and is not influenced by dissolution processes that would affect calcareous taxa. Figure 5.14 shows that the fluctuations of Af. arenacea are comparatively similar in 1098 and 1099.
B. aculeata was found to possess the highest resistance towards dissolution of all calcareous foraminifers in the study area (Table 5.2), with a theoretical 67.04 % o f the original number of specimens preserved. The correlation of B. aculeata between 1098 and 1099 is fair during the last 3.5 ky BP. Prior to 3.5 ky (Fig. 5.13) B. aculeata is more abundant in core 1099 fi-om basin m , even though the site is 400 m deeper than the site of core 1098. A shallow calcimn compensation depth can thus not be responsible for the hypothesized partial dissolution of B. aculeata in the 1098 record. The unusual pore
166 M. areiicea B. aculeata E fusiformis (#/cm‘ ky"') (#/cm' ky ') (#/cm ‘ky ')
10 1000 I00000 10 1000 I00000 10 1000 I00000 • 1 « t t I ttt t I t t t I nt t_ » 1 i Hi ' « f t t t t.1 S3 1098 1098 1098 I - S' basin I basin I basin I X ^ - ft> s rs
4 - - 1099 _1099 \ 1099 basin III basin III basin III 5 -
> a. 03 6 - I n X o_ o CO 7 - n -a cs n5 8 -
n S3
10 - 33 II - o fSn s 12 - rtl
13
Figure 5.15. Foraminiferal test accumulation rates for the most abundant species in 1098 from Palmer Deep basin I and 1099 from Palmer Deep basin DI. Thiclk black lines indicate values from 1098; gray lines specify values from 1099, with both smoothed by four-point running average. Vertical reference lines indicate modem values from surface samples. Age model from Domack et al. (in press).
167 water chemistry of 1098, with an extremely deep sulfate reduction zone (~ 20 mbsf.
Barker et al„ 1999), may have promoted early diagenetic dissolution (see chapter 7 for discussion). Partial dissolution would also explain the fluctuations of F. fusiformis, the third dominant species. Unlike the other dominant species, the fragile and small F. fusiformis was found to have a very low preservation potential in modem surface samples, resulting in the rapid postmortem dissolution of most of its tests (Table 5.2). F. fusiformis is at times abimdant during the mid-Holocene in 1099 of Palmer Deep basin m , indicating that preservation conditions for calcareous foraminifers must have been excellent. Core 1098 from basin I on the other hand is barren o f F. fusiformis during the entire mid-Holocene. It is theoretically possible that F. fusiformis was originally present in basin I during this interval, and was removed by partial calcite dissolution.
This leads to the important question, how was the resistant B. aculeata influenced by dissolution? It cannot be answered at this time given the imcertainties in the age- control and stratigraphy of 1099. Core 1099 contains abimdant turbidites; and it is possible that most of its foraminifers encountered have been reworked. The nearby
Andvord drift record shows the occurrence of B. aculeata confined exclusively to the late
Holocene (see chapter 6). B. aculeata is absent during the mid-Holocene in the Andvord drift, but the abundance of F. fusiformis in the same interval indicates that partial dissolution may not be the cause in this case. It is thus possible that the absence of B. aculeata during the mid-Holocene in the Palmer Deep basin I is primarily a paleoceanographic signal despite the aforementioned considerations of dissolution.
168 BFAR Standing stock PI (#fcm kyr"^) (fiicva kyr'^) (%)
M. arenacea 392 308 127.11 B. aculeata 634 946 67.04 B. pseudopunctata 232 3016 7.70 F. fusiformis 34 1408 2.38
Table 5.2. Benthic foraminiferal accumulation rates (BFAR), standing stock (living specimens), and preservation index (PI, standing stock/BFAR x 100) firom surface samples. Note that F. fusiformis produces a high number of living specimens but the lowest BFAR, resulting in theoretically 2.38 % of the original number preserved in the fossil record. B. aculeata has the highest preservation potential of all calcareous foraminifers in the study area with 67.04% preservation. The preservation index of M. arenacea exceeds 100%, highlighting the high preservation potential
In conclusion, although partial dissolution may have removed the less resistant F. fusiformis firom the 1098 record, the fluctuations of B. aculeata are thought to present a primary paleoclimate signal rather than a dissolution pattern. The occurrence of B. aculeata in the Palmer Deep basin HI during the mid-Holocene may be due to uncertainties in age control more effective deep water circulation or better calcite preservation conditions.
169 Principal component analysis
The defined Q-mode faunas in core 1098 and 1099 are almost identical in their faunal composition. Af. arenacea, B. aculeata, and F. fusifomtis are dominant species in the first three principal components of each core. The only major difierence is the occurrence of B. pseudopunctata as an important species in the F. fusiformis (QPC3) assemblage firom 1099. In chapter 2 it was shown that the calcareous species B. pseudopunctata has a low preservation potential under modem conditions in the Palmer
Deep (Table 5.2). It may indicate further evidence for the overall better calcite preservation conditions in 1099 of basin HI.
Ecological adaptations of the dominant species of the Q-mode faunas are reviewed below (for detailed discussion see chapter 2). The QPCl assemblage is dominated by Af. arenacea. Af. arenacea is prevalent in Saline Shelf Waters (SSW) of the
Antarctic continental margin (Murray, 1991). Calcareous foraminifers are typically absent in hypersahne settings (Murray, 1991). SSW are an essential ingredient for
Antarctic Bottom Water formation (Carmack & Foster, 1975; Sugden, 1982). Repeated episodes of sea ice formation in a single season, in areas such as the southern Weddell
Sea, result in the most hyper-saline water mass on the Antarctic continental shelf (Jacobs et al„ 1979). An alternative mechanism for the production of SSW involves the formation of dense super-cooled Ice Shelf Water beneath an ice shelf (Jacobset al., 1985; Jacobs,
1986). Mackensen et al. (1995) suggests that the preservation of certain agglutinated species, such as Af. arenacea, is independent of carbonate saturation and redox conditions, which influences the preservation of calcareous tests. The fact that Af. arenacea has a continuous record in the Palmer Deep provides additional evidence for
170 this hypothesis. The mono-specific appearance of M.arenacea (QPCl) is therefore presumably due to high preservation potential and ability to live in high salinities of Af. arenacea.
The dominant species of QPC2, B. aculeata, is common in organic rich sediments with moderate oxygen content (Mackensen et at., 1993), and normal marine salinities
(Harloff & Mackensen, 1997). The B. aculeata assemblage described by Ishman &
Domack (1994) firom the Bellingshausen Sea was linked to up welling of warm and nutrient-rich CDW and is similar to the B. aculeata (QPC2) assemblage defined in this study. The use of B. aculeata (QPC2) as indicator of CDW and open-marine conditions during the Austral summer was proposed (Chapter 2).
The dominant species o f Q-PC3, F. fusiformis exhibits a high tolerance of oxygen-depletion in the sediment. As Stainforthia fusiformis it was reported firom periodic anoxic Norwegian Qords (Gupta & Machain-Castillo, 1993), surviving even high contents of HzS in the pore-water, fatal to all but few organisms (e.g. Bernhard, 1993).
The latter author suggests that Globocassidulina cf G. biora possesses bacteria that may aid in anaerobic survival G. biora is also a constituent of F. fusiformis (QPC3) in this study, indicating that this assemblage may be dominant when oxygen-levels were too low for other foraminifers to survive. In contrast to Af. arenacea, F. fiisiformis seems to be more affected by salinity fluctuations (Gupta & Machain-Castillo, 1993).
F. fusiformis (QPC3) is similar to the Fursenkoina spp. assemblage described by
Tshman and Domack (1994) firom the adjacent Gerlache Strait and associated with the cold Weddell Sea Transitional Water (WSTW). Leventer et al. (1996) suggested that maximum primary productivity in the surface waters of the Antarctic Peninsula occurs
171 during stratification of the water column caused by melt-water lenses. Melt-water pulses firom the Weddell Sea may have triggered enhanced primary productivity, organic matter accumulation in the sediment, and subsequently, a proliferation of the eutrophic F. fusiformis (QPC3). The dominance of F. fusiformis (QPC3) likely indicates normal marine salinities but high organic contents, caused by high primary productivity and/or the intrusion of the WSTW into the Palmer Basins.
The fluctuations of the defined Q-mode faunas during the last 13 ky BP in the
Palmer Deep basins are shown in figure 5.16. During the last 3.5 ky the fluctuations of
Af. arenacea (QPCl) and B. aculeata (QPC2) appear similar in 1099 and 1098, with a faunal turnover occurring between 4-3 ky BP. The distribution patterns seem to suggest variable extent of sea-ice, with minimal sea-ice at 3.2-2.1 ky BP and 0.9-0.2 ky BP, as indicated by high loadings of the Circumpolar Deep Water (CDW) indicator B. aculeata
(QPC2). Alternately, the dominance of the Saline Shelf Water indicator M. arenacea
(QPCl) implies periods of more persistent sea-ice, or, alternatively, periods of increased melt water input prior to 3.3 ky BP, 2.1- 1.6 ky BP, 1.2-1 ky BP, and 0.2 ky BP. In the adjacent Andvord drift and northern Gerlache Strait (see chapter 6) maximum benthic foraminiferal accumulation rates (BFAR) and diversity during the 4.5-2.5 ky BP period point to a climatic optimum, with a gradual cyclical decrease in the proxies. Important is the first occurrence of the B. aculeata (RPC2) assemblage in the Andvord drift record ~
3.3 ky BP ago, which is equivalent to the faunal turnover in the Palmer Deep.
172 Q-mode PCI Q-mode PC2 Q-mode PC3 M. arenacea B. aculeata K fiisiformis (PC loadings) (PC loadings) (PC loadings)
- 0.2 0.2 0.6 -02 02 0.6 1 - 0.2 02 0.6 i Î t — 1_ _i— 1
\ l 0 9 8 t- b a sin I ■ T
n o
1099 : 1098 basin III basin I 1 -
oao
n
1098 / basin I n
10 - \ 1099 \ 1099 basin III basin III n n 12 - r
Figure 5.16. Q-mode foraminiferal assemblages (3-component model) from Palmer Deep basin I (1098) and HI (1099). Lines have been smoothed by four-point (1098) and two- point (1099) moving average. Loadings higher than 0.4 indicate the dominance of a component. Age model from Domack et al. (in press.). Note the faunal turnover from M. arenacea (QPCl) to B. aculeata (QPC2) at 4-3 BP.
173 Prior to 3.4 ky BP the records from 1098 and 1099 appear to contain contrasting events. Few peaks of the CDW indicator B. aculeata (QPC2) are present in 1098, whereas the same assemblage continues to dominate in 1099. The F. fusiformis (QPC3) assemblage was insignificant over the last during the last 7.8 ky.
Given the aforementioned uncertainties about age control of 1099 from Palmer
Deep basin m and dissolution processes of 1098 from basin I during the mid-Holocene, the existence of a warmer mid-Holocene cannot unequivocally be confirmed or refuted from the foraminiferal data at this point. A detailed radio-chronostratigraphy is needed to clarify the 1099 record.
If the 1099 record turns out to be correctly dated, it would imply that the Palmer
Deep basins experienced three major periods of warmer conditions and intrusion of CDW during the last 10 ky. The oldest of these warm periods occurred at the early/mid-
Holocene transition ~10-9 ky BP, an intermediate during the Mid-Holocene at —7.8-5 ky
BP, and the most recent during the late Holocene at ~ 3.7-0.8 ky BP.
174 5.6. Paleoclimate synthesis
The bipolar insolation signal
The summer insolation values for the last 13 ky were calculated for the GISP2 and Palmer Deep latitudes using free software from Paillard et al. (1996) based on the work of Berger (1978). June 21 and Dec 21 were selected for the GISP2 and the Palmer
Deep, respectively, corresponding to the summer solstices for both hemispheres.
Berger (1978, 1992) provided the theoretical solution to calculate the insolation for the last 1 million years. Since the groundbreaking work o f Imbrie et al. (1984) it has been well established that the orbital forcing of the Mflankovitch cycles is an important pace setter for the (Quaternary climate.
Figure 5.17 shows summer insolation curves for 75 degrees north latitude
(GISP2) and 65 degrees south latitude (Palmer Deep) from the present to 13 ky BP
(calculated after Berger, 1978). In the Northern Hemisphere, the highest summer insolation occurred during the early Holocene, at about 11 ky BP. Since that time, the
Northern Hemisphere summer solar radiation has decreased to 502 watts per square meter
(W/m^). It was suggested that the difference was sufficient to pace the Holocene climate, since the Northern Hemisphere climatic optimum occurred during the early Holocene
(e.g. Alley et al., 1995), and cold phases such as the Neoglacial during the late Holocene.
In contrast, the summer insolation of the Palmer Deep reached a minimum of 488
W/m^ around 12 ky BP, then increased steadily to a peak of 516 W/m^ at 2.5 ky BP. The last 2.5 ky BP saw declining values to 512 W/m^. Although the maximum difference is smaller (-28 W/m^) than that calculated for the Northern Hemisphere, an analog climate
175 ODP 1098 Palmer Deep basin I
Q-mode PCI Q-mode PC2 Insolation B. aculeata M. arenacea (W/m') (PC loadings) (PC loadings)
- 0.2 0.2 0.6 480 500 520 560
Palmer Deep
Onset o f climatic _ optimum in Antarctica
> eraa 9 C3 -a
Hiatus Onset of climatic optimum in the Northern Hemisphere
GISP2
Fig. 5.17. Q-mode foraminiferal assemblages from core 1098 of Palmer Deep basin I and summer insolation at solstices calculated after Berger (1978) for the GISP2 and Palmer Deep latitudes.
176 forcing effect seems likely. Another climate force may be the upweHing of deep water. It was however calculated that today's southward oceanic heat transport provides a comparatively small net flux to the atmosphere (~ 3 watts/m^) along the Antarctic coastal margin (Jacobset al., 1985).
On a shorter time scale, other periods of solar irradiance variability, such as sunspot cycles, became apparent over the last decade. For instance. Lean & Rind (1999) linked the colder climate during the Maunder minimum (-LIA, 1645-1715) to a slightly lower solar irradiance (0.3 W/m^). Leventer et at. (1996) proposed a similar cold event in the Antarctic Peninsula as well as a solar driven 200 years variability. Since these short cycles in solar variability produce presumably rather small differences, one would expect that the 28 W/m^ difference during the course of the Holocene in the Palmer Deep must have had even more climate forcing impact. In conclusion, a bipolar climate that is in phase during the entire Holocene seems unlikely according to most previous studies and the Mflankovitch theory.
Comparison with other proxies from core 1098
Four drafts (submitted to Paleoceanography) on climate proxies from core 1098 became available to the author few weeks before the completion of this dissertation. It has to be pointed out that the drafts may be subject to changes in the review process.
Holocene benthic foraminiferal assemblages were used as proxies for tracking paleodeep- water flow and paleoproductivity and their strengths and weaknesses have been discussed in previous chapters. Two of the publications use the planktic record (diatom assemblages and total diatom abundances) as indicators of climate change (Sjunneskog &
177 Taylor, submitted, Taylor & Sjunneskog, submitted). Two other papers address the sedimentary record, the magnetic susceptibility and mass accumulation rates/radio carbon ages (Brachfeld et al., submitted, Domack et at, in press). Strengths and weaknesses of those proxies are discussed below.
The planktic record
The use of planktic (living in surface waters) diatom abundances as paleoclimatic indicators is based “on the simplified view that warm, stable surface water, which often forms as a result of sea ice melt, (Estrada & Delgado, 1990), produces an environment suitable for diatom blooms” (Sjuimeskog & Taylor, submitted). It was therefore concluded that diatom abundance in the sediment could be used as a proxy for marine primary productivity (Scherer et al., 1992). However, this simple model does not take the influence of oceanic currents on the deposition of planktic diatoms at the sea floor into account. Diatom shells (firustules) are easily transported by ocean currents, and the presence in some terrestrial settings indicated that even aerial transport is possible. The discrepancy in the planktic and benthic proxies (Fig., 5.18) during the late Holocene may be explained by changes in the current flow regime as welL Foraminiferal evidence indicated that intrusions of CDW into the Palmer Deep and Andvord drift was restricted to the late Holocene. If that were the case, deep-water circulation increased during the late Holocene and presumably allowed lesser amounts of fine-grained material to settle on the seafloor. This would explain the lowered diatom productivity reported by
Sjunneskog & Taylor during the late Holocene. The authors observed also high and variable diatom abundances prior to 4.5 ky BP and interpreted this as a climatic optimmn
178 Palmer Deep basin I
D eep w ater Surface water Sediment foraminifers diatoms MS & MAR 0 -| Lowered planktic Neoglacial productivity 1000 - high and Sea ice diatom 2000 - variable MS assemblage lowered MAR 3000 More persistent 4000 sea-ice? low benthic 5000 productivity Lower planktic -• 6000 productivity @ .D fim & 7000 few incursions U of CDW - 8000
9000 higher primary Climatic 10000 productivity than today Reversal 11000 H extremely high intensified ice production from rafting 12000 First forams: M . arenacea 12.8- 11.7 ky BP Deglaciation 13000 -I high and variable MAR 14000
Figure 5.18. Comparison of the benthic, planktic and sedimentary record of core 1098 from the Palmer Deep basin I. CDW: circumpolar deep water, WSTW: Weddell sea transitional water, SSW: saline shelf water, MS: magnetic susceptibility, MAR: mass accumulation rates, IRD: ice rafted debris. Diatom data from Sjunneskog & Taylor (submitted) and Taylor & Sjunneskog (submitted), MS data from Brachfeld et al. (submitted), age model, MAR and IRD data from Domack et al. (in press).
179 of high productivity (Fig., 5.18). A factor of 2-3 increase in silica content in the mid-
Holocene interval of 1098 was also reported (Brachfeld et al., submitted). However, this could also be caused by a less vigorous deep-water circulation as indicated by the absence of the CDW during the mid-Holocene in the Palmer Deep, allowing more fine grained material to settle on the seafloor. A paleoflow record from the northern Scotia
Sea provides evidence for the CDW flow during the Holocene (Howe & Pudsey, 1999).
The authors concluded that the CDW was strong and fluctuating in the early Holocene, and stabilized and less vigorous during the mid-Holocene.
Benthic foraminifers live within the sediment and are therefore much less prone to redeposition than diatoms. It is perhaps the dependence on the current velocity that explains the considerable differences in the benthic and planktic faunal results from core
1098 (Rg. 5.18). In good agreement however with the first occurrence of benthic foraminifers (Af. arenacea) is Sjunneskog & Taylor’s note of “extremely high” diatom production starting at 12.8 ky BP.
Sedimentation rates & magnetic susceptibility
High mass accumulation rates (MAR) (Domack et al., in press) during the mid-
Holocene were interpreted as due to a climatic optimum with enhanced biogenic productivity (Fig. 5.18). Low MAR was thought to indicate low productivity due to
“Neoglacial” conditions (Domacket al., in press). In Antarctic waters, however, biogenic silica derived from org anism s such as diatoms is a major constituent (up to 75%,
Gersonde & Wefer, 1987) of m arine sediments. It is likely that mass accumulation rates
180 in the area are m ainly determined by the productivity of diatoms and other primary producers. Therefore, MAR is presumably not independent of the diatom abundance proxy and may be influenced by changes in the flow regime as welL
The late Holocene fluctuations of the magnetic susceptibility (MS) in cores from the study area are thought to be mainly due to periodic diatom blooms (Leventer et al.,
1996; Kirby et al., 1998). The MS record may therefore also depend on the primary productivity and the bottom water flow regime. MS was low in core 1098 prior to 3.5 ky
BP, presumably caused by a change in sediment provenance and/or sediment transport processes (Brachfeld & Baneqee, 2000, Brachfeld et al., submitted).
The authors suggest that a cessation in locally derived ice-rafted debris caused the drop in MS, representing the transition from the mid-Holocene climatic optimum to the
Neoglacial period. Given this, the MS record seems to contain both a sedimentary signal and a climatic signal
The Younger Drvas (-12.7-11.6kv BPl
The record of 1099 from basin IH was not considered for the interpretation since abundant turbidites and lack of age control prevented reasonable correlation with the well dated 1098 record during this period. The fluctuations of the defined Q-mode faunas during the Younger Dryas and early Holocene in core 1098 from Palmer Deep basin I are shown in figure 5.19. The presence of F. fusiformis, which had a low dissolution resistance, during the early Holocene indicates that preservation conditions were excellent during this interval Dissolution processes can be neglected in this case.
181 The first diatoms appear in the Pahner Deep record around 13.2 ky BP and were thought to be deposited beneath a floating ice shelf (Sjunneskog & Taylor submitted).
The first benthic foraminifers (Af. arenacea) occured at 12.5 ky BP (Fig. 5.5) in Palmer
Deep basin I, with the assemblages remaining monospecific until 11.6 ky BP. Sjunneskog
& Taylor (submitted) noted “extremely high” diatom production firom 12.8 ky to 11.7 ky
BP. Those dates are similar to the dmation of the Younger Dryas (YD) in the GISP 2 ice core (-12.7-11.6 ky BP, AHey et aL, 1995). Rebesco et al., 1999 proposed that Palmer
Deep basin I was filled with grounded ice during the preceding Last Glacial Maximum
(LGM). If one assumes that benthic life would not be possible under those conditions, the first occurrence of benthic foraminifers at 12.5 ky BP marks the final disintegration of a thick ice shelf and the end of the LGM in the study area. This would imply that the YD, an extreme cold phase in the Northern Hemisphere, was a time of warming in the
Antarctic Peninsula. Alternatively, the disintegration of the hypothesize Palmer Deep ice shelf might have been caused by global sea-level rise at that time (Sowers & Benders,
1995; Bentley, 1999).
There are considerable uncertainties about nature and duration of the YD in the
Southern Hemisphere, partly due to poor dating control (White & Steig, 1998). The main obstacle in defining the duration of the YD is the apparent spatial climatic variability during the Holocene that exceeds the precision of most dating methods. Undoubtedly, the best dated record of the YD cold event comes firom the Greenland ice cores (Alley,
2000 ).
182 ODP 1098 Palmer Deep basin I (1040 mbsl)
Q -m o d e P C I Q -m o d e P C 2 Q -m od e P C 3 F. fusiformis (N = 30I) M. arenacea B. aculeata (PC loadings) (PC loadings) (PC loadings)
-0.2 0.2 0.6 I -02 02 0.6 I -0.2 0.2 0.6 L
_ J I ______I L
Hiatus
10.8 -
Figure 5.19. Q-mode foraminiferal assemblages (3-component model) from 1098 of Palmer Deep basin I. Lines have been smoothed by four-point moving average. Loadings higher than 0.4 indicate the dominance of a component. Age model from Domack at al. (in press.).
183 The Antarctic Cold Reversal, known from Antarctic ice core records (Jouzel et al., 1995), was commonly correlated with the YD from the Northern Hemisphere
(Johnson et at., 1992). It is thought that deglacial warming after the Last Glacial
Maximum was accompanied by the renewal of North Atlantic Deep Water (NADW) formation. The flow of warm NADW into the Southern Oceans was thought to warm and strengthen the Circumpolar Deep Water (CDW), thereby enhancing sea ice melting and atmospheric w arm ing along along the Antarctic coast (Imbrie et at., 1993). Weakened
NADW formation accounted for cold conditions during the YD (Lehman & Keigwin,
1992; Hughen et al., 1998). Evidence from Antarctica for this scenario was provided by the stable isotope record (5D) of Taylor Dome, suggesting a YD like event at this site
(Steig et al., 1998).
However, circum-Antarctic climate response may not be uniform. Recent methane measurements for the Vostok and Byrd station cores show that the Antarctic
Cold Reversal preceded the YD by at least 1000 years (Sowers & Bender, 1995; Blunier et al. 1998) in these locations.
A solution to this problem of asynchrony of bipolar climate during the YD may be the so-called seesaw effect (Stocker, 1998). Heat normally released in the Northern
Hemisphere by the deep water circulation is released in the South (Broecker, 1998) due to a weakening of the NADW in the North Atlantic.
The results presented in this research supports the latter hypothesis. Given that the age control of the 1098 record is well constrained, the first occurrence of benthic foraminifers at 12.5 ky is interpreted as the final disintegration of the ice shelf over the study site. Domack et al. (in press) recognize a deglacial period of high primary
184 productivity and iceberg rafting from 13.2-11.5 ky BP based on magnetic susceptibility, mass accumulation rate and ice rafted debris in the 1098 record, pointing to warmer conditions during the YD as welL
Early Holocene n i.6 to 9kv BP)
From 11.6 to 9 ky BP the foraminiferal record exhibits diverse assemblages, mainly consisting of species recently found in the adjacent Andvord drift and Gerlache
Strait to the north. The benthic foraminiferal accumulation rates are considerably elevated, reaching the high levels apparent in modem samples. Lower sea level and the intrasion of Weddell Sea Transitional Water (WSTW) into the Palmer Basins may have been the reason for the extension of F. fusiformis (QPC3).
Today, the WSTW is restricted to areas north of the Palmer Deep Basins (Ishman
& Domack, 1995), indicating that production of WSTW in the early Holocene was at times much stronger than today. Melt-water pulses from the Weddell Sea may have been responsible for those events during the early Holocene, causing enhanced organic matter accumulation, and subsequently, a proliferation of the eutrophic F. fusiformis (QPC3).
The distribution pattern of M. arenacea (QPCl) and F. fusiformis (QPC3) may be explained by this hypothesis. Most of the time, M. arenacea (QPCl) dominates because of persistent sea-ice cover, and is at times interrupted by short melt-water events, indicated by the F. fusiformis (QPC3) assemblage. Sjunneskog & Taylor (submitted) observed higher than today productivity in the diatom assemblages, which is in conflict
185 with Domack et a l's (in press) interpretation of this interval as a cold “climatic reversal”, based on mass accumulation rates. Coral records show a period of particularly rapid meltwater influx into the oceans around 11.4 ky BP (Bard et al., 1996). The source of meltwater is uncertain (Bentley, 1999) and may be related to the collapse of the
Laurentide ice sheet (Blanchon & Shaw, 1995). The foraminiferal evidence provided in this research however suggest that the Weddell Sea ice shelf may have played a role. A sudden warming at 11.5 ky BP is also present in Bolivian ice cores (Thompson et al.,
1998), hinting that the results from the Palmer Deep may indicate a synchronous climate response for South America and the Antarctic Peninsula.
In the North Atlantic the thermohaline circulation resumed and was at full strength by 11.6 ky BP (Stocker, 1998) when normal saline waters entered the Palmer
Deeps for assumedly the first time during the Holocene. Consequently, diverse benthic assemblages occur abruptly at 11.6 ky BP (Fig. 5.19). One such water mass providing normal marine waters may have been the warm and nutrient-rich Circumpolar Deep
Water (CDW), which is currently present in the Palmer Deep. A paleoflow record from the northern Scotia Sea provide an indication of strong but fluctuating CDW flow from
12.3 to -10 ky BP (Howe & Pudsey, 1999). Beyond 10 ky CDW flow stabilized and became less vigorous. The strong CDW during the early Holocene may help explain the first occurrence of the CDW indicator B. aculeata (QPC2) at 10.4 ky BP in Palmer Deep basin I.
The record from the Andvord drift (core JPC18, see chapter 6) is presiunably long enough to cover at least parts of the Early Holocene. The foraminiferal proxies BEAR,
Diversity and WSTW faunas (F. fusiformis) point to moderate benthic activity that do not
186 reach the high levels observed in the Palmer Deep during the early Holocene. A possible explanation may be that in the Andvord drift the sea ice produced during the Austral summer persisted longer due to a closer proximity to the coast.
Explanation for the termination of the early Holocene in the Palmer Deep is difficult. The diverse foraminiferal assemblages disappear abruptly at 9 ky BP.
Presumably the weakening of the CDW (Howe & Pudsey, 1999) played a role, indicated by the absence of B. aculeata beyond 9 ky BP. The diatom record shows a rapid, stepped increase in abundances, starting at 8.7, and was interpreted as the onset of the mid-
Holocene climatic optimum (Sjunneskog & Taylor, submitted). Enhanced mass accumulation rates were also interpreted as due to warmer climate (Domack et aL, submitted).
The Byrd ice core shows a major shift towards lower temperatures around 9ky BP
(Johnson et at., 1972), which is roughly equivalent to the onset of the climatic optimum in the Northern Hemisphere. It is hypothesized that after the last major oceanographic reorganization ending at 9 ky BP, the current ocean circulation pattern was established.
Heat was transported preferably to the North by the deep-water conveyor belt, magnifying the orbitally induced warming in the Northern Hemisphere during the mid-
Holocene. In the absence of the heat provided by the deep-water circulation, the low summer insolation over the Palmer Deep resulted in increased sea-ice, thereby depressing the open-marine benthic assemblages.
187 Mid-Holocene f~9-3.4 kv BP~)
A warmer, and thus more productive mid-Holocene is not evident in the
foraminiferal data from the Palmer Deep basin L Core 1098b lacks the open-marine
indicator B. aculeata (QPC2) in the interval from 9-3.51q^ BP. The dominance of
M.arenacea (QPCl) suggests more persistent sea-ice cover than today (fig. 5.12).
However, the lack of calcareous foraminifers in the mid-Holocene of 1098 might have
been caused by postmortem dissolution of the calcareous foraminifers as pointed out
above. An age model of 1099 is needed to clarify the uncertainties about the nature of the mid-Holocene in the Palmer Deep.
Higher sedimentation rates than today in the 1098 record were interpreted as due to an increased primary productivity during warmer conditions and minimal summer sea- ice (Domack et al, in press), as were increased diatom abtmdances (Sjuimeskog &
Taylor, submitted) Delta data from the Byrd ice-core (Johnsonet at., 1972) however show no evidence for a warmer period during the mid-Holocene but a pronounced peak from 9-9.4 ky BP. A recent paper by Yoon et al. (2000) proposed rather colder climate between 4-6.2 ky BP, “making the definition of the ‘Hypsithermal’ difficult in the South
Shetland Islands”.
The rapid change from M. arenacea to B. aculeata dominated assemblages indicates that a climatic threshold was reached around 4 ky BP. Such an abrupt climate change in response to the insolation signal requires strongly non-linear feed-back processes (Lagerkhnt & Wright, 1999). The threshold occurred at the same time as the
188 intersection of the Greenland and Palmer Deep insolation curves (fig. 5.17), indicating that the mid-Holocene/ late Holocene boundary in the Palmer Deep may be of global significance.
The late Holocene (3.4 — presenf)
The foraminiferal data suggest variable extend of sea ice over the last 3.5 ky BP in the study area (Fig. 5.20). In the Palmer Deep, assemblages vary between CDW faunas and SSW faunas. The CDW intruded occasionally into the Andvord drift area, as indicated by few peaks of B. aculeata during the late Holocene. There is a good correlation between the WSTW faunas (F. fusiformis) in the Andvord drift and the SSW faunas (Af. arenacea) in the Palmer Deep over the last 4 ky, indicating that periods of increased WSTW pushed the CDW northwards. This pattern may be related to oscillating glaciers in the Antarctic Peninsula during the past 2.5 ky (Clapperton, 1990).
189 C D W fa u n a s WSTW/SSW faunas B. aculeata F. fusiformis/ M. arenacea (PC loadings) (PC loadings)
- 0.2 0.2 0.6 -0.2 0.2 0.6 I
0.4 -
Palmer Deep b a sin I Palmer Deep * basin I
1.6 -
2 .4 -r OQ ^ 2.8 -
- Andvord drift W 3 .2 -
3.6 - Andvord drift
4.4
4.8 T
5.2 -
5.6 -
I 0 1 2 3 4 (PC scores)
Figure 5.20. Comparison of the 1098 record from Palmer Deep basin I with the Andvord drift record (JPC18, chapter 6). Note that activity of the CDW indicator B. aculeata is confined to the late Holocene in both locations. During the mid-Holocene, the Weddell Sea Transitional Water (WSTW) and Saline Shelf Water (SSW) were prevalent in the study area, as indicated by F. fusiformis and M arenacea, respectively.
190 CHAPTERS
THE HOLOCENE RECORD O F THE ANDVORD DRIFT
6.1. Summary
Benthic foraminiferal accumulation rattes (BFAR), diversities, and principal component analysis of foraminiferal assemblages from the Andvord drift and Gerlache
Strait are used here to establish an 11 ky paleoce^mographic record. From 11 to 7.2 ky BP high frequency fluctuations of BFAR indicatre periodic intrusions of Weddell Sea
Transitional Water (WSTW) into the study airea with subsequent blooming of a F. fusiformis assemblage. Presumably due to a pemnanent sea ice cover between 7.2 and 5.7 ky BP the conditions appeared unfavorable for benthic foraminifers. BFAR values drop below the modem level, and the WSTW indicato r F. fusiformis is very rare or absent. The proposed cold event corroborates reports of glatcial readvance in the Antarctic Peninsula between 6.7 and 5 ky BP (Shevenell et aL, 1996 ; Yoon et al., 2000).
Elevated BFAR, diversity, and WSTW fauna values centered around 4.5 - 2.5 ky
BP are interpreted as a Holocene climatic optdmum. The development of the climatic optimum was a rather gradual process with elevated BFAR, diversity and WSTW fauna values from 5.7 to 2.5 ky BP. The mid-/late- Holocene boundary as suggested by
Domack et a l (in press) at 3.4 ky BP in the Palmer Deep does not constitute a well- 191 defined datum in the Andvord bay and Gerlache Strait. There is an apparent 200-300 years cyclicity present within the climatic optimum. The last 2.5 ky saw declining BFAR,
Diversity and WSTW fauna values, pointing to a weaker influence of the WSTW in the study area.
6.2. Introduction
Previous studies suggested that currently very little sediment is produced by tidewater glaciers along the Pacific margin of the Antarctic Peninsula (e.g. Griffith &
Anderson, 1989), resulting in a very thin postglacial sediment cover. Recent high resolution seismic surveys however reveal more than 40 m of postglacial sediment cover in the southern Gerlache Strait and in fi-ont o f Andvord Bay (Harris et al., 1999). These authors claim the discovery of a “new type of inner shelf, glacial marine deposystem” called the “Andvord drift” at the entrance of Andvord Bay (Fig. 6.1). Although deposited in only 300-500 m water depth, the fine-grained sediments recognized are similar to deep-sea deposits (Harris et al., 1999). The term “drift” applied in glacial geology is defined as all rock material that is transported by a glacier or by running water emanating firom the glacier (Bates & Jackson, 1980). A regional deceleration over the drift leading to a slow moving gyre was proposed as a mechanism for the absence of coarse grained material and increased carbon flux (Harris et al., 1999). The sluggish nature of the assumed gyre increases the influx of fine biogenic detrius to the seafloor. Consequently, the coarse ice-rafted component is diluted (Bird, 1999; Maxwell, 1999).
192 CO South Shetiand islands / ® ^ Island Snxfy sfte ^
(J'JPCISH R°"9= Island uiano
Wiencto l^nd
lem cira island
CO s- s
63° 00" W 62° 40' W 62’20’W
Figure 6.1. Location and bathymetry o f study area in southern Gerlache Strait, Antarctic Peninsula. Glacial drainage patterns and divides are after Williamset al. (1989), the map after Harris et al. (1999). Positions o f NBP 99/3 cores JPC18 in the Andvord drift and JPC28 in the Gerlache Strait are indicated.
193 Short sediment cores collected firom the region indicate high sedimentation rates varying fi'om 0.15 to 0.32 cm yr'^ through the late Holocene (Harris et aL 1999). profiles firom core top samples point to less variable sedimentation rates, ranging firom
0.15 to 0.18 cm yr'^ (Domack & McLennan, 1996).
Based on these estimates, it was assumed that the maximum drift thickness of ~
40 m would take between 27 and 13 ky to accumulate (Harris et al., 1999). The sediment is thought to be supplied via the Gerlache Strait, Andvord Bay, and the Aguirre and
Errera Channels (Harris et at., 1999). Sediment-trap results suggest the composition of the Andvord drift sediments comprises ice-rafted debris, meltwater derived sût, and phytoplankton detritus (Mashiotta, 1992, Domack & Ishman, 1993; Domack &
Mammone, 1993). Consequently, very fine grained material accumulated in the Andvord
Drift in the absence of strong currents, similar to sediments in the Palmer Deep basins.
Due to the increased organic carbon flux it was estimated that the carbon accumulation in the Andvord drift was about 1.7 g/cm^ky'^ (Harris et at., 1999).
