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1997 Late Quaternary Foraminifera From Lower Bathyal and Abyssal Sediments, Gulf of Mexico: A Record of Paleoceanographic Change. Megan H. Jones Louisiana State University and Agricultural & Mechanical College
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Recommended Citation Jones, Megan H., "Late Quaternary Foraminifera From Lower Bathyal and Abyssal Sediments, Gulf of Mexico: A Record of Paleoceanographic Change." (1997). LSU Historical Dissertations and Theses. 6426. https://digitalcommons.lsu.edu/gradschool_disstheses/6426
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LATE QUATERNARY FORAMINIFERA FROM LOWER BATHYAL AND ABYSSAL SEDIMENTS, GULF OF MEXICO: A RECORD OF PALEOCEANOGRAPHIC CHANGE
A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Geology & Geophysics
by Megan H. Jones B.S., Florida Institute of Technology, 1983 M.S., Old Dominion University, 1990 May 1997
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 9736021
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION
I dedicate this work to my ever-growing family,
Matt and Joan, Kelly, Katy, Ron, Eddie and Zoe, and Jim and Sally,
without whom I would not have had the strength or the courage to embark on such a
task. Their love and belief in me were a lifeline for me
through whatever storms came my way and when the storms were over,
they were always there waiting,
smiling in the sunshine, still loving me.
I also dedicate this work to Chris,
a long lost part of me,
who has never ceased being on my mind and in my heart.
May we catch up soon!
ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS
I would like to express my sincerest appreciation to Dr. Barun Sen Gupta, my
mentor and friend, for his constant support and guidance on this project. His candor
and ceaseless availability were instrumental in the completion of my dissertation. My
committee was invaluable to me in many ways, the most important of which was
modeling for me professionalism, integrity, and excellence in scientific research in their
own careers. Dr. James Geaghan was always available to share his statistical and
biological expertise with me. Dr. Jeffrey Hanor provided guidance on the geochemical
aspects of this project and on the critical illustrations, but probably most important were
the much needed limits he set for the completion of this project. Dr. Lui-Heung Chan's
boundless enthusiam for her own work in chemical oceanography was contagious and
propelled me in directions I had no idea that I was interested in going. Dr. Joseph
Hazel's love for stratigraphy and the subtleties of geology were a constant source of
enlightenment. Dr. Stuart Scott, my outside committee member who surfed the net in
search of foraminifera, was an inspiration in his effort to glean insight into my
dissertation. Thank you all!
Many thanks go to Dr. Bill Behrens, Dr. Dick Buffler, Dr. Tony Gary and Dr. Paul
Loubere who graciously allowed my participation in the University of Texas at Austin
cruise leg 89-G-10 from which this project evolved. Additional thanks go to Dr.
Behrens for making available to me core material from other cruises as well as his
chemical data from these cruises. He essentially opened-wide the door to his archives
and let me roam around. Financial support for this work came from several sources:
the Department of Geology and Geophysics here at LSU, research grants from British
Petroleum, Mobil Oil, and the Gulf Coast Association of Geological Societies, and a
iii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. partial fellowship from Shell Oil. I would like to thank Dr. Victor Rivera, Dr. Robert
Twilley, and John Foret from the Department of Biology at the University of
Southwestern Louisiana for providing organic carbon analyses, and Dr. Gary Byerly
(LSU) for microprobe analysis of the ash layer in core IG-45-15. The SEM
photographs were graciously taken by Emil Platon (and this really is the last time I will
thank you). I wish to thank Mary Lee Eggart for bringing to life many of the figures in
this dissertation and for always having a calming and an objective perspective when I
was fumbling with figures. Photography here at LSU was made effortless by Kerry
Lyle and Felicia. Sara Marchiafava, in her quiet, efficient way, made the logistics of
any task I undertook here flow smoothly. I would loath to be here without her!
I want thank to Pam Borne, Jonathan Franzosa, Cathy Johnson, Missy Powell,
and Diane Weiland for willingly helping me with many phases of this project at times
when I was despairing. This work benefitted greatly from numerous stimulating
discussions with Tom Buerkert, and from critical reviews by Maud Walsh and Wylie
Poag. I am eternally grateful to Liz McDade for the roof (if you can call it that) over my
head during this last year. Should every ABD be so lucky! Were it not for several new
friends who openly shared their experience, strength and hope (timeless words of
wisdom) with me and gently nudged me in a renewed life direction, I would still be
floundering. Thank you Barbara, Diane, Dick, Grace, Janice, Jodi, Lance, Louise,
Martha, Stuart, Tonia, Viki, and those that came before us.
My most special thanks go to the following women who kept me steady throughout
this endeavor over the last millenium: Laurie Anderson, my cherished friend and
colleague, for her ceaseless support in ways too numerous to list, but she knows;
Missy Powell, my roommate and cherished friend, who always asked the pointed
questions at just the right moment; Jayne Salvo, my cherished friend and fellow
waitress, for modeling for me wit, charm, determination, flirtatiousness, and
iv
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. spontaneity, all which enabled me to crawl out of my shell over the last 20 years; Poree
Sen Gupta, my voice of timeless wisdom, for her warmth, willingness to listen, and for
the fabulous Indian food that usually followed; and Maud Walsh, my twin and
cherished friend, for providing me with a family and an objective eye whenever I
needed them.
Numerous others have shared their expertise with me, have given of their time,
have fed and tea'd me, and/or simply have dried my tears as I have trodden this path. I
wish to thank all of you who joined me for this leg of the Journey; I was truly blessed:
Paul Aharon, Gile Beye, Vila Binford, Grace Blereau, Susan Bradshaw, Peggy
Broussard, Cathy Castille, Steve Culver, Jim Galluzzo, Glenn Garson, H.P., Stacy
Henry, Paul Henrich, Stacey Hochstadter, Oscar Huh, Cathy Johnson, Steve Jones,
Kirt Kempter, John Kruger, Dinah and Rich Launch, Chris Livesey, Chad McCabe,
Liz McDade, Pete McLaughlin, Kathy McManus, Nargis, Janice Oliver, PJ Perry, Katy
Powell, Ellen Prager, Bob Remy, Harry Roberts, Jim Roche, John Rybcyzk, Judith
Scheibout, Julia Sanky, Stuart Stewart, Su Yin Ting, Bill W., Nan Walker, Lynn
Wiggins, Stan and Lynda Williams, and Judy Young.
with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS
DEDICATION...... ii
ACKNOWLEDGMENTS ...... iii
LIST OF TABLES...... viii
LIST OF FIGURES...... ix
LIST OF PLATES...... xv
ABSTRACT...... xvi
CHAPTER 1 INTRODUCTION...... I Significance ...... 1 Goal and Objectives ...... 2 Oceanography ...... 3 Methods and Materials ...... 8
2 LITHOSTRATIGRAPHIC RECORD...... 14 Ash Layer Geochemistry ...... 14 Sediment Accumulation Rates ...... 17 Organic Carbon (Cop,) ...... 22 Calcium Carbonafe ...... 31 Discussion and Summary ...... 36
3 PLANKTIC FORAMINIFERAL RECORD...... 41 Planktic Foraminifera in Surface Sediments ...... 41 Downcore Planktic Foraminiferal Record ...... 43 Biostrati graphic Framework ...... 57 Late Quaternary Planktic Foraminiferal Variations ...... 64 Discussion and Summary ...... 85
4 BENTHIC FORAMINIFERAL RECORD...... 97 Distribution of Recent Benthic Foraminifera ...... 99 Downcore Distributions of Benthic Foraminifera ...... 137 Discussion and Summary ...... 160
5 SYNTHESIS...... 177 The Late Quaternary Record of Paleoceanographic and Paleo- climatic Change in the Northwestern Gulf of Mexico 177 Paleoceanographic Model for Abyssal Gulf of Mexico 185 D iscussion ...... 190 Conclusions ...... 192
REFERENCES...... 195
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 1 Planktic foraminiferal percentage data for core-top study ...... 209
2 Planktic foraminiferal percentage data for downcore study ...... 213
3 Benthic foraminiferal percentage data for core-top study ...... 237
4 Benthic foraminiferal percentage data for downcore study ...... 253
VITA...... 278
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES
1. Station Numbers, Locations, and Water Depths (m) for all Core Material. Map numbers used only for samples of the core-top Study (see Fig. 3) ..... 9
2. Ash Bed Geochemistry: Major Element Composition (%)...... 16
3. Sediment Accumulation Rates (cm/kyr) ...... 19
4. Downcore Corg (%)...... 27
5. Downcore Calcium Carbonate (%)...... 33
6. Taxonomic List of Planktic Foraminifera ...... 44
7. Biostratigraphic Zonation Summary ...... 46
8 . Factor Scores for Species of Planktic Foraminifera. Scores in bold considered significant for interpretation of factors ...... 80
9. Taxonomic List of Benthic Foraminifera ...... 100
10. Species Diversity Measures for each Core-Top Sample: S, number of species per sample, H(S), Shannon-Wiener Information Function, and E, species equitability ...... I ll
11. Rotated Factor Pattern (loadings) from R-mode Factor Analysis. Boxed loadings considered significant (> 0.7) for interpretation of factor assemblages ...... 117
12. Factor Scores from R-mode Factor Analysis ...... 119
13. Downcore Species Diversity Measures for Lower Bathyal and Abyssal Stations: S, number of species per sample, H(S), Shannon-Wiener Information Function, and E, species equitability ...... 139
14. Summary Table of Carbonate Dissolution Events. Numbers in bold indicate one dissolution event at the lower boundary of the zone; na indicates zone not present ...... 181
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES
1. Map showing station locations for downcore planktic foraminiferal study.... 4
2. Hydrographic data for station 89-G-10-PC4 showing negiible variation in temperature (°C), salinity (%o), and dissolved oxygen (ml/L) throughout Gulf Basin Water (GBW) ...... 5
3. Map showing station locations for core-top benthic foraminiferal study 10
4. Distribution of Gulf of Mexico sediments showing that study area (outline) lies within three sedimentary regimes: Rio Grande, Central Texas, and Mississippi Regimes. After Poag (1981) ...... 15
5. Map with station locations showing sediment accumulation rates in the Holocene (bold) and the Pleistocene subzone, Y 1 (italics at these sites; na indicates no data) ...... 18
6 . Distribution of percent organic carbon (COTS) in surface sediments of northwestern Gulf of Mexico “ ...... 23
7. Distribution of carbon/nitrogen ratios (C/N) in surface sediments of northwestern Gulf of Mexico ...... 24
8 . Sl3C of sedimentary Corg in surface sediments showing geographic distribution of organic matter type ...... 26
9. Downcore plots of percent Coro for five stations showing notable COTg increase within Y 1 meTtwater interval ...... 29
10. Downcore plots of 6 13C of sedimentary Corg for two stations showing increase in terrestrial Corg in glacial (Y) interval ...... 30
11. Variations of percent calcium carbonate in surface sediments showing basinward increase ...... 32
12. Downcore plots of percent calcium carbonate for six stations showing higher carlxmate content in interglacial (X and Z) intervals ...... 35
13. Map of planktic foraminiferal provinces in the North Atlantic Ocean 42
14. Downcore plots of percent relative frequencies of six planktic foraminifera species used for biostratigraphic zonation of station BPX-10; * indicates a dissolution event ...... 48
15. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-45-15; * indicates a dissolution event ...... 49
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16. Downcore plots of percent relative frequencies of six planktic foraminifera species used for biostratigraphic zonation of station BPX- 1; * indicates a dissolution event ...... 50
17. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-41-21; * indicates a dissolution event ...... 51
18. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-41-26; * indicates a dissolution event ...... 52
19. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC1; * indicates a dissolution event ...... 53
20. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC4; * indicates a dissolution event ...... 54
21. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC2; * indicates a dissolution event ...... 55
22. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globigerinoides ruber, percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Note the largest relative frequency peak in the meltwater interval, subzone Y 1. Water depth for each station is shown in lower left comer of plot ...... 68
23. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Neogloboquadrinadutertrei: percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Note the largest frequency peak in the early Holocene, subzone Z2. Water depth for each station is shown in lower right comer of plot ...... 69
24. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Gbbigerinioides sacculifer percentages (solid curve and bottom scale) and number of foraminifera/ g sediment (dashed curve and top scale), respectively. Water depth for each station is shown in lower right corner of plot ...... 71
25. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globorotaliatruncatulinoides percentages (solid curve and bottom scale) and number of foraminifera/ g sediment (dashed curve and top scale), respectively. Water depth for each station is shown in lower right corner of plot ...... 72
26. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Hasterigerina aequilaterialis : percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. bottom scale), respectively. Water depth for each station is shown in lower right corner of plot ...... 73
27. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globigerina falconensis percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Water depth for each station is shown in lower right corner of plot ...... 75
28. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globorotaliainflata percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Water depth for each station is shown in lower right comer of plo t ...... 76
29. Downcore absolute frequency plots of total planktic foraminifera minus G. ruber and of G. ruber (number of foraminifera/ g sediment; solid curve and dashed curve, respectively) showing larger frequencies of G. ruber than total planktics in Y1 meltwater interval ...... 78
30. Downcore plots of absolute frequency of total planktic foraminifera (number of foraminifera/ g sediment) showing increase beginning latest Pleistocene with highest absolute frequencies occurring in Holocene Z zones ...... 79
31. Downcore plots of Factor 1 loadings with more positive loadings, reflecting influence of increased productivity assemblage, in glacial Y zones ...... 82
32. Downcore plots of Factor 2 loadings with more negative loadings, reflecting influence of cool-water assemblage, inglacial Y zones ...... 83
33. Downcore plots of Factor 3 loadings with more negative loadings, reflecting influence of stenotopic assemblage, in glacial Y zones ...... 84
34. Map with station locations showing the relative frequency increases of Globigerinoidesruber (bold) and Neogloboquadrinadutertrei (italic) within the meltwater interval (Yl); na indicates no data ...... 86
35. Plots of species diversity measures against water depth, showing persistently high species diversity, but no discernible trend with water depth, S, is number of species (open diamonds), H(S) is the Shannon-Wienner Information Function (closed circles) and E is a measure of species equitability (open circles) ...... 109
36. Percentage plots of Nuttallidesdecorata and Buliminaaculeata against water depth, showing their highest relative abundances at depths less than 2000 m...... 112
37. Percentage plots of Alabaminellaturgida and Bolvini lowmani against water depth, showing their persistently high relative abundances at all depths 112
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38. Percentage plots of three minor species against water depth, showing their eurybathic nature ...... 114
39. Percentage plots for eight species against water depth, showing a trend of increasing relative abundance with increasing depth. All of these species attain their highest abundances at water depths greater than 2700 m ...... 114
40. Percentage plots of five species against water depth, showing highest abundances between 2000-2400 m ...... 115
41. Plot of the number of foraminifera (per gram of sediment) against water depth, showing a decrease in absolute abundance of total foraminifera with increasing water depth ...... 115
42. Plots of the number of individuals (per gram of sediment) of selected species against water depth, showing an overall trend of decreasing absolute abundance with increasing water depth ...... 116
43. Map showing geographic distribution of strong (labeled stations) Factor 1 scores (> 0.7) ...... 120
44. Map showing geographic distribution of strong (labeled stations) Factor 2 scores (> 0.7) ...... 120
45. Map showing geographic distribution of strong (labeled stations) Factor 3 scores (> 0.7) ...... 121
46. Map showing geographic distribution of strong (labeled stations) Factor 4 scores (> 0.7) ...... 121
47. Map showing geographic distribution of strong (labeled stations) Factor 5 scores (> 0.7) ...... 122
48. Map showing geographic distribution of strong (labeled stations) Factor 6 scores (> 0.7) ...... 122
49. Plot of Corg against percentage of Nuttallidesdecorata, showing a trend of increasing relative abundance of N. decorata with decreasing COTg...... 125
50. Dendrogram from Q-mode cluster analysis of core-top samples showing a depth separation of samples and six sample groupings within lower bathyal and abyssal depth zones ...... 132
51. Map showing distribution of six lower bathyal and abyssal biofacies identified by Q-mode cluster analysis. Assemblages that characterize these biofacies were indentified by R-mode factor analysis ...... 133
52. Downcore plots of species diversity measures for lower bathyal stations showing generally high species diversity with little temporal variation 140
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53. Downcore plots of species diversity measures for abyssal stations showing generally high species diversity with conspicuous fluctuations during the early to late Holocene ...... 141
54. Percentage plots of benthic foraminiferal species characteristic of lower bathyal stations and rare to absent in abyssal stations against core depth (cm ) ...... 142
55. Percentage plots of benthic foraminiferal species characteristic of abyssal stations and associated with NAIW against core depth (cm) ...... 143
56. Percentage plots of several agglutinated foraminiferal species against core depth (cm) generally with Glomospiracharoides, Karrerulina apicularis and SpiroplecieUa cylindroides showing their highest abundances in the upper portions of all cores, and Siphotextularia qffinis and Sigmoilopsis schlumbergeri showing their highest abundances in the abyssal and lower bathyal cores, respectively ...... 144
57. Percentage plots of three watermass associated benthic foraminifera, the Oridorsalistener species group (NAIW), Cibicides wueUerstorfi (NADW) and Gryoidinoides polius (CMW/NADW) against core depth (cm) 146
58. Percentage plots of Alabaminella turgidus, Bolivini lowmani, Nuttallides decorata, and Cassidulina subglobosa against core depth (cm) ...... 147
59. Percentage plots of Quinqueloculinavenusta, Q. seminula, and Q. spp. against core depth (cm) showing highest abundances in glacial intervals.... 148
60. Percentage plots of Biloculinellairregularis and Hoeglundina elegans against core depth (cm) showing highest abundances in glacial and interglacial intervals, respectively ...... 149
61. Percentage plots of Gbbobuliminaaffinis, Osangulariaculter, and Cibicidesbradyi against core depth (cm) ...... 150
62. Percentage plots of Melonispompilioides and Epistominella exigua against core depth (cm) ...... 151
63. Dendrograms from Q-mode cluster analyses of lower bathyal downcore samples showing glacial-interglacial separation: a) all samples from BPX-1 and BPX-10 using 21 species at > 1% in 10 or more samples; b) samples from BPX-10 only using 7 species at > 1% in 9 or more samples; c) samples from BPX-10 only using 8 species at > 2% in 7 or more samples; d) samples from BPX-1 only using 10 species at > 1% in 9 or more samples; e) samples from BPX-1 only using 12 species at > 2% in 5 or more samples; 0 all samples from BPX-1 and BPX-10 using 19 species at > 2% in 6 or more samples ...... 154
64. Dendrograms from Q-mode cluster analyses of abyssal downcore samples showing glacial-interglacial and within-depth zone separation: a) all samples from PC-1 and PC-2 using 31 species at > 1% in 2 or more samples; b) all samples from PC-1 and PC-2 using 21 species at > 2% in 2 or more samples; c) samples from PC-1 only using 15 species at > 2% in 2
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. or more samples; d) samples from PC-2 only using 14 species at >2 % in 3 or more samples; e) samples from PC-1 only using 17 species at > 1% in 5 or more samples; f) samples from PC-2 only using 16 species at > 1% in 5 or more samples ...... 155
65. Dendrogram from Q-mode cluster analysis of all lower bathyal and abyssal downcore samples using 37 species at > 2% in 2 or more samples, showing between-depth zone separation, a within-depth zone separation and a within-core glacial-interglacial separation ...... 158
66. Cross-sections showing the stratigraphic distribution of sample clusters.... 159
67. Map showing the distribution of generic benthic foraminiferal provinces modified from Poag (1981) ...... 166
68 . Gulf of Mexico basin at the last glacial maximum (LGM): a) map showing study area (black outline) and the LGM shoreline and b) map showing late Pleistocene shelf-edge deltas modified from Suter and Berryhill (1985) ..... 178
69. Summary diagram graphically depicting changes in the proxies for oceanographic parameters (Y-axis) through time (X-axis) ...... 186
70. Summary diagram of the paleoceanographic model for abyssal Gulf of Mexico surface- and deep-waters graphically depicting changes in oceanographic parameters (Y-axis) through time (X-axis) ...... 187
71. Summary chart outlining late Quaternary variations in oceanographic proxies used to develop the paleoceanographic model for abyssal Gulf of Mexico surface- and deep-waters ...... 188
72. Cross-sections showing Atlantic water mass configuration: a) at the present and b) during the last glacial interval, modified from Haddad and Droxler (1996) ...... 191
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF PLATES
1. Planktic Foraminifera. 1,2) Globorotalia crassaformis 150/*, 180/*; 3) Neogloboquadrina sp. cf. N.pachyderma 250/*; 4 ) G. inflata 190/*; 5, 6) G. truncatulinoides 150/*, 150/*; 7, 8 ) Neogloboquadrina dutertrei 180/*, 190/*; 9) Globorotalia menardii 70/*; 10, 11) Gbbigerina falconensis 250/*, 270/*; 12, 13) Globigerinoides ruber 200/*, 170/*; 14, 15) G. sacculifer 110/*, 140/*; 16, 17) Hasterigerina aequilateralis 170/*, 200/*. All scale bars equal 100/* ......
2. Benthic Foraminifera. 1,2) Eggerella bradyi 300/*, 250/*; 3) £. bradyi with possible nematode borings 350/*; 4, 5) Siphotextularia ajfinis 400/*, 270/*; 6,7) Quinqueloculina venusta 170/*, 230/*; 8 ) Pyrgo murrhina 130/*; 9) Sigmoilopsis schlionbergeri 120/*; 10, 11) Hoeglundina elegans (10 with borings) 110/*, 170/*; 12) Bolivina lowmani 500/*; 13, 14) Cassidulina subglobosa 120/*, 600/*; 15) Stainforthia complanata 270/*; 16) Bulimina alazanensis 270/*; 17, 18) fi. aculeata 200/*, 270/*; 19) Uvigerina auberiana 370/*; 20, 21) U. peregrina 370/*, 170/*; 22, 23) U. hispidocostata 100/*, 220/*; 24, 25) Bulimina mexicana 150/*, 230/*. All scale bars equal 100/* ......
3. Benthic Foraminifera. 1,2) Alabaminella turgida 600/*, 700/*; 3, 4) loanella tumidula 550/*, 650/*; 5, 6) Cibicides wuellerstorfi 130/*, 160/*; 7 , 8 ) C. 6ra*/yz 250/*, 300/*; 9, 10, 11) Nuttallides decorata 550/*, 550/*, 500/*; 12, 13) Melonis pompilioides 180/*, 200/*; 14) Pullenia bulloides 500/*; 15, 16, 17) Oridorsalis tener 370/*, 220/*, 370/*; 18, 19) O.umbonatus 180/*, 220/*; 20) O. sp. A 850/*; 21, 22) Gyroidinoides polius 450/*, 430/*; 23, 24) Biloculinella irregularis 350/*, 370/*. All scale bars equal 100/* ......
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT
Striking late Quaternary surface- and deep-water oceanographic changes and a link
to North Atlantic thermohaline circulation are identified by analyses of high-resolution,
benthic and planktic foraminiferal census data from the lower bathyal and abyssal Gulf
of Mexico (GOM). The recognized environmental, watermass, preservation, and
productivity signals reveal a detailed paleoenvironmental and paleoceanographic history.
A paleoceanographic model developed for surface and deep waters of the abyssal Gulf
describes a four-stage sequence of oceanographic changes from the Last Glacial
Maximum (LGM) to the present.
Compared to present-day surface waters, those of LGM were nutrient-enriched and
had reduced productivity. The influx of glacial meltwater into the Gulf, identified by-
increases in Globigerinoides ruber and Neogloboquadrina dutertrei, caused a reduction
in salinity and an increase in nutrients (leading to higher surface-water productivity),
and possibly initiated a period of surface- and bottom-water instability that continued
into the middle or late Holocene. Planktic foraminifera do not indicate that GOM
surface waters cooled to full-glacial conditions during the Younger Dryas interval.
Compositional changes in Gulf Basin Water (GBW) from LGM to the present, with
a period of bottom-water instability in between, reflect changing source areas for
intermediate- and deep-water formation in the Atlantic. Glacial North Atlantic
Intermediate Water (GNAIW), indicated by high relative abundances of the Oridorsalis
tetter species group, Ioanella tumidula, and Eggerella bradyi, strongly influenced
glacial GBW during LGM and most of the Meltwater/Younger Dryas intervals. From
the late Holocene to the present, a stronger influence of upper North Atlantic Deep
Water (UNADW), indicated by high relative abundances of Cibicides wuellerstorfi, is
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. evident. Between these two intervals, the influence of both GNAIW and UNADW is
present, probably reflecting bottom-water reorganization. Relative abundances of
several dissolution-prone benthic species (e.g. BilocuUnella irregularis, Hoeglundim
elegans ), and of various dissolution-prone and dissolution-resistant planktic species
indicate diminished bottom-water corrosivity during glacial intervals, again reflecting a
significant change in GBW.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1 INTRODUCTION
"A foraminiferal organism may be considered to carry a paleobiological message within its shell that awaits decoding by the micropaleontologist, ecologist, cytologist, geochemist, and biochemist."
Allan W. H. Be (1977)
In recent years, the use of benthic foraminifera as paleoceanographic indicators has
led to fierce debate (e.g. Boyle, 1990; Schinitker, 1994). Many advances in marine
geochemistry have revolutionized the field of paleoceanography, and chemical signals
(especially in foraminiferal shells) have been presented as the only reliable indicator of
past bottom-water change (Boyle, 1990). This view, however, does not take into
account the nature of foraminiferal distribution data. Indeed, with few exceptions, the
complex nature of foraminiferal interrelationships as well as their relationship to the
environment precludes the use of simple presence/absence data in paleoceanography.
However, with careful collection of quantitative data and robust numerical techniques,
foraminiferal distributions can provide great insight into oceanographic changes that are
not often elucidated by straightforward geochemical analysis (e.g., Ishman et al., 1996;
Rasmussen et al., 1996a, b). This dissertation illustrates how detailed, high-resolution
foraminiferal data and their analysis can yield coherent paleoceanographic models
comparable to those developed using chemical proxies and computer modeling. Significance
There are many unanswered questions about Gulf of Mexico surface- and deep-
water paleoceanographic conditions over the last glacial-interglacial cycle. In particular,
what influences, if any, does large-scale, open-ocean circulation have on the deep Gulf,
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. or what effect does the Gulf of Mexico have on extra-basinal oceanography and climate?
Although a marginal sea, do Gulf basin renewal waters, of Caribbean origin, reflect an
Atlantic connection? That Gulf of Mexico oceanographic changes may have a large
effect on global oceanographic and atmospheric circulation patterns has been proposed
by the General Circulation Model studies of Maasch and Oglesby (1990) which
indicated that an influx of cold meltwater into the Gulf at 12 ka would reduce the
intensity of the North Atlantic storm track, enhance the monsoonal flow of moisture
over northwestern Mexico, creating increased precipitation in the west, and causing
increased trade winds across the Caribbean. Also, since the Gulf Stream is the major
conveyor of heat to the North Atlantic, inhibiting this flow would tend to pull the polar
front farther south, greatly effecting the climatic regime of that region. Goal and Objectives
The goal of this project was a comprehensive examination of lower bathyal and
abyssal benthic and planktic foraminifera through the latest Quaternary to examine
glacial-interglacial oceanographic and climatic changes in the Gulf of Mexico. The high-
resolution data set of this study provide a special opportunity to look at the relationship
between surface- and deep-water oceanographic changes, and to evaluate if the effects
of large-scale, extra-basinal oceanographic and climatic changes are evident within the
Gulf of Mexico.
The following theses are addressed in this dissertation: 1) that foraminifera can be
reliably used as indicators of paleoceanographic change, 2) that the influx of glacial
meltwater strongly affected surface-water conditions beyond simple salinity variations,
3) that shifting open-ocean deepwater circulation influences deep Gulf basin waters, 4)
that spatial variation within the lower bathyal and abyssal environments would be
reflected in benthic foraminiferal assemblages and biofacies distributions, thus allowing
refinement of these historically depth-defined, deepwater depositional environments,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3
and 5) that, although benthic foraminiferal inter-relationships are complex,
environmental, taphonomic and productivity signals can be readily isolated.
This dissertation includes three main chapters: 1) the lithostratigiaphic record of
lower bathyal and abyssal sediments which includes sections on geochemical analysis of
volcanic ash, sediment accumulation rates, and the organic carbon and calcium
carbonate records; 2) the planktic foraminiferal record which includes the
biostratigraphic framework for the study, downcore faunal variations of planktic
foraminifera, and discussions on glacial meltwater influx into the Gulf of Mexico and
the record of the Younger Dryas Event; and 3) the benthic foraminiferal record which
includes a detailed core top study documenting Recent benthic biofacies and a downcore
study to evaluate glacial/interglacial benthic foraminiferal variations. Each of these
three chapters includes an examination of surface-sediments from core-top samples or
from the literature, as well as a downcore study to look at temporal variations. A final
chapter, titled "Synthesis," integrates the lithostratigraphic, planktic and benthic records
and proposes a model for surface- and deepwater paleoceanography of the abyssal Gulf
of Mexico. Oceanography
Surface Waters (0-700 m)
Three water masses — the Surface Mixed-Layer (0-100m), Gulf Water (100-250 m),
and the Oxygen-Minimum Water (250-700 m) — comprise the upper layers of the Gulf
Basin (Nowlin, 1971; Denne and Sen Gupta, 1993). In the eastern Gulf these waters,
replenished by the Loop Current, are still characteristic of Atlantic surface-waters,
whereas those in the western Gulf have lost the salinity and dissolved-oxygen
signatures characteristic of the Atlantic water masses from which they originate because
of intense vertical mixing (Morrison, et al., 1983). Hydrographic data in the study area
from station 89-G10-PC-4 (26°03'N, 94°30'W; Figs. 1,2) reveal the temperature.
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AREA 1 AREA 2
BPX-1 0 IG-45-15 brx * * | AREA 3 i / \ A PC-1*
PC-4
100
PC-2
Figure 1. Map showing station locations for downcore planktic foraminiferal study. The star in Area 1 is the location of Orca Basin.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5
Temperature, °C Salinity, % o
0 5 10 15 20 25 30 34.5 35.5 36.5 37.5
© ♦
500-
1000-
g 1500
a £
2000 - GBW GBW
2500-
3000 2 3 4 5 6 Dissolved Oxygen, ml/L
Figure 2. Hydrographic data for station 89-G-10-PC4 showing neglible variation in temperature (°C), salinity (%o), and dissolved oxygen (ml/L) throughout Gulf Basin Water (GBW).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6
salinity and dissolved-oxygen conditions of these water masses in the central western
Gulf.
Upper-layer circulation in the west-central Gulf is dominated by warm-core
anticyclonic eddies shed from the Loop Current (Elliot, 1982; Vidal et al., 1992). These
anticyclonic, warm-core eddies are typically characterized by low nutrient levels in the
upper 100 m. However, increased productivity, relative to the eddy core, was reported
from the eddy margins as well as from cold-core, cyclonic eddies (Biggs, 1992).
Intermediate Waters (700-1500 m)
Subantarctic Intermediate Water (700-1000 m; SAIW) and Caribbean Midwater
(1000-1500 m; CMW) retain enough of their geochemical signature that they are easily
recognized. SAIW is characterized by a salinity minimum (34.88%o) and a nutrient
maximum (Morrison et al., 1983). CMW, actually an altered form of upper North
Atlantic Deep Water (UNADW), is modified as it passes through the Caribbean basins
(Denne and Sen Gupta, 1993). It decreases in dissolved oxygen, with consequent
increases in nutrient levels, from the Atlantic through the Caribbean and into the Gulf of
Mexico (Shiller, 1995).
Bottom Water (>1500 m)
Gulf Basin Water (GBW), ubiquitous below a depth of about 1500 m (Nowlin,
1971), is the deepest water mass in the Gulf. It forms at the Yucatan Straits as renewal
waters from the Caribbean Sea enter the Gulf over the 1900-m deep sill. GBW consists
of at least 50 percent Caribbean water as far as 350 km north of the Yucatan Straits
(Carder et al., 1977), but a deep counter-current flowing southward from the Atlantic
into the Gulf through the 800-m deep Florida Straits may also contribute to GBW
(Hurley and Fink, 1963; Newman and Ball, 1970; Poag, 1981, 1984). Deep outflow
of silica-enriched waters from the Gulf of Mexico into the Caribbean, at water depths
from 1250-1600 m, was proposed to account for increased silica concentrations in the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7
northwestern Yucatan Strait (Carder et al., 1977). Furthermore, oxygen concentrations
in the Yucatan Strait also suggest deep southward transport (Hansen and Molinari,
1979). Shiller (1995) postulates that this outflow is the balance for the influx of deep
Gulf renewal waters from the Caribbean.
Water properties, except for dissolved silica, show insignificant vertical or lateral
variation within GBW (Nowlin, 1971; Carder et al., 1977). At depths >1,500 m,
GBW temperature is about 4.2°C, salinity is 34.95%c, and dissolved oxygen is 4.8-5
ml/L (Nowlin, 1971; Morrison et al., 1983). Hydrographic data collected during this
study (Fig. 2) support previous observations; a temperature of 4.3°C, salinity of
34.94%c and dissolved oxygen of 4.8-5 ml/L.
Knowledge of deep-water currents in the Gulf of Mexico is preliminary, and no
simple models of regional bottom-water circulation exist, but it has been demonstrated
that the Gulf of Mexico basin is not just a quiescent marginal sea (Lewis, 1992). In the
western Gulf, upper-level circulation patterns are dominated by warm-core anticyclonic
eddies which are shed from the Loop Current (Elliot, 1982; Vidal et al., 1992). Recent
work reveals that deepwater currents exist to a depth of 3000 m, and in some cases are
related to Loop Current eddy shedding and propagation into the western Gulf
(Hamilton, 1990, 1992; Welsh, 1996). Hoffman and Worley (1986) suggest that
deepwater circulation is counterclockwise and composed of several small cells as
opposed to the large, clockwise, gyres that drive upper-layer circulation. On the
Mexican-Texan continental slope, warm-core eddies interact with bottom topography
and generate secondary cyclonic and anticyclonic eddies at depth (Lewis et al., 1989;
Welsh, 1996). Welsh (1996), in a recent modeling study of the Gulf of Mexico,
demonstrates that the deep cyclones do not become uncoupled from the upper layer
anticyclones as they migrate westward and are influenced by bottom bathymetry. She
shows that they move relative to one another with deep cyclones moving faster than the
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surface anticyclones. Another possible energy source for deepwater currents in the Gulf
of Mexico is topographic Rossby waves. These low frequency motions have been
documented in deep circulations of the northwest Atlantic continental rise (Hamilton,
1984) and recently have been recorded from parts of the eastern, central, and western
Gulf (Hamilton, 1990).
The impact of deep-water currents and the eddies shed from the Loop Current on
the biota of the deep Gulf is at present unknown. However, these anticyclonic, warm-
core eddies have low nutrient levels, whereas the cyclonic eddies have much higher
productivity (Biggs, 1992). This productivity variation suggests that a surface-ocean
productivity' gradient affecting organic carbon flux to the continental slope may exist
(Loubere et al., 1993a, b). Methods and Materials
Core material for this project (Table 1) came from two sources: The Institute for
Geophysics at the University of Texas at Austin and BP Exploration, Inc. Twenty-
seven core-top samples were obtained for the study of surface sediments (Fig. 3) and
eight piston cores for the downcore study (Fig. 2). Carbonate, Corg, and 6 ^ c data
from some of these cores was made available by Behrens (1989; pers. comm.).
Chronology used to calculate sediment accumulation rates was that of Broecker et al.
(1990) and adapted from Flower and Kennett (1990). Ages for the Pleistocene-
Holocene boundary and for the boundary between the planktic foraminiferal subzones
Y1/Y2 are 10.1 ky and 14 ky, respectively. For an estimate of sediment accumulation
for the Y zone an age of 84 ky was used. This age is based on geochemical correlation
of an ash layer in subzone Y 8 , just after the X-Y boundary, in core IG-45-15.
Organic Carbon
Analysis of total organic carbon (Corg) was performed on 13 of the core-top and 97
downcore samples to examine the effect of organic matter abundance on the
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Table 1. Station numbers, locations, and water depths (m) for all core material. Map numbers used only for samples of the core-top study (see Fig. 3).
Map # Sample No. Depth (m) Latitude °N Longitude °W
BPX-10 1543 26 54.5 92 19.0 BPX-1 1815 26 47.5 92 13.4 89-10-PC-4 3550 25 12.8 95 03.7 1 IG-41-13 1941 26 57.4 94 08.7 2 IG-41-21 2199 26 56.0 91 12.4 3 89-10 PC-1 2905 26 03.5 94 30.7 4 89-10 PC-2 3632 24 07.1 95 14.8 5 89-10 PC-3 3550 25 10.4 95 04.8 7 89-10PC-5 2881 26 12.5 95 31.9 8 IG-41-23 2324 26 56.1 91 19.4 9 IG-41-26 2231 26 52.7 90 59.7 10 IG-38-10 1538 26 42.7 95 26.0 12 IG-45-15 1692 26 50.7 92 46.8 13 IG-41-28 1972 26 53.3 91 52.7 14 IG-41-29 1878 26 58.8 92 24.3 15 IG-46-11 1856 26 56.6 91 17.7 16 IG-46-7 1625 27 10.3 90 37.2 17 IG-46-8 2180 27 01.5 90 24.5 19 IG-45-14 1919 26 44.3 92 40.6 20 IG-41-18 1616 26 59.6 93 07.1 22 IG-41-19 1584 27 00.1 93 06.9 23 IG-38-18 1786 27 06.4 94 28.1 24 IG-46-12 2097 26 42.2 91 42.7 25 IG-45-9 2288 26 58.0 91 17.2 26 IG-41-24 2002 26 57.5 90 52.3 27 IG-46-9 2380 26 54.8 91 20.8 28 BC-8 3500 25 10.2 95 03.7 29 BC-3 2700 26 08.6 94 31.7 30 BC-4 3850 24 07.0 95 16.0 31 BC-7 1750 24 27.9 96 14.3
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10
AREA 1 AREA 2 ^ .^ 15%
AREA 3
Figure 3. Map showing station locations for core-top benthic foraminiferal study.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. il
foraminiferal distributions and the distribution of organic matter variations throughout
the Late Quaternary. Only 13 core top samples were used because they were not
previously processed for micropaleontologic analysis, and the silt/clay fraction was still
available. For all samples, a small portion of the dried, unwashed sample was
removed, powdered with a mortar and pestle, and weighed. The remaining unwashed sediment was then reserved for micropaleontologic analysis. The biogenic CaCO 3 was
removed using 6 N HC1 and the residue was rinsed three times with distilled, deionized
water, dried, and re-weighed. The residue was analyzed using a CHN analyzer to
obtain the organic carbon and nitrogen content of the sample.
Ash Laver Analysis
Glass from the ash layer in core IG-45-15 was analyzed using a Jeol 733 electron
microprobe on a polished thin section . Nine glass shards were analyzed for 30 second
counts per element with a 25 micron beam, at 15 kV and 2 nanoamps. The standard
used was Smithsonian standard VG568, rhvolite glass.
Planktic Fbraminifera
The planktic foraminiferal biostratigraphic framework for 313 samples from eight
piston cores (Fig. 2) is based on the zonation schemes of Ericson and Wollin (1968)
and Kennett and Huddlestun (1972a). Both of these zonations use changes in patterns
of species frequencies, which often, but not necessarily, reflect climatic shifts (Thunell,
1976a), to establish biostratigraphic boundaries. Ten to thirty gram samples were air
dried, weighed, and washed over a 63 -pi sieve. The sample residue w'as dried and re
weighed to determine the proportions of the sand and silt/clay components. The greater
than 175-/< size fraction (Kennett and Huddlestun, 1972a; Joyce et al., 1985; Joyce and
Williams, 1986) of each sample was split into an aliquot containing approximately 300
planktic foraminifera. Planktic foraminifera from the entire split were counted and
representative specimens of each species were picked. Where sample residue was
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12
sparse the whole sample was picked. For discussion of faunal abundances the
following criteria were used: high = peaks > 20%; moderate = abundances between 8 -
20%; low = abundances between 3-8%; rare = abundances < 3%.
For cores BPX-1 and BPX-10, samples for biostratigraphy were analysed
differently because they were part of an earlier pilot study for this project that did not
require the high-resolution biostratigraphic zonation. These samples were dry-sieved
using a 250-p.m sieve. A 0. lg portion of the fraction retained on the 250-pm sieve was
weighed and specimens of the G. menardii complex (Chapter 3) were counted and
recorded. These samples were later re-examined (see discussion in Chapter 3) to
provide a more detailed stratigraphy for these cores.
Benthic Foraminifera
For the core-top study, 27 samples (top 5 cm) from 23 piston cores and four box
cores were used; water depths of core stations range from 1538 to 3850 m (Table 1;
Fig. 3). The downcore study included 64 samples (2-2.5 cm thicknesses) from four
piston cores where water depths ranged from 1538 to 3632 m (Fig. 1). For both studies, samples were air dried, weighed, and washed over a 63-um sieve. The sample
residue was dried and re-weighed to determine proportions of the sand and silt/clay
components. Each sample was split into a fraction containing approximately 300
benthic foraminifera, and the entire split was picked.
Species diversity was examined using three measures: 1) species richness (S),
which is simply the number of species in a sample; 2) the Shannon-Wiener information
function [H(S)], and 3) species equitability (E). Species richness is generally biased by
sample size with larger samples tending to have a greater number of species. The
diversity index H(S), given by H(S)=-Zpjlnpj, minimizes sample.size bias by
considering the number of species in a sample and their relative abundances (Gibson
and Buzas, 1973). Species equitability, given by E=H(S)/lnS, measures the
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distribution of individuals among species within a sample; so E=l, if all species are
evenly distributed (Buzas, 1972).
Numerical Analyses
R-and Q-mode factor analyses (SAS Institute, 1993) were used to evaluate subtle
assemblage variations and their downcore distributions. In addition, Q-mode cluster
analysis was used to examine both the spatial and temporal distribution of biofacies.