A previous study from the Andvord Bay based on a short core spanning the last
3000 years revealed cyclic changes in biogenic opal and organic carbon that reoccur every 200-300 years (Domack et al, 1993). Similar cycles were noted in the Palmer Deep basin I (Leventer et at., 1996). The high resolution record obtained from core JPC18 from the Andvord Drift (Fig. 6.1) is therefore considered an important addition to the Palmer
Deep record. Core JPC28 was collected from the southern Gerlache Strait, 12 km distant from JPC18. Benthic foraminiferal accumulation rates (BFAR) have been frequently used as a simple tool for estimating the primary productivity during the Quaternary
(Herguera & Berger, 1991; McCorkle et al., 1994). 194 BFAR are thought to be directly correlated to primary productivity in the surface waters, with higher productivity resulting in more food for the benthic communities and subsequently, higher BFAR and diversity in the benthic assemblages. More persistent annual sea-ice reduces the primary productivity by limiting light penetration, and periods of warming result in a melt-water induced stratification which enhances primary productivity (Leventer et al., 1996) in the study area.
The other climate proxy for JPC18 and JPC28 presently available is magnetic susceptibility (MS). The late Holocene fluctuations of the MS in cores firom the study area are thought to be mainly due to periodic diatom blooms (Leventer et al., 1996; Kirby et al., 1998). Leventer et al. (1996) suggested that high MS values occurred during
“normal” conditions in the study area. Strong winds and/or storms prevent stratification of the upper 100 m o f the water column, causing relatively low primary productivity and dominance of terrigenous sedimentation. MS lows are thought to be produced by thermal warming, which leads to weaker winds and increased melting of sea ice. The resulting water column stratification promotes high primary productivity, which dilutes the magnetic phase in the sediment. MS data were therefore considered a paleoenvironmental signal with mino r diagenetic overprinting in marine sediment cores firom the study area
(Brachfeld & Banerjee, 2000).
Detailed radiocarbon dating of cores firom the study area revealed cycles of warmer conditions and elevated primary productivity that reoccur approximately every
200 - 300 years (Domack et al., 1993; Leventer et al. 1996; Domack & Mayewski, 1999).
In addition to its utility as a paleoenvironmental proxy, the MS data can be also used for correlating cores from the study area (Domack & Ishman, 1992). Brachfeld &
195 Baneqee (2000) noted that marine sediment cores recovered from the Palmer Deep basins, the Gerlache Strait and Andvord drift show remarkably similar MS profiles.
Those records demonstrate regularly spaced peaks and troughs over the past 3.5 ky.
Prior to 3.5 ky BP, MS was low in all cores, presumably caused by a change in sediment provenance and/or sediment transport processes (Brachfeld & Baneqee, 2000).
The authors suggest that a cessation in locally derived ice-rafted debris caused the drop in
MS, representing the transition from the mid-Holocene climatic optimum to the
Neo glacial period. The transition from high and variable MS to uniformly low values will be used to correlate JPC18 and JPC28 with core 1098 from the adjacent Palmer Deep basin I. The transition in core 1098 is dated at 3.4 ky BP (Domack et al., in press).
6.3. Objectives
• The first goal is to establish a high resolution record of benthic foraminifers of cores
JPC18 and 28. Magnetic susceptibility data will be used to correlate JPC18 and 28
with core 1098c from Palmer Deep basin I, which is well dated. The resulting
preliminary age models of JPC18 and 28 will be utilized for an evaluation of the
aforementioned 200-300 year cycles in the Andvord drift and Gerlache Strait.
• Based on sedimentation rates derived from the preliminary age models, benthic
foraminiferal accumulation rates (BFAR) will be calculated for cores JPC18 and 28.
Subsequently, a high-resolution record of Holocene primary productivity will be
196 established. Special emphasis will be placed on the nature and tim ing of the Holocene
climatic optimum and mid/late Holocene transition in the Andvord drift and Gerlache
Strait in comparison to the Palmer Deep.
6.4. Material and Methods
Core NBP99/3 JPC18 (JPC18 hereafter) was retrieved in the Andvord drift during
the NBP cruise in April 1999 from 400 m water depth. JPC18 is 19.8 m long and was
sampled throughout at 5 cm intervals one year after core recovery. The samples were
processed for foraminifers utilizing the methods described in chapter 2. Core NBP99/3
JPC28 (JPC28 hereafter) was retrieved during the NBP cruise in April 1999 from 673 m
water depth at the southern end of the Gerlache Strait (64 38.647 S, 62 52.407 W). The
core was sampled one year after the cruise at 5 cm intervals. Only the uppermost 13 m (of
20 m) have been investigated in this study.
Detailed stratigraphies and age models of JPC18 and JPC28 are not available at
this time, pending completion by other workers. An approximate stratigraphy for each
core was established by visual investigation of the available sample material before processing and observations of the sand size fraction (>63 pm) of the processed samples.
As an auxiliary sedimentological tool the dry weight values (>63 pm) of the processed samples have been noted. Dry weight highs in this particular setting are thought to be caused by coarse grained turbidites, and dry weight values near zero by mud mass flows (Domack et al., 1998).
197 Benthic foraminifer accumulation rates (BFAR) were calculated with sedimentation rates derived from the preliminary age model The BFAR may have to be adjusted after more detailed chronologies of JPC18 and JPC28 become available.
BFAR values w eie considered directly proportional to the vertical flux of organic matter (Herguera & Berger, 1991) and will be used accordingly for interpretation in this study. Foraminiferal diversity (number of species) was calculated according to the methods outlined in chapter 2 as an additional proxy for faunal characterization. Q-mode
Princ^al Component Analysis (QPCA) of foraminiferal assemblages has been used to decçher major faunistic trends, following the methods described in chapter 2.
Rare species that might be a good tracer for environmental changes are however suppressed in QPCA (Schmiedl, 1995). Thus, R-mode Principal Component Analysis
(RPCA) was applied to the data set. Foraminiferal assemblages that contain significant but rare species could thereby be recognized.
6.5. Results
Stratigraphies and age models
AH samples collected from the Andvord drift and Gerlache Strait consisted of homogenous olive-green, diatomaceous mud. Obvious changes in sediment composition such as sandy layers were not observed.
198 The dry weight values of the fraction > 63 |im of core JPC18 from the Andvord
drift and the upper 14 m of core JPC28 from the Gerlache Strait are shown in figure 6.2.
The fluctuations are minor in both cores, the fraction >63 pm usually accounts for less
than 0.02 g. Distinctive peaks are due to large moUusk fragments at 12.2 m core depth in core JPC28, and large dropstones (>355 pm) at 3.2, 5.45, and 9.2 mcore depth in JPC18.
Two samples from JPC18 produced fragments of macrofauna, at 9.8 and 14.8 m core
depth. Other features encountered in the fraction > 63 pm were fecal pellets. They are
abundant in JPC18 between 2 to 4.5 m, and 13 to 13.2 m core depth. By comparison,
fecal pellets are less abundant in JPC28, except a section between 2 and 4.5 m core depth.
The proposed preliminary age models of JPC18 and JPC28 are shown in figure
6.3. In core 1098 of Palmer Deep basin I the drop in MS indicates the end of the mid-
Holocene at 7.8 m core depth, which is equivalent to 3.36 ky BP according to Domack et
al. (in press). A similar drop in MS in JPC18 occurred at 6 m core depth, and in JPC28 at
10 m core depth. The tie points were used to extrapolate the age model of 1098 to JPC18 and JPC28. If it is assumed that the upper 6 m of JPC18 were deposited during the last
3.36 ky, an average sedimentation rate of 0.18 cm yr'^is implied. If the sedimentation rates were consistent for the entire core length of 19.8 m, the record would span the last
11 ky. Accordingly, if the upper 10 m of core JPC28 contain the last 3.36 ky, an average sedimentation rate of 0.3 cm yr'^is implied. The upper 14 m of JPC28 may contain the last 4.5 ky.
199 JPC28 JPC18 Gerlache Strait Andvord Drift
dry weight dry weight (g) (g) 0.0 02 02 06 0 0 I I o 2 e % 2 3 ♦ O 3 4 5 8 o 4 o ♦ <=> 6 5 7 o 8 6 ♦ e 9 7 10
II 8 12 o 9 © 13 o 10 14 15 11 16 o 12 17 ^ 8 18 13 19 14 20
Legend I I Diatomaceous mud and ooze Fecal pellets • Dropstones (>355 um) M ollusks
Figure 6.2. Stratigraphie columns and dry weight values (>63 um) of JPC 18 and JPC28. Occurrences of dropstones, fecal pellets and mollusk fragments are indicated. Note the uniform fluctuations of the dry weight, which suggests that sedimentation processes remained relatively constant.
20 0 Susceptibility (X 10^ CCS)
JPC28 JPC18 10 9 8 Gerlache Strait Abdvord drift Palmer Deep (670 mbsl) (4 0 0 m bsl) (1030 mbsl)
200 400 0 200 400 SO 160
late Holocene
mid- Holocene
Figure 6.3. Proposed age models o f JPC18 and JPC28. Magnetic susceptibility data have been used to fit the age model o f 1098 (Domack et al., in press). Mid-/late Holocene boundary in 1098 as suggested by Domack et at. (in press) is indicated.
201 Foraminiferal occurrences, diversity and BFAR
Andvord drift
Nineteen benthic and one planktonic species (N. pachyderma sinistral) have been found in core JPC18 from the Andvord drift. F. fusiformis accounts for 55% of the total number of specimens. The four most abundant species, including also G. biora, T. intermedia, and Af. arenacea add up to 85% of the total counts. The down core occurrences of foraminifers in core JPC18 are shown in figure 6.4. Two species are present throughout the core, almost every sample yielded specimens of Af. arenacea and
T. intermedia. The agglutinated taxa S. bifomds and P. eltaninae on the other hand diminish with increasing core depth. There are only scattered occurrences of S. biformis below 8.5 m core depth, the same holds true for P. eltaninae below 10 m. A group of calcareous species including B. aculeata, B. pseudopwictata, G. crassa rossensis, and F. earlandi are mainly restricted to the 2.5 to 10 m interval F. fusiformis and G. biora are present throughout most of the core, except a section at 10 to 12.5 m core depth. The other species are more dispersed, not cotmting a cluster between 5.5 to 8 m core depth of
N. iridea, N. bradii, N. pachyderma, and E. exigua. Based on preliminary sedimentation rates derived from the age model described above, benthic foraminiferal accumulation rates (BFAR) values have been calculated as numbers of foraminifers per cm^ kyr'^ for both cores (Appendices F & G). Core JPC18 from the Andvord drift shows high frequency fluctuations ranging from 0 to 37944 tests / cm^ kyr'^ (Table 6.1; fig. 6.5). The average BFAR was 2644 tests / cm^ kyr'^. Intervals with low values occur at 16.2 to 18.4 m, 10.2 to 13 m, and 1 to 2.4 m core depth.
202 JPC18 Andvord drift M Pc Co ES Ci rï: C i Q M (400 mbsl) s # S: s î r I- I I! l r t E- I E - 5 ■p (N = 393) 11
O O 8 o O e o 0 o 8 8 8 o o ° § o 1 8 i I 8 o 8 § o 8 s g § 8 e 8 1 8 8 O o O 8 o O 0 o 9 e o o o g- 8 a o ■O — o o 8 o
O o o o
8 § e 8
Figure 6.4. Occurrences of foraminifers in JPC 18 from Andvord drift. Note the continuous record of M arenacea and T. intermedia, and the occurrence o f the Palmer Deep basin fauna including B. aculeata and B. pseudopunctata in the upper 10 m o f the core.
203 High values are recorded at 2.6, 4.4, 7, 7.8, 13, and 13.8 m core depth. Compared with BFAR from surface samples, the fossil values from JPC18 seem to be considerably elevated. The diversity also demonstrates high frequency fluctuations, ranging from 0 to
13 species (average 3.2). The diversity decreased from 20 to 11 m, then increased to peak values between 4.2 and 8 m core depth. The top 4 m depicted lower values, except for two peaks at 0.8 and 2.8 m core depth. Compared with diversities from surface samples, the fossil values in JPC18 were mostly lower except between 4.2 and 8.2 m core depth.
Gerlache Strait
Twenty benthic and one planktonic (N. pachyderma sinistral) species have been observed in JPC28 from the Gerlache Strait. Four species account for 85% of the total number. F. fusiformis is the most abvmdant with 40 %, followed by T. intermedia (20%),
Af. arenacea (15%), and N. iridea (10%). The occurences of foraminifers are shown in figure 6.6, grouped by their distribution pattern down core. Af. arenacea and T. intermedia are present throughout the core. The agglutinated taxa P. eltaninae and 5. biformis occurred in the upper part. The diverse calcareous species are limited below 4.5 m core depth, above that level only a few scattered occurrences of F. fusiformis, G. crassa rossensis and others are present. BFAR and diversity of core JPC28 from the
Gerlache Strait are shown in figure 6.7. The BFAR values fluctuate between 0 and 33600 tests / cm^ kyr'^ (Table 6.1, average 2640). Peak values of this proxy occur aroimd 12 m core depth. Above 12 m the BFAR decreased up-cores. A similar trend is evident in the diversity, fluctuating from 0 and 12 species (average 3.3).
204 JP C 18 BFAR D iversity Andvord drift (400 mbsl) (# cm’’kyr') (# species / sample)
10 1000 10000 0 4 8
(N = 393)
- 2
- 3
- 4
O. - 6
- 7 fi, CQ > v e M <
- 9
- 10
II 20
Figure 6.5. Records of benthic foraminiferal accumulation rates (BFAR) and diversity from the Andvord drift (JPC 18). Thicker black lines indicate a four-point smoothing, reference lines modem values from surface samples. The proposed age model is given for comparison, the raid-/late Holocene boundary (Domack et al., in press) indicated.
205 Holocene Assemblages
JPC18 JPC28 Andvord drift Gerlache Strait (400 mbsl) (670 mbsl)
# Samples 393 272
BFAR Min 0 0 (#/ cm^ kyr'^) Max 37944 33600 Average 2644 2640
Diversity Min 0 0 (# species) Max 13 12 Average 3.2 3.3
Modem assemblages
# Samples
BFAR (pot.fossil*) Min 280 (#/ cm^ kyr'^) Max 770 Average 454
Diversity (pot.fossil*) Min 3 (# species) Max 7 Average 4.6
Table 6.1. Benthic foraminiferal accumulation rates (BFAR) and foraminiferal diversity of JPC18 from the Andvord drift and JPC28 from the Gerlache Strait. Modem BFAR and diversity from surface samples of Andvord drift are given for comparison. Note the remarkably similar maximum and average BFAR values of JPC18 and JPC28. Compared with modem values from surface samples the BFAR of JPC18 from the Andvord drift are considerably elevated. Surface samples from the Gerlache Strait were not available to the author. * potential fossil = corrected by removal of disintegration susceptible species, which are not preserved in Holocene sediments (see chapter 2)
206 JP C 2 8
Gerlache Strait M S: Q P i M ro n % Cr* C2- (% o 2 C2* . 3 % s 5 : 2 - =5 Crq 1 (670 mbsl) a <§: % I. o ï r g S' i r 2 - §- %" (% a R- .£3 3 S'I f |- % 5=. S3 I I- (% S; (N = 272) 5; S' -o- “D“ O 8 O O oe o
o o g O8
o o § 8 o 8 8 o o O o o 8 O 0 o O 8 0 0 9 O o o o Ç> OV - o ° o O 8 O o o o o o O. 8 o O o o "3 o o o
o 0 o o
o o 8 O o o o o o 8 § 0 o o o a o 08 O o o o O 8 o o 1 0 o § g o o o o o o § 0 0 o e o o o a § o 8 8 o o 8 s o o 8
Figure 6.6. Occurrences of foraminifers in JPC28, grouped by their distribution down core. Note the continuous record of M. arenacea and T. intermedia and the increasing number of species down core. 207 JP C 28 BFAR Diversity Gerlache Strait (670 mbsl) (# cm’kyr') (# species / sample)
100 1000 10000
(N = 272)
- 0.5
T3
- 2.5
10 -
B. - 3.5
12 -
14-1 4.5
Figure 6.7. Records of benthic foraminiferal accumulation rates (BFAR) and diversity from the Gerlache Strait (JPC28). Reference lines indicate modem values in surface samples from the nearby Andvord drift. Black lines indicate four-point smoothing. The mid-/late Holocene boundary (Domack et al., in press) is indicated.
208 Maximum diversity in core JPC28 was noted around 12 m core depth. Above 4.5 m most samples contain only three species or less. Modem values from surface samples were not available for the purpose of this study. Since the diversities, and maximum and average BFAR values of JPC18 from Andvord drift and JPC28 from Gerlache Strait are remarkably similar, it is assumed that this may be tme in the case of modem assemblages as welL The BFAR of JPC28 from the Gerlache Strait thus appear notably elevated, compared with modem values from surface samples from the nearby Andvord drift.
Principal component analvsis
Andvord drift
The Late Holocene foraminiferal faunas from core JPC18 of the Andvord drift were grouped into three Q-mode and two R-mode assemblages. The Q-mode component model explains 90.96 % of the total variance within the data. In contrast, the R-mode component model explains only 41.06 % of the total variance within the data. Principal component scores for Q-mode fatmas and principal component loadings for R-mode faimas are listed in table 6.2. The resulting assemblages were named after their most dominant species. Down-core fluctuations of the resulting Q- and R-mode assemblages are presented in figures 6.8 and 6.9 and listed in appendices F and G.
209 JPC18 Andvord Drift
Q-mode assemblages R-mode assemblages
Species QPCl QPC2 QPC3 RPCl RPC2 RPC3
Astrononion echolsi -0.40 -0.29 -0.37 -0.05 0.05 -0.49 Bolivina pseudopmctaSa -0.33 -0.29 -0.37 0.69 0.32 -0.23 Bulimina aculeata -0.36 -0.28 -0.37 0.85 0.07 0.10 EpietomineUa exigua -0.40 -0.37 -0.38 0.75 0.06 0.23 Funertkoina earlandi -0.34 -0.36 -0.38 0.67 0.50 -0.26 Fursenkoina fits^ormis 1 3^1 -0.07 -0.10 0.30 0.84 -0.02 Globocassidulina biora 0.19 0.02 0.37 0.10 0.79 0.12 Globocassidulina crassa rossensis -0.38 -0.35 -0.33 0.39 0.59 0.11 Miliammina arenacea -0.27 -0.19 1 3.25 1 0.01 -0.02 1 0 6 S | Neogloboquadrina pachyderma -0.32 -0.37 -0.37 -0.04 0.27 0.44 tfonianella bradii -0.35 -0.36 -0.38 0.02 CÜE 0.15 Nonionella iridea -0.09 -0.41 -0.40 0.10 0.57 0.01 Trochammina intermedia -0.25 1 3.30 1 -0.17 -0.01 -0.14 -0.56
variance explained (%) 42.02 29.08 17.83 18.97 22.09 10.73
Table 6.2. Spades composition of Late Holocene foraminiferal Q-mode and R-mode assemblages of core JPC 18 from the Andvord Drift. Principal Component No., dominant and important associated species (outlined) are given.
210 JP C 1 8 Andvord drift (400 m bsl, N = 212)
Q -m ode P C I Q -m ode PC 2 Q-m ode PC 3 F. fusiformis T. intermedia M. arenacea (PC loading) (PC loading) (PC loading)
-0^ 0.2 0.6 l.O - 0.2 02 0.6 1.0 - 0.2 0.2 0.6 1.0
3
14 -
Figure 6.8. Q-mode foraminiferal assemblages (3-component model) from core JPC18 of Andvord Bay. Thicker black lines indicate a six-point smoothing. Loadings higher than 0.4 indicate the dominance of a component. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated.
211 J P C 1 8 R-mode PC I R-mode PC2 Andvord drift B. aculeata F. fusiformis (PC score) (400 m b sl) (PC score) 4■2 0 2 4
(N = 2 I2 ) - I
- 2
- 3
- 4
m
S) <
12 - ^ 7
14 - - 8
16 - - 9
18 - 10
II 20
Figure 6.9. R-mode foraminiferal assemblages (3-component model) from core JPC18 of Andvord drift. Thicker black lines indicate a four-point smoothing. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated. Note high scores oïB. aculeata (RPCl) in the Late Holocene.
2 1 2 The first component of the Q-mode model of JPC18, the F. fusiformis assemblage
(QPCl), explains 42.02 % of the total variance within the data. Other important associated species are not present. The down core distribution of this component is characterized by high frequency fluctuations showing two maxima between 6 and 8 m core depth (Fig. 6.8). The T. intermedia assemblage (QPC2) accounts for 29.08 % o f the total variance. Further important species besides T. intermedia were not encoimtered.
Peak values of this assemblage occurred in the upper 9 m of JPC18. The Af. arenacea assemblage (QPC3) explains 17.83 % of the variance and appears monospecific. The down core distribution of this component reveals no apparent trends.
The first component of the R-mode model of JPC18, the B. aculeata assemblage, explains 18.97 % of the total variance within the data. Important associated species areE. exigua, B. pseudopunctata and F. earlandi. Three peaks of this assemblage are recorded in JPC18 at 2.8, 4.4, and 6.2 m core depth (Fig. 6.10). The second component, the F. fusiformis (RPC2) assemblage describes 22.09 % of the total variance. G. biora and N. pachyderma are important constituents. F. fusiformis (RPC2) is similar in down core distribution to the F. fusiformis (QPCl) assemblage defined above, maxima are present at
6.5 and 8 m core depth.
Gerlache Strait
The Late Holocene foraminiferal faunas firom core JPC28 were grouped into three
Q-mode and two R-mode assemblages. The Q-mode component model explains 87.88 % of the total variance within the data. In contrast, the R-mode component model explains only 28.97 % of the total variance within the data. Principal component scores for Q-
213 mode faunas and principal component loadings for R-mode faunas are listed in table 6.3.
The resulting assemblages were named after their most dominant species. Down-core fluctuations of the resulting Q- and R-mode assemblages are presented in figures 6.10 and 6.11.
The first component of the Q-mode model of JPC28, the T. intermedia assemblage (QPCl), explains 35.66 % of the total variance within the data. Other important species are not present. The down core distribution of this component is characterized by high frequency fluctuations with a trend towards higher values between
6 and 11.5 m core depth (Fig. 6.10). Above 5.5 m core depth the T. intermedia (QPCl) assemblage is rare. 34.87 % of the variance are explained by the F. fusiformis assemblage
(QPC2). Further important species were not encountered. F. fusiformis (QPC2) is mostly absent in the upper 4.5 m, the section firom 4.5 to 9 m core depth shows regularly spaced fluctuations. From 9 to 13 m core depth F. fusiformis (QPC2) increases down core with a apparent cyclicity. The M. arenacea assemblage (QPC3) accounts for 17.46 % o f the total variance. Similar to the first two components, QPC3 appears monospecific as well
The down core distribution of this component reveals no apparent trends, high values are common throughout the core.
214 JPC28 Gerlache Strait
Q-mode assemblages R-mode assemblages
Species QPCl QPC2 QPC3 RPCl RPC2
Astrononion echolsi -0.32 -0.44 -034 Bolivina pseudopunctata -0.26 -0.11 -0.17 Bulimina aculeata -0 J2 -0.45 -0.14
C ibicides sp. -033 -0.44 -037 - 0.02 Epistominella exigua -035 -034 -036 Fursenkoina fiisifomds -038 0 Ü ] -0.17 Globocassidulina biora -030 -031 -034 Globocassidulina crassa rossensis -0.33 -0.46 -036 Miliammina arenacea 0.08 -0.07 1 3 47 1 Neogloboquadrina pachyderma -0.33 -0.43 -037 Nonionella bradii -034 -037 -033 Nonionella iridea -033 0.31 -0.39 0.05 Trifarina angulosa -0.34 -0.44 -039 Trochammina mtermedia [S] -0.03 -0.34
variance e:qilained (%) 35.66 34.87 17.46 16.20 12.77
Table 6.3. Species composition of Late Holocene foraminifeiral Q-mode and R-mode assemblages of core JPC18 from the Andvord Drift. Principal Component No., dominant and important associated species (outlined) are given.
215 JP C 28 Gerlache Strait (670 mbsl, N = 272)
Q-mode P C I Q-mode PC 2 Q -m ode PC 3 T. intermedia F. fusiformis M. arenacea (PC loading) (PC loading) (PC loading)
-0.2 0J2 0.6 1.0 -QJ2 0 2 0.6 1.0 - 0.2 0.2 0.6 1.0 0
1
2
3
4
5
O 6 CO
7
- 2.5 8
9
10
- 3.5 11
12
13
4.5 14
Figure 6.10. Q-mode foraminiferal assemblages (3-component model) from core JPC28 of Gerlache Strait. Thicker black lines indicate a six-point smoothing. Loadings higher than 0.4 indicate the dominance of a component. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack et al., in press) indicated. Loadings higher than 0.4 indicate the dominance o f a component.
216 JPC28 R-mode PCI R-mode PC2 Gerlache Strait F. fusiformis B. aculeata (PC score) (PC score) (670 mbs) jy 0 2 jy 0 2
- 0.5 (N = 272)
P n 3 a . ■ao
- 2.5
10 -
- 3.5
12 -
14 -* 4.5
Figure 6.11. R-mode foraminiferal assemblages (2-component model) from core JPC28 of Gerlache Strait. Thicker black lines indicate a four-point smoothing. The proposed age model is given for comparison, with the mid-/late Holocene boundary (Domack at al., in press) indicated. Note high scores of B. aculeata (RPC2) during the late Holocene and latest mid-Holocene.
217 The first component of the R-mode model, F. fusiformis (RPCl), describes 16.2
% o f the total variance. N. iridea and N. bradii are important associated species. The
down core distribution in JPC28 suggests mayimiim activity of this assemblage at 10 m
and between 12 and 13.2 m core depth (Fig. 6.11). The B. aculeata assemblage (RPC2),
including N. pachyderma and B. pseudopunctata as important associated species,
describes 12.77 % of the total variance. The down core record of this assemblage is
characterized by peaks at 5.5 m, 9.8 m and 10.5 m core depth.
6.5. Discussion & Conclusions
The age model of OOP core 1098 (Palmer Deep basin I) was applied to JPC 18
(Andvord drift) and JPC28 (Gerlache Strait) through correlation of the magnetic
susceptibility data. The dry weight values of JPC 18 and 28 indicate that sedimentation
processes did not change .significantly over times. It can thus be assumed that the age
models presented herein give a good approximation. Nevertheless, it has to be kept in
mind that the benthic foraminiferal accumulation rates (BFAR), utilized in the following
as a paleoclimate proxy, were calculated with average sedimentation rates derived firom
the preliminary age models.
BFAR and Diversity
The foraminiferal assemblages in cores JPC 18 and JPC28 appear to be similar in composition and spatial extent. One major difference is the increased importance of G. biora in JPC18 in the Andvord drift. Since this site is shallower (~ 400 m) than the site in
218 the Gerlache Strait (JPC28 ~ 670 m) it may indicate a preferred water depth habitat for G. biora. G. biora was very rare in surface samples deeper than 400 m in the study area (see chapter 2). The overwhelming dominance of only a few species in both cores is remarkable. F. fusiformis alone accounts for 55 and 40 % of the total number of tests counted in JPC18 and JPC28, respectively, corroborating its ability to occur in large numbers.
The agglutinated species S. bifomds and P. eltaninae were omitted from the data set, since their down core distribution pattern is likely influenced by disintegration (for discussion see chapter 2).
The calculated benthic foraminiferal accumulation rates (BFAR) and diversity (# o f species) o f JPC18 from Andvord drift and JPC28 from Gerlache Strait have been plotted against the preliminary age model in figure 6.12. A smoothing function (running average of every four samples) has been applied to the BFAR and diversity to allow visualization of long term trends.
The calculated sedimentation rates of 0.18 cm yr'^ for JPC18 from Andvord drift are in good agreement with 210^ profiles from core top samples from Andvord Bay, ranging from 0.15 to 0.18 cm yr"^ (Domack & McLennan, 1996). Changes in lithology are mino r in JPC 18; thus, it is assumed that the BFAR calculated herein may serve as a good approximation. Radiometric controlled sedimentation rates from the Gerlache Strait are presently unavailable. The average rate for JPC28 from the Gerlache Strait calculated in this study of 0.3 cm yr'*^ is at the upper limit of values based on C'^'* profiles from the nearby Andvord Bay (Domack & McLennan, 1996).
219 BFAR Diversity
(# cm'kyr’ ) (# species / sample) 10 1000 I00000
«
Benthic Optimum
JPC28 JPC28 Gerlache Strait Gerlache Strait
. JPC18 _ Andvord drift
10 -
100 1000 10000 0 2 4 6 8
Figure 6.12. BFAR and. diversity from the Andvord Drift and Gerlache Strait plotted against the preliminary age model. Lines have been smoothed by four-point running average, references lines indicate modem values from surface samples in the Andvord drift. The Holocene climatic optimum defined in this study lasted from 4.5 to 2.5 ky BP, as indicated by high BFAR and diversity values. Rather than an abrupt event, the optimum appears to have been a gradual process, expressed for example in the gradual decrease o f the BFAR from the Gerlache Strait.
220 The modem benthic foraminiferal accumulation rates (BFAR) in the Andvord
drift (derived from the surface samples) seem to present a lower limit for the last 5.8 ky.
It would imply that the recent warming observed in the study area (e.g. Leventer et al.
1996) did not result in higher benthic productivity. A possible explanation may be a
response time in the trophic system to a warm period. As judged by the high frequency
fluctuations of the BFAR, higher benthic productivity than today presumably occurred
during much of the Holocene. The last higher value in the BFAR occurred approximately
400 years ago. The Little Ice Age (LIA), a cold period, which occurred shortly
afterwards, may be responsible for the decline of the BFAR during the last 400 years.
The diversity seems to follow the BFAR trends. High BFAR values are
accompanied by high diversity values and vice versa. The main difference is that the
Holocene diversity was mostly lower than the values calculated from modem
assemblages of the Andvord drift. It may be that the enhanced modem diversity is the
first impact of the recent w a rm ing in the study area. It is also possible that disintegration
processes are responsible for the depleted Holocene assemblages, although all data sets
were adjusted by the removal of agglutinated species with low preservation potential
BFAR values have been used as a simple tool for estimating the primary
productivity (Herguera & Berger, 1991; McCorkle et al., 1994). It seems that BFAR
values are directly correlated to primary productivity in the surface waters, with higher
productivity resulting in more food for the benthic communities and subsequently, higher
diversity and BFAR values. More persistent annual sea-ice reduces the primary
productivity by limiting hght penetration, periods of warming result in a melt-water induced stratification with enhanced primary productivity (Leventer et al., 1996). Under
221 these assumptions, it appears that the primary productivity over the Andvord drift and
Gerlache Strait today is relatively low, compared with conditions in the past. Namely, the period from 4.5 to 3 ky BP must have experienced considerably higher productivity, as indicated by high BFAR and diversity values in JPG18 and 28.
Statistical Analysis
The Q-mode faunas in core JPC 18 and 28 appear similar in composition, and, after applying the age model, similar in their distribution through time. F. fusiformis
(QPCl) from JPC18 of the Andvord drift is equivalent to F. fusiformis (QPC2) from
JPC28, both assemblages contain no additional dominant species.
In chapter 2 it was predicted that the F. fusiformis assemblage of the biocoenoses, which occupied the Andvord drift during March 1998, is likely to appear monospecific in the fossil record. R. subdentaliniformis is an important part of the biocoenoses in the
Andvord drift, but this species disintegrates rapidly down core. The reason for the lack of stability of agglutinated species was discussed im chapter 4, and is likely linked with the iron-bearing wall in species like R. subdentaliniformis.
As pointed out in chapter 2, F. fusiformis- (sometimes referred to as S. fusiformis) was reported as an opportunistic species in tenrporarily anoxic environments such as in
Norwegian Qords (Alve & Nagy, 1990). It is remarkable in its ability to occur in extremely high abundances following anoxic events (Jorissen et al., 1992). The data presented in this research provides additional evidence for the capacity of F. fusiformis to occur in large numbers when conditions are suitable.
222 Ishman & Domack (1994) linked ±e intrusions of the WSTW into the study area with the occurrence of a Fursenkoina spp. assemblage. It would imply that the influence of the WSTW was strongest during the late mid-Holocene in the Andvord drift and
Gerlache Strait (Fig. 6.13).
A dominant feature in the interval from 4.5 to 3 ky BP is the cyclic change of the
WSTW faunas (F. fusiformis assemblage), supporting earlier studies of 200-300 year cycles in the Andvord Bay (Domack et al., 1993) and the Palmer Deep (Leventer et at.,
1996, Domack & Mayewski, 1999). The WSTW faunas decrease from a maximum at 4.5 ky BP.
T. intermedia (QPC2) from JPC18 in the Andvord Drift is identical in composition to the T. intermedia (QPCl) assemblage from JPC28 in the Gerlache Strait
(Tables 6.2 & 6.3). Both contain no further associated species. Surface samples from the study area revealed that T. intermedia is accompanied by S. biformis and P. eltaninae in the Andvord Drift (see chapter 2). The latter species are agglutinated taxa with a low preservation potential, thus their distribution down core is primarily influenced by disintegration rather than ecological changes. Not as much is known about ecological preferences of those species. The absence of eutrophic foraminifers in the T. intermedia assemblage indicates that it was dominant when the organic flux was too low for other species to flourish. Conditions leading to a low organic flux may be an annual more persistent sea ice cover with reduced primary productivity, resulting in a low organic flux to the seafloor. The ability of T. intermedia to live during times of restricted food supply
223 WSTW faunas CDW faunas F. fusiformis B. aculeata (PC loading) (PC scores)
- 0.2 0.2 0.6 1.0 0 1 2 3 4
Benthic Optimum
OQ Gerlache Strait Gerlache Strait
Andvord drift Andvord drift
10 -
0.6 1.0
Fig. 6.13. Down-core fluctuations of WSTW and CDW faunas from the Andvord drift (JPC18) and southern Gerlache Strait (JPC28). Mid-/late Holocene boundary as proposed by Domack et al. (in press) in the Palmer Deep is indicated. Lines have been smoothed by six-point (WSTW faunas) and four-point average (CDW faunas). The Holocene climatic optimum, as suggested in this study, is characterized by high PC loadings of WSTW fauna from 4.5 — 2.5 ky BP.
224 would perhaps explain the fact that almost all Holocene samples from JPC18 and JPC28 contain specimens of this species. Until results from a seasonal study of benthic foraminifers from the Antarctic Peninsula become available, the assumed ecological preferences of T. intermedia remain unproven. For the time being it wiH be assumed that the dominance of the T. intermedia assemblage indicates a limited organic flux, presumably caused by a persistent sea ice cover.
Figure 6.13. shows that the T. intermedia assemblage was dominant during most of the Late Holocene, whereas the climatic optimum is characterized by low loadings.
Prior to 6 ky BP the influence of the T. intermedia assemblages seems to be uniformly low, which may however be an artifact of the statistical analysis. Many samples dominated by T. intermedia in the lower part of core JPC18 could not used for the principal component analysis due to insufficient total numbers of foraminifers.
Furthermore, the fluctuations of the T. intermedia assemblage are not well matched in
JPC18 and JPC28, presumably also caused by the generally low numbers of T. intermedia. Minor changes in absolute numbers hence produce large differences in the statistical analyses.
Af. arenacea (QPC3) from JPC18 of Andvord Bay matches the Af. arencaea
(QPC3) from JPC28 of Gerlache Strait. Similar to the first two Q-mode assemblages defined in this study, the M. arenacea assemblage is monospecific with no additional associated species. The surface samples of the Andvord Drift showed abundant dead, but very few live (stained with Rose Bengal for recognition of protoplasm) specimens of Af. arenacea, providing an important hint that this species is reproducing at a different time
225 in the year (see chapter 2). Af. arenacea was linked to the extent of the High Saline Shelf
Water (HSSW, Murray, 1991). Other species of this genus are known to live in hypersaline conditions as w ell Such extreme salinities are usually uninhabitable by open marine foraminifers, and F. fusiformis was reported to be especially sensitive towards salinity fluctuations (Murray, 1991). It was thus adapted as a working hypothesis that the
Af. arenacea assemblage dominates in the fossil record during times of high salinities in the deep water. Figure 6.8 shows that the Af. arenacea assemblage is characterized by high frequency fluctuations with a few peaks in the late Holocene. However, low numbers and no apparent match between JPC18 and JPC28 imply the same limitations as with the T. intermedia assemblage.
In conclusion, the overall low numbers of T. intermedia and Af. arenacea limit the utility for statistical analysis of those species. The F. fusiformis assemblage is assumed to provide a detailed record of the intrusion of the WSTW into the study area, with a climatic optimum from 4.5 ky BP and an apparent cyclicity of 200-300 years.
R-mode analysis
R-mode Principal Component Analysis (RPCA) was applied to the data set to recognize foraminiferal assemblages that contain significant but rare species. Due to the high dominance of F. fusiformis, the R-mode F. fusiformis (RPC2) assemblage is basically the Q-mode F. fusiformis assemblage plus the associated species G. biora and
N. bradWiridea. The F. fusiformis (RPC2) assemblage has as similar distribution in time as the F. fusiformis Q-mode assemblage.
226 The occurrence of a B. aculeata R-mode assemblage in JPC18 and JPC28, consisting of B. aculeata, B. pseudopunctata and E. exigua and F. earlandi in the
Andvord drift, and N. pachyderma in the Gerlache Strait seems significant. E. exigua was reported fi’om many regions as an opportunistic phytodetritus-feeder which occurs in large numbers during food pulses (Murray, 1991; Mackensen et al. 1993, Gooday, 1993,
Schmiedl et al., 1997). However, E. exigua is present in very limited numbers.
The B. aculeata assemblage is currently present in the Palmer Deep, and thought to be adapted to the warm and productive CDW (Ishman & Domack, 1994, this dissertation, chapter 5). The R-mode analysis thus suggests intrusions of the CDW into
Andvord drift and Gerlache Strait on at least two occasions during the last 3.5 ky. The fluctuations of the CDW faunas are not well matched in JPC 18 and JPC28, but seem to indicate a strong influence of the CDW around 1.7, 2.5, and 3.5 ky BP. Therefore, the findings of Domack et al. (1993) of R aculeata, N. pachyderma, and Fursenkoina spp. at
1.6 and 2.6 ky BP from the central basin of Andvord Bay seem significant.
Palenclimate Svnthesis
The timing of the deglaciation is not well known in the study area (Ingolfrson et al., 1998). Some of the iimer shelf of the northern Antarctic Peninsula areas was deglaciated as late as 8 to 6 ky BP (Herron & Anderson, 1990; Pudsey et al., 1994).
There are indications of mid-Holocene glacial readvance on James Ross Island on the eastern side of the Antarctic Peninsula between 5 and 4.5 ky BP (Hjort et al., 1997), and from Lallemand Qord between 6 and 5 ky BP (Shevenell et al., 1996). From Brabant
227 Island, 100 km to the north of the Andvord drift, glacial expansions have been described culminating at 5.3 ky BP (Hansom & Flint, 1989). The climate of the last 4 ky appears to have been quite variable. From Lallemand Çord a climatic optimum was reported between 4.2 and 2.7 ky BP (Shevenell et aL, 1996). Leventer et al. (1996) suggested warmer conditions prior to 2.6 ky BP in the Palmer Deep. Recent research from Domack et al. (in press.) reported the onset of colder conditions ("Neoglacial') in the Palmer Deep at 3.4 ky BP. The reason for this discrepancy may be by the suggestion of Leventer et al. that their record could be incomplete due to core loss during recovery. Pudsey et al.
(1994) recognized elevated biogenic sedimentation west of the Palmer Deep between 6.4 and 3.9 ky BP. In Andvord Bay, a high resolution Qord (ice proximal) record shows peaks of enhanced organic matter preservation prior to 2.2 ky BP (Mashiotta, 1992). In the South Shetland Islands to the north of the smdy area warmer and more humid conditions were reported (Yoon et al., 2000). In the South Shetland Islands the warmer conditions seem to have continued over the last 2.7 ky BP (Yoon et al., 2000).
The record of the Andvord drift presented in this research presumably covers the last 11 ky BP. A simple correlation with a tie point at 3.4 ky BP was utilized to establish an age model for core JPC18 from the Andvord drift. The lower two thirds o f the
Andvord drift record may thus require considerable modification in the age model after detailed radiochronology data become available. The ages of events from the mid-
Holocene given in the following should be considered preliminary.
The conditions in the Andvord drift were quite variable from 11 to 7.2 ky BP Fig.
6.15), as indicated by high frequency fluctuations of BFAR, probably due to periodic intrusions of WSTW with subsequent blooming of F. fusiformis. Another possibility
228 would be fluctuating sedimentation-rates, which would produce a sim ilar pattern. Most assemblages from 11 to 7.2 ky BP are restricted to T. intermedia, presumably due to a more persistent sea ice cover during most o f the early Holocene.
Between 7.2 and 5.7 ky BP the conditions appear unfavorable for benthic foraminifers. BFAR values drop below the modem level, the WSTW indicator F. fusiformis is very rare or absent. It is suggested that a permanent sea ice cover during this time prevented the occurrence of diverse benthic assemblages, equivalent to reports of glacial readvance in the Antarctic Peninsula between 6 and 5 ky BP.
The optimum was a rather gradual process with elevated BFAR, diversity and
WSTW fauna values from 5.7 to 2.5 ky BP. The mid-/late Holocene transition is therefore not clearly defined in the Andvord drift and Gerlache Strait.
An apparent 200-300 years cyclicity is evident in the WSTW faunas within the climatic optimum. Peaks of BFAR, diversity and WSTW faunas occurred between 4.5 and 2.5 ky BP, and is here considered the climatic optimum in the study area, and an analog to reports of similar warm events in the Antarctic Peninsula (see above). The temperature increase is also seen in the Vostok, Dome C and Byrd ice cores (Johnsenet al., 1972; Jouzel et a/., 1989).
The last 2.5 ky saw declining BFAR, Diversity and WSTW fauna values, pointing to a weaker influence of the WSTW in the study area. The proxies decrease from a last peak at 400 years to the low values that prevail today. That last drop in productivity may be due to the Little Ice Age, which was recognized in the study area as a period of cold conditions and limited biogenic productivity (Domack & Mayewski, 1999, Shevenell et aL, 1996; Domack era/., 1995).
229 Ill
o
O Gerlache Andvord lu Strait drift =? late Holocene mid Holocene
o \8 CN o Age (ky BP)
Benthic Glacial Optimum readvance?
■3 "3-
Gerlache Strait Andvord drift
late Holocene mid Holocene
o O Age (ky BP)
Figure 6.14. Paleoclimate synthesis of the Andvord drift and Gerlache Strait. Lines have been smoothed according to methods used in previous figures. Reference lines indicate modem values o f BFAR and diversity in the Andvord drift.
230 CHAPTER?
POSSIBLE AUTHIGENIC GYPSUM FROM THE PALMER DEEP BASINS
7.1. Summary
Authigenic gypsum is not a common constituent of deep-sea sediments due to the
paucity of Ca^^ and relatively high solubility of SO^ in seawater. Gypsum crystals in
cores from the Palmer Deep are thought to be authigenic, as indicated by the euhedral
crystal shape, the sharp demarcation between gypsum and non-gypsum-bearing layers,
absence of breakage, and association with the foraminiferal assemblage dominated by M.
arenacea.
A laboratory experiment demonstrated that the gypsum is not a curation storage
artifact of pyrite oxidation or resulted from desiccation of the core. A comparison with
gypsum in organic-rich sediments from the Mediterranean Sea suggests that the crystals
of the Palmer Deep formed on the sediment-water interface rather than within the sediment. The proposed mechanism for the origin of the mineral is the generation of hypersalme waters, caused by stormier and cooler austral winter. Consequently, the surface waters increase in density causing it to sink to the seafloor. Given the enclosed nature of the P almer Deep basins it seems possible that hypersaline bottom waters could build up temporarily, resulting in the precipitation of gypsum at the sediment surface.
231 7.2. Introduction
Authigenic (formed or generated in place) gypsum crystals are infrequently reported in marine sediments. Few investigations deal with gypsum from high latitudes, although gypsum is a common mineral in soils from cold regions (Marion & Barren,
1997). Briskin & Schreiber (1978) associated the influx of the corrosive Antarctic
Bottom Water into the Weddell Sea with the production of gypsum on the seafloor. The
CO2 imder-saturated Antarctic Bottom Water was thought to dissolve the foraminiferal ooze, thereby providing the necessary Ca^^ for the precipitation of gypsum. Gypsum has been reported from the Indian Ocean (Vijaykumar & Vaz, 1995) and was linked to dissolution of calcareous foraminifers in organic-rich sediments. The authigenic origin of gypsum is often questioned, because the mineral can also form by dehydration of the of marine sediment cores (Briskin & Schreiber, 1978).
The sediment cores retrieved from the region called the Palmer Deep have received a great deal of attention in the recent past (Kirby et aL, 1998, Rebesco et al.,
1998). Extremely high sedimentation rates associated with rare sediment-flows made the
GDP cores 1098a-c from basin 1 prime material for investigating Holocene climatic fluctuations (e.g. Domack et aL, 1998). During microfossil processing, large (<2mm) unbroken euhedral gypsum crystals were observed in GDP core 1098b (Sperling & GDP
Scientific party, 1999). In many cases, the gypsum crystals occur together with the Af. arenacea assemblage which may be adapted to hypersaline conditions (see chapter 2).
The crystals are tabular euhedral, exhibit abundant twinning features, and are mostly confined to the fraction >125 pm. A few samples yielded lens-like forms. The demarcation between non-gypsum and gypsum-bearing layers is sharp. Inclusions of
232 diatom frustules and spicules in the gypsum crystals are abimdant, however, no gypsum overgrowth of foraminifers or clasts has been observed similar to those described by
Briskin and Schreiber (1978) from the Weddell Sea. Therefore, the evidence indicates that the gypsum crystals in the sediments of the Palmer Deep formed on the sediment- water interface from hypersaline bottom waters.
However, alternative pathways for the generation of gypsum are possible and win be discussed in this chapter. The gypsum may be a curation storage artifact, due to evaporation of interstitial pore water or produced by pyrite oxidation and dissolution of calcareous foraminifers (Schnitker et aL, 1980). Early diagenetic processes in organic rich sediments are also known to result in the production of gypsum (e.g. Passchier et aL,
1997).
7.3. Previously reported gypsum from marine sediments
Reworking
Clastic gypsum has been reported from reworked marine deposits in the Adriatic
Sea (Parea & Ricci-Lucchi, 1972) and in parts of the Sflician Basin (Schreiber et aL,
1976). The gypsum likely formed on land and was transported rapidly enough to prevent total dissolution. Breakage and abrasion are typical features of these deposits since gypsum is a very soft mineral (Briskin & Schreiber 1978). Soils in cold regions such as the Antarctic Peninsula also contain gypsum as a common constituent (e.g. Marion &
Farren, 1997). Redeposition of terrestrial gypsum by glaciers into the Palmer Deep basins appears possible. Signs of breakage or abrasion should be evident if the crystals in ODP
233 core 1098b were the products of such reworking. This is not the case. On the contrary, even fragile crystals with twinning features are perfectly preserved (Fig. 7.1 top). A clastic origin of the Palmer Deep gypsum can thus be excluded.
Precipitation during storage from interstitial solutions
Briskin & Schreiber (1978) described the spontaneous precipitation of gypsum in organic rich sediments from interstitial solutions supersaturated in Ca^^ and 5 0 4 ^'. If the occurrence of gypsum in the ODP cores were a similar artifact, they should occur in intervals of high Ca^^, 8 0 4 ^', and total organic carbon (TOC) concentrations. Pore-water analyses taken onboard the ODP vessel (Fig. 7.1 bottom) show that the crystals are restricted to intervals where Ca^^ and 8 0 4 ^' - concentrations are below the limit of detection. The TOC values are also lower than in the upper part of the core. The pH in this interval is 8 .0 , which is higher than in the upper 2 0 m, suggesting better preservation conditions for calcareous microfossüs. Therefore, the gypsum from the Palmer Deeps is not likely to be the product of precipitation from interstitial solutions.
Post-sampling oxidation of pyrite
Framboidal (raspberry-hke) pyrite crystals are com m on features in the lower half of core 1098b and often occur inside foraminifer tests or on their organic internal linings
(see chapter 3). 8 chnitker et aL (1980) reported the formation of gypsum during the desiccation of stored samples, and suggested that the slow oxidation of pyrite in
234 ODP 1098c Palmer Deep basin I
Calcium Iron pH Sulfate TOC (N = 30) (oM (uM (w e ^ t %) 0 15 0 40 7.6 8.1 0 40 0.0 , I
10 -
20 -
Gypsum in 30 1098b
40 -
Figure 7.1. Top: scanning electron microscope images of euhedral gypsum crystals from ODP core 1098b (28.6 m core depth) from Palmer Deep basin I. Bottom: Profiles of interstitial water chemistry, total organic carbon (TOC) in core 1098c (Barker et aL, 1999) and occurrence of gypsum in core 1098b.
235 the presence of oxygen resulted in the dissolution of calcareous foraminifers. The results
of a soil drainage experiment (Ritsema & Groenenberg, 1993) indicates that after air
enters the sample, Oz oxidizes pyrite, thus producing H 2 SO4 .
4 FeS 2 (s) + 1 5 0 2 (g) + 14 H 2 O ^ 4 Fe(OH) 3 ( 4 + 16 H" (aq> + 8 (1)
The decrease in pH results in the dissolution of carbonate:
CaC03(s) + 2 (aq) Ca^\aq) + H2 O + COz(g) (2)
Ca^^ reacts with sulfate produced by the oxidation o f pyrite to form gypsum:
Ca^+(aq) +S04^aq) + 2 H2 O CaS04 ' 2 H 2 O (s) (3)
The results of Ritsema & Groenenberg (1993) show that if a soil containing carbonate and pyrite remains waterlogged, oxidation of pyrite does not take place. The above reactions wfll take place only after drying o f the soils to allow the intrusion of O 2
Of special note is another result of Ritsema & Groenenberg, who concluded that after 70 days only 0.038% of pyrite was oxidized and only 0.099 % of gypsum was produced. In addition, they determined that at least 10.6 yr are required to oxidize all pyrite if the soil remained waterlogged. If this is true for marine sediments containing calcite and pyrite, substantial production of gypsum should not take place provided that
236 the samples are kept wet and are processed within a few months after the core was
retrieved. This assumption is supported by Schnitker et aL (1980) who noted that undried samples did not develop gypsum. The Palm er Deep samples were stored in watertight containers and processed within 9 months after core recovery. No evidence of
dehydration was observed during processing therefore the Palmer Deep gypsum is probably not a product of pyrite oxidation during core storage.
Early diagenetic formation
Several workers noted gypsum as an apparently authigenic mineral in a variety of non-evaporitic sediments, m ainly in association with reducing conditions (Briskin &
Schreiber, 1978; MuHineaux & Lohmann, 1980). Several mechanisms were postulated for the formation of gypsum, including the dissolution of calcareous fossils by intrusion of corrosive bottom waters and the lowering of the pH in the pore water by bacterial anaerobiosis. Schnitker et al. (1980) pointed out that seawater is undersaturated with respect to gypsum by a factor of about 4 to 5 and that the only plausible sulfate source is oxidation of iron sulfides in the sediment. Schnitker et at. (1980) proposed that the intrusion of oxygen into the sediment by bioturbation or the replacement of stagnant bottom waters by oxygenated waters as possible mechanisms Schnitker et al.'s model may explain this pattern. Oxygenation of sediment layers in the P alme r Deep that were previously below the sulfate reduction zone may have caused an in situ oxidation of pyrite, dissolution of calcareous fossils and precipitation of gypsum. A model of Basberg et at. (1998) provides additional evidence for this scenario, because these authors showed
237 that a pyrite oxidation front results in a calcite dissolution front below it. This mechanism may be responsible for the tmusual porewater chemistry o f core 1098 with an abnormally deep sulfate reduction zone (Barker etal., 1999, fig. 7.1 bottom).
Precipitation from hypersaline bottom waters
When seawater freezes at the surface, the salt content is released into the tmderlying water mass, which consequently increases the water density causing it to sink to the seafloor. Therefore during times of enhanced winter storm activity, which repeatedly breaks up the sea ice, the Palmer Deep basins may be filled with hypersaline waters generated by this process.
A temporary stratification of the water co lum n and subsequent high salinity in the bottom waters seems possible due to the enclosed nature of the Palmer Deep. The absence of calcareous foraminifers such as B. aculeata which live within normal saline salinities from the gypsum bearing layers in 1098b may be explained by the above scenario. Instead, the foraminiferal assemblages in the gypsum-bearing layers are dominated by M. arenacea and T. intermedia. Both belong to genera which are common constituents of hypersaline environments, where calcareous taxa are absent or rare (Sen
Gupta, 1999). M. arenacea was also linked to the extent of the High Saline Shelf Water
(Murray, 1991). Therefore, the foraminiferal evidence supports the hypothesis that the crystals in the Palmer Deep formed by precipitation from hypersaline bottom waters.
238 7.4. Objectives
• The desiccation experiment described below was perffonned in order to find out
whether the gypsum in core 1089b is a storage artifactt derived by the oxidation of
pyrite and dissolution of calcareous foraminifers.
• The comparison of the gypsum in the Palmer Deep w itli gypsum fi-om the sapropels
of the eastern Mediterranean Sea was used to evaluate whether the Antarctic gypsum
formed within the sediment as an early diagenetic prooduct, or precipitated at the
sediment-water interface from hypersaline bottom waters-
7.5. Materials & Methods
The following experiment was performed to test whether the gypsum in ODP core
1089b may be a storage artifact and was derived by the oxidation of pyrite and the concurrent dissolution of calcareous foraminifers. This experiment also yielded information about losses of foraminiferal assemblages during core storage. Core LMG
98/2 KC27 (KC27 hereafter) firom the shallow sill between Palmer Deep basin H and m
(Fig. 7.2) was taken in March 1999. Core PD 92-05 (PD0#5 hereafter) was recovered 7 years earlier at approximately the same place. KC27 is 2.6 m long and sampled in 5 cm intervals 3 months after the cruise. Sediment samples were split, and 5 cm^ of each sample was washed through a 63 pm sieve and investigated for foraminifers and gypsum within one month after sampling. The remaining sample mate=rial was stored in watertight
239 Palmer Deep basins
KC27 / PD05
, Stiufy
; 6 00
64° 30' W 64° 20' W 64° 10’W
Figure 7.2. Bathymetric map of the study area. Dots indicate cores ODP 1098b, LMG98/2 KC27, and PD92-05 (PD05). Map after Leventer etal. (1996).
240 containers to prevent drying. Sixteen months later another 5 cm^ of each sample was taken and processed. The final phase was investigated using material firom core PD05 since time is somewhat limited. By coincidence, the samples received firom core PD05 were completely dehydrated because the containers were not sealed. Rve cm^ of each sample were processed within one week.
7.6. Results
Figure 7 .3 (bottom) shows that processing three months after sampling yielded abundant calcareous foraminifers in the upper part of core K C 27. Gypsum was not found in these samples. Samples processed 16 months later showed somewhat lower foraminiferal numbers, but gypsum was not present. In contrast, every sample firom the dehydrated core PD05 produced gypsum, however the gypsum crystals did not show the typical euhedral form of the specimens in the P alm er Deep core. The crystals in core
PD05 were hard to separate firom the sediment and exhibited irregular shapes, mainly in a rose-like crystal aggregation (Fig. 7 .3 , top). Calcareous foraminifers are present in only one sample at the bottom of the core.
7.7. Discussion & Conclusions
Samples that were stored for 19 months did not yield gypsum and the abundances of calcareous foraminifers did not change appreciably. The gypsum in core PD05 precipitated in rose or concretion-like shapes, which are unlike the large euhedral crystals in core 1098b. The fact that every sample of PD05 generated gypsum is also in contrast with the restriction of the gypsum to certain intervals of core 1098b. Thus, the
241 Processed after
3months 19 months 7 years
K C 27 KC27 PD05 Rotaliina (per cc) Rotaliina (per cc) Rotaliina (per cc) (N = 5 I) (N=51) (N = 3 0 )
0 25 50 0 25 50 0 25 50 0 8 o o o 0.5 o o o o o ? o 3 o c . o 1.5 o o o o o 7 no gypsum no gypsum gypsum ■ o o o o 2.5 o o o o
Figure 7.3. Top: 1, Gypsum of rose-like crystal aggregation from core PD05; 2, Detail picture of 1, showing the diatom frustules in gypsum. Bottom: Abundances of Rotaliina (calcareous foraminifers) and occurrence of gypsum in cores KC27 and PD05 from the sill between Palmer Deep basins II and III. Note that KC27 is 20 cm shorter than PD05. It therefore could not be evaluated whether the single occurrence o f Rotaliina in PD05 at 2.8m has an equivalent in KC27. None of the samples stored in watertight containers and processed within 16 months yielded gypsum. In contrast, gypsum was present in all samples of PD05, which desiccated during 7 years o f storage.
242 experiment provided further evidence that the gypsum from 1098b is not a storage artifact. This being the case, the gypsum has to be of natural authigenic origin, and was derived either from precipitation from seawater or by early diagenetic processes within near-surface sediments.
Sapropels, which are dark, organic-rich sediments, are a common feature of deep- water sediments in the eastern Mediterranean Sea. Most deep-water sediments are poor in organic carbon, making the sapropels easy recognizable features in sediment cores. Kidd et al. (1978) defined sediment layers as sapropels when they are more than 1 cm thick and contain at least 2% organic carbon. Dark, reduced organic matter, pyrite and gypsum crystals are typical components of sapropels (MuHineaux & Lohmann, 1981). The sapropels are enriched in iron and sulfur and are products of bacterial sulfate reduction
(e.g. Passier et al., 1997). The authors proposed that after the available iron in the sapropels was reduced to FeSz, HS diffuses into the layer above. The HS may then react with Ca^^ and O2 in the pore water to form gypsum. After the available oxygen has been used up, more pyrite is formed. The gypsum content of Mediterranean sapropels is therefore considered to be a product of an early diagenesis.
Core MC528 from the Ionian Basin was investigated to compare gypsum of early diagenetic origin with the crystals in the Palmer Deep basins. MC528 yielded large amounts of gypsum and pyrite in the layer that contains the sapropel (Fig. 7.4). The crystal shape of gypsum in MC528 is characterized by its lens-like form, whereas the typical euhedral Palmer Deep variety was not observed. Many of the crystals of MC528 show inclusions of planktic foraminifers or aragonitic pteropods. In several instances, the growth of crystals was impeded by sediment particles.
243 Only three of the Palmer Deep samples displayed the lens-like form. The vast majority of gypsum crystals are euhedral, suggesting a different origin. Imperfect crystals due to overgrowth of clasts or foraminifers are not present. The ideomorphic crystal shape implies the prec^itation in an environment where unrestricted crystal growth was possible, which may have been at the sediment-water surface. The author favors the view that the gypsum observed in 1098b precipitated at the sediment-water surface firom hypersaline waters derived firom the freezing of seawater. Support for this hypothesis is provided by the association of gypsum-bearing layers with Af. arenacea, which may live in hypersaline waters, the euhedral crystal shape, and the failure of euhedral gypsum to form in the laboratory experiments of core desiccation.
The confirmation of gypsum precipitation firom hypersaline seawater hypothesis might be achieved by stable isotope analysis of sulfur. Pyrite in marine sediments is mainly a product of bacterial reduction (Strauss et al., 1997; Raiswell & Canfield, 1998;
Zachara et aL, 1998; Aharon & Fu, 2(XX), Kasten et aL, 2CXX)). Bacteria are known to discriminate against the heavier isotope (Mizutani Sc Rafter, 1973; Habicht et at.,
1998). Values of Ô of pyrite and gypsum derived firom it are therefore mostly heavily altered in comparison to seawater (e.g. Wendorf, 1992). Calcium sulfate is thought to reflect the isotopic composition of the seawater at the time of deposition (Strauss &
Joachimski, 1997). The 6 ^"*S values should be similar to values of seawater if the gypsum crystallized firom hypersahne bottom waters. Lower Ô ^'^S values are expected if in situ pyrite oxidation and dissolution of calcareous fossils was involved.
244 10 mm
MC529 Ionian Basin G. orbicularis B olivina spp. g yp su m (2650 mbsl) (n/g) (n/g) (w t% ) 0 5 10 0.1 03 03 03 1.0 0 N = 15
5
10 ? c3 a . ■§ 15
20
25
30
Figure 7.4. Top: gypsum from core MC529 from the Ionian Sea (eastern Mediterranean Sea). Bottom: dominant calcareous foraminifers and weight percentage of gypsum in core MC529. Position of sapropel SI is indicated.
245 CHAPTERS
SUMMARY
The previous chapters focused on foraminiferal assemblages from the Antarctic
Peninsula, their composition dependent on environmental conditions and postmortem processes, and their mtüity as paleoenvironmental proxies in Holocene sediments.
Additional independent proxies may be provided by chemical analysis of the shells or organic linings of bentSiic foraminifers in future studies as shown by reconnaissance studies in this dissertation. The derived applications, results, conclusions and recommendations for fiitiure research are outlined below.
Goals and intentions of this dissertation changed over the last two years since the dissertation proposal was written. Some problems proved unsolvable at the time (e.g.
Mg/Ca ratios) or incomclusive without further, independent evidence that was not available (e.g. diamicton. in ODP core 1099). Compensation for this was provided by the evaluation of additional cores from the Andvord drift and Gerlache Strait.
246 Questions outlined in the dissertation proposal
From the dissertation proposal (Sperling, 1999):
> “How do the foraminiferal assemblages and the geochemical composition of
foraminiferal tests reflect the most recent increase in annual mean summer
temperature? ... Relative abundances offoraminifera in the sediment reflect climatic
conditions, with higher values, due to enhanced primary productivity, during warmer
periods. Leventer et al. (1996) linked increased glacial melt-water input, due to
warmer atmospheric and sea surface temperatures, to high productivity events.
Furthermore, the composition of assemblages is also dependent on climatic
conditions; immigrants, from permanently sea ice-free areas are expected to appear
in the sediment record during warmer periods. Additional, certain trace metal ratios
of foraminiferal tests may he related to water temperature and/or salinity. ”
> “Are the processes responsible for Mg incorporation in tests o f the benthic
foraminifer Bulimina aculeata temperature-related? Can Mg/Ca ratios of
foraminiferal calcite be used as a paleothermometer ?” Benthic foraminifers live
under the influence o f bottom water masses, which are in general thought to be less
variable in temperature than surface waters. However, the two prevalent water
masses in the study area show differences o f up to 3.7°C (Ishman and Domack, 1994).
Differences in salinity are relatively mirwr. Hastings et al. (1998) linked a 25%
increase in Mg/Ca in planktonic foraminifers tests to a water temperature increase of
247 2.6^C. A combined study of Mg/Ca and 5180 ratios of Bulimina aculeata should
therrfore have the potential to track incursions ofCWDW and WSTW into the Palmer
Basins.
The Mg/Ca composition of modem and fossil specimens of F. fusiformis and B. aculeata was measured (Chapter 3) to address this question. The calculated Mg/Ca ratios of modem tests were similar to those published from other benthic species (Rathbum &
De Deckker, 1997). The Mg contents of fossil specimens were however below below detection limit of the Scanning electron microscope (SEM) interfaced with an energy dispersive X-ray spectrometer (EDS). The originally desired investigation via microprobe, which allows a lower detection limit, could not be carried out at the time due to hardware problems associated with the OSU microprobe.
More conclusive proved the investigations of modem benthic assemblages. Based on CDT profiles collected during the March 1998 field season two prevalent water masses and their associated foraminiferal assemblages were recognized (Fig. 8.1). In the
Gerlache Strait and Andvord drift region the cold Weddell Sea Transitional Water
(WSTW) and the associated F. fusiformis assemblage was present. The Palmer Deep basins are filled with the warm CDW and occupied by the B. aculeata assemblage. In between occurred a mixing zone of water masses and the F. earlandi assemblage. The downcore distribution of a profile across the boundary between the latter two assemblages revealed that abundances of B. aculeata decrease with core depth (Fig. 8.1), pointing to a weakened influence of the CDW over those sites over the last ~ 50 years.
248 Q-mode Faunas Biocoenoses F. fusiformis (PCI) Anvers Island
G33 ..*•* Palmer Deeps f **. F. earlandi Q CDW « 4 V (PC3) o B. pseudopiinctatd'. Mixing zone (PC2) ■■ ^ WSTW
64-30'W 64°00’W 63°30'W 6 3 “00'W G33 0 (440 mbsl) 0
(N = 7) Dead
M. arenacea B. pseiidopct. F earlandi B. aculeata
G34 0 0 0 Dead 1 (N = 7) 9 Liv(
3
4 Deal 5 B. pseudopitnct. B. aculeata P. eltaninae M. arenacea
Figure 8.1. Top: spatial distribution o f biocoenoses in the study area, and proposed deep- water mass distribution. Bottom: downcore distribution o f the most abundant foraminifers in cores G33 andG34.
249 > “What is the nature o f the Climate Optimum ("Hypsithermal") present in the study
area as recorded by foraminifers? Could it be used as a paleoclimatic analog to
conditions expected in the study area during further warming? ... The Climate
Optimum ("Hypsithermal") is still poorly documented in Antarctica (e.g. Domack et
al., 1990) because o f the lack o f suitable exposures on land, though ice-core records
suggest slightly warmer conditions ... If the "Hypsithermal" was indeed experienced
in this area, evidence within the foraminiferal record should be found.”
ODP core 1098b was considered the prime site for answering this problem. It
became clear after the faunal investigations were completed that the record of the mid-
Holocene in core 1098b (-3.4 — 9 ky BP, Domack et al., in press) is open to different
interpretations. The calcareous assemblages are mainly restricted to B. aculaeta, which
has the highest preservation potential The described pattern could therefore be caused by
partial dissolutioiL Cores JPC18 and 28 from the Andvord drift and Gerlache Strait,
respectively, exhibited richer assemblages. The occurrence of the low resistant F. fusiformis in those cores indicated that dissolution did not strongly influence the
calcareous assemblages. The drawback of cores JPC18 and 28 was that detailed
radiochronology data were not available. A simple age model using magnetic
susceptibility data with a tie point at 3.4 ky BP was establish, but the dating uncertainties
about the lower two third (prior to 3.4 ky BP) of the Andvord drift record remained.
Although an absolute time scale could not be established for the Andvord drift record, the
foraminiferal proxies point to rather variable conditions during the mid-Hoiocene, with a climatic optimum in the Andvord drift around 4-2.3 ky BP.
250 > What is the nature of the diamict from Site 1099 and is it synchronous with the
diandct from Site 1098? Rebeso et al. (1998) suggested a latest Pleistocene age for
the diamict in Site 1099, based on seismic data and preliminary sedimentation rates.
During the Last Glacial Maximum a permanent ice cover was proposed, with
grounded ice in Basin 1 and sub-glacial lake conditions in the deeper Basin HI. If the
diamict represents the LGM, fossils should be absent in this section. Alternatively, the
diamict might be due to a mid-Holocene event, caused by higher rates of iceberg
calving. Warmer conditions would stimulate primary productivity and benthic
assemblages as well. A distinction between these two alternatives based on
foraminifers appears possible.
At the time the proposal was written, the clast rich interval was considered a possible diamicton, deposited either by floated or grounded ice (Rebesco et al., 1998) during the Last Glacial Maximum. Radiochronology data of core 1099 were not available. An extrapolation of the 1098 age model via magnetic susceptibility suggested that the deposition of the “diamicton” ended around 10.8 ky BP, more than 2400 years later than in the adjacent Palmer Deep basin I. However, the uncertainties of this simple approach are too large to identify the exact timing or possible hiatuses.
As for the benthic foraminifers, the assemblages are diverse throughout the
“diamicton” (Fig. 8.2). This excludes the possibility of a grounded ice-shelf at that time and points to a warm mid-Holocene event. Benthic foraminifers could presumably live beneath a floating ice shelf, in which case however the primary productivity and thus
251 organic flux to the seafloor would be drastically reduced. The occurrence of the CDW indicator B. aculeata in the mid part of the “diamicton” however contradicts this hypothesis. Another explanation may be Rebesco et a/’s (1998) comment that the deeper
Palmer Deep basin m has a direct connection to the outer shelf via deep channels, and may thus allow a better deep-water circulation than Palmer Deep basin I. In this case the organic material would have been swept in laterally. It would imply important consequences for the interpretation of the extent of the ice shelf if the “diamicton” was indeed deposited during the Last Glacial Maximum. Pope & Anderson (1992) concluded
(controversial with other authors) that a flinging ice shelf extended across parts of the middle shelf during the LGM. The differentiated distribution pattern of the foraminiferal assemblages might be explained by this scheme. There is, however, some evidence that the “diamicton” might be a mass-flow deposit (personal communication E. Domack,
1999). Sedimentological evidence and radiocarbon data are needed before the question of the nature of the diamicton m 1099 can be answered.
252 O D P 1099 Palmer Deep basin DI (1400 mbsl)
(N = 98)
B. aaileata M aænacea F. fiisiformis T. intermedia
50 0 25 50 0 25 50 0 10 I - 1 L 1- - I _i I ■ 1
n o fS Mud Turbidite a .
Diamicton ?
Figure 8.2. Down core distribution of the most abundant benthic foraminifers in core 1099 from Palmer Deep basin DI. Note the differentiated pattern in the “diamicton”,M. arenacea appears evenly distributed, but B. aculeata and F. fusiformis show high frequency fluctuations.
253 8.2. Modem foraminifers
Ecology and preservation potential
Previous chapters showed the importance of the definition of true biocoenoses
and the recognition o f taphonomic alteration of assemblages. The derived conclusions
about seasonal assemblages must be considered preliminary because samples firom only one field season were available. A detailed seasonal study of benthic foraminifers would be of great value for ecological studies. Two biocoenoses are recognized in this study, both of which were present during the field season in March 1998.
The B. aculeata assemblage is recently present in the Palmer Deep area, which is bathed in Circumpolar Deep Water (CDW) during the austral summer (Fig. 8.3). Farther to the north, intrusions of the Weddell Sea Transitional Water occurred according the
CTD profiûtes collected during the 1998 field season. The absence of the B. aculeata assemblage in the north indicates a dependence of this fauna on the warm and productive
CDW. Judging by previously reported water mass distribution (Ishman & Domack,
1994), the WSTW extended further southwards than in previous years, presumably due to accelerated disintegration of the Larsen ice shelf on the eastern side of the Peninsula.
The F. fusiformis assemblage seems to be opportunistic and thrives in environments that may be temporarily anoxic. These conditions seem to prevail in the
Andvord drift and Gerlache Strait, recently bathed in Weddell Sea Transitional Water
(WSTW), where the shallow water depth prevents deep-water circulation and hindering the o^qrgenation of the bottom waters. Despite the low dissolution resistance F. fiisiformis occurred in large numbers in Holocene sediments firom the Andvord drift, suggesting that strong productivity of this particular species may overweight dissolution.
254 WSTW ill Autumn 1 2 3 4 Mesotrophic ■ X - Eutrophic
7 9 10 Winter 7 9 10 7 9 Oligotrophic
n >s 7 9 10 Spring 2 5 8 Eutrophic ■ X - Oligotrophic
Palmer Deep Andvord drift
Figure 8.3. Proposed seasonal assemblages of the Palmer Deep region. I. B. aculeata, 2. B. pseudopunctata, 3. P. eltaninae, 4. B. bulloides, 5. F. earlandi, 6. R. subdentaliniformis, 7. M. arenacea, 8. F. fusiformis, 9. T. intermedia, 10. S. biformis. 255 Two additional assemblages were proposed, but they occur only in the thanatocoenoses. It is proposed that this is due to a strong seasonality of benthic foraminifers in the study area.
The Af. arenacea assemblage occupies the shallower parts of the Palmer Deep and the adjacent Gerlache Strait to the east. Due to proximity to the coast, sea-ice persists longer than over the deep parts of the Palmer Basins. Until more information about ecological preferences of Af. arenacea becomes available, it is suggested that this taxon be used as indicator of hypersaline conditions, which may be generated by the formation of sea-ice which produces Saline Shelf Water (SSW). The excellent preservation potential of Af. arenacea suggested that this assemblage is robust in Holocene sediments.
The T. intermedia assemblage may be adapted to low salinities, which occur during the spring melting of sea-ice. The associated species S. biformis, noted for its ability to live in low salinities, however it has a low preservation potential The T. intermedia assemblage may therefore appear monospecific in the fossil record.