Cluster analysis was performed using JMP (SAS Institute, 1994), a SAS system for the
Macintosh. Details of particular numerical methods used are included in chapters 3 and
4 where the results are discussed. Analysis of variance (JMP; SAS Institute, 1994) was
used to evaluate differences between Pleistocene and Holocene distributions of Corg and
carbonate content (Chapter 2).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2
LITHOSTRATIGRAPHIC RECORD
The uniform, muddy-siliciclastic, and foraminiferal ooze sediments, which
characterize the study area lie primarily within three sedimentary regimes summarized by
Poag (1981): 1) the Mississippi Regime, 2) the Central Texas Regime and 3) the Rio
Grande Regime (Fig.4). These sediments are 80-99% silt and clay. The remaining
sand-sized fraction is dominantly a foraminiferal ooze with lesser components of detrital
siliciclastic grains and organic matter. In the few samples where siliciclastics and
organic matter are the dominant sand-sized components, the foraminifera are severely
diluted and often contain shallow-water species. These intervals are considered to have
been effected by downslope transport. This chapter is an examination of the
sedimentologic record to characterize the sedimentary regime, to facilitate development
of research hypotheses, and to evaluate lithologic components that may be useful in
refining paleoecologic and paleoceanographic interpretations based on foraminifera. Ash Layer Geochemistry
Occurrence of volcanic ash layers in deep-sea cores has been well-documented
in the Gulf of Mexico (Kennett and Huddlestun, 1972a, b; Thunell, 1976). In a detailed
analysis of several hundred deep-sea ash layers, Ledbetter (1985) chemically
"fingerprinted" eleven distinct tephra horizons and mapped their distribution throughout
the Gulf of Mexico, Caribbean Sea and the Pacific Ocean. A single ash layer,
approximately 5 cm thick, lies within the Y 8 subzone in core IG-45-15 at a stratigraphic
depth of 573 cm. The major element composition (Si, Al, Na, Mg, Fe, Ti, Ca and K)
of this ash (Table 2), as determined by microprobe analysis, is most similar to that of
14
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 4. Distribution of Gulf of Mexico sediments showing that studv area (outline) lies within three sedimentary regimes: Rio Grande, Central Texas, and Mississippi Regimes. After Poag (1981).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.53 0.17 0.09 4.44 0.51 12.71 77.60 3.50 3.94 13.12 H-tephri/5) (®) Aah Flow 3.34 3.98 4.40 12.95 77.80 78.67 (Y-8,D)(4) 0.18 0.18 0.17 3.92 2.99 0.85 0.88 0.57 (Y-8,D)(3) 1.68 0.45 0.40 0.36 0.05 0.21 2.70 4.30 13.20 12.77 75.70 78.12 OL-5 (2) OL-5 1.24 3.50 0.70 1.60 0.65 0.67 0.52 77.20 * * Data renormalized to dry100% weight. 3.600.63 4.00 77.80 0.08 0.18 0.30 4.21 4.60 0.11 0.09 0.13 IG-45-150) SC-7(2) (2) OL-4 (1) (1) This study; Rose(2) et al. (1979); Ledbetter(3) (1985); (4) Raybeket al.(1985);et Drexler (5) al.(1980).* FeO 0.56 0.40 K20 CaO 0.63 MgO Si02 77.89 Ti02 Na20 3.65 AI203 12.96 12.60 12.80 Major Element Table 2. Ash Bed Geochemistry: Major Element Composition (%).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17
the high-K rhyolitic ash and pumice (SC-7, H-tephra and Ash Row; Rose et al., 1979;
Drexler, 1980) that resulted from the Los Chocoyos eruption of Atitlan volcano in
Guatemala and to the composition of deep-sea ash layers that have been chemically
correlated to the Los Chocoyos Ash (Y- 8 , D; Ledbetter, 1985; Raybek et al., 1985; see
Table 2). Geochemical tracing of the ash layer in core IG-45-15 to the Los Chocoyos
eruption yields an age of 84 ky for the ash layer interval and confirms biostratigraphic
evidence suggesting this core penetrates the pentultimate interglacial zone X. Sediment Accumulation Rates
Sediment accumulation rates throughout the lower bathyal and abyssal regions of the
northwestern Gulf are quite variable (Table 3; Fig. 5), indicating that sedimentary
processes in this region are complex and may involve several different sediment sources
and transport mechanisms. Cores IG-41-21 and IG-41-26 (Area 1), from abyssal water
depths (2199 m, 2231 m respectively), have the highest Holocene and latest Pleistocene
sediment accumulation rates, 41-77 cm/kv, due to their proximity to Mississippi River
influx. These rates agree with those reported by Leventer et al. (1982,1983) for cores
from Orca Basin, which is also within Area 1. In contrast, just to the west of Area 1
and from lower bathyal depths (1500-2000m), cores IG-45-15, BPX-10, and BPX-1
(Area 2; Fig. 5) have the lowest sediment accumulation rates, 4-11 cm/ky. Sediment
thicknesses decrease westward (Berryhill, 1982), and low rates such as these are not
uncommon. Finally, cores from farther south and west (PC-1, PC-4, PC-2; Area 3;
Fig. 5), also from abyssal depths (2905,3550,3632 m respectively), show
intermediate to high sediment accumulation rates, 14-36 cm/ky and these rates decrease
basinward.
Proximity of the Mississippi River outflow suggests that the Orca Basin region
(Area 1) should be a sediment sink. Very high sediment accumulation rates documented
by this and other studies (Leventer, 1982, 1983; Coleman et al., 1991) are not unusual
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18
AREA 1 AREA 2
V U £ AREA 3 5/5 919* I /V n
24121
100 Holocene sediment accumulation rates 24/21 114/15 Latest Pleistocene (Y1) sediment accumulation rates
Figure 5. Map with station locations showing sediment accumulation rates in the Holocene (bold) and the Pleistocene subzone, Y 1 (italics at these sites; na indicates no data).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9.8 15.4 13.9 16.7 PC-2 19.5 20.5 26.7 15.4 19.5 35.646.7 23.8 153.7 56.724.4 25 BPX-1 IG-41-21 IG-41-26 PC-1 PC-4 ash tolayer Plcistocene/Holocene boundary 8 5.1 9.0 41.0 no base IG-45-15 3.8 14.6 9.8 9.8 * Interval from Y * BPX-10 Z172 9.2 1.7 6.7 Y1 Zone Total Y*Total 7.0 T otal Holoceneotal (Z) T 5 11.4 7.9 43.6 77.2 Table 3. SedimentAccumulation Rates (cm/kyr). l
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20
for a region with an enormous sediment influx. In addition, intraslope-interlobal
basins, which may be blocked submarine sediment conduits (e.g., Pigmy Basin) or
basins formed by salt diapirs coalescing around a depression (e.g., Orca Basin), also
are characterized by very high rates of sediment accumulation (Martin and Bouma,
1978; Stelting, 1984; Byrant et al., 1990, 1991). Sediment accumulation in these
basins results from hemipelagic deposition, frequent slumping, and influx of turbidites
and other products of large- and small-scale mass movements off the basin flanks
(Coleman et al., 1991). The effect of semi-continuous salt diapiric structures and ridges
(which trend more or less east-west) as well as isolated salt lobes on sediment transport
on the Texas-Louisiana slope is to channel the sediment flow, often resulting in rapid
and direct transport onto the continental rise and abyssal plain through openings in the
Sigsbee Escarpment (Martin, 1984; Lee et al., 1996). Satterfield and Behrens (1990)
documented a canyon/channel system on the upper slope of the western Gulf that may
have facilitated the filling of a series of intraslope basins. Areas between these filled
basins constitute an erosional canyon, which clearly indicates that this system is an
effective sediment conduit So the efficacy of sediment dispersal to the west may be
inhibited by sediment being trapped in intraslope basins and/or diverted to the south,
directly onto the Sigsbee Plain.
Area 2,100 km to the west of the Area 1 (Fig. 5), is either sediment starved or is a
sediment source area. Markedly low sediment accumulation rates for this lower slope
area suggest: 1) it is being bypassed by sediment or too far removed from sediment
sources; 2) sediment is trapped on the shelf, never reaching the lower slope; or 3)
sediment is being periodically removed. Shelf regions to the north are characterized by
erosion, nondeposition and transport (Roberts et al., 1986; Morton, 1991), and are
reported to have the lowest deposition rate along the Texas-Louisiana coast (Curray,
1960). According to Berryhill (1982), Holocene sediments in this shelf area are either
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very thin or absent; this same pattern holds true for the latest Pleistocene sediments of
this study (Fig. 5). Apparently, sediment is not being trapped on the shelf. Reasonable
explanations for these low sediment accumulation rates include sediment being diverted
from this region into intraslope basins or channeled directly onto the continental rise and
Sigsbee Plain. Alternatively, this region may be a sediment source area, with sediment
being periodically removed.
Sediment accumulation patterns in the western part of the study area (Area 3; Fig. 1,
5), at the deepest abyssal stations, are very different from Areas 1 and 2, clearly
reflecting different sediment sources and dispersal mechanisms. In addition, the pattern
of Holocene sediment accumulation rates is different from that of the latest Pleistocene
(subzone Y l), suggesting temporal as well as spatial differences in sediment
accumulation. This area is part of the Western Gulf wave field recently documented by-
Behrens (1994). Sediment sources and mechanisms forming this wave field remain
enigmatic, but the direction of wave migration suggests that both Alaminos and Perdido
Canyons are potential sediment sources (Behrens, 1994) and/or sediment conduits.
That such canyon systems are sediment dispersal paths has been suggested by
Satterfield and Behrens (1990).
All three of the stations in Area 3 are due south of Alaminos Canyon which has a
small but well-developed submarine fan at its base (Behrens, 1994), indicating that it is
an active sediment conduit. Holocene sediment accumulation rates steadily decrease to
the south (36-14 cm/ky; Fig. 5); which would be expected if the stations were at
increasing distances from a point source of sediment to the north. In addition, the
complicated physiography of the Rio Grande Slope and the Mexican Ridges west of the
study area may restrict sediment influx from Texas coastal sources. For the latest
Pleistocene, the sediment accumulation rates are nearly constant, 15-21 cm/ky. The low
rate for the northernmost station (which has the highest rate for the Holocene) and the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. highest rate at the middle station are difficult to explain. It is possible that there was
more input from Texas coastal sources during the latest Pleistocene and that station
PC-4, located downslope of the Rio Grande outflow, received an increased influx of
sediment relative to the adjacent stations. These variable sediment accumulation rates
throughout the northwestern Gulf are the result of the complex interplay between
sediment influx and the salt-dominated bottom physiography.
Organic Carbon (C 0 r g )
Surface Sediments
Available data on the distribution of Corg content in Gulf of Mexico surface
sediments is very scarce. These data indicate that the distribution of Corg in surface
sediments (Fig. 6) is variable (0.23 to 1.34% with a mean of 0.87 ± 0.04%) and exhibit
no trend with geographic location or with water depth (Koons and Perry, 1976; Jones
and Sen Gupta, 1995). An ANOVA comparison of Coro content in surface sediments
from the Mississippi Cone region and the remainder of the basin found no statistically significant difference (F =0.0234; P = 0.8795) in Corg content of surface sediments
between these two areas. Trask (1953) found that organic content (estimated as 1.8
times the carbon content) for near-surface sediments (10-50 cm ) increased basin ward,
reaching a maximum ( 1-2%) at bathyal depths, and then decreased toward the basin
center, where it was approximately 1% at abyssal depths. In addition, he suggested that
organic content was influenced primarily by sediment texture and topography (Trask, 1953). This trend of basinward increase in Corg content is not reflected in the data
reported here.
Carbon/nitrogen (C/N) ratios in the study area, which are often related to organic
matter source (Joyce et al., 1985), range from 4.8 to 13.3 (Fig. 7). C/N values
between 4-6 indicate marine organic matter (plankton) and values between 12-25 reflect
a terrestrial plant source (Muller, 1977; Prahl et al., 1980). Most C/N ratios within the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.7 0.7 * <01.12 8 fife ESc> 62 62 0.84 . 0/63 v . • • This study This o Perry(1976) & Koons . . Distributionof percent organic in surfacecarbon sediments (Corg) of northwestern Gulfof Mexico. 6 Figure
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CD CO CQ
o •
at
LU
oc
CO* z CO U
#u»
_ ir t. Figure Figure 7. Distribution of carbon/nitrogen ratios (C/N) surface in sediments of northwestern Gulf of Mexico.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25
study area fall between these categories indicating that organic matter is derived from
both marine and terrigenous sources (Jones and Sen Gupta, 1995). Despite this
prevalence of mixed-source organic carbon one sample clearly indicates some
terrigenous (13.3) influence, suggesting that even at lower bathyal depths a terrigenous
influence can be felt.
Another indicator of organic carbon source is the 6 13C signature of sedimentary
organic carbon (Eckelmann, 1962; Sackett and Thompson, 1963; Parker et al., 1972;
Newmann et al., 1973; Hedges and Parker, 1976). Although some early studies
(Sackett et al., 1965; Rogers and Koons, 1969) suggested that the temperature of the
surface-water in which plankton lived was the primary factor controlling carbon isotopic
signature of organic carbon, more recent work clearly demonstrates that variation in
organic carbon source (marine versus terrestrial) is the dominant factor in controlling
carbon isotopic signatures in surface sediments in the Gulf of Mexico (Sackett and
Rankin, 1970; Jasper and Gagosian, 1989).
The 6 13C of organic carbon in surface sediments within the study area (Fig. 8 )
shows distinctly different patterns of organic carbon source. Organic matter in the far
western portion of the basin is clearly of marine origin (-18.8 to -21%o), whereas in the
vicinity of the Mississippi Cone, there is a strong terrigenous influence (-24.2 to -26.3%o). The 6 13C values throughout the remainder of the basin indicate mixed-
source (-21 to 24°/oo) organic carbon as indicated by the C/N ratios.
Downcore Distribution
The downcore Pleistocene Corg values (Table 4) are noticably more variable (0.30 to
1.61%, mean = 0.85 ± 0.04%) than those of the Holocene (0.52 to 0.89%, mean = 0.73 ± 0.02%). An ANOVA comparison of the Corg content in downcore Pleistocene
and downcore Holocene samples indicates there is a statistically significant difference (F
= 6.1286; P = 0.0150) between the two. Data from core IG-45-15
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. as to
------Koons Koons and Perry (1976) □Behrens 1989comm. per. o Newmano ef al. (1973) ANorfham et al. (1980)
.-25.7 -23.3 -2 3 .1 81C of 81C organicof carbon from surface sedimenfs 0
-22 -22.3 22.0 21.2 ••- S/GSBEt^ . 0 4 n - 2 1 „ 7 - 2 1 . 22.91 22.91 V21.4 •1 9 0 ° -19.5° 19.8 0-19.2 PREDOMINANTLY MARINE CARBON 1Q0 13C of sedimentary Corg in in surface ofsedimentary sediments Corg showing13C geographic distribution oforganic matter type. 6 . . 8 Figure
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Table 4. Downcore Corg (%)•
IG-41-21 PC-1 PC-4 PC-2 IG-45-15 Depth TOC Depth TOC Depth TOC Depth TOC Depth TOC (cm) (%) (cm) (%) (cm) (%) (cm) (%) (cm) (%)
10 0.88 10 0.81 30 0.87 50 0.60 15 0.60 80 0.88 30 0.84 80 0.73 80 0.58 55 0.90 90 0.89 50 0.80 90 0.74 90 0.52 75 0.70 130 0.86 70 0.78 100 0.86 100 0.56 95 0.80 180 0.78 90 0.79 115 0.67 120 0.52 215 0.70 220 0.86 110 0.78 150 0.75 150 0.58 395 0.60 240 0.77 150 0.75 180 0.66 160 0.59 475 0.30 260 0.69 180 0.74 220 0.66 200 0.41 535 0.40 300 0.73 200 0.67 240 0.57 240 0.63 595 0.40 320 0.72 220 0.63 260 1.00 260 0.58 655 0.40 340 0.70 260 0.63 280 0.82 300 0.83 775 0.60 360 0.79 300 0.76 300 1.26 340 0.68 420 0.84 320 0.70 320 0.98 395 0.88 440 1.02 360 0.63 340 0.60 460 1.57 380 1.21 370 0.59 470 1.61 400 0.79 380 0.66 480 1.53 440 0.96 400 0.96 540 1.36 450 0.59 420 0.54 620 1.27 460 0.93 640 0.88 480 0.87 680 0.88 510 1.03 700 0.71 530 1.33 710 0.92 570 0.53 720 0.99 590 0.84 740 1.15 630 0.75 760 1.07 650 0.74 780 1.18 660 0.94 800 1.09 820 0.99 840 0.89 860 0.87 880 0.73 900 0.97 930 0.96
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28
(Behrens, 1989, per. comm.), which is very limited (n=ll), show little of the
Pleistocene variation at all. In contrast, C^g data from this study (cores IG-41-26, PC-
1, PC-2 and PC-4, n=92), which is a more detailed record, show two late Pleistocene peaks (Fig. 9). These C ^ increases, which occur in the Y 1 subzone in all five cores
and in the Y3 subzone in two cores, are the sources of most of the late Pleistocene C^a
variability. But for these fluctuations, the organic carbon content remains relatively
constant throughout the late Quaternary, possibly indicating that the COTg increases are
related to variations in the influx of terrigenous organic matter. Downcore 6 I3C data (Behrens, 1989, per. comm.) from two cores, IG-45-15 and
IG-41-21, show a marked shift toward lighter 6 13C values (to almost -26°/oo) in the late
Pleistocene (Fig. 10). In IG-45-15, the 6 13C variations appear cyclic, with a shift back
to heavier 6 13C values at the Y5/Y6 boundary and which continue into the pentultimate
interglacial zone X. This cyclicity, with the lighter S13C values reflecting an increased
influence of terrigenous organic carbon during glacial intervals and the heavier values
indicating a shift to a marine organic carbon source during interglacials, has been well-
documented in the northwestern Gulf of Mexico (Parker et al., 1972; Newmann et al.,
1973; Sackett and Rankin, 1970; Northam et al., 1981; Jasper and Gagosian, 1989).
The cyclic nature of these isotopic shifts precludes diagenesis as the primary' factor
controlling these 6 13C variations. If degradation of organic matter was the primary'
factor governing the 6 l3C variations they would exhibit a monotonic trend (Rogers and
Koons, 1969; Jasper and Gagosian, 1989) and be accompanied by a monotonic
decrease in C/N ratios (Nakatsuka et al., 1995).
Holocene 6 13C values increase, indicating a dominantly mixed-source COTg (-23 to
-21%o), which is common in northwestern Gulf surface sediments (Fig. 8 ); however, latest Holocene 6 13C values in IG-4S15 are approaching -20, w'hich indicate a marine
organic carbon source (Fig. 10). Despite the limited 5 13C data, the climatically-forced.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to Z1 Y2 Y3 PC-2 Percent Zi Y1 Y2 Y3 12 Y4 meltwaterinterval. 1 1 PC-4 P ercent Z1 Y1 Z2 Y 2
1 PC-1 Percent «»«!»» o o Zl Yl Y4 Z2 Y2 Y5 Y6 Y3 7 . . . i i / / s / Percent Downcore Total Organic Carbon IG-41-21 . . . 0 0 1 JLl ¥8 2,2 Y4 Y5 Y6 Y7 XI Y3 X2 X3 Y2 -Yl— . . . . 1 1 ------y Percent \ IG-45-15 / . . . . - - 2 0 0 400 800 1000 > Figure 9. for Downcore fivestations plots showing increase of withinpercent Y notable CQrg Corg OJ 0 a a a. o 3 3 ft U
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30
S^CcPDB)
IG-45-15 IG-41-21 -26 -24 -22 -20 -26 -24 -22 -20 Z1 7 2 -VI Y2
200 200 - Y3
Y4 Y5 400 - 22 Y6
Y7
600 600 XI Y2
X2 Y3 X3 800 800 - Y4 Y5
Y6 1000 1000
Figure 10. Downcore plots of 8l3c of sedimentary COTg for two stations showing increase in terrestrial Con, in glacial (Y) interval.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31
cyclic trend of lighter 6 13C values during interglacial intervals and heavier 6 13C values
during glacials, as seen in other Gulf of Mexico late Quaternary sediments (Jasper and
Gagosian, 1989; Jasper and Gagosian, 1990), is clearly evident in core IG-45-15. This
trend reflects shifts in organic carbon source from a dominantly terrigenous source
during low sea-level stands to a more marine organic carbon source, during high sea-
level stands. Calcium Carbonate
Surface Sediments
Little has been published about the distribution of calcium carbonate in surface
sediments in the northwestern Gulf of Mexico. Trask (1953) reported a trend of
basinward increase in calcium carbonate content in near-surface sediments; to a
maximum of 30% in the abyssal Gulf. In general, the carbonate content of near-surface
sediments from this study (Fig. 11) are in agreement with those of Trask (1953),
although samples from stations PC-4 and IG-41-26 differ slightly from Trask's fields.
Williams et al., (1988) reported an increase in carbonate content of surface sediments
(0-1 cm) with increasing water depth from shelf to abyssal plain. In addition, they
found very low carbonate content (3%) at the Mississippi Delta and steady increases to
the west (reaching 15% just east of Garden Banks) suggesting that dilution by incoming
siliciclastics is an important factor in controlling patterns of calcium carbonate
distribution in the northwestern Gulf of Mexico.
Downcore Distribution
Downcore carbonate content (%) data (Table 5) was obtained for six of the eight
cores (Behrens, 1989 pers. comm.) as a means to examine surface-water productivity
and carbonate dissolution patterns. Although Pleistocene carbonate values (8.2-38%,
mean=l 8.6 ± 0.450%) and Holocene carbonate values (8.9-34%, mean=21.3 ±
0.453%) appear similar (Table 5), an ANOVA comparison between the two shows that
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. w IO contours (%) from Trask (1953) and and Surface Near Sediments Calcium Carbonate in Surface • (%) this study t s O * 9* » eg . . Variationsof percent calcium carbonate in surface sediments showingbasinward increase. 11 Figure
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5. Downcore Calcium Carbonate (%).
IG-45-15 IG-41-26 IG-41-21 PC-1 PC-4 PC-2 Depth CaCOa Depth CaCQs Depth CaCOs D epth CaCQ3 Depth CaC 03 D epth C aC 03 (cm ) (%) (cm ) (%) (cm) (%) (cm ) (%) (cm) (%) (cm ) %
15 33.9 15 17.4 15 21.3 10 24.7 10 26.5 15 25.2 35 25.5 35 21.5 35 21.4 22 23.7 20 26.2 30 27.6 55 21.2 55 22.2 55 23.9 40 24.6 40 27.1 42 28.2 75 24.1 75 19.3 75 23.4 60 24.1 60 26.0 60 27.1 95 18.1 95 20.8 95 21.7 80 23.4 80 29.2 80 25.4 115 18.5 115 19.0 115 22.1 100 25.5 104 26.6 100 26.0 135 17.6 135 18.6 135 22.2 120 27.5 120 24.3 118 28.7 155 18.4 155 26.1 155 19.7 140 23.3 140 24.2 141 25.7 175 20.1 175 22.6 175 22.4 160 25.1 160 21.3 155 18.8 195 21.4 195 22.2 195 22.4 180 23.8 180 23.7 180 15.4 215 24.4 215 20.1 215 21.2 200 23.3 200 22.1 200 19.4 235 23.8 235 22.0 235 22.8 220 20.4 220 29.2 215 22.4 255 21.1 255 20.5 255 19.0 240 23.5 240 25.3 233 18.4 275 23.2 275 20.3 275 10.7 260 14.6 260 15.5 242.5 16.4 295 22.1 295 22.9 295 20.5 280 22.1 280 18.9 260 20.2 315 20.9 315 22.4 315 15.2 298 22.8 300 17.4 280 18.1 335 23.6 335 18.7 335 13.6 320 21.6 320 19.1 300 18.5 355 25.9 355 19.5 355 16.5 340 26.1 340 18.9 320 20.5 375 23.8 375 15.9 375 18.7 360 22.7 360 8.60 340 18.4 395 23.6 395 18.9 395 21.3 380 16.9 380 14.3 359 17.5 415 15.3 435 19.4 415 20.7 400 18.1 400 17.3 380 17.7 435 21.6 455 17.8 435 21.0 420 13.1 420 11.9 395 12.5 455 16.7 475 16.2 455 15.2 440 16.5 440 17.5 475 16.4 495 12.0 475 14.9 452 13.9 460 16.0 495 20.1 515 18.2 495 16.4 480 19.4 515 23.5 535 12.2 515 13.9 490 9.30 535 31.5 555 8.90 535 13.4 510 16.9 555 23.5 575 12.7 555 14.7 499 17.0 575 16.6 595 17.7 575 15.5 540 18.7 595 8.20 615 16.1 595 17.0 560 17.1 615 26.0 635 12.8 615 18.2 580 17.6 635 35.2 655 18.2 635 15.7 600 16.2 655 37.7 675 17.4 655 16.6 620 17.6 675 26.6 695 16.0 675 16.0 640 14.3 695 19.9 715 17.5 695 19.5 660 17.8 715 20.6 735 19.0 715 15.4 735 14.3 755 13.1 735 17.1 755 14.2 775 20.3 755 16.6 775 30.3 795 17.8 775 16.1 815 16.9 795 17.2 815 15.3 835 14.8 855 12.9 875 14.3 895 17.5 915 16.2
with permission of the copyright owner. Further reproduction prohibited without permission. 34
they are significantly different (F=18.2904, p < 0.0001). In general, Pleistocene and
Holocene carbonate content exhibits relative stability, forming a baseline from which
several notable fluctuations in carbonate content occur (Fig. 12). Deviations from this
baseline generally begin with a steady increase within the Y 1 subzone in all but two
cores, reaching a carbonate maximum (to 30%) in the early Holocene, decreasing
slightly into the middle Holocene, and then reaching another carbonate maximum (to
30%) in the middle to late Holocene. Core IG-41-26, an expanded section, contains a
very detailed record of Holocene carbonate fluctuations with a carbonate maximum
(27%) just below the Z1/Z2 boundary and a carbonate minimum (10%) mid-way
through subzone Z2.
The overall increase in carbonate content from Pleistocene to Holocene , which
ranges from 6-12%, occurs in the Y1 subzone in five of the six cores (Fig. 12). For
most cores, Pleistocene carbonate values exhibit a few small deviations from the
Pleistocene carbonate baseline; an exception is core IG-45-15, which will be discussed
separately. Two carbonate decreases in the Y2 subzone are evident in cores PC-2 and
PC-4: the first decrease, about 6 %, occurs just below the Y1/Y2 boundary and the
second, smaller decrease about 3%, occurs above the base of the Y2/Y3 boundary.
Both cores also show decreasing carbonate content into the Y3 subzone, however, in
PC-4 this decrease is an abrupt trough that increases and then remains constant
throughout Y3. Core IG-41-21 shows only minor (1-4%) deviations from the
Pleistocene baseline in Y2, Y3, and Y5.
Core IG-45-15, which contains the most complete strati graphic record, shows
several striking fluctuations in carbonate content in the late Pleistocene (Zones X and
Y). Overall, carbonate content increases from the latest Pleistocene (Y 1) through the
Holocene (to 34%). Through subzones Y3, Y4, and Y5 minor fluctuations (1-5%)
occur around the Pleistocene carbonate baseline. In contrast, large perturbations (up to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. u> 12 Yl Y2 Zl Y3 > 3632 m f
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 6
30%) in carbonate content occur in subzones Y 6 , Y8 and X2 (decreases) and Y7, X3
and at the X1/X2 boundary (increases). Discussion and Summary Productivity and Carbonate Dissolution Signals
High Corg values within the Y1 interval may indicate that incoming glacial meltwater
was nutrient enriched with terrestrial COTg. The relatively depleted 6 13C values within
the Y 1 subzone confirm an increased presence of terrestrial Corg in the sediment The
addtition of nutrient-rich, glacial meltwater to Gulf of Mexico surface waters may
enhance carbonate production, including planktic foraminifera, providing that the low
temperature and salinity conditions were not too severe.
Fluctuations in carbonate content frequently have been attributed to one or more
causes: dissolution, productivity’, terrigenous dilution, and transport or winnowing
(Damuth, 1975; Thunell, 1976a, b; Joyce et al., 1985; Steinsund, 1994). In the
northwestern Gulf of Mexico, all of these factors probably play a role in determining the
carbonate content of these sediments, however, isolating the influence of each factor is
difficult. Patterns of carbonate dissolution throughout the western Gulf of Mexico are
poorly understood. For example, several episodes of brief, but intense dissolution have
been reported from the southwestern Gulf throughout the late Quaternary (Thunell,
1976a, b), and evidence of less-corrosive glacial bottom-water (presence of a
dissolution-prone assemblage of benthic foraminifera) has been reported from the same
area (Marchain-Castillo et al., 1995). These contrasting reports suggest that the
compostion of Gulf of Mexico bottom-waters has fluctuated throughout the late
Quaternary. Dissolution indicators such as frequencies of solution-prone versus
solution-resistant planktic species and composition of benthic foraminifera! assemblages
are necessary to evaluate the effect of dissolution on the carbonate content throughout
the latest Quaternary.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37
Contributions by other factors such as surface-water productivity, dilution by
terrigenous influx, and/or lateral or downslope transport are evident in some cores.
Carbonate content and Corg appear to be inversely related; carbonate content increases
from the Pleistocene into the Holocene, whereas Corg decreases. This inverse
relationship suggests that during the Pleistocene, with increased continental area available for erosion, the influx of terrigenous material, hence COTg, increased,
swamping the pelagic rain of carbonate. Although dilution by terrigenous sediments is
common throughout most of the glacial Y intervals, as noted by the lower percentages,
increased carbonate begins in the uppermost part of the Pleistocene Y 1 subzone (Fig.
12). Carbon isotopic data (Fig. 12) indicate a predominance of terrigenous Cor depleted 6 13C values) during glacial intervals with a gradual return to more enriched 6 13C values approaching and into interglacial intervals. The organic carbon and carbon isotopic data clearly indicate an increased inflax of terrigenous Corg during glacial intervals which may have diluted the pelagic rain of carbonate to the seafloor. Sediment Accumulation Rates Varying sediment accumulation rates in the north-central Gulf of Mexico reflect several sediment sources and/or transport mechanisms. The effectiveness of Area 1 (Fig. 5), a region with very high sediment accumulation rates (41-77 cm/ky), as a sediment dispersal route to the west may be inhibited by sediment being trapped in intraslope basins and/or diverted south, directly onto the Sigsbee Plain. In contrast, Area 2, a region with comparatively low sediment accumulation rates (4-11 cm/ky), may be a sediment-starved or sediment-source area Intermediate sediment accumulation rates (14-36 cm/ky), which are found in Area 3, reflect a reduced influx of coastal terrigenous sediment, resulting in the increased influence of pelagic sedimentation. These variable sediment accumulation rates are the result of the complex interplay between sediment influx and the salt-dominanted bottom physiography, which effects Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 sediment dispersal in the north-central Gulf of Mexico. A clear understanding of patterns of sediment accumulation is critical in order to evaluate the faunal signals contained within the sedimentary record. Although there is little sedimentologic or biostrati graphic evidence to suggest the presence of either downslope or lateral transport of sediment, the prevalence of such mass movement in the deep Gulf of Mexico is well-documented (see Sediment Accumulation Rates section) and it cannot be ruled out as a mechanism for influencing the downcore distribution of carbonate. Certainly the varying rates of sediment accumulation (Fig. 5) effect the carbonate distribution to some degree. This variation is evident in core IG-41-26 which has an expanded strati graphic section that reflects small perturbations, and core IG-45-15 with the reduced, thin biostratigraphic zones, that records rather large fluctuations in carbonate content (Fig. 12). However, carbonate content in surface sediments (Fig. 11) is generally highest in the region that exhibits the lowest sediment accumulation rates (Area 2), supporting the notion that dilution by the influx of terrigenous sediments can severely affect the carbonate record. Highly variable sediment accumulation rates in the north-central Gulf of Mexico do not distort the sedimentary record to such a degree that Corg and carbonate signals are uninterpretable. That the influx of cool, less saline meltwater also brought higher nutrient levels to Gulf of Mexico surface waters is evident in the downcore distribution of Corg, and supported by more depleted 6 13C values (indicating more terrigenous Cor„) and increasing carbonate content within the Y1 meltwater interval. Thus, increased nutrient levels, which may influence the production of planktic foraminifera, must be considered, along with temperature and salinity conditions, when evaluating the effect of glacial meltwater on planktic foraminifera. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Synopsis The lithostratigraphic record reveals several large-scale spatial and temporal patterns. The study area is characterized by three regions that have distinctly different sediment accumulation rates that are strongly influenced by sediment supply, bottom physiography and sediment transport. In surface sediments, the amount of organic matter exhibits no geographic or depth-related trends, and shows no relationship to sediment accumulation rates. Conversely, the surficial distribution of SI3C of sedimentary organic carbon, often indicative of organic matter source, reveals distinct geographic zones that delinate Corg from marine versus terrestrial sources, thus reflecting areas strongly influenced by terrigenous influx. In general, carbonate content of surfical sediments displays a trend of basinward increase which probably reflects dilution by terrigenous influx near the basin margin. Temporal patterns in the lithostratigraphic record are linked to glacial-interglacial shifts. Increased Corg content during the glacial Y interval, relative to the interglacial Z zone, with a maximum within the Y 1 meltwater interval, suggests increased nutrient levels associated with incoming glacial meltwater. Depleted 6 13c values in the glacial Y zone suggest a stronger influence of terrigenous-source Corg and are consistent with the notion of increased nutrient levels associated with incoming glacial meltwater inferred from increased Corg content of glacial intervals. Calcium carbonate content is decreased within the glacial Y interval, relative to the interglacial Z zone. This pattern may be the result of dilution by increased terrigenous material, carbonate dissolution, and/or decreased surface-water productivity. Calcium carbonate content begins to increase in the upper Y 1 subzone and reaches a maximum in the early Holocene. This early Holocene maximum may be related to the CaCC >3 preservation event documented by Broeckeret al. (1993) in the western equatorial Atlantic. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 The spatial and temporal patterns revealed by the lithostratigraphic record pose several questions which can be examined by using the benthic and planktic foraminiferal records. For example, was incoming glacial meltwater nutrient rich? Can the influence of carbonate dissolution, surface-water productivity, and dilution by terrigenous influx be isolated? Is the early Holocene preservation event evident in benthic and planktic foraminiferal distributions? What influence, if any, does Corg source have on the distribution of benthic foraminifera? Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3 PLANKTIC FORAMINIFERAL RECORD Modem, large-scale, planktic foraminiferal provinces are largely distributed latitudinally from pole to equator (Fig. 13) reflecting the influence of long-term climate on planktic foraminiferal assemblages (Hemleben etal., 1989), thus making them useful both as paleoecologic and biostratigraphic tools. For the late Quaternary, planktic foraminiferal speciation and extinction events are few, so high-resolution biostratigraphic zonal schemes for the Pleistocene and Holocene are based on shifts in relative abundance. The goal of this chapter is an examination of glacial-interglacial paleoceanographic changes in surface waters as reflected by planktic foraminifera. The objectives of this chapter are: to develop the planktic foraminiferal stratigraphic framework, and to evaluate their surficial and downcore distributions to examine several hypotheses: 1) meltwater influx into the Gulf of Mexico is reflected by planktic foraminiferal frequency variations; 2) glacial-interglacial surface-water productivity and dissolution events can be recognized by changing planktic foraminiferal frequencies; and 3) the Younger Dryas cooling event in the Gulf of Mexico is evident from planktic foraminiferal frequency patterns. Planktic Foraminifera in Surface Sediments Distributional studies of planktic foraminifera from surface sediments of the Gulf of Mexico have used several methods to examine the utility of planktic foraminifera to reflect surface-water conditions. Although slight variations in species frequencies occur, the faunal composition of the planktic assemblage is generally ubiquitous throughout the Gulf, with subtropical species such as Globigemaides ruber dominating the assemblage. Snyder (1978), reported a weak relationship between the distribution 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 2 -60' -45' -30°. SUBTROPICAL ~15' TROPICAL -0“ 15° modified from Toideriund and Be' (1971) Figure 13. Map of planktic foraminiferal provinces in the North Atlantic Ocean. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 of planktic species frequencies, and the patterns of temperature and salinity of the overlying surface watermass. Because the Gulf of Mexico is a restricted, marginal sea, overall variation of physical parameters in surface-waters is subtle, and most strongly influenced by seasonal effects. Thus, the reflection of this subtle variation often cannot be detected by mapping species frequencies alone; more robust numerical techniques must be used. In one such attempt, Brunner (1979) recognized five faunal assemblages using a Q-mode factor analysis and related them to surface watennass characteristics such as salinity, temperature, permanent and seasonal thermoclines, and dissolution related to highly productive surface waters. Planktic foraminiferal census data of core tops from this study (Appendix 1) reveals a warm-temperate to subtropical assemblage, with high frequencies of Globigerinoides ruber, Globigerinoides sacculifer, Globorotalia menardii, Globorotalia truncatulinoides (r), Neogloboquadrina duterteri, and Pulleniatina obliquiloculata, consistent with findings of earlier studies. One measure of carbonate dissolution, a comparison of relative frequencies of Globigerinoides ruber, a dissolution-prone species, and Neogloboquadrinadutertrei, a dissolution-resistant species (Snyder, 1978; Coulboum, 1980; Hemleben, 1989), suggests that dissolution has had little effect on most samples. Three exceptions are samples IG-38-18, IG-41-21, and IG-41-29. These samples have extremely low frequencies (6-9%; compared to 11-57% in other samples) of Globigerinoides ruber and moderate to high frequencies (8-19%) of Neogloboquadrina dutertrei, suggesting that, although dissolution has occurred, it altered only the most delicate forms in these samples. Downcore Planktic Foraminiferal Record Twenty-one species of planktic foraminifera were identified (Table 6; Appendix 2), of these, six were used to place Kennett and Huddlestun (1972a) subzone boundaries within the Ericson and Wollin (1956a, b; 1970) zonal scheme. Relative frequency Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44 Table 6. Taxonomic List of Planktic Foraminifera Globorotalia menardii (Parker, Jones and Brady) = Rotalia menardii Parker, Jones and Brady, 1865 G. tumida (Brady) = Pulvinulina menardii Brady var. tianida Brady, 1877 G. flexuosa (Koch) = Pulvinulina tumida Brady var. flexuosa Koch, 1923 G. ungulata Bermudez, 1960 G. crassaformis (Galloway and Wissler) = Globigerina crassaformis Galloway and Wissler, 1927 G. inflata (D'Orbigny) = Globigerina inflata d'Orbigny, 1839 G. tnmcatulinoides (d'Orbigny) = Rotalina mwcalulinoides d'Orbigny, 1839 G. scitula (Brady) = Pulvinulina scitula Brady, 1882 Globigerinoides ruber (d'Orbigny) = Globigerina rubra d'Orbigny, 1839 G. conglobatus (Brady) = Globigerina conglobata Brady, 1879 G. sacculifer (Brady) = Globigerina sacculifera Brady, 1877 Hasterigerina aequilateralis (Brady) = Globigerina aequilateralis Brady, 1879 Globigerina falconensis Blow, 1959 G. bulloides d'Orbigny, 1826 Globigerinella calida (Parker) = Globigerina calida Parker, 1962 Beella digitata (Brady) = Globigerina digitata Brady, 1879 Globorotaloides hexagona (Natland) = Globigerina hexagona Natland, 1938 Pulleniatina obliquiloculata (Parker and Jones) = Pullenia sphaeroides var. obliquiloculata Parker and Jones, 1865 Sphaeroidinella dehiscens (Parker and Jones) = Sphaerodina bulloides var. dehiscens Parker and Jones, 1865 Candeina nitida d'Orbigny, 1839 Orbulina universa d'Orbigny. 1839 Neogloboquadrina dutertrei (d'Orbigny) = Globigerina dutertrei d'Orbigny, 1839 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45 variations (%) of most species show trends similar to those of Kennett and Huddlestun (1972a), but in a few cases there are notable differences. The stratigraphic framework below outlines the frequency distributions of planktic species within these cores (Table 7; Figs. 14-21) following the framework of Kennett and Huddlestun (1972a). The Globorotalia menardii complex as defined by Kennett and Huddlestun (1972a) is used here. It includes the subspecies of Globorotalia menardii menardii, Globorotalia menardii tumida and Globorotalia menardii flexuosa. Kennett and Huddlestun (1972a) counted frequencies of 28 species of planktic foraminifera to develop their zonal scheme. Of these, they actually used only eight species to define their zonal boundaries, although they did describe frequency variations of several others within the context of their scheme. In all cores of this study, except BPX-1 and BPX-10, frequency counts were based on 21 planktic species and of these only six were found necessary to clearly recognize the Kennett and Huddlestun (1972a) subzones. The BPX cores, which were part of an earlier pilot study (Jones, 1990) for this project, were originally examined only for the Globorotaliamemrdii complex to simply place the Pleistocene-Holocene boundary'. Later when it became critical to look at more detailed stratigraphy in these cores, additional counts were made of six species: Globorotalia crassaformis, Globorotalia inflata, Globorotalia truncatidinoides, Neogloboquadrina dutertrei, Globigerinoides sacculifer, and Globigerinoides ruber, and all other planktics were simply counted as a sixth category called 'other planktics'; this last category was necessary for calculating percentages. Frequency counts of 20-30 species, such as found in both of these studies, is very labor and time intensive, whereas the 'quick-counting method' used later in this study on the BPX cores was considerably more time efficient while providing the necessary information for the detailed zonation. Thus, this 'quick-counting method' is more feasible when the objective is simply biostratigraphy and the abundances of additional species are not required for other purposes. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Tabic con'd) sacculifer Inc. Inc. to mod. freq. Low-rare, or Freq. trough peak then dec. absent Steady dec. Low/rare to mod. Rare to low freq. Low-mod. freq. Low -mod. freq. Ireq. inc. to mod. Decreasing to Low-mod. freq. & dec. freq. G. G. Moderate freq. & freq. peaks Decreasing mod. freq. low-mod. freq. frequencies dutertrei freq. Inc. Inc. freq. Mod. Mod. to high freq. Dec. from high to Inc. Inc. low to mod. Mod. to high freq. peaks Inc. Inc. freq. & Low-mod. low freq. then inc. freq. & freq. peak freq. & & freq. peaks G. G. Decreasing mod. freq. Moderate freq. freq. peaks oblipuiloculata Highest freq. Rare to absent X-zone Rare to Low Low Low freq. peak Freq. trough freq. steady dec. nearbase, low freq. Increasing from Absent P. Absent Low -mod. 0 to mod. freq. ruber Inc. Inc. freq. Highest freq. in Dec. from Dec. freq. Low freq. Mod. freq. peak high freq. High High freq. Absent except High High freq. Low freq. peak then G. G. High High freq. Absent to a peak High High & dec. freq. High High & dec. freq. Ireq. menardii Highest freq. in X-zone Low Low to mod. freq. Mod. freq. peak Low Low freq. G. G. Absent Inc. Inc. from 0 Highest to mod. freq. freq. 1 2 8 Absent Steady inc. 1 Rare to absent Highest 3 1 6 Absent 7 5 Absent High freq. 24 Rare to absent High freq. Rare to absent Low freq. 3 Absent High freq. 2 auD Key Bio8tratigaphic Species Zones X Y z Table 7. Biostratigraphic Zonation Summary. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. low-mod. from Rare/low to absent Low Low to absent Freq. trough Inc. Inc. low to high G. G. crassaformis Mod. freq. Mod. freq. freq. freq. freq. then inc. freq. peaks freq. to 0 Species Key Biostratigaphic Low Low freq. peaks Low freq. peaks Mod. Mod. freq. G. G. falconensis peaks to low freq. peaks to low freq. freq. to 0 Rare to absent Rare to absent Rareto absent Low Low freq. peak Low freq. peak G. G. inflata Rare to absent Dec. to low-mod. freq. Dec. to low-mod. Low Low to mod. freq. Dec. from mod. freq. Low to mod. freq. high freq. Dec. from mod. freq.peak to rare-absent Mod. freq. & freq. peaks Inc. to mod. freq. & highest freq. in Y-zone highest freq. in Y-zone Rare to absent Dec. mod. freq. & freq. 1 1 2 Low to absent Low to absent 3 Rare/low to absent Rare/low to absent 1 Absent Dec. from low-mod. Dec. 7 Mod. to high freq. peaks 8 2 6 Mod. to high freq. & Mod. to high freq. & Low-rare to mod. 5 2 34 Mod. to high freq. Inc. from low to Mod. freq. Z ones X X Y Y Z Z Z o n e s S u b Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 G. inflata BPX-10 (1543 m) G. crassaformis N. dutertrei 10 20 30 40 10 20 30 0 Zl Z2 Z2 -Yl =Y1 Y2 Y2 200 - 200 Y3 Y3 Y4 Y4 400 - 400 O 600 - 600 800 - 800 1000 1000 0 10 20 30 40 0 2040 60 80 G. ruber G. sacculifer N. dutertrei G. menardii complex G. ruber Figure 14. Downcore plots of percent relative frequencies of six planktic foraminifera species used for biostratigraphic zonation of station BPX-10; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 G. in fla ta IG-45-15 G.falconensis (1692 m) H. aequilaterialis N. dutertrei 10 20 30 40 10 20 30 zi a Yl -Yl Y2 Y2 200 200 Y3 Y3 Y4 Y4 e Y5 Y5 « 400 400 £ Y6 Y6 a»a fi 'V Y7 Y7 « u 600 Y8 600 ^-^YS o XI XI y X2 X2 X3 800 - 800 X3 1000 1000 0 10 20 30 40 0 20 40 60 80 G. ruber G. menardii complex N. dutertrei G. sacculifer G. ruber P. obliquiloculata G. crassaformis Figure 15. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-45-15; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 G. inflata BPX-1 G. crassaformis (1815 m) N. dutertrei 10 20 30 40 10 20 30 0 Zl Z2 Z2 Y2 Y2 200 - 200 Y3 Y3 Y4 Y4 | 400 - 400 JZ 600 oh 600 - U 800 - 800 1000 1000 0 10 20 30 40 0 406020 80 G. ruber G. sacculifer N. dutertrei G. menardii complex G. ruber Figure 16. Downcore plots of percent relative frequencies of six planktic foraminifera species used for biostratigraphic zonation of station BPX-1; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 G. inflata IG-41-21 G. falconensis (2199 m) H. aequilaterialis N. dutertrei 0 10 20 30 40 10 20 30 0 200 200 S 400 400 Yl 600 600 Y2 Y2 Y3 Y3 800 800 Y4 Y4 Y5 YS Y6 Y6 1000 1000 0 10 20 30 40 0 20 40 60 80 ------G. menardii complex G. ruber ------G. sacculifer S. dutertrei ------p obliquiloculata G. ruber ...... G. crassaformis Figure 17. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-41-21; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. G. inflata IG-41-26 G. falconensis (2231m) H. aequilaterialis N. dutertrei 30 Z l Zl 200 - 200 S w 400 Z2 Z2 600 Y l 800 Y l 1000 1000 0 10 20 30 40 0 20 40 60 80 G. ruber ------G. sacculifer N. dutertrei ------p obliquiloculata G. ruber ...... G. crassaformis Figure 18. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station IG-41-26; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 G. inflata PC-1 G. falconensis (2905 m) H. aequilaterialis N. dutertrei zi 200 200 - Z2 Z2 N s Y l W 400 400 Yl Y2 Y2 «& Q o» oIm 600 - 600 - U 800 - 800 - 1000 1000 I 40 G. menardii complex G. ruber G. sacculifer N. dutertrei P. obliquiloculata G. ruber G. crassaformis Figure 19. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC1; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 4 G. inflata PC-4 G. falconensis (3550 m) H. aequilaterialis N. dutertrei zi 200 Z2 - 200 - Z2 Yl Yl Y2 £ 400- 400 - Y2 'w'w JB Y3 Y3 600- 600 - © Y4 Y4 800- 800 - 1000 1000 G. ruber G. menardii complex G. sacculifer ~ N. dutertrei P. obliquiloculata — G. ruber G. crassaformis Figure 20. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC4; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 G. inflata PC-2 G. falconensis (3632 m) H. aequilaterialis N. dutertrei 10 20 30 40 10 20 30 Zl ZL Z2 Yl Yl 200 200 Y2 Y2 s Y3 Y3 400- 400 - ©£ 600- 600 - V 800- 800 - 1000 “i ' i ' i—’ r 1000 0 10 20 30 40 0 20 40 60 80 G. ruber ------G. menardii complex ------G. sacculifer N. dutertrei ------P. obliquiloculata G. ruber ...... G. crassaformis Figure 21. Downcore plots of percent relative frequencies of nine planktic foraminifera species used for biostratigraphic zonation of station 89-G-10-PC2; * indicates a dissolution event Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 All cores with the exception of one, IG-45-15, contain only the Holocene (Z) and latest Pleistocene (Y) zones. Core IG-45-15, which contains the most complete stratigraphic record (Fig. 15), has sediments of the Holocene (Z) zone, the complete last glacial zone (Y) and the latest part of the last interglacial zone (X). Since there is no biostratigraphic evidence of unconformities in any of these cores, they appear to record continuous sedimentation, although the presence of undetectable discontinuities cannot be ruled out. The Kennett and Huddlestun (1972a) biostratigraphic zonal scheme provides a remarkably detailed stratigraphy and for the most part is readily recognizable in the cores of this study. There are, however, a few ambiguities in the Kennett and Huddlestun scheme and its original graphic depiction. For example, the lack of definitive subzonal boundary descriptions for the X-zone makes accurate recognition of the boundaries of each subzone difficult They provide only a brief description of notable faunal elements occurring within each zone with no indication of what to look for in bracketing these faunal patterns. In their illustration of these subzones as well as those of Z, Y and W, a subzone is indicated by a number in each core, but boundaries between subzones are unmarked. This labeling scheme is sufficient in the case of Z, Y and W zones where they provide a written description of how to recognize the boundaries between subzones, but is inadequate in the absence of such w'ritten descriptions as in the case of zone X. Finally, in their cores K-125, K-124, and K-120, a thick X zone is not subdivided into subzones as is the case with cores K-131, K-129 and K-127, and there is no explanation for this omission. For this study, a careful examination of Kennett and Huddlestun's Figure 3, which illustrates frequency oscillations of the important planktic species in the cores mentioned above, was used to define these subzonal boundaries. In the following section, a description of what was used to recognize the X3/X2 and X2/X1 boundaries in core IG-45-15 is included. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 Biostratigraphic Framework XZone This zone, found only in core IG-45-15, is characterized by moderate to high frequencies of the Globoroialia menardii complex and Neogloboquadrinadutertrei. Globorotaliainflcua, G. crassaformis and Globigerina falconensis are reduced to absent, whereas Pulleniatina obliquiloculata and Globigerinoidessacculifer exhibit low to moderate frequencies which are decreased from Zones Z and Y, respectively. Subzone X3 Only the upper portion of this subzone was penetrated by IG-45-15. This portion of X3 contains the highest frequencies of the Globoroialia menardii complex and Pulleniatina obliquiloculata of the X zone in this core, whereas Globoroialia inflata , Globoroialia crassaformis, Globigerina falconensis and Globigerinoides sacculifer are low to rare, or absent. Globigerinoides ruber and Neogloboquadrinadutertrei show steadily increasing frequencies. The upper boundary- is not well defined, but can be recognized by abrupt decreasing to low frequencies of the Globoroialia menardii complex and Pulleniatina obliquiloculata. Subzone X2 The Globorotalia menardii complex and Pulleniatina obliquiloculata exhibit consistently lower frequencies, low to moderate and rare to low respectively, than in subzone XI, whereas Neogloboquadrinadutertrei shows strong moderate to high frequencies. Globigerinoides sacculifer steadily increases to a moderate frequency peak within this subzone and then begins a steadily decline. Globorotalia inflata is absent until near the upper boundary where it reappears in low' frequencies. A notable feature of this subzone is the co-occurrence of three low to moderate frequency peaks above the base of X2, one each of the Globorotalia menardii complex, Neogloboquadrina dutertrei and Globorotalia crassaformis. Although Globigerinoides ruber decreases from a peak at the base of this subzone, it consistently maintains very high frequencies. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58 The upper boundary of this subzone is marked by increasing frequencies of the Globorotalia menardii complex and Neogloboquadrina dutertrei with a corresponding decrease in Globigerinoides ruber and Globigerinoides sacculifer. Subzone XI This subzone is characterized by moderate frequency peaks of the Globorotalia menardii complex and Neogloboquadrina dutertrei, whereas Pulleniatina obliquiloculata exhibits low frequencies. Globigerinoides sacculifer steadily decreases, and both Globorotalia inflata and Globorotalia crassaformis are rare to absent Globigerinoides ruber has decreased frequencies, up to 15% less than in the underlying X2 subzone and 35% less than in the overlying Y8 subzone. Globorotalia truncaiulinoides is almost 100% dextral throughout the entire X zone. X/Y Boundary This boundary is marked by the last consistent occurrence of the Globorotalia menardii complex. Neogloboquadrina dutertrei decreases. Globorotalia inflata, Globorotalia crassaformis and Globigerinoides sacculifer exhibit low frequencies, whereas Globigerinoides ruber shows marked increases. Globorotalia truncaiulinoides exhibits a slight change in coiling direction. Zone Y The Y zone is characterized by increased frequencies of Globorotalia inflata , Globigerina falconensis, both cool water species, and Globorotalia crassaformis, whereas the warm water species of the Globorotalia menardii complex and Pulleniatina obliquiloculata are decreased and/or absent. Neogloboquadrinadutertrei generally exhibits lower frequencies than in the Z zone except at three intervals where high frequency peaks occur. Globigerinoides ruber continues to occur at very high frequencies throughout the Y zone, whereas Globigerinoides sacculifer, like Neogloboquadrinadutertrei, exhibits wide frequency flucuations. Globorotalia Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59 truncattdinoides is dominantly right-coiling but does exhibit several sinestral peaks throughout the Y zone. Subzone Y8 This very narrow subzone is characterized by rare to low frequencies of most species. Globigerinoides sacculifer, Neogloboquadrinadutertrei, and Globorotalia crassaformis actually show frequency troughs, whereas Pulleniatina obliquiloculata , Globorotalia inflata and Globigerina falconensis exhibit small peaks. Globigerinoides ruber shows a steady increase in frequency to a peak near the Y8/Y7 boundary. The upper boundary is characterized by abrupt increases in Neogloboquadrinadutertrei, Globorotalia crassaformis and Globorotalia inflata. Subzone Y7 This subzone is characterized by marked fluctuations: a 35% decrease in Globigerinoides ruber, moderate to high peaks of both Globorotalia inflata and Neogloboquadrinadutertrei', and low frequency peaks of Globorotalia crassaformis, Pulleniatina obliquiloculata, and Globigerina falconensis. The Globorotalia menardii complex appears briefly at low frequencies in one sample in Y7 and Pulleniatina obliquiloculata begins to decline within this subzone. The upper boundary of this subzone is marked by increasing Globorotalia inflata w'ith corresponding decreasing frequencies of Neogloboquadrinadutertrei. This boundary' as well as that of Y8/Y7 is marked by a moderate pulse of left-coiling Globorotalia truncatulinoides. Subzone Y 6 Only one core, IG-45-15, contains this complete subzone, and core IG-41-21 contains only the upper portion. The most notable feature of this subzone is the complete disappearance of Pulleniatina obliquiloculata just above the lower boundary of Y6, after which it is virtually absent until the Holocene. Neogloboquadrinadutertrei abruptly decreases from high frequencies at the base to low frequencies then begins to increase steadily to the upper boundary'. Globorotalia crassaformis and Globigerinoides Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 0 sacculifer both show low or rare, to moderate frequencies and are absent in some parts of Y 6, whereas Globigerina falconensis and Globorotalia inflata exhibit moderate to high frequencies, form two frequency peaks within this subzone and reach their highest frequencies throughout the core. It is notable that the highest frequency peak of Globorotalia inflata coincides with the abrupt decline and disappearance of Pulleniatina obliquiloculata just above the base of Y6. The upper boundary of Y6 is marked by increasing frequencies of Neogloboquadrinadutertrei and simultaneous decreasing frequencies of Globigerinafalconensis and Globorotalia inflata. In IG-45-15, Globorotalia truncaiulinoides exhibits a weak pulse of left-coiling specimens similar to that at the Y4/Y5 boundary. Subzone Y 5 Globorotalia crassaformis, Globorotalia inflata and Globigerinoides sacculifer exhibit highly variable, low to moderate frequencies in cores IG-45-15 and IG-41-21. In contrast, Neogloboquadrinadutertrei exhibits a distinct increasing trend from low to moderate, and in one core, to high frequencies, forming a peak then decreasing toward the upper boundary. Globigerina falconensis decreases from a moderate frequency peak at the lower boundary to low frequencies at or near the upper boundary. The upper boundary is marked by increasing frequencies of both Globorotalia inflata and Globigerina falconensis as well as a trough of Globorotalia crassaformis. In core IG- 45- 15, Globorotalia truncaiulinoides exhibits a weak pulse of left-coiling specimens, whereas in IG-41-21 it is 100% right-coiling at this boundary and throughout the remainder of this core. Subzone Y4 This subzone was found in five of the eight cores, with the complete subzone present in only two of these. In most cases, Globorotalia crassaformis and Globorotalia inflata show frequencies increasing from low to high and often reaching a peak at the upper boundary-. Globigerinoides sacculifer and Neogloboquadrinadutertrei generally Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61 exhibit low to high frequencies, whereas Globigerinoides ruber continues to maintain high frequencies, 40-60%. Globigerinafalconensis shows variable moderate frequencies and usually reaches a frequency peak within this subzone. The upper boundary is characterized, in most cases, by decreasing Globorotalia inflata and increasing frequencies of Globigerinoides sacculifer. In all but two cores, Globorotalia truncatulinoides is characterized by a coiling change from right to left at the Y4/Y3 boundary. Subzone Y3 The Globorotalia menardii complex is absent. Pullentinia obliquiloculata is absent in Y3 in all cores except fora rare occurrence in IG-41-21. Globigerinoides ruber continues to maintain high frequencies, whereas Neogloboquadrinadutertrei and Globigerinoides sacculifer exhi bit low to moderate frequencies, with Globigerinoides sacculifer decreasing from a moderate frequency peak at or near the lower boundary. Globorotalia crassaformis and Globigerinafalconensis exhibit moderate, but variable frequencies often forming more than one frequency peak and trough. Globorotalia inflata shows moderate to high frequencies, usually increasing and peaking near the upper boundary, then decreasing into Y2. However, in two cores (IG-45-15 and IG- 41-21), it decreases from a high frequency peak at the base of this subzone. In most cases, the upper boundary of Y3 is recognized by an abrupt increase in Globigerinoides sacculifer , with an increase in or a peak of Globorotaliainflata and Globorotalia crassaformis , and Globorotalia truncatulinoides in all but one case is 100% right-coiling. Subzone Y2 The Globorotalia menardii complex and Pulleniatina obliquiloculata are rare to absent. Globorotalia crassaformis and Globigerinoides sacculifer exhibit an overall increasing trend toward moderate frequencies, often reaching a peak within this subzone and/or at the upper boundary, or both. Globigerinoides ruber continues to maintain Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62 high frequencies, between 40-60%, whereas Neogloboquadrinadutertrei drops to some of its lowest frequencies with an occassional moderate frequency peak. While generally maintaining moderate frequencies, Globigerinafalconensis also exhibits one or more moderate to high peaks within this subzone. In constrast, Globorotalia inflata, decreases from a moderate frequency peak at the base of this subzone to rare or even absent at the upper boundary, and through the remainder of the section. The upper boundary of Y2 is marked by the last consistent occurrence of Globorotalia inflata, an increase in Neogloboquadrinadutertrei, and a steady increase in or a frequency peak of Globigerinoides ruber. Globorotalia truncaiulinoides is generally 100% right-coiling at this boundary'. Subzone Y 1 There are several notable frequency shifts in this subzone. The warm-water species of the Globorotalia menardii complex and Pulleniatina obliquiloculata which characterize interglacial subzones with moderate to high frequencies are rare to absent in Y 1 in most cores. Globigerinoides ruber attains its highest frequency, between 70- 80%, in each core within this subzone. Also, in all but one core (IG-45-15), Neogloboquadrinadutertrei exhibits increasing frequencies; it too, often reaches a peak within this subzone. Although each of the following species often begins with a moderate to high frequency peak in the lower part of this subzone, Globorotalia crassaformis, Globigerina falconensis and Globigerinoides sacculifer generally exhibit from low’ to moderate frequencies; Globorotalia crassaformis and Globigerinoides sacculifer often increase or reach a peak at or near the upper boundary. Globorotalia inflata is absent, in most cores, to rare within this subzone. Subzone Y1-A (Kennett et al.. 1985) This subzone identified in two cores, EN32-PC-4 and PC6, from the Orca Basin by Kennett et al. (1985) is characterized by high frequencies of Globorotalia inflata, Hasterigerina aequilateralis and Globigerina falconensis, with lower frequencies of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63 Neogloboquadrinadutertrei. In cores from this study, Y I-A is not readily identified. Although there are consistently lower frequencies of Neogloboquadrinadutertrei, and in six of the cores, only a slight frequency increase in Hasterigerina aequilateralis (1-2%), there are no distinct frequency increases in Globorotalia inflata and Globigerina falconensis such as described by Kennett et al. (1985). Y/Z Boundary This boundary is recognized by the first consistent occurrence of the Gbborotalia menardii complex. Pulleniatina obliquiloculata reappears and/or begins a steady increase in frequency, whereas Globigerinoides ruber generally begins to decrease, although it still maintains very high frequencies. In addition, Globorotalia crassaformis begins to increase from low to moderate frequencies at the Y/Z boundary and Globigerinoides sacculifer generally exhibits increasing frequencies. Also, there is a spike of left-coiling Globorotaliatruncatulinoides at or just above the Y/Z boundary. ZoneZ This zone is characterized by high frequencies of warm-water species such as the Globorotalia menardii complex and Pulleniatina obliquiloculata. High frequencies of Globigernioides ruber and moderate frequencies of Globigerinoides sacculifer, and Globorotalia crassaformis are also common. Frequencies of cool-water species such as Globorotaliainflata and Globigerina falconensis are low in this zone. Globorotalia truncaiulinoides is dominantly right-coiling throughout this zone, although there is at least one and often two left-coiling spikes most commonly at or near a subzonal or zonal boundary. Subzone Z2 This subzone is characterized by steadily increasing, from 0 to 5-10%, frequencies of the Globorotalia menardii complex and Pulleniatina obliquiloculata, steadily decreasing frequencies of Globigerinoides ruber, and consistently moderate frequencies of Globorotalia crassaformis and Globigerinoides sacculifer, both of which often exhibit Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 4 a distinct frequency peak within this subzone. Neogloboquadrinadutertrei also exhibits moderate frequencies and generally reaches a frequency peak within or at the upper boundary of this subzone. Globorotaliainflata is rare to absent, whereas Globigerina falconensis decreases from moderate frequencies or a frequency peak at the Y1/Z2 boundary to low frequencies. The upper boundary of subzone Z2 is marked by the abrupt decrease and disappearance of Globorotalia crassaformis and an abrupt change in coiling direction from right to left in Globorotalia truncaiulinoides. Subzone Z1 This subzone is characterized by the highest frequencies, to 20%, of the Globorotalia menardii complex and Pulleniatina obliquiloculata in each core, consistently high, yet generally decreasing, frequencies of Globigerinoides ruber, and moderate to decreasing frequencies of Neogloboquadrinadutertrei and Globigerinoides sacculifer. Globorotalia crassaformis and Globigerina falconensis generally decrease from moderate and low frequencies to being rare to absent. Globorotalia inflata is absent with the exception of a single sample in core IG-41-26. Late Quaternary Planktic Foraminiferal Variations In addition to the six species used to recognize zonal and subzonal boundaries for the biostratigraphic framework, frequency variations of four other abundant and climatically-sensitive species of planktic foraminifera are discussed below. These ten species (Plate 1) are reported from six cores, but not from the two BPX cores that were examined as part of an earlier pilot study (Jones, 1990). Faunal variations are discussed within the stratigraphic framework described above (Figs. 14-21). Relative Frequencies The most striking faunal change is that for the warm-water species of the Globorotalia menardii complex at the Pleistocene-Holocene boundary’. The Globorotalia menardii complex is mostly absent throughout the last glacial interval (Y zone) in all ten cores, and in the Holocene (Z zone) frequencies gradually increase from Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PLATE 1. Planktic Fbraminifera. 1,2) Globorotalia crassaformis 150/*, 180//; 3) Neogloboquadrina sp. cf. N. pachyderma 250p; 4 ) G. inflata 190//; 5,6) G. truncatulinoides 150//, 150//; 7, 8) Neogloboquadrina dutertrei 180//, 190//; 9) Globorotalia menardii 70//; 10, 11) Globigerina falconensis 250//, 270// 12,13) Globigerinoides ruber 200//, 170//; 14,15) G. sacculifer 110//, 140//; 16, 17) Hasterigerina aequilateralis 170//, 200//. All scale bars equal 100//. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67 0-1% at the Pleistocene-Holocene boundary’ to 20% in the latest Holocene. In core IG- 45-15, the Globorotalia menardii complex decreases from 20% in subzone X3 to < 3% near the X-Y boundary. Pulleniatina obliquiloculata , another warm-water species, is rare to absent during the latest Pleistocene, except in core IG-41-21 (Fig. 17) where it exhibits minor, erratic fluctuations through subzones Y3 to Y lwith frequencies to -4%. Frequencies of P. obliquiloculata steadily increase from the Y-Z boundary and reach their maximum frequencies, 25-40%, in the latest Holocene, subzone Zl. From the last interglacial subzone X3 to half-way through glacial subzone Y6, -40 kv (Damuth, 1973; Damuth and Kumar, 1975), frequencies of P. obliquiloculata decline from 8 to 0%, reflecting climatic deterioration into the glacial Y zone. The most dominant constituent of the planktic foraminiferal assemblage throughout the latest Quaternary is Globigerinoides ruber. The consistently high frequencies (> 40%) of this species through both glacial and interglacial intervals suggest that it can tolerate a wide range of surface water temperatures. In five cores, a distinct frequency peak (nearly 80%) occurs within the Y 1 subzone, whereas in the remaining three cores the same peak straddles the Y-Z boundary (Fig. 22). Above this Y1 peak and into the Holocene, frequencies of Globigerinoides ruber decreases slightly, but is still very high. In all cores but the two with the most complete strati graphic coverage (IG-45-15, IG-41-21; Figs. 15 and 17), Neogloboquadrinadutertrei is most abundant (10-20%) in the latest Pleistocene (Y 1) and the Holocene sections, whereas frequencies in older (glacial) sections are generally < 5%. Frequency peaks reaching 9 to 18% occur in the glacial Y1 subzone in six cores, but in two cores (IG-45-15, BPX-10) there is no such peak (Fig. 23). In cores IG-45-15 and IG-41-21. Neogloboquadrinadutertrei exhibits additional frequency peaks (10-20%) in Y3, Y4 and Y5 subzones. Neogloboquadrina dutertrei also shows high frequencies (10-20%) throughout the later part of the last interglacial (Zone X) in core IG-45-15. The persistence of these high frequencies in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 Globigerinoides ruber BPX-10 IG-45-15 BPX-1 IG-41-21 20 40 (0 80 0 20 40 60 80 0 20 40 60 80 0 20 40 60 80 Z1 ______7.5 ZL -H- 22. 2 2 Y2 -¥t- ? / 200 Y2 Y2 Y3 { Y3 Y3 Y4 *s S Y* Y4 -L. Y5 400 Z2 Y6 Y1 > ^ Y7 600- _ ia_ r - — XI Y2 X2 Y3 800- X3 Y4 Y5 Y6 1543 m 1692 m 1815 m 2199 m 1000 0 500 1000 1500 0 500 1000 1500 500 1000 1500 0 500 1000 1500 IG-41-26 PC-1 PC-4 PC-2 0 20 40 60 80 20 40 60 80 20 40 60 80 20 40 60 80 Z1 Z1 Z1 Z2 Z1 2 0 0 - Z2 Y1 Y2 12 Y1 Y3 Y1400 Y2 Z2 Y2 600 Y3 Y4 800- Y1 1000 2905 m 3550 m 3632 m 0 500 1000 1500 0 500 1000 1500 Figure 22. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globigerinoides ruber, percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Note the largest relative frequency peak in the meltwater interval, subzone Yl. Water depth for each station is shown in lower left comer of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 Neogloboquadrina dutertrei BPX-10 IG-45-15 BPX-1 IG-41-21 0 10 20 30 0 10 20 30 zi Z2 Y2 Y2 200 Y3 Y3 Y3 Y4 Y4 Y4 Y5 400- Z2 Y6 Y7 Y1 JO. 600- Y2 X2 Y3 X3 800- Y4 Y5 1543 m 1692 m 1815 m 2199 m Y6 1000 300 0 100 200 300 300 0 100 200 300 IG-41-26 PC-1 PC-4 PC-2 0 10 20 30 10 20 30 10 20 30 10 20 30 Zl Zl Z l Zl 200 Z2 Y1 Y2 Z2 400 Y1 Y2 Y3 Y2 Z2 Y3 600 Y4 Y1 2905 m 3632 m 1000 2231 m 0 100 200 300 0 100 200 300 0 100 200 300 0 100 200 300 Figure 23. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Neogloboquadrinadutertrei: percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Note the largest frequency peak in the early Holocene, subzone Z2. Water depth for each station is shown in lower right comer of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70 interglacial intervals is consistent with the report that Neogloboquadrinadutertrei is a marginally warm-water species (Kennett et al, 1985; Flower and Kennett, 1990). Globigerinoides sacculifer is a consistent element (2-10%) throughout the entire latest Quaternary in the northwestern Gulf. It exhibits slightly lower frequencies during the last glacial with the exception of several frequency peaks, to 15-30%, which are consistent from core to core in the Y2, Y3, Y4 subzones. Several frequency peaks are also present in the interglacial subzones X2, Zl and Z2 (Fig. 24). Globorotalia truncatulinoides exhibits its highest frequencies, 10-20%, in interglacial intervals X and Z. Late Pleistocene Zone Y frequencies do not exceed 10% except in one case, subzone Y6, which may reflect the onset of full-glacial conditions and this is consistent with the disappearance of Pulleniatina obliquiloculata which occurs at this time as well (Fig. 25). Globorotalia crassaformis , reportedly a marginally-cool water species in the Gulf (Kennett and Huddlestun, 1972a; Malmgren and Kennett, 1976; Kennett etal., 1985; Flower and Kennett, 1990), consistently exhibits moderate frequencies, 5-8%, with several high frequency peaks, sometimes to over 20%, throughout the latest Pleistocene (Zone Y) and the earliest Holocene (Z2). In the latest Holocene, subzone Zl, Globorotalia crassaformis is absent in most cores, however in IG-41-21 and PC-1 there are isolated frequency peaks, one to greater than 15%. In core IG-45-15, the frequency of Globorotalia crassaformis decreases steadily from the base of interglacial subzone X2 to the X/Y boundary7, at which point it begins to increase. Low to moderate frequencies (<5%) of Hasterigerina aequilateralis are prevalent throughout both glacial and interglacial interv als. Frequency peaks of 10-15% occur in only two cores, IG-41-26 in the latest Holocene and PC-2 in glacial subzones Y2 and Y3 (Fig. 26). The species has been considered as a marginally-cool water species in the Gulf (Malmgren and Kennett, 1976; Kennett et al., 1985; Flower and Kennett, 1990), but this interpretation is not substantiated by the data from this study. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71 Globigerinoides sacculifer BPX-10 IG-45-15 BPX-1 IG-41-21 0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 Zl ZL Z2. Z2 Y2 JX Y2 Y2 Z l 2 0 0 - Y3 Y3 Y3 Y4 Y4 YS 4 0 0 - Z2 Y6 Y7 Y1 6 0 0 - Y2 X2 Y3 X3 8 0 0 - Y4 Y5 1543 m 1692 m 2139 m Y6 1000 0 100 200 300 0 100 200 300 0 100 200 300 IG-41-26 PC-1 PC-4 PC-2 0 10 20 30 40 10 20 30 40 0 10 20 30 40 0 10 20 30 40 Zl 200 - Z2 Yl Y2 Z2 400- Yl Y2 Y3 Z2 Y2 Y3 600- Y4 Yl 2231 m 3350 m 3632 m 1000 0 100 200 300 0 100 200 300 0 100 200 300 0 100 200 300 Figure 24. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globigerinioides sacculifer percentages (solid curve and bottom scale) and number of foraminifera7 g sediment (dashed curve and top scale), respectively. Water depth for each station is shown in lower right corner of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Globorotalia truncatulinoides IG-45-15 IG-41-21 IG-41-26 0 50 100 150 200 0 20 40 60 80 0 100 200 Z2 YI- Y2 Z l 20 0 - 2 0 0 - 200 Y3 s Y4 400 Y5 400- Z2 Y6 Bi Z2 o Y7 Yl ® 600- VK 600-. 600- Y2 © U X2 Y3 800- X3 800- Y4 800 Y5 Yl 1692 m2199 m Y6 2231m 1000 1000 1000 00 10 20 30 0 10 20 30 PC-1 PC-4 PC-2 0 20 40 60 80 0 20 40 60 80 0 20 40 60 80 Zl Yl 2 0 0 - 2 0 0 - Z2 200 Y2 Yl Z2 Y3 Yl 400- Y2 400- Y2 Y3 600- 600- 600- Y4 800- 800- 800- 2905 m 3550 m 3632 m 1000 1000 1000 0 10 20 30 0 10 20 30 0 10 20 30 Figure 25. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globorotalia truncaiulinoides percentages (solid curve and bottom scale) and number of foraminifera/ g sediment (dashed curve and top scale), respectively. Water depth for each station is shown in lower right comer of plot Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hastigerina aequilateralis IG-45-15 IG-41-21 IG-41-26 0 20 40 60 80 0 5 10 IS 20 0 20 40 60 80 I . I ■ I ■ I 21 Z2 ■Yl—1 Y2 Zl 200 - 200 2 0 0 - Y3 Y4 400 Y5 400 Z2 400 a Y6 w Y l o Y7 Y « 600 600 600 u XI o Y2 u X2 • V " 2 , Y3 800- X3 800- Y4 800 Y5 1692 m 2199 m Y6 2231m 1000 1000 1000 10 10 5 10 IS 20 PC-1 PC-4 PC-2 0 5 10 IS 20 0 5 10 IS 20 0 5 10 15 20 0- 0- V .i: . Zl Zl IT 1* Zl 1 7,2 200- 200- 1 ' Z2 Mn. Yl F v* "*** Yl V Y2 Z2 E w 400- Yl 400- Y2 400- Y3 'y Y2 oa Y3 fi 600- 600- 600- uV 9 U Y4 800- 800- 800- 2905 m 3550 m 3632 m 1000- 1000- ... ,- innn. 10 0 5 10 IS 20 10 Figure 26. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Hasterigerinaaequilaterialis: percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Water depth for each station is shown in lower right comer of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74 Frequencies of the cool water-species Globigerinafalconensis consistently range from 5 to 10%, with occasional frequency peaks from 10 to >20%, throughout glacial intervals (Fig. 27). Frequency peaks occur in glacial subzones Y 1, Y2, Y3, Y4 and Y6, often these peaks straddle subzonal boundaries. Frequencies above 5% are rare in interglacial subzones, and decrease steadily from the Y/Z boundary with the lowest frequencies occurring in the latest Holocene (Zl). Globorotalia inflata, another cool-water species, is generally absent during interglacial intervals and is rare to absent in glacial subzone Y 1. Late Pleistocene frequencies of Globorotalia inflata range from 5-10%, with frequency peaks attaining their highest values (to >20%) in subzone Y3 in four cores. In core IG-45-15, highest frequencies of Globorotalia inflata occur in subzone Y6 (Fig. 28). Absolute Frequencies Absolute frequencies were examined for several planktic species, and for total planktics to evaluate population variations that: 1) are related to meltw'ater influx, 2) reflect surface-water temperatures and, 3) may reflect surface-water productivity changes. Although the absolute frequency of Globigerinoides ruber exhibits little variation throughout the latest Pleistocene (Fig. 22), a steady increase begins in most cores within the Y2 or Y 1 subzone, reaching a frequency peak in the Z2 subzone. Overall, the highest absolute frequencies of Globigerinoides ruber (to ~1500 G. ruber /g sediment) occur in the Holocene. In core IG-45-15, how'ever, a large frequency peak is also seen in the interglacial X zone. In this core, frequencies of Globigerinoides ruber fluctuate throughout the early glacial Y zone, but never attain frequencies greater than 500 G. ruber /g sediment In only one core, IG-45-15, is there a distinct frequency peak within the Y 1 subzone. Downcore plots of absolute frequencies of Globigerinoides ruber and total planktics minus Globigerinoides ruber show' that the tw'o curves generally coincide because Globigerinoides ruber usually makes up almost half of the total assemblage. An exception is found w'ithin the Y 1 interval, where the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Globigerina falconensis IG-45-15 IG-41-21 IG-41-26 0 50 100 150 200 0 20 40 60 80 21 0 20 40 60 80 Z2 Z l Zl 200 200- 200- Y3 Y4 Y5 « 400 400- Z2 400 Y6 Y7 Yl Z2 600 XI 600 600 Y2 X2 Y3 800- X3 800 Y4 800- Y5 Y l 1692 m Y6 2231m 1000 1000 1000 0 5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 PC-4 PC-1 PC-2 Z l zi 200 200- Z2 200 Y1 Y l Y2 Z2 su 400 400- Y1 Y2 400- Y3 JC 2905 m 1000 3632 m 1000 1000 0 5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 Figure 27. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globigerina falconensis percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Water depth for each station is shown in lower right comer of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76 Globorotalia inflata BPX-10 IG-45-15 BPX-l 41-21 50 0 50 100 200 0 50 100 150 200 10 20 30 40 50 71 L i { * ■ —i—._ j . j - i . Zl Z2 Zl 7,? Z2 -vt- Yl Y2 Y2 Z l 200 - Y3 Y3 Y3 Y4 ——. Y4 Y5 400- - - Z2 Y6 Y7 Yl VK v Y2 X2 Y3 800- X3 - - V' Y4 Y5 1543 m 1692 m 1815 m 2199 m Y6 1000 T— ■ 1 ■ ---- 1— - ■ -I 1 i ■ ■■ 10 20 30 10 20 30 10 20 30 10 20 30 IG-41-26 PC-1 PC-4 PC-2 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 ■ ■ i i i Zl Zl Zl Z2_ Zl XL 20 0 - Z2 Yl Y2 Z2 c ; Y3 400 Yl Y2 Z2 Y2 Y3 Y4 Yl 2231m 2905 m 3662 m 1000 i ■' "i ■ i 1 i ■' 30 0 10 20 30 0 0 10 20 30 40 50 Figure 28. Downcore plots of late Pleistocene and Holocene relative and absolute frequencies of Globorotalia inflata percentages (solid curve and top scale) and number of foraminifera/ g sediment (dashed curve and bottom scale), respectively. Water depth for each station is shown in lower right comer of plot. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Globigerinoides ruber curve deviates by a small increase, and in the early to middle Holocene where the Globigerinoides ruber curve shows a marked decrease in several of the cores (Fig. 29). Absolute frequencies of Neogloboquadrinadutertrei (Fig. 23) are consistently an order of magnitude lower than those of Globigerinoides ruber. Despite this major difference, the pattern of absolute frequency of Neogloboquadrinadutertrei mimics very closely that of Globigerinoides ruber (Figs. 22 and 29), exhibiting little variation within the latest Pleistocene and then increasing slightly to frequency peaks in the 72 subzone. Similarly, in IG-45-15, both species exhibit a large frequency peak in interglacial zone X with some fluctuations throughout the lower and middle Y zone Planktic foraminiferal populations (# total planktic foraminifera I g sediment) are generally low (0-500 foraminifera / g sediment) throughout the glacial Y zone (Fig. 30), however, there are small peaks within the Y2 subzone in several cores. A steady increase in planktic populations begins within the Y1 subzone, reaching a maximum in the early to middle Holocene, except in core IG-45-15, where total planktic foraminieral number reaches its maximum in the latest interglacial X2 subzone (almost 3000 foraminifera / g sediment). Total planktic foraminifera generally decrease throughout the latest Holocene. Factor Analysis A Q-mode factor analysis was performed on the downcore relative frequency data of sixteen species (variables) for six cores. The varimax factor analysis revealed three factors that account for 95% of the variance. Varimax rotation, used to facilitate interpretation, redistributes the variance across the factors retained. This repartitioning of the variance often produces factors w’hich resemble end-member assemblages (Brunner, 1979). Species used in the analysis had frequencies of >2% in at least three samples. Factor scores were used to identify faunal assemblages (Table 8). Factor Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 Total Planktonics minus G. ruber & Absolute G. ruber (# foraminifera / g sed) BPX-10 IG-45-15 BPX-i IG-41-21 0 1000 2000 0 1000 2000 q 1000 2000 0 500 1000 0 Zl Z2 -¥*- Y2 200 Y2 Y2 Y3 Y3 Y3 Y4 Y5 Y4 400 Z2 Y6 Y7 Yl <00 Y2 X2 Y3 X3 800 Y4 Y5 1543 m1692 m 1815 m 2199 m Y6 1000 1000 2000 0 1000 2000 o 2000 0 500 10001000 IG-41-26 PC-4 PC-1 PC-2 1000 2000 500 1000 0 500 1000 500 1000 0 1_ Zl } Zl Zl *■’ —i^T * 72 Zl Yl 200 Z2 Yl Y2 Z2 > Y3 400 4 Yl Y2 Z2 Y3 600 m * > Y4 \ . 