Organic linings
Three different types of linings were recognized, and the taxonomic affinities to the species level were defined by chemical removal of the mineral test of handpicked specimens. The linings observed belong mainly to Trochammina intermedia, which is the first report of linings firom this species to the knowledge of the author. Additionally, the findings of megalospheric and microspheric linings produced by Cibicides lobatulus are considered the first report of linings firom this species firom the Southern Hemisphere.
Future studies of the chemical composition of organic linings are expected to increase our
256 knowledge in the growing field of molecular biology, contributing to long debated issues such as generic and family relationships, classification, evolutionary derivation of major groups, bipolarity of foraminifers, and macro-/ micro-evolution.
Biominineralization in foraminifers
Scanning electron microscope (SEM) interfaced with an energy dispersive X-ray spectrometer (EDS) was used for investigations of external wall composition. The results revealed that iron content is one of the essential factors determining the resistance of agglutinated foraminifers towards postmortem disintegration (preservation potential).
Iron in tests of agglutinated foraminifers is progressively lost after the death of the specimen, resulting in loss of strength, and in case of Haplophragmoides sp., total disintegration. Af. arenacea does not incorporate iron bearing minerals into its shelf providing further evidence that certain foraminifers can select and precçitate wall material specifically. It also suggests that the absence of iron in tests of Af. arenacea is responsible for its outstanding preservation potential in Holocene sediments from the study area.
8.3. Holocene foraminifers
ODP core 1098b was thought to contain a unique Holocene sequence. While this holds true, the correlation and interpretation of the climate proxies cause controversy.
Three out of four proxies identify a "Neoglacial" and a mid-Holocene optimum in the study area, however all three are mainly determined by the productivity of diatoms in the stuface waters and the bottom water flow regime. The fourth proxy, based on benthic
257 foraminifer data presented in this dissertation, has its own strength and weaknesses. As
benthic organisms, they most likely provide a good record of conditions exactly at the
core site, whereas planktic organisms could be swept in or removed laterally. What are
needed here are proxies independent of sedimentation processes. One such proxy may be
stable isotopes ratios (S^*0, ô^^C) of foraminiferal calcite, however the results of such a
study are not available at this time. The 5^*0 ratios of deep-sea foraminifers were
frequently used as a proxy for temperature and salinity. of foraminiferal calcite is
considered a proxy for pakoproductivity (e.g. Mackensen et al., 1993). The drawback is
that calcareous microfossils in the Palmer Deep basin I are rare or absent during the mid-
Holocene. A possible remedy may be provided by the chemical investigations of
foraminiferal linings,
r. intermedia has a thick, resistant inner organic lining (see chapter 4) and
occurred in almost every sample of core 1098. A hiatus-free record of paleoproductivity could therefore be established, if the fractionation processes of carbon isotopes in organic linings follow similar rules as in the foraminiferal calcite. However, such an approach has not been made before and would therefore require extensive precursory investigations beyond the time limits of a dissertation.
The most reliable information that can be derived from the foraminiferal proxies at this time spans the last ~ 6 ky, given the aforementioned open questions about possible dissolution processes and time control The foraminiferal data suggest variable extend of sea ice over the last 3.5 ky BP in the study area (Fig. 8.3). In the Palmer Deep, assemblages vary between CDW faunas and SSW faunas. The CDW intruded occasionally into the Andvord drift area, as indicated by few peaks of B. aculeata during
258 the late Holocene. There is a good correlation between the WSTW faunas (F. fusiformis) in the Andvord drift and the SSW faunas (Af. arenacea) in the Palmer Deep over the last
4 ky, indicating that periods of increased WSTW pushed the CDW northwards. This pattern may be related to oscillating glaciers in the Antarctic Peninsula during the past
2.5 ky (Sudgen & John, 1973, Zale & Karlén, 1989; Clapperton, 1990; Ldpez-Mdrtinezet al., 1996). Prior to 3.5 ky the CDW seemed to have been absent in the Palmer Deep and
Andvord drift regions, the WSTW and SSW were prevalent water masses (Fig 8.5). The possible implications for the mid-Holocene climate are uncertain. The recent warming in the study area did not produce assemblages as they occurred dining the mid-Holocene
“optimum”. It is therefore concluded that, from a micropaleontological point of view, the mid-Holocene can be hardly described as a period of warmer and thus more productive conditions.
8.4. Recommendations and future work
Sampling
The sampling tool chosen is crucial for recovering complete assemblages. Species living at the sediment-water surface may have been lost during recovery with the grab sampler used in this research. There is little evidence that this was actually the case in the samples investigated in this study. One station showed maximum abundances of certain shallow infaiinal species at the very top (Fig. 2.10), which might be explained by loss of the uppermost sediment centimeter. The use of a professionally build multiple corer such as the Bamett-Watson multiple corer is recommended to avoid similar pitfalls.
259 C D W faunas W S T W /S S W faunas B. aculeata F. fusiformis/ M. arenacea (PC loadings) (PC loadings)
- 0.2 0.2 0.6 1 - 0.2 0.2 0.6 1
0.4 -
0.8 - Palmer Deep basin I 12 - Palmer Deep * basin I
1.6 -
2.4 -
Andvord drift
3.6 - Andvord drift
4.4 -
4.8 -
5.2 -
5.6 -
I 0 I 2 3 4 (PC scores)
Figure 8.4. Comparison o f the 1098 record from Palmer Deep basin I with the Andvord drift record (JPC18, see chapter 18). Note that activity of the CDW indicator B. aculeata is confined to the late Holocene in both locations. During the mid-Holocene, the Weddell Sea Transitional Water (WSTW) and Saline Shelf Water (SSW) were prevalent in the study area, as indicated byF. fusiformis and M. arenacea, respectively.
26 0 Lalleraand Palmer Deep Palmer Deep Andvord South Livingstone Fjord basin I basin I drift Shetland Island diatoms diatoms foraminifers foraminifers Islands 1 5
Neoslacial lower Cooling, productivity warm instability Lowered occasional Transition to productivity CDW humid colder conditions Sea ice diatom More assemblage persistent low cold sea-ice? productivity conditions low benthic Lower persistent depostion productivity pr^uctirit\ sea-ice of till Slightly cover? colder SSW, few an.timu incursions of CDW
10000 - Climatic Reversal 11000 -
12000 Ice breakup First o foraminifers 13000 - =0 U 14000 - Deglaciation
Figure 8.5. Synthesis and comparison with other climate records. 1. Shevenell et al. (1996), 2. Taylor & Sjunneskog (submitted), Sjunneskog & Taylor (submitted), Domack et at. (in press), 3. this study (Chapter 5), 4. this study (chapter 6), Yoon et al. (2000), Bjôrck et al. (1991).
261 This corer is recognized as the “best device available for general sampling of open-marine, soft bottom sediments at present” (Blomqvist, 1991) and is able to recover a virtually imdisturbed sediment water interface (Gooday, 1993). An additional advantage of the Bamett-Watson multiple corer is that this device is able to recover even light and easily dispersed phytodetrius. The content of phytodetrius in the sediment water interface is directly proportional to the primary productivity in the surface waters (Gooday, 1993).
Phytodetrius is thought to be the main food source of many foraminiferal species in the study area. A quantitative investigation may confirm the phytodetrius feeding nature of species such as F. fusiformis and B. pseudopunctata, and provide additional information about the cormection between primary productivity in the surface waters and benthic assemblages.
Multiple corers allow a simultaneously recovery of up to 12 cores with a maximum length of 100 cm. Those features allow for a more thorough investigation of in situ disintegration processes, which may proceed well below the 10 cm core depth limit of the grab sampling device. The maximum core length of the multiple corer would be also sufficient to study events of the last 400 years such as the Little Ice Age. There is a crucial gap in the sampling devices used in this research. The grab sampler covers only the upper - 10 cm (last ~ 100 years), whereas the longer hasten- and gravity cores are rather crude devices which may disturb of loose the uppermost sediment layer (more than
10 cm). Magnetic susceptibility profiles showed that core-loss of the hasten- and gravity cores was variable in extent (personal communication S. Brachfeld, 2000).
262 The Bamett-Watson multiple corer would also aid in improving the precision of the radiocarbon dating in the study area. Surface samples are frequently recowered by kasten, piston or box cores for the determination o f the reservoir correction (Antdrews et al., 1999). The authors noted that one hypothesis to explain the anomolowsly old sediment/water interface age is that the coring devices lost some fraction of tbe upper sediment column. The use of a Bamett-Watson multiple corer to recover an imdisturbed sediment/water interface is therefore recommended.
Storage and Processing
Storage and processing can inflict major damage to the foraxniniferal assemblages, as shown in chapter 2 and 7 of this dissertation. Standard methaods are needed to avoid preservational artifacts outlined below.
Samples should be taken onboard and processed immediately. Due to time constraints this is rarely possible, but at least a few samples should be processed onboard after taking back-up samples. The comparison between the back-up samples and the samples processed onboard may allow the evaluation of loss of foraminifers during storage. If storage is necessary, the greatest emphasis should be placed oo sealed containers. Desiccation of the sediment samples may destroy calcareous foramimifers in short time. It is important to note that cold storage may aggravate the problem (S-chnitker et al., 1980). Storage in alcohol solution is recently considered the optimunm, which prevents bacterial activity that may destroy organic matter such as organic cement • of
263 agglutinated foraminifers or internal linings of foraminifers. Storage in formaldehyde may stabilize organic linings (pers. comm, J. Mitchell, 2000) and allow the recovery of complete specimens.
The samples should be processed as soon as possible, and at the same time. If the time difference between the first processed sample and the last one is large, so could be the extent of foraminiferal disintegration. Drying before processing must be avoided. The dry weight, necessary to calculate ‘Torams/g”, can be calculated firom backup samples, if desired. Dispersants such as ’’Calgon” (sodium hexametaphosphate) are frequently used to cleaning, but may cause damage to micro fossils (Hodgkinson, 1991).
The use of a 36 pm sieve is reconunended although the >63 pm fraction has become standard in micropaleontological research over the last decade (e.g. Mackensen et al„ 1990). The 36 - 63 pm fraction may allow a more complete recovery of small phytodetrius feeders such as E. exigua and of foraminiferal linings.
Seasonal sampling
Seasonal studies have been proven to be of great value for trophic investigations elsewhere (e.g. Mayer, 2000), but in the polar setting it involves some difficulties. At least during the winter, sampling through the sea-ice appears possible, which may clarify the hypothesized adaptation of certain foraminiferal assemblages to those conditions.
Sampling during the spring melting may show descend of cold meltwater (“cold tongues”, Domack et aL, 1993) and their impact on the benthic assemblages. Seasonal studies may confirm the hypothesized variations in biocoenoses in the study area.
264 Foraminiferal linings
Linings could be used in the growing field of molecular biology, unraveling issues such as bipolarity of foraminifers, evolution rates, and classification problems.
Molecular investigations of foraminiferal organic tissue have already challenged fimdamental paradigms in foraminiferal research. For instance, the discovery of “naked” foraminifers (Pawlowski et al., 1999) contradicts with the traditional definition of foraminifers as shelled protists. The proposed reclassification of the foraminiferal genus
Miliammina (Fahmi et al., 1997) questions the classical taxonomy based on test composition/structure. Even more impact is expected by the recent discovery of Darling et al. (2000) that morphospecies of planktonic foraminifers defined by the micropaleontologist may not be genetically continuous species with a single environment preference, challenging the traditional extensive use of those morphospecies for paleochmate reconstruction. Since linings are preservable in sediments o f Quaternary ages and older (Stancliffe, 1996), their potential for extending our knowledge of such issues is evident.
Future studies of the chemical composition of organic linings are expected to increase our knowledge in the growing field of molecular biology, contributing to long debated issues such as generic and family relationships, classification, evolutionary derivation of major groups, bipolarity of foraminifers, and macro-/ micro-evolution.
265 Holocene sites
It was previously thought that the Palmer Deep contains a unique Holocene sequence (e.g. Domack et al., in press), but a recent cruise (NBP99/3) showed that thick
Holocene sediment sequences may be common elsewhere around the Antarctic
Peninsula. The Andvord drift, for instance, reaches 50 m of thickness, and may date back to the Last Glacial Maximum (Harris et at., 1999). The upper 20 m have been investigated in this research, and the foraminiferal assemblages are more abundant and diverse than in the adjacent Pahner Deep. Whether this is due to environmental conditions or in situ disintegration of the Palmer Deep assemblages is not knowiL The
Andvord drift and similar sediment accumulations (e.g. northern Gerlache Strait, chapter
5) are therefore prime sites for future Holocene studies. Future quantitative analysis of benthic foraminifers in combination with the development of additional proxies dependent on chemistry of shells and organic linings may help to further decipher the climatic history of the region.
266 A P P E N D IX A
Appendix A: Surface sample locations, environmental parameters, foraminiferal counts, diversity, standing stock, and benthic foraminiferal accumulation rates used in chapter 2 . Sedimentation rates are from Leventer et al. (1996), Domack & McLennan (1996), and Kirby era/. (1998).
267 A ppendix A 1 1 1 Î } i i ; 1 (°S) (°W) (mbsl) (CT) C%o) C%o) mm/yr
G19 Palmer Basin I 64° 51.7 64° 12.4 1030 1.3 3.9
G20 Palmer Basin I 64° 52.8 64° 14.4 810 --- 3.9
G21 Palmer Basin I 64° 53.9 64° 16.4 950 - - - 3.9
G22 Palmer Basin HI 64° 55.0 64° 183 1340 - - - 1.8
G31 Palmer Basin I 64° 50.6 63° 3.8 400 - - - 3.9
G33 Palmer Basin I 64° 52.8 64° 7.9 440 -- - 3.9
G34 Palmer Basin I 64° 54.0 64° 10.0 745 - - - 3.9
G35 Palmer Basin n 64° 55.2 64° 12.1 1296 -- - 13
G37 Palmer Basin n 64° 57.2 64° 163 1270 --- 13
G38 Palmer Basin n 64° 58.2 64° 183 1228 -- - 13
G44 Flandres Bay 64° 56.4 63° 21.7 387 0.9 - - 13 G45 Flandres Bay 64° 0.6 63° 163 585 0.7 3435 0.83 13
G46 Flandres Bay 65° 4.1 63° 10.4 550 0.9 3437 - 13
G48 Palmer Basin I 64° 51.2 64° 12.1 1050 1.3 34.68 - 3.9
G49 Palmer Basin n 64° 55.0 64° 15.7 1380 --- 13
G51 Palmer Basin I 64° 51.7 64° 153 959 - -- 3.9
G52 Palmer Basin I 64° 50.6 63° 133 650 - - - 3.9
G53 Palmer Basin I 64° 49.5 62° 11.4 300 -- - 3.9
G54 Palmer Basin I 64° 49.5 62° 83 270 -- - 3.9
G58 Bismark Strait 64° 47.7 62° 323 281 - - - 1.8
G62 Andvord Bay 64° 45.9 62° 53.9 421 -- - 13 G64 Andvord Bay 64° 463 62° 50.9 490 -03 3430 1.37 13
G65 Andvord Bay 64° 443 62° 47.4 358 -0.6 3430 - 13
G66 Andvord Bay 64° 453 62° 48.7 400 - - - 13
G67 Andvord Bay 64° 46.0 62° 493 430 - - - 13
G68 Andvord Bay 64° 46.7 62° 49.9 431 - -- 13
G69 Andvord Bay 64° 473 62° 50.9 442 -0.7 3430 - 13
G71 Andvord Bay 64° 46.6 62° 48.0 412 -- - 13
G72 Andvord Bay 64° 45.6 62° 47.9 406 -- - 13
G76 Gerladie Strait 64° 45.8 62° 5.6 360 - -- 13
G77 Paradise Harbor 64° 54.8 64° 55.1 222 0.1 34.15 - 1.8
G78 Paradise Harbor 64° 50.9 63° 543 280 --- 1.8
G79 Paradise Harbor 64° 50.4 63° 13 256 - - - 1.8
KC26 Palmer Basin m 64° 56.7 64° 123 1388 - - - 13
KC17 Palmer Basin m 64° 57.1 64° 22.1 1016 - - - 13 KC27 Palmer Basin H 64° 553 64° 16.9 1364 1.3 34.77 - 13
268 A ppendix A I f 1 M f I I I live dead (#^>ecies) (#spectes) Nfaxi yr ' N/cm^ yr'* N/cm? ;
G19 Palmer Baain I 15 953 7 16 0 6.4 4.2 G20 Palmer Basin I 3 910 2 15 0 8.6 8.1 G21 Palmer Basin I 610 1008 13 18 45 10.9 8-5 G22 Palmer Basin m 19 1081 6 17 1 5.0 4.0 G31 Palmer Basin I 138 682 8 16 8 5.2 3.2 G33 Palmer Basin I 144 826 9 19 11 7.0 5.9 G34 Palmer Basin I 105 990 8 23 8 7.9 6.7 G35 Palmer Basin n 4 893 3 17 0 2.9 2.7 G37 Palmer Basin n 379 1823 9 21 28 6.0 3.5 G38 Palmer Basin n 0 1889 0 18 0 5.8 4.4 G44 Flandres Bay 53 561 6 21 4 2.4 2.0 G45 Flandres Bay 4 220 1 8 0 0.8 0.8 G46 Flandres Bay 49 189 12 12 4 0.8 0.7 G48 Palmer Basin I 374 686 19 17 28 7.9 2.9 G49 Palmer Basin n 40 2870 7 19 3 10.5 7.8 G51 Palmer Basin I 155 516 16 22 11 53 4.1 G52 Palmer Basin I 223 1007 14 23 16 7 3 5.9 G53 Palmer Basin I 133 641 15 21 10 8.4 6.4 G54 Palmer Basin I 218 408 8 16 16 5.1 3.8 G58 Bismark Strait 55 254 12 16 4 1.7 1.3 G62 Andvord Bay 117 325 6 11 9 0.9 0.8 G64 Andvord Bay 24 102 6 9 2 03 0-3 G65 Andvord Bay 100 185 12 11 7 0.8 0.7 G66 Andvord Bay 110 149 9 10 10 0.5 03 G67 Andvord Bay 85 210 11 11 6 0.9 0.4 G68 Andvord Bay 44 217 7 9 3 0.9 0.4 G69 Andvord Bay 48 111 7 7 4 0.4 0.3 G71 Andvord Bay 139 240 11 13 10 0.7 0.4 G72 Andvord Bay 73 320 8 11 5 0.4 0.4 G76 Gerladie Strait 36 376 6 14 3 1.9 1.1 G77 Paradise Harbor 85 321 12 13 6 1.7 1.1 G78 Paradise Harbor 117 317 6 12 9 1.5 1.1 G79 Paradise Harbor 194 311 10 14 14 2.1 1.2 KC26 Palmer Basin HI 139 350 9 12 10 4.1 2.9 KC17 Palmer Basin HI 187 953 8 16 14 1.7 1.6 KC27 Palmer Basin H 61 972 7 15 4 4.7 4.3
269 A p pendix A
Biocoenoses
Station G19 G20G21G22G31G33 G34G35 G37G38 G44G45 G46
Adercotryma gC-omerata AmmobacuUtes agglitinans
Astrononion ecAotm — — Bolivina pseudcipunctata 2 406 4 43 68 74 - 147 - 21 4 3 Bulimina aculeata 4 - 80 3 1 15 3 1 135 - 1 Cassidulinoides: parkerianus Cibicides lobatalus - - - - - 1 Cribrostomoidezs sp. Cribrostomoidezs subglobosum Fursenkoina eatjlandi 1 - 76 51 9 ...... Fursenkoinafiixtformis 1 1 3 - 1 1 ------19 Globocassidulina biora Globocassiduliraa crassa rossensis 1 Haplophragmoides canariensis — — 5 — 1 — — — 15 — — — — Haplophragmoides guttifera Haplophragmoides parkerea 2 - 22 - - 1 - - 12 - - - 2 Haplophragmoides pilufera Haplophragmoides sp. Miliammina arenacea 6 Nodosariia spp^. Nonionella bradii
Honionella iridea ----- 21 - - - - -1 Portatrochammzina chaUengeri 1 Portatrochammzina eltaniruie 2-18 4- -1-15---2 Pullerda bulloidies 2 - 59 6-2-2 35 ---- Pullenia subcarinata Reophax dentaEiniformis 3-9161113-2-- Reophax nodulasa 1 ------Reophax subdentalin^ormis 1 - - - 8 3 15 - 16 - 27 - 10 Saccamina sp. Saccorhiza ramzosa Spiroplectammâna biformis Textularia spp. 1 ------2 Trifarina angulasa 1 - - - - - ...... Trochammina intermedia 1 ------1 Trochammina sp .l Trochammina sgi. H 1 - -
270 A ppendix A
Biocoenoses
Station G48 G49 G51 G52 G53 054 G58 G62 G64 G65 G66 067 G68
Adercotryma glomerauz ------1 - 6 2 AmmobacuUtes aggUtirums ------Astrononion echolsi 1 -54144 - - 21-- BoUvina pseudopunctata 94 11 50 40 12 6 28 3 2 18 2 3 3 BuUmina aculeata 20 5712 ------CassiduUnoides parkerianus - ---2----1-- Cibicides lobatulus ------1------Cribrostomoides sp- — — — 1 — — — — — — — Cribrostomoides subglobosum ------1 - 1 - Fursenkoina earlandi 2 - 41 128 67 186 1 ------Fursenkoina fits^ormis 8 - 2 - 1 - 1 91 14 41 92 17 - Globocassidulina biora 2 Globocassidulina crassa rossensis 4-22------Haplophragmoides canariensis 14 - 2 8 ------Haplophragmoides guttifera 9-2------Haplophragmoides parkerea 167 - 45 4 2 2 ------Haplophragmoides pilufera --53------Heplophragmoides sp. Miliammina arenacea 11-23 - - - 17 4 11 6 9 13 Nodosariia spp. ------1 ------Nonionella bradii ------171-- Nonionella iridea 1------Portatrochammina chaUengeri 1------5- Portatrochammina eltaninae 1 1352 1 1 1 - 44 17 8 PuUenia bulloides 2 20 5 1 3------PuUenia subcarinata 1------Reophax derttaliniformis --17 10 57------Reophax nodulosa 5 Reophax subdentaliniformis 4 1 21 13 25 13 3 4 2 9 1 12 9 Saccamina sp. ------1------Saccorhiza ramosa Spiroplectammina biformis ------10 6 Textularia spp. 1-3------211- Trifarina angulosa - - - -11------Trochammina intermedia 28 1- -- --113-43 Trochammina sp. I 5 1 . 3 . ------Trochammina sp. H - - - -1 ------
271 i^pendix A
Biocoenoses
Station G69 071 072 076 077 078 079 K1 K26 K17 K27
Adercotryma glomerata 1 - - - - - 4 - -- Ammobaculites aggUtinarts Astrononion echolsi 1-----3-2-- BoUvina pseudopunctata SLl 7 6 9 12 6 9 11 132 20 Bulimina aculeata ------51 36 21 13 Cassidulinoides parkerianus - - 1 - 4 - 8 - - - - Cibicides lobatulus Cribrostomoides sp. ------10- Cribrostomoides subglobosum ----1------Fursenkoina earlandi ----3-2---- Fursenkoinafitstformis 29 100 4 8 9 23 89 3 Globocassidulitui biora -1----13---- Globocassidulina crassa rossensis - 1 - -12-12- Haplophragmoides canariensis ------16 8 10 1 Haplophragmoides guttifera Haplophragmoides parkerea - - - 1 - 5 11 Hcq>lophragmoides piUrfera Haplophragmoides sp. Miliammina arenacea 7 17 12 16-41--- Nodosariia spp. — — — 1 — — — — — — — Nonionella bradii -2-2------Nonianella iridea -----12----- Portatrochammina chaUengeri -11----2--- Portatrochammina eltaninae 41 1 - 6 - - 33 40 -3 Pullenia bulloides ------15 257 18 Pullenia subcarinata - ----1-4-- Reophax dentaliniformis - - - - 1 - 9 2 4 - Reophax nodulosa ------21 Reophax subdentaUn^ormis - 3 - 18 17 2 142 1 - 1 5 Saccamina sp. ------Saccorhiza ramosa - Spiroplectammina btformis - ---1----- Textularia spp. -2--1------Trifarirui angulosa Trochammina intermedia 1 1 1 - 1 - -11- Trochammina sp.l Trochammina sp. II
272 A ppendix A
Thanatocoenoses
Station G19 G20 G21G22 G31G33 G34 G35 G37338 G44 G45 G46
Adercotryma glomerata Ammobaculites agglitinans ------3 24 7 - - - Astrononion echolsi 4 5 10 - 3 18 14 3 3 4 26 - - Bolivina pseudopunctata 183 102 179 142 27 68 231 106 266 443 7 5 4 Bulimina acuUata 451 456 444 626 11 116 513 567 763 901 20 - - CassiduUnoida parkerianus - - - - 1 ...... Cibicides lobatulus ------7-- Cribrostamaides sp. - - - - 18 1 1 Cribrostomaides subglobosum 3------721-- Fursenkoina earUmdi - 1 - - 19 69 36 - 1 - 7 1 - Funenkoina fusiformis 21 55 4 2 - 10 5 3 1 5 13 6 8 GlobocassiduUna biora Globocassidulina crassa rossensis - - 1 -1 4 3 ---2 -1 Htq?lophragmoides canariensis 2 - 8 1 5 - 2 2 13 22 - - - Haplophragmoides gutt^era 58 - 107 5 107 22 27 - 338 - 6 1 2 Haplophragmoides parkerea 1 - - 7 - - 1 5 13 1- -- Haplophragmoides pilufera - 1 ------Haplophragmoides sp. - — ^ — — — — — — Miliammirta arenacea 49 209 65 20 406 420 69 45 71 53 307 185 142 tfeogloboquadrina pachyderma - 39 14 8 - 6 28 3 7 10 3 - - Hodosariia spp. - - 2 - - 1 - - 2 2 5 - -
Nonionella bradii ------2 - - - - - Honionella iridea - 6-1-84241-1 Portatrochammina challengeri ------1 Ponalrochammina eltaninae 107 25 113 219 13 39 31 90 169 322 7 - 12 Pullenia bulloides 24 4 37 41 - 3 10 28 92 86 - - - Pullenia subcarinam Reophax dentaliniformis 7 8 4 2 12 17 6 6 16 13 9 4 - Reophax nodulosa - - - - 3 ------Reophax subdentalinÿormis 6 - - 3 14 10 20 4 17 10 32 - 8 Saccamina sp. Saccorhiza ramosa - - - _ - - 2 ------Spiroplectammina biformis Textularia spp. 13 531312442--2 Trifarirui angulosa 111 - - 1 1 - 2 - 18 - - Trochammina intermedia 23 26 25 5 51 18 4 21 19 12 60 17 7 Trochammina sp. I - 711-6------Trochammina sp. E
273 ^ p e n d ix A
Thanatocoenoses
Station G48G49 G51G52G53 G54G58 G62G64G65 G66G67 G68
Adercotryma glomerata — — — — — — — 1 — 1 — 55 Ammobaculites agglitinans Astrononion echolsi 7 3 19 27 28 7 2 1 ...... Botivina pseudapunctata 62 386 75 100 23 10 2 3 3 4 3 1 - Bulimina aculeata 163 1460 175 330 10 ------Cassidulinoides parkerianus - - - - . ------1 - Cibicides lobatulus Cribrostomaides sp. Cribrostomaides subglobosum - 6--214------Fursenkoina earlandi 2 - 39 116 166 98 3 ------Fursenkomafitstformis 8 4 4 2 14 2 3 44 19 11 13 3 1 Globocassidulâuz biora - - ...... - - - 1 - - Globocassidulina crassa rossensis Haplophragmoides canariensis 18 4 1 3 3 2 ------Haplophragmoides gutt^era 167 5 56 53 71 36 7 - 1 - - - - Haplophragmoides parkerea - 11 - 1 ------Haplophragmoides pilufera - - 4 10 2 ...... Haplophragmoides sp. 9 - 2 - 4 ...... - - - Miliammina arenacea 11 18 68 273 224 165 182 89 28 104 64 42 49 Neogloboquadrina pachyderma - 13 11 - 7 1 ...... - - Hodosariia spp. - 1 1 1 1 ------Nonionella brada Nonionella iridea 1 1 2 ------Portatrochammina challengeri 3 - --1 --3 3 3 - 13 5 Portatrochammina eltaninae 183 796 31 17 12 22 2 18 - 9 9 18 22 Pullenia bulloides 16 109 10 3 - 2 - ...... Pullenia subcarinata Reophax dentaliniforrrds - 1 10 13 28 19 19 - - - 1 - - Reophax rwdulosa - — — — 9 — — — — — — Reophax subdentaliniformis 2 1 4 5 14 15 10 4 3 4 - 16 20 Saccamina sp. Saccorhiza ramosa - - - 18 9 6 1 ------Spiroplectarronina biformis - - - - - 46 20 14 6 61 62 Textularia spp. 1 33 15 2 - 1 4 1 5 10 6 5 Trifarina angulosa - 5 - 4 1 3 ...... - - Trochammina intermedia 28 26 5 13 26 20 5 112 24 29 41 44 48 Trochammina sp. I 5-38------1-- Trochammina sp. II - - - 1 -......
274 ^ p e n d ix A
Thanatocoenoses
Station G69 G71 G72 G76 G77 G78 G79 K1 K26 K17 K27
Adercotryma glomerata --8 - 1-1 1 0 - - - Ammobaculites agglitinans ------Astrononion echolsi ------3161 Bolivina pseudapunctata -4 1 2 7 8 3 6 241 279 97 Bulimina aculeata ------242 71 348 743 Cassidulinoides parkerianus ------77- Cibicides lobatulus - - 1 - 9 - 12 - - - - Cribrostomaides sp. - 1 - - Cribrostomaides subglobosum Fursenkoina earlandi - - - 1 4 - 6 - --- Fursenkoinafits^ormis 8 36 28 4 40 88 1 - - 2 3 Globocassidulina biora - - - - 6 10 11 Globocassidulina crassa rossensis - 4 - 2 23 2 8 - - - - Haplophragmoides canariensis ------8 5 10 4 Haplophragmoides gutt^era - - - 3 - - - 44 - 139 12 Hlophragmoides parkerea ------1 - - 11 Haplophragmoides pilufera - - - 1 ------Htqtlophragmoides sp. --- - ______Miliammina arenacea 58 60 71 196 79 66 136 83 1 12 11 Neogloboquadrina pachyderma ------5132 Nodosariia spp. ------Nonionella bradii - - - - 4 - 6 - - -- Nonionella iridea - 1 - - - 3 - - - - - Portatrochammina challengeri 129 - - 1 - 4 - - - Portatrochammina eltaninae 9 8 14 3 37 24 2 263 7 89 6 Pullenia bulloides - - - - - 1 - 15 9 44 42 Pullenia subcarinata ------1 - Reophax dentalintformis - 3 - 1 - - - 15 3 4 12 Reophax nodulosa ------1-113 Reophax subdentalin^ormis - 17 27 123 17 - 95 - 4 4 23 Saccamina sp. — - - 1 ------Saccorhiza ramosa ------Spiroplectammina b^ormis 20 37 68 16 67 76 14 42 - - - Textularia spp. 3 45 17 3 3 1 - 7 - - - Trifarina angulosa ------Trochammina intermedia 12 22 76 20 30 41 16 71 - 7 4 Trochammina sp. I ------Trochammina sp. H ------
275 A P P E N D IX B
Appendix B: List of abbreviated benthic foraminiferal systematics for modem and Holocene samples from the Antarctic Peninsula including species name, original citation and SEM images of important species. The list does not include poorly represented species or obviously reworked shallow water forms.
276 Adercotryma glomerata (Brady) = Lituola glomerata Brady, 1887, Annu. Mag. Nat. Hist., ser. 5, 1, p. 433, pit. 20, fig. 1.
Ammobaculites agglitinans (d'Orbigny) = Spirolina agglutinons d'Orbigny, 1846, Foraminiferes Fossiles du Bassin Tertiaire de Vienne (Austriche), p. 137.
Astrononion echolsi Kennett, 1967, Cushman Foundation of Foraminiferal Research Contributions, 18 (3), p. 134, pit. 11, figs. 4-7.
Bolivina pseudapunctata Hoeglund, 1947, Uppsala Univ., ZooL Bidr., 26, p. 273, pit. 24, figs., 5a, 5b.
Bulimina aculeata d'Orbigny, 1826, Annals of Natural Science, Paris, series 1, 7, p. 269.
Cassidulinoides parkerianus (Brady) = Cassidulina parkerianus Brady, 1881, Quarterly Journal of Microscopical Sciences, 21, p. 59.
Cibicides lobatulus (Walter & Jacobs)= Nautilus lobatulus Walker & Jacobs, 1798, in Adams Essays, Kanmacker's eL, p. 642, plate 14, figure 36.
Cribrostomoides spp.
Fursenkoina earlandi (Parr) = Bolivina earlandi Parr, 1950, British Australian and New Zealand Antartic researhc expedition 1929-1931, series B, 5 (6), p. 341, plate 12, figure 21.
Fursenkoina fusiformis (Williamson) = Bulimina pupoides var. fusiformis WiDiamson, 1858, Royal Society of London, p. 63, plate 5, figures 129-130.
Globocassidulina biora (Crespin) = Cassidulina biora Crespin, 1960, Scientific Results of the Tohoku University, series 2 (Geology), special volume 4, p. 28, plate 3, figures 1-10.
Globocassidulina crassa rossensis Kennett, 1967, Cushman Foundation for Foraminiferal Research Contribution, 18 (3), p. 133-135, plate 11, figures 4, 6.
Haplophragmoides canariensis (d'Orbigny) = Nonionia canariensis d'Orbigny, 1839, Hist. Nat. lies Canares, Foraminiferes, voL 2(2), pL 2, fig. 33-34.
Haplophragmoides parkerae (Uchio) = Recurvoidella parkerae Uchio, 1960, Cushman Foundation for Foraminiferal Research Special Publication, 5. 53, plate 1, figures 18, 19.
277 Haplophragmoides spp.
Miliammina arenacea (Chapman) =Milionlina oblonga var. arenacea Chapman, 1916, British Antarctic Expedition 1907-1909, Reports o f the Scientific Investigations, Geology, 2 (3), p. 59, plate 1, figure 7.
Nodosariia spp.
Nonionella bradii (Chapman) =Nonionina scapha var. bradii Chapman, 1916, British Antarctic Expedition 1907-1909, Reports o f the Scientific fiivestigations. Geology, 2 (3), p. 71, plate 5, figure 42.
Nonionella iridea Heron & Earland, 1932, Discovery Report, 4, p. 438, plate 16, figures 14-16.
Portatrochammina challengeri (Jones & Parker) = Trochammina squamata Jones & Parker, 1884, Challenger Expedition 1873-1876, Rept. ZooL, voL 9, p. 337-338, pL 41, fig. 3a-c.
Portatrochammina eltaninae Echols, 1971, Antarctic Research Series, 15, p. 148, plate 8, figures 1, 2.
Pullenia bulloides (d'Orbigny) = Spaeroidina bulloides d'Orbigny, 1826, Annals of Natural Science, Paris, series 1, p. 267
Pullenia subcarinata (d'Orbigny) = Nonionia subcarinata d'Orbigny, 1839, Voyage dans r Amérique Méridionale, Foraminifers, 5 (5), p. 28, plate 5, figures 34, 24.
Reophax dentaliniformis Brady, 1881, Quarterly Journal of Microscopical Sciences, 21, 21, p. 49.
Reophax nodulosa, Brady, 1879, Quarterly Journal of Microscopical Sciences, 21, 19, p. 52.
Reophax subdentaliniformis Parr, 1950, British Australian and New Zealand Antarctic research expedition 1929-1931, series B, 5 (6), p. 269, plate 4, figure 20.
Saccamina sp.
Saccorhiza ramosa (Brady) = Hyperammina ramosa Brady, 1879, Quarterly Journal of Microscopical Sciences, 21, 19, p. 33.
Spiroplectammina biformis (Parker & Jones) =Textulatia agglutinons var. biformis Parker & Jones, 1865, Philosophic Transactions of the Royal Society, p. 155, plate 15, figures 23, 24.
278 Textularia spp.
Trifarina angulosa (Wflliamson) = Uvigerina angulosa, 1858, On the recent foraminifera of Great Britain, London: Ray society, p. 67.
Trochammina intermedia Rhumbler, 1938, Kieler Meeresforschung, 2, p. 186, figures 27a-b.