800 - p Yl 3632 m 2231m 3550 m 2905 m ------,------1000 - ■ ' i ------1000 2000 500 1000 0 500 1000 500 1000 Figure 29. Downcore absolute frequency plots of total planktic foraminifera minus G. ruber and of G. ruber (number of foraminifera/ g sediment; solid curve and dashed curve, respectively) showing larger frequencies of G. ruber than total planktics in Y 1 mel twater interval. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79 Total Planktic Foraminifera (#/g sed) BPX-10 IG-45-15 BPX-1 IG-41-21 1000 2000 3000 1000 2000 3000 1000 2000 3000 1000 2000 3000 - 1 ___1 . . Z2 ZL Z l 22. Z2 Y2 JO. Z l Y2 Y2 200 - Y3 Y3 Y3 Y4 Y4 Y4 YS 400- Z2 Y 6 Y l Y7 600- jm. 1 Y2 > X2 Y3 800- X3 - Y4 Y5 1 1692 m1543 m 1692 m1543 1815 m 2139 m Y6 1000 IG-41-26 PC-1 PC-4 PC-2 2000 4000 0 1000 2000 3000 1000 2000 3000 1000 2000 3000 Z l Z l 200 - Z2 Y l Y2 Z2 Y3 400- Y l Y2 Z2 Y2 Y3 600 Y4 800 Yl 2231 m 2905 m 3350 m 3632 m 1000 Figure 30. Downcore plots of absolute frequency of total planktic foraminifera (number of foraminifera/ g sediment) showing increase beginning latest Pleistocene with highest absolute frequencies occurring in Holocene Z zones. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80 Table 8. Factor Scores for Species of Planktic Foraminifera. Scores in bold considered significant for interpretation of factors. Species Factor 1 Factor 2 Factor 3 Globorotalia menardii -0 .8 9 5 3 4 1.38928 -0.22279 Pulleniatina obliquiloculata -0.90489 2.06162 -0 .7 6 3 7 7 Globigerinoides sacculifer -1 .1 3 7 8 4 -0.70559 2 .7 2 1 5 4 Neogloboquadrina dutertrei -0 .8 5 0 5 4 0.10030 1 .5 1 8 5 5 Globigerinoides ruber 3.06750 1.49153 1.41781 Globorotalia inflata 0.75855 -0.83765 -1.01429 Orbulina universa 0.07312 -0.14003 -0.36259 Globorotalia crassaformis 0.69608 -0.89235 -0.49608 Globigerina falconensis 0.61594 -0.83347 -0.51865 Hasterigerina aequilateralis 0.05095 -0.49657 -0.38980 Globigerina bulloides -0.11239 -0.55469 -0.29924 Globorotalia truncatulinoides (R) -0.11239 -0.55469 -0 .7 0 6 1 7 Globigerinella calida -0.11375 -0.49873 -0.06888 Beella digitata -0.20762 -0.61431 -0.25697 Globorotalia scitula -0.19243 -0.61615 -0.24991 Globigerinoides conglobatus -0.28237 -0.33687 -0.30876 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81 loadings for the three factors were plotted versus core depth to provide a means to examine temporal assemblage variations. Factor 1 accounts for 49% of the variance. Globigerinoides ruber exhibits a high positive score on this factor, whereas Globigerinoides sacculifer show's the most negative score. Since both of these species, Globigerinoides ruber in particular, exhibit low resistance to dissolution (Be, 1977) another parameter must be dominating the overall signal exhibited by this factor. Since both Globigerinoides ruber and Globigerinoides sacculifer have similar temperature and salinity optima (Hemleben, 1989; Bijma et al., 1990), the strongly opposing scores they exhibit (Table 8) may suggest that this factor reflects surface-water fertility. Globigerinoides ruber has been reported to dominate surface waters rich in nutrients whereas Globigerinoides sacculifer has been associated often with nutrient-depleted surface waters (Halicz and Reiss, 1981; Deuser et al., 1988; Bijma, 1990). Downcore plots of Factor 1 loadings (Fig. 31) most strongly reflect assemblage variations related to surface-water nutrient levels, however, a record of carbonate dissolution overprinting the nutrient signal may be exhibited by the sharp negative excursions. This dissolution signal (on factor 1) may be useful as an indicator of bottom-water corrosivity. Factor 2 accounts for 25% of the variance. Species that have high positive scores on factor 2 include: Globigerinoides ruber, Pulleniatina obliquiloculata, Globorotalia menardii, all warm-water species, and Globorotaliatruncatulinoides (r). Those with high negative scores are Globorotalia inflaia, Globorotalia crassaformis, Globigerina falconensis, and Globigerinoides sacculifer. Globorotalia inflata and Globigerina falconensis are typical cooMvater species (Kennett and Huddlestun, 1972a) and Globorotalia crassaformis is a marginally cool-water species (Kennett et al., 1985). Downcore plots of Factor 2 loadings (Fig. 32) reflect fluctuations between warm- and cool-water assemblages recording a distinct surface-water temperature signal. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oo to Y2 Y3 0.5 PC-2 Factor I -0.5 Y2 Z2 Y3 Y4 0.5 PC-4 Factor I ■0.5•0.5 Y2 0.5 PC-1 Factor 1 Z1 Z2 Yl 0.5 Fnctor 1 1G-41-26 -0.5 Yl Y4 Y2 Y5 Y3 Y6 Z2 0.5 Factor 1 IG-41-21 •0.5 Surface-Water Nutrients/Bottom-Water Corrosivity Y l- Y6 Y5 Y3 Y7 X3 X2 Y2 0.5 Factor 1 IG-45-15 •0.5 - 200 400 600 800 1000 Figure31. Downcore plots ofFactor loadings with 1 more positiveproductivity loadings, assemblage, reflecting in Y glacial influencezones. ofincreased Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8S Y2 Y3 0.5 1 PC-2 Factor2 Y2 Y3 Z2 Yl Y4 2 0.5 PC-4 Factor Yl Zl Y2 0.5 PC-1 Factor 2 Zl 0.5 Factor 2 IG-41-26 Surface-Water Temperature Yt Y4 Zl Y2 Y3 Y5 Z2 Y6 0.5 Factor 2 IG-41-21 Y4 Y3 Y7 Y5 Y6 X2 X3 0.5 Factor 2 1G-45-15 Figure 32. Downcore plotsof Factor 2 loadings with more negative loadings, reflecting influence ofcool-water 200 600- 400 assemblage, in glacial Y zones. 1000 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 Z2. Y2 Y3 PC-2 Factor 3 -0.5 0 0.5 1 Zl Y2 Y3 Yl Y4 PC-4 Factor 3 0 0.5 -0.5 rencc,i"8ofstenofopic Factor 3 0.5 Factor 3 IG-41-26 Surface-Water Stability Yl Z l Y4 Y2 Z2 Y3 VS Y6 0.5 <■ \ < * Factor 3 < IG-41-21 > Y0zon°esFaC'0r3 Y0zon°esFaC'0r3 Wi"’ “ *“ iveloadin8s’ Yrt XI Zl Y l- Y4~ Y5 Y6 Y7 Y3 X2 X3 Y2 0.5 r* v. f J < Factor3 IG-45-15 800 200 400 600 1000 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85 Factor 3 accounts for 21% of the variance. Globigerinoides ruber, Globigerinoides sacculifer and Neogloboquadrinadutertrei have high positive scores on factor 3 and Globorotalia inflata, Globorotalia truncatulinoides and Pulleniazina obliquiloculata exhibit the most negative scores. Globigerinoides ruber, Globigerinoides sacculifer and Neogloboquadrinadutertrei ait several of the most euiytopic species (Bijma et al., 1990), whereas the negatively scored species are much more stenotopic. Downcore plots of Factor 3 loadings (Fig. 33), then, reflect oscillations between a more eurytopic assemblage and a stenotopic, or more seasonally-influenced assemblage, possibly indicating climatic transition and/or changing patterns of seasonality, which may reflect the stability of surface-water environments. Discussion and Summary Foraminiferal Signal of Meltwater Influx Results from this study confirm the presence of glacial meltwater as far as 500 km south of the present-day shoreline of the northwestern Gulf of Mexico. In many past studies, this meltwater signal has been recognized in Gulf cores by a negative oxygen- isotope shift (Kennett and Shackleton, 1975; Leventeretal., 1982,1983; Kennett etal., 1985). In the present investigation, the tool for recognition of the meltwater signal is Globigerinoides ruber and Neogloboquadrina dutertrei relative frequency peaks. These planktic foraminiferal data, from seven of the eight cores, do not support the conclusion from earlier studies that the frequency of Globigerinoides ruber would decrease significantly between the northern and central Gulf during a meltwater event, and that the frequency of Neogloboquadrinadutertrei, a deeper-dwelling species would increase (Kennett et al., 1985). The relative frequency increase of Neogloboquadrinadutertrei remains more or less the same throughout the study area (5-12%; Fig. 34), including these central Gulf stations and the Orca Basin cores (8 and 9%; Kennett et al., 1985), except in BPX-10, which shows no increase. In the southwestern Gulf, Neogloboquadrinadutertrei Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 AREA 1 AREA 2 na/,70 AREA 3 25( W / \ n 3 4 /1 2 91 "■* Figure 34. Map with station locations showing the relative frequency increases of Globigerinoides ruber (bold) and Neogloboquadrinadutertrei (italic) within the meltwater interval (Y1); na indicates no data. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 87 frequency increases are more variable (6-20%), increase basinward and, at all but two stations (TR 126-25,26; 16% and 20% respectively, Thunell, 1976), show frequency increases comparable (6-10%) to data of this study. Also, the most basinward station of Thunell (1976) shows one of the lowest frequency increases (7%). Overall, Neogloboquadrinadutertrei frequency increases during the Y 1 meltwater interval are relatively uniform throughout the entire western Gulf. Although the influx of meltwater during the Y 1 subzone had only a small effect on the absolute frequencies of Globigerinoides ruber and Neogloboquadrinadutertrei , there is a trend of increase, generally beginning in the Y 1 subzone and culminating in a peak in the Holocene Z2 subzone. Globigerinoides ruber populations also exhibit a small increase over the total planktic population in the Y 1 subzone in response to the influx of cool, less saline meltwater at this time. In addition, absolute frequencies are consistently the highest in the Holocene, except in core IG-45-15 where frequencies of both species increase in the latest interglacial X zone, reach a peak at the X2/X1 boundary, and then decline in the postglacial Z zone. For Globigerinoides ruber, the absolute frequency peak lags behind the relative frequency peak (Fig. 22) in all but two cores (IG-41-21, IG-41-26), whereas for Neogloboquadrinadutertrei , the two peaks coincide in all but two cores (Zl peak in PC-1 and Y1 peak in PC-4; see Fig. 23). Arguably, the decline of other planktic species during the Y1 meltwater event lasted long enough for the populations of Globigerinoides ruber to increase, reaching a peak in the early Holocene. With the onset of more equitable conditions and the population increase in other species, Globigerinoides ruber populations declined. In contrast, both absolute and relative frequency peaks of Neogloboquadrinadutertrei occur in the early Holocene rather than in the meltwater interval (Y 1). These trends and the distribution of other planktic foraminifera support the idea that the dominance of Globigerinoides ruber reached a very high level in the Y1 subzone because other species were unable to proliferate under meltwater temperature and salinity conditions (Kennett et al., 1985). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88 Temporal Variations in Nutrient Levels Low temperature and salinity conditions may not be the only aspect of glacial meltwater effecting planktic foraminiferal distributions. Nutrient levels in meltwater outflow, which would be higher simply by virtue of large discharge volumes and a reduced Gulf basin, could be a contributing factor in determining which species flourish. Bjima et al. (1990) argue that salinity variations may not be the only factor controlling Globigerinoides ruber and Globigerinoides sacculifer distributions since both have been documented to tolerate extreme salinity conditions, and have been shown to have similar salinity optimums. Furthermore, they summarize two studies that suggest Globigerinoides ruber has an affinity' for high-productivity surface waters (Haliczand Reiss, 1981; Deuser etal., 1988). Near Barbados, Globigerinoides ruber dominates nutrient-enriched, freshwater lenses, which originate from the Amazon River (Deuser et al., 1988). In the Red Sea, Globigerinoides ruber was reported to dominate the more nutrient-enriched surface waters of the south, whereas Globigerinoides sacculifer was most abundant in the oligotrophic northern surface waters (Bijma et al., 1990). In addition to the reduced salinities of glacial meltwater, enhanced nutrient levels may then accentuate the proliferation of Globigerinoides ruber over other planktic species, such as Globigerinoides sacculifer. which has decreased frequencies within the Y 1 meltwater interval (Figs. 14-21; 24). Late Quaternary increases in total planktic population begin within the Y 1 meltwater interval and continue into the early to middle Holocene. The timing of these increases in planktic populations supports the idea that surface-water nutrient levels increased with the inflax of nutrient-rich meltwater. In most cores (BPX-1, IG-451-5, IG-41-21, PC- 1, PC-2, PC-4), low relative frequencies of Globigerinoides sacculifer, which prefers more nutrient-depleted surface-waters (Deuser et al., 1988; Bijma et al., 1990), co occur with high relative frequencies of Globigerinoides ruber in the Y1 meltwater interval (Figs. 14-21). Since these two species have been shown to have the same Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89 salinity optimum (Bijma et al., 1990), the proliferation of Globigerinoides ruber over Globigerinoides sacculifer may be linked to increased surface-water nutrient levels as a result of meltwater influx. The downcore plots of factor 1 loadings show an increased influence of the Globigerinoides ruber-domimted assemblage, often associated with nutrient-enriched surface-waters, during the glacial Y interval, and a diminished influence of this assemblage in interglacial X and Z intervals (Fig. 31). However, these nutrient- enriched surface-waters apparently did not yield significantly increased surface-water productivity in the glacial Y-zone, although the Y l interval is an exception. Total planktic foraminiferal populations, which are often used to reflect increased surface- water productivity, were at their lowest during this full-glacial interval (Fig. 30), indicating no increase in surface-water productivity at this time. On a global scale, increased productivity levels have been widely reported for the last glacial from major ocean basins (Pedersen, 1983; Pedersen, et al., 1988; Samthein, et al., 1988; Herguera, et al., 1991). However, Thomas et al. (1995) reported evidence of decreased surface-water productivity in high latitudes of the northeast Atlantic and suggested that high glacial surface-water productivity may be confined to lower latitudes. Data from this study, however, are contrary to this idea of increased productivity’ during the last glacial interval, and instead are supported by the earlier work of Joyce et al. (1985), which suggests decreased surface-water productivity’ in the western Gulf of Mexico during glacial intervals. Carbonate Dissolution In addition to its association with fertile surface-waters, Globigerinoides ruber is one of the most dissolution-susceptible species (Thunell, 1976b; Snyder, 1978; Berger, 1970), whereas Globorotalia menardii, Neogloboquadrinadutertrei and Pulleniatina obliquloculata (15, 16 and 19 respectively, on Snyder (1978) scale of Hierarchy of Resistance to Solution) are relatively resistant species to carbonate dissolution. Thunell Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 (1976) reported a strong inverse relationship between the relative abundances of Globigerinoides ruber and Neogloboquadrinadutertrei in intervals reflecting brief episodes of intense dissolution in the southwestern Gulf of Mexico. In addition, a study of planktic foraminifera in Gulf of Mexico surface sediments documented a carbonate dissolution factor based on the high scores of dissolution-resistant species (Brunner, 1979). Brunner suggested that the distribution of the carbonate dissolution factor (mapped factor loadings) reflected regions of dissolution in areas with relatively productive surface waters, thus relating dissolution in surfical sediments with overlying surface-water productivity'. Faunal data from this study (paired frequency data and faunal associations resolved by factor analysis) also record several brief episodes of dissolution throughout the late Quaternary in the northwestern Gulf. Similar to that documented by Thunell (1976a, b), the inverse relationship between Globigerinoides ruber (decreased) and Neogloboquadrinadutertrei (increased), occurring in subzones Zl, 22, Y3, Y5, Y l , XI and X2, reflects dissolution events (* in Figs. 14-21) in the northwestern Gulf. Moreover, Factor 1 corroborates the presence of these dissolution episodes indicated by paired-species frequencies. Although downcore plots of Factor 1 loadings (Fig. 31) most strongly reflect assemblage variations related to surface-water nutrient levels, a record of carbonate dissolution is evident in the sharp negative excursions. Since Globigerinoides ruber (high positve score) is the most dissolution-prone planktic foraminifera (Berger, 1970), and Globorotalia menardii, Pulleniatina obliqulioculata and Neogloboquadrinadutertrei (strong negative scores on Factor 1) are several of the dissolution-resistant species (Snyder, 1978; Coulboum, 1980; Hemleben et al., 1989), negative shifts (shifts toward dissolution-resistant species) indicate a stronger dominance by this assemblage. These negative excursions (* in Fig. 31), then, mark brief dissolution events overprinting the surface-water nutrient signal. These carbonate dissolution events may reflect periods where carbonate production is simply unable to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 keep up with carbonate dissolution, possibly reflecting brief periods of decreased surface-water productivity or increased influx of siliciclastics. Temperature Signals: Glacial-interglacial. the Younger Dryas Cooling, reduced seasonalitv/surface-water instability, and the ecotone concept in the Gulf of Mexico Large-scale as well as more subtle temporal variations in surface-water temperature are reflected by individual species frequency fluctuations and by assemblage variations represented by factors 2 and 3. Downcore plots of Factor 2 loadings clearly depict alternating warm- and cool-water assemblages (Fig. 32) reflecting large-scale surface- water temperature shifts. A cool-water assemblage dominates in the glacial Y zone in most cores. In IG-45-15, the tendency to increasingly favor the cool-water assemblage begins within interglacial subzone XI and continues into the last glacial Y zone with a few perturbations throughout Y7 and Y6. The transition to the interglacial, warm-water assemblage generally begins in Y2, after the last glacial maximum, and continues into the Z zone. Surface-water temperatures, reflected by Factor 2 faunal assemblages and which began warming at the end of the last glacial maximum, appear to have had minor perturbations within the Y 1 interval, but did not again approach anything like full-glacial conditions in the northwestern Gulf of Mexico. However, Kennett et al. (1985) report the presence of an additional subzone that had gone previously unrecognized possibly due to lower strati graphic resolution in earlier work. Subzone Y 1 A, identified from two cores, EN32-PC-4 and -PC-6, from the Orca Basin, was described as being characterized by high frequencies of Globorotalia in/lata , Hasterigerina aequilateralis and Globigerina falconensis with lower frequencies of Neogloboquadrina dutertrei. These faunal data in conjunction with a positive oxygen isotope shift within this interval, were interpreted to indicate that within Y1A a brief return to almost glacial conditions occurred, and that it is correlative to the Younger Dryas cold episode of Europe and the North Atlantic (Kennett et al., 1985; Rower and Kennett, 1990). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. As discussed previously, there is scant evidence of this subzone in the eight cores of this study, even in the two cores (IG-45-15 and PC-2) with the same sampling resolution over this interval. In addition, cores IG-41-21 and IG-41-26, which are closest to Orca Basin and have comparable sediment accumulation rates (Table 3), indicate only a slight frequency increase in Globigerina falconensis (to 5%) and Hasterigerina aequilateralis (to 1-2%), but do not show a Globorotalia inflata frequency increase. Globorotalia inflata is almost entirely absent throughout this interval in all cores, indicating that if the faunal variation and oxygen-isotope shift reported by Kennett et al. (1985) do reflect a cooling event, it did not approach full- glacial conditions. That surface-waters were enriched in 6lsO at this time has been well-documented, but the cause of this enrichment during the Younger Dryas has been frequently debated (Fairbanks, 1989; Broecker et al., 1988a, 1990; Anderson and Thunell, 1993). Accompanying this Ol8-enrichment in the North Atlantic was a decrease in sea-surface temperatures and as a result the 0 18-enrichment has been often attributed to cooler surface-waters at this time (Ruddiman and McIntyre, 1981; Lehman and Keigwin, 1992a). An alternative hypothesis to that of cooler sea-surface temperatures (SST) is that of Fairbanks (1989) who proposed that the Ol8-enrichment was caused by a reduction or slowing of deglacial melting (hence a slow-down in the return of O18- depleted meltwater to the oceans), thus changing the 6l80 content of seawater (Anderson and Thunell, 1993). Evidence in support of the latter hypothesis was reported by Anderson and Thunell (1993) in a study of faunal data to evaluate tropical SST from the Pacific, Atlantic and Indian Oceans. The site that they used to represent the Atlantic Ocean was actually the Orca Basin core EN32-PC-4 of Flower and Kennett (1990). They found no faunal evidence from any of these low-latitude sites, including the Orca Basin, to indicate that SST were cooler during the Younger Dryas than during either the preceding or Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93 following interval. The results of Anderson and Thunell (1993), based on faunal data which are in good agreement with the faunal data from the eight cores of this study, suggest that transfer of the oxygen-isotopic signature throughout the tropical oceans was accomplished via transport by precipitation rather than transport by thermohaline circulation. Possible evidence for reduced seasonality or altered surface-water circulation patterns, either of which may lead to surface-water instability, lies in the assemblages revealed by Factor 3. All the positively scored species are most commonly reported today from subtropical to tropical zones (Tolderlund and Be, 1971; Be, 1977). In the northwestern Gulf, Globigerinoides ruber is the most prolific species throughout both glacial and interglacial intervals as well as today. Neogloboquadrina dutertrei and Globigerinoides sacculifer also occur throughout the Late Quaternary, although in much lower frequencies. The distribution of Globigerinoides ruber, Globigerinoides sacculifer and Neogloboquadrinadutertrei throughout both glacial and interglacial intervals demonstrates their ability to withstand wide ranges in temperature, and for Globigerinoides ruber and Neogloboquadrinadutertrei, salinity, thus making them eurytopic. Species that are negatively loaded are generally more stenotopic and reflect a stronger seasonal signal. For example, Globorotalia inflata, the only known transition zone species (Fig. 13; Tolderlund and Be, 1971; Be, 1977), is mostly absent (<2% in 4 samples; Appendix 2) from the northwestern Gulf today. Pulleniatina obliqulioculata, a tropical/subtropical species, is absent throughout most of the latest interglacial Y zone (Figs. 14-21), and is present today in the northwestern Gulf in moderate to high frequencies (Appendix 1, this study; Phleger, 1960). Tolderlund and Be, (1971) document restricted seasonal occurrences of Pulleniatina obliquiloculata and suggest that it is an excellent indicator of early winter conditions in the western North Atlantic subtropical zone. In contrast, Globorolaliatruncatulinoides, also a subtropical species, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94 is present throughout the last glacial Y zone, albeit in low frequencies (Appendix 2). In addition, it too, exhibits a limited seasonal distribution and is reported by Tolderlund and Be (1971) as an excellent indicator of winter conditions. Downcore plots of factor 3 loadings (Fig. 33) reveal a prominent positive shift (toward increasing influence of the eurytopic assemblage) within the Z2 and lower Zl subzones. Three minor isolated shifts also occur in Y2, Y5 and the interglacial X2 subzone. In the upper Z2 subzone and throughout most of the Y zone, the influence of the stenotopic assemblage is strongest One explanation for the prominent Z2-Z1 shift is a reduction in seasonality. This could be accomplished by warmer winter temperatures during this interval. An alternative explanation is that as sea-level rose, the Loop Current intruded farther into the Gulf, disrupting circulation patterns and causing surface-water instability, thus facilitating the westward penetration of the more eurytopic assemblage. That the Gulf of Mexico acts as a planktic foraminiferal ecotone, a low-latitude and mid-latitude faunal mixing zone, is well-established (Phleger, 1960; Tolderlund and Be, 1971; Boltovskoy and Wright, 1976; Be, 1977; Brunner, 1979). The presence of Globorotalia truncatulinoides (r) and Globigerinoides sacculifer together, in the northwestern Gulf, demonstrate the ecotone concept. Globorotalia truncaiulinoides (r), a mid-latitude species, is considered relict to the northwestern Gulf from the last glacial interval (Phleger, 1960). Its proliferation (averages 16%; Appendix 2) indicates that winter temperatures are low enough to facilitate reproduction (Phleger, 1960; Boltovskoy and Wright, 1976). Globigerinoides sacculifer, a low-latitude species which proliferates during the summer and fall months in the western North Atlantic (Tolderlund and Be, 1971), is present at low to moderate frequencies (1-11%, averaging 6%) in the northwestern Gulf. However, in the eastern Gulf, it attains much greater frequencies (to 25%) because of its proximity to the Loop Current which brings in the low-latitude surface-water that it inhabits (Phleger, 1960). Thus, if the Loop Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95 Current extended farther west into the Gulf, increased frequencies of Globigerinoides sacculifer would be expected. Another way to increase the influence of the eurytopic assemblage would be to reduce seasonality by increasing winter temperatures. A temperature increase may inhibit the ability of Globorotalia truncatulinoides to reproduce, thus impairing its proliferation. An increase in winter temperatures might also enhance the reproductive capabilities of Globigerinoides sacculifer by extending the summer and fall seasons, allowing its frequencies to increase. An increase in winter temperatures, which may limit the frequencies of some species, would favor an overall proliferation of the eurytopic assemblage and further enhance the separation of this assemblage on Factor 3. A decrease in winter or summer temperatures would favor increased frequencies of other cool-water forms (e.g., Globorotalia inflata-, Figs. 25a-c), which although present in the Gulf, do not flourish (Phleger, 1960; Boltovskoy and Wright, 1977). This, however, is not seen in Factor 3. Variations in seasonality throughout the latest Quaternary have been proposed to explain the oxygen isotope records of pink Globigerinoides ruber and white Globigerinoides ruber in the Orca Basin region (Flower and Kennett, 1990). They suggest an offset in isotopic signatures between pink and white Globigerinoides ruber is indicative of enhanced seasonality. Since pink Globigerinoides ruber lives only during the summer months (Flower and Kennett, 1990), its increased temporal presence, if winter temperatures were higher, would yield an isotopic signature closer to that of white Globigerinoides ruber, which is a year-round resident. Thus, reduced seasonality w'ould produce similar isotopic signatures for both forms of Globigerinoides ruber and offset records would indicate enhanced seasonality. Their oxygen isotopic records do depict an offset throughout the late glacial from 19 to 10.2 ky, except from approximately 12.1-11.1 ky during the meltwater spike (Flower and Kennett, 1990). At the Pleistocene-Holocene boundary, the magnitude of the offset Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 6 decreases from 1.5 per mil to 0.5 per mil, and by about 8.6 ky, the offset is gone. Both pink and white Globigerinoides ruber have roughly the same isotopic signature, probably because of increased winter temperatures, thus reflecting a reduction in seasonality. This isotopic evidence of reduced seasonality as a result of increased winter temperatures is in good agreement with results inferred from Factor 3, which indicate reduced seasonality shortly after the Pleistocene-Holocene (Z/Y) boundary and into the middle Z l subzone. Factor 3 loadings reflect enhanced seasonality throughout most glacial intervals, which is consistent with the oxygen isotopic offset of Flower and Kennett (1990). Synopsis The planktic foraminiferal record of the latest Pleistocene and Holocene reveals several paleoceanographic and paleoclimatic changes. Extensive meltwater influx to the northwestern Gulf is reflected by frequency peaks of Globigerinoides ruber. Despite minor perturbations in surface-water temperature, once warming began after the last glacial maximum, surface waters did not cool significantly, certainly not to full-glacial conditions, leaving no record of the Younger Dryas event in the northwestern Gulf. Temporal distribution of planktic foraminiferal assemblages suggests decreased surface- water productivity in the northwestern Gulf during glacial intervals relative to those of interglacial intervals X and Z. Carbonate dissolution was enhanced during interglacial intervals indicating the presence of less-corrosive bottom waters during the last glacial interval. The presence of a more eurytopic and subtropical-tropical assemblage, shortly after the Pleistocene-Holocene (Z/Y) boundary' and into the mid to early Holocene, may reflect a period of increased winter temperatures leading to reduced seasonality or a deeper penetration of the Loop Current into the Gulf of Mexico, which may have resulted in sea-surface instability. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4 BENTHIC FORAMINIFERAL RECORD Despite debate over the utility of benthic foraminifera as paleoceanographic tools (e.g. Boyle, 1990; Schnitker, 1994), several recent studies have successfully used benthic foraminiferal assemblages to trace bottom-water conditions and to infer changes in deep-water circulation (Ishman et al., 1996; Rasmussen et al., 1996) as well as other environmental parameters such as productivity and bottom-water corrosivity (Mackensen et al., 1995). In the Gulf of Mexico, a relationship between water-mass boundaries and benthic foraminiferal associations has been documented in bathyal depths (Denne and Sen Gupta, 1991, 1993). These investigations, however, have not clarified trends of bathymetric succession (if any) of benthic foraminiferal species in the lowermost bathyal and abyssal waters of this marginal sea. Since waters at lower bathyal and abyssal depths in the Gulf belong to a single water mass, Gulf Basin Water (GBW; within which the variations in temperature, salinity, and oxygen are negligible; Chapter I), benthic foraminiferal assemblage variations are expected to be minimal if the overlying water mass is the primary factor controlling their distributions. Many studies examining the effects of organic matter and bottom- and pore- water oxygen content on the distribution of benthic foraminifera have demonstrated that food is an overall limiting factor in controlling benthic foraminiferal distributions both vertically and laterally in seafloor sediments (Caralp, 1989; Corliss and Emerson, 1990; Gooday, 1988, 1993; Loubere, 1991; Loubere et al., 1993a, b; Linke and Lutze, 1993; Lutze and Coulboum, 1984; Smart, et al., 1994). However, this does not render benthic foraminifera useless as indicators of changing bottom-water conditions; it simply complicates the picture. Extracting such a signal is possible by using 97 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 independent lines of evidence to isolate the part of the assemblage that is dominated by the food signal (Schnitker, 1994; Mackensen et al., 1995). Controversy regarding deep-water formation during the last glacial interval has resulted in numerous studies proposing scenarios such as complete deep-water formation shut-down (Streeter and Shackleton, 1979; Broeckeretal., 1985, 1989), reduced, but present deep-water formation (Streeter and Shackleton, 1979; Boyle and Keigwin, 1982; Duplessy and Shackleton, 1984; Mix and Fairbanks, 1985; Curry et al., 1988), and formation of waters whose densities allow them to sink only to intermediate- rather than deep-water levels (Boyle and Keigwin, 1987; Lehman and Keigwin, 1992 a, b; Fichefet et al., 1994; Haddad and Droxler, 1996). Detecting the influence of deep-waters (NADW) and intermediate-waters (SAIW or proposed NAIW) is critical to understanding the changing oceanographic structure throughout the last deglaciation, and benthic foraminifera can provide insight into this problem (Ishman et al., 1996; Rasmussen et al., 1996). In the Gulf of Mexico, the influence of NADW is reduced by mixing with Caribbean Midwater; the resulting water mass has a higher silicate content and lower salinities than pure NADW (Metcalf, 1976; Denne, 1990). The deep Gulf renewal w’aters that flow over the 1900 m-deep sill, then, cam- a component, albeit dilute, of NADW into Gulf of Mexico bottom waters. Thus, it may be possible to identify the presence of this NADW-component in the deep Gulf by benthic foraminiferal assemblages, and if so, to use downcore benthic foraminiferal assemblages to identify its presence or absence during the last deglaciation. This chapter is composed of two parts, the first of which is a study of benthic foraminiferal distributions in surface sediments from core-top samples. The purpose of the core-top study is to develop a modem analog for lower bathyal and abyssal environments in the present-day Gulf of Mexico. This study also examines the inter relationships between foraminiferal distributions and sediment accumulation rates, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99 organic carbon amount or type, carbonate content (Chapter 2), surface-water productivity and nutrient levels, carbonate dissolution (Chapter 3), and bottom-water ventilation. Part two is a comparison of Recent benthic foraminiferal distributions with those of the latest Pleistocene (Y4-Y1 subzones) to evaluate: 1) if changing deep-water circulation is evident within the Gulf basin, 2) if variations in surface-water productivity and nutrient levels are reflected by shifts in benthic foraminiferal abundances, and 3) the effects of fluctuating sedimentation patterns on glacial/interglacial benthic foraminiferal distributions. Distribution of Recent Benthic Foraminifera One-hundred sixty-six species of benthic foraminifera, 57 agglutinated and 109 calcareous, were identified from 27 core-top samples (Table 9; Plates 2,3; Appendix 3). Functions of species diversity were calculated using all 166 species. Relative abundances of all species and absolute abundances of selected species were used to examine the relationship between particular species and water depth, and to refine lower bathyal and abyssal zonations. R-mode factor analysis was performed using the 26 most abundant species (keeping the number of variables less than the number of observations) to examine benthic foraminiferal assemblages, whereas Q-mode cluster analysis was used delineate foraminiferal biofacies. Species Diversity There is no distinct trend in simple species diversity or species richness (S=number of species in a sample) with depth from lower bathyal to abyssal environments (Fig. 35). Such diversity values are less variable for samples from waters deeper than 2,400 m, but this probably relates to the fact that fewer samples were studied from this depth range than from the one above. For the entire sample set (Table 9), species richness, S, ranges from 20 to 61 (average 43 ± 9.95). Species diversity' values for the Shannon- Wiener Information Function, H(S), van- from 2.07 to 3.43 (average 2.86 ± 0.36), and for species equitability, E, from 0.61 to 0.91 (average 0.77 ± 0.07). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 Table 9. Taxonomic List of Benthic Foraminifera Adercotryma glomerala (Brady) = Lituolaglomerala Brady, 1878 Alabaminella turgida (Phleger and Parker) = Eponides turgidus Phleger and Paiker, 1951 Alveolophragmium sp. A Ammobaculites filiformis Earland = Ammobaculites agglinatus (d'Orbigny) var. filiform is Earland 1934 Ammodiscus incertus (d'Orbigny) = Operculinaincerta d'Orbigny Am m odiscus sp. A Ammodiscus tenuis Brady, 1881 Ammoglobigerina sp. A Ammoniaparkinsoniana (d'Orbigny) = Rosalinaparkinsoniana d'Orbigny, 1839 Ammotium fragile Warren, 1957 Angulogerina sp. cf. A. bella Phleger and Parker, 1951 Ammovertellina sp. A Astacolus crepidulus (Fitchel and Moll) = Nautilus crepidulus Fitchel and Moll, 1803 Bathysiphon spp. Biloculinellairregularis (d'Orbigny) = Biloculinairregularis d'Orbigny, 1839 Bolivina alata (Seguenza) = Vulvulina alata Seguenza, 1862 Bolivinaalbatrossi Cushman, 1922 Bolivinabarbata Phleger and Parker, 1951 Bolivina fragilis Phleger and Parker, 1951 Bolivinalanceolata Parker, 1954 Bolivina lowmani Phleger and Parker, 1951 Bolivina minima Phleger and Parker, 1951 Bolivina ordinaria Phleger and Parker, 1952 Bolivinapaula Cushman and Cahill, 1932 Bolivina pusilla Schwager, 1866 Bolivina subaenarienesis Cushman = Bolivina subaenarienesis Cushman, 1922 Bolivina subspinenscens Cushman, 1922 Bolivina translucens Phleger and Parker, 1951 Bulimina aculeata d'Orbigny, 1826 Bulimina alazanensis Cushman, 1927 Bulimina marginata d'Orbigny, 1826 Bulimina mexicana Cushman = Bulimina striata d'Orbigny var. mexicana Cushman, 1922 Bulimina spicata Phleger and Parker, 1951 Buliminella elegantissima (d'Orbigny) = Bulimina eleganiissima d'Orbigny, 1839 Cassidulinacarinata Silvestri = Cassidulina laevigata d'Orbigny var. carinata Silvestri, 1896 Cassidulina crassa d'Orbigny, 1839 Cassidulina neocarinata Thalmann, 1950 Cassidulina subglobosa Brady, 1881 Cassidulinoides tenuis Phleger and Parker, 1951 Chilostomella oolina Schwager, 1878 Cibicides bradyi Trauth = Truncatulina bradyi Trauth, 1918 Cibicides corpulentus Phleger and Parker, 1952 (table con’d) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 Cibicides incrassatus (Fitchel and Moll) = Nautilus incrassatus Fitchel and Moll, 1798 Cibicides robertsoniansus (Brady) = Truncatulinarobertsoniana Brady, 1881 Cibicides robustus Phleger and Parker, 1951 Cibicides rugosus Phleger and Parker, 1951 Cibicides sp. A Cibicides sp. B Cibicides sp. C Cibicides sp. D Cibicides umbonatus Phleger and Parker, 1951 Cibicides wuellerstorfi (Schwager) = Anomalina wuellerstorfi, Schwager, 1866 Cibicidoides sp. cf. C. m ollis (Phleger and Parker) = Cibicides mollis Phleger and Parker, 1951 Cibicidoides mundulus (Brady, Parker, and Jones) = Truncatulina mundulus Brady, Parker, and Jones, 1888 Cibicidoides bathyalis (Poag) = Truncatulina pachyderma Rzehak, 1886 = Cibicidoides "floridanus" (Cushman) forma bathyalis Poag, 1981 Cibicidoides sublittoralis (Poag) = Truncatulina pachyderma Rzehak, 1886 = Cibicidoides "floridanus" (Cushman) forma sublittoralis Poag, 1981 Comuspira planorbis Schultze, 1854 Cribostromoides sp. A Cribrostomoides nitidium (Goes) = Haplophragmium nitidum Goes, 1896 Cribrostomoides sp. A Cribrostomoides subglobosum (Sars) = Lituola subglobosa Sars, 1872 Cribrostomoides wiesneri (Parr) = Labrospira wiesneri Parr, 1950 Cyclammina cancellata Brady, 1879 Eggerella bradyi (Cushman) = Vemeuilina bradyi Cushman, 1911 Eggerella propinqua (Brady) = Vemeuilina propinqua Brady, 188 Elphidium spp. Epistominellaexigua (Brady) = Pulvinulinaexigua Bradv, 1884 Epistominellavitrea Parker, 1953 Eponidesantillarum (d'Orbigny) = Rotalina antillarum d'Orbigny, 1839 Eponides sp. A Fursenkoina pauciloculata (Brady) = Virgulinapauciloculata Brady, 1884 Gaudryina sp. A Gavelinopsis translucens (Phleger and Parker) = "Rotalia" translucens Phleger and Parker, 1951 Globobulimina ajflnis (d'Orbigny) = Bulimina ajflnis d'Orbigny, 1839 G .ovata (d'Orbigny) = Bulimina ovata d'Orbigny, 1846 Glomospira charoides (Jones and Parker) = Trochammina squamata Jones and Parker var. charoides Jones and Parker, 1860 Glomospira gordialis (Jones and Parker) = Trochammina squamata Jones and Parker var. gordialis Jones and Parker, 1860 Gyroidina altiformis (R.E. and K.C. Stewart) = Gyroidina soldanii (d'Orbigny) var. altiformis R.E. and K.C. Stewart, 1930 Gyroidina orbicularis d'Orbigny, 1826 Gyroidinoides sp. cf . G.rotundimargo (Stewart and Stewart) = Gyroidina soldanii d'Orbigny var. rotundimargo Stewart and Stewart, 1930 Gyroidinoides polius (Phleger and Parker) = Eponides polius Phleger and Parker, 1951 Gyroidinoides sp. A (table con'd) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 Gyroidinoides spp. Gyroidinoides umbonalus (Silvestri) = Rotaliasoldanii (d'Orbigny) var. umbonata Silvestri, 1898 Hansensica regularis (Phleger and Parker) = Eponides regularis Phleger and Parker, 1951 Hansensica sp. A Hanzawaia concentrica (Cushman) = Truncatulina concentrica Cushman, 1918 Haplophragmoides bradyi (Robertson) = Trochammina bradyi Robertson, 1891 Haplophragmoides sp. A Haplophragmoides sp. B Haynesina depressula (Walker and Jacob, emend. Murray) = Nautilis depressulus Walker and Jacob, 1798 Hoeglundina elegans (d'Orbigny) = Rotalia (Turbinuline) elegans d'Orbigny, 1826 Hormosina globulifera Brady, 1869 Hormosina spp. Hormosinella sp. A Hormosinella sp. B Hyalinea balthica (Gmelin) = Nautilus balthicus Gmelin, 1791 Ioanella tumidulus (Brady) = Truncatulina tumidula Brady, 1884 Karreriella bradyi (Cushman) = Gaudryina bradyi Cushman, 1911 Karrerulina apicularis (Cushman) = Gaudryina apicularis Cushman, 1911 Lagenammina spp. Laticarininapauperata (Parker and Jones) = Pulvinulinarepanda Fichtel and Moll var. menardii d'Orbigny subvar. pauperata Parker and Jones, 1865 Loxostomum truncatum Phleger and Parker, 1951 Martinottiella occidentalis (Cushman) = Clavulina occidentalis Cushman, 1922 Melonis pompilioides (Fichtel and Moll) = Nautilus pompilioides Fichtel and Moll, 1798 Melonis barleeanus (Williamson) = Nonionina barleeana Williamson, 1858 Multifidella sp. A Neoconorbina terquemi (Rzehak) = Discorbina terquemi Rzehak, 1888 Neocrosbyia minuta (Parker) = Valvulineria minuta Parker, 1954 Neolenticulina peregrina (Schwager) = Cristellaria peregrina Schwager, 1866 Neolenticulina sp. A Nodosariaflintii Cushman, 1923 Nonionella opima Cushman, 1947 Nonionellina sp. A Nonionellina sp. B Nonionoides grateloupi (d'Orbigny) = Nonionina grateloupi d'Orbigny, 1826 Nuttallidesdecorata (Phleger and Parker) = Pseudoparella (?) decorata Phleger and Parker, 1951 Oculosiphon linearis (Brady) = Rhabdammina linearis Brady, 1879 Oridorsalis sp. A Oridorsalis sp. B Oridorsalis tener (Brady) = Truncatulinatener Brady, 1884 Oridorsalis umbonatus (Reuss) = Rotalina umbonata Reuss, 1851 Oridorsalis westi Anderson, 1961 Osangularia culler (Parker and Jones) = Planorbulina farcta (Fichtel and Moll) var. ungeriana (d'Orbigny) subvar. culler Parker and Jones, 1865 Osangularia rugosa (Phleger and Parker) = Pseudoparella (?) rugosa Phleger and Parker, 1951 (table con'd) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103 Paumotua sp. cf. P. terebra (Cushman) = Eponides terebra Cushman, 1933 Planorbulina mediteranensis d'Orbigny, 1826 Polystomammina nitidia (Brady) = Trochammina nitidia Brady, 1884 Psammosphaera sp. A Pseudocancris sp. A Pseudonodosinella sp. A Pseudononion allanticum (Cushman) = Nonionellaatlantica Cushman, 1947 Pseudononion clavatum (Cushman) = Nonionellaclavata Cushman, 1931 Pullenia sp. A Pulleniabuiloides (d'Orbigny) = Nonionina bulloides d'Orbigny, 1846 Pullenia quinqueloba (Reuss) = Nonionina quinqueloba Reuss, 1851 Pullenia subcarinala (d'Orbigny) = Nonionina subcarinata d'Orbigny, 1839 Pullenia subsphaerica Parr, 1950 Pyrgo lucemula (Schwager) = Biloculinalucemula Schwager, 1866 Pyrgo murrhina (Schwager) = Biloculinamurrhina Schwager, 1866 Quadrimorphina glabra (Cushman) = Valvulineria vilardeboana Cushman var. glabra Cushman, 1927 Quadramorphina sp. A Quinqueloculina bosciana d'Orbigny, 1839 Quinquebculinalamarc/dana d'Orbigny, 1839 Quinqueloculina sp. cf. Q. seminulum (Linne) = Serpula seminulum Linne, 1758 Quinqueloculina venusta Karrer, 1868 Reophax sp. cf. R . dentaliniformis Brady, 1881 Reophax sp. A. Reussella sp. A Rhizammina algaeformis Brady, 1879 Rhizammina sp. A Rhumbler sp. A Robertinoides bradyi (Cushman and Parker) = Robertina bradyi Cushman and Parker, 1936 Saccammina sp. cf. S. socialis Brady, 1884 Saccammina difflugiformis (H. B. Bradv) = Reophax difflugiformis H. B. Brady, 1879 Saccammina sphaerica Sars, 1872 Saccorhizaelongala (Brady) = Hyperamminaelongata Brady, 1878 Saccorhizafriablis (Brady) = Hyperamminafriabilis Brady, 1884 Sacchorizaramosa (Brady) = Hyperamminaramosa Brady, 1879 Sigmoilopsis schlumbergeri (Silvestri) = Sigmoilina schlumbergeri Silvestri, 1904 Siphonina bradyana Cushman, 1927 Siphotextidaria affinis (Fomasini) = Sagrina affinis Fomasini, 1883 Siphotrochammina squammata (Jones and Parker) = Trochammina squamata Jones and Parker, 1860 Sphaeroidina bulloides d'Orbigny, 1826 Spiroplectella cylindroides Earland, 1934 Stainforthia complanata (Egger) = Virgulinaschreibersiana Czjzekvar. complanata Egger, 1893 Textulariagramen d'Orbigny, 1846 Tretomphalus atlanticus Cushman, 1934 Trifarina bradyi Cushman, 1923 Trochammina advena Cushman, 1922 Trochammina sp. cf.7\ inflata (Montagu) = Nautilus inflatus Montagu, 1808 (table con'd) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 Trochamminaglobigeriniformis (Parker and Jones) = LLtuolanautiloidea var. globigeriniformis Parker and Jones, 1865 Trochamminajaponica Ishiwada, 1950 Cystamminapauciloculaia (Brady) = Trochamminapauciloculata Brady, 1879 Trochammina sp. A Uvigerina auberiana d'Orbigny, 1839 Uvigerina hispidocostata Cushman and Todd, 1945 Uvigerina peregrina Cushman, 1923 Uvigerinaparvula (Cushman) = Uvigerina peregrina Cushman var. parvuLa Cushman, 1923 Valvulineria "A" Valvulineria humilis (Brady) = Truncatulina humilis Brady, 1884 Valvulineria mexicana Parker, 1954 Valvulineria opima as identified by Pfium and Frerichs, 1976 Valvulineria sp. A Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 Plate 2. Benthic Foraminifera. 1,2) Eggerella bradyi 300pi, 250/*; 3) E. bradyi with possible nematode borings 350//; 4, 5) Siphotextidaria affinis 400pi, 270//; 6, 7) Quinqueloculina venusta 170//, 230pi; 8) Pyrgo murrhina 130pi; 9) Sigmoilopsis schlumbergeri 120//; 10, 11) Hoeglundina elegans ( 10 with borings) 110pi, 170pi; 12) Bolivina lowmani 500pi; 13, 14) Cassidulina subglobosa 120//, 600pc, 15) Stainforthia complanata 270//; 16) Bulimina alazanensis 270//; 17, 18) B. aculeata 200pi, 270//; 19) Uvigerina auberiam 370//; 20, 21) U. peregrina 370//, 170//; 22, 23) U. hispidocosiata 100//, 220//; 24, 25) Bulimina mexicana 150//, 230//. All scale bars equal 100//. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107 Plate 3. Benthic Foraminifera. 1,2) Alabamitiella turgida 600/*, 700/*; 3,4) loanella tumidula 550/*, 650/<; 5, 6) Cibicides wuellerslorfi 130/*, 160/*; 7, 8) C. bradyi 250ft, 300/*; 9, 10, 11) Nuttallides decorata 550/*, 550ft, 500/*; 12, 13) Melonis pompilioides 180pi, 200pr, 14) Pullenia bulloides 500ft; 15, 16, 17) Oridorsalis tener 370/*, 220/*, 370/*; 18, 19) O. umbonatus 180/*, 220/*; 20) O. sp. A 850/*; 21, 22) Gyroidinoides poliits 450/*, 430/*, 23, 24) Biloculinella irregularis 350/*, 370/*. All scale bars equal 100/*. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109 H(S) E 4 0 .5 0.8 1.0 1500 2 0 0 0 - 2500- a . 4> a <><>•• L. 3000- -*■>V 83 £ 3500- 4000 10 20 30 40 50 60 70 Figure 35. Plots of species diversity measures against water depth, showing persistently high species diversity, but no discernible trend with water depth, S, is number of species (open diamonds), H(S) is the Shannon-Wienner Information Function (closed circles) and E is a measure of species equitability (open circles). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110 As in the study of Gibson and Buzas (1973), species diversity values for the abyssal northwestern Gulf of Mexico exhibit no trend with water depth. My diversity values (Table 10), however, are considerably higher than those of Gibson and Buzas (1973), which range from 9 to 14 for S and 1.82 to 2.39 for H(S), contradicting their conclusion that the northwestern Gulf of Mexico has low benthic foraminiferal diversity. High species equitability values reported here are similar to those found by Gibson and Buzas (1973) and indicate the absence of strong dominance by a few species. These high E values, typical for the study area, are greater than those of the northeastern Gulf and of delta regions in the northwestern Gulf (Gibson and Buzas, 1973). Relative abundances Several depth-related patterns of relative abundance reflected by variations in dominant taxa are recognized in the deep Gulf. Because relative abundance (%) depends on the abundances of all species in the sample, species with low absolute abundances in some samples (especially at depths below 2,400 m) may show high relative abundances in the same samples, and these are recognized as dominant taxa in these assemblages. Of the four species that constitute more than 10% of the assemblage in one or more samples, two attain their highest relative abundances in depths less than 2.400 m. Bulimina aculeata is common (> 10%) at < 2,400 m depths but absent in deeper waters, whereas Nuttallidesdecorata maintains a > 10% abundance in the 1,500- 2.400 m range and in the two deepest samples (3,632 and 3,850 m), but not in the intermediate (2,400-3,600 m) range (Fig. 36). The other two, Alabaminellaturgida and Bolivina lowmani, maintain high relative abundances (>20%) at all depths (Fig. 37). Some minor species, however, such as Cibicides bradyi, Eggerella bradyi, and Trochammina globigeriniformis , are eurybathic within the depth range of the study area (Fig. 38). Five agglutinated species, Glomospiracharoides, Karrerulina apicularis, Saccammiria sphaerica, Cribrostomoides wiesneri, and Spiropleciella cylindroides, and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ill Table 10. Species diversity measures for each core-top sample: S, number of species per sample, H(S), Shannon- Wiener Information Function, andE, species equitability. Sample No. S H(S) E IG-38-10 57 2.62 0.647 IG-38-18 47 3.16 0.821 IG-41-13 44 3.43 0.907 IG-41-18 43 2.58 0.685 IG-41-19 52 2.93 0.742 IG-41-21 42 3.09 0.828 IG-41-23 30 2.07 0.607 IG-41-24 61 3.12 0.763 IG-41-26 40 2.93 0.795 IG-41-28 56 3.29 0.817 IG-41-29 53 3.15 0.793 IG-45-9 25 2.64 0.821 IG-45-14 54 3.23 0.81 IG-45-15 44 2.84 0.751 IG-46-7 51 3.19 0.812 IG-46-8 29 2.27 0.675 IG-46-9 20 2.24 0.749 IG-46-11 46 2.94 0.769 IG-46-12 40 2.95 0.799 BC-3 45 3.35 0.88 BC-4 30 2.58 0.759 BC-7 46 2.5 0.654 BC-8 43 2.6 0.692 89-10 PC-1 44 3 0.792 89-10 PC-2 35 2.54 0.715 89-10 PC-3 41 3.04 0.818 89-10 PC-5 41 2.88 0.774 Mean 43 2.86 0.766 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 Relative Abundance (%) 0 10 20 30 40 SO 1500 o» Bulimina o • aculeata 2000 - Nuttallides decorata S 2500- 4>a. o W V 3000- 03 £ 4000 Figure 36. Percentage plots of Nuttallides decorata and Bulimina aculeata against water depth, showing their highest relative abundances at depths less than 2000 m. Relative Abundance (%) 0 10 20 30 40 50 60 70 1500 Alabaminella turgida Bolivina lowmani 2000 2500- 4)Q. Q 4>u 3000- -wes £ 3500- 4000 Figure 37. Percentage plots of Alabaminella turgida and Bolvini lowmani against water depth, showing their persistently high relative abundances at all depths. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113 three calcareous species, Ioanella tumidula, Gyroidirtoides polius, and Stainforthia complanata , show a distinct trend of increasing relative abundance with increasing water depth, especially below 2,400 m (Fig. 39). Finally, several species exhibit peak relative abundances in the 2,000-2,400 m range. These include Gavelinopsis translucens, Osangulariaculter, 0. rugosa, Cassidulim subglobosa, and Epistominellaexigua (Fig. 40). Absolute abundance In order to assess the effect of depth-related environmental variables on the size of foraminiferal populations, absolute abundances of the entire assemblage as well as of the constituent species were calculated. This absolute abundance ("foraminiferal number"), expressed as the total number of benthic foraminifera g '1 sediment varies considerably, but, overall, it decreases with depth (Fig. 41), and all values higher than 200 g"1 sediment are confined to depths above 2,000 m. Most species that attain an absolute abundance greater than 10 g '1 sediment show the same trend (Fig. 42). All have peak abundances at depths less than 2,400 m, and several, such as Bolivina albatrossi, Bulimina marginata, B. aculeata, Gyroidina orbicularis, Laticarinina pauperata, and Paumotua sp. cf. P. lerebra are unrecorded at depths greater than 2,400 m. Factor Analysis R-mode factor analysis extracted 6 factors which accounted for 79% of variance. These six factors reflect nine species groups, identified by factor loadings (Table 11), that are related by some environmental preference or parameter. Species factor loadings with (- or +) magnitudes > 0.6 are considered significant and are used to characterize factor assemblages. Species loadings with values < 0.6 were repetitive and contributed no additional information to the characterization of assemblages. The distribution of factor scores, which describes the influence of a factor on a particular sample, is Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 Relative Abundance (%) 0 1 2 3 4 5 Trochammina globigeriniformis 0» Eggerelia 2000 iT o° bradyi C ibicida bradyi 2500H 3500- O o. Figure 38. Percentage plots of three minor species against water depth, showing their eurybathic nature. 0 3 6 9 12 15 3 6 9 12 15 1500-^75-^-----1----'--- 1500 J-----1___ i_i_ Cribrostomoides Saccam mina mesneri sphaerica Glomospira SpiropUcteUa ch amides 2000 cylindroides Gyroidittoides IoaneUa palius tum idula Slainforlhi 2500- Karrerulina compltmata apiculara 2 5 0 0 - Va 3> o a Bo0*o L. 30 00- 3 0 0 0 - £ 3500 .*oS°o o 3 5 0 0 - & • x> o • A OO o 4000 4000 £1 Figure 39. Percentage plots for eight species against water depth, showing a trend of increasing relative abundance with increasing depth. All of these species attain their highest abundances at water depths greater than 2700 m. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 Relative Abundance (%) o 10 20 30 40 1500 © CaaiduUna subglobosa • EpistouuntUa 2000 adgua o Gavelinopsis trunslucens £ A Osangularia 2500 culler JS«■» fit □ Osangularia Q rugosa 3000 a £ 3500 •] £ 4000 Figure 40. Percentage plots of five species against water depth, showing highest abundances between 2000-2400 m. # Total Foraminifera/g sed 0 200 400 600 2000 - 2500 - « 3000 - 4000 Figure 41. Plot of the number of foraminifera (per gram of sediment) against water depth, showing a decrease in absolute abundance of total foraminifera with increasing water depth. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 # Foraminifera/g sed # Foraminifera/g sed 50 100 150 200 SO 100 150 200 1500 _J______I______L ____ Alabaminella j» o O A Cibicides turgida wuellerstoifi Bolivina Cassidulina 2000 >• lowmani 2000 subglobosa Clomospira EpistomineUa charoides ezigua Nuttallides 2500 - 2500 - decorata 4>a a 3000 - 3000 o £ 3500 < [ 4000 4000 # Foraminifera/g sed # Foraminifera/g sed 0 10 20 30 40 50 0 10 20 30 40 50 1500 1500 ■£> <>'• 1 co « o Bolivina albatrossi .J6* loanella 2000 2000 -» tum idula Bulim ina aculeata Osangularia culler B ulim ina e marginata 2500- PuUenia 2500- bulloides j: Gyroidina orbicularis Ladcariuina 3000- 3000- itb pauperata ss Paumotua sp. £ cC P. terebm 35001 3500-j | •. 4000 4000- Figure 42. Plots of the number of individuals (per gram of sediment) of selected species against water depth, showing an overall trend of decreasing absolute abundance with increasing water depth. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 Table 11. Rotated Factor Pattern (loadings) from R-mode Factor Analysis. Boxed loadings considered significant (>0.7) for the interpretation of factor assemblages. S p e c ie s Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6 Cribrostomoides wiesneri 0.89993 -0.11692 -0.07332 -0.00544 -0.03548 -0.09684 Gyrodinoides polius 0.89753 -0.18757 -0.22396 -0.02504 0.09342 0.00147 loanella tumidula 0.86635 -0.17809 -0.25240 -0.08469 -0.07590 0.27396 Glomospira charoides 0.85675 -0.19222 -0.00974 -0.08740 -0.18190 -0.03697 Karrerulina apicularis 0.83169 -0.15969 -0.03988 -0.11624 -0.26259 0.00663 Spiroplectella cylindroides 0.83006 -0.20035 -0.14527 -0.17874 -0.14349 0.06416 Saccammina sphaerica 0.74139 -0.18347 -0.12344 -0.24221 -0.34468 0.02296 Osangularia cutter -0.21198 0.92395 -0.11909 0.00757 -0.08979 -0.02143 Gavelinopsis translucens -0.16483 0.90117 -0.10280 0.03164 -0.03074 0.03294 Osangularia rugosa -0.16559 0.76224 -0.24888 -0.22344 0.03965 -0.08155 Bolivna albatrossi -0.34596 0.73524 -0.01741 0.21866 0.32144 0.03644 Epistominella exigua -0.40229 0.54509 0.01798 0.33900 0.46581 -0.16360 Cibicides bradyi 0.02220 -0.21194 0.85729 -0.16386 -0.09557 -0.00471 Laticarinina pauperata -0.25117 -0.07993 0.79556 0.06010 0.10215 0.25803 Hansenisca regularis -0.12249 -0.05844 0.78196 0.24072 0.03923 -0.07146 Pullenia bulloides -0.24279 -0.14955 0.61361 0.08343 0.48836 -0.13694 Uvigerina peregrina -0.41994 -0.23258 -0.03260 0.72199 0.21744 -0.07591 Bulimina aculeata -0.21732 -0.04248 0.54432 0.70636 0.03248 -0.08595 Bulimina marginata -0.31998 0.33973 0.25735 0.70235 0.02253 -0.14682 Gyrodinoides umbonatus 0.09002 -0.29128 -0.30030 -0.40724 -0.22007 -0.24749 Hoeglundina elegans -0.26034 0.05978 0.36300 -0.66657 0.21554 -0.17006 Nuttallides decorata -0.04378 -0.10745 -0.06242 0.16740 0.86021 0.28156 Cassidulina subglobosa -0.53425 0.20142 0.01159 -0.10825 0.63964 -0.25331 Bolivina lowmani 0.27789 -0.17431 -0.32038 0.13829 -0.60127 0.13452 Cibicides wuellerstorfi 0.20602 -0.22918 -0.05041 -0.06915 0.00676 0.81336 Alabaminella turgida 0.19752 -0.49665 -0.15170 -0.04622 0.00029 -0.71707 % Variance Explained 24.60% 15.46% 12.80% 10.10% 9.60% 6.50% Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 depicted on maps indicating how highly each sample scored on a factor (Table 12; Figs. 43-48). Mixed Agglutinated-Calcareous Assemblage (F1+) Species with strong positive loadings on Factor 1 include five agglutinated species Cribrostomides wiesneri, Glomospira charoides, Karrerulinaapicularis, Saccammina sphaerica, Spiroplectella cylindroides and two calcareous species Ioanellatumidula and Gyroidinoides polius. Ioanella tumidula has been previously reported in the Gulf of Mexico from water depths of 2836-3367 m by Phleger (1951), from 1883-3253 m, by Pflum & Frerichs (1976), with abundances > 10% at abyssal depths and from the lower slope, rise and Sigsbee Plain (Poag, 1981). Gyroidinoides polius, although generally not as abundant as Ioanella tumidula, is also reported from these depths (Pflum & Frerichs, 1976; Poag, 1981). However, Denne and Sen Gupta (1991) associated it with Caribbean Mid-Water (CMW; 1000-1500 m). Poag (1981) reported that four of the five agglutinated species are typically found on the lower slope and Sigsbee Plain. Relative abundances of these species are typically highest at water depths greater than 2700 m (Jones and Sen Gupta, 1995). Scott et al. (1989) found Ioanella tumidula, (= Eponides tumidula ) in an assemblage they associated with a major influx of Atlantic-derived intermediate water to the Arctic Ocean. In the Amerasian Basin, Ishman et al. (1996) suggested that the Oridorsalis tener and Ioanella tumidula, assemblage reflected development of the modem Arctic Ocean structure, which includes Atlantic-derived Intermediate Water and Canada Basin Deep Water. Ioanella tumidula may reflect the remnants of a glacial, deep-water fauna that has persisted in abyssal Gulf waters, possibly indicating the presence of cold, North Atlantic water in the Gulf of Mexico during the Pleistocene. Mixed-calcareous and agglutinated assemblages have been interpreted many different ways. In the Artie Ocean, they were inferred to reflect well-mixed bottom- and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Table 12. Factor Scores from R-mode Factor Analysis. z £ (O © E Q. © o' m © CD CO y— CO CO o CM 1 0 CM pw CM *43a-1 < * 1 Oistnbution of scores on Factor 1 Figure 43. Map showing geographic distribution of strong (labeled stations) Factor 1 scores (> 0.7). -■« ,02*'-31 ES° Distribution of scores on Factor 2 Figure 44. Map showing geographic distribution of strong (labeled stations) Factor ? scores (> 0.7). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.4 1.4 •-.72, -25* .02 -.82 100 -.61 Distribution of scores on Factor 3 •l.2/« km S o re (> 07)P showing ^ g ra p h ic distribution of strong (labeled stations) Factor 3 -30* ,••11 •46- 2.6 1.4 1.1 -i.i« ■; -1.3 ' .25 -25* -.23 1.5 .18 100 Distribution of scores on Factor 4 km Figure 46. Map showing geographic distribution of strong (labeled stations) Factor 4 scores (> 0.7). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.7, 1.7 .44 •- 1.1 L-.76 • 1.0 100 • |1.1 Distribution of scores on Factor S Figure 47. Map showing geographic distribution of strong (labeled stations) Factor 5 scores (> 0.7). -30' .95, .93 1.7 '-9S -o.9.? V 1>i •-.15 .99 -.69 .42 100 • -.3 Distribution of scores on Factor 6 Figure 48. Map showing geographic distribution of strong (labeled stations) Factor 6 scores (> 0.7). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123 deep-waters (Scott et al., 1989), whereas in the Amerasian Basin they were thought to indicate stressed environments reflecting periods of sediment disturbance with subsquent recolonization (Ishman et al., 1996). Many others have suggested such a mixed assemblage indicates somewhat corrosive-bottom waters which remove more solution-prone calcareous forms, differentially preserving agglutinated forms (e.g. Mackensen and Douglas, 1989; Ishman et al., 1989; Clark et al., 1994; Mackensen et al., 1989, 1995). This assemblage represents remnants of a glacial fauna ( Ioanella tumidula) that has persisted in the deep Gulf, and which is exposed to periodic disturbance and recolonization, possibly influenced by slightly corrosive bottom-waters. Low -C r.ro Assemblage (F5+) Cassidulina subglobosa and Nuttallides decorata are the most strongly loaded (positive) species on Factor 5. Nuttallides decorata has consistently high relative abundances (10%) at most stations, but has very high abundances (> 20%) at a few shallow (1500-1700 m) and one deep (3800 m) station. This pattern is clearly depicted by the location of stations with strong positive scores associated with this factor (Fig. 47). Although Nuttallides decorata maintains high relative abundances at most stations, it reaches peak abundances at lower bathyal stations. Nuttallides decorata is typically a lower bathyal to abyssal species in the Gulf of Mexico and Caribbean (Pflum and Frerichs, 1976; Poag, 1981; Sen Gupta and Aharon, 1987; Galluzzo, 1989; Murray, 1991) and is usually prevalent in sediments bathed by oxygenated waters with low Corg (Lagoe et al., 1994; Jones and Sen Gupta, 1995). Nuttallides decorata was reported as frequently misidentified as Nuttallides umbonifera in the eastern Caribbean (Sen Gupta et al., 1982; Gaby and Sen Gupta, 1985) by Sen Gupta and Aharon (1987). Living Nuttallides umbonifera tolerates corrosive bottom waters (Mackensen et al., 1990) and its distribution has been reported by numerous workers to be related to carbonate-undersaturated Antartctic Bottom Water (AABW; Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Streeter, 1973; Lohmann, 1978; Hermelin, 1989; Murray, 1991; Mackensen et al., 1995). Mackensen et al. (1990) describe a potential fossil assemblage characterized by Nuttallides umbonifera that reflects an AAB W-like water mass in a zone below the carbonate lysocline but above the CCD. The depths at which Nuttallides decorata is most prevalent in the GOM suggest that bottom-water corrosivity may play only a minimal role in its distribution, since large-scale influx of AABW into the Caribbean, hence Gulf of Mexico, is restricted by sill depths (Galluzzo,1989), however, its preference for low' Corg fluxes (Fig. 49) may be the most critical factor to its distribution. Cassidulina subglobosa is a cosmopolitan species in the GOM and is reported from water depths between 40-3614 m (Pflum and Frerichs, 1976; Murray, 1991). Despite its ubiquitous distribution, moderate to high abundances of Cassidulina subglobosa have proven useful as environmental indicators. Streeter and Shackle ton (1979) related its distribution to NADW in the North Atlantic. It dominates assemblages associated with AABW along ridge crests and flanks in the southeastern Indian Ocean (Corliss, 1983), generally above carbonate-corrosive w'aters. Mackensen et al. (1995) infer that Cassidulina subglobosa-domma.tcd assemblages are opportunistic, in a sense, because they flourish in regions with low' Corg (<1 gCm-2yr-l), high bottom-current velocities, and non-corrosive bottom waters, conditions which are unsuitable for other opportunistic species. The association of these species reflects an assemblage able to tolerate low COTg. Reduced-Cb assemblage (F2+) Bolivina albatrossi, Osangularia culler, O. rugosa, and Gavelinopsis translucens all exhibit very high postive loadings on Factor 2. Bolivina albatrossi is reported in the Gulf of Mexico, most commonly, from upper to middle bathyal depths in the Brizalina albatrossi association and as a constituent of several other shelf and slope associations Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125 1.1-1 • 1.0- • /_K • • £ 0.9- • • • • • • o u © 00 • H • 0.7- < 0.6-1 ...... r i -...... — i i i i 0 10 20 30 40 Nuttallides decorata (%) Figure 49. Plot of Corg against percentage of Nuttallides decorata, showing a trend of increasing relative abundance of N. decorata with decreasing Corg. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 126 by Murray (1991), as well as from the upper bathyal zone by Pflum and Frerichs (1976). Lagoe et al. (1994) found it associated with a weak oxygen minimum biofacies and high organic carbon flux. Moreover, Gary (1985) suggested that it adapts to low' oxygen environments by developing more test pores. Within the study area, Osangularia culler, O. rugosa and Gavelinopsis translucens are most abundant at stations from water depths ranging between 2000-2400 m (Jones and Sen Gupta, 1995). Osangularia culler has been reported in association with water masses, in particular Subantarctic Intermediate Water (SAIW; 700-1000 m), that are poorly- oxygenated and have reduced salinities (Denne, 1990). Like Bolivina albatrossi, O. culler was found as a constituent of several neritic and upper bathyal species associations (Murray, 1991). However, Osangularia culter may be eurybathyic since it has been reported from middle bathyal to abyssal depths (Pflum and Frerichs, 1976), and as a common constituent of the lower bathyal and abyssal Nuttallides decorata association of Murray (1991). Pflum and Frerichs (1976) reported Osangulariarugosa from upper bathyal depths. Gavelinopsis translucens was reported by Denne (1990) as abundant in sediments associated with Oxygen Minimum Water (250-650 m), as well as with a secondary oxygen minimum zone. The putatively epifaunal habitats for Osangularia culter, O. rugosa and Gavelinopsis translucens (Denne and Sen Gupta, 1989) suggest that these species are responding to bottom-water oxygen content, whereas Bolivina albatrossi, an infaunal species, may be responding to pore-water oxygen content. Nonetheless, these species as a group seem to be able to tolerate low oxygen levels, whether in bottom- or pore-water. Factor 2 species described previously are associated with some level of reduced oxygen content and are typically reported from water depths much shallower than those of the study area. Only two samples score highly on factor 2. These are from Area 1, the Orca Basin region (Fig. 5), which has the highest sediment accumulation rates of the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. study area. The tremendous influx of terrigenous sediments in Area 1, which also may include high levels of Corg (the degradation of which may reduce oxygen content), would favor the proliferation of these low-oxygen species. Although these species clearly represent a reduced O2 assemblage, their presence at much deeper water depths, and their dominance in only two samples from the Orca Basin suggest that this assemblage may reflect downslope sediment transport High/Episodic Productivity Assemblage (F4+) Three infaunal species exhibit strong positive loadings on Factor 4: Bulimina aculeata, Buliminamarginata, and Uvigerinaperegrina. Buliminamarginata has been found associated with low oxygen and high Corg in the Mediterranean (Jorrissen, 1988) as well as off the coast of Yugoslavia (Cimmerman et al., 1988). Although reported by Lagoe et al. (1994) in the Gulf of Mexico from depths between 1200-2100 m with decreasing COTo flux, Bulimina aculeatahas more frequently been found associated with relatively high Corg or episodic pulses of increased productivity (Lutze and Coulbourn, 1984; Mackensen et al., 1990, 1995; Ishman et al., 1996). Bulimina aculeata in association with Uvigerinaperegrina, both low-oxygen species, have been documented from the Caribbean (Galluzzo, 1989). Uvigerinaperegrina has been frequently reported from areas of high COTg flux to the seafloor (Altenbach, 1988; Loubere et al., 1993b, 1995; Lagoe et al., 1994), of elevated Corg in sediments and of low-oxygen conditions (Miller and Lohman, 1982; Poag, 1984; van Morkhoven et al., 1986; Corliss 1979; Corliss et al., 1986; Lutze and Coulbum, 1984). Mackensen et al. (1995) report Uvigerinaperegrina associated with two "Productivity and Organic Carbon Flux” assemblages: 1) the "high-productivitv" assemblage, and 2) the "phytodetritus" assemblage. Although often reported as low-oxygen species, Bulimina aculeata and Uvigerinaperegrina may, in addition, reflect episodic high Corg fluxes to the seafloor. Most stations with high positive scores on Factor 4 (Fig. 46) are found along the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128 lower slope in Area 2, the area with the lowest sediment accumulation rates. The success of Bulimina aculeata, B. marginata, and Uvigerinaperegrina in this area may be related to their infaunal habitat and their ability to adapt to episodic influxes of organic matter, both of which are effective strategies in an area with such low sediment accumulation rates. Organic matter type does not seem to play a defining role because stations with high positive scores on Factor 4 fall within the marine and the mixed- source organic carbon realms (Fig. 8). Mixed Assemblage (F3+) Four species show strong positive loadings on Factor 3: Cibicides bradyi, Hansenisca regularis, Laticarinina pauperaia, and PuUenia bulloides. Cibicides bradyi and Laticarinina pauperataaxe reported from middle bathyal to abyssal depths, whereas Hansenicaregularis is found much shallower in upper bathyal depths (Pflum and Frerichs, 1976). Both Cibicides bradyi and Laticarinina pauperataare reported in associations defined by Cibicides wuellerstorfi and Globocassidulina subglobosa (Murray, 1991). Denne (1990) linked Laticarinina pauperaia with CMW (1000-1500 m). He also reported that Hansenicaregularis is common in Gulf Water and the Oxygen Mininimum zone (both shallow water masses), attaining its highest average abundances (to > 10%) adjacent to the delta, possibly indicating tolerance for high or terrigenous organic matter concentrations. In the Caribbean, Bommalm (1992) found it associated with key indicator species for NADW since the late Neogene. Pullenia bulloides is reported from neritic depths in the Gulf of Mexico (Pflum and Frerichs, 1976). However, on the Atlantic seaboard, Phleger et al. (1953) reported it from abyssal depths. Corliss (1983) reported it in the Indian Ocean from depths between 1600-3800 m, and associated with Cibicides wuellerstorfi and Globocassidulina subglobosa. Galluzzo (1989) also noted this association, Pullenia bulloides with Cibicides wuellerstorfi, in the Grenada Basin. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129 In the Ontong-Java Plateau area, Pullenia bulloides dominates assemblages associated with Pacific Deep Water and is inferred to reflect reduced oxygen conditions with episodes of upwelling (Heimelin, 1989). Mackensen et al. (1985) report living Pullenia bulloides as a dominant constituent of an assemblage occupying slope regions covered with fine-grained, organic-rich, terrigenous mud. Samples that scored highly on this factor are from the far western portion of the basin (Fig. 45), where the organic matter is of predominantly marine origin. The widely varying sample depths and inconsistent environmental preferences of species comprising this assemblage suggest sediment mixing. NADW/CMW Assemblage (F6+) One species, Cibcides wuellerstorfi, has strong positive loadings on Factor 6. This species is commonly considered water-mass dependent, and a key indicator of NADW in several ocean basins (Murrary and Weston, 1984; Schnitker, 1984; Sen Gupta, 1988; Bommalm, 1992; Mackensen et al., 1995; Ishman et al., 1996). In addition to its strong association with a water mass, it has been reported to be well adapted to low annual flux of organic carbon (Altenbach, 1988; Murray, 1991), and to be present in the Mississippi Fan, which has a high sediment accumulation rate and is rich in terrestrial organic detrims (Poag, 1981). Mackensen et al. (1985) find abundances of Cibicides wuellerstorfi positively correlated to relatively coarse (i.e., sand fraction dominated by planktic foraminifera) and organic-rich sediments suggesting a high-productivity connection. This C. wullerstorfi-domimted assemblage, revealed by Factor 6, probably represents a weak modem NADW signal in the northwestern Gulf. This weak signal is a result of the influx of Caribbean renewal waters, which contain an NADW component as shown by the relative abundances of C. wuellerstrofi in the eastern Caribbean (Sen Gupta, 1988). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 130 Oxygen-Sensitive Assemblage (F6-) Alabaminella turgida has strong negative loadings on Factor 6. Alabaminella turgida is a highly oxygen-sensitive species (Pflum and Frerichs, 1976; Denne, 1990), and is most common from bathyal and abyssal depths. Poag (1981) reported it as abundant from the Sigsbee and Florida Plains, both commonly associated with slow sedimentation rates, increased CaCC>3, and mainly marine organic matter; he found it in lower abundances in facies adjacent to the Mississippi Fan. Lagoe et al. (1994) found it associated with decreasing organic carbon flux to the seafloor. Since most of the study area is bathed by well-oxygenated bottom-waters, the persistently high, ubiquitous abundances of Alabaminellaturgida are not unusual. Preservation Assemblage (F4-) Only one species, Hoeglundina elegans, has a strong negative loading on Factor 4. Hoeglundina elegans , is most commonly reported from bathyal to abyssal w ater depths, although Pflum and Frerichs (1976) found it most common in neritic waters in the Gulf of Mexico. Poag (1981) reports scattered occurrences from the shelf to the Sigsbee Plain, and Lagoe et al. (1994) find it characteristic of water depths between 100-2134 m. This assemblage may reflect a preservation factor either in less-corrosive bottom waters unable to dissolve a more robust (thick) aragonitic test. A more feasible explanation may be rapid burial so that shells are removed from exposure to waters undersaturated with respect to aragonite. Environmentallv-Stressed Assemblage (F5-) Bolivina lowmani is the only species with a strong negative loading on Factor 5. Most other species that have (weak) negative loadings are agglutinated. Relative abundances of Bolivina lowmani are high (typically 20%, in some cases 40-70%) and somewhat erratic within the study area. Bolivina lowmanis rather ubiquitous distribution, being reported from shelf waters to the Sigsbee Plain (Poag, 1981), and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. often very high relative abundances may, in part, reflect its meroplanktonic phase (Hueni et al„ 1978). It has also been associated with fine-grained substrates and relatively high sedimentation rates (Lankford, 1959; Sen Gupta et al., 1981; Galluzzo, 1989) both of which are prevalent in the study area. However, its absolute abundance is relatively constant (< 20 individuals/g sediment) suggesting that the high relative abundances occur because other species cannot readily adapt to the environmental conditions. Consequently, the very high abundances of Bolivim lowmani, which characterize this assemblage, may be indicative of stressed environmental conditions as was suggested by McLaughlin and Sen Gupta (1994) in the Azua Basin. Cluster Analysis Q-mode cluster analysis of abundance data (Ward's Minimum Variance Method) for 26 species from 27 core-samples revealed six clusters (Fig. 50) related to somewhat overlapping environmental parameters, and which broadly comprise two depth zones. These six clusters are characterized by species that define assemblages identified by factor analysis. The geographic distribution of biofacies reflected by these six clusters is quite distinct, despite some overlap (Fig. 51). Depth Zone A Depth zone A, which includes clusters 1 and 2, defines a lowermost bathyal to abyssal biofacies, in water depths from 2700-3900 m, confined to the lowermost slope and abyssal plain (Area 3). Stations in depth zone A contain the highest average abundances of agglutinated taxa in addition to high abundances of several calcareous species: Bolivina lowmani, Alabaminella turgida, Ioanella tumidula, and Gyroidinoides polins. This cluster reflects a mixed-calcareous and agglutinated assemblage similar to the Mixed Agglutinated-Calcareous Assemblage identified by factor analysis (F1+). The high abundances of Alabaminella turgida and Bolivina lowmani in this assemblage are not unique; these two species in addition to Nuttallidesdecorata exhibit these very Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hierarchical Clustering Method = Ward’s Minimum Variance Map Water Sample # depth numbers 29 2700 BC-3 3 2905 PC-1 7 3632 PC-5 Zone 4 2881 PC-2 30 3550 BC-4 5 3850 PC-3 28 3500 BC-8 31 1750 BC-7 10 1538 IG-38-10 I > 8 2324 IG-41-23 17 2180 IG-46-8 2 2199 IG-41-21 13 1972 IG-41-28 26 2002 IG-41-24 15 1856 IG-46-11 24 2097 IG-46-12 9 2231 IG-41-26 Zone 23 1786 IG-38-18 *'• ‘ r\ /• 4* *. ^L f 20 1616 IG-41-18 *r2 *t> '* ^ T’Vrv 22 1584 IG-41-19 j* Figure 50. Dendrogram from Q-mode cluster analysis of core-top samples showing a depth separation of samples, and six sample groupings within lower bathyal and abyssal depth zones. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. U> U> Biofacies Distribution Biofacies Figure51. Mapshowing distribution ofsix lower bathyal and abyssal biofacies identified by Q-mode clusteranalysis. Assemblagesthat characterize these biofacies wereindentified R-modeby factoranalysis. I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 134 high abundances in all 27 samples. These persistently high abundances across all samples (i.e., water depths) preclude them from being helpful as environmental indicators within the deep GOM, except in extreme cases where they reach acme proportions. The separation of most clusters, then, is characterized by the most abundant taxa after these species. Several agglutinated species, and Ioanellatumidula and Gyroidinoides polius are the defining taxa for this depth zone. Cluster 1—Lowermost Slope Biofacies Stations included in cluster 1 are from water depths between 2700-2900 m, with one exception, station PC-2 (an outlier) from 3632 m of water. This Lowermost Slope Biofacies is located in A rea3, which is influenced by predominantly marine organic carbon (Figs. 1,3, and 8). These stations contain an assemblage differentiated from cluster 2 by lower abundances of agglutinated species and the highest average abundances of Cibicides wuellerstorfi (in any cluster). Hoeglundina elegans is present in rare to low abundances at cluster 1 stations, although its highest abundances within the study area occur in the lower bathyal realm (depth zone B). This biofacies reflects the NADW/CMW Assemblage (F6+) and the Mixed Agglutinated-Calcareous Assemblage (F1+). Cluster 2—Sigsbee Plain Biofacies Stations comprising cluster 2 are from water depths > 3000 m (Fig. 50), and are located in an area influenced by predominantly marine organic carbon, as were cluster 1 stations. This biofacies lies entirely on the Sigsbee Plain (Fig. 51). Cluster 1 stations most closely reflect the assemblage of depth zone A, characterized by several agglutinated species, and Ioanellatumidula and Gyroidinoides polius of the Mixed Agglutinated-Calcareous Assemblage (F1+). The scarcity of Hoeglundina elegans at these stations may indicate a degree of bottom-water corrosivity in the deepest Gulf basin. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135 Depth Zone B Depth zone B includes the remaining clusters (3 to 6; Fig. 50) and defines a biofacies confined to the uppermost lower slope (Fig. 51), overlain by waters 1500- 2400 m deep (Areas 1, 2 and 3). In stations of depth zone B, the agglutinated taxa are significantly reduced (averages generally < 1%), and Cassidulina subglobosa, Osangularia culler , Bulimina aculeata, Bolivina albatrossi and Epistominella exigua are more abundant than in stations of depth zone A. In addition, these stations show high abundances of Alabaminella turgida , Bolivina lowmani , and Nuttallides decoram , as is seen in depth zone A. The dearth of agglutinated taxa and the notably higher abundances of Cassidulina subglobosa, Osangularia culler, Bulimina aculeata, Bolivina albatrossi and Epistominella exigua, the defining taxa for this depth zone, represent two assemblages identified by factor analysis: 1) the Reduced-02 Assemblage (F2+), and 2) the High Productivity Assemblage (F4+). Cluster 3—Environmentally-Stressed Lower Bathyal Biofacies Cluster 3 contains stations from water depths of 1500-2300 m, and the biofacies it represents has a disjunct geographic distribution in areas of both marine and mixed- source organic carbon (Areas 1 and 3; Figs. 1, 3, 5, 50, 51). Most stations in cluster 3 are characterized by unusually high abundances (39-45 %) of Bolivina lowmani , and thus reflect the Environmentally-Stressed Assemblage (F5-) identified by factor analysis. Stations in this cluster exhibit the lowest species diversity and equitability values (average H(S)= 2.37 and E =0.65) in the study area, indicating a greater species dominance in this biofacies relative to other study sites. Moreover, low diversity and species dominance are often indicative of stressed environments. Cluster 4—Orca Basin Area Biofacies Cluster 4 includes stations from water depths of 1800-2200 m and its biofacies is restricted to Area 1, the Orca Basin region (Fig. 51). This area is characterized by high Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136 rates of sediment accumulation and is associated with mixed-source organic carbon. These stations contain the highest average abundances of Alabaminella turgida and Hoeglundina elegans in the study area, with high abundances of Cassidulina subglobosa and Nuttallidesdecorata. This cluster reflects overlap of the Low-COTg Assemblage (F5+-), the Preservation Assemblage (F4-), and the Oxygen-Sensitive Assemblage (F6-). The high percentages of Hoeglundina elegans at stations in this area suggest that high sediment accumulation rates do not allow long-enough exposure at the sediment- water interface for dissolution to occur. Such high sediment accumulation rates often result in relatively high COTg content, and may preclude proliferation of Cassidulina subglobosa and Nuttallidesdecorata, both of which define the Low COTg Assemblage. However in this instance, the Nuttallidesdecorata-Cassidulina subglobosa association, may, instead, reflect a preference for terrigenous organic carbon (Jones and Sen Gupta, 1995), rather than, or in addition to, low Corg. Cluster 5—Lower Bathyal Biofacies Stations in cluster 5 range in water depth between 1500 and 1900 m, and are from a laterally extensive E-W trending biofacies along the uppermost lower continental slope in Areas 1 and 2 (Figs. 5 and 51). These stations lie primarily within the zone of mixed-source Corg in areas of both high and low sediment accumulation rates. Cluster 5 samples contain the highest average abundances of Nuttallidesdecorata and Bulimina aculeata , with moderate abundances of Cassidulina subglobosa and Alabaminella turgida. This Lower Bathyal Biofacies reflects the overlap of three assemblages: 1) the Low Corg Assemblage (F5+), 2) the High/Episodic Productivity Assemblage (F4+), and 3) the Oxygen-Sensitive Assemblage defined by Alabaminellaturgida (F6-). C luster 6 — Environmentally-Mixed Biofacies Two stations, IG-45-9 and IG-46-9, were grouped to form this cluster (Fig. 50). These stations, from a narrow depth range (2300-2400 m, are from the Orca Basin, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137 which does not typically support an indigenous benthic fauna (Lagoeetal., 1994). Five species characterize these stations with their highest abundances: Osangularia culler, 0. rugosa, Bolivina albatrossi, Gavelinopsis translucens, and Epistominella exigua. Two common species exhibit anomalously low abundances: Alabaminella turgida and Bolivina lowmani, both of which have persistent high abundances in all other samples, and several species, all characteristic of deep Gulf basin waters, are absent: the agglutinated taxa, and Ioanella tumidula, and Gyroidinoides polius. The low abundance of Alabaminella turgida and Bolivina lowmani, and the absence of the characteristic deep-water species, all of which would be expected, in some degree in an indigenous assemblage, suggest that these samples reflect downslope transport. Furthermore, the species that characterize this biofacies are typical of shallower, upper to middle bathyal, depths (Pflum and Frerichs, 1976; Denne, 1990; Murray, 1991). Species characterizing samples from this cluster reflect the Reduced Oo Assemblage (F2+) identified by factor analysis. Downcore Distributions of Benthic Foraminifera Benthic foraminiferal distributions from 64 samples (2-2.5 cm intervals) from two lower bathyal (BPX-1 and BPX-10) and two abyssal (PC-1 and PC-2) piston cores were used to examine bottom-water fluctuations and paleoenvironmental variations through the transition from the Last Glacial Maximum (LGM) and interval of meltwater (MW) influx through the Holocene. Downcore plots of species diversity trends and of dominant species relative abundances were examined to compare lower bathyal and abyssal depth intervals, and glacial-interglacial intervals. In addition, Q-mode cluster analysis (see core-top study) on relative abundance (%) data from 59 samples (five samples were removed because of low foraminiferal numbers) was used to delineate benthic foraminiferal biofacies (Appendix 4). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 138 Species Diversity Trends Measures of species diversity calculated for cores BPX-10, BPX-1, PC-1 and PC-2 (Table 13) are generally high, and show an overall trend of decreasing diversity with increasing water depth from the lower bathyal to the abyssal realm. For the lower bathyal cores, H(S) ranges from 2.29-3.41 with an average of 2.93, S ranges from 30- 46 with an average of 38, and E ranges from 0.67-0.90 with an average of 0.80. For the abyssal cores, H(S) ranges from 1.65-2.91 with an average of 2.28, S ranges from 17-40 with an average of 27, and E ranges from 0.47-0.88 with an average of 0.70. The two shallowest cores, in particular BPX-10, exhibit little temporal variation in species diversity and equitability (Fig. 52). In contrast, the abyssal cores show more variability (Fig. 53), particularly related to the deglacial transition. In both PC cores, but most conspicuous in PC-2, a decrease in species diversity and equitability begins in the latest Pleistocene Y1 subzone (Fig. 53). Species diversity and equitability fluctuate throughout the early and middle Holocene Z zone, and then begin to increase in the latest Holocene, approaching high values similar to those of the last glacial maximum (Y2-Y3 subzones). Species diversity and equitability are highest in core PC-2 during full-glacial conditions and the latest Holocene interglacial, and are lowest and exhibit more flux during the glacial-interglacial transition (Fig. 53). Dominant Species Abundances Downcore plots of 32 abundant, and/or environmentally significant species and species groups reveal several depth-related and temporal variations. Bulimina aculeata, B. mexicana, B. spicata, Uvigerina peregrina, U. hispidocostata, Paianotua sp. cf. P. lerebra, Gavelinopsis translucens, Martinottiellaoccidentalis, and Sigmoilopsis schlumbergeri are present in low to moderate abundances (3-10%) only in the lower bathyal cores and are rarely present in the abyssal cores (Fig. 54,55, 56). In contrast, Ioanella tumidula, Melonis pompiloides, Cibicides wuellerstorfi, Siphotextularia affinis Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 139 Table 13. Downcore Species Diversity Measures for Lower Bathyal and Abyssal Stations. H(S), Shannon-Wiener Information Function, S, number of species in sample, and E, species equitability. Sample H(S) s E Sample H(S) S E PC2-1 5 2.4638 23 0.79 BPX1-25 2.5851 36 0.72 PC2-20 2.3012 24 0.72 BPX1-55 2.7692 38 0.76 PC2-30 2.2075 20 0.74 BPX1-80 2.8235 38 0.78 PC2-40 1.9550 21 0.64 BPX1-10S 2.5443 30 0.75 PC2-S0 1.8133 22 0.59 BPX1-115 3.0562 45 0.80 PC2-60 1.7434 19 0.59 BPX1-145 2.6146 32 0.75 PC2-90 1.6543 22 0.54 BPX1-160 2.5680 32 0.74 PC2-100 1.4885 23 0.47 BPX1-175 3.0118 40 0.82 PC2-11 0 1.9035 25 0.59 BPX1-205 2.6915 38 0.74 PC2-1 20 1.8754 23 0.60 BPX1-235 2.7576 41 0.74 PC2-130 2.1312 24 0.67 BPX1-260 2.0790 32 0.60 PC2-140 2.0029 17 0.71 BPX1-290 3.0932 41 0.83 PC2-155 1.6837 22 0.54 BPX1-315 2.2993 31 0.67 PC2-180 2.3204 24 0.73 Mean 2.6841 36 0.75 PC2-200 2.6215 26 0.80 PC2-215 2.5139 22 0.81 BPX10-25 3.4055 46 0.89 PC2-260 2.5229 24 0.79 BPX10-55 3.3555 44 0.89 PC2-300 2.3436 18 0.81 BPX10-85 3.3206 41 0.89 PC2-320 2.6039 25 0.81 BPX1 0-115 3.1054 40 0.84 PC2-380 2.5517 18 0.88 BPX1 0-1 40 3.3307 42 0.89 Mean 2 .1 3 5 1 22 0.69 BPX1 0-185 3.0987 38 0.85 BPX10-215 3.3102 46 0.86 P C I-to 2.7194 35 0.76 BPX10-245 3.2127 36 0.90 PCI-20 2.7900 40 0.76 BPX10-26 0 3.3026 43 0.88 PCI-40 2.9064 32 0.84 BPX10-29 0 3.0429 33 0.87 PCI-6 0 2.4673 32 0.71 Mean 3 .2 4 8 5 41 0 .8 8 PCI-80 2.5994 33 0.74 P C I-too 2.2675 28 0.68 Mean Lower Bathyal 2 .9 2 9 5 3 8 0 .8 0 PCI-1 1 0 2.3434 23 0.75 PCI-1 20 2.2143 25 0.69 PCI-1 4 0 2.3316 24 0.73 PCI-1 60 2.3999 29 0.71 PCI-20 0 2.1670 23 0.69 PCI-24 0 2.4121 33 0.69 PCI-2 60 2 .60 36 30 0.77 PCI-2 80 2.3725 31 0.69 PCI-300 2.6289 33 0.75 PCI-320 2 .50 46 31 0.73 PCI-340 2.2098 36 0.62 PC1-360 1.9125 32 0.55 PCI-380 2.1335 31 0.62 PCI-40 0 2.4901 35 0.70 PCI-440 2.2464 30 0.66 Mean 2.41 5 3 31 0.71 Mean Abyssal 2 .2 7 8 6 2 7 0 .7 0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - - ^ 72 7.1 Y4 > > >* Y3 1 6 ^ 3 -- 5^-2 f I£ BPX-1 ------I . \ ------) ) 0.5 - Z2 /.I Y3 Y4 Y2 1 s ---- f4 V* S H(S) L_ L_ 1 1 H(S) C H(S) -- BPX-1 1 - , ' 1 ' 1 '"I--' 1 ■ ------0 10 20 30 40 0 50 40 30 20 10 0 0 1 2 3 Z1 Z2 Y4 Y2 Y3 0.5 BPX-10 Species Diversity & Equitability Z1 Z2 Y4 Y2 Y3 -v+- _ H(S) 2 2 3 4 -j -j i H(S) 1 BPX-10 i ■ i i ■ i * i ■ 0 10 20 30 40 0 50 40 30 20 10 - 200 400 800- 600- (000 Figure 52. Downcore plots ofspecies diversity measures for lower bathyal stationsshowing generally high species diversity little temporal with variation. a V o A U Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 141 >« >- ’o CO8. JG N 00 i m \ // 12 u ® eu *2.CO S3 « "■ O' U S? H <2 § co — S O O 2 3C b.<« O) S ” s*- U) u S 2 cn & > «j *3 =3.8 SJ co w a O 00 tZ) o c 8.'g © ° a «o CO o _ o ■§ * Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bulimina aculeata, B. mexicana, & B. spicata BPX-10 BPX-1 PC-1 0 5 10 15 5 10 15 5 10 15 Z1 Zl Z2 : e Z2 -XL. Y2 Y2 Zl 20 0 - r Y3 Y3 Y4 & Y4 Z2 400- Y1 Y2 600- 800- 1543 m 1815 m 2905 m 1000 Uvigerina peregrina Gavelinopsis translucens & U. hispidocostata & Paumotua sp. cf. P. terebra BPX-10 BPX-1 BPX-10 BPX-1 0 5 10 10 0 5 10 0 5 10 zi ZL Z l Zl 1 2. 72 Z2 .XL Z2 ____— 4* ____ -Yt— Y2 Y2 Y2 Y2 200 - > . v ' Y3 Y3 Y3 Y3 ' ■*--4 Y4 * > Y4 Y4 Y4 400- 600- 800- 1543 m 1815 m 1543 m 1815 m 1000 Figure 54. Percentage plots of benthic foraminiferal species characteristic of lower bathyal stations and rare to absent in abyssal stations against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143 IoaneUa tumidula BPX-10 BPX-1 PC-1 PC-2 5 10 15 20 5 10 15 20 5 10 15 20 5 10 15 20 i • 1— ^ -1 - Z l 7,1 > 7.2 Z2 f Y1 ■ iff 2 2. Y2 Y2 Zl 2 0 0 - Y3 Y3 Y2 Y4 Y4 Z2 400- Y1 Y3 Y2 600- 800- 1543 m 1815 m 2905 m 3632 m 1000 - EggereUa bradyi & Martinottiella occidentalis BPX-1 pc-1 PC-2 zi Z l 22. Z2 VI -Yt- Y2 Y2 2 0 0 - Y3 Y3 Y4 Y2 Y4 Z2 400- Y3 Y2 600- 800- 1543 m 1815 m 1000 2905 m 3632 m Figure 55. Percentage plots of benthic foraminiferal species characteristic of abyssal stations and associated with NAIW against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 144 Glomospira charoides, Karrerutina apicularis, & SpiroplecteUa cylindroides BPX-10 BPX-1 PC-1 PC-2 IS i s Z l ___ _ Z2 Y2 Y1 200 Y2 Y3 Y3 Y2 Y4 Z2 Y4 Y3 400- Y1 Y2 600- 800- 3632 m 1543 m 1815 m 2905 m 1000 Siphotextularia affinis & Sigmoilopsis schlumbergeri BPX-10 BPX-1 PC-1 PC-2 0 5 10 10 5 10 5 10 Zl 22. Zl Z2 XL 3 * S'* % 72 Zl Y2 Y2 Y1 2 0 0 - ■*; ijIT-** Y3 Y3 o Y2 Y4 Y4 * Z2 1! 400- - &-'• Y1 J > • Y3 ck- Y2 600- - 1543 m 1815 m 2905 m 3632 m 1000 Figure 56. Percentage plots o f several agglutinated foraminiferal species against core depth (cm) generally with Glomospira charoides, Karrerulina apicularis and SpiroplecteUa cylindroides showing their highest abundances in the upper portions of all cores, and Siphotextularia affinis and Sigmoilopsis schlumbergeri showing their highest abundances in the abyssal and lower bathyal cores, respectively. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 145 and Bolivina lowmani are present only in, or exhibit their highest abundances in, the abyssal cores (Figs. 55, 56, 57, 58, 62). Two species, Alabaminella turgida and Nuttallidesdecorata, exhibit consistently high abundances (10-20% and 5-35%, respectively) in both lower bathyal and abyssal cores as well as throughout both glacial and interglacial intervals (Fig. 58). However, Alabaminella turgida reaches its highest abundances (-50%) in a peak during the latest Pleistocene Y 1 subzone in both abyssal cores and the Y3 subzone in BPX-1 core. Although Nuttallidesdecorata exhibits markedly lower abundances, in the shallowest core BPX-10, relative to the other three cores, 2-10% as opposed to 10-40%. Cibicides bradyi is consistently present in low to moderate abundances (2-8%) in the lower bathyal cores and the shallowest abyssal core (Fig. 61), and it is rare in the deepest abyssal core. A few species exhibit their highest abundances in the latest Pleistocene. Eggerella bradyi, Quinqueloculina venusta, and the Oridorsalistener species group (Figs. 55, 56, 59) show consistent and markedly higher abundances (2-7%, 3-25%, and 5-14%, respectively) throughout the Y zone as opposed to the Holocene Z zone (<3 %, <2% and 0-6%, respectively). Four species exhibit one or more isolated abundance peaks during the last glacial Y zone. In the Y 1 subzone, Alabaminella turgida and Globobulimina affinis (Figs. 58,61) reach abundance peaks, whereas in the Y2 and Y3 subzones, Quinqueloculina seminula, Q. spp, and Biloculinella irregularis (Figs. 59, 60) reach peak abundances. Several species are typical of the Holocene. The more fragile agglutinated species, Glomospira charoides, Karrerulina apicularis and SpiroplecteUa cylindroides (Fig. 53), are present only in the latest Holocene samples of all cores. Gyroidinoides polius reaches its highest abundances (to 10-25%) in the latest Holocene samples as well (Fig. 57). Bolivina lowmani attains its maximum abundance (25-60%) in the middle Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 146 Oridorsalis tener species group BPX-10 BPX-1 PC-1 PC-2 5 10 15 5 10 15 10 15 5 10 15 . » ■ - t — - .. i . . i .. ._ Zl S" A_ ------72 Zl Z2 ..XL. ------^ ------.12. Z l Y2 Y2 f Y1 2 0 0 - X Y3 Y3 > . Y2 Y4 Y4 Z2 400- Y1 Y3 Y2 800- 1543 m 1815 m 2905 m 3632 m 1000 Cibicides wuellerstorfi & Gyroidinoides polius BPX-10 BPX-1 PC-1 PC-2 10 20 30 10 20 30 10 20 30 10 20 30 . .. j— i 1--- 1--- L. 0- zi Zl 22. Zl Z2 XL -Yt— 22. Y2 Y2 Z l Y1 200- c * m Y3 Y3 Y2 Y4 Y4 Z2 Y3 400- Y1 Y2 600- 800- 1543 m 1815 m 2905 m 3632 m nnn. Figure 57. Percentage plots of three watennass associated benthic foraminifera, the Oridorsalis tener species group (NAIW), Cibicides wuellerstorfi (NADW) and Gryoidinoides polius (CMW/NADW) against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147 Alabaminella turgida & Bolivina lowmani PC-2 BPX-10 BPX-1 PC-1 20 40 60 20 40 60 20 40 60 20 40 ---i ---1. . 1 . Z l Z2 Z2 Y2 * t5 j - Z l Y1 200 - Y2 Y3 Y3 Y2 Q> Y4 Z2 Y4 - ♦ Y3 400- r Y1 ♦ ^ Y2 600- - 800- ” 1543 m 1815 m 2905 m 3632 m 1000 Nuttallides decorata & Cassidulina subglobosa BPX-10 BPX-1 PC-1 PC-2 0 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 -» - l - ' ■___L ■ , . i . i ♦ o Zl Zl -ZZ. Zl o Z2 XL =fc= <5*=- 2 2. Z l £ Y2 % Y2 200 - v v XL Y3 Y3 ► * Y2 Y4 Y4 Z2 400- s r : ■* Y1 © ♦ Y3 IT Y2 600- 800- 1543 m 1815 m 2905 m 3632 m 1000 Figure 58. Percentage plots of Alabaminella turgidus, Bolivini lowmani, Nuttallides decorata, and Cassidulina subglobosa against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 Quinqueloculina venusta, Q- seminula, & Q. spp. BPX-10 BPX-10 BPX-1 BPX-1 0 5 10 0 5 10 o 5 10 o 5 10 Zl 21 21 Z2 Z2 XL Y2 Y2 Y2 Y2 2 0 0 - Y3 Y3 Y3 Y4 Y4 Y4 Y4 400- 600 MO- 1543 m 1543 m 1815 m 1815 m 1000 PC-1 PC-1 PC-2 PC-2 0 5 10 5 10 5 10 0 10 20 30 Zl Zl 200 XL Y2 Y2 Z2 Z2 Y1 Y3 Y3 Y2 Y2 600- 800- 2905 m 2905 m 3632 m 3632 m 1000 Figure 59. Percentage plots of Quinqueloculina venusta, Q. seminula, and Q. spp. against core depth (cm) showing highest abundances in glacial intervals. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. & IX Y2 Z l Y3 XL 10 3632 m PC-2 .--o 0 7 <2: against core depth (cm) showing highest Y1 Z2 Y2 10 10 0 5 2905 m PC-1 Hoeglundinaelegans Y4 Y3 z r Y2 10 10 0 5 and 1815 m 1815 Z2 Y4 Y2 Y3 BUoculinella irregularis & Hoeglundina elegans Hoeglundina & irregularis BUoculinella BUoculinellairregularis 1543 m BPX-10 BPX-1 0 0 5 10 0 5 - 600- 200 400- 800- 1000 Figure 60. Percentage plots of abundances glacial in and interglacial intervals, respectively. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 150 Globobulimina affinis BPX-10 BPX-1 PC-1 PC-2 0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 Zl ZL 22 Z l Z2 -¥*- 200 Y2 Z l Y1 Y3 Y3 Y2 Y4 Y4 Z2 Y3 Y2 600 800 1543 m 1815 m 2905 m 3632 m 1000 Cibicides bradyi & Osangularia culter BPX-10 BPX-1 PC-1 PC-2 0 5 10 o 5 10 0 5 10 o 5 10 Z l Zl 22. Zl 7.2 Y2 Y2 Zl 20 0 - V Yl Y3 Y3 Y2 Y4 Y4 Z2 I 400- Y1 \ Y3 Y2 600- 800- 1543 m 1815 m 2905 m 1000 3632 m Figure 61. Percentage plots of Globobulimina affinis, Osangulariaculter, and Cibicides bradyi against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 151 Melonis pompilioides & Epistominella exigua BPX-10 BPX-1 0 5 10 0 5 10 Z l Z2 XL Y2 200 - 200 Y3 Y3 Y4 Y4 400- 400- 600- 800- 800- 1543 m 1815 m 1000 1000 PC-2 PC-1 PC-1 PC-2 5 10 5 10 5 10 Zl XL. Z l Y1 Y2 Y2 Z2 r Y1 Y3 Y3 Y2 2905 m 2905 m 3632 m 3632 m 1000 Figure 62. Percentage plots of Melonis pompilioides and Epistominella exigua against core depth (cm). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152 Holocene Z l subzone of the two abyssal cores (Fig. 58), then decreases steadily to some of its lowest abundances in the latest Holocene samples. In the two lower bathyal cores, Cassidulina subglobosa (Fig. 55) exhibits its highest abundances in the Holocene. Hoeglundina elegans is consistently rare to absent (<3%) in the latest Pleistocene (Fig. 60). In the Holocene, it reaches abundances to almost 10% in the lower bathyal cores and the shallowest abyssal core (2905 m). However, in the deepest abyssal core (3632 m) H. elegans is mostly absent, appearing only in 4 out of 20 samples at abundances < 1% (Fig. 60). Osangularia culler is mostly absent throughout the Pleistocene, and is present in low to moderate abundances (to 6%) in the latest Holocene of the lower bathyal cores. In the abyssal cores, it is rare to absent in the Holocene, and absent in the Pleistocene (Fig. 61). Epistominella exigua typically exhibits rare to low abundances in the two lower bathyal cores and the shallowest abyssal core (Fig. 62); it is mostly absent in the deepest abyssal core. It does, however, reach its maximum abundance (to 5%) in the middle to late Holocene in parts of both lower bathyal cores. Cluster Analyses Several Q-mode cluster analyses were performed: I) core samples from the lower bathyal and abyssal environments were treated separately to enhance recognition of temporal (glacial-interglacial) variation, because the core-top study revealed a distinct separation between lower bathyal and abyssal environments; 2) separate analysis of data from each core was performed to enhance recognition of temporal (glacial-interglacial) signal; and 3) all samples were analyzed together to examine if the depth and the glacial- interglacial signals could be separated. In addition, analyses were run using species abundances at the ^1% and s2% levels. The results of these analyses show clear distinctions between depth intervals and glacial-interglacial intervals based on dominant species relative abundances. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153 Glacial-interglacial Signal: Within-Core Analyses Cluster analyses of lower bathyal core BPX-1 show a strong glacial-interglacial separation. In both analyses (Fig. 63d, e), all the Holocene samples are grouped together (Cluster A), whereas for the Pleistocene samples, each analysis groups them somewhat differently. The dendrogram in Figure 63e (12 species at the >2%) shows the latest Pleistocene Y 1 samples (Cluster B) grouping together, and then joining the Holocene cluster (Cluster A). Cluster C, which is separated from Clusters A and B, is made up of full-glacial samples from subzones Y2, Y3 and Y4, indicating that the latest Pleistocene samples are more similar to the interglacial Holocene samples than to the glacial samples. The results from the 10 species at the >1% analysis are slightly different (Fig. 63d) in that the Holocene cluster (A) is separate from the Pleistocene samples, which form two smaller groups, differentiating the last glacial maximum samples (Y2) from older Pleistocene samples (Y3 and Y4 subzones). Cluster analyses of BPX-10 core show a weak glacial-interglacial signal. These analyses are not robust due to the small number of samples from this core, which severely limits the number of species (7-8) used for the analyses. The good results from the BPX-1 core suggest that with more samples a stronger glacial-interglacial signal may emerge. Analyses for the deepest abyssal core PC-2 show a strong glacial-interglacial separation. In both analyses (14 species at the >2%, and 16 species at the >1%) the latest Pleistocene Y 1 samples are grouped with the earliest Holocene samples (Cluster C; Figs. 64d, 0 and then grouped with two clusters (A and B) of Holocene samples. The full-glacial samples are grouped together (Cluster D) and later clustered with the three stratigraphically younger groups (Figs. 64d, f)- The results from PC-1 analyses are somewhat different possibly because after the removal of several samples (due to downslope transport affecting the base of the core), only four Pleistocene samples (counting the Z/Y boundary sample) remain with enough benthic foraminifera to be Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 154 Hierarchical Clustering Method = Ward’s Minimum Variance BPX1-25 BPX10-25 A BPX1-S5 BPX10-55 8PX1-105 A BPX10-140 3 - h BPX1-145 BPX10-85 BPX1-175 BPX10-115 BPX1-235 BPX10-185 B- BPX1-315 BPX10-260 BPX1-160 Bi BPX10-215 • BPX1-260 BPX10-245 BPX1-205 BPX1-BO BPX10-25 J BPX10-85 i o - c- BPX10-55 (21) BPX10-25 BPX10-115 P (22)BPX10-55 • -JY2' BPX10-140 A (Y3 BPX10-260 ■ [Y1/Y2 BPX1-115 (Y2/Y3) BPX10-215 ■ (Y2/Y3 BPX10-215 (Y3) BPX10-245 (Y4i BPX1-290 lH (Z2jBPX10-85 to BPX10-185 2/Y) BPX10-115 • Y3 BPX10-245 B i (Y2 BPX10-140 ■ Y3 BPX10-260 (Y2) BPX10-185 ■ BPX1-025' :1) BPX1-25 BPX1-055 ■ 2 BPX1-55 A' BPX1-080- A (Y4) BPX1-290 -I BPX1-105 - (Z/Y) BPX1-80 [Yi^l; BPX1-115- B- (Y1 BPX1-105 B- [Y2 BPX1-145 ‘ l£Y1/Y2) BPX1-115 Y2 BPX1-160' to ) BPX1-145 to' BPX1-205 - to)8PX1-160 Y2) BPX1-175' to BPX1-175 Y3) 8PX1-235 - c- to BPX1-235 c- Y4 BPX1-290- to BPX1-260 Y4) V4 BPX1-315 BPX1-260’ Y2) BPX1-205 ) BPX1-25 BPX1-55 BPX1-105 8PX1-115 A’ 6PX1-290 BPX10-55 ) BPX10-215 )BPX1-80 BPX10-25 BPX10-85 BPX10-115 B‘ ) BPX10-140 BPX10-185 BPX10-245 BPX10-260 ) BPX1-145 BPX1-160 ) BPX1-175 BPX1-235 c- BPX1-205 BPX1-260 BPX1-315 f Figure 63. Dendrograms from Q-mode cluster analyses of lower bathyal downcore samples showing glacial-interglacial separation: a) all samples from BPX-1 and BPX- 10 using 21 species at > 1% in 10 or more samples; b) samples from BPX-10 only using 7 species at > 1% in 9 or more samples; c) samples from BPX-10 only using 8 species at > 2% in 7 or more samples; d) samples from BPX-1 only using 10 species at > 1% in 9 or more samples; e) samples from BPX-1 only using 12*species at > 2% in 5 or more samples; 0 all samples from BPX-1 and BPX-10 using 19 species at > 2% in 6 or more samples. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155 Figure 64. Dendrograms from Q-mode cluster analyses of abyssal downcore samples showing glacial-interglacial and within-depth zone separation: a) all samples from PC-1 and PC-2 using 31 species at > 1% in 2 or more samples; b) all samples from PC-1 and PC-2 using 21 species at > 2% in 2 or more samples; c) samples from PC-1 only using 15 species at > 2% in 2 or more samples; d) samples from PC-2 only using 14 species at >2 % in 3 or more samples; e) samples from PC-1 only using 17 species at> 1% in 5 or more samples; 0 samples from PC-2 only using 16 species at > 1% in 5 or more samples. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hierarchical Clustering Method = Ward’s Minimum Variance — (21 PC2-15 PC2-15 ---- Z1 PC2-30 PC2-20 ---- Z1 PC2-40 PCI-10 — a - Z1 PC1-10 PCI-20 ---- Z1 PCI-20 PCI-60 ---- 71 PC2-20 PCI-80 ---- Z1 PCI-60 PC1-100 — Z1 PCI-80 PC1-110— Z1 PCI-100 PC1-120—L Z1 PCI-110 PC1-200 — Z1 PCI-120 PCI-140----- Z1 PCI-140 PCI-160----- Z1 PCI-160 PC1-360 ----- 22 PCI-300 PCI-440----- 22 PCI-340 PCI-320----- rtn PCI-360 PCI-340----- PC1-I0 PC1-20 PC1-60 PCI-80 PCI-100 PCI-110 PCI-120 PCI-140 PCI-160 PCI-200 PCI-320 (2/Y I PCI-340 c- (Y1 I PCI-360 — m I PC1-440 (Y1/Y2 I PC1-380 PC1-240 PC1-300 PC1-260 PCI-280 PCI400 d PC1-10 PC2-15 PCI-20 PC2-30 PCI-60 A' PC2-4C PCI-80 PC2-20 A- PC1-240 PC2-50 PCI-260 PC2-90 PCI-300 B' PC2-100 PC1-2B0 PC2-110 PCI-400 PC2-120 PC1-100 PC2-130 = h - PC1-120 c- PC2-180 PCI-140 □ ------PC2-140 PC1-160 PC2-1S5 PC1-200 u ------I PC2-200 PC1-440 PC2-215 PCI -320 D- PC2-260 PCI-340 PC2-300 PC1-360 PC1-380 PCM 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157 included in the analyses. The dendrogram from the 17 species at the >1% analysis shows strati graphic disorder and does not exhibit a distinct glacial-interglacial signal (Fig. 64e), whereas the results from 15 species at the >2% analysis (Fig. 64c) shows three of the Pleistocene samples grouping together to form a separate cluster (C), thus delineating a glacial-interglacial separation. Overall, a within-core, glacial-interglacial separation can be detected by cluster analysis in all cores. Depth Signal: Between Core Analyses Within Depth Intervals Cluster analysis reveals a distinct depth-separation within both the lower bathyal and abyssal environments, possibly allowing a refinement of depth zonations. The cluster analysis of all lower bathyal samples from cores BPX-1 and BPX-10, using 19 species at the > 2% level, shows a distinct depth separation as well as a glacial-interglacial separation (Fig. 63a). However, the analysis using 21 species at the > 1% level shows only a distinct depth separation, the glacial-interglacial signal is present but is more noisy than that in the > 2% analysis (Fig. 630- Both analyses of all abyssal samples from cores PC-1 and PC-2 show a distinct depth separation between the two cores (Figs. 64a, b), but the glacial-interglacial signal is not as distinct in both cores (as was reported for the single core analyses). For core PC-2, both >1% and >2% analyses, all but one glacial sample group together (cluster D) and the remaining Holocene samples form cluster C (Fig. 64a, b). Samples from PC-1 do not exhibit a clear glacial- interglacial signal as discussed previously. All Sample Analysis: Between Depth Intervals Cluster analysis of all samples together reveals a strong depth separation between the lower bathyal (Depth Zone B) and abyssal (Depth Zone A) environments, as well as a within-depth separation (Fig. 65). The downcore distribution of samples among clusters shows no significant stratigraphic disorder (Fig. 66). The glacial-interglacial signal is clearly evident, but it is not strong enough be the dominant force in the cluster Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hierarchical Clustering Method = Ward’s Minimum Variance PC2-15 PC2-20 PCI-10 PC1-20 PC1-60 PC1-80 PC2-30 PC2-40 PC2-50 PC2-90 PC2-100 PC2-110 PC2-130 PC2-120 ' • - 'M '. PC2-140 PC2-155 PCM 00 PCM 10 PCM 20 Depth PCM 40 Zone PCM 60 PC1-200 A PC1-320 PC1-340 PC1-240 (21/Z2 PC1-280 PC1-300 PC1-260 PC1-360 PC1-440 PC1-380 BPX1-260 PC1-400 PC2-180 PC2-200 PC2-215 1.1. .. - IT., ,~v«. PC2-260 pta-ann.. BPX1-25 BPX1-55 BPX10-25 BPX10-55 BPX1-80 BPX10-115 BPX10-85 BPX1-105 BPX1-145 Depth BPX1-235 Zone BPX1-175 \\\\\ BPX1-160 B BPX1-205 BPX1-315 * 1 BPX1-115 BPX10-140 BPX10-215 BPX1-290 BPX10-260 BPX10-185 BPX10-245 Figure 65. Dendrogram from Q-mode cluster analysis of all lower bathyal and abyssal downcore samples using 37 species at > 2% in 2 or more samples, showing between- depth zone separation, a within-depth zone separation and a within-core glacial- interglacial separation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Figure 66. Cross-sections showing the stratigraphic distribution of sample clusters. sample of distribution stratigraphic the showing Cross-sections Figure 66. Core Depth (cm) Stratigraphic Distribution Distribution Stratigraphic of Sample Clusters Sample of (1543m) BPX-10 included included n study in not not & (1815m) BPX-1 IY3/Y4 0 -===X4=_=_"" 400 0 ■300 :g£SS^ggS6SSa3S (2905m) PC-1 Z/Y Z1/Z2 Y1/Y2 400 J 400 300- 200 100 # s (3632 m)(3632 included included n study in PC-2 PC-2 - ^ x 5-C S'-* not not JT-. r%£r. Y1/Y2 Z/Y Z1/Z2 159 160 analysis. In each depth interval, lower bathyal and abyssal, the latest Holocene samples from both cores cluster together (Figs. 65,66) indicating a strong similiarity between latest Holocene samples within each depth interval. The Y 1 samples are often mixed with both Holocene and Pleistocene samples, but in general, full-glacial samples (subzones Y2, Y3 and Y4) always group together, indicating a strong separation between full-glacial and latest Holocene samples. The within-depth separation is evident only during glacial intervals in the lower bathyal environment, but also occurs in the early to middle Holocene in the abyssal realm (Figs. 65,66). Discussion and Summary The following discussion relates patterns of benthic foraminiferal species diversity, dominant species trends, and results of the numerical analyses to address the following topics: 1) Holocene benthic foraminiferal variability, 2) late Quaternary glacial- interglacial and depth-related patterns of benthic foraminifera, and 3) the benthic foraminiferal record of dissolution and productivity. Modem Analog: Benthic Foraminiferal Variability Despite the physico-chemical stability of the lower bathyal and abyssal environments in the Gulf of Mexico, patterns of species diversity, assemblage variations, and biofacies distributions reflect considerable complexity. Although simple species diversity shows no distinct trend with depth, it is persistently high. This high diversity reflects the large niche capacity of the lower bathyal and abyssal Gulf, although in most instances the amount of foraminiferal biomass being supported is quite small, and widely dispersed, as indicated by the very high species equitability values. Of the 166 species identified, only about 30 reach abundances high enough to be considered as being influenced by anything other than random variation. Factors influencing the complex benthic foraminiferal distributions include microhabitat heterogeneity, disturbance by macrobiota, bottom currents, sediment mixing, patchiness of food Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 resources, sediment accumulation rates, water-mass characteristics, and differential preservation. In most cases, many of these factors affect benthic foraminiferal populations, and although reading a single signal is difficult, it is not impossible. Throughout most of the lower bathyal and abyssal regions, bottom waters are well- oxygenated (4.8-5 ml/L) and the flux of COTg to the seafloor is low (< 1 gC/m2/yr; (Loubere et al., 1993b; Lagoe et al., 1994). However, it is possible that intermittent input of organic material may influence some of the foraminiferal distributions in these deep environments. Recent studies such as those of Gooday (1988,1993) and Smart et al. (1994) have documented benthic foraminiferal responses to sudden, sometimes seasonal influxes of phytodetritus. It appears that some species are able to take advantage of this fluctuating input of organic matter for varied time periods. Surface water circulation patterns may also influence productivity signals. Anticyclonic, warm- core eddies shed from surface-water currents tend to have low nutrient levels, whereas the cyclonic eddies have much higher productivity levels (Biggs, 1992). The episodic shedding of cyclonic, high nutrient-producing eddies from the Loop Current into the western Gulf may, then, produce intermittent productivity events, which would most affect areas directly beneath eddy paths, and thus, would explain the overlapping of the High/Episodic Productivity and the Low Corg assemblages, identified by factor and cluster analyses, and represented by the Lower Bathyal Biofacies. Organic matter type influences the distributions of some benthic foraminifera. For example, the biofacies from depth zone A and the assemblages that characterize them (Mixed Agglutinated-Calcareous (F1+) and NADW (F6+) assemblages) lie in Area 3, which is associated with predominantly marine organic matter sources (Figs. 8 and 51). Although species that characterize these assemblages are often present throughout the study area, their high abundances here may suggest a preference for marine organic matter. A contrast is provided by two species, Nuttaliides decoraia and Cassidulim Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 subglobosa, which define the Low Coq, Assemblage characteristic of the Orca Basin Area Biofacies. This biofacies is restricted to the region adjacent to Orca Basin, an area with unusually high sediment accumulation rates, and therefore, possibly higher concentrations of terrestrial Corg relative to marine Corg. Thus, these species may attain higher abundances in areas associated with some terrigenous influence (Jones and Sen Gupta, 1995), or they may be more readily able to adapt to variable organic matter types than other species. Although a productivity signal is common throughout the lower bathyal and abyssal realms, it can be isolated to some degree as described above, and a water-mass signal can be detected. The biofacies of depth zone A are characterized by Ioanellatumidula and Cibicides wiiellerstorfi, species commonly associated with North Atlantic Waters by numerous workers (e.g. Sen Gupta, 1988; Scott et al., 1989; Mackensen et al., 1990; Ishman et al., 1996). These species define two assemblages identified by factor analysis, the Mixed Agglutinated-Calcareous (F1+) assemblage, and the NADW (F6+) assemblage, that appear to reflect bottom-water masses. The idea that the Mixed Agglutinated-Calcareous (F1+) assemblage reflects remnants of a glacial fauna is supported by several studies from tropical Caribbean and equatorial Atlantic regions (Gaby, 1982; Wendler, 1987; Galluzzo, 1989). These studies reported Ioanellatumidula (= Eponides tumidula) in both glacial and interglacial intervals, with much higher abundances during glacial intervals. Its common occurrence in modem Arctic deep waters (Lagoe, 1977; Scott and Vilks, 1991; Ishman and Folev, 1996) is not surprising, since it apparently prefers cooler, deep waters. Another calcareous species that defines this assemblage is Gyroidinoides polius. This species, associated with CMW in the Gulf of Mexico (Denne and Sen Gupta, 1991), was reported only from Recent sediments in the Venezuela Basin (Gaby, 1982) suggesting that it may reflect the influence of modem renewal waters (CMW+NADW) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 into the deep Gulf. Cibicides wuellerstorfi clearly reflects an NADW influence into the deep Gulf of Mexico. Because its abundances in the northwestern Gulf are considerably lower (average 3% and maximum 8% in one sample) than those of the Caribbean and the equatorial Atlantic (Gaby, 1982; Wendler, 1987; Sen Gupta, 1988; Galluzzo, 1989), the NADW signal in the Gulf is very weak, due to dilution with CMW. Stressed conditions appear to influence some part of the lower bathyal environment today. Stations from the Environmentally-Stressed Biofacies are characterized by unusually high abundances (39-45%) of Bolivim lowmani and they exhibit the lowest species diversity and species equitability values. The absolute abundance of B . lowmani, which is relatively constant (< 20 individuals/g sediment), indicates that the high relative abundances occur because other species cannot readily adapt to the environmental conditions, and the persistent species are not abundant. Bolivina lowmani has been associated with fine-grained substrates and relatively high sedimentation rates (Lankford, 1959; Sen Gupta et al., 1981; Galluzzo, 1989) both of which are prevalent in the study area. However, not all stations with high sediment accumulation rates exhibit these extremely high abundances, suggesting that something other than substrate and the high sediment accumulation rates is influencing the Bolivina lowmani relative abundances. Factors that may be perturbing the environment are difficult to isolate, but disturbance by macrofauna (Grassle and Maciolek, 1992; Loubere et al. 1995), bottom currents, and sediment transport are likely candidates. Sediment transport is often easier to demostrate than the presence of macrofaunai disturbance and bottom currents, but the latter two may favor the presence of an infaunal species such as Bolivina lowmani. The very’ high abundances of B. lowmani, which characterize this assemblage, indicate environmentally-stressed conditions, such as was Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 164 inferred for a neritic assemblage characterized, in part, by Bolivina lowmani from the Azua Basin by McLaughlin and Sen Gupta (1994). Preservational factors seem to influence, at least to some degree, benthic foraminiferal assemblages. Most notable is the Hoeglundina elegans assemblage, which is present only in lower bathyal areas with high sediment accumulation rates, suggesting that rapid burial reduces exposure time at the sediment-water interface, thus precluding dissolution of this aragonitic form. An occasional presence of pteropods is also evident at some stations in the deep Gulf. The deepest Gulf bottom waters are clearly corrosive to aragonitic forms, but the variable sediment accumulation rates preserves them well in some areas. The last factor to have a noticeable influence on Recent benthic foraminiferal distributions is sediment transport. Two stations clearly reflect downslope sediment transport. These two stations comprise the environmentally-mixed biofacies restricted to the Orca Basin (Fig. 51), which does not support an indigeneous benthic fauna (Lagoe et al., 1994). Species that represent this biofacies, Osangulariaculler, O. rugosa, Bolivina albatrossi, Gavelinopsis translucens, and Epistominellaexigua, are from distinctly shallower, and more poorly-oxygenated waters than the surrounding lower bathyal waters of the study area in the vicinity of Orca Basin. Moreover, Lagoe et al. (1994) reported an obvious case of downslope sediment transport at one of these stations (IG-46-09) on the basis of its shallow-water biotope. The significance of a Mixed assemblage identified by factor analysis (F3+) remains unclear. It is not associated with any of the benthic foraminiferal biofacies and does not show a mappable pattern of sediment mixing. Four samples showed strong positive factor scores (Fig. 45), which suggests some influence of this assemblage in isolated parts of the study area, but clearly not enough to obsure an indigeneous benthic foraminiferal signal. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 6 5 Benthic foraminiferal assemblages and biofacies distributions in surface sediments reveal the extremely complex nature of lower bathyal and abyssal environments in the Gulf of Mexico, despite the phyisco-chemical stability of the overlying Gulf Basin Water. Previous work of Poag (1981), based on compilations of benthic foraminiferal genera, identified only four fauna! provinces within the study area (Fig. 67). A clearer picture of the environmental complexity is revealed by using species level data, as in this study. Furthermore, benthic foraminiferal biofacies are easily recognizable both between and within the Modem lower bathyal and abyssal environments, but the factors controlling the separation of these biofacies are not just related to bathymetry. Robust numerical techniques must be used to tease out these complex species inter relationships. Late Quaternary Glacial-interglacial and Depth-Related Variability The persistently high species diversity and equitability documented from the Modem analog is prevalent throughout the late Quaternary. In lower bathyal cores, species diversity and equitability exhibit little variation while maintaining rather high values. In contrast, the abyssal cores, which also have relatively high species diversity, show considerable fluctuations during the deglacial transition (subzones Y 1, Z2 and basal Zl). In the Pleistocene Y2, Y3, Y4 subzones and in the latest Holocene Z1 zone, species diversity values are at their highest in cores PC-1 and PC-2. Apparently, stable (relative to the deglacial transition) bottom conditions during full-glacial intervals, and the latest Holocene interglacial interval (Z2 to present) led to these high diversity and equitability values. This deglacial instability may reflect reorganization of deep Gulf bottom waters, possibly coinciding with and related to changing North Atlantic and Caribbean deep-ocean circulation patterns. These high diversity and equitability values that occur throughout the late Quaternary indicate little if any strong dominance by a few species and identifying species Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. & ro t 4 tiom ro tiom t than OLIO ^W cot KHOUEffRS FIGURE 19 FIGURE • Wiolid - Aicbotot *HomoWemo • WiolidAicbotot- *HomoWemo Focitt N* (ftptttnirtiiottom vxomtrt b* cWcNt) O • ArophWteglno Focitt Uvio*U»lQtflno F odtt © • Hoegiundlno F odtt f p • Clomoiplfo Foclet puwikM Holln puwikM (upmnltd IihukI by INi) w 4 0 0 5000 Gcrwtlc Pitdomnmc* rodrt mn) IN «mhn« bvnlMc (noirMfpat (noirMfpat bvnlMc rodrt mn) IN «mhn« Pitdomnmc* Gcrwtlc rowiriii •( IN Cwtt o< OaN ihon ihon U * /Vi' * PI p m m L;Ai $ CIBiCfOtS $CIBiCfOtS W m m m .■•fee YUCATAN wmxw-igs CAM1*EC StrtiTl -^V StrtiTl l l i l l*f 1*1 - , \DVT V -^ 1 a n a r f L O U t it TARASCO mJv*WEtic MM Figure 67. Mapshowing distributionthe ofgeneric benthic foraminiferal provinces modified from Poag (1981). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 167 influences on foraminiferal biofacies delineated by cluster analysis is difficult. However, downcore plots of several dominant species revealed a few associations that can be related to several factors, such as water depth, bottom-water fluctuations, organic carbon flux and oxygen levels, and carbonate preservation/dissolution. These factors are discussed further within the framework of their water-depth associations. The late Quaternary abyssal and lower bathyal environments are clearly distinquished by cluster analysis (depth zones A and B, respectively; Fig. 65). This apparent depth separation is controlled by the presence/absence of several species which are restricted to these environments within the depth range of the study area. Downcore species plots indicate that Bulimina aculeata, B. mexicana, B. spicata, Uvigerina peregrina, U. hispidocostaia, Paumotua sp. cf. P. terebra, Gavelinopsis translucens, Martinottiella occidentals, and Sigmoilopsis schlumbergeri are present in low to moderate abundances (3-10%) only in the lower bathyal cores, and are rarely present in the abyssal cores, whereas loanella tumidula, Melonis pompilioides, Cibicides wuellerstorfi, Siphotextularia affinis and Bolivina lowmani are present only in, or exhibit their highest abundances in, the abyssal cores. Most of the above lower bathyal species occupy infaunal microhabitats (Denne and Sen Gupta, 1989; Loubere and Gary, 1990), and can tolerate low-oxygen conditions and high COTg levels. This connection is reflected by their association in the High/Episodic Productivity Assemblage (F4+) identified by factor analysis for the surface sediments. In contrast, species characterizing samples from the abyssal depth zone (A) group reflect the influence of three assemblages: 1) the Mixed Agglutinated-Calcareous (F1+), 2) the NADW/CMW (F6+-), and 3) the Environmentally-Stressed assemblage (F5-), all described in the Modem analog study. The presence of these assemblages suggests that the late Quaternary abyssal region, relative to the lower bathyal environment, was more strongly Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 168 influenced by bottom-water fluctuations and carbonate dissolution, and may have been subject to more extreme environmental conditions. Late Quaternary Lower Bathval Environment (Depth Zone B) Three distinct biofacies, which reflect spatial and temporal variations, were revealed by the cluster analysis. First, an interglacial biofacies (cluster 6) which includes all the Holocene samples from both lower bathyal cores, and second, two glacial biofacies (clusters 7 and 8) consisting primarily of samples from core BPX-1 and BPX-10 (Fig. 65). Apparently, conditions within the lower bathyal realm were variable during the latest Pleistocene, and uniform bottom conditions within the lower bathyal environment emerged in the interglacial. Samples of the interglacial biofacies from both cores (Cluster 6) differ from the those of the two glacial biofacies in that they show higher relative abundances of Cibicides wuellerstorfi, Cassidulina subglobosa, Osangularia culler, Episiominella exigua, as well as several agglutinated species, and considerably lower abundances of the Oridorsalis tener species group, and the agglutinated species Eggerellabradyi, Sigmoilopsis schlumbergeri, and Martinottiellaoccidentalis. The stratigraphic distributions of three of these species with strong present-day watermass associations, Cibicides wuellerstorfi (NADW), Osangularia culter (SAIW) and the Oridorsalis tener species group (NAIWj, suggest a shift in Gulf basin bottom-water source from the Pleistocene into the Holocene. The abundance maxima of the aragonitic species Hoeglundina elegans in these samples suggests that lower bathyal bottom waters were saturated with respect to aragonite during the early to middle Holocene. In Modem surface sediments from this study, Hoeglundina elegans is abundant only in samples from the Orca Basin region, an area with extremely high sediment accumulation rates, indicating increasing undersaturation of bottom waters with respect to aragonite in low'er bathyal regions today. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169 The higher relative abundances of agglutinated species present in samples of the interglacial biofacies probably reflect their non-preservation in older sediments. Glomospiracharoides, Karrerulinaapicularis and SpiroplecteUa cylindroides, rather fragile forms, are absent below about 50-100 cm core depth, and they make up only 1- 2% of the assemblage above these stratigraphic depths, whereas Sigmoilopsis schlumbergeri, Eggerella bradyi, Martinottiellaoccidentalis, and Siphotextularia ajfinis , somewhat robust forms, maintain low to moderate abundances at much deeper core intervals. Two of these more robust forms, Sigmoilopsis schlumbergeri, and Eggerella bradyi, also have been associated with Modem NAIW in the North Atlantic Ocean (Rasmussen et al., 1996a, b). The dominance of interglacial samples by species associated with NADW and SAIW, and that of glacial samples by species associated with Modem NAI W are strong indications that changing deepwater circulation in the North Atlantic exerts an influence on Gulf Basin Water (GBW). The two glacial biofacies (clusters 7 and 8) reveal spatial variation within the late Pleistocene lower bathyal environment. Samples making up the BPX-10 glacial biofacies are characterized by consistently higher relative abundances of Uvigerina peregrina, Buliminaaculeata, Gyroidinoides spp. and Laticarinim pauperata. In contrast, BPX-1 glacial biofacies samples are characterized by very high abundances of Nuttallides decorata, Mabaminella turgida, and the Oridorsalis tener species group. The late Pleistocene spatial variation represented by these two lower bathyal biofacies suggests an environmental influence over and above that exerted by the overlying water mass. Samples from BPX-10 glacial biofacies (1543 m), dominated by Uvigerina peregrina and Buliminaaculeata , may reflect high- and/or episodic-productivity (see core-top study). The contrasting low abundances of Nuttallides decorata and Alabaminella turgida, which proliferates at low COTg levels (Fig. 49) and well- oxvgenated bottom waters, respectively, also support this idea. The very high Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 170 abundances of Nuttallides decorata and Alabaminella turgida in BPX-1 glacial biofacies (1815 m) may reflect increased bottom-water ventilation or a stronger influence of GB W over incoming CMW, as the present day boundary between these two water masses is 1500 m. Thus, in addition to being influenced by bottom-water conditions, the BPX-10 glacial biofacies appears to have been the site of higher productivity during the latest Pleistocene than the BPX-1 glacial biofacies. The latter probably reflects a stronger water-mass signal than the BPX-10 glacial biofacies due to the overprint of the productivity signal. Late Quaternary Abyssal Environment (Depth Zone A) Abyssal biofacies include a single Holocene interglacial biofacies (cluster 1), similar to that seen in the lower bathyal environment, two Holocene transitional biofacies (clusters 2 and 3), and two Pleistocene, glacial biofacies (clusters 4 and 5), all shown in Figure 65. The samples comprising the Holocene interglacial biofacies show higher abundances of Cibicides wuellerstorfi, Gyroidinoides polius, Ioanella lumidula, and the more fragile agglutinated species mentioned previously. Furthermore, Hoeglundina elegans is rare or absent in these samples. This biofacies reflects the Mixed Agglutinated-Calcareous (F1+) and the NADW (F6+) assemblages of the Modem analog described from surface sediments; its late Holocene appearance may reflect production of the more corrosive Gulf Basin Waters of the present day. The two transitional biofacies (clusters 4 and 5) contain the early to middle Holocene samples (all of subzone Z2 and most of basal Z l) of cores PC-2 and PC-1, respectively. These two biofacies share some general characteristics, but also reflect some abyssal spatial variation. In general, samples of these two biofacies are characterized by fluctuating abundances of Eggerella bradyi (3-5%), Ioanellatumidula (2-8%), Alabaminella turgida (10-45%), Nuttallides decorata (10-20%), Cibicides bradyi (1- 4%), Bolivina lowmani (with an abundance maximum to 64%), Hoeglundina elegans Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 171 (0-9%), consistent but low abundances of Cibicides wuellerstorfi (3-5%), and decreasing, but fluctuating abundances of the Oridorsalis tener species group. The transitional or unstable regime represented by these two biofacies is also reflected in the late Quaternary record of species diversity and equitability. While maintaining high species diversity and equitability, the record from both abyssal cores (Fig. 53), but PC- 2 in particular, shows considerable fluctuations in subzones Y1, Z2 and basal Zl, probably reflecting more stable (relative to the transition zone) bottom conditions during full-glacial intervals, and the firmly established interglacial interval of the latest Holocene. Spatial variation within the abyssal realm is evident in that the PC-2 transisitional biofacies (deepest abyssal site) is characterized by consistently highest abundances of Ioanellatumidula, the highest Bolivina lowmani abundances, low or lowest abundances of the Oridorsalis tener species group, Cibicides wuellerstorfi, C. bradyi, Alabaminella turgida, and Nuttallides decorata, and the conspicuous absence of Hoegludina elegans. This biofacies represents a somewhat stressed environment, reflected by the highest Bolivina lowmani abundances; it has been subjected to considerable dissolution causing the removal of the aragonitic species Hoeglundina elegans which is present in low to moderate abundances in the PC-1 transitional biofacies. The decreasing abundances of the Oridorsalis tener species group, and the increasing abundances of Cibicides wuellerstorfi support the notion that the record of open-ocean deepwater reorganization is captured in sediments from the deepest reaches of the Gulf basin. Like the Deglacial Transition biofacies, the two glacial biofacies (clusters 4 and 5) share some general characteristics, while also reflecting spatial variation within the abyssal realm. Species that characterize both biofacies with some of their highest abundances, and that are associated with Modem NAIW, are the Oridorsalis tener species group, Eggerella bradyi, and Ioanellatumidula. The high abundances of these Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172 species in place of Cibicides wuellerstorfi (rare to absent) suggests a stronger influence of NAI W during glacial intervals (GNAIW) within the Gulf of Mexico. These glacial biofacies are also chararacterized by the absence of Hoeglundina elegans (indicating increased aragonite dissolution) but they contain low to high abundances of dissolution- prone porcelaneous species such as Biloculinella irregularis and Quinqueloculina venusta. A striking feature of the abyssal glacial record is a rather large abundance maximum of Globobulimina ajfinis that appears abruptly within the Y1 subzone, and then is gone (Fig. 61). This fragile, infaunal species, which is difficult to preserve, may indicate high productivity because it can tolerate elevated levels of Corg and low- oxygen levels, and it is often associated with Late Quaternary anoxia in the Mediterranean (Mullineaux and Lohmann, 1981; Sen Gupta and Machain-Castillo, 1993). Although its presence alone cannot unequivocally reflect low-oxygen conditions (Sen Gupta and Machain-Castillo, 1993), this G. ajfinis pulse, in conjunction with other data (Chapters 2,3) may then reflect a brief, but intense productivity event during the Y 1 meltwater interval. The two glacial biofacies (clusters 4 and 5) are composed of samples from the PC-1 and PC-2 cores, respectively. Samples from the glacial PC-2 biofacies are characterized by moderate to high abundances of Bolivina lowmani, by the highest abundances of Ioanellatumidula, several porcelaneous species and the agglutinated species Siphotexularia ajfinis, and finally by the absence of Epistominellaexigua. This deepest abyssal glacial biofacies seems to represent a somewhat harsh or stressed environment. However, the presence of Biloculinellairregularis (a high-Mg calcite species) and Quinqueloculina venusta, both postulated to reflect decreased corrosivity of glacial Caribbean Basin Water (CBW; Galluzzo, 1989), in the glacial biofacies but not in any Holocene biofacies suggests that the deepest Gulf waters were slightly less corrosive during glacial intervals. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173 Benthic Foraminiferal Record of Productivity and Dissolution Evidence for productivity and dissolution variability, reflected by the benthic foraminiferal record is summarized below. Typically, the Modem lower bathyal and abyssal environments of the northwestern Gulf are characterized by low Corg fluxes (< 1 gC/m2/yr), and are well-oxygenated (4.8-5 ml/L; Loubere et al., 1993; Lagoe et al., 1994). In surficial sediments, biofacies characterized by the High/Episodic Productivity (F4+) and Reduced-Oxygen (F2+) assemblages are restricted to the lower bathyal realm indicating that this region may experience higher overall productivity relative to the abyssal environment. With respect to dissolution in surfical sediments, relative abundances of Hoeglundina elegans, which are generally low (0-6%), are consistently highest in the lower bathyal enviroment, in and around the Orca Basin. This area (Area 1, Fig. 5) has very high sediment accumulation rates (highest within the study area) and it is likely that Hoeglundina elegans is being preferentially preserved by rapid burial in this region. This rapid burial reduces exposure time at the sediment-water interface, and precludes the dissolution of this aragonitic form; this dissolution is prevalent in other parts of the lower bathyal and abyssal regions. Throughout the late Quaternary, dominance by the High/Episodic Productivity (F4+-) assemblage and the reduced influence of the Low COTg (F5+) and Oxygen- Sensitive (F6-) assemblages in the shallowest lower bathyal core BPX-10 suggest that this area was the site of somewhat higher productivity' relative to other areas of the lower bathyal and abyssal realm. This particular area is near the confluence of the westernmost extent of eddy paths and the remnants of a western boundary current flowing northward (Poag, 1981). The resulting complex surface-water circulation interactions in this lower bathyal region may have produced conditions more favorable to increased productivity by periodically enhancing the influence of nutrient-rich, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 cyclonic eddies, which are generally more prevalent in shelf areas (Biggs, 1992; Loubere et al., 1993b). The only benthic foraminiferal evidence indicative of a significant productivity event in the abyssal realm is the large pulse of Globobulimina affinis that appears abruptly and briefly within the glacial Y 1 subzone. The occurrence of this abundance peak in the two abyssal cores (PC-1 and PC-2), taken some 200 km apart, indicates that this was a widespread event. Moreover, a qualitative visual inspection of samples within the Y 1 interval of core PC-4 (from the planktic foraminiferal study, but not included in the benthic study) also identified this pulse of G. affinis in two consecutive samples (300- 320 cm), lending further support to the speculation that this is indeed the same event over an extended region of the abyssal realm. Evidence suggesting varying bottom-water corrosivity over the late Quaternary is present in the benthic foraminiferal record. Preservation of the dissolution-prone species Biloculinella irregularis and Quinqueloculina venusta within the Pleistocene Y zone and their absence during the Holocene Z zone suggests that glacial bottom-waters were somewhat less corrosive than present-day Gulf of Mexico bottom-waters. The late Quaternary’ record of the aragonitic species Hoeglundina elegans, however, indicates that lower bathyal and abyssal bottom-waters during the deglacial transition (early to middle Holocene) were less-corrosive (with respect to aragonite) than either present-day or glacial bottom waters. These two somewhat conflicting records pose a pu zzling question — how can Holocene bottom-waters be unable to dissolve aragonite, yet appear to remove the dissolution-prone species Biloculinella irregularis (high-Mg calcite) and Quinqueloculina venusta that are more common in the late Pleistocene? At present, the solution to this enigmatic problem remains unresolved, but the robust nature of the test of Hoeglundina elegans (thick and large) and the high sediment accumulation rates Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 occurring at the time of its maximum preservation may be factors in its unusal preservation record. Synopsis The following summarizes briefly the paleoceanographic inferences based on the benthic foraminiferal record. From the Modem analog study, a weak influence of NADW is evident in the Gulf of Mexico today. The type and amount of organic matter may influence the distribution of some benthic foraminifera. For example, some species reflect the presence of high and/or episodic productivity events which may have been initiated by suface-water circulation patterns, such as eddy shedding from the Loop Current, whereas others such as Nuttallides decorata and Cassidulina subglobosa may prefer a component of terrigenous Cor*>. Parts of the deep Gulf are subjected to stressed environmental conditions as evidenced by lower species diversity and equitability values, and very high abundances of Bolivina lowmani. These areas may be affected by bottom circulation, macrobenthos disturbance or sediment mixing. The former two may be most likely, since sediment mixing is often easily recognized. Sediment mixing by downslope transport is evident in the Orca Basin, an interslope basin that does not usually support an indigeneous fauna The biofacies at the Orca Basin stations reflects a benthic foraminiferal assemblage that is clearly from a shallower, more poorly- oxygenated environment than most of the study area Some preservational effects are evident. The aragonitic species, Hoeglundina elegans, attains its highest abundances in Area 1, which has the highest sediment accumulation rates, suggesting that exposure at the sediment-water interface is insufficient for dissolution. Consistently high species diversity- and equitability are evident in lower bathyal and abyssal sediments of the northwestern Gulf through the late Quaternary, and remains high in the surface sediments of the present day. However, an interval of widely- fluctuating, yet still high, species diversity and equitability values characterizes a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176 deglacial transitional interval. Holocene sediments of the lower bathyal environment do not exhibit the variability present in Modern lower bathyal surface sediments. Conversely, in the abyssal environment, a distinction between biofacies of the latest Holocene and the deglacial transition (early-middle Holocene) is evident in benthic foraminiferal assemblage variations. The shift from a Pleistocene assemblage dominated by species linked to Modem NAIW to a Holocene assemblage dominated by species associated with NADW and SAIW confirm that the record of open-ocean deepwater reorganization is captured in sediments from the deepest reaches of the Gulf basin. The presence of the High/Episodic Productivity (F4+) and Reduced-C>2 (F2+) assemblages only in the lower bathyal enviroment suggests that this region is more strongly influenced by productive surface waters than the abyssal region. The apparent depth-related separation between the lower bathyal and abyssal environments is, in fact, best explained as a productivity-related separation which simply coincides with bathymetry. Finally, the records reflecting carbonate dissolution in the lower bathyal and abyssal environments, inferred from benthic foraminifera, suggest that glacial GBW was less corrosive than that of GBW in the present-day Gulf. During the deglacial transition, however, GBW was, apparently, saturated with respect to aragonite as evidenced by the low, but consistent relative abundances of Hoeglundina elegans. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 5 SYNTHESIS This chapter contains a detailed chronostratigraphic summary of the paleoceanographic and paleoclimatic changes based on the Iithostratigraphic, planktic foraminiferal, and benthic foraminiferal records described in chapters 2,3, and 4, respectively. In addition, a model is proposed for surface and deep-water paleoceanography of the abyssal Gulf regions. The following theses addressed in this dissertation are also discussed below: 1) that foraminifera can be reliably used as indicators of paleoceanographic change, 2) that the influx of glacial meltwater strongly affected surface-water conditions in the Gulf, 3) that shifting open-ocean deepwater circulation influences deep Gulf basin waters, 4) that spatial variation within the lower bathyal and abyssal environments are reflected in benthic foraminiferal assemblages and biofacies distributions, thus allowing refinement of these historically depth-defined, deepwater depositional environments, and 5) that, despite the complexity of benthic foraminiferal inter-relationships, environmental, preservation and productivity signals can be isolated. The Late Quaternary Record of Paleoceanographic and Paleoclimatic Change in the Northwestern Gulf of Mexico Full-Glacial/Last Glacial Maximum (LGM) Interval (Y4, Y3. Y2 subzones) The reduced size of the Gulf basin at this time (Fig. 68), due to lowered sea level, also reduced the surface-water area This diminished surface-water area led to higher surface-water nutrient levels as evidenced by higher Corg values (Fig. 9), and an increased influence of terrigenous COTg (reflected by 613 C values; Fig. 10). The low calcium carbonate content in this interval relative to interglacial sediments (Fig. 12), 177 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■30*- 25'- SIGSB;e plain Gulf of Mexico at LGM i ■2 95* 90* 96* New~ Orleans Galveston .28* Corpus Christi DEP delta DELTA M ISSISSIPPI RIVER DELTA RIO GRANDE DELTA 50 100 km Figure 68. Gulf of Mexico basin at the last glacial maximum (LGM): a) map showing study area (black outline) and the LGM shoreline and b) map showing late Pleistocene shelf-edge deltas modified from Suter and Berryhill (1985). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 179 supports the idea that an increased influx of siliciclastics, diluted the carbonate sediments. The strong influence of a planktic foraminiferal assemblage tolerating highsurface-water nutrients (Planktic Factor 1 [PF1]; Fig. 31) is evident at this time. In contrast, total planktic foraminiferal populations, which are often used as a proxy for surface-water productivity, were at their lowest during this full-glacial interval (Fig. 30), indicating no increase in surface-water productivity at this time. Surface-water temperature conditions were cool throughout Y 4 and basal Y 3, reflected in the strong influence of a cool-water assemblage (Planktic Factor 2 [PF2]; Fig. 32) characterized by Globorotalia inflata, G. crassaformis and Globigerina falconensis (Figs. 14-21). These cool surface-water temperatures began waning in upper Y3 and through Y2 with the onset of climatic wanning. That surface-waters were relatively stable during this glacial interval is evidenced by the dominance of a more stenotopic assemblage (cool-water variety) identified by Planktic Factor 3 (PF3; Fig. 33). Although glacial Gulf Basin Water (GGBW) and Gulf Basin Water (GBW) are considered to be relatively stable water-masses, benthic foraminiferal relative abundance data indicate that GGBW was somewhat different from GBW that occupies the northwestern Gulf today. The consistently high species diversity and equitability values throughout this interval further support this idea (Figs. 52 and 53). The dominance of assemblages characterized by species associated with Modem NAIW (the Oridorsalis tener group, Sigmoilopsis schlumbergeri, Eggerella bradyi , Ioanellatumidula; Figs. 55- 58) during this interval suggests a change in the source area for Caribbean renewal waters entering the Gulf at this time. Corroborative evidence is provided by the preservation of dissolution-prone species within this interval. The presence, albeit in low abundances, of Biloculinella irregularis and Quinqueloculina venusta (Figs. 59, 60), which are not preserved in Holocene intervals, indicates that GGBW was less corrosive and probably had a different source than Modem GBW. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 180 Despite the relative stability of glacial surface- and bottom-waters, the lower bathyal and abyssal environments exhibited some spatial differences. Variations in Corg flux and oxygen level, as indicated by the increased abundances of species tolerant of high Corg flux and reduced-oxygen conditions (Bulimina aculeata, B. mexicana, B. spicata, Uvigerina peregrina and U. hispidocostata) in the vicinity of BPX-10, are seen in the lower bathyal realm. In the deepest part of the Gulf (site of PC-2,3632 m), bottom conditions may have been stressed as indicated by the abundance maximum of Bolivina lowmani (Fig. 58), which reflects the Environmentally-Stressed assemblage (F5-). Also, judged by the absence of Hoeglundina elegans, this deepest site was subjected to considerable (greater than in the remainder of the study area) bottom-water corrosivity (Fig. 60). Although variations in bottom-water corrosivity are evident, overall, pulses of intense dissolution are not evident (Table 14; Figs. 14-21,31). The preservation of dissolution-prone benthic foraminifera (Fig. 60) indicates reduced bottom-water corrosivity during this glacial interval. The Meltwater/Y oungerDrvas Interval (Y 1 subzone) The most dramatic event of the Y 1 interval was the influx of glacial meltwater into the northwestern Gulf, identified by Globigerinoidesruber maxima (Figs. 22, 34). The meltwater influx severely affected surface waters in two ways: 1) by reducing salinities, as inferred from increased abundances of euryhaline planktic species (Figs. 29,23,34), and 2) by increasing incoming nutrient fluxes, indicated by the presence of an Corg maximum, probably of terrigenous origin (Figs. 9,10). Unlike the full glacial/LGM interval, significantly increased levels of surface-water nutrients resulted in higher surface-water productivity, which is evident from an increase in total planktic foraminiferal populations (Fig. 30), and by more enriched 613C values (Fig. 10), indicating an increase in marine Corg. As will be discussed below, this increase of incoming nutrients with the glacial meltwater appears to have briefly influenced bottom conditions. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 1 na na PC-4 2 na na na na na na PC-2 na na na PC-1 1 5 4 1 nana na na na na na na na na 1 na na I na na 1 4 IG-45-I5 BPX-1 1G-41-21 1G-41-26 na 1 na na BPX-10 XI X2 na 1 na na na na Y8 na na na na na na na Z2 X3 na na Y5Y7 na na 1 na na na Zl 1 Y6 na Y3Y4 na na na na Y1 Y2 na Zone/Station dissolution event at lowerthe boundary of zone;the indicatesna zone not present. Table 14. Summary ofCarbonate Dissolution Events. Numbers in bold indicateone Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18 2 Surface-water temperatures continued to increase (PF2; Fig. 32) with little, if any, surface-water cooling during the interval of the Younger Dryas (upper Y 1). This interpretation is contrary to that of Kennett et al. (1985), and Flower and Kennett (1990), who suggest that Gulf of Mexico surface-waters cooled to full-glacial conditions at this time. However, it is in good agreement with a re-evaluation of their data by Anderson and Thunell (1993) who concluded that Gulf of Mexico surface- waters did not significantly cool during the Younger Dryas. Also, the continued decreasing dominance of the stenotopic assemblage (cool variety) during this interval (Fig. 33) indicates increasing surface-water instability . The physico-chemical conditions of GGBW within the Meltwater/Younger Dryas interval remained as described above for the full-glacial/LGM interval, with two notable exceptions. First, the high benthic species diversity and equilability' values common through the full-glacial/LGM interval persist only into lower Y 1, after which, they begin to fluctuate (Fig. 53) into the early Holocene, reflecting the onset of increasingly unstable bottom-water conditions. Second, the relative abundance of Globobulimina affinis (Fig. 61), a hypoxia-tolerant (and generally poorly-preserved) species shows an abrupt, although brief, increase within this interval. This G. affinis abundance maximum is either coeval with, or just antecedent to an increase in total planktic populations (Fig. 30), and co-occurs with the highest COTg levels of the late Quaternary. This areallv widespread (at least 200 km across) hypoxic event may then reflect a brief, but intense period of surface-water productivity brought on by the high nutrient levels associated with the incoming glacial meltwater. Deglacial-lnterglacial Transition Interval (22 and basal Z l subzones) This interval, present only in the abyssal cores, corresponds to a transitional, or somewhat unstable, surface and deep%vater paleoceanographic regime with steadily increasing surface water temperatures, as reflected by the increasing presence of the warm-water assemblage identified by Planktic Factor 2 (Fig. 32). Several factors Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 183 delineate the stratigraphic extent of this deglacial-interglacial transition: 1) widely fluctuating species diversity and equitability values (Rg. 53); 2) relative abundance shifts of several known watermass-associated benthic foraminifera (Figs. 55,57,58, 61), as if competing for ecospace; 3) a dramatic shift from the strong influence of a more stenotopic assemblage (cool variety) to a more eurytopic assemblage (PF3; Fig. 33), which is later replaced by a more stenotypic assemblage (warm variety); and 4) an increasing influence of marine-sourced C0rg (Fig. 10). Increased surface-water productivity', which began in the previous Meltwater/Younger Dryas Interval, continues just into Z2 and declines. This trend is reflected in the record of total planktic populations (Rg. 30), and by the more nutrient-depleted character of the surface-waters indicated by Planktic Factor 1 (Fig. 31). Evidence of deepwater instability over this interval is present in the widely fluctuating species diversity and equitability values, and the decreasing abundances of the Oridorsalistener group (and other NAIW species), coeval with increasing abundances of Cibicides wuellerstorfi and Osangularia culter (NADW and SAIW species, respectively). This signal, albeit weak, of deepwater transition or instability records the onset of open-ocean, deep- and intermediate-water reorganization that led to the present-day configuration of thermohaline circulation and deepwater formation. In addition, unusual preservation patterns, such as the records of Hoeglundina elegans, Pyrogoella irregularis, and Quinqueloculina venusta , and the increased frequency of brief, but intense dissolution events inferred from planktic foraminifera (Table 14; Figs. 14-21,22,31) indicate increasing bottom-water corrosivity from glacial to interglacial intervals. However, with the deglacial-interglacial transition, rates of sediment accumulation significantly increased (Table 3 ; Fig. 5). These high rates apparently insulated Hoeglundina elegans from the more corrosive bottom-waters by rapid burial. Finally, a carbonate maximum (relative to adjacent intervals; Fig. 12) is prevalent throughout the study area within the early Holocene Z2 interval. This carbonate Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 184 maximum may represent the early Holocene CaCC >3 preservation event documented by Broecker et al. (1993) in the western equatorial Atlantic. Latest Holocene/Modem Interglacial Interval (upper Zl subzone) This interval, which reflects the onset of surface- and deepwater-oceanographic conditions of the present-day Gulf, is characterized by the same reduced suface-water productivity and low incoming nutrient levels (Figs. 9,30,31), and by an increasing dominance of marine-sourced COTg (Fig. 10), as was the Deglacial-interglacial Transition Interval. The record of total planktic populations exhibits a decline which is consistent with reduced surface-water productivity indicated by the Corg record. Carbonate content, however, decreased slightly from the preceding interval, although in some areas a second carbonate maximum (upper Zl interval) is evident (Fig. 12). The increasing influence of the stenotypic, warm-water assemblage persisted (PF2, PF3 ; Fig. 32,33), reflecting continued surface-water warming to the present. Deepwater conditions began to stabilize, relative to the preceding interval; this is indicated by a return to high benthic species diversity and equitability values characteristic of the Full Glacial/LGM Interval (Fig. S3). The highest abundances of Cibicides wueUerstorfi and Gyroidinoides polius in the abyssal realm and the corresponding decreased abundances of the Oridorsalis tener species group, Ioanella tumidula, and Eggerellabradyi in both the lower bathyal and abyssal regions (Figs. 55, 57) reflect the presence of an NADW influence, over NAIW, in Modem GB W. Increased bottom-water corrosivity persisted to the present as indicated by the absence of Biloculinella irregularis and Quirtqueloculina venusta , by sharply decreasing abundances of Hoeglundina elegans, and by the highest abundances of agglutinated species in the deepest Gulf (Fig. 56,60). Although very high sediment accumulation rates continue (albeit at slightly lower rates relative to Z2), there is a decrease in the percentage of H. elegans being preserved, possibly indicating an increase in corrosivity of GBW relative to GBW of the Deglacial-interglacial Transition Interval (DGBW). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 185 This idea of increasing bottom-water corrosivity throughout the Holocene, rather than just an increase relative to glacial intervals, is supported by the increase in number of brief, but intense dissolution events seen in the planktic foraminiferal record {Globigerinoidesruber versus Neogloboquadrinadutertrei and PFl; Table 14, Figs. 22, 23,31). The absence of wide fluctuations in the carbonate content (Fig. 12) indicates that throughout the Holocene, carbonate dissolution kept up with surface-water productivity and dilution by incoming siliciclastics. In the late Pleistocene, however, the significantly lower carbonate content, at a time of reduced bottom-water corrosivity, indicates that the amount of incoming siliciclastics must have been enormously high in order to dilute the carbonate record to such a degree. However, the reduced size of the glacial Gulf basin, as well as the lower surface-water productivity, would enhance this dilution factor even if the absolute amount of incoming siliciclastics remained unchanged throughout the late Quaternary. Paleoceanographic Model for Abyssal Gulf of Mexico A simple model for late Quaternary paleoceanographic change in the northwestern Gulf of Mexico can be extracted from the above synthesis. Several of these changes can be linked to glacial-interglacial variations in open-ocean surface and deep/intermediate water circulation and formation. In particular, they reflect changes in source areas for deep and intermediate waters entering the Gulf via the Caribbean. A brief summary of this model is presented in Figures 69-70, and the Proxies for Oceanographic Variability Chart (Fig. 71). Full/Last Glacial Maximum 1. Lowered sea level, creating a smaller Gulf basin (ie. reduced surface-water area). 2. Cool surface-water temperatures, beginning to wane around LGM. 3. Higher surface-water nutrient levels (relative to the present), probably amplified by a smaller Gulf basin. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 186 High/Strong Intermediate-water Benthic Foraminiferal Assemblage Cool-water Planktic Assemblage Eurytypic Planktic Assemblage K elegans Stenotypic Planktic Assemblage Benthic Species Diversity & Equitability co x S. irregularis & Q. venusta c x £ o X 32.6 cm/1000 yr 23.6 cm/1000 yr CaC03 (%) 15.7 cm/1000 yr Total Planktics Low/Weak Full Glacial/ Meltwater/ Deglacial/ Late Holocene/ Last Glacial Younger Dryas Interglacial M odem Maximum Transition RELATIVE TIME Figure 69. Summary diagram graphically depicting changes in the proxies for oceanographic parameters (Y-axis) through time (X-axis). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 187 High/Strang GNAIW Surface Water Nutrient Levels C /3 cc 1—UJ UJ 2 < Surface Water cc Productivity 2 o Environmental X Stability NADW Surface Water Temperature Bottom Water Corrosivity Low/W eak Full Glacial/ Meltwater/ Deglacial/ Late Holocene/ Last Glacial Younger Dryas Interglacial Modern Maximum Transition RELATIVE TIME Figure 70. Summary diagram of the paleoceanographic model for abyssal Gulf of Mexico surface- and deep-waters graphically depicting changes in oceanographic parameters (Y-axis) through time (X-axis). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 188 INC DEC ..INC INC DEC Latest INC DEC NC NC STRONG WEAK STRONG WEAK HIGH STRONG WEAK INC R A INC intergtaciaV (max 2) (max) Modem Degladal INC INC OFC INC P A WEAK 5TR0NG FLUX INC DEC INC C A INC (m axi) (max) NC INC DEC INC DEC Transition (max) INC deleted A P Meltwater/ INC INC (max) DEC INC HIGH WEAK STRONG LOW A C LOW Younger DEC INC INC DEC Dryas ''’o h T depleted A P HIGH Full Glacial/ LOW LOW HIGH STRONG WEAK WEAK STRONG LOW A C N/A Last Glacial INC WEAK STRONG (max) Maximum 1. LOW, MOO, HIGH relative to adjacent intervals. 2. WEAK/STRONG refers to the influence of a particular benthic or planktic assemblage at that time. 3. A/P = presence or absence of particular indicator species, group of species, proxy; C, R = common or rare 4. INC/DEC refers to this interval relative to the preceeding interval. 5. NC = no change. 6. Flux = fluctuating trend. 7. (max) = a maximum. 8. depleted/enriched with respect to °C. 9. M/A = not available. 10. SAR = sediment accumulation rates. 11. R vs. D = number of dissolution events indicated by Globigerinoides ruber versus Neogloboquadrina dutertrei frequencies. 12. Hoeg = relative abundance of Hoeglundina elegans. 13. P & Q = relative abundance of Pyrgoella irregularis and Quinqueloculina venusta. Figure 71. Summary chart outlining late Quaternary variations in oceanographic proxies used to develop the paleoceanographic model for abyssal Gulf of Mexico surface- and deep-waters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 189 4. Increased terrigenous COTg over marine-sourced Corg in bottom-sediments reflecting increase of incoming siliciclastics, although reduction in basin size would serve to amplify this as well. 5. Relatively stable surface- and deep-water environments. 6. Reduced corrosivity of GGBW, relative to the present 7. Strong influence of GNAIW on GGBW. Meltwater/Y ounger Drvas 1. Meltwater influx into northwestern Gulf resulting in reduced surface-water salinites and increased surface-water nutrients (maximum). 2. Increased surface-water productivity due to increased nutrient levels. 3. Continued surface-water warming, with no abrupt cooling coeval with Younger Dryas. 4. Continued surface and deep water environments early on, with decreasing stability occurring later. 5. Brief reduction in bottom- and/or pore-water oxygen levels, possibly related to increased surface-water productivity. 6. No change in corrosivity of GGBW. 7. Strong GNAIW influence on GGBW. Deglacial-interglacial T ransition 1. Warm, but steadily increasing surface-water temperatures. 2. Continued increase in surface-water productivity (maximum), decreasing later. 3. Maximum instability' of surface- and deep-water environments. 4. CaCC>3 preservation maximum. 5. Increase in bottom-water corrosivity of DGB W. 6. DGBW reflecting influence of both GNAIW and NADW. Late Holocene/Modem 1. Sea level at present position. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 190 2. Warm surface-water temperatures. 3. Reduced surface-water productivity and low incoming nutrient levels. 4. Increased marine-sourced over terrigenous sedimentary COTg. 5. Relatively stable surface- and deep-water environments. 6. Increasing corrosivity of GBW. 7. Modem GBW reflecting an NADW influence. Discussion Deep Gulf waters are renewed via flow from the Caribbean over the 1900-m sill at the Yucatan Straits. Today, the composition of deep Caribbean waters is a result of the mixing of both north- and south-sourced watermasses. Northward flowing, oxygen- depleted, nutrient-enriched, and [C 03=]-depleted SAIW (Fig. 72a; Haddad and Droxler, 1996) enters the Caribbean through several passages in the southern Lesser Antilles (Wiist, 1964). However, southward flowing, well-oxygenated, nutrient-depleted UNADW enters the Caribbean over sills at the Anegada-Jungfem passage. The resulting Caribbean deepwaters not only reflect the influence of NADW (Sen Gupta, 1988), they also exhibit a lowered salinity (34.95%o; Wust, 1964), which is the result of mixing with the overlying SAIW. Another indication of the influence of SAIW on Caribbean deepwaters is the poor preservation of carbonate sediments. Haddad and Droxler (1996) suggest that the lowering of [C 03=] in upper NADW, because of mixing with [C 03 =]-depleted SAIW, would increase the corrosivity of Caribbean deepwaters. In turn, these Caribbean waters renewing Modem GBW carry a weak NADW signal and are more corrosive, both of which are taken into account in the proposed oceanographic model (Late Holocene/Modem interval). During the last glacial interval (Fig. 72b), northward flow of glacial SAIW (GSAIW) was restricted to the southern hemisphere (Boyle and Keigwin, 1987; Lehman and Keigwin, 1992a, b; Haddad and Droxler, 1996) due to the southward migration of the polar front (Ruddiman and McIntyre, 1981). This suppression of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 191 MODERN ATLANTIC CIRCULATION j \S " \ Water entering \ ___ CL 0 3 UNADW ”“ Caniten ■ o 0 3 SALINITY 13 S 50° 40' 0° 20° 60° N 70° Latitude GLACIAL ATLANTIC CIRCULATION 0 SAIW E GNAIW 2 •Water entering CL the Caribbean 730 3 0 3 3 13 LSCW 4 5 20° 0° 20° 40° Latitude B modified from Haddad and Droxler (1996) Figure 72. Cross-sections showing Atlantic water mass configuration: a) at the present and b) during the last glacial interval, modified from Haddad and Droxler (1996). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192 GSAIW to south of the equator (Fig. 72b), resulted in a deeper southward-penetration of well-oxygenated, and nutrient- and [C03=]-enriched glacial NAIW (GNAIW), which then entered the Caribbean as renewal waters instead of GSAIW. The formation of north-sourced intermediate waters (GNAIW), as opposed to deep-waters of today (UNADW and LNADW; Figs. 72a, b), is the result of lowered surface-water salinities (Boyle and Keigwin, 1987). These lower salinities, hence densities, allowed surface- waters to sink only to intermediate depths resulting in the formation of less-corrosive, nutrient-depleted GNAIW (Lehman and Keigwin, 1992a, b). This less-corrosive GNAIW influence in Caribbean and Gulf of Mexico deep-waters led to enhanced carbonate preservation in the Caribbean (Galluzzo, 1989; Machain-Castillo et al., in prep) and the Gulf of Mexico as is reflected in the above model. This paleoceanographic model, based on high-resolution benthic and planktic foraminiferal data and developed for the abyssal Gulf of Mexico, lends support to open- ocean thermohaline circulation models that propose a "shallower conveyor belt" for glacial intermediate- and deep-water formation (Boyle and Keigwin, 1987; Lehman and Keigwin, 1992a, b; Fichefet et al., 1994; Haddad and Droxler, 1996). It also supports the notion that the deep- and intermediate-water source area play an important role in governing thermohaline circulation (Duplessy et al., 1988; Charles and Fairbanks, 1992; Haddad and Droxler, 1996). Furthermore, this model agrees well with models developed using chemical proxies and computer modeling. Despite the complex nature of foraminiferal ecology, particular benthic and planktic assemblages are good approximators of paleoceanographic and paleoclimatic change. Conclusions 1. Analyses using high-resolution, parallel benthic and planktic foraminiferal relative abundance data provide a means for examining coeval surface- and deep-water paleoceanographic changes, which yield results comparable to those of geochemical techniques. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 2. Modem distributions of benthic foraminifera from lower bathyal and abyssal environments are extremely complex and are not simply related to bathymetry. These foraminiferal distributions are influenced by the amount and type of sedimentary Corg, bottom- and/or pore-water oxygen levels, bottom-water corrosivity, macrofaunal disturbance, microhabitat heteogeneity, sediment accumulation rates, and sediment mixing. This complex nature of foraminiferal distributions makes placement of these environments into a simple zonal scheme difficult, but it provides a useful analog for examining deepwater oceanographic variability throughout the late Quaternary. 3. Modem planktic foraminiferal frequency data show that the Gulf of Mexico is a planktic foraminiferal ecotone (a mid-latitude and low-latidude mixing zone) characterized by a warm-temperate to subtropical assemblage. This mixing of subtropical and transition zone species reflects the seasonality' of the northwestern Gulf climate, in which surface waters cool sufficiently to facilitate reproduction of transition species in the winter, but not enough to prohibit proliferation of subtropical species. 4. Late Quaternary temporal variations in benthic and planktic foraminiferal abundances, in conjunction with Coro and carbonate data, reveal a detailed paleoceanographic history for the lower bathyal and abyssal environments over the last glacial-interglacial cycle. The data are robust enough for the construction of a paleoceanographic model that explains surface- and deep-water changes in the Gulf of Mexico from the last glacial maximum to the present 5. This paleoceanographic model shows that, in addition to introducing reduced salinities, incoming glacial meltwater brought high nutrient levels to glacial Gulf of Mexico surface waters and may have led to the onset of unstable surface-, and possibly bottom-, water environmental conditions. This period of surface- and bottom-water instability continued into the Holocene and persisted until the middle to late Holocene at which time more stable conditions returned. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6. Variations in carbonate dissolution and surface-water productivity throughout the late Quaternary are recognized by parallel benthic and plantkic foraminiferal relative- abundance analyses. In the northwestern Gulf, productivity and carbonate dissolution during glacial intervals were reduced relative to interglacial intervals, indicating that glacial bottom-waters were less corrosive than those of the present day. Despite an overall increase in carbonate dissolution in the Holocene, a carbonate preservation maximum in the early Holocene abyssal Gulf matches a similar early Holocene event in the western equatorial Atlantic. 7. Benthic foraminiferal relative abundances clearly reflect changing bottom watermass structure and establish a clear link between Gulf of Mexico bottom waters and North Atlantic deep- and intermediate-water source areas. 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F., 1985, Tephrochronology of the western Gulf of Mexico for the last 185,000 vears: Quatemarv Research, v. 23, p. 403-416. Rasmussen, T. L., Thomsen, E., Labeyrie, L., and van Weering, T. C. E., 1996, Circulation changes in the Faeroe-Shetland Channel correlating with cold events during the last glacial period (58-10 ka): Geology, v. 24, p. 937-940. Rasmussen, T. L., Thomsen, E., van Weering, T. C. E., and Labeyrie, L., 1996, Rapid changes in surface and deep water conditions at the Faeroe Margin during the last 58,000 years: Paleoceanography, v. 11, p. 757-771. Roberts, H. H., Singh, I. B., and Coleman, J. M., 1986, Distal shelf and upper slope sediments deposited during rising sea level, north-central Gulf of Mexico: Gulf Coast Association of Geological Societies, Transactions, v. 36, p. 541-551. Rogers, M. A., and Koons, C. 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R„ 1963, Isotopic organic carbon composition of recent continental derived clastic sediments of eastern Gulf coast, Gulf of Mexico: American Association of Petroleum Geologists Bulletin, v. 47, p. 525-531. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 206 Samthein, M., Winn, K., Duplessy, J.-C., and Fontugne, M. R., 1988, Global variations of surface ocean productivity in low and mid latitudes: Influence of C02 reservoirs of the deep ocean and atmosphere during the last 21,000 years: Paleoceanography, v. 3, p. 361-399. SAS Institute Inc., 1993 SAS/STAT® User's Guide, Version 6, Fourth Edition, Volume 1, Cary, NC: SAS Institute Inc., 1989, p. 943. SAS Institute Inc., 1994, JMP User's Guide, Version 3, Cary, N. C., 233 p. Satterfield, W. M., and Behrens, E. W., 1990, A late Quaternary canyon/channel svstem, Northwest Gulf of Mexico continental slope: Marine Geologv, v. 92, p. 51-67. 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K., and Aharon, P., 1987, The last deglaciation event in a Venezuela basin box core: Foraminifera and isotopes: Bulletin de 1' Institut de Geologie du Bassin d'Aquitaine, Bordeaux, v. 42, p. 23-32. Sen Gupta, B. K., Lee, R. L., and May III, M. S., 1981, Upwelling and an unusual assemblage of benthic foraminifera on the northern Florida continental slope: Journal of Paleontology, v. 55, p. 853-857. Sen Gupta, B. K., and Machain-Castillo, M. L., 1993, Benthic foraminifera in oxygen- poor habitats: Marine Micropaleontology, v. 20, p. 183-201. Sen Gupta, B. K., Temples, T. J., and Dallmeyer, M. D. G., 1982, Late Quaternary benthic foraminifera of the Grenada basin: Stratigraphy and paleoceanography: Marine Micropaleontologv, v. 7, p. 297-309. Shiller, A. M., in review, An overview of the marine chemistry of the Gulf of Mexico. Smart, C. W., King, S. C., Gooday, A. J., Murrary, J. 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Further reproduction prohibited without permission. 208 Wendler, S., 1987, Late Quaternary' abyssal benthic foraminifera of the eastern equatorial North Atlantic Ocean: M.S. thesis, Louisiana State University, Baton Rouge, 138 p. Williams, D. F., Trainor, D. M., Guilderson, T., Gamble, R., and Corbin, J., 1988, Calcium carbonate sedimentation on the northwestern Gulf of Mexico margin: A new tool for chemical stratigraphy and depositional modeling: Gulf Coast Association of Geological Societies, Transactions, v. 38, p. 395-397. Wiist, G., 1964, Stratification and circulation in the Antillean-Caribbean Basins 1. Spreading and mixing of the water types, with an Oceanographic Atlas: Columbia University Press, New York, 201 p. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 1 Planktic foraminiferal percentage data for core-top study. 209 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.16 2.64 0.00 0.17 4.62 0.17 0.50 5.28 0.99 0.17 0.83 2.64 0.00 8.42 12.05 18.32 390 606 0.51 0.00 0.00 0.00 0.00 0.00 0.00 4.62 6.60 0.00 0.00 16.67 16.67 12.56 28.72 18.81 IG-41-17 IG-41-18 524 8.02 0.77 0.00 0.00 0.000.00 0.95 0.00 1.28 3.05 3.08 0.00 8.78 17.37 19.27 14.10 468 1.07 1.07 0.57 1.03 1.71 4.01 5.13 0.00 0.00 0.00 0.00 0.21 0.00 0.26 0.21 0.00 0.00 0.00 7.48 8.12 10.88 11.28 20.30 30.56 16.60 IG-38-18 IG-41-13 1.51 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8.38 5.98 10.50 0.00 6.37 17.09 4.19 0.00 0.00 24.29 5.77 442 597 1.81 2.68 6.33 0.23 0.00 0.00 0.00 0.00 0.23 11.76 22.17 21.78 IG-36-2 IG-38-10 0.00 3.41 0.00 2.26 0.34 0.00 0.00 0.23 19.38 10.86 23.41 1.54 3.74 3.57 2.26 0.22 14.76 455 454 645 5.71 10.57 12.87 5.49 7.27 3.57 4.30 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.16 0.00 23.96 20.04 16.90 21.04 20.60 614 3.42 2.86 1.54 0.33 0.44 0.00 0.000.00 0.22 0.00 0.78 0.00 0.17 0.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.65 0.66 0.00 3.423.91 5.05 7.49 10.55 2.20 7.44 16.52 8.38 7.82 15.38 11.89 5.58 0.16 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 PC-1 PC-20.00 PC-3 PC-5 10.75 17.92 18.46 25.99 17.92 G. inflata G. 0. unlversa crasslformlsG. falconensisG. P. finalls Spedes/Sample Number Number Foraminifera Picked G. sdtulaG. S. S. dehtscens dutertrelN. aequilaterialisH. calida G. cuttralaG. fimbriataG. 1.14 0.22 0.22 2.95 0.00 1.34 0.43 G. ruberG. nitidaC. 24.59 10.99 G. G. truncat (L) 0.1G G. tmncatG. (R) digitataG. G. bulloides G. G. saccullferG. conglobatusG. P. obliquiloculataP. G. menardiiG. complex Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 509 1.57 1.96 6.48 3.14 2.95 7.86 0.00 0.00 0.00 0.00 0.00 0.59 0.00 0.00 0.00 0.00 0.98 0.59 12.38 18.86 12.57 30.06 IG-45-14 468 6.20 3.63 0.00 0.00 0.00 2.99 0.00 0.00 0.00 0.43 0.21 0.00 0.43 0.00 0.00 0.00 14.53 14.53 12.39 10.90 12.18 21.58 IG-45-9 489 1.64 5.32 4.09 3.89 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.00 0.00 0.00 0.41 19.22 15.75 22.90 IG-41-29 889 1.57 1.35 1.01 3.37 0.11 0.11 3.94 7.31 0.00 0.34 0.00 0.79 0.11 0.00 0.11 0.00 12.71 12.04 18.20 16.09 18.34 8.38 IG-41.28 601 1.50 1.83 2.83 8.82 0.00 0.11 0.00 0.33 8.99 0.50 0.00 0.00 0.170.67 0.00 0.00 9.320.00 20.58 0.33 0.00 10.32 12.31 12.98 29.12 IG-41-26 470 3.83 6.17 4.47 0.00 0.64 0.21 0.00 8.09 0.00 0.00 0.00 0.00 0.00 10.64 15.32 15.32 IG-41-24 369 3.52 1.28 3.25 0.00 8.94 0.27 7.59 0.27 0.00 8.67 0.00 0.27 0.00 0.00 0.270.00 0.00 0.00 0.00 12.47 16.53 11.1118.43 13.19 20.85 IG-41-23 5.75 1.08 8.41 0.00 2.43 6.64 7.32 0.00 0.00 0.00 7.96 0.00 0.00 0.44 0.00 0.44 0.00 0.22 0.00 0.00 15.49 17.48 18.58 14.16 IG-41-21 544 452 1.84 1.65 1.10 2.57 1.99 0.00 3.49 0.18 0.00 9.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10.48 15.63 11.21 11.58 31.25 IG-41-19 Spedes/SampleNumber S. S. dehiscens G. crasslformisG. P. P. obliquiloculata Number Foraminifera Picked N. N. dutertrei sdtulaG. G. menardiiG. complex saccullferG. truncatG. (R) G. truncat (L) inflata G. 0. universa nitida C. G. cultrataG. fimbriataG. G. calida G. H. aequilaterialisH. G. conglobatusG. G. falconensls P. finalis G. ruberG. G. bulloldesG. G. digitataG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. U to 474 1.05 2.74 3.16 0.00 2.11 7.59 0.21 4.01 0.21 618 0.32 1.27 2.43 3.07 3.80 0.81 3.72 34.47 33.76 542 1.11 1.66 0.00 2.77 5.35 2.59 5.27 3.87 8.74 10.13 0.000.000.00 0.00 0.00 0.00 0.63 0.00 0.00 0.00 0.00 0.000.00 0.00 0.16 0.00 6.27 7.56 6.15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.49 8.67 11.00 BC-4 BC-7 BC-fl 19.93 15.05 13.92 10.15 9.87 10.13 32.66 699 0.00 0.00 0.00 1.13 5.72 2.72 0.14 0.00 BC-3 15.88 17.17 0.00 0.00 0.00 0.76 0.29 0.00 0.00 0.00 15.11 10.38 16.34 3.72 IG-46-12 837 655 0.00 0.72 7.05 4.58 4.72 0.00 0.120.00 0.00 0.00 0.00 0.00 0.00 2.87 5.65 0.008.720.48 0.00 0.00 6.87 1.07 5.58 1.72 0.00 0.00 0.00 0.000.24 0.15 0.15 0.00 0.00 0.00 0.00 12.19 13.74 10.9919.83 12.06 17.71 7.73 34.62 12.90 IG-46-11 6.54 0.00 9.35 10.16 9.16 9.58 14.25 IG-46-9 0.00 0.70 2.66 4.79 9.11 7.18 0.00 0.53 2.13 0.00 0.00 0.00 0.23 0.00 0.00 IG-46-8 583 376 428 2.06 6.00 0.000.00 0.00 0.00 0.00 0.69 3.43 2.93 2.10 0.34 0.00 0.00 0.00 0.00 0.00 1.06 0.23 9.43 3.460.00 14.72 11.32 10.46 6.65 5.37 14.41 9.84 11.32 24.70 57.45 22.43 IG-46-7 660 1.97 0.00 0.00 8.33 0.00 0.00 IG-45-17 523 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6.12 4.85 4.59 2.290.00 1.21 0.19O.S7 0.00 0.19 0.00 0.00 0.00 0.00 2.10 3.33 8.22 11.67 0.000.00 0.00 0.00 0.00 0.00 0.00 I f . 85 14.70 14.91 15.61 22.56 21.97 Number Foraminifera Picked G. crasslformisG. nitida C. P. P. finalis 0. universa sdtulaG. G. falconensisG. aequilaterialisH. calidaG. 2.29 1.52 5.83 1.33 5.37 G. cultrataG. Spedes/SampleNumber IG-45-15 S. S. dehiscens 0.00 G. fimbriataG. digitataG. bulloidesG. 0.00 0.38 0.00 G. saccullferG. dutertreiN. G. inflata G. G. truncatG. (R) G. truncat (L) 23.71 0.00 14.85 0.00 G. ruberG. P. P. obliquiloculata conglobatusG. G. menardii G. complex Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 2 Planktic foraminiferal percentage data for downcore study. 213 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 214 E'Ol I CO t n OO o o o o o o O o c o d d r— 0.2 o 12.8 23.9 G. G. menardil/O.Igsed 1 809 1 1 I 0.5 0.2 1 UE 1 1 Cl o CD c o (0 *T CO 00 c n CO CM 594 349 ~] CO t n 716 i n t o i n CO m Total Total Countedl ; ; 438 ! 1 I 416 f 424 389 1 | | [ 1 489 623 I | | 465 I 322 I 1 J 1 Ol I SO'll N- n n* c n Cl CM O c o O CM i n O CM i n i n t o ’ ci t o c o ’ t o ’ 18.25 18.25 25.26 25.26 31.40 | 22.05 r — | 20.22 20.22 | 43.72 43.72 1 CM CM CM CM Other Other Planks 1 80‘6 I | 15.30 | | | 34.20 33.68 | 1 | | I I I | 22.04 1 I | | 1 29.46 23.21 1 1 I 2 O CM r«* c o CD CO CM V t o 'fr £ 17 Cl CM o ' t o q CO CO CM 9 ) c n CO CM M- o ’ CD i n CM o ’ d 17 r“» c — G. G. saccullfer 1 ] I 89' 89' I Z9V t | | 2.30 | | 10.43 | | | 2.80 1 25.42 16.97 | | O1 ] SO'11 0 I 90 CO o CM o CD c n CM o c n N» CO CO CO I o’ o’ 1.12 1.12 I 9.36 9.36 1 cn to * 6.58 N.’ | ai CM o I [ [ G. crassaformls 1 | 14.31 I 1 | 7-37 9.25 1 ] 7.14 I | | | 8.89 1 000 0 0 | OO'O [ OE'O| | 14.33 | 9 ) CD CM m o o O t o o ci CM CM 00 CO o O o q CM co d d o o’ 0.00 o’ 1 d o’ G. inflataG. E9'9S [ | | 2.86 | 9.95 | | 15.26 | 16.34 ] | | 20.05 | 15.63 | I | CO i n CM CM 9> 9 ) t o 58.49 58.49 31.36 31.36 54.90 54.90 | 48.67 ] 54.60 54.60 | 59.36 | 41.29 | 39.25 39.25 41.41 | | 71.22 | i n G. ruberG. 1 S i'll i'll S 1 1 1 41.26 19> | 1 | 65.87 | 1 [ 52.19 | 48.63 | ] | 42.54 | £8'0 | | I | 53.22 \ | 53.30 | | | | ] EO'Ol f S . ZE'Z CM t o GO o c q o o CO cn CM 00 CO CM c n o o 10 CO »•« CM c n CM o o 10.27 10.27 | dutertrei N. i 1 0 1 | |0Z 1 | | | 1.58 0.43 | | |062 | | 1.55 0.38 | S2 | |SE2 022 o i n O m i n i n i n O i n o i n i n m in N. O r - CM m CO 9 ) O to I a N* *— CM c n CO CO Sample I I | 20 51 260 | | BPX-1-25 | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced | | S a m p le | N. dutertrei | G . r u b e r | , G. inflata | | G. crassaformis | { G. saccullfer | | Other Planks |[Total C ountedl I G. menardii/O.lg sed 1 n i l n t cn I S'O ’ t I CO CO ^5“ \ 3 < CO i f i m m CD n | | BPX-10-25 | | 0 .3 6 1 I 4 6 .3 3 1 3 1 . 1 i / i o . N o GO o d o o o o CO CO CO GO CO 3 7 .8 2 | | 4 8 .1 9 | 3 2 I in CO *->’Im* 'T I . N 0 »jC N r r cn n t CM CO | 1 3 .9 4 I| 3 9 .8 2 1 I 3 0 .0 9 I i 1 i i i I i s-z ... n O tn CO . CM CM TT r t o * o CM cn . | 1 0 .9 6 |[ 2 6 .4 8 | 4 3 8 CO in I 'l E O | o m CO CO CO* ff) 1 1 .7 6 | 4 4 .2 7 | 1 0 .3 7 I 2 2 .1 4 1 1 0 0 81' | '6 1 8 I cn ] L / ' 9 5 | d o o in • | 8 .7 0 | | 7 2 .9 7 | n t j 1 3 .4 0 | I 5 2 9 | L _ . u s i CO o 1 9 0 0 S CM o CM CO CM o o CO I 2 .1 0 | 1 5 .3 7 1 CM q m CM . - r q c CM q I - r CM O i 4 7 . 8 5 303 | 98‘E | E ‘ 8 9 I ...... L ' l - 2 9 I i a - t 1 CO* in co’ . N CO rs. CO CM V CO . N o m CM GO in 1 3 .5 1 | CO | 2SS I n i oo o o o CO (D CM o «— o ...... 1 8 5 1 2-17 ] 1 1-09 ] CM o o co* l C CO o 1 1.3 7 || 4 8 .4 4 || 1 0 .3 5 1 [ 1 0 .3 5 |1 2 0 . 5 1 1 5 1 2 CM I i w 1 in n t CO fs. CO in q 00 . r* cn CO o d cn | | 2 9 .4 9 I 6 5 1 2 E 0 S6' | I 'l 6 S | O | 2 .9 9 || 5 4 .9 4 | | 5 .7 5 II 3 .2 2 | | 2 1 .1 5 |1 4 35 | CM in CM* in in CM “* r CO CM CO CM cn cn o CO m IM o CM CO O cn o CO . N co' n i CM cn . N l O CO* CM m CM GO* q CM 01 0 CM q CM r*. n t | U Z S rf- o 0N. N 00 rs. o TT CO | 5 3 .5 8 j| 1 0 .6 3 j I 2.66 n CM l C o ] l '6 8 S I s CO fs. fs. CM i c q o cn « O CO O 1 5 3 .1 9 I 1- | 16-8 I cn o o | '9 ltr o O I 5 2 .3 8 | | 1 9 .3 6 | | 1 2 .4 7 | I 8 42 | 130 1.80 1.64 3.27 5.24 6.87 0.82 0.82 0.16 5.24 0.16 7.36 0.49 14.57 10.97 12.60 27.99 120 1.18 423 611 1.65 2.36 8.51 0.24 4.96 7.09 5.20 8.75 0.24 11.82 15.84 23.40 307 1.95 1.30 0.98 8.47 11.07 12.05 8.75 18.57 11.07 27.69 100 110 424 3.54 3.07 0.24 0.65 11.08 90 1.23 1.38 1.38 1.65 3.85 5.23 3.54 6.92 3.07 6.19 7.54 0.31 9.23 15.33 0.15 0.154.00 0.24 8.49 0.15 19.38 12.03 39.08 37.74 80 1.60 437 650 5.72 7.55 0.23 0.46 0.92 0.92 13.50 16.48 15.79 27.69 1.10 3.87 3.87 9.15 6.35 0.14 0.14 0.14 0.14 14.78 28.45 26.38 60 70 557 724 1.44 1.38 1.44 3.77 3.95 0.18 0.83 0.18 6.64 0.36 0.97 0.90 0.41 16.34 19.39 12.93 11.05 32.14 T c 6 50 o 1.96 1.09 460 1.09 3.48 0.22 0.36 0.65 18.48 17.17 21.52 20.65 ------~ 1 366 1.91 1.64 2.61 1.37 1.09 0.27 6.56 18.31 15.30 ~ ~ 4.92 30 40 600 7.67 3.00 6.00 0.17 0.83 0.33 0.83 16.17 19.67 25.17 31.42 ------20 1.41 496 3.02 3.63 3.83 ZMZ 2.02 0.50 12.70 10.08 13.71 27.42 23.19 15.83 18.31 ------418 3.11 5.SO 3.83 3.83 7.6G 0.24 9.33 0.48 0.72 17.22 17.22 30.06 ------PC-1-10 — G. inflata G. P. obliquiloculataP. S. dehiscens 0. universa G. truncatG. (L) dutertreiN. ruberG. G. sacculiferG. G. truncat (R) G. conglobatusG. C. nitida C. Species/Core Depth (cm) H. aequilaterialisH. G. fimbriataG. G. crassiformisG. sdtulaG. G. menardiiG. complex builoidesG. digitataG. G. G. falconensis G. calida G. G. ungulataG. Total Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 587 360 1.19 1.87 6.47 5.28 5.45 2.04 2.21 2.04 0.68 0.17 0.17 65.93 340 1.99 702 2.42 3.75 3.13 2.71 3.13 9.83 2.71 2.73 0.57 0.28 0.14 0.71 14.96 12.68 44.16 320 420 1.43 2.86 6.67 5.95 0.71 0.28 6.67 4.76 0.24 0.24 0.28 8.57 0.71 0.95 15.48 40.00 300 1.18 1.65 6.38 0.95 7.09 0.24 0.47 0.24 0.240.95 1.43 0.95 10.87 18.68 34.28 514 423 280 1.95 5.64 3.55 3.10 2.53 0.78 3.31 0.78 3.31 4.67 0.19 0.39 16.54 14.40 5.91 260 496 1.01 0.19 3.23 7.06 0.81 7.20 0.20 8.87 0.40 0.20 12.70 30.24 44.75 20.77 ~~0.20“ 240 1.90 1.52 1.81 2.29 11.69 5.33 0.81 6.29 0.57 2.29 0.38 19.62 33.33 ------502 525 1.59 220 1.00 5.14 6.57 8.00 2.99 0.40 0.40 0.20 9.96 0.80 12.35 16.73 13.33 44.82 1.11 1.20 2.58 4.98 0.37 0.18 0.37 0.370.37 0.60 16.61 14,21 36.53 ------180 200 1.84 381 542 1.05 1.29 0.40 1.57 6.30 9.71 5.90 2.62 9.97 4.98 0.52 13.39 10.15 10.76 32.55 ” ------5.05 2.02 0.51 0.25 7.32 0.25 10.86 42.93 150 160 1.26 2.30 1.52 2.51 8.79 10.61 9.19 0.42 0.25 9.000.42 15.40 0.63 0.26 8.16 0.63 1.26 0.21 0.21 1.52 11.09 140 522 478 396 1.53 1.72 1.15 4.79 0.25 0.26 7.09 4.60 10.46 6.32 0.19 2.49 9.39 50.19 43.93 _ a 5 7 _ ~_9l96_ Species/Core Depth (cm) S. S. dehiscens 0. universa N. dutertreiN. P. P. obliquiloculata sacculiferG. falconensisG. G. inflata G. G. ruberG. crassiformisG. sdtulaG. nitida C. G. truncatG. (R) G. truncat (L) G. menardii G. complex conglobatusG. aequilaterialisH. G. digitataG. Total G. calida G. G. bulloides G. ungulataG. G. fimbriataG. with permission of the copyright owner. Further reproduction prohibited without permission. 80 1.22 491 1.43 1.83 1.83 5.91 3.67 0.41 0.20 0.81 45.01 628 1.11 5.256.05 5.09 0.16 0.16 0.16 2.072.07 1.63 2.85 15.92 19.35 11.15 8.76 42.20 60 70 396 1.26 1.01 1.77 9.34 7.83 0.51 4.29 6.05 0.51 0.80 12.37 10.10 6.69 10.86 50 418 1.20 0.76 4.55 4.55 0.72 0.16 9.33 0.24 0.72 0.24 0.51 47.37 38.89 635 1.73 3.59 1.73 0.796.93 0.48 7.09 7.66 0.94 0.31 0.94 0.96 11.02 8.61 12.28 9.81 38.58 30 40 465 1.94 1.29 6.88 5.51 0.86 9.25 0.22 0.43 12.04 12.13 13.55 25.16 20 515 0.19 0.97 7.31 0.19 0.39 15.53 12.43 22.33 41.75 21.08 520 5.96 2.69 1.36 2.69 0.19 0.77 0.19 18.85 10.77 3.88 30.00 20.96 PC-2-15 450 1.24 1.49 0.96 0.25 0.25 0.25 14.14 55.83 1.45 414 403 440 1.93 2.17 6.45 6.15 0.78 0.97 3.86 4.96 4.59 ~ 4.11 1.99 11.59 ------549 420 1.82 4.59 0.25 2.37 0.18 5.65 0.91 2.17 3.23 0.91 0.91 11.11 13.53 9.68 59.20 48.55 — ■ ■ — 400 1.63 5.23 0.91 2.94 3.27 2.55 0.33 0.18 8.17 10.750.33 0.48 6.54 380 529 306 1.89 2.27 1.63 0.19 0.19 6.620.19 12.75 2.27 12.75 2.55 0.19 0.19 2.46 2.84 0.95 0.33 0.38 12.10 67.11 44.12 —a i i T “ Species/Core Depth (an) S. S. dehiscens G. menardiiG. complex conglobatusG. P. P. obliquiloculata saccullferG. G. truncatG. (L) N. N. dutertrei G. ruberG. 0. universa sdtulaG. aequilaterialisH. G. falconensisG. G. G. truncat (R) G. inflataG. crassiformlsG. C. nitidaC. bulloldes G. G. ungulataG. digitataG. Total G. calida G. G. fimbriataG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 240 610 1.64 1.64 1.15 2.13 0.16 0.82 9.34 4.43 0.66 41.80 22.46 215 1.48 2.59 0.37 2.47 4.56 6.41 3.93 0.12 0.16 0.740.12 0.16 0.62 0.66 0.25 16.03 40.57 20.84 8.85 200 1.92 1.44 0.62 416 811 1.92 2.22 1.68 6.25 0.72 0.24 0.96 4.33 2.88 0.24 0.96 19.71 180 1.16 1.35 1.16 0.77 0.96 0.19 0.19 7.71 7.45 2.31 2.31 10.40 56.65 49.28 444 519 1.58 1.13 4.05 1.73 0.23 2.03 11.49 7.51 70.72 155 160 545 7.52 2.57 3.38 0.37 0.55 0.23 0.37 5.87 3.832.02 5.59 2.20 1.35 0.55 0.92 60.18 150 1.50 467 4.71 5.32 9.42 6.85 9.64 11.01 2.57 0.55 0.86 4.28 0.43 140 1.83 2.98 2.29 0.43 4.59 0.23 9.86 0.23 0.43 7.11 2.29 1.93 0.46 0.43 4.13 4.07 56.65 52.46 130 573 436 1.92 0.46 1.57 3.14 5.76 1.22 8.03 5.93 0.35 0.52 0.87 0.17 11.52 6.19 51.83 120 1.67 1.94 2.27 1.11 1.22 0.69 2.22 3.66 4.17 0.56 3.06 0.28 0.56 44.44 110 1.77 1.94 3.37 5.50 5.50 5.83 0.18 7.98 6.39 0.89 11.52 12.50 11.88 13.33 100 1.21 494 564 360 1.21 1.42 2.30 3.04 3.24 0.71 4.66 8.50 0.81 2.30 3.04 2.30 0.40 0.18 0.402.02 0.89 0.61 0.18 8.50 56.07 42.55 90 682 5.72 1.03 3.37 4.55 5.72 4.86 0.59 0.73 2.49 0.73 0.59 0.73 14.52 11.00 48.24 Species/Core Depth (cm) G. menardii G. complex G. truncat (R) P. P. obliquiloculata S. dehiscens N. N. dutertrei inflata G. nitida C. aequilaterialisH. G. truncatG. (L) G. conglobatusG. G. sacculiferG. ruberG. 0. universa crassiformisG. sdtulaG. falconensisG. calida G. G. bulloides G. ungulataG. fimbriataG. digitataG. Total Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 414 1.21 1.21 2.17 0.24 8.21 3.86 0.24 0.24 0.72 14.25 14.01 27.29 30 1.58 3.76 3.96 9.90 0.40 0.99 0.79 0.40 0.40 25.15 25.94 26.33 20.20 20 517 505 1.35 1.74 3.37 1.35 7.93 5.03 2.90 0.58 0.19 0.19 17.41 11.22 3.17 15.86 21.66 10 1.48 1.55 405 2.72 2.96 2.22 0.25 0.99 0.99 0.19 10.37 13.33 12.84 10.83 546 1.10 1.23 7.14 1.47 3.85 5.68 3.48 0.55 0.920.18 1.23 3.48 0.55 6.96 3.30 0.18 8.97 19.23 23.95 38.64 19.75 PC-4-5 395 1.95 5.84 7.78 8.95 0.78 0.78 0.78 0.39 10.12 33.07 380 1.06 472 257 1.48 0.64 0.78 4.45 2.33 2.54 3.50 14.62 23.35 14.83 40.68 360 4.24 7.84 4.00 0.71 2.35 0.24 0.24 0.64 1.95 0.47 0.42 13.41 8.26 340 1.74 0.47 2.90 40.00 0.58 0.71 0.21 0.58 2.51 1.18 45.07 23.06 320 537 517 425 1.49 1.12 0.39 7.08 7.16 0.93 2.23 2.90 2.42 2.32 3.29 4.84 0.56 0.19 0.74 12.85 10.83 10.61 11.41 5.65 44.88 300 1.16 603 1.99 1.49 6.47 9.45 5.14 8.75 11.61 2.16 8.29 12.77 1.30 280 2.13 2.13 0.38 0.132.01 2.65 1.49 0.38 4.64 0.38 13.03 52.76 40.30 1.45 5.39 1.63 260 553 798 1.45 1.25 2.89 5.24 8.15 6.63 0.18 0.13 0.18 2.53 1.88 0.18 0.18 9.95 0.18 0.18 0.88 15.37 13.02 4.39 45.39 Species/Core Depth (cm) N. dutertreiN. G. ruberG. S. S. dehiscens G. truncat (R) truncatG. (L) G. inflata G. 0. universa G. crassiformisG. nitida C. P. P. obliquiloculata saccullferG. conglobatusG. G. menardii G. complex G. sdtulaG. G. G. falconensis H. aequilaterialisH. G. calida G. G. fimbriataG. Total G. bulloides G. G. ungulataG. digitataG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. \i 150 1.52 1.07 1 .6 8 1 .2 2 5.34 6.25 0.46 0.15 7.16 0.30 5.18 19.51 42.68 140 472 656 1.91 4.73 1.69 6.14 2.74 2 .1 2 3.81 5.51 5.93 0 .2 1 0 .2 1 0.42 14.41 130 1.07 1.07 1.69 3.37 3.83 5.21 4.03 0.15 0.46 10.28 7.84 13.50 0 .S 1 2 0 467 652 1 2.57 2.15 3.64 1.53 0.43 0.43 6.64 7.98 0 .2 1 0 .2 1 0.43 12.63 14.13 44.11 47.70 45.76 115 464 1.08 5.17 4.71 7.54 0 .8 6 3.45 0 .2 2 5.39 4.53 8.14 0 .2 2 0 .2 2 0 .2 1 0 .2 2 1 1 0 3.51 2 .1 1 0.53 2.28 0 .8 8 0 .8 6 0.53 0.35 0.18 0.65 10.37 10.54 9.91 15.64 16.81 558 569 105 5.02 0.18 0.90 4.48 7.53 0.54 0.35 8.24 4.75 0.36 9.68 0.72 48.57 46.40 42.89 1 0 0 459 3.27 1.97 1.58 0.65 0 .2 2 0.44 11.55 39.87 90 421 7.84 9.15 7.89 9.74 6.75 0.24 2.18 1.25 0.71 0.65 8.55 0.71 80 1.18 1.43 1.96 2.52 7.39 11.64 9.15 0.67 3.80 2.61 2.69 0.34 6 .2 2 0.34 12.44 9.03 8.50 13.61 70 534 595 1.87 3.53 0.48 3.05 3.37 4.03 0.19 9.18 5.38 3.80 8.05 0.19 0.56 11.42 18.54 34.08 42.35 42.04 459 1.09 1.50 1.74 2.81 1.31 2.40 2.81 2.18 3.92 5.43 9.80 0 .2 2 0.44 11.55 1 1 .1 1 50 60 1 .0 2 1 .0 2 1.53 6.23 5.98 2.54 2.04 3.56 4.33 0.13 0.25 18.32 21.13 10.94 42.11 33.12 Species/Core Depth (cm) H. aequilaterialisH. S. S. dehiscens G. digitataG. G. falconensisG. bulloides G. G. sdtulaG. G. ruberG. O. universaO. P. obliquiloculataP. dutertreiN. G. menardii G. complex G. calida G. ungulataG. fimbriataG. Total 786 G. crassiformisG. nitida C. G. inflata G. G. sacculiferG. conglobatusG. G. truncat (L) G. G. truncat (R) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CCL 474 1.27 1.48 2.53 2 .1 1 0.42 0 .2 1 0 .2 1 0 .2 1 17.93 370 380 1.72 2.95 1.29 1.48 1.93 1.93 6.65 6.75 3.43 1.50 0.43 0.63 2.79 1.90 0.43 0 .2 1 0 .2 1 0.43 16.74 13.52 11.60 44.21 48.31 529 466 360 7.18 0.38 4.35 2.65 0.38 0.76 2.58 0.38 0.95 4.73 0.38 4.91 0.38 0.57 13.42 53.50 1.48 5.19 5.10 50.86 320 340 445 405 1 .1 2 1.80 1.98 3.15 1.73 3.37 7.41 6.07 6.97 13.33 8.31 0.45 0 .2 2 0.90 0.25 0.90 3.46 0.45 17.75 14.32 48.54 1 .0 0 1 .0 0 6 .0 0 0.50 0.67 11.67 66.83 ------280 300 439 600 1.14 0.17 6.83 6.50 4.56 7.06 6.83 1.67 3.87 1.17 0 .6 8 0.23 0.50 478 " 1.46 2.51 2.33 1.46 3.35 3.35 3.97 5.65 2.09 0.63 0.84 0.23 0.84 9.00 0.84 0.46 0.63 65.90 65.60 240 260 1.41 1 .2 0 3.01 0 .2 0 2.81 0 .2 0 0 .2 0 0.60 0.60 ~ 498 2 2 0 1.24 485 " 1.65 0.60 1.65 4.02 1.03 2.27 10.44 3.71 6.19 2.47_ 9.07 5.02 0 .2 1 0 .2 1 0.41 10.72 4.82 22.06 9.24 _ 2 0 0 1.11 0 .2 1 1 .6 6 3.51 2.96 0.92 0.18 0.74 14.60 36.97 36.91 55.62 " " 0.18 " 8 8 . 180 1.55 0.18 1.32 1.32 3.97 3.75 6.62 0 .6 6 8.61 12.940 0 .2 2 0.44 '" 8.17 6.47 0.44 11.26 1.85 39.74 "2765" 5.73 ------160 507 453 541 1.58 1.78 1.97 2.37 2.76 ' 4.34 5.52 6.31 7.89 8.39 9.98 0 .2 0 0.39 16.96 47.53 ~ 0 .3 9 ' ------. . universa Species/Core Depth (cm) N. dutertreiN. G. crassiformisG. sdtulaG. G. inflata G. 0 aequilaterialisH. G. ruberG. G. menardiiG. complex S. dehiscens G. truncatG. (R) C. nitidaC. G. falconensis G. fimbriataG. G. conglobatusG. G. truncat (L) P. P. obliquiloculata sacculiferG. Total G. bulloides G. ungulataG. G. calida G. G. digitataG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 223 590 679 2.06 3.39 0.15 3.83 2.65 0.29 0.44 9.57 50.07 21.35 1.56 1.56 1.56 4.69 10.94 6.1918.75 550 570 449 64 3.79 2.906 .6 8 6.25 0.89 0.450.45 1.56 0 .2 2 7.13 7.81 0 .2 2 0.45 1.56 6 .0 1 42.32 43.75 530 491 1.43 1 .0 2 5.70 0.41 0.61 0 .2 0 0.61 0 .2 0 6.52 0 . 2 0 9.78 19.76 10.91 11.41 17.59 41.34 434 1.15 0.23 5.07 4.84 2.53 3.69 0.69 0.92 0.81 0.23 21.89 43.78 500 510 492 1 .2 2 1 .0 2 1 .0 2 0.41 0.81 0.46 3.460.41 6.45 0.23 7.11 0.41 8.94 7.83 14.84 53.46 189 490 1.06 3.17 5.82 5.29 0.53 2.65 4.76 0.53 2 .1 2 3.70 7.94 6.91 13.76 42.86 480 538 1.67 5.82 1.67 1 .1 2 0.19 0.74 2.04 0.56 2.04 0.74 4.65 15.61 12.45 50.00 " 1.37 1.18 1.10 1.57 3.53 2.55 0 .2 0 5.49 6.51 3.73 3.73 9.80 440 460 489 510 1.64 9.61 0 .2 0 0.61 1.96 0.41 3.68 2 .6 6 2 .8 6 0 .2 0 3.48 4.91 11.96 9.20 10.84 13.29 36.40 51.76 115 430 1.74 1>4 2.61 3.48 0.87 2.61 4.35 0.87 6.96 12.17 38.26 T h lc T 1.69 1.27 5.06 0 .2 1 0 .2 1 4.01 5.91 8 .8 6 55.91 400_ 420 1 .0 0 K26 " 556 474 1.80 1.26 1.05 0.36 0.63 4.14 1.27 5.76 3.16 6.96 _ 5.760.36 0.63 4.50 6.09 7.91 12.59 10.13 52.52 S. S. dehiscens P. obliquiloculataP. Species/Core Depth (cm) menardiiG. complex conglobatusG. G. truncatG. (R) G. sacculiferG. aequilaterialisH. bulloides G. ungulataG. G. G. truncat (L) N. dutertrei sdtulaG. G. fimbriataG. digitataG. G. ruberG. nitida C. falconensisG. calida G. G. inflata G. O. universa crasslformisG. Total Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 to 80 289 1.37 1.37 1.37 2.75 5.50 1.37 0.69 2.06 0.69 5.15 0.69 12.71 64.26 391 1.53 1 .0 2 3.84 9.97 2.30 4.35 0.51 7.42 0.26 57.54 60 70 617 1.62 1.62 4.09 3.07 1.28 2.27 0.32 0.51 0.974.05 1.79 0.16 3.24 3.58 0.16 2 .1 0 0.16 12.46 14.40 53.40 50 444 5.86 1.13 2.93 3.60 3.60 0.45 0 .6 8 0.90 3.38 0.23 0 .6 8 76.58 40 314 1.91 5.10 0.32 0.32 0.96 7.64 6.05 0.32 0.32 0.64 0.32 0.96 63.69 30 1.43 350 4.57 0 .8 6 0.29 0.29 14.57 11.46 1 0 .0 0 10.57 2 0 553 1.27 5.79 5.79 4.00 2.89 2.35 2.29 2.35 3.98 1.71 0.72 0.29 2.17 1.14 9.22 0.18 0.54 7.78 0.18 11.93 42.86 48.00 537 0.19 4.83 2.42 0.19 7.81 2.04 0.19 0.37 0.74 9.67 0.19 10.97 665 IG-41-15-10 675 1.48 5.93 4.44 2.23 5.04 0.93 3.41 0.89 0.19 0.15 14.67 11.15 17.63 42.52 45.91 ' a30 “ 2 0 . 660 1.21 3.23 0 4.03 3.56 6.45 9.27 10.69 39.92 ------~~ 4^64 ~~ ------650 1.30 1.49 4.83 0.19 5.39 0.37 0.37 12.08 1 0 .2 2 40.52 J8.03 1875 _V .30 1.61 '" 5 3 8 496 572 1.75 1 .2 2 1 .2 2 6.99 2.97 17.48 12.41 3.90 9 610 630 540 1.48 0.52 1.11 6.48 9.26 3.70 2.45 0.93 4.44 2.41 4.63 10.14 0.19 1 0 .1 54.81 42.83 ” 0 .3 7 ~ Species/Core Depth (cm) S. S. dehiscens P. obliquiloculataP. saccullferG. G. calida G. C. nitida C. G. falconensis aequilaterialisH. G. fimbriataG. G. bulloides G. G. truncatG. (L) N. dutertrei G. conglobatusG. truncatG. (R) ruberG. inflata G. universaO. sdtulaG. Total G. ungulataG. G. menardiiG. complex G. crassiformisG. G. digitataG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 260 5.79 1.58 6.84 6.05 3.16 0.26 0.79 0.26 14.47 12.37 376 380 240 1.06 0.53 1.60 0.26 1.06 3.19 2.63 3.72 3.46 2.13 0.53 6.91 4.79 0.27 0.80 0.27 2.89 14.89 52.39 41.58 1.37 2 2 0 3.19 3.42 3.46 0.46 0.23 0 .6 8 9.57 0.23 0.23 17.77 2 0 0 1.19 3.95 4.74 20.96 3.75 1.59 4.94 0.91 3.16 7.11 0 .2 0 0.40 0.40 0.59 10.08 59.49 39.41 464 506 439 1.72 1.94 3.02 3.23 3.02 0 .2 2 0 .2 2 0 .2 2 0 .8 6 0 .2 2 10.56 57.54 160 180 470 1.06 1.06 1.29 5.72 4.31 2.97 3.18 2.75 1.08 0.85 0.42 10.81 14.83 11.23 10.56 43.01 150 438 1.14 1.06 7.05 4.77 0.23 0.23 0.45 4.77 0 .6 8 0.23 14.32 10.23 51.59 1.32 5.79 2.05 0.79 0.23 1.06 3.16 0.79 2.05 0.53 0.53 130 140 411 380 1.21 1.21 7.28 3.95 5.10 0.53 2.67 0.49 0.24 0.73 10.19 15.26 20.87 18.95 50.00 48.16 511 1.17 0.78 1 1 0 1 2 0 374 1.071.07 2.54 0.26 2.41 1.76 3.21 7.49 5.87 2.94 0.80 12.92 6.422.14 10.76 0.59 0.27 0.53 9.63 2.94 60.43 59.30 1 0 0 1 .2 2 1 .2 2 1 .2 2 2 .2 0 2 .2 0 5.13 6.60 3.42 1.60 1.37 1 1 .0 0 90 468 409 1.07 1.07 1.07 1.50 1.71 0 .2 1 3.42 3.42 2.992.78 1.47 9.40 0.43 4.27 1 0 .6 8 59.40 60.88 . universa. S. S. dehiscens dutertreiN. ruberG. 0 G. truncatG. (L) crassiformisG. G. conglobatusG. Species/Core Depth (cm) C. nitida C. falconensisG. aequilaterialisH. G. G. truncat (R) sdtulaG. ungulataG. G. inflata G. P. obliquiloculataP. G. bulloides G. G. fimbriataG. digitataG. G. menardii G. complex sacculiferG. G. calida G. Total O CD Q. O Q_ with permission of the copyright owner. Further reproduction prohibited without permission. to C\ 500 2.52 4.42 2 .2 1 0.63 0.63 3.47 2 .2 1 0.32 2.84 0.95 0.32 6.62 19.56 41.64 490 1.84 488 316 3.07 1.64 0.61 2 .6 6 4.30 0.41 2.52 0 .2 0 5.33 0.41 53.48 21.72 9.15 551 480 1.27 1.63 1.27 1.27 3.99 2.72 4.30 0.73 3.45 0.73 0.18 12.16 25.95 44.46 1.59 2.27 0.91 5.23 2.27 0.18 0.23 3.41 0.45 0.45 1 0 .6 8 12.50 53.18 567 440 440 460 1.76 1.94 0.23 0.53 0.35 6.59 0.18 0.18 20.63 45.68 20.28 420 508 1.77 1.77 6.70 0 .2 0 0 .2 0 0.79 0.79 1.76 0.39 10.83 400 1.95 1.95 1.71 3.66 2.36 0.24 7.80 11.81 0.49 0.24 0.59 15.12 6.50 15.85 50.24 62.01 380 364 410 8.24 0.27 2.75 0.27 2 .2 0 9.34 3.02 0.27 0.27 0.27 0.73 23.63 37.36 360 375 1.07 1.33 5.07 10.44 0.27 0.80 0.27 2.13 1.65 0.27 4.80 13.33 13.87 340 2.62 1.60 0.26 2 .1 0 7.35 2.89 3.15 8.53 0.79 0.52 0.53 0.26 8 .6 6 17.59 53.81 46.13 320 1.52 460 381 3.04 5.22 1.52 0.43 2.83 0 .2 2 0.65 1.29 1.51 1.08 0.43 0.65 4.31 0.43 0 .2 2 14.44 13.48 14.66 10.34 14.13 49.78 56.30 280 300 1.33 528 464 1.89 5.68 5.68 1.14 1.51 0.19 0.19 3.98 9.85 0.76 0.76 0.95 0.19 17.61 49.81 S. S. dehiscens dutertreiN. G. truncatG. (R) Species/Core Depth (cm) P. P. obliquiloculata G. menardiiG. complex G. sacculiferG. G. truncat (L) G. conglobatusG. G. ruberG. inflata G. O. O. universa G. crassiformisG. aequilaterialisH. G. sdtulaG. G. digitataG. G. bulloides G. C. C. nitida G. G. falconensis G. calida G. ungulataG. fimbriataG. Total i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to 720 409 1 .2 2 1.46 5.85 2.44 0.24 0.73 0.49 0.24 10.24 1 2 .2 0 20.73 41.95 700 424 1.18 4.71 2.59 2 .1 2 0.24 0.47 0.71 1.46 0.71 0.73 0.24 14.35 46.59 608 680 2.96 0.33 0 .6 6 0.16 0.82 0.49 3.06 1 1 .0 2 8 . 0 0 14.14 11.76 48.85 660 1.49 1.49 1.48 3.29 6 .2 0 2.48 9.18 4.61 2.73 0.74 0.50 0.16 0.99 0.25 13.15 18.86 13.16 38.96 1 .0 0 1 .0 0 8 .0 0 15.60 45.60 620 640 354 500 402 1.41 1.98 2.54 6.80 0.56 2.23 0.99 0.28 0.60 2.54 0.40 0.74 0.16 0.85 0.40 14.12 600 381 1.31 3.15 2.62 0.56 1.80 2.62 0.52 2 .1 0 0.52 53.02 40.96 573 590 1.75 1.57 1.57 1.05 2.79 2.62 5.76 5.77 2.26 4.80 2.27 5.41 12.07 18.36 5.06 7.87 13.28 11.40 3.14 1.57 0.17 0.17 2.092.97 2.36 0.28 2.60 0.17 0.35 63.87 611 580 1.14 1.63 6.05 2.78 6.05 0.33 0.33 71.24 1 .2 0 0.13 3.99 0.13 0.80 2 .6 6 0.93 4.92 4.25 4.79 2.29 0.27 0.16 11.44 2.45 587 750 1.36 1.46 3.41 0.34 0.27 0.98 4.09 2.73 6.81 6.47 0.34 19.25 13.80 1.33 38.16 65.03 348 540 560 570 1.15 2.30 2 .0 1 0 .8 6 0 .6 8 0 .8 6 0.29 0 .8 6 34.77 316 3.48 6.61 0.32 8.23 18.10 21.84 19.25 . . universa 4.11 Species/Core Depth (cm) 520 N. dutertreiN. S. S. dehiscens G. sdtulaG. G. falconensisG. 2.85 4.89 2.04 G. menardiiG. complex obliquiloculataP. 5.06 G. sacculiferG. G. truncatG. (L) ruberG. 1.58 43.35 G. conglobatusG. 0 C. nitidaC. 0.40 0.16 H. aequilaterialisH. 0.63 G. G. truncat (R) 6.33 3.45 G. Inflata G. G. crasslformisG. 1.58 4.60 G. bulloidesG. calidaG. ungulataG. fimbriataG. 0.32 0.32 0.51 0.27 0.16 1.40 0.26 G. digitataG. Total Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 640 9.20 9.05 0.16 2.03 0.16 0.16 0.16 0.16 10.92 15.13 35.10 80 1.07 1.25 5.01 3.04 0.36 0.31 0.18 0.18 0.54 0.72 2.03 0.18 10.38 5.15 13.42 9.05 11.27 23.79 29.70 70 721 559 1.24 1.24 1.94 8.44 8.99 0.14 0.18 0.28 8.44 0.14 0.28 12.03 12.45 43.57 60 467 1.07 4.48 2.35 2.77 0 .2 1 0.85 8.74 0 .2 1 0.850.64 0.83 0.43 13.22 13.86 2 1 .1 1 29.21 50 349 1.72 6.30 0.57 2.29 0.29 8 .8 8 0.29 0 .8 6 12.61 13.75 10.89 37.25 40 1.14 350 1.42 3.42 4.30 3.42 6.84 9.69 4.56 7.98 0.28 0.28 0.28 12.25 30 535 1 .6 8 1 .6 8 6.36 0.19 2.62 0.37 10.84 12.34 13.11 12.15 39.25 35.33 2 0 357 1 .6 8 5.04 9.80 4.20 0.28 8 .6 8 2.24 3.18 0.84 1.87 0.28 12.89 15.97 7.48 37.82 1.01 4.03 6.04 2 .6 8 0.34 0.67 0.670.34 0.28 19.80 11.74 17.79 13.76 21.14 IG-41-21-10 780 425 298 8.39 2.56 0.70 1.63 3.26 2.33 8.62 0.23 0.23 2.56 0.47 0.93 0.70 0.93 13.29 18.88 34.27 770 1.89 1.47 1.26 3.37 1.47 1.26 0.63 0.42 0.42 0 .2 1 0 .2 1 0.42 0.42 17.47 11.16 1 2 .2 1 39.37 760 1.98 6.32 452 473 3.30 8.35 0 .8 8 3.74 2 .8 6 9.45 0 .2 2 0 .2 2 0.44 0 .6 6 0 .8 8 0.44 11.87 54.07 740 405 3.17 3.90 1.71 2 .2 0 5.37 1 .2 2 0 .6 6 2 .2 0 8.29 7.32 0.24 0.98 0.24 2 .6 8 0.73 59.76 Species/Core Depth (cm) S. S. dehiscens G. sacculiferG. P. P. obliquiloculata G. menardiiG. complex conglobatusG. G. truncatG. (