Trochammina sp. I
Trochammirm sp. II
279 Figure Bl. 1. Portatrochammina eltaninae Echols. 2. Trochammina intermedia Rhumbler. 3. Spiroplectammina biformis (Parker & Jones). 4. Haplophragmoides parkerae (Uchio). 5. Reophax dentaliniformis Brady. 6. Reophax subdentaliniformis Parr. 7. Miliammina arenacea (Chapman).
280 r
400HM
281 Figure B2. 1. Astrononion echolsi Kennett, 1967. 2. Pullenia bulloides (d'Orbigny). 3. Bolivina pseudapunctata Hoeglund. 4. Fursenkoina fusiformis. 5. Fursenkoina earlandi (Parr). 6. Bulimina aculeata d'Orbigny. 7. Globocassidulina biora (Crespin). 8. Nonionella iridea Heron & Earland.
282 1 I
283 APPENDIX C
Appendix C: Foraminiferal counts (#/cc) of cores GC14 / GC15 (Palmer Deep basin I), KC26 (Palmer Deep Basin II), and KC17 / KC27 (Palmer Deep basin III). The list does not include poorly represented or obviously reworked shallow water forms.
284 APPENDIX C
Core# GC14 GC14 GC14 GC14 GC14 GC14 GC14 GCI4 GC14 GC14 GC14 GC14 GC14 GC14 GCI4 GC14 GC14 GC14 GCI4 GCI4 Core depth (mbs!) 0.27 0.32 0.37 0.42 0.47 0.52 0.57 0.62 0.67 0.72 0.77 0.82 0.87 0.92 0.97
Counts (#/cc) . A. echolsi 0.1 0.1 0.2 0.3 0.3 0.2 0.4 0.1 0.4 0.4 0.5
B. pseudapunctata 0.2 0.1 0.1 9.4 3.2 5.9 0.4 0.4 - 0.4 0.2 0.6 5.3 2.3 0.4 8.4 1.6
B. aculeata 13.3 3.9 10.4 19.4 25.0 27.4 12.0 8.1 2,8 25.0 7.0 0.1 2.8 21.0 17.4 48.1 15.8
C. lobatulus
Cribrostomoides sp. to 00 F. fusiformis 2.5 0.2 - 0.5 1.0 0.2 7.1 0.2 - - 0.4 - 1.0 0.4 0.3 0.2 0.1 0.1
H. canariensis
H, parkerae
Haplophragmoides sp.
M. arenacea 0.9 0.1 0.6 0.4 - 0.9 1.4 0.6 0.8 0.2 0.2 0.3 0.1 0.4 0.8 0.6 0.2 1,2 0.3
N. pachyderma - 0.1 5.8 0.1 0.3 - 0.6 0.1 0.2 0.4 0.5 6.7 0.2 0.5 0.2 - 0.4 0.6
P. eltaniae 0.8 - - - 0.4 0.3 0.4 - 0.1 - - - 0.4 0.1 0.4 - 0.7 0.2
P. bulloides - 2.8 - 1.1 1.2 0.3 0.3 1.1 0.6 1.0 1.8 0.1 - 0.3 0.7 0.1 0.5 0.4
Reophax spp.
T. angulosa - - -- 0.1 - - - 0.1 0.1 0.1 -- 0.1 --- -
T intermedia 0.3 - 0.1 -- 0.2 0.1 0.1 0.1 0.4 0.2 0.2 - 0.2 0.3 ■ - 0.1 0.2 APPENDIX C
C ore# GCI4 GC14 GC14 GCI4 GC14 GCI4 GC14 GC14 GC14 GC14 GC14 GCI4 GC14 GCI4 GCI4 GC14 GCI4 GC14 GCI4 GCI4
Core depth (mbsO 1.02 1.07 1.12 1.17 1.22 1.27 1.32 1.37 1.42 1.47 1.52 1.57 1.62 1.67 1.72 1.77 1.82 1.87 1.92 1.97
Counts (#/cc)
À, e c h o ls i ■ 0.8 0.6 • 0.1 - 0.1 - - 0.2 0.2 . . . 0.4 .....
B. pseudopunctata 0.2 22.8 9.6 7.2 3.8 2.4 1.8 1.3 6.0 6.5 6.8 6.5 1.0 5.9 4.4 - 0.2 5.6 1.2 3.3
B. aculeata 7.5 39.6 32.4 49.8 10.2 2.9 8.5 16.4 63.0 12.2 61.0 7.6 20.0 7.4 34.2 8.5 20.1 13.6 76.0 12.4
C. lo b a tu lu s ......
Cribrostomoides s p ...... N) 00 o\ F, fusiformis 0.1 0.8 0.2 0.4 1.1 0.7 0.6 1.3 0.6 - 1.2 0.3 0.2 1.6 - - - 0.3 - 0.1
H. canarietjsis
H. parkerae
Haplophragmoides sp.
M. arenacea 0.2 3.0 1.0 0.8 2.9 2,0 2.1 0.7 - 0.7 5.4 1.3 1.2 0.8 1.8 1.3 1.5 0.8 1.6 0.3
N. pachyderma - 1.4 1.2 0.8 0.1 0.1 -- 0.4 0.2 0.8 0.2 0.1 - 0.2 - 0.5 - - ■
P. eltaniae - 2.2 0.4 - 0.5 - 0.1 --- 2.0 - 0.3 -- 0.2 - 0.2 0.2 -
P. bulloides 0.6 1.2 0.4 0.2 0.2 0.6 0.5 0.2 ■ 1.5 0.6 0.4 - 0.1 - - - 1.3 - 0.1
Reophax spp.
T. angulosa --- 0.2 ------0.1 ------■
T. intermedia 0.1 0.4 0.2 - 0.3 0.2 0.4 0.3 - 0.1 - - - 0.3 0.2 0.2 -- 0.2 - APPENDIX C
C ore# GC14 GC14 GC14 GC14 GC14 GCI4 GC14 GC14 GC14 GC14 GC14 GCI4 GC14 GC14 GC15 GC15 GC15 GC15 GC15
Core depth (mbsO 2.02 2.12 2.17 2.22 2.27 2.32 2,37 2.42 2.47 2.52 2.57 2.62 2.67 2.72 0.05 0.10 0.15 0.20 0.25
Counts (#/cc)
A, echolsi 0.8 0.2
B. pseudopunctata 54.4 1 - 24.8 0.1 14.0 8.0 8.4
B. aculeata 12.2 6 0.2 12.2 7.5 12.2 12.0 17.4 0.2 0.8 7.2
C. lobatulus
Cribrostomoides sp. to F. fusiformis 1.2 1.6 0.2
H, canariensis
H. parkerae
Haplophragmoides sp.
M. arenacea 1.2 0 9 0.1 1.4 2.6 1.0 0.2 1.0 0.4 1.6 0.6 0.2 1.0 0.4 0.6 0 8
N, pachyderma 0.6 1.8 - - - -
P. eltaniae 0.2 0.4 0.1 0.4 0.2 0.2
P. bulloides 5.0 1.6 0.3 1.4
Reophax spp. 0.4 0.2
f. angulosa
T. intermedia 0 2 0.2 0.2 0.6 0.4 0.2 APPENDIX C
C ore# GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GC15 GCI5
Core depth (mbsO 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30
Counts (#/cc)
À. echolsi ......
B. pseudopunctata......
B. aculeata 0.2 4.0 - 0.4 - - 0.4 - 0.2 0.4 - - 2.0 - 10.0 0.4
C. lobatulus ......
Cribrostomoides sp. 0.2......
M F. fusiformis......
H. canariensis ......
H. parkerae ......
Haplophragmoides s p ......
M. arenacea - - 0.6 1.4 0.6 0.6 2.2 0.4 0.4 - 1.6 2.4 1.2 0.8 0.6 2.2 1.2 2.4 2.4
N. pachyderma ......
P. eltaniae 0.2 ------
P. bulloides ... .. 0.2 ......
Reophax spp. 0.2 - - - - - 0.2 - - - - 0.2 0.2
71 angulosa......
71 intermedia 0.2 0.2 - 0.8 0.6 1.4 0.2 - 0.6 0.4 - 0.4 0.2 0.2 0.2 0.2 0.4 - 0.2 0.4 APPENDIX C
C ore# GC15 GCI5 GC15 GC15 GCI5 GC15 GCI5 GC15 GC15 GC15 GC!5 GC15 GC15 GC15 GCI5 GC15 GC15 GC15 GC15 GC15
Core depth (mbsf) 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20 2.25 2.30
Counts (#/cc)
X. echolsi ......
B. pseudopunctata ...... B. aculeata - - 1.2 13.0 - - - 68.8 0.4
C. lobatulus
^ Cribrostomoides sp.
F. fusiformis
H. canariensis
H. parkerae
Haplophragmoides sp.
M. arenacea 0 4 0.2 2.8 1.4 0.4 0.4 0.2 0.6 - - 1.4 - 1.0 0.2 0.4 1.2 - 1.6 0.8 0.4
N. pachyderma
P. eltaniae
P. bulloides
Reophax spp. 0.2 0.2
T. angulosa
T. Intermedia 2.6 1.8 1.6 0.6 0.8 0.6 0.4 0.2 0.4 0.2 0.2 - 1.2 1.0 1.4 0.6 0.8 0.6 0.4 0.4 APPENDIX C
C ore# GC15 GC15 GC15 GC15 KC17 KC17 KC17 KC17 KC17 KCI7 KC17 KC17 KCI7 KC17 KC17 KC17 KC17 KC17 KCI7 2.35 2.40 2.45 2.50 0.01 0.03 0.05 0.07 0.09 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Counts (#/cc)
A. echolsi - 0.4 0.1
B. pseudopunctata -- - 0.4 0.7 0.4 1.5 0.4 - - - - - 0.2 ----
B. aculeata ■ ■ 7.8 7.3 4.0 3.2 1.9 -- --- 12.0 0.8 -- -
C. lobatulus
Cribrostomoides sp. 0.2 0.2 - 0.4 - 0.2 g F. fusiformis -- - 0.1 - - - 0.1 ------
H. canariensis -- ■ 0.3 - 0.1 0.1 -
H. parkerae -- - 9.2 1.4 1.1 0.3 0.2 ------0.8 -
Haplophragmoides sp.
M. arenacea 0.2 0.4 - 0.2 0.3 0.3 0.3 0.2 1.6 1.4 0.2 1.0 0.4 3.4 1.2 2.2 1.6
N. pachyderma -- - 0.2 ------
P. eltaniae - - - 4.4 1.7 0.9 0.2 0.1 0.8 2.4 1.0 0.4 0.2 0.2 ■ 2.8 1.0 0.2
P. bulloides -- 2.4 0.4 0.1 0.1 0.1
Reophax spp. ------0.1 0.2 0.2 -- 0.2 0.2 - 0.4 0.2 0.2
T. angulosa
T intermedia 0.6 0.2 1.2 0.2 0.3 0.4 0.6 0.2 0.2 0.2 0.4 0.2 0.2 APPENDIX C
Core# KC17 KCI7 KC17 KC17 KC17 KC17 KC17 KCI7 KC17 KCI7 KCI7 KC17 KC17 KC17 KCI7 KC17 KC17 KC17 KC17 KC17 Core depth (mbsf) 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1,45 1.50 1.55 1.60
Counts (#/cc)
A. echolsi ......
B. pseudopunctata ......
B, aculeata o.4- - 0.4 ------
C. lobatulus ...... Cribrostomoides sp. - - - 0.2 ------0.2 0.2 ------
F. fusiformis ......
H. canariensis ...... H. parkerae 0.2 ------0.2-----
Haplophragmoides s p ...... 0 2 M, arenacea 0.6 0.6 1.6 1.0 1.0 1.4 0.6 0.6 1.8 2.6 2.6 1.2 1.4 1.2 4.4 1.0 4.0 2.2 0.8 1.6
N. pachyderma ......
P. eltaniae 0.4 - 0.2 0.2 0.6 0.2 - 0.2 0.2 -
P. bulloides ...... Reophax spp. ■ - - - 0.2 0.2 - 0.2 - 0.2 - 0.2 ......
T. angulosa ...... 71 intermedia - - 0.2 . . . 0.2 . . . 0.2 - 0.4 0.2 - - 0.2 0.2 0.2 APPENDIX C
Core# KCI7 KC17 KC17 KC17 KC17 KCI7 KC17 KCI7 KC17 KC17 KC17 KC17 KC17 KC17 KCI7 KC17 KCI7 KC17 KC17 KC17
Core depth (mbsO 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20 2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60
Counts (#/cc)
A. echolsi ......
B. pseudopunctata ......
B. aculeata ......
C. lobatulus ......
Cribrostomoides s p ...... 0-2
F. fusiformis......
H. canariensis ......
H. parkerae ......
Haplophragmoides s p ...... M. arenacea 2.4 1.2 - 2.0 1.2 0.2 0.2 4.2 1.0 0.6 3.2 0.6 2.6 3.2 0.8 2.6 0.6 1.2 1.6 10
N. pachyderma ...... P. eltaniae 0.4 0.6 ------
P. bulloides......
Reophax spp. 0.2 -
T, angulosa ...... T. intermedia 0.4 - 0.6 0.4 0.2 - 0.2 0.6 - - 0.2 0.2 0.2 - 0.2 APPENDIX C
Core# KCI7 KC17 KC17 KC17 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 Core depth (mbsf) 2.65 2.70 2.75 2.80 0.01 0.05
Counts (#/cc)
À. echolsi - --- 0.1 -
B, pseudopunctata ---- 21.1 5.6 7.6 0.2 - - 2.2 0.2 1.6
B. aculeata ■ --- 6.2 56.0 74.0 8.6 0.2 0.6 7.0 - 8.6 0.4
C. lobatult4s ------0.2 - - -
Cribrostomoides sp. - - -- 0.6 2.22.2 1.0 3.4 0.6 2.4 0.2 1.0 - - 0.2 1.4 1.4 u> F. fusiformis
H. canariensis - - - - 0.4 0.4
H. parkerae
Haplophragmoides sp.
M. arenacea 0.8 2.4 5.4 2.4 0.1 0.8 8.6 0.4 0.2 1.0 0.2 3.4
N. pachyderma - - - - 0.1 0.6 2.4
P. eltaniae - - 0.2 - 0.6 3.8 0.2 0.2 0.4 0.6 0.2
P. bulloides - -- - 0.8 2.4 11.6 . 0.2 1.4 - 0.2 0.2
Reophax spp. - -- - 0.6 0.6 0.6 - 0.2 - 0.4 0.2 0.2
71 angulosa ------0.2
71 intermedia 0.2 -- 0.4 - 0.8 APPENDIX C
Core # KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26
Core depth (mbsO 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75
Counts (#/cc) ......
A. echolsi ......
B. pseudopunctata ...... o , 2 ------0.2----
B, aculeata 6.8 - - - 1.4 3.2 5.4 3.0 - - - - 1.6 3.6 2.2 3.8 - - - -
C. lobatulus
Cribrostomoides sp. 0.2 - 0.8 ------0.6 - 0.4 0.2 g F, fusiformis
H. canariensis
H. parkerae
Haplophragmoides sp.
M. arenacea 0.4 - - 0.2 0.2 - - - - 0.6 0.6 - 0.4 - 0.4 0.6 - - 1.0
N. pachyderma
P. eltaniae * • - 0.4 - 0.2 0.4 0.2 0.2
P. b u llo id e s 1.0 - - - - 0.6 2.0 0.4 0.2 - - - 0.2 0.8 - 1.8
R eo p h a x spp. ■ - • • • • - 0.2 - - - - 0.2 - - - - 0.2
T. angulosa
T. intermedia APPENDIX C
Core# KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 KC26 Core depth (mbsf) 1.80 1.85 1.90 1.95 2.00 2,05 2.10 2.15 2.20 2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60 2.65
Counts (#/cc)
À. echolsi
B. pseudopunctata 0.4
8. aculeata 6.2 - 0.2 0.2 13.4 0.4
C. lobatulus
Cribrostomoides sp. 0.4 0.2 0.2 0.2 0.2 0.2
F. fusiformis
H. canariensis
H. parkerae
Haplophragmoides sp.
M. arenacea 0.6 0.6
N. pachyderma
P. eltaniae
P. bulloides - 16
Reophax spp. 0 2 - 0.2 0.2 0.2 0.2
71 angulosa
71 intermedia APPENDIX C
Core # KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 Core depth (mbsf) 0.03 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95
Counts (#/cc)
A. echolsi - 0.1 - B. pseudopunctata 3.3 2.3 18.6 7.0 9.0 5.2 0.2 5.4 0.2 0.2 --- - 0.2 - 0.2 --- B. aculeata 21.1 26.7 20.8 29.0 23.0 13.4 - 8.6 3.6 2.0 2.4 1.4 - - 9.8 1.4 4.6 4.6 - C. lobatulus Cribrostomoides sp. -- 5.2 0.6 1.4 2.0 0.6 0.2 - - 1.0 - - 0.4 0.2 0.2 - 0.2 0.2 S F. fusiformis - 0.2 H. canariensis - 0.2 0.6 0.6 0.4 0.4 --- - 0.4 ------0.2 H. parkerae - 0.8 8.2 4.2 3.6 4.4 - 0.4 - - 0.2 - --- 0.2 --- Haplophragmoides sp. - 0.8 0.6 0.4 0.4 0.2 --- 0.4 ------M. arenacea 0.3 0.3 0.4 1.0 0,4 0.2 -- 0.4 0.4 0.6 - - 0.6 0.8 0.2 0.2 - ■ N. pachyderma 0.2 --- - - 0.4 ------P. eltaniae - 0.2 4.0 8.4 4.8 1.6 - 1.0 0.2 0.6 2.4 - 1.8 1.0 0.2 0.2 - 0.4 0.2 1.2 P. bulloides 0.5 1.2 1.8 2.2 0.4 2.0 - 0.4 0.4 - -- -- 0.6 0.2 0.6 1.0 - Reophax spp. 0.8 1.9 1.4 1.2 1.0 0.2 0.2 0.4 0.2 0.4 0.2 - 0.2 0.6 - 0.2 0.4 0.2 -- T. angulosa ------0.2 ------■ T intermedia 0.2 0,1 __ 0.2 0.2 0.6 0.2 - 0.8 . 1.0 . 0.2 - 0.2 --- APPENDIX C
Core # KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 Core depth (mbs!) 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 0.01
Counts (#/cc)
À. echolsi
B. pseudopunctata 2.9 B. aculeata 2.4 11.6 1.0 0.8 2.4 17.4
C. lobatulus
Cribrostomoides sp. 0.8 1.6 1.2 0.2 0.2 g F. fusiformis 0.1 H. canariensis 0.2 H. parkerae 0.3
Haplophragmoides sp. 0.2
M. arenacea 0.2 0.2 0.8 0.2 0.4 0.2 0.2 0.4
N. pachyderma
P. eltaniae 1.0 - 1.0 0.8 6.4 0.2 1.2 0.8 0.2 0.8 0.4 0.2 0.6 1.2 0.4 0.8 0.4 0.6 0.4 P. bulloides 0.6 2.4 1.9 Reophax spp. 0.2 0.2 0.2 0.2 0.2 0.6
T. angulosa T intermedia 0.2 0.2 0.4 0.4 0.2 0.2 0.2 0.4 0.2 0.1 APPENDIX C
Core # KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27 KC27
Core depth (mbsf) 1.00 1.05 2.10 2.15 2.20 2.25 2.30 2.35 2.40 2.45 2.50 2.55
Counts (#/cc)
À. echolsi ......
B. pseudopmctata ......
B. aculeata 0.6 9 . 8 ......
C. lobaiulus ......
Cribrostomoides sp. - 0.2 - - 0.2 - 0.8 0.2 0.4 - 0.2 00 F. fusiformis ......
H. canariensis ......
H. parkerae ......
Haplophragmoides sp. 0 . 2 ......
M .arenacea 0.2 0.4 1.4 1.0 - 0.8 - 0.2 0.4 0.2 N. pachydema ......
P. eltaniae 2.2 0.8 - 0.4 0.8 - 0.4 - - - - 1.0
P. bulloides - 0 . 8 ......
Reophax spp. 0 . 2 ...... 20.4
T. angulosa ......
T. intermedia 0.4 0 . 4 ...... 0.2 - 0.2 A P P E N D IX D
^pendix D: Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BEAR) (#/cm^ky‘^), Varimax Princçal Component Loadings of Holocene benthic foraminiferal Q-mode assemblages, and occurences of gypsum in core ODP 1098b from the Palmer Deep basin I. List iucludes only species used in the potential fossil data set.
299 APPENDIX D
Core depth (mcd) 0.11 0.16 0.31 0,36 0.46 0.51 0.56 0.61 0.66 0.71 0.76 0,81 0.86 0.91 0.96 1.01 1.06 1.11 1.16 1.21 1.26 1,31
Age(kyBP) 0.04 0.07 0.15 0,18 0,24 0.26 0.29 0.32 0.34 0.37 0,40 0,42 0.45 0.48 0.50 0.53 0.55 0.58 0.61 0.63 0.66 0.68
Counts (#/cc) A. echolsi ..... 0.1 0.3 0.2 0.7 0.1 0,1 . 0.1 0.1 0.1 0.1 0.2 B. pseudopmctata 1,0 0,2 - - 0.1 0.9 4.5 14.6 11.7 2.5 1,4 0.8 1.6 1.5 5,6 5.6 1.4 4,3 6.8 0.7 8.3 1.9 B. aculeata 1,4 0,3 - - 1,1 0.9 4.4 8.2 14.2 5.5 11,6 2.8 2.2 5.5 13,9 11.5 7.8 4,2 6.1 3.9 2.4 3.8 C, lobatulus . . . . . F, earlandi ...... 0.2 .. - . 0.2 . 0.1 . . . . . ■ . . F, fusiformis - - - - 0,1 0.6 0.2 0.3 0.1 --- 0.4 0.3 0,1 0.2 0.1 0,1 - - 0.1 - G, biora ..... G, crassa rossensis . . . . . M, arenacea 0,2 0.2 1.1 0.9 0.5 0.2 0.3 0.2 0.2 0.5 - 0.4 0.5 0.5 4,8 0.5 - 0,7 0.8 0.9 0.6 0.8 N. iridea ...... P. bulloides - 0.1 - - 0.1 0.2 0.1 0.1 0.2 0.2 0.1 ._ 0.2 . 0.3 . 0.1 0.1 T. angulosa ..... -- 0.2 --- 0.1 ------T. intermedia - 0.1 - 0.2 0.2 0.1 0.1 0.1 - 0.1 - 0.1 - 0.1 0.1 0.2 - 0.1 - 0.2 N. pachydenna ...... - 0.2 0.1 - - 0,4 0.2 ------0.7 -- -
Diversity (#species) 3 5 1 1 5 6 8 8 7 5 3 7 5 7 4 6 6 5 5 4 6 6
BFAR(#/cmV‘) ^12 269 231 442 731 2596 6000 6769 2173 3365 1212 1231 2019 6115 4519 2423 2385 3673 1404 2885 1769
Q-mode loadings -0.01 -0.13 -0.15 -0.16 -0.08 -0,13 -0.03 0.03 -0.05 0,18 -0.12 -0.14 -0.05 -0.08 0.10 -0.07 0.04 0.75 0.85 0.67 0.90 0.99 0,97 1.00 0.93 0.99 0,98 0.98 0.98 0.86 0.83 0.98 0.48 0.98 0.13 -0.04 -0.03 -0.03 -0.03 -0,02 -0.04 0.06 0.00 -0.01 -0.02 -0.02 -0.06 -0.03 -0.03 -0.02 -0.05
Gypsum APPENDIX D
Core depth (mcd) 1.41 1.46 1.51 1.56 1.61 1.66 1.71 1.86 1.91 1.96 2.01 2.26 2.31 2.41 2.46 2.51 2.66 2.71 2.76 2.91 2.96 3.01
Age(kyBP) 0.73 0.76 0.79 0.81 0.84 0.86 0.89 0.96 0.99 1.01 1.03 1.16 1.18 1.23 1.25 1.28 1.35 1.37 1.39 1.46 1.49 1.51
Counts (#/cc) A. ccholsi ------0.2 ------0 , 1 - B. pseudopmctata 1.5 4.8 1.8 0,4 0.3 0.3 0.1 2.6 0.2 0.4 1.2 - - 0.7 0.5 - 0.2 1,6 - - - - B. aculeata 2.2 3.6 3.2 0.9 3.2 2.2 0.3 2.5 0.3 1.3 5.9 - - 1.4 1.5 - 0.8 4.9 0.3 - C. lobatulus ------Fi eaclafidi ------F. fusiformis 0.2 0.1 - - - 0.1......
(f. crassa rosserists ------w Af. arenacea 0.3 0.1 1.7 0.4 1.3 0.9 0.2 3.3 0.8 2.5 0.3 0.9 0.4 0.4 0.3 0.5 0.1 0.4 0.3 0.1 0.5 3.8 O I trtdea ------P. bulloides - - 0.5 0.1 0.1 ------0.2 - Ï) angulosa ------
T. intermedia 0.1 0.2 O.l...... O.l - O.l - O.l 0.1 0.4 0.2 0.1 N. pachydenna - 0.1 - 0.1......
Diversity (#species) 555444343331 1432363222 BFAR (#/cm \y‘) 1096 2212 isos 462 1212 SS5 135 2173 30S 103S 1S65 231 96 635 596 135 269 ISOS 173 115 154 962
Q-mode loadings QPCl Af. arenacea -0.05 -0.15 0.29 0.23 0.27 0.27 0.33 0.60 0.89 0.85 -0.09 1.00 1.00 0.10 0.04 0.99 -0.04 -0.08 0.65 0.17 0.96 1.00 QPC2 B, aculeata 0.94 0.77 0.92 0.97 0.94 0.95 0.94 0.69 0.44 0.53 0.99 0.04 0.04 0.98 1.00 0,02 0.99 0.99 0.70 -0.15 -0.01 0.04 QPC3 F. fusiformis 0.00 -0.05 -0.03 -0.01 -0.01 0.01 -0.01 0.00 0.02 0,01 -0.02 0.03 0.03 -0.06 -0.02 -0.12 -0.02 -0.03 -0.15 -0.87 -0.26 0.01
Gypsum APPENDIX D
Core depth (mcd) 3.11 3.16 3.21 3.26 3.31 3.41 3.51 3.56 3.61 3.66 3.71 3.76 3.81 3.96 4.01 4.06 4.11 4.16 4.21 4.26 4.31 4.36 4.41
A ge(kyB P) 1.56 1.58 1.60 1.63 1.65 1.69 1.74 1.76 1.78 1.81 1.83 1.85 1.87 1.94 1.96 1.98 2.00 2.02 2.05 2.07 2.09 2.11 2.13
Counts (#/cc) A. echolsi ...... 0.1 0.1 B. pseudopunclata 0.2 0.9 0.4 -- 0.5 - 0.2 1.2 - 1.0 3.0 1.3 B. aculeata 0.1 0.4 4.4 2.1 0.4 - 0.4 2.2 0.4 3,1 2.2 0.2 0.4 3.5 4.9 C. lobatulus F, earlaitdi F. fusiformis 0.1 ------0.1 -- G. biora G, crassa rossensis M, arenacea 0.5 0.4 0.4 0.7 1.0 0.2 0.2 0.5 0.2 1.0 0.3 0.5 0.9 3.6 0.8 0.8 0.7 0.8 0.5 0.2 1.6 0.1 0.4 S N. iridea P. bulloides 0.2 0.1 ---- 0.1 -- 0.2 0.3 0.1 T, angulosa T. intermedia 0.2 0.2 0.1 0.1 0.2 0.1 .... 0.1 0.2 . 0.1 0.1 N. pachydenna ------0.1 -
Diversity (#species) 2 2 2 1 1 3 4 4 2 1 3 1 2 2 3 2 4 4 3 5 6 6
B F A R (#/cm V ‘) 1^5 115 173 250 192 1442 769 135 250 115 115 923 308 885 269 1058 962 135 808 1769 1712
Q-mode loadings 1.00 0.89 0.24 0.85 0.15 0.04 0.72 0.80 -0.16 -0.07 0.04 0.44 0.97 0.51 0.96 0.98 0.45 0.35 0.89 0.99 0.01 0.02 -0.01 0.02 -0.01 -0.05 -0.45 0.03 -0.04 -0.03
Gypsum APPENDIX D
Core depth (mcd) 4.46 4.51 4.56 4.81 4.86 4.91 4.96 5.01 5.11 5.16 5.21 5.26 5.41 5.56 5.61 5.66 5.71 5.76 5.81 5.86 6.17 6.22 6.27
Age(kyBP) 2.15 2.17 2.19 2.30 2.32 2.34 2.36 2.38 2.42 2.44 2.46 2.48 2.54 2.60 2.62 2.64 2.66 2.68 2.70 2.72 2.84 2.86 2.88
Counts (#/cc) A. echolsi 0.2 0.5 B. pseudopunctata 4.2 1.1 0.1 0.1 0.3 0.1 0.2 0.5 1.2 0.6 1.5 0.2 0.1 0.1 B. aculeata 0.2 10.8 4.1 1.2 3.8 1.8 0.1 0.4 0.4 0.5 1.1 5.2 9.0 0.2 1.5 1.8 1.8 0.7 C. lobatulus F. earlandi F. fusiformis G. biora 0. crassa rossensis ^ M. arenacea 0.5 0.5 0.2 0.2 0.5 0.2 0 0.3 0.3 0.2 0.5 0.2 0.2 4.2 0.2 0.2 0.2 0.2 0.1 0.5 0.4 S N, iridea P. bulloides 0.6 0.8 0.1 0.1 0.2 0.1 T. angulosa T. intermedia 0.1 0.1 0 0.1 0.2 0.2 0.2 0.1 0.2 0.1 0.1 0.2 0.5 0.2 0.2 N. pachydenna 0.2 0.1
Diversity (#species) 24444342 3 3 5 4 2 3 6 3 3 3 4 4 2 2 2 BFAR(#/cmV') 4038 1538 365 1154 558 115 96 231 192 365 731 96 1481 3885 115 442 538 538 269 154 173 135
Q-mode loadings QPCl M. arenacea 0.95 -0.11 -0.10 0.01 0.02 -0.14 0.87 0.98 0.48 0.55 0.04 0.13 0.85 ■0.10 0.31 0.54 -0.13 0.00 -0.04 0.09 0.12 0.91 0.94 QPC2 B. aculeata 0.31 0.99 0.98 0.96 0.96 0.98 0.36 0.00 0.85 0.77 0.86 0.82 -0.05 0.97 0.94 0.52 0.96 0.96 0.96 0.91 -0.15 -0.03 -0.02 QPC3 F. fusiformis 0.02 -0.02 -0.02 -0.07 -0.01 -0.02 -0.26 -0.19 -0.01 -0.14 -0.22 -0.11 -0.48 -0.02 -0.01 -0.54 -0.06 -0,01 -0.05 -0.20 -0.87 -0.38 -0.31
Gypsum . . .. -...... -- ...... APPENDIX D
Core depth (mcd) 6,37 6.47 6.57 6.67 6.91 6.96 7.01 7.06 7.11 7.16 7.21 7.31 7.36 7.41 7.51 7.56 7.66 7.71 7.76 7.81 7.86 7.91 7.96
A ge(kyB P) 2.92 2.96 3.00 3.03 3.12 3.14 3.16 3.18 3.20 3.21 3.23 3.27 3.29 3.31 3.34 3.36 3.40 3.41 3.43 3.45 3.47 3.48 3.50
Counts (#/cc) A. echolsi ------B, pseudopunctata --- 0.2 0.5 0.1 1.8 0.2 0.1 1.1 - 0.2 0.1 -- - B. aculeata - - 2.3 1.5 0.5 1.0 0.3 4.2 1.7 0.1 3.9 0.2 0.5 1.0 - - - C. lobatulus - - 0.1 ------F. earlandi ------F. fusiformis ---- 0.2 ------G. biora ------G. crassa rossensis ------M. arenacea 0.1 0.1 0.1 0.2 0.5 0.2 0.2 0.2 0.1 0.1 0.4 0.4 0.3 1.2 0.9 0.8 0.4 0.3 0.1 0.4 0.4 0.5 1.2 N. iridea ------■ - P. bulloides -- 0.1 0.1 - 0.2 -- 0.1 0.1 --- T angulosa ------T. intermedia 0.5 0.7 0.4 0.2 0.2 0.1 0.1 0.2 -- 0.3 0.1 - 0.4 0.1 0.1 -- 0.1
N. pachyderma -- 0.2 -- . ------
Diversity (#species) 222246343531 2 3 4 2 2 5 5 1 1 1 2 B F A R (# /cm V ') '^4 115 115 769 635 192 365 115 1577 577 96 96 404 1500 269 192 288 327 96 96 115 308
Q-mode loadings QPCl M. arenacea 0.12 0.09 0.17 0.72 0.08 0.00 0.16 0.10 0.11 -0.14 0.10 1.00 0.96 0.98 0.09 0.95 0.72 0.41 -0.06 1.00 1.00 1.00 1.00 QPC2 B. aculeata -0.15 -0.16 -0.15 -0.09 0.96 1.00 0.92 0.92 0.99 0.98 0.98 0.04 0.28 0.02 0.99 0.30 -0.09 0.88 0.96 0.04 0.04 0.04 0.03 QPC3 F. fusiformis -0.87 -0.87 -0.87 -0.62 -0.07 -0.06 -0.13 -0.14 -0.01 -0.01 -0.01 0.03 0.02 -0.19 -0.03 0.02 -0.62 -0.13 -0.08 0.03 0.03 0.03 -0.03
Gypsum . ... _ ... APPENDIX D
Core depth (mcd) 8.01 8,06 8.11 8.21 8.26 8.46 8.51 8.61 8.66 8.71 8.76 8.81 8.86 9.01 9.11 9.16 9.21 9.26 9.31 9.36 9.41 9.51
Age(kyBP) 3.52 3.54 3.55 3.59 3.61 3.68 3.69 3.73 3.74 3.76 3.78 3.80 3.81 3.86 3.90 3.91 3,93 3.95 3.96 3,98 4.00 4.03
Counts (#/cc) A. echohi B. pseudopunctata ...... o.3 B. aculeata O.l 0 . 2 ...... 24.8 C. lobatulus F. earlandi F. fusiformis G, biora G, crassa rossensis w M. arenacea 0.8 0.4 0.2 0.3 0.6 1.5 0.2 1.1 1.5 0.4 0.8 0.5 0.8 1.3 1.1 0.6 0.9 0.4 0.3 1.1 0.8 0.3 s N. iridea P. bulloides T. angulosa T. intermedia 0.2 0.1 0.2 0.2 . - 0.3 - - 3.2 0.2 0.1 . - 0.2 . 0.1 0.1 0.2 - . 0.1 N. pachyderma 0.2
Diversity (#species) 3 3 2 2 1 1 2 3 1 2 221121222112
BFAR (#/cm \y') ^ '34 115 115 154 385 115 6577 365 904 250 154 192 327 308 154 250 115 115 269 192 96
Q-mode loadings QPCl M. arenacea 0.99 0.91 0.72 0.91 1.00 1.00 0.44 -0.07 1.00 0.09 0.97 0.99 1.00 1.00 0.99 1.00 1.00 0.99 0.91 1.00 1.00 0.98 QPC2 B. aculeata 0.10 0.37 -0.09 -0.03 0.04 0.04 -0.13 0.95 0.04 -0.15 0.00 0.02 0.04 0.04 0.02 0.04 0.03 0.01 -0.03 0.04 0.04 0.00 QPCi F. fusiformis -0.13 -0.15 -0.62 -0.38 0.03 0.03 -0.80 -0.01 0.03 -0.87 -0.23 -0.10 0.03 0.03 -0.10 0.03 -0.05 -0.15 -0.38 0.03 0.03 -0.19
Gypsum APPENDIX D
Core depth (mcd) 9.56 9.66 9.71 10.06 10.16 10.21 10.26 10.31 10.36 10.51 10.56 10.61 10.86 10.91 10.96 11,01 11.06 11,11 11.16 11.21 11,26 11.31
A ge(kyB P) 4,05 4.08 4.09 4.21 4.24 4.26 4.27 4.29 4.30 4.35 4.37 4.38 4.46 4.48 4.49 4.51 4.52 4.54 4.56 4.57 4.59 4.60
Counts (#/cc) i4. ccholsi Sf psciidopHfictoto ------0.1 " 0.2 ------B, aciilcQto ------0.2 ------C. lob at ulus -
Ft corloftdi ------Ft ^iSlJbfJHlS ------Gt bio fCl ------Gt crossci rosscfisis ------Af. arenacea 0.4 2.5 0.9 0.8 8.0 1.4 0.5 5.5 0.8 0.5 0.5 0.5 0.7 0.5 0.5 0.9 0.9 1.0 0.5 0.4 0.2 0.8 N, iridea ------P. bulloides ------•---- T. angulosa ------T intermedia 0.2 0.2 0.2 0.1 0.1 -- 0.3 - 0.1 - 0.1 0.2 0.2 0.3 0.1 - 0.2 - 0.1 0.2 - N, pachyderma ------
Diversity (#species) 2 2 2 2 2 1 1 2 1 2 2 2 3 2 3 2 1 2 1 2 2 1 250 288 115 212 BFAR(#/cmV‘) 135 692 269 212 2019 346 135 1462 192 135 154 154 288 173 250 231 135 115
Q-mode loadings QPCl Af. arenacea 0.94 1.00 0.99 1.00 1.00 1.00 1.00 1.00 1.00 0.99 0.98 0.99 0.91 0.97 0.77 1.00 1.00 0.99 1.00 0.99 0.72 1.00 QFC2 B. aculeata -0.02 0.03 0.02 0.03 0.04 0.04 0.04 0.03 0.04 0.02 0.07 0.02 0.06 0.00 0.34 0.03 0.04 0.02 0.04 0.01 -0.09 0.04 QPC3 F. fusiformis -0.31 -0.05 -0.12 -0.06 0.02 0.03 0.03 -0.02 0.03 -0.12 0.02 -0.10 -0.26 -0.22 -0.47 -0.05 0.03 -0.11 0.03 -0.15 -0.62 0.03
Gypsum -...... ■.. APPENDIX D
Core depth (mcd) 11.41 11.46 11.51 11.56 11.61 11.71 11.81 11.86 11.96 12.01 12.06 12.11 12.16 12.56 13.01 13.11 13.26 13.41 13.56 13.61 13.96 14.01 14.06
Age (ky BP) 4.63 4.65 4.66 4.68 4.69 4.73 4.76 4.77 4.80 4.82 4.83 4.85 4.86 4.98 5.12 5.15 5.19 5.24 5.28 5.29 5.40 5.41 5.43
Counts (#/cc) A. echolsi ------B. pseudopunctata ----- 0.5 ------0.1 - - - - ■ - B. aculeata ----- 0.1 ------2.7 - - -0.6------C. lobatulus ------F. earlandi ------F. fusiformis ------G, biora ------G. crassa rossensis ------u> M. arenacea 0.5 0.2 0.2 0.2 0.3 0.2 6.7 1.8 5.7 0.6 2.5 1.8 0.1 2.8 1.9 1.7 0.4 3.9 0.3 0.2 0.4 1.3 5.0 o N. iridea ------P, bulloides ------T angulosa ------T intermedia 0.2 0.2 2.7 0.5 0.1 0.2 0.1 0.2 0.1 -- 0.1 --- 1.9 0.1 0.1 0.2 0.2 0.2 0.2 - N. pachyderma ------
Diversity (#species) 2 2 2 2 2 4 2 2 2 1 1 2 2 1 1 2 4 2 2 2 2 2 1
BFAR(#/cmV‘) 173 96 731 173 96 231 1692 500 1442 154 615 481 692 692 481 904 288 1000 135 115 135 365 1250
Q-mode loadings QPCl Af. arenacea 0.97 0.85 0.06 0.44 0.98 0.34 1.00 1.00 1.00 1.00 1.00 1.00 -0.09 1.00 1.00 0.67 0.44 1.00 0.82 0.72 0.94 1.00 1.00 QPC2 B. aculeata 0.00 -0.05 -0.16 -0.13 0.00 0.32 0.04 0.03 0.04 0.04 0.04 0.04 0.94 0.04 0.04 -0.10 0.87 0.04 -0.06 -0.09 -0.02 0.02 0.04 QPC3 F. fusiformis -0.22 -0.48 -0.87 -0.80 -0.19 -0.28 0.02 -0.05 0.02 0.03 0.03 -0.01 -0.01 0.03 0.03 -0.67 -0.10 0.01 -0.52 -0.62 -0.31 -0.08 0.03
Gypsum ..- APPENDIX D
Core depth (mcd) 14.16 14.21 14.31 14.41 14.46 14.56 14.61 14.66 14.76 14.96 15.16 15.26 15.31 15.36 15.41 15.56 15.61 15.66 15.71 15.76 15.96 16.11 16.26
Age(kyBP) 5.46 5.47 5.50 5.53 5.54 5.57 5.59 5.60 5.63 5.69 5.75 5.78 5.79 5.81 5.82 5.87 5.88 5.89 5.91 5.92 5.98 6.03 6.07
Counts (#/cc) A. echolsi B. pseudopmctata B. aculeata 0.3 0.9 C. lobatulus F. earlandi F, fusiformis G, biora G. crassa rossensis w M. arenacea 1.2 1.6 11 0.2 0.5 0.9 2.4 0.2 0.2 0.1 0.7 1.2 1.8 4.4 6.5 0.5 0.7 2.1 1.8 0.5 1.3 1 3 0.3 M N. iridea P. bulloides T angulosa T intermedia 0.2 0.1 0.2 0.2 0.2 0.1 0.1 0.2 0.1 0.1 0.1 N. pachyderma
Diversity (#species) 1 1 1 2 2 2 1 2 2 2 1 1 1 2 2 1 2 2 2 1 2 1 2 404 269 96 135 269 596 96 96 96 173 308 442 1115 1865 135 192 558 481 135 346 327 96
Q-mode loadings 1.00 1.00 0.85 0.99 0.99 1.00 0.85 0.85 0.13 1.00 1.00 1.00 1.00 0.98 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.98 0.04 0.04 -0.05 0.02 0.02 0.04 -0.05 -0.05 0.94 0.04 0.04 0.04 0.04 0.18 0.04 0.03 0.03 0.04 0.04 0.03 0.04 0.00 0.03 0.03 -0.48 -0.12 -0.12 0.03 -0.48 -0.48 -0.01 0.03 0.03 0.03 0.01 0.03 0.03 -0.07 -0.04 -0.01 0.03 -0.02 0.03 -0.19
Gypsum APPENDIX D
Core depth (mcd) 17,07 17.12 17.17 17.22 17.27 17.32 17.37 17.42 17.47 17.57 17.62 17.67 17.72 17.77 18.07 18.27 18.42 18.47 18.52 18.57 18.67 18.82 18.87
A ge(kyB P) 6.31 6.32 6.34 6.35 6.37 6.38 6.40 6.41 6.43 6.46 6.47 6.49 6.50 6.52 6.61 6.67 6,71 6,73 6,74 6,76 6,79 6,84 6,85
Counts (#/cc) /I. ccholsi ------
B, pscudoputictoSci ------B, oculcdto ------C, tobciSulus ------B, ccirlcifidt ------
Ft Jus1 ^ 0 mi I s ------
Gt crossd rosscfisis -
Af. arcridccd O . l 0.3 0.8 1.6 1.2 0.9 0.5 0.5 0.8 1.0 0.9 3.5 0.5 0.4 0.7 0.3 0.4 1.9 1.7 0.4 - 0.8 0.6
it^idcd ------Ft bulloides ------Ft dfi^ulosd - T. intemedid 0.3 0,1 0,2 0,5 0,4 - 0,3 ■ 0,5 0,1 0,1 0,1 0,1 - 0,1 0,1 - 0,1 - 0,1 9,1 0,4 0,2 A/. pdchydcrtHd ------
Diversity (#species) 22222121222221221212122 BFAR (# /c m \y ') 96 96 269 538 404 231 192 115 308 269 250 885 154 96 192 96 96 500 423 115 2269 308 192
Q-mode loadings QPCl Af. drcfldccd 0.22 0.98 0.98 0.96 0.97 1.00 0.85 1.00 0.87 1.00 1.00 1.00 0.99 1.00 1.00 0.98 1.00 1.00 1.00 0.99 -0.03 0.93 0.98 QPC2 B. dculcdtd -0.15 0.00 0.00 -0.01 -0.01 0.04 -0.05 0.04 -0.05 0.03 0.03 0.04 0.02 0.04 0.03 0.00 0.04 0.04 0.04 0.01 -0.16 -0.03 0.00 QPC3 Ft fusiformis -0.86 -0.19 -0.21 -0.26 -0.24 0.03 -0.48 0.03 -0.44 -0.04 -0.05 0.01 -0.10 0.03 -0.07 -0.19 0.03 -0.01 0.03 -0.15 -0.87 -0.35 -0.19
Gyp8Um APPENDIX D
Core depth (mcd) 18.97 19.07 19.12 19.27 19.37 19.42 19.52 19.62 19.87 19.92 19.97 20.47 20.52 20.72 20.77 21.02 21.07 21.12 21.22 21.27 21.32 21,37 21.42
Age(kyBP) 6.88 6.91 6.93 6.97 7.01 7.02 7.05 7.08 7.16 7.18 7.19 7.36 7.37 7.44 7.45 7.54 7.55 7.57 7.60 7.62 7.63 7.65 7.67
Counts (#/cc) ccholsi •mmmwmmmmmmmmmmmmmimmmm Bt psciidoputictotci Bt oculcoio 0.5 lobotuliis - Ft coT’lot'idi F, ^usiJ'oTiiiis - hiOTO G, crosso rossctisis M. arenacea 3.7 0.5 1.4 0.2 0.5 0.2 2.2 0.4 1.0 1.3 0.5 0.7 0.4 0.7 0.9 0.4 0.3 1.0 0.3 0.8 0.3 0.3 0.4 hit iridea Ft bulloides ------0.1 Tf angulosa ------Tt intermedia 0.2 0.4 0.3 0.2 0.4 0.3 0.2 0.2 o.l - - 0.2 0.1 0.1 0.1 0.2 0.1 - 0.2 0.4 0.2 0.1 hit pachydenna -
Diversity (#species) 2 2 2 2 2 2 2 2 2 1 1 2 2 2 2 2 2 1 2 2 2 2 3
BFAR (#/cmV‘) 423 96 212 115 577 154 269 327 135 231 115 192 250 135 96 250 115 288 135 96 231
Q-mode loadings 0,87 1,00 1,00 1,00 0,96 0,99 1,00 1,00 0,94 0.98 1,00 0,91 0,91 0,82 0.98 0,57 -0.05 0,03 0,04 0,04 -0,01 0,01 0,03 0,03 -0,02 0,00 0,04 -0,03 -0,03 -0,06 0,00 0,78 -0,44 -0,04 0,03 0,03 -0,26 -0,15 -0,07 -0,05 -0,31 -0,19 0,03 -0,38 -0,38 -0,52 -0,19 0,01
Gypsum X .. APPENDIX D
Core depth (mcd) 21.47 21.52 21.62 21.72 22.17 22.37 22.77 22.82 22.87 22.92 22.97 23.02 23.07 23.17 23.22 23.27 23.32 23.37 23.42 23.52 23.57 23.62 23.72
A ge(kyB P) 7.69 7.70 7.74 7.77 7.92 7.99 8.14 8.15 8.17 8.19 8.21 8.23 8.24 8.28 8.30 8.32 8.34 8.35 8.37 8.41 8.43 8.45 8.48
Counts (#/cc) A. echolsi B. pseudopunctata B. aculeata C. lobatulus F, earlandi F, fusiformis G. biora G. crassa rossensis M, arenacea 0.4 0.5 0.5 0.2 0.4 0.4 0.8 0.6 1.4 1.5 1.6 1.4 3.1 0.5 0.6 1.2 0.6 2.8 0.6 0.3 0.6 0.5 N, iridea ------P. bulloides ------T angulosa ------T intermedia 0.1 - 0.4 0.1 0.1 -- 0.4 0.2 0.1 --- 0.2 0.2 0.1 0.5 0.1 - N. pachyderma ------
Diversity (#species) 2 1 1 2 2 2 1 1 1 2 1 1 2 2 1 1 1 2 2 2 1 2 1
BFAR (#/cmV‘) 115 135 115 135 115 115 192 154 346 481 404 346 827 154 154 288 154 731 192 96 135 173 115
Q-mode loadings QPCl M. arenacea 0.99 1.00 1.00 0.36 0.99 0.99 1.00 1.00 1.00 0.98 1.00 1.00 1.00 0.99 1.00 1.00 1.00 1.00 0.98 0.98 -0.03 1.00 1.00 QPC2 B. aculeata 0.01 0.04 0.04 -0.14 0.01 0.01 0.04 0.04 0.04 0.00 0.04 0.04 0.03 0.02 0.04 0.04 0.04 0.03 0.00 0.00 -0.16 0.02 0.04 QPC3 F. fusiformis -0.15 0.03 0.03 -0.83 -0.15 -0.15 0.03 0.03 0.03 -0.19 0.03 0.03 -0.04 -0.10 0.03 0.03 0.03 -0.02 -0.19 -0.19 -0.87 -0.08 0.03
Gypsum X _. .. - ...... ■ - X APPENDIX D
Core depth (mcd) 23.77 23,82 23,87 23,92 23,97 24,02 24,12 24,17 24,27 24,37 24,42 24,57 24,62 24,67 24,77 24,87 29,23 29,28 29,33 29,38 29,43 29,48 29,53
A ge(kyB P) 8,50 8,52 8,54 8,56 8,58 8,60 8,64 8,65 8,69 8,73 8,75 8,81 8,83 8,85 8,89 8,93 8,97 8,98 8,99 9,00 9,01 9,01 9,02
Counts (#/cc) A. echolsi ■ - - • 0,1 0,1 ■ - ■ 0,4 B. pseudopunctata B. aculeata 0,1 - 3,1 0,1 - 0,2 - - 0,2 ■ - 0,2 - 0,1 C, lobatulus F. earlandi . - ... .._ . 0,3 F. fusiformis - - - ■ - 0,1 - 0,1 - 2,0 G. biora G. crassa rossensis w M. arenacea 1,5 0,6 1,3 2,4 1,5 1,3 2,8 5,7 0,5 0,5 0,6 1,6 0,4 1,0 0,6 0,4 0,6 0,1 0,5 2,3 1,2 7,8 0,7 w N. iridea ------■ 0,2 P, bulloides - --- 0,1 - --• 0,3 T. angulosa T intermedia 0,3 0,2 . 0,1 0,2 . 0,2 ... 0,2 .. 0,2 . N. pachyderma - .... 0,1 ■ 0,3 . 0,2
Diversity (#species) 32111113311221114413127 BFAR(#/cmV) 32? 596 365 327 692 2212 422 329 375 1126 329 610 375 235 563 282 329 1737 704 4881 2534
Q-mode loadings QPCl M, arenacea 0,99 0,98 1,00 1,00 1,00 1,00 1,00 0,85 0,95 1,00 1,00 0,99 0,91 1,00 1,00 1,00 0,95 0,35 1,00 0,99 1,00 1,00 0,24 QPC2 B. aculeata 0,06 0,00 0,04 0,04 0,04 0,04 0,04 0,50 0,14 0,04 0,04 0,02 0,40 0,04 0,04 0,04 0,25 -0,23 0,04 0,10 0,04 0,04 -0,16 QPC3 F. fusiformis -0,15 -0,19 0,03 0,03 0,03 0,03 0,03 0,01 -0,26 0,03 0,03 -0,10 0,02 0,03 0,03 0,03 0,03 -0,50 0,03 0,04 0,03 0,01 0,56
Gypsum X _ . . . XXX .. . _ ...... A PPEND IX D
Core depth (mcd) 29.58 29.63 29.68
Age (ky BP) 9.03 9.04 9.05 9.06 9.06 9.07 9.08 9.09 9.10 9.10 9.11 9.12 9.14 9.15 9.15 9.16 9.17 9.18 9.19 9.19 9.20 9.23
Counts (#/cc)
A. echolsi 1.8 0.8 0.1 0.1 0.1
B. pseudopunctata 0.5 0.2 0.1 0.1 B. aculeata 2.1 2.5 1.2 9.3 0.2 0.2 0.1 0.3 2.5 30.8 C, lobatulus --- 0.1 F. earlandi 12.1 3.2 1.8
F. fusiformis 18.3 6.3 4.5 0.5 0.9 0.5 0.8 0.1 2.0 0.5 G. biora 4.4 - 0.1 0.2 0.3 0.2 0.2 G. crassa rossensis 2.5 -- 0.9 0.7 0.6 w M. arenacea 5.2 2.2 2.1 1.5 1.2 1.2 1.5 3.2 1.4 3.7 1.8 2.2 2.3 2.6 2.3 2.0 1.6 1.9 5.9 1.1 2.6 2.2 w N. iridea 6.5 1.8 0.4 0.4 0.2 0.2 P. bulloides 1.0 -- 0.1 0.2 0.1 0.1 T angulosa --- 0.1 T intertnedia 0.2 -- 0.1 0.1 0.1 N. pachyderma 2.6 0.8 0.2 0.1 0.2 0.2
Diversity (#spccies) 11 7 8 BFAR(#/cmV‘) 34777 10795 6430
Q-mode loadings QPCl M. arenacea 0.08 0.15 0.30 QPC2 B. aculeata -0.18 0.13 0.07 QPC3 F. fusiformis 0.58 0.53 0.53
Gypsum APPENDIX D
Core depth (mcd) 30.88 30,93 30.98 31.13 31.18 31.23 31.33 31.38 31.43 31.48 31.73 31.78 31.83 31.88 31.93 31.98 33.28 33.33 33.38 33.43 33.48 33.53 33.58
Age(kyBP) 9.24 9.25 9.26 9.28 9.29 9.30 9.32 9,33 9.33 9.34 9.38 9.39 9.40 9.41 9.42 9.42 10.43 10.44 10.44 10.45 10.45 10.46 10,46
Counts (#/cc) A. echolsi B. pseudopunctata B, aculeata 0.40.4 - 11.5 - - - 0.2 0.2 0.5 C. lobatulus 0.2 0,1 F. earlandi F. fusiformis 0.7 G. biora G. crassa rossensis 0.5 0,2 M. arenacea 0.5 0.7 1.5 0.8 0.5 0.5 2.3 0.6 1.2 2.1 0.8 3.1 0.8 0.9 0.7 0,8 1.6 1,5 0,6 2,4 1,0 1 8 1,9 N. iridea P, bulloides T. angulosa 0.1 T, intermedia 0.2O.l o.l N. pachyderm a ...... 0.2
Diversity (#species) 1 1 1 1 1 2 3 1 2 1 2 2 3 6 1 1 2 2 2 1 1 1 1 BFAR (#/cmV‘) ^^9 422 892 469 329 563 1924 375 7744 1267 563 1924 610 1737 422 516 2198 1805 706 2433 1020 1884 1962
Q-mode loadings QPCl Af, arenacea 1.00 1.00 1.00 1.00 1.00 0.78 0.97 1.00 -0.02 1.00 0.99 1.00 0.97 0.72 1.00 1.00 0.93 0.99 0.99 1.00 1.00 1.00 1.00 QPC2 B, aculeata 0.04 0.04 0.04 0.04 0.04 0.61 0.17 0.04 0.95 0.04 0.01 0.04 0.22 0.05 0.04 0.04 0.35 0.02 0.03 0.04 0.04 0.04 0.04 QPC3 F. fusiformis 0.03 0.03 0.03 0.03 0.03 0.01 0.13 0.03 -0.01 0.03 -0.15 0.01 -0.06 0.42 0.03 0.03 0.02 0.05 0.03 0.03 0.03 0.03 0.03
Gypsum X XXX APPENDIX D
34.23 34.28 34.33 34.38 34.43 34.48 34.53 34.58 34,63 34.68 34,73 34.78
Age(kyBP) 10.4' 10.53 10.53 10.54 10.54 10.55 10.55 10.56 10.56 10.57 10.57 10.58 10.58
Counts (#/cc) A. echolsi 0.5 0.1 0.3 0.3 0.2 0.2 ------B. pseudopunctata
B. aculeata 0.1 0.2 0.1 1.1 .. - .. _ . C. lobatulus 0.1 0.3 0.1 - 0.2 0.1 ------F, earlandi
F. fusiformis 0.1 0.1 3.9 0.1 0.1 1.6 0.5 2.4 . . . . _ . G. biora - 4.2 ------0, crassa rossensis 0.4 0.1 0.5 0.6 0.1 0.2 12.8 ------M. arenacea 0.8 0.8 0.8 0.3 2.3 2.7 1.7 1.8 0.6 0.9 1.9 0.7 5.2 6.0 5.8 0.9 GÎ N. iridea 0.1
P. bulloides 1.4 0.1 0.6 0.8 1.0 0.4 ... _ .. T. angulosa 0.1 0.1 0.3 0.1 0.1 - 0.2 ------T. intermedia 0.1 N, pachyderma 0.1 0.4 0.1 0.1 0.2 0.1 0.4 0.1 ------
Diversity (#species) 1 7 7 1 1 5 1 1 1 1 1 1 1 6515 22448 1727 1805 3768 942 1962 706 5338 6122 5965 942
Q-mode loadings QPCl M. arenacea 0.73 0.10 1.00 1.00 0.18 1.00 1.00 1.00 1.00 1.00 1.00 1.00 QPC2 B, aculeata 0.28 -0.19 0.04 0.04 -0.15 0.04 0.04 0.04 0.04 0.04 0.04 0.04 QPC3 F, fusiformis 0.35 0.22 0.03 0.03 0.54 0.03 0.03 0.03 0.03 0.03 0.03 0.03
Gypsum XXXXXX X APPENDIX D
Core depth (mcd) 34.93 34.98 35.08 35.83 35.88 35.98 36.03 36.08 36.18 36.23
Age(kyBP) 10.60 10.60 10.61 10.68 10.69 10.70 10,70 10.71 10.72 10.72
Counts (#/cc) A. echolsi - -- 1.9 0.2 0.5 0.1 B. pseudopunctata - - - B. aculeata --- C. lobatulus -- -
F. earlandi - - - 4.1 1.4 ---- F. fusiformis 0.3 -- - 11.5 0.1 0.1 7.2 0.8 - 0.6 0.5 G, biora 0.2 - 0.4 - 12.5 3.2 0.5 0.2 - 0.9 2.2 G, crassa rossensis 1.2 0.1 3.1 0.2 0.1 3.7 0.5 0.8 2.5 0.2 12.0 - M. arenacea 5.1 2.7 0.3 1.7 2.0 6.7 0.5 1.1 3.2 7.1 0.8 6.1 4.6 1.8 0.1 5.4 1.2 0.1 0.3 w 5\ N. iridea - -- 0.1 . ___ P. bulloides -- - 0.4 0.2 T. angulosa --- 0.1 T, intermedia - -- 0.1 N. pachyderma - -- 0.3 0.1 0.7
Diversity (#species) 4 2 3 BFAR (#/cmV‘) 6986 2826 3846
Q-mode loadings QPCl M. arenacea 0.97 0.97 1.00 0.02 0.02 1.00 1.00 1.00 1.00 1.00 0.96 1.00 1.00 1.00 1.00 0.23 -0.14 -0.09 1.00 1.00 -0.07 0.91 0.97 -0.07 0.04 QPC2 B. aculeata -0.01 -0.01 0.04 0.04 -0.15 -0.15 0.04 0.04 0.04 0.04 0.04 0.00 0.04 0.04 0.04 0.04 -0.24 -0.20 -0.11 0.04 0.04 -0.19 -0.07 0.00 -0.16 -0.15 QPC3 F. fusiformis 0.10 0.03 0.18 13 0.03 0.03 0.03 0.03 0.08 0.03 0.03 0.03 0.03 0.49 0.11 0.02 0.04 0.03 0.57 0.18 0.06 0.20 0.18
Gypsum X XX APPENDIX D
Core depth (mcd) 36.64 36.69 36.74 36.79 36.84 36.89 36.94 36.99 37.04 37.09 37,14 37.19 37.24 37.29 37.34 37.39 37.44 37,49 37.54 37.59 37.64 37.69
A ge(kyB P) 10.76 10.77 10.77 10.78 10.78 10.79 10.79 10.80 10.80 10.81 10.81 10.82 10.82 10.83 10.83 10.84 10.84 10.85 10.85 10.86 10.86 10.87
Counts (#/cc) At €c}\olsi ------0.1 0,1 " 0.1 ------0,4 Bt pS6udopufict(it(x - Bi oculccita ------0.1 0.1 - 0.1 ------C. lobatulus ------0,1 ------0.1 Bt cat“latt(ii Ft fusijbrftus - - 0.1 - - - 2.3 0.1 - 2.2 0.3 - - 0.1 ------
Gt crassa rossensis 0.2 - 0.2 - O.l - 0.4 0,5 - 0.5 0,1 0.1 - 0.4 0.2 ------0.2 Mt arenacea 4.7 2.2 1.5 2.2 2.4 0.4 0,7 2.5 0.5 0.7 0.6 0.6 1.9 4.6 2.8 3.5 1.5 2.9 0.5 2.5 4.7 1.6 iridea ------0.5 ------Pt bulloides 0.1 - 0.2 - - 0,1 - - 0.1 0.1 O.l ------0.1 - - 0.5 Tt angulosa ------O.l ------0.2 Tt mterfnedia O.l - - - - - Nt pachydertna ------0,1 O.l - - O.l O.l - O.l - - 0.5
Diversity (#species) 3141223536632321212116 B F A R ( # / c m \ y ') ^024 2198 2041 2276 2512 471 3532 3297 706 4082 1256 785 2041 5259 3140 3532 1570 2983 706 2512 4788 3375
Q-mode loadings QPCl M. arenacea 1.00 1.00 0.98 1.00 1.00 0.98 0.23 0.98 0.97 0.22 0.89 0.98 1.00 1.00 0.99 1.00 1.00 1.00 0.99 1.00 1.00 0.93 QPC2 B, aculeata 0,04 0.04 0.01 0.04 0.04 0.03 -0.15 0.04 0.17 -0.19 0.05 0.01 0.04 0.03 0.03 0.04 0.03 0.04 0.03 0.04 0,04 -0,04 QPC3 F. fusiformis 0.03 0,03 0.07 0.03 0.03 0.03 0.56 0.08 0.03 0.57 0.30 0,05 0.03 0.05 0.04 0.03 -0.02 0.03 0.03 0.03 0.03 0.05
Gypsum XXX . . APPENDIX D
Core depth (mcd) 37.74 37.79 37.84 37.89 37.94 37.99 38.04 38.09 38.14 38.19 38.24 38.29 38.39 38.44 38.49 38.54 38.59 38.64 38.69 38.74 38.79 38.84 38.89
A ge(kyB P) 10.87 10.8810.88 10.88 10.88 10.8910.89 10.8910.89 10.90 10.90 10.91 10.91 10.92 10.92 10.92 10.93 10.94 10.94 10.95 10.95 10.96 10.96 10.97 10.97 10.98 10.98
Counts (#/cc) A, echolsi 0.6 0.5 1.8 0.3 - - 0,2 - 0,2 • 0,6 - - B. pseudopunctata - - 0.4 0.1 - B, aculeata ----- C, lobatulus 0.1 - - -- F, earlandi -- 0.9 0.1 - 0,2 m m m 6,5 ** " F, fusiformis 0.3 0.1 3.5 0.3 0.6 ------1,9 - 9,9 - 41,4 G, biora -- 0.2 0.1 0.1 ------1,4 0,1 7,8 - 0,2 - - G. crassa rossensis 0.3 0.5 0.9 0.6 2.0 ------0,1 - 1,5 - 1,1 - - Ui M. arenacea 1.2 2.2 2.8 2.7 5.3 0.8 0,7 4,7 2.2 0,5 2,4 0,8 5,5 8,6 3,6 0,8 0,5 0.4 7,1 0.8 5.2 3,2 0.7 00 AuN. irideatrtdcd --- - 0,60.6 0,2 0.2 0,1 0.1 ------0,4 - 0,2 - 4,1 P. bulloides 0.2 - - -- T. angulosa 0.5 ---- T, intermedia ------0,2 --•««-« 0,1 - - - - N. pachyderma 0.8 0.5 2.2 0.9 0,5 ------3,4 0,8 2,9 - 2,2
Diversity (#species) 7 4 8 8 5 BFAR(#/cmV‘) 4003 3846 13658 5338 8791
Q-mode loadings QPCl M. arenacea 0.83 0.96 0.54 0.97 0.94 1.00 1.00 1.00 0.11 0.98 0.44 1.00 0.05 1.00 1.00
QFCZfli m lŒ ia :0ll3 :0l01 :0l20 :0l03 :0.03 m m ■ m 9.92 -9il8 9.91 -9,17 9,91 9,91 QPC3 F. fusiformis 0.20 0.09 0.52 0.14 0.15 0.03 0.03 0.03 0.50 0.04 0.48 0.03 0.56 0.03 0.03
Gypsum APPENDIX D
Core depth (mcd) 38,94 39.14 38.99 39.04 39.09 39.19 39,29 39.34 39.39 39.44 39.49 39.54 39.59 39.64 39.69 39.74 39.79 39.84 39.89 39.94 39.99 40.04
Age (ky BP) 10.99 11.01 10.99 11.00 11.00 11.01 11.02 11.03 11.03 11.04 11.04 11.05 11.05 11.06 11.06 11.07 11.07 11.08 11.08 11,09 11.09 11.10
Counts (#/cc) A. echolsi -- 0,2 0.3 ------B. pseudopunctata ------B. aculeata ------■ C. lobatulus - - 0.2 0.1 0.2 ------F. earlandi --- 0,2 ------1.8 2.8 2.0 0.7 -- F, fusifonnis - 0.2 - 0.6 0.7 - 0.2 ------7.2 12.9 14.5 2.6 • - G. biora - 0.5 0.1 0,2 0,4 - 0.2 ------0.5 0.3 0.5 0.2 - - G. crassa rossensis -- 0.1 0.4 5.5 ------2.5 2.3 3.8 1.6 - - w M. arenacea 0.6 2.0 1.4 1.1 3.4 6.1 14.9 5.2 7.9 3.5 0.8 0.8 0,6 0.5 3.8 2,5 0.5 1.8 1.5 0.3 5.5 3.2 VO N. iridea ---- 0.2 ------0.4 ----- P. bulloides ------T angulosa ------T. intermedia -- ■- •------N. pachydenna - 0.1 0.2 0.5 0.5 - 0,1 ------
Diversity (#spccies) 1 3 1 5 7 1 6 1 3 1 1 1 1 1 1 1 6 5 5 5 1 1
BFAR (# /c m V ‘) 628 2747 1413 1803 5730 6201 22841 5259 8634 3611 863 863 628 549 3846 2512 13265 20565 22684 5573 5573 3218
Q-mode loadings QPCl Af. arenacea 1.00 0.97 1,00 0.96 0.98 1.00 0,94 1,00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 -0.03 0,06 0.02 -0.01 1.00 1.00 QPC2 B. acuieata 0.04 0.00 0.04 -0.01 -0.03 0,04 -0.02 0.04 0,04 0.04 0.04 0.04 0.04 0.04 0.04 0,04 -0.23 -0.19 -0.19 -0.24 0.04 0.04 QPC3 F. fusifonnis 0.03 0.08 0.03 0.05 0.16 0.03 0.11 0.03 0.05 0.03 0.03 0.03 0,03 0.03 0.03 0.03 0.60 0.58 0.59 0,59 0.03 0.03
Gypsum ...... - . ■ . APPENDIX D
Core depth (mcd) 40.09 40.14 40.24 40.29 40.34 40.39 40.44 40.49 40.54 40.64 40.69 40.79 40.84 40.89 40.94 40.99 41.04 41.09 41.14 41.19 41.24 41.29
Age (kyBP) 11.10 11.11 11.12 11.12 11.13 11.13 11.14 11.14 11.15 11.16 11.16 11.17 11.17 11.18 11.18 11.19 11.21 11.22 11.24 11.26 11.27 11.29
Counts (#/cc) A. echolsi ------0.1 ■ 0.1 ----- 0.2 -- 0.1 ---- B. pseudopunctata ------■ ------• ------B. aculeata ------■------C, lobatulus ------F. earlandi ------0.6 - - - 1.1 - - - F. fusifonnis ---- - 0.8 - 2.5 --- -- 5.6 - 0.3 - 21.4 - 0.1 0.3 G. biora •-----■------G. crassa rossensis ------0.1 - 0.2 -- - -- 0.3 0.1 3.0 - - - ■ 0.1 M. arenacea 2.2 1.5 8.4 2.3 9.5 1.9 0.7 4.5 2.2 1.4 1.3 3.6 1.5 0.5 1.6 3.0 1.5 0.5 0.1 2.0 6.5 4.5 u>s> N. iridea ------0.2 - - ■ - - - - P, bulloides ------T. angulosa ------T, intermedia ------N. pachydenna ------0.3 - 0.4 0.2 -- - 0.5 -- 0.2 ---- 0.7
Diversity (#spccies) 1 1 1 1 1 1 4 1 4 1 1 1 1 1 6 2 3 2 3 1 2 3 3140 68298 6061 BFAR(#/cm V‘) 2198 1491 8556 2355 9733 1962 1962 4631 5338 1570 1334 3689 1491 1020 8713 15152 1865 19814 16783
Q-mode loadings QPCl Af. arenacea 1.00 1.00 1.00 1.00 1.00 1.00 0.65 1.00 0.65 1.00 1.00 1.00 1.00 1.00 0.22 1.00 0.39 0.99 -0.05 1.00 1.00 1.00 QPC2 B. aculeata 0.04 0.04 0.04 0.04 0.04 0.04 •0.10 0.04 -0.09 0.04 0.04 0.04 0.04 0.04 -0.16 0.04 -0.13 0.03 -0.15 0.04 0.04 0.03 QPC3 F. fusiformis 0.03 0.03 0.03 0.03 0.03 0.03 0,45 0.03 0.45 0.03 0.03 0.03 0.03 0.03 0.55 0.03 0.22 0.03 0.53 0.03 0.03 0,07
Gypsum ...... X - . ■ APPENDIX D
Core depth (mcd) 41.34 41.39 41.44 41.49 41.54 41.59 41.64 41.69 41.74 41.79 41.84 41.89 41.94 41.99 42.04 42.09 42.14 42.19 42.29 42.34 42.39 42.44 42.49
Age (kyBP) 11.31 11.32 11.34 11.36 11.37 11.39 11.41 11.42 11.44 11.46 11.47 11.49 11.51 11.52 11.54 11.56 11.57 11.59 11.62 11.64 11.66 11.67 11.69
Counts (#/cc) A. echolsi 0.2 B. pseudopunctata B. aculeata
C. lobatulus 0.1 0.1 0.1 0.2 0.2 0.2 -- 0.1 ------F. earlandi 0.9 -- 0.5 0.6 0.2 ------F. fusiformis 0.1 0.3 0.1 21.4 0.2 0.2 3.8 - 4.4 4.7 1.2 - 8.3 ---- G. biora 0.4 0.6 - 4.8 2.2 0.9 ----- 0.1 G. crassa rossensis 0.7 0.9 0.2 1.7 0.2 0.2 2.7 - 19.7 12.5 9.7 - 0.5 ---- Af. arenacea 3.9 7.1 1.9 0.7 5.8 11.8 6.8 3.5 1.8 2.1 1.6 1.7 1.5 3.5 4.0 3.3 3.8 2.5 4.2 0.7 2.6 6.6 8.2 (O N. iridea 0.2 .. 0.5 0.2 . - 0.2 . _ .. P. bulloides T. angulosa T. intermedia 0.1 N. pachyderma 0.2 0.1 0.1 1.1 0.1 0.1 0.1 2.9
Diversity (#species) 43318342113151675141112 BFAR (# /c m \y ') 14452 25874 6760 2098 92541 36597 22145 11189 5361 6294 6294 5128 30070 10723 103030 71795 48019 7692 48485 2098 7925 20047 25175
Q-mode loadings QPCl Af. arenacea 0.98 0.99 1.00 l.OO 0.21 1.00 1.00 l.OO 1.00 1.00 0.98 1.00 0.24 1.00 0.10 0.15 0.30 1.00 0.41 1.00 1.00 1.00 1.00 Q?C2 B. aculeata 0.01 0.02 0.03 0.04 -0.15 0.04 0.03 0.04 0.04 0.04 0.02 0.04 -0.21 0.04 -0.20 -0.21 -0.15 0.04 -0.12 0.04 0.04 0.04 0.04 QPC3 F. fusiformis 0.07 0.07 0,06 0.03 0.55 0,04 0.05 0.03 0.03 0.03 0.03 0.03 0.57 0.03 0.31 0.38 0.25 0.03 0.51 0.03 0.03 0.03 0.03
Gypsum APPENDIX D
Core depth (mcd) 42.54 42.59 42.64 42.74 42.84 42.89 42.94 42.99 43.04 43.09 43.14 43.19 43.24 43.39 43.44 43.59 43.74 43.79 43.94 43.99 44.14 44.19 44.39
Age (kyBP) 11.71 11.72 11.74 11.77 11.81 11.82 11.84 11.86 11.87 11.89 11.91 11.92 11.94 11.99 12.01 12.06 12.11 12.12 12.37 12.39 12.44 12.45 12.52
Counts (#/cc) A. echolsi ...... B. pseudopunctata ...... B. aculeata - ...... C. lobatulus ...... F. earlandi ...... F. fusiformis - 0 . 8 ...... G. biora - 0 . 1 ...... G. crassa r o s s e n s is ...... M. arenacea 1.5 2.0 0.5 0.4 0.5 0.8 1.2 1.8 3.5 1.4 2.0 0.8 2.2 4.3 1.2 6.6 1.4 1.3 13.2 0.4 2.8 1.8 0 (d to N. iridea P. bulloides T, angulosa T. intermedia N. pachyderma ■ 0.1
Diversity (#species) 1 3 111111111111111111111 BFAR (# /c m \y ‘) 4429 9091 1399 1166 1632 2564 3497 5361 10723 4196 6061 2564 6527 13054 3730 20047 4196 3963 40093 1166 8392 5361 1399
Q-mode loadings QPCl M. arenacea 1.00 0.93 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 QPC2 B. aculeata 0.04 -0.02 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 QPC3 F, fusiformis 0.03 0.24 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03
Gypsum X ... .. - X .. X ■ XX XX - XX A P P E N D IX E
Appendix E: Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumulation rates (BEAR) (#/cm^ky'^), Varimax Principal Component Loadings o f Holocene benthic foraminiferal Q-mode assemblages, and occurences of gypsum in core OOP 1099a/b from the Palmer Deep basin IIL List includes only species used in the potential fossil data set.
323 APPENDIX E
Core depth (mbsl) 0,05 0.20 1.55 1.70 2.30 2.50 2.70 2.90 3.05 3.20 3.40 3.60 4.55 4.70 4.90 5.20 5.35 5.50 5.70 6.10 6.85 7,00 7.20 7.40
Counts (#/cc) A. echolsi -- - - 0.1 0.1 ------0.1- -0.1 B. pseudopunctata 5.8 0.3 2.2 0.4 7.1 3.4 1.7 - 2.2 - 7.5 - 1.4 - 1.7 2.0 2.5 2.7 0.6 - 10.2 --- B. aculeata 14.2 4.7 - 0.8 2.4 3.3 0.2 0.1 0.9 9.5 1.1 5.4 0.1 0.3 1.0 4.6 3.2 0.7 - 5.8 -- 0.5 C, lobatulus - E. exigua F, earlandi -- F.fusifomis ------0.1 ------0.1- - - 0.1 --- G. biora G. crassa -- M. arenacea - 0.2 0.1 0.1 0.1 - 0.7 - 0.1 - 0.2 1.8 0.8 0.2 0.3 0.2 0.1 0.2 0.1 0.2 0.6 0.2 0.2 N. pachyderm ------0.1- 0.1 ---- 2.3 0.1 g Nodosaria spp. --- 0.1 ------N, bradii N. iridea 0.1 - - - P. bulloides 1.1 0.1 -. 0.3 0,2 0.5 - 0.2 1.7 0.1 0.6 - 0.1 - 0.8 0.4 -- 1.3 - - 0.4 T. angulosa - ■ - - 0.1 ------■----■--- T. intermedia 0.2 0.1 0.8 0.3 0.5 0.2 0.2 - 0.5 0.2 0.3 0.2 0.3 0.1 0.2 0.2 0.1 - 0.1 0.7 0.2 0.2 0.2 0.3
Diversity (#species) 4 5 3 3 6 5 3 4 4 4 4 5 3 5 5 6 5 4 2 8 2 3 6 BFAR(#/cmV') 14021 3505 2032 508 5740 4216 3607 965 1829 914 12548 1016 6299 660 1575 2337 5436 4216 1067 508 11887 559 1829 1016
Q-mode loadings QPCIM. arenacea -0.07 0.01 -0.11 0.03 -0.13 -0.13 -0.08 0.75 -0.14 0.04 -0.11 0.11 0.27 0.99 -0.05 0.01 -0.06 -0.09 0.15 0.08 -0.12 0.94 0.00 0.27 QPC2 B, aculeata 0.99 0.92 0.30 0.20 0.46 0.84 0.99 0.16 0.36 0.85 0.96 0.86 0.94 0.03 0.51 0.74 0.99 0.95 0.93 -0.14 0.78 -0.09 -0.11 0.52 QPC3 F, fusiformis -0.05 -0.16 0.31 0.23 0.32 0.16 -0.02 -0.20 0.35 -0.24 0.04 -0.21 -0.13 -0.06 0.29 0.22 -0.02 0.07 0.08 -0.07 0.20 -0.06 -0.18 -0.34
Gypsum APPENDIX E
7.60 7.80 8,00 8.35 8,50 9.10 9.70 9.85 10,20 10.40 10.60 11,35 11,50 11,70 12,85 13,00 13,20 13,40 14,35 14,85 14,95 15,00 15,40
Counts (#/cc) A. echolsi 0.1 0.3 0,2 B. pseudopunctata 5.6 0.6 0.8 0.3 11.1 - - 0,1 - 6.1 9,2 8,0 1,3 45,4 4,5 0,1 17,5 0.3 8,5 B. aculeata 4.8 1.9 6.6 11,2 1.5 - 0,1 -- 5.0 3,9 3,4 7,8 20.9 7.8 1,2 8,8 2.8 6,5 C, lobatulus E. exigua F. earlandi ... 0,2 0.5 F.fusifomis --- - 1.3 -- - 0.2 0,8 0,1 0,2 - - - 4,5 -- G, biora G, crassa ... 0,1 0.2 . M. arenacea - 0.1 0.8 0,2 0,9 0,5 0,5 0,6 2,3 0,6 2.9 0,2 0,6 1,2 0.7 1,4 0,6 0.2 0,2 6,2 0,2 1.4 0.3 N. pachyderm - - 0,2 ---- 0.2 0,2 - 0.5 4,8 0.2 - 1.8 0.3 0.2 Nodosaria spp. N. bradii N. iridea 0,7 1,2 0.4 3.3 0.1 7.6 2.2 P. bulloides 0.3 0.3 0,4 0,1 0,1 ----- 0.1 0.2 0.6 0.1 0.1 - 0.1 - T. angulosa T. intermedia 0.2 0.5 0,6 0,1 0,2 0,5 0,5 0.2 0,4 0,2 0.5 0.2 0.2 0,2 0.2 0.1 0.3 - 0,2 0.2 0.5 -
Diversity (#species) 4 5 5 8 2 9 2 3 3 2 6 8 7 2 7 1 7 7 4 2 7 6 7 BFAR(#/cmV‘) 7214 2286 6045 8026 711 10617 660 610 1829 508 9855 10414 8433 864 7214 914 49987 8636 965 4216 26822 3556 12090
Q-mode loadings -0.12 -0.04 0,08 -0,01 0,99 -0,10 0.76 0,95 0,98 0,97 0.26 -0.13 -0.07 0,99 0.04 0,99 -0.14 -0.07 0.10 0.99 -0.17 0.43 -0.12 0.89 0.94 0,93 0.90 -0,07 0,46 -0.13 0.02 -0,05 -0,08 0.84 0.69 0.70 -0,06 0.95 -0,04 0.72 0.99 0.92 -0.05 0.67 0.83 0.85 0.14 -0.12 -0.16 -0.18 -0,05 0,43 -0.07 -0.08 -0,04 -0.06 0.16 0.34 0.26 -0.05 -0.13 -0,04 0.24 0,01 -0.18 -0.04 0.47 -0.19 0.19
Gypsum XX APPENDIX E
16,70 16,90 17,10 17.30 17,85 18.00 18,20 18,40 18,60 18,80 19,00 19,20 19,35 19,50 19,70 19,90 20,10 20,30 20,50 20,85 21,00
Counts (#/cc) A. echolsi 0.2 0,1 0,1 0.1 0,1 0,2 0,1 0,2 0,1 B. pseudopunctata 4,2 2,4 1,1 1.8 0,1 0,2 0,6 4,2 2,9 6,7 3.5 17,0 24,6 63,1 7,8 B. aculeata 1.9 1.1 2,2 6.3 3,2 3.4 1,0 0,9 0,5 7,3 12,4 7,2 0,1 0,8 13,7 10.5 0,1 0,2 13.5 6.2 53,1 12,9 C. lobatulus ■ - - 0.1 0,1 -- 0,1 ■ - -- E. exigua F. earlandi F. fusiformis - 0.5 0,1 - 0,1 -- 0.3 5.8 92.3 18,5 2,9 G. biora G. crassa . . 0,1 M. arenacea 1.2 0.1 0,5 0.5 1,1 0.9 0,3 0,5 0.5 0.5 0.4 0,9 0,6 2,8 0.4 0.8 0.8 1.5 2,7 0.5 --- s N. pachyderma 0.2 0.2 0.4 0,2 0.1 0.5 0,6 0,4 1.4 0.3 0.1 4.7 - 15,4 0,8 Nodosaria spp. N. bradii N. iridea 0,6 0.1 8,7 61,5 84.6 15.5 P. bulloides .. 0.1 0,1 0,3 0,2 0,1 0,4 0,6 0,2 0.9 0.2 1.5 1.4 T. angulosa ------0,1 - T. intermedia 0.1 0.4 - 0,2 0,1 - 0,2 0,2 0,1 - 0,3 0,1 0,1 0.1 0.8
Diversity (#species) 5 4 7 10 9 7 4 5 3 9 9 7 3 2743 1829 4826 7163 4064 4267 965 1219 762 6350 12294 7925 508
Q-mode loadings Q P C I M. arenacea 0.45 -0.07 -0.04 0.01 0.25 0.16 0,27 0.42 0.77 0.02 -0.04 0.05 0.99 0.97 -0,07 0.01 0,99 0.99 0.99 0.16 -0.10 -0.19 -0.16 Q P C 2 B. aculeata 0.89 0.87 0.75 0.99 0.96 0.98 0,89 0,84 0.54 0.92 0.99 0.99 0.05 0.21 1.00 0,99 0.03 -0.05 0,00 0.78 - 0.01 0.56 0,64 QPC3 F. fusiformis -0,06 0,13 0,21 0,01 -0,09 -0,03 -0,18 -0,16 -0,17 0,18 -0,08 -0,06 -0,07 - 0,10 -0,04 -0,05 -0,07 -0,04 -0,06 0,42 0,91 0,36 0,25
Gypsum APPENDIX E
Core depth (mbsl) 21.20 21,60 21,80 22,20 23,00 23,20 23,85 24,00 24,20 24,35 24,50 24,70 25,10 25,50 25,70 26,20 27,00 27,20 27,55 27,95 28,35 29,05 29,45
Counts (#/cc) A. echolsi - - - - 0,3 B. pseudopunctata 9.5 0,5 1.7 4.8 19,2 0.6 8,8 1.6 2,6 0,2 0,6 0,2 0,2 0,6 0.2 0.7 0.4 0.2 1.5 0.2 B. aculeata 6,4 1.1 20.2 33,8 0,9 4,0 9,8 4,2 8,0 5.3 - 0.2 - - - - 0.2 - - 0.5 C. lobatulus E. exigua F, earlandi 0,2 0,1 - 0,1 - - - - 0,2 - 0,1 F. fusiformis 5.5 1,4 8,8 6,4 0,8 1,5 0,6 1.3 0.5 0.5 1.5 0.4 0.5 0.4 0.8 2.9 0.5 G. biora 0. crassa 0.2 0.1 0.1 0.1 M, arenacea 0,1 0,2 - 0,2 0,7 0,2 - 0,6 - 0,2 0.3 0.2 0.1 N. pachyderma 0,3 - - 1,0 1,5 - 0,2 2.4 0,3 0,5 0.4 0.1 Nodosaria spp. a N. bradii N. iridea 40,8 - 0,9 1,6 8,8 5,8 0,5 2.2 0.1 0.7 0.2 0.5 0.7 0.2 0.3 0.2 2.3 P. bulloides 0,2 - 1,4 2,1 0,5 0,3 T. angulosa 0,1 T. intermedia 0,2 0,1 0,1 0.1 0.1 0.1 0.1 0.4 0.1 0.2 0.4 0.1 0.1
Diversity (#species) 7536 lO 248288 l l 57534453683 B FA R ( # /c m ^ y ‘) 41656 1372 2642 19304 48565 711 4521 22606 2946 7976 9550 8484 711 2032 711 813 2083 559 1270 660 1168 4978 559
Q-mode loadings Q P C I M. arenacea -0.14 0.04 -0.15 -0.05 -0.10 0.15 -o.os -0.12 -0.02 -0.03 -0.04 -o.os -0.09 -0.02 -0.11 -0.11 -0.11 -0.12 -0.16 -0.14 -0.01 -0.14 -0.07 Q P C 2 B. aculeata 0.12 0.97 0.I 8 0.97 0.95 o.S9 o.84 0.79 o.S9 o.96 o.9S 0.92 -0.02 0.09 -0.01 -0.06 -0.03 0.04 0.42 0.12 -0.10 0.12 0.03 Q P C 3 F. fusiformis 0.32 -0.09 0,87 -0.11 0.24 -0.19 -0.21 0.53 -0.19 -0.04 0.02 0.25 0,97 0.97 0.99 0.82 0.96 0.98 0.82 0.8I 0.90 0.90 0.95
Gypsum APPENDIX E
Core depth (mbsl) 29.85 30.55 31.35 31.90 32.05 32.25 32.45 32.65 32.85 33.05 33.35 33.41 33.55 33.75 34.10 34.25 34.45 34,65 34.80 34.85 35.00 35.20 35.35
Counts (#/cc) A. echolsi 0.1 - - 0.1 0.2 0.2 0.5 ------0.1 - -- 0.3 - 1.0 B. pseudopunctata 2.0 1.9 - 0.9 0.8 0.2 0.5 - 0.2 - - - - - 7.57.9 1.0 0.2 0.2 1.0 0.7 1.4 2.8 B. aculeata 0.5 0.4 - 0.8 2.4 1.7 9.8 - 0.5 -- - - - 4.0 4.1 2.3 1.0 1.2 0.5 2.2 0.2 3.8 C. lobatulus 0.1 -- E. exigua F. earlandi 0.2 - - 0.2 0.2 0.2 0.2 - 0.2 ----- 0.5 ---- 0.5 - 0.2 1.3 F.jusiformis 4.0 2.0 - 0.4 3.7 0.2 1.8 - 0.2 ----- 0.7 1.2 1.1 0.9 1.7 2.2 2.9 0.8 7.3 G. biora -- G. crassa - 0.1 -- 0.4 0.1 0.2 - 0.2 - - - - - 0.1 - - - 0.2 0.1 0.2 0.1 0.3 M. arenacea 0.1 0.2 0.5 0.9 1.2 0.8 0.5 0.8 1.1 1.1 3.2 0.8 1.2 1.3 0.3 0.5 0.3 0.2 0.2 0.2 0.2 1.9 2.0 N. pachyderma ------0.2 - 0.1 - - - - - 0.1 - - 0.2 0.2 - - 0.1 - Nodosaria spp. - 0.1 ------0.1 ---- 0.1 N. bradii - N. iridea 1.6 0.2 -- 0.3 --- 0.3 ----- 0.8 0.4 0.1 - - 1.0 0.3 0.1 0.5 P. bulloides ------0.3 ------0.3 -- 0.1 0.2 0.2 0.2 - 0.2 T, angulosa ---- 0.1 - 0.1 ------T. intermedia 0.2 0.2 0.4 0.1 0.4 0.1 0.1 ------0.2 0.1 0.2 -- 0.2 -- -
Diversity (#species) 8 8 2 7 10 8 11 1 8 1 1 1 1 1 10 6 7 7 7 9 9 8 10 BFAR(#/cmV‘) 5690 3353 559 2235 6452 2286 9296 559 1676 711 2083 508 813 864 9601 9296 3302 1829 2540 3861 4724 3150 12751
Q-mode loadings QPCI M. arenacea -0.10 -0.06 0.77 0.56 0.23 0.38 0.02 0.99 0.90 0.99 0.99 0.99 0.99 0.99 -0.12 -0.08 0.04 0.12 0.06 -0.09 -0.01 0.74 0.15 QPC2 B. aculeata 0.12 0.30 -0.13 0.66 0.45 0.85 0.89 -0.04 0.30 -0.04 -0.04 -0.04 -0.04 -0.04 0.75 0.75 0.91 0.67 0.46 0.17 0.52 0.22 0,40 QPC3 F. fusiformis 0.98 0.90 -0.07 0.32 0.72 -0.07 -0.03 -0.04 0.05 -0.04 -0.04 -0.04 -0.04 -0.04 0.30 0.35 0.33 0.50 0.65 0.95 0.68 0.47 0.81
Gypsum . ■ . - . . - . . . X . ■.-■.------APPENDIX E
Core depth (mbsl) 35.50 35.70 35.90 36,10 36.30 36.50 36.70 36.95 37.10 37.30 37,50 37.70 38.10 38.30 38.55 38.70 38.90 39,10 39,30 39.50 39.70 39.90 40,05 40.20
Counts (#/cc) A. echolsi 0.1 . B. pseudopunctata 0.1 ------1.2 0.1 - - 0.1 ------0.1 - B. aculeata 3.0 0.1 0.4 - 0.1 8.5 0.1 3.6 0.2 0.1 0.1 0.8 - - -- 0.1 ---- 1.2 - C. lobatulus 0.1 E. exigua F, earlandi 3.5 2.7 F. fusiformis 0.2 0.1 ----- 0.7 -- 16.9 0.2 ------. - 0.1 13.1 G. biora G, crassa ----- 4.3 0.1 0.1 - 0.1 0.6 0.8 - ■ - - - • - - - 0.2 1.5 s M. arenacea 1.8 0.7 1.0 2.8 1.5 1.5 2.5 1.7 1.2 1.6 2.6 1.9 3.1 1.0 2.8 0.8 1.5 1.6 1.2 0.8 1.4 1.8 2.6 0.9 N. pachyderma 0,2 - - - 0.1 2.3 - 0.2 -- 0.2 1.1 ------0.2 - Nodosaria spp. N. bradii N. iridea .. ..-.- 0.1 -- 1.6 1.6 P. bulloides 0.1 - 0.2 .... 0.1 ■ . 0.1 0.1 0.2 - T. angulosa 0.1 T. intermedia -- - 0.1 --- 0.2 ■ - 0.1 ------•--
Diversity (#species) 7 3 3 2 4 4 3 9 3 3 1 9 8 1 1 1 1 2 1 1 1 1 8 4 BFAR(#/cmV') 3556 559 1016 1930 1118 10973 1778 5131 965 1168 1727 16459 5080 660 1880 559 1016 1118 813 508 914 1219 2997 12040
Q-mode loadings QPCI M, arenacea 0.51 1.00 0.94 0.99 0.99 0.08 0.99 0.37 0.99 0.99 0.99 0.07 0.81 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.990.99 0.92 0.03 QPC2 B. aculeata 0.78 0,04 0.28 -0.05 0.00 0.73 -0.02 0.91 0.09 -0.01 -0.04 -0.15 0.06 -0.04 -0.04 -0.04 -0.04 0.00 -0.04 -0.04 -0.04 -0.04 0.35 -0.15 QPC3 F. fusiformis-0.15 0.03 -0.13 -0.04 -0.06 -0.29 -0.05 0.06 -0.04 -0.06 -0.04 0.85 -0.06 -0.04 -0.04 -0.04 -0.04 -0.05 -0.04 -0.04 -0.04 -0.04 -0.12 0.82
Gypsum ...-...... X .. X . X . X -.. X .. APPENDIX E
40,40 40.82 51.54 59.50 60.30 60.50 61.00 61.30 62.20 63.50 65.40 65.60 66.00 66.10 68.60 69.50 69.60 69.80 70.00 70.20 70.60 71.10
Counts (#/cc) A. echolsi B. pseudopunctata 2.8 ------0.1 0.2 0.2 --- 0.1 -- 0.2 0.2 - B. aculeata 24.6 ------0.2 0.1 - 0.2 -- 0.2 0.2 -- 0.9 C. lobatulus 0.1 E. exigua 0.1 0.2 0.2 - 0.2 F. earlandi 0.8 ------0.4 - 0.1 ------0.1 - F.jusiformis 0.8 1.6 - 2.7 0.2 - 2.0 --- 1.6 6.5 1.2 1.7 1.4 ----- 0.1 0.2 G. biora 0.2 0.2 G. crassa 0.2 - M, arenacea 1.3 0.2 ------0.1 0.1 0.1 0.4 0.1 0.2 0.2 0.2 1.5 3.6 2.0 4.1 3.2 1.0 i N. pachyderma 2.7 0.2 - Nodosaria spp. N. bradii N. iridea 18.1 0.9 0.2 0.2 1.1 0.2 0.2 0.2 P. bulloides 0.3 0.1 - 0.1 0.4 0.1 - T. angulosa T. intermedia 0.1 - 0.9 0.3 0.8 1.1 1.2 1.0 0.9 1.1 0.4 0.2 0.2 0.1 0.2 0.7 0.1 0.2 0.2 0.2 0.1 -
Diversity (#species) 3 9 1 3 2 1 3 1 2 2 6 8 7 5 6 2 4 3 4 6 8 5 BFAR(#/cmV‘) 1422 33934 610 2591 711 711 2184 660 660 762 1626 5994 1372 1473 1473 559 1168 2591 1575 3302 2591 1524
Q-mode loadings 0.89 -0.10 -0.03 -0.05 -0.04 -0.03 -0.03 -0.03 0.05 0.04 0.00 0.02 0.00 0.11 0.07 0.19 0.99 0.99 0.99 0.99 0.99 0.75 -0.10 0.73 -0.13 -0.15 -0.16 -0.13 -0.17 -0.13 -0.14 -0.14 -0.14 -0.10 -0.06 -0.13 -0.20 -0.14 -0.04 -0.01 0.01 -0.05 -0.04 0.58 0.41 0.00 -0.06 0.88 0.17 -0.06 0.76 -0.06 -0.06 -0.06 0.88 0.89 0.90 0.87 0.71 -0.07 -0.04 -0.05 -0.07 -0.05 -0.02 -0.09
Gypsum ... X .. XX XX . XXX X APPENDIX E
Core depth (mbsl) 71.50 71,90 72.60 73,20 73,40 73.60 73.80 75.10 77.30 77.70 84.85 85.05 85.45
Counts (#/cc) A. echolsi 0.2 . 0.1 - 0.9 0.2 0.3 0.1 - ■ . . ■ B. pseudopunctata B, aculeata 2.3 2.2 1.0 4.1 8.7 2.8 4.1 0.3 0.2 - -- -
C. lobatulus --- 0.2 0.2 0.1 0.2 ------E, exigua F, earlandi F. JUsiformis 1.8 - 0.9 1.0 2.3 0.1 0.2 - 5.5 1.4 --- G. biora 0.2 0,3 0.6 2.8 4.8 2.2 2.9 0.4 ----- G, crassa - 0.2 -- 1.8 0.2 0.9 ------M. arenacea 2.9 3.2 2.0 3.2 5.3 2.4 1.8 0.2 -- 0.8 0.8 0.8
N. pachyderma -- 0.5 4.2 5.2 0.7 2.4 ------Nodosaria spp. N. bradii N, iridea ------0.4 0.3 --- P. bulloides 0.3 0.4 0.2 0.9 1.6 0.5 0.5 0.2 -----
T. angulosa ---- 0,1 0.1 ------T. intermedia
Diversity (#species) 6 5 8 7 11 10 10 5 3 2 1 1 1 BFAR(#/cmV‘) 5182 4115 3505 10871 20574 6096 8890 813 3962 1118 559 508 508
Q-mode loadings QPCI M. arenacea 0.75 0.85 0.85 0.40 0.38 0.53 0.21 0.32 -0.02 -0.03 0.99 0.99 0.99 QPC2 B. aculeata 0.45 0.46 0.26 0.43 0.57 0.53 0.56 0.37 -0.08 -0.12 -0.04 -0.04 -0.04 QPC3 F. fusiformis0.25 -0.18 0.13 -0.24 -0.23 -0.33 -0.39 -0.38 0.87 0.89 -0.04 -0.04 -0.04
Gypsum . X A P P E N D IX F
Appemdix F: Foraminiferal counts (#/cc), diversity (#species), benthic foraminiferal accumiolation rates (BFAR) (#/cm^ky'^), Varimax Principal Component Loadings of Holocaene benthic foraminiferal Q-mode assemblages, and Varimax Principal Component Scores of Holocene benthic foraminiferal R-mode assemblages of core NBP99/3 JPC18 from tlie Andvord drift. List includes only species used in the potential fossil data set.
332 APPENDIX F
Core depth (mbsf) 0.21 0.26 0.41 0.51 0.56 0.61 0.66 0.71 0.76 0.81 0.91 1.01 1.06 1.11 1.16 1,21 1.26 1.31 1,36 1.41
Counts (#/cc) ccholst ------0.7 ------• - B. aculeata - - - - 0.7 0.3 0.7 ...... B, pseudopunctata - - 0.3 - 1.3 0.3 0.7 0.3 - 0.3 - - - - - E. exigua ...... F. earlandi - - - - 1.7 0.7 ------. - - - 0.7 - F.jusiformis 1.0 1.0 7.7 10.3 31.0 10.0 5.0 1.0 - 1.0 2.0 0.3 - 0.3 - 0.3 0.3 1.3 7.0 1.0 a biora - 0.3 0.7 1.0 4.0 2.0 3.7 ...... 1.0 1.0 1.3 0.3 - - 1.7 - G. crassa rossensis M. arenacea 1.0 1.7 3.0 1.0 3.7 1.7 1.3 0.3 3.3 0.7 0.7 2.7 1.0 1.3 0.7 1.0 0.7 0.3 5.7 4.0 N, bradii 1.0 0 . 3 ...... w Mt iridea ----- 0.3 ------N. pachyderm a ...... T. intermedia 1.3 1.3 2.0 1.0 2.3 1.7 - 2.7 - 1.3 2.0 2.0 2.3 2.7 2.0 2.3 4.3 1.7 0.7 0.7
Diversity (#spccies) 34547964143334343353 BFAR(#/cmV') 597 776 2446 2387 7995 3222 2208 776 597 597 835 895 776 955 716 716 955 597 2804 1014
Q-mode loadings QPCI F.jusiformis 0.45 0.36 0.91 0.99 0.99 0.98 0.84 0.27 -0.08 0.49 0.65 -0.01 -0.08 0.03 -0.06 0.04 -0.01 0.57 0.76 0.15 QPC2T. intermedia 0.70 0.57 0.21 0.07 0.04 0.11 -0.06 0.94 -0.06 0.75 0.70 0.58 0.89 0,88 0,84 0,93 0.99 0,79 0.02 0,10 QPC3 M. arenacea 0,49 0,73 0,33 0,07 0,08 0,12 0,23 0,05 0.98 0.32 0.18 0.79 0.38 0.44 0.30 0.37 0.10 0.10 0.64 0.95
R-mode scores KPCl B. aculeata -0.22 -0.21 -0.10 -0.26 0.87 0.09 0.10 -0.12 -0.18 -0.12 -0.23 -0.18 -0.24 -0.23 -0.25 -0.22 -0.22 -0.23 -0.04 -0.16 PPClF.jusiformis -0.45 -0.46 -0.40 -0.27 0.04 -0.09 -0.07 -0.45 -0.53 -0.44 -0.44 -0.52 -0.43 -0.44 -0.39 -0.46 -0.49 -0.43 -0.37 -0.54 APPENDIX F
Core depth (mbsO 1.46 1.71 1.86 1.96 2.06 2.11 2.16 2.31 2.41 2.46 2.51 2.56 2.61 2.66 2.71 2.76 2.86 2.91 3.00 3.10
Counts (#/cc) A, ccholst ----- 0.3 ------0.3 - - - - Bt üculcütu ------5.7 - 0.3 - - - - - B, pseudopunctata ------q.3 - -7.7 0.7 ---- 0.3 - E. exigua - ...... 1.3 1.0 ------F. earlandi ------9.3 0.3 ------F. fusiformis 2.3 - - 1.7 1.0 0.3 1,3 0,3 0.3 - - 1.3 90.7 27.0 3.3 0.3 - - 2.7 3.0 a biora - - 0.3 2.0 2.0 1.3 1.0 1.0 0.3 - - 20.7 4.0 1.7 ----- G. crassa rossensis ------0.3 - - - - 2.7 -- 0.3 ---- M. arenacea 4.0 0.3 - 3.3 - 2.7 0.7 1.0 3.7 4.0 4.0 0.7 0.3 - 1.0 - 0.7 1.0 -- N. bradii - ...... 1.7 0.7 •----- t N* iridea ------18.7 - 0.3 ---- - N. pachyderma - ...... ------T. intermedia 2.7 4.3 3.3 1.3 2.3 0.7 2.3 2.7 0.3 4.3 1.7 4.3 1.3 1.7 4.0 3.0 2.7 4.3 3.0 0.3
Diversity (#species) 3 2 2 4 3 4 4 5 4 3 2 3 11 7632232 BFAR(#/cmV‘) 1611 835 656 1492 955 955 955 955 835 1551 1014 1134 28640 6325 1909 716 597 955 1074 597
Q-mode loadings QPCI F. fusiformis 0.36 -0.08 -0.07 0.35 0.31 0.04 0.43 0.02 0.01 -0.12 -0.11 0.21 0.98 0.99 0.60 0.01 -0.09 -0.09 0.62 0.98 QPC2 T. intermedia 0.48 0.99 1.00 0.28 0.77 0.17 0.85 0.92 0.03 0.72 0.34 0.96 -0.06 0.03 0.77 0.98 0.97 0.97 0.76 0.09 QPC3 M. orenocea 0.75 0.03 -0.04 0.85 0.03 0.95 0.23 0.33 0.99 0.65 0.91 0.09 -0.06 -0.03 0.16 -0.08 0.19 0.17 -0.07 -0.04
R-mode scores KPCl B. aculeata -0.16 -0.22 -0.24 -0.22 -0.28 -0.31 -0,24 -0.19 -0.18 -0.04 -0.16 -0.22 8.27 0.90 -0.06 -0.29 -0.22 -0.21 -0.13 -0.24 RPC2F. fusiformis -0.55 -0.48 -0.44 -0.41 -0.33 -0.32 -0.40 -0.33 -0.52 -0.60 -0.57 -0.47 2.49 -0.17 -0.43 -0.24 -0.47 -0,50 -0.42 -0.38 APPENDIX F
4.40 4.50 4.55 4.60
Counts (#/cc) A. echolsi - 0.3 0.7 B. aculeata 1.0 1,0 - 1.3 - - -
B. pseudopunctata 1.3 0 . 7 ...... 0.3 1.0 - 3.7 -
E. exigua - 1.0 - 0.7 - F. earlandi 2.3 6.0 - 2.7 - F. fusiformis 43.0 - - - 3.7 ------1 . 7 128.0 0.3 47.7 - G. biora 7.0 6.3 0.3 6.0 - - - - 1.0 0.7 2.7 0.3 - 0.7 9.3 1.3 2.0 0.3 G, crassa rossensis 1.0 0.3 0.3 ------1.7 - 1.7 - M, arenacea 0.7 2.7 0.3 - - - 0.3 0.3 2.3 2.7 1.3 3.0 0.7 3.0 0.3 1.0 2.0 0.7 N. bradii 3.7 a 4.0 - 2.0 - N. iridea 6.0 4.3 - 0.7 - N. pachydenrm 1.0 - T, intermedia 0.7 1.3 4.0 1.0 2.7 1.3 3.0 3.3 1.0 0.7 4.3 1.0 2.0 1.0 5.0 1.0 0.70.7 3.33.3 3.7 3.7 2.32.3
Diversity (#species) 10 11 4 11 3 BFAR(#/cmV‘) 11933 28222 1074 12232 597
Q-mode loadings QPCI F. fusiformis 0.99 0.99 0.02 0.98 -0.09 QPC2 T. intermedia -0.04 -0.03 0.93 0.03 0.97 QPC3 M. arenacea -0.04 -0.04 0.27 -0.02 0.24
R-mode scores RPCl B. aculeata 0.79 2.54 -0.24 1.88 -0.23 mRPC2 : i F. fusiformis 1.61 -0,52 -0.48 0.06 -0.53 -0.11 -0.47 -0.47 -0.51 -0.51 -0.46 -0.38 -0.29 -0.51 -0.48 -0.37 2,83 -0.42 1.31 -0.45 APPENDIX F
Core depth (mbsf) 4.65 4.70 5.35 5.45 5.50 5.65 5.70 5.75 5.80 5.85 5.90 5.95
Counts (#/cc) A. echolsi 0.3 0.3 0.3 - 0.3 - 0.3 0.3 0.3 B. aculeata 1.0 - 2.7 0.3 0.3 - - 0.7 0.3 - 0.3 - 0.3 0.3 -- 0.3 0.7 - B. pseudopunctata 0.7 1.0 - 1.0 0.7 0.7 5.3 0.3 0.7 5.7 -- E. exigua -- -0.3------F. earlandi - 0.3 0.7 4.0 1.0 0.7 4.0 - - 2.7 -- F. fusiformis 0.3 3.0 6.0 1.3 - - 1.3 - 1.7 24.0 23.0 10.3 31.7 2.3 4.0 33.0 2.7 - G. biora -- 4.0 2.0 1.0 - 0.3 1.0 3.7 0.3 5.7 - 0.3 0.3 2.0 - G, crassa rossensis -- 0.3 - - 0.3 M. arenacea 0.3 0.7 1.0 0.7 0.7 0.3 0.3 1.3 1.7 0.7 0.3 1.7 3.3 w ------N. bradii -- - 0.7 -- 0.7 - 1.0 - 0.3 1.3 -- A N. iridea -- - - 0.3 - 4.0 1.7 0.3 1.7 - 1.7 1.3 0.7 - N. pachyderma ------0.7 -- T, intermedia 0.7 2.0 2.7 0.3 0.7 1.7 1.3 1.0 1.0 0.3 0.3 0.7
Diversity (#species) 5 5 5 9 8 8 9 4 7 10 6 2 BFAR(#/cmV‘) 597 1313 1134 6384 5668 2685 9368 955 1551 8234 1432 716
Q-mode loadings QPCI F, fusiformis 0.03 0.77 0.44 0.97 1.00 0.98 0.98 0.74 0.91 0.97 0.76 -0.09 QPC2 T. intermedia 0.38 0.51 0.85 -0.05 -0.01 0.12 -0.02 0.30 0.14 -0.05 0.02 0.14 QPC3 M. arenacea 0.05 0.08 0.13 -0.05 -0.02 -0.03 -0.02 0.53 0.05 -0.06 0.49 0.96
R-mode scores RPCl B. aculeata 0.49 0.07 -0.19 1.34 -0.01 0.20 2.26 -0.10 -0.07 2.12 0.14 -0.17 RPC2tæC2 F. fusiformis -0.56 -0.28 -0.72 -0.43 -0.25 -0.50 -0.34 -0.51 -0.40 -0.45 -0.26 0.18 0.33 -0.19 0.73 -0.45 -0.25 0.51 -0.47 -0.53 APPENDIX F
Core depth (mbsf) 6.00 6.05 6.10 6.15 6.20 6.25 6.30 6.35 6.40 6.50 6.55 6.60 6.70 6.75 6.80 6.85 6.90 6.95 7.05 7.10
Counts (#/cc) A. echolsi 1.0 1.0 0.3 ------B. aculeata 1.3 7.7 - 0.7 B. pseudopunctata - 2.0 0.3 0.3 - 0.7 2.0 - 0.3 ------1.7 - - 0.7 E. exigua 4.0 2.7 0.3 0.7 F. earlandi - 3.0 - 3.7 - 1.0 1.3 - 2.0 - - - 1.0 -- 3.0 4.3 -- 2.7 F. fusiformis 22.7 46.0 12.0 42.7 0.7 24.3 15.3 0.3 57.7 - 2.7 - 32.7 1.0 4.7 96.3 115.0 -- 50.3 G. biora 3.7 11.3 1.7 2.3 0.7 2.0 1.0 - 9.3 - 2.3 - 0.7 - 1.0 21.7 48.0 0.7 - 5.0 G, crassa rossensis 2.7 1.0 - 0.7 ---- 2.0 ------4.0 --- M. arenacea 3.0 2.7 - 1.3 -- 1.7 0.7 2.7 3.0 0.7 0.7 0.3 1.7 --- 6.0 1.0 0.7 N. bradii 0.7 1.3 -- 0.7 ------1.3 -- 4.0 w N. iridea 4.3 13.3 - 1.7 - 0.7 ------0.7 - 13.0 8.7 -- 2.3 N. pachyderma 1.3 - T. intermedia 1.3 2.3 3.3 2.7 2.3 0.7 2.0 4.7 1.0 1.7 5.0 3.3 1.0 5.7 0.7 2.7 3.0 2.0 3.7 1.7
Diversity (#species) 10 11 5 10 466372425435 8328 BFAR(#/cmV‘) 8055 16707 3162 10143 776 5251 4177 1014 13425 835 2088 895 6444 1611 1134 24463 33294 1551 835 12053
Q-mode loadings F. fusiformis 0.98 0.97 0.96 0.99 0.19 1.00 0.97 -0.02 1.00 -0.11 0.40 -0.12 0.99 0.07 0.99 0.99 0.97 -0.10 -0.10 0.99 q?C2 T. intermedia -0.04 -0.04 0.25 0.02 0.93 0.00 0.09 0.99 -0.01 0.45 0.86 0.94 0.01 0.95 0.12 -0.01 -0.01 0.27 0.96 -0.01 QPC3 M. arCTWceo 0.04 -0.03 -0.04 -0.02 -0.06 -0.03 0.05 0.09 0.02 0.86 0.08 0.11 -0.02 0.22 -0.01 -0.03 -0.01 0.95 0.21 -0.03
R-mode scores KPCIB. aculeata 4.79 7.95 0.17 1.67 -0.30 0.09 0.67 -0.22 0.27 -0.18 -0.56 -0.51 -0.20 -0.21 -0.27 -0.44 0.23 -0.13 -0.21 -0.02 m : 2 F fusiformis -0.96 -1.04 -0.36 0.30 -0.29 0,12 -0.13 -0.49 1.49 -0.54 0.01 -0.13 0.23 -0.50 -0.31 2.80 5.76 -0.60 -0.50 1.48 APPENDIX F
Core depth (mbsf) 7.15 7.20 7.25 7.30 7.35 7.40 7.45 7.50 7.55 7.60 7.65 7.70 7.75 7.80 7.85 7.90 8.06 8.16 8.21 8.26
Counts (#/cc) A. echolsi B, aculeata --- 1.0 - 0.3 ------0.3 ----- 0.3 B, pseudopunctata 0.3 0.3 - 0.3 0.7 - 0.3 -- 0.3 0.7 1.0 0.7 ------E. exigua 0.7 0.3 - 0.3 ------F. earlandi 2.0 1.0 - - - - - 0.7 -- 0.7 1.3------F.jusiformis 46.3 32.3 - 44.7 24.0 8.3 1.7 12.3 5.0 14.0 23.7 80.7 54.0 2.3 0.7 0.3 - - 2.7 - G. biora 4.0 2.3 0.3 21.0 6.3 1.7 2.0 3.3 1.0 0.7 4.7 32.0 17.7 0.7 2.7 1.3 - 0.3 1.3 1.0 G. crassa rossensis - 0.7 - - - 1.0 - 1.3 - - - 4.0 0.3 0.7 - 1.7 ---- M. arenacea 0.3 - 5.7 1.3 0.7 9.0 4.3 1.0 - - - 5.7 8.3 - 0.3 2.0 5.7 0.3 4.7 0.3 N. bradii 2.3 0.3 - 12.3 ------18.7 5.7 ------00 N. iridea 9.3 4.0 - 2.7 8.0 ---- 4.0 4.0 4.3 12.7 ------N. pachyderma - 0.7 - - 4.3 0.3 - 0.3 - 0.3 2.7 2.3 1.0 - 0.3 ----- T. intermedia 1.0 0.7 0.7 1.0 3.7 1.7 1.0 1.3 2.3 0.3 0.3 1.0 3.3 0.7 1.0 - 1.0 3.3 2.3 3.0
Diversity (#species) 9 10 3 9 7 7 5 7 3 6 7 10 9 5 5 4 2 3 4 4 BFAR(#/cmV‘) 11874 7637 1193 15155 8532 3998 1671 3640 1492 3520 6563 27029 18556 835 895 955 1193 716 1969 835
Q-mode loadings QPCI F. fusiformis 0.99 0.99 -0.09 0.92 0.95 0.64 0.28 0.98 0.91 0.97 0.99 0.95 0.97 0.92 0.25 0,02 -0.09 -0.08 0.40 -0,08 QPC2 T. intermedia -0.04 -0.03 0.06 -0.04 0.07 0.07 0.15 0.07 0.42 -0.04 -0.04 -0.05 -0.01 0.22 0.34 -0.11 0.12 0.99 0.37 0.96 QPC3 M. arenacea -0.05 -0.05 0.98 0.01 -0.05 0.75 0.93 0.05 -0.03 -0.07 -0.05 0.04 0.11 -0.06 0.19 0.73 0.97 0.06 0.84 0.08
R-mode scores RPCl B. aculeata 0.48 0.27 -0.14 -0.74 -0.57 0.19 -0.09 -0.03 -0.26 -0.25 -0.25 -1.62 -1.00 0.03 -0.31 -0.03 -0.13 -0.23 -0.18 -0,05 RPC2 F. fusiformis 1.04 0.54 -0.59 3.09 0.92 -0.29 -0.44 0.34 -0.33 0.00 0.62 7.03 2.64 -0.25 -0.26 0.07 -0.61 -0.45 -0.49 -0.49 APPENDIX F
Core depth (mbsf) 8.31 8.36 9.10 9.15 9.20 9.25 9.30 9.35 9.40 9.45 9.50
Counts (#/cc) A. echolsi ------0.3-
B, aculeata -- - - - 0,7 - - - - B. pseudopunctata 0.7 0.3 - - - 0.7 - - - - ______1.7 0.7 E. exigua 0.3 ------0.3 -
F. earlandi 1.3 - . . . 2,3 . ------4.0 0.7 F. fusiformis 82.0 15.3 0.3 - 0.3 36,3 41.0 - 24.0 1.3 13.0 - - - - 74.7 13.3
G. biora 5.7 0.7 1,0 5.0 - - 0.7 1.0 - 0.3 0.3 - - - 2.0 1.3 G. crassa rossensis 1.7 3.3 ------0.7 0.3 M. arenacea 2.7 1.7 0.3 0.3 0,3 0,3 1,0 2,0 1,0 0.7 1.0 -- 0.3 1.0 1.3 2.7 - 0.3 N. bradii 0.3 0.3 ... 1.0 .... 15 N. iridea 3.0 - - - - 24.3 12.7 0.7 ...... 0.3 - vo N, pachyderma - 3.3 0.7 0.3 - - - - - 1.0 1.0 T, intermedia 3.3 1.0 2.7 5.0 4.3 2.3 1.0 3.3 3.7 2.0 6.3 1.7 3.3 6.7 2.7 4.0 5.3 2.0 4.7 2.3
Diversity (#species) 10 8 6 3 3 3 2 2 2 9 8
BFAR(#/cmV‘) 18079 4654 5191 895 3580 597 895 1193 835 16050 3580
Q-mode loadings QPCI F. fusiformis 0.99 0.94 0.99 0.30 0.88 -0.08 -0.09 -0.09 -0.11 0.99 0.98 QPC2 T. intermedia 0.01 -0.01 0.04 0.94 0.45 0.99 0.97 0.97 0.57 0.03 0.14 QPC3 M. arenacea 0.00 0.03 0.00 -0.07 -0.05 0.09 0.19 0.19 0.78 -0.04 -0.03
R-mode scores RPCl B. aculeata 0.52 0.03 -0.33 -0.25 -0.25 -0.23 -0.21 -0.20 -0.18 1.21 0.05 RPC2 F. fusiformis 1.48 1.07 0.00 -0.41 -0.31 -0.44 -0.50 -0.53 -0.53 1.22 0.03 APPENDIX F
Core depth (mbsf) 9.65 9.70 9.75 9.80 9.85 9.90 9.95 10.00 10.35 11.25 11.30 11.40 11.95 12.05 12.30 12.65 13.05 13.10 13.55 13.60
Counts (#/cc) A. ccholsi _____ 2.3 ______0.3 _ _ _ B, üculcüîd - ______0,3 B, pscudopunctüici ■ _____ 0.7 _____ . . . _ Bl, cxi^uu - ______. 0.7 F. corlüfidi - _____ 4.0 _____ F.fusifomis 2.3 4.0 - - 0.7 11.7 72.3 71.0 66.0 3.3 0.7 G. bioro - ______2.7 1.0 - - 0.3 _ _ _ 3.7 12.7 0.3 G. crassa rossensis ...... M. arenacea 1.0 1.3 3.7 4.0 2.0 0.3 1.0 2.0 2.0 1.0 0.7 3.0 3.3 4.7 7.3 4.3 0.7 5.0 0.7 2.3 N, bradii _ _ _ _ _ q.7 1.3 ------N, iridea - ...... - 48.7 11.0 N> pachyderma - _____ 0.3 _____ - - - - 12.7 2.0 T. intermedia 3.7 2.3 - 4.0 9.3 5.0 4.0 12.0 2.3 3.0 2.0 0.7 0.3 0.7 0.3 0.3 - 0.3 0.7 1.7
Diversity (#species) 33123472233223223854 BFAR(#/cmV‘) 1253 1372 656 1432 2148 3580 14976 2506 776 1193 656 656 656 1014 1372 835 21599 17840 3461 895
Q-mode loadings QPClF./j«//omj« 0.47 0.81 -0.08 -0.11 -0.02 0.89 0.98 -0.09 -0.11 -0.04 -0.07 -0.10 -0.09 -0.09 -0.08 -0.09 0.83 0.97 0.29 0.13 Q?C2 T. intermedia 0.85 0.48 -0.06 0.69 0.98 0.36 0.03 0.98 0.75 0.76 0.89 0.16 0.04 0.09 -0.01 0.02 -0.09 -0.06 0,03 0.55 QVC3M. arenacea 0.17 0.24 0.98 0.68 0.16 -0.05 -0.03 0.11 0.62 0.29 0.30 0.96 0.98 0.98 0.98 0.98 -0.09 0.01 0.14 0.81
R-mode scores KPCl B. aculeata -0.22 -0.22 -0.17 -0.15 -0.18 -0.97 0.56 -0.17 -0.20 -0.27 -0.24 -0.18 -0.17 -0.16 -0.10 -0.16 -1.15 -0.41 -0.62 -0.20 BPC2F.fusifomis -0.46 -0.44 -0.54 -0.60 -0.59 0.60 1.05 -0.63 -0.51 -0.34 -0.41 -0.52 -0.53 -0.56 -0.66 -0.56 2.66 1.77 0.47 -0.49 APPENDIX F
Core depth (mbst) 13.65 13.80 13.82 13.95 14.00 14.05 14.20 14.30 14.35 14.55 14.65 14.70 14.80 14.85 14.95 15.00 15.20 15.45 15.50 15.55
Counts (#/cc) A. echolsi ...... B. aculeata .0.3 - B. pseudopunctata ...... E, exigua - - - - 0.3 0 . 3 ...... F, earlandi ...... F.jusiformis 96.3 - - 47.7 21.0 34.3 12.7 11.3 1.0 3.3 15.0 8.0 16.3 80.3 8.0 0.7 2.3 G. biora 26.0 - 2.7 4.7 2.7 5.7 - - - 0.7 0.3 0.7 4.7 14.7 - 0.3 6.7 40.7 12.7 7.3 G. crassa rossensis ...... M. arenacea - - 4.3 - 0.7 .. 3.7 . 0.7 0.7 4.0 1.3 0.7 0.3 0.3 2.7 1.3 2.0 TV. bradti . . . . . --- 0.7 ------N. iridea 48.7 - - 12.7 - - - -1.3------13.7 --- N. pachyderma - - - 0.7 0.3 ---- 0.3 0.3 - - - - - 0.3 0.3 - T, intermedia - 4.0 0.7 3.7 3.3 0.7 - 0.3 0.7 2.0 0.7 0.7 2.3 - 2.0 0.3 0.7
Diversity (#species) 3 1 3 4 1 1 2 4 5 5 4 4 3 4 4 5 6 4 BFAR (#/cmV‘) 30609 716 1372 11754 656 597 776 2745 2327 597 2506 5668 1671 3461 18079 9606 2804 2208
Q-mode loadings QPCI F. fusiformis 0.91 -0.07 -0.05 0.98 -0.07 -0.07 -0.09 0.99 0.99 0.68 0.48 0.78 0.98 0.98 0.99 0.24 0.09 0.33 QPC2 T. intermedia -0.07 0.99 0.09 -0.05 0.99 0.99 0.12 -0.04 0.00 0.43 0.27 0.02 0.06 0.12 -0.04 0.05 0.02 0.07 QPC3 M. arenacea -0.06 -0.05 0.93 -0.05 -0.05 -0.05 0.97 -0.04 0.03 0.48 0.66 0.12 0.05 -0.02 -0.04 0.17 0.21 0.36
R-mode scores RPCl B. aculeata -1.66 -0.23 -0.21 -0.65 -0.23 -0.23 -0.17 -0.35 -0.27 -0.26 -0.26 -0.55 -0.24 -0.26 -0.71 -1.07 -0.30 -0.36 RPC2 F. fusiformis 4.31 -0.47 -0.42 1.06 -0.46 -0.46 -0.55 -0.04 -0.24 -0.37 -0.27 0.52 -0.34 -0.22 1.58 1.81 0.18 -0.06 APPENDIX F
Core depth (mbsf) 15.65 15.70 15.75 15.75 15.95 16.00 16.05 16.15 16.55 16.80 17.35 17.40 17.70 17.75 17.80 17.85 18.05 18.15 18.20 18.25
Counts (#/cc) A. echolsi ...... B, oculetUo 0.3 0.3 ...... 0.7 - - .... B. pseudopunctata ...... E. exigua ...... F. earlandi ...... F. fusiformis 1.0 7.7 - - 4.3 60.7 54.3 2.3 14.0 - 5.7 10.7 - 1.0 1.0 4.0 6.0 7.0 8.7 7.0 G. biora 5.3 2.7 - - 2.7 3.0 1.7 0.7 - - 0.3 - 0.7 2.0 1.7 - - 0.3 0.3 0.7 G. crassa rossensis .0.3 - - M. arenacea 0.7 0.3 4.3 4.3 - - 0.3 0.3 0.7 3.3 2.0 0.3 2.0 0.3 - 0.7 - 0.7 - lé N. bradii - - - - 0.3 1 . 3 ...... N, iridea . . . . 4.0 0.7 . . . . . 13.0 . . . . . 1,7 N. pachyderrrui - - - - 0.7 1.0 1.0 - 2.7 - 1.0 3.7 - - - - 0.3 0.7 - 1.0 T, intermedia 1.3 0.3 0.7 0.7 - - - 0.7 - 0.7 3.0 - 1.0 1.0 1.3 0.7 0.3 0.3 1.0 0.3
Diversity (#species) 5 5 2 2 5 5 4 4 3 2 5 4 3 5 3 3 3 7 3 4 BFAR(#/cmV‘) 1551 2029 895 895 2148 11933 10263 716 3103 716 2148 4952 656 895 716 955 1193 1969 1790 1611
Q-mode loadings QPCI F. fusiformis 0.21 0.98 -0.09 -0.09 0.72 0.99 0.99 0.95 0.97 -0.09 0.83 0.61 -0.09 0.41 0.45 0.96 0.98 0.97 0.99 0.99 QPC2 T. intermedia 0.24 0.02 0.10 0.10 -0.12 -0.03 -0.02 0.25 -0.04 0.14 0.43 -0.14 0.40 0.41 0.61 0.14 0.03 -0.02 0.10 0.01 QPC3 M. arenacea 0.21 0.04 0.97 0.97 -0.07 -0.03 -0.02 0.12 -0.01 0.96 0.25 -0.12 0.91 0.18 0.04 0.12 -0.04 0.02 -0.03 -0.04
R-mode scores RPCl B. aculeata -0.14 -0.10 -0.15 -0.15 -0.43 -0.59 -0.43 -0.25 -0.42 -0.17 -0.27 -0.67 -0.21 0.13 -0.27 -0.23 -0.27 -0.27 -0.26 -0.33 RPC2 F. fusiformis -0.24 -0.27 -0.57 -0.57 0.07 0.91 0.49 -0.37 0.00 -0.53 -0.33 0.60 -0.46 -0.48 -0.33 -0.40 -0.31 -0.11 -0.30 -0.20 APPENDIX F
Core depth (mbsf) 18.30 18.50 18.60 18.65 18.90 18.95 19.00 19.05 19.10 19.45 19.50 19.55 19.60
Counts (#/cc) A. echolsi B, aculeata 0.3 -- 0.3 ----- 2.3 1.0 0.3 - B. pseudopunctata --- 0.3 ------0.3 - E. exigua -- 1.0 - - - 0.3 - - - - 0.3 - F. earlandi F.jusiformis - 4.7 32.7 11.3 13.0 24.0 15.7 28.7 2.0 54.7 0.3 34.7 1.7 G. biora 2.0 1.3 3.0 2.3 - 0.7 1.7 4.7 6.0 12.0 2.0 9.0 9.3 G, crassa rossensis ------0.3-- M. arenacea 1.0 0.3 - 1.3 1.0 0.3 1.0 0.3 8.7 8.0 -- 4.0 N, bradii ------1.0 0.3 0,3 --- I N. iridea -- 4.7 -- 4.3 1.3 4.7 - 1.3 - 0.3 - N. pachyderma ---- 0.7 0.7 1.0 -- 1.3 - 1.7 - T intermedia 0.7 - - 1.3 - - - 0.7 0.3 0.3 1.7 --
Diversity (#species) 4 3 4 6 3 5 6 6 5 8 5 7 3 BFAR(#/cmV‘) 716 1134 7399 3043 2625 5370 3759 7160 3103 14380 955 8353 2685
Q-mode loadings QPCI F.jusiformis -0.03 0.99 0.99 0.99 0.98 0.98 1.00 1.00 0.16 0.99 0.07 0.99 0.19 QPC2 T. intermedia 0.27 -0.02 -0.04 0.09 -0.03 -0.05 -0.04 -0.02 -0.02 -0.03 0.61 -0.03 -0.02 QPC3 M. arenacea 0.52 0.07 -0.04 0.10 0.04 -0.04 0.02 -0.03 0.90 0.13 -0.01 -0.01 0.50
R-mode sccffes RPCl B. aculeata -0.06 -0.27 0.61 0.03 -0.29 -0.39 -0.02 -0.53 -0.23 0.83 0.36 0.06 -0.36 RPC2 F. fusiformis -0.43 -0.30 -0.07 -0.28 -0.21 0.17 -0.15 0.56 -0.29 0.38 -0.47 0.48 -0.02 A P P E N D IX G
^pendix G: Foraminiferal counts (#/cc), diversity (#spedes), benthic foraminiferal accumulation rates (BFAR) (#/cm^ky'^), Varimax Princçal Component Loadings o f Holocene benthic foraminiferal Q-mode assemblages, and Varimax Principal Component Scores of Holocene benthic foraminiferal R-mode assemblages of core NBP99/3 JPC28 from the Gerlache Strait. List includes only species used in the potential fossil data set.
344 APPENDIX G
Core depth (mbsf) 0.07 0.37 0.42 1.07 1.12 1.42 1.47 1.62 3.02 3.22 3.72 3.87 4.47 4.62 4.72 4.77 4.82 4.92 5.12 5.17 5.27
Counts (#/cc) A. ccholsi - - - - 0.7 ------0.3 0.3 Bt Qculcotct - - — - 0.7 ------Bt pscudopiifictoto 0.7 - - - 0.3 ------1.7- C. lobaiulus ------Et exigua ------Ft fusifoTttiis 0.7 - 0.3 0.3 ------16.0 4,3 - - - - 0,3 ^j. biora ------0.3 ------Gt crassa rossensis - - - - 0,3 ------0,3 ------Mt arenacea 1.7 2.0 1.7 8.3 1.3 1.0 3.0 0.3 0.3 5.3 1.3 4.0 1.7 0.3 0.7 2.3 2.7 3.7 1.0 1.0 4.0 ^ Nt bradii ------1.0 0,3 6 N. iridea 5.7 0.3 - - - - 1.7 - bit pachyderma ------0.3 - - - - 1.0 - r. angulosa Tt intermedia 2.0 1.3 4.3 1.3 1.3 2.3 0.7 4.7 3.0 0.7 2.0 0.7 2.3 1.7 1.0 2.7 0.7 2.7 2.7 1.3 0.3
Diversity (#spccies) 423362222322257222273 BFAR(#/cm2ky-l) 1500 1000 1900 3000 1400 1000 1100 1500 1000 1900 1000 1400 1200 7400 2200 1500 1000 1900 1100 2200 1400
Q-mode faunas Q?ClTt intermedia 0.76 0.59 0.96 0.18 0.64 0.95 0.24 1.00 1.00 0.14 0.87 0.19 0.85 0.00 0.13 0.79 0.27 0.63 0.96 0.39 0.10 Q K 2 Ft JUsiformis 0.23 -0.02 0.06 0.02 -0.14 -0.02 -0.02 -0.01 -0.01 -0.03 -0.02 -0.02 -0.02 0.98 0.97 -0.02 -0.02 -0.02 -0.02 0.09 -0.03 Q?C3 Mt arenacea 0.56 0.80 0.27 0.98 0.59 0.31 0.97 -0.03 0.01 0.98 0.49 0.98 0.52 -0.08 0.05 0.61 0.96 0.78 0.26 0.19 0.99
R-mode faunas BPCl Ft JUsiformis -0.51 -0.44 -0.75 -0.10 -0.75 -0.60 -0.32 -0.87 -0.70 -0.15 -0.54 -0.27 -0.56 0.61 -0.25 -0.56 -0.34 -0.49 -0.63 -0.18 -0.24 BtPClBt aculeata -0.20 -0.25 -0.47 -0.13 1.51 -0.34 -0.19 -0.52 -0.40 -0.15 -0.31 -0.17 -0.33 -0.44 0.71 -0.34 -0.19 -0.31 -0.36 1.05 -0.09 APPENDIX G
Core depth (mbsf) 5.42 5.47 5.52
Counts (#/cc) A. echolsi B. aculeata 0.3 0.7 3.0 ...... 0.7 0.7 B, pseudopunctata 0.7 0.3 8.0 3.0 ------0.7 - - 1.0 C, lobatulus - 0.3 - E, exigua - 0.3 - 0.7 ------1,0 - - - - F. fusiformis 26.0 2.3 0.7 2.0 8.0 - 1.0 1.3 - - - 12.0 0.7 - 7.0 G. biora -- - 0.7 ------1,3 G. crassa rossensis -- 0.3 M. arenacea 8.3 1.0 2.7 N. bradii 2.0 - 1.3 0.3 0.7 N, iridea 4.0 -- 1.0 N, pachyderma - 0.3 2.3 0.3 T angulosa - 0.7 - 0.3 T. intermedia 0.7 0.7 0.3
Diversity (#spccies) 79822223 10 244222532632 BFAR (#/cm2ky-l) 12600 2000 5600 1300 1200 1100 1100 1000 6000 1400 1100 1400 1600 1000 1400 5600 1300 1100 5100 1500 1200
Q-mode faunas QFCl T. intermedia -0.06 0.11 -0.11 1.00 0.93 0.81 0,99 0.25 0.34 1.00 0.82 0.84 0.83 0.95 1.00 0.16 0.98 0.96 0.30 0.67 0.48 QPC2 F. fusiformis 0.96 0.84 -0.06 -0.01 -0.02 -0.02 -0.01 0.92 0.89 -0.01 0.48 0.47 -0.02 -0.02 -0.01 0.96 0.18 -0.02 0.83 -0.05 -0.02 QPC3 M. arenacea 0.24 0.27 0.21 0.08 0.37 0.59 0,12 0.24 0.05 0.07 0.22 -0.01 0.56 0.31 -0.02 0.08 -0.01 0.26 0.40 0.71 0.88
R-mode faunas RPCl F.jusiformis 1.42 -0.40 -0.57 -0.75 -0.61 -0.53 -0.68 -0.38 -0.11 -0.78 -0.45 -0.45 -0.59 -0.60 -0.83 0.00 -0.71 -0.63 -0.29 -0.68 -0.41 RPC2 B. aculeata 0.40 1.10 8.54 -0.44 -0.36 -0.31 -0.39 -0.24 0.21 -0.46 -0.29 -0.33 -0.36 -0.34 -0.49 -0.45 -0.43 -0.36 0.72 0.67 -0.24 APPENDIX G
Core depth (mbsf) 8.07 8.12 8.17 8.27 8.32 8.37 8.47 8.57 8.62 8.72 8.77 8.82 8.87 8.92 8.97 9.02 9.07 9.32 9.37 9.43
Counts (#/cc) i4. ccholsi - - - ” 1.3 3.0 ------0.3 - - - - - B. aculeata 0.3 0.3 0.3 - 0.7 - B. pseudopunctata - - 0.7 - 0.3 2.3 1.0 - - - - - 0.7 - 3.7 - - - 0.3 C. lobatulus 0.3 - E. exigua - - - - 0.7 1.7 0 . 7 ...... 0.3 - 0.3 F. fusiformis - 0.7 - 2.3 14.7 3.3 5.0 0.7 3.3 G. biora 0.7 4.3 6.3 0.7 7.0 0.3 - 0.3 - G. crassa rossensis M. arenacea 1.7 1.3 3.7 2.3 1.0 0.7 2.0 3.7 0.3 0.3 1.7 0.7 1.0 1.0 1.7 1.0 0.3 1.0 1.0 ^ iV. bradti ------0.3 - - 0.3 - - - - - 5 N. iridea - 0.3 - 0.3 9.7 - 2.0 - - - - 1.0 2.3 - 2.0 - - - 1.0 iV. pachyderma - 0.3 ------0.7 ------7, angulosa - - - - - 6.0 ------T. intermedia 5.3 5.3 3.7 1.7 2.7 2.0 1.7 0.7 4.0 4.3 2.3 3.7 4.3 3.3 3.0 4.0 3.0 1.0 2.0 5.7
Diversity (#species) 25347862222654842662 BFAR(#/cm2ky-l) 2100 2400 2400 2000 9100 5900 3700 1300 1300 1400 1200 3200 4400 1600 5500 1700 1000 1200 2400 1800
Q-mode faunas Q?Cl T. intermedia 0.98 0.98 0.74 0.44 0.04 0.07 0.19 0.20 1.00 1.00 0.85 0.62 0.51 0.97 0.28 0.98 1.00 0.58 0.44 0.99 Q K 2 F fusiformis -0.01 0.11 -0.03 0.66 0.90 0.27 0.92 -0.02 -0.01 -0.01 -0.02 -0.08 -0.06 -0.04 -0.10 -0.03 -0.01 0.33 0.88 -0.01 QPC3M. arenacea 0.21 0.13 0.66 0.60 -0.07 -0.11 0.24 0.98 -0.02 -0.02 0.52 -0.06 -0.05 0.17 0.03 0.14 0.01 0.54 0.13 -0.10
R-mcxle faunas RPCl -0.86 -0.77 -0.60 -0.36 0.75 -0.09 -0.01 -0.29 -0.80 -0.83 -0.56 0.13 0.26 -0.70 0.44 -0.81 -0.70 -0.50 -0.37 -0.91 KPC2B. aculeata -0.54 -0.21 -0.27 -0.29 -0.41 0.92 -0.26 -0.17 -0.47 -0.49 -0.33 0.08 -0.64 0.05 0.50 0.01 -0.40 0.65 -0.34 -0.64 APPENDIX G
9.53 9.58 9.63 9.68 9.73 9.78 9.83 9.93 9.97 10.03 10.13 10.18 10.23 10.28 10.33 10.43 10.48 10.58 10.71 10.76
Counts (#/cc) A. echolsi ... 2.0 0.3 0,7 B. aculeata -- - 0.3 ------0.3 -- B. pseudopunctata - 1.7 - - 2.0 17.3 1.3 - 0.7 --- 0.3 -- 1.0 0.7 8.3 1.0 - C, lobatulus ------0.7 ------0.3 - E. exigua ---- 1.0 - 4.0 1.3 0.7 0.3 --- 0.3 -- 0.3 - 0.3 1.7 F. fusiformis 8.7 5.0 -- 1.7 8.7 7.0 57.3 14.0 - - 0.3 0.7 2.3 - 7.7 2.7 17.3 10.3 2.0 G. biora -- 0.7 - 1.0 2.3 - 7.0 0.7 ------G. crassa rossensis ------0.3-- 1.3 --- M. arenacea 2.7 0.3 2.0 4.7 0.7 0.7 0.7 2.0 2.3 0.3 2.0 2.3 1.3 0.7 1.7 0.7 1.7 2.3 1.0 1.0 N. bradii - 0.3 - - - 0.3 1.3 - 1.3 ------4.0 0.3 -- 00 N. iridea 0.7 0.3 -- 1.0 1.7 2.7 14.0 1.3 -- - 0.3 2.3 - 2.7 2.3 1.0 -- N. pachyderma ------0.7 - -- T, angulosa T. intermedia 5.0 2.0 3.3 4.3 0.7 1.0 1.0 2.7 1.7 4.0 4.3 1.0 4.0 1.7 2.3 4.0 2.7 2.3 --
Diversity (#species) 4 6 3 3 8 7 7 6 10 3 2 3 5 6 2 5 9 8 5 3 5100 2900 1800 2800 3000 9600 5400 25300 7100 1400 1900 1100 2000 2300 1200 4800 4900 9800 3900 1400
Q-mode faunas 0.44 0.27 0.89 0.72 0.00 -0.07 -0.04 -0.06 0.01 0.99 0.94 0.42 0.96 0.38 0.85 0.37 0.36 0.01 -0.09 -0.12 0.87 0.92 -0.03 -0.03 0.43 0.42 0.87 0.99 0.99 -0.02 -0.02 0.11 0.15 0.72 -0.02 0.91 0.44 0.91 0.97 0.70 0.17 -0.05 0.43 0.69 0.00 -0.06 -0.07 -0.06 0.07 -0.02 0.34 0.90 0.21 0.02 0.52 -0.05 0.09 0.03 0.04 0.30
R-mode faunas RPCl F. fusifonnis -0.44 -0.36 -0.55 -0.70 0.01 0.15 1.16 3.67 0.61 -0.72 -0.74 -0.38 -0.70 -0.28 -0.56 -0.33 0.41 -0.01 0.04 0.10 RPC2 B. aculeata -0.54 -0.07 -0.41 0.07 0.26 2.44 -0.61 -1.29 -0.33 -0.52 -0.46 -0.22 -0.40 0.24 -0.33 -0.38 3.06 1.57 -0.15 -0.42 APPENDIX G
Core depth (mbsf) 10,81 11,01 11,16 11,21 11,26 11,36 11,41 11,46
Counts (#/cc) A. echolsi ------0.7 B. aculeata - 0,3 - 0,7 B. pseudopunctata - 0,3 - - - 1,0 - - 0,7 0,3 ------2,0 C. lobatulus 0,3 ------0,3 ------0,3 E. exigua 1,3 1,0 -- 3,0 --- F. fusiformis 16,0 22,7 - 15,7 9,3 2,3 21,0 1,3 0,7 5,0 8,0 1,0 - - - 68,0 68,0 37,3 24,0 2,7 G. biora - 6,0 0,3 - 4,0 0,7 2,7 0,7 4,0 0,7 G. crassa rossensis 0,3 ------0,3 ------M. arenacea 0,7 0,3 4,7 2,3 0,7 1,0 3,7 1.3 4,0 1,0 2,3 2,0 5,7 1,7 1,3 7,7 7,7 0,7 1.0 0,7 N. bradii 0,7 - - 1,0 - 0,3 0,3 1.0 0,7 0,3 1,0 - 12,7 0,7 1,3 0,7 2,0
% N, iridea 2,3 - 0,7 0,3 2,3 0,7 3,3 4,7 1,7 2,7 1,7 - - - 12,7 14,0 16,0 3,0 N. pachyderma ------0,3 ------0,7 0,3 1,7 T, angulosa T. intermedia 0,3 -- 1,0 - - 0,3 - 1,0 1,7 2,7 3,0 4,0 2,0 0,3 1,0 1,3 1,0 7,7
Diversity (#species) 8 6 3 6 5 6 6 4 BFAR (#/cm2ky-l) 6600 9200 1700 6300 5800 1800 8700 2500
Q-mode faunas QPCl T. intermedia -0,08 -0,10 0,01 -0,02 -0,14 -0,14 -0,07 -0,10 QPC2 F. fusiformis 0,99 0,94 -0,01 0,98 0,88 0,87 0,99 0,34 QPC3 M, arenacea -0,04 -0,06 0,98 0,08 -0,07 0,26 0,10 0,14
k-modc faunas RPCl F, fusiformis 0,67 1,30 -0,07 0,16 1,37 -0,08 0,82 0,28 RPC2 B. aculeata 0,12 -0,11 -0,13 0,70 -0,82 -0,05 0,05 -0.23 APPENDIX G
Core depth (mbsf) 12.32 12.37 12.42 12.47 12.52 12.57 12.62 12.67 12.72 12.77 12.92 12.97 13.02 13.07 13.12 13.27 13.57 13.62
Counts (#/cc) A. echolsi ----- 0.3 -- 0.3 - 0,3 ------B. aculeata 1.0 ------0.3 B. pseudopunctata 2.7 1.3 ---- 2.7 1.7 2.0 - 1.0 0.3 -- 2.0 1.0 -- C, lobatulus ------0.3 - 0.3 E. exigua - 3.0 - 0.7 ------1.0 . 2.3 . 0.7 .•. F. fusiforrms 16.7 7.3 30.3 29.3 1.0 1.7 28.3 2.0 1.0 1.3 4.0 14.7 4.0 2.0 4.0 11.0 20.7 1.3 G. biora ------2.7 -- 1.0 4.0 2.7 0.3 G. crassa rossensis M, arenacea 3.0 1.3 0.3 - 0.3 1.3 0.7 4.0 1.7 - 0.3 - - - 2.0 0.3 0.7 1.0 2.0 w N. bradii 0.7 0.3 1.0 1.0 - 1.0 1.7 - 0.3 - 0.3 1.0 - - 4.0 - - - o N. iridea 0.3 1.3 6.0 14.7 0.30.3 -- 14.714.7 ------10.7 ---- 29.0 - 5.3 - N, pachydertna ------0.3 - -- 1.3 0.3 ------T angulosa ------0.3 ---- 0.3 --- T intermedia 2.3 5.3 1.0 1.3 1.7 5.3 1.7 1.3 4.0 1.7 1.7 2.3 0.3 - - - 2.7 1.3
Diversity (#species) 7 7 5 5 4 5 7 5 6 3 5 6 2 2 8 5 5 4 BFAR (#/cm2ky-l) 8000 6000 11600 14100 1000 2900 15000 2800 2800 1000 2200 7000 1300 1200 12400 5100 9700 1500
Q-mode faunas QPCl T, intermedia 0.04 0.50 -0.06 -0.07 0.84 0.94 -0.06 0.25 0.85 0.74 0.29 0.05 0.00 -0.04 -0.10 -0.11 0.03 0.50 QPC2 F. fusiformis 0.97 0.81 0.99 0.95 0.53 0.26 0.95 0.40 0.18 0.61 0.91 0.95 0.98 0.70 0.21 0.91 0.99 0.48 QPC3 M. arenacea 0.10 0.00 -0.07 -0.11 0.04 0.11 -0.09 0.82 0.24 -0.13 -0.11 -0.10 -0.06 0.70 -0.13 -0.03 -0.05 0.70
R-mode faunas RPCl F. fusiformis -0.10 0.22 1.16 1.92 -0.50 -0.63 1.91 -0.29 -0.65 -0.53 -0.33 0.94 -0.32 -0.24 3.13 0.43 0.83 -0.35 RPC2 B. aculeata 1.53 -0.78 -0.47 -0.74 -0.32 -0.45 0.14 0.01 -0.05 -0.36 0.18 -0.75 -0.24 -0.17 -0.35 0.27 -0.65 -0.27 LIST OF REFERENCES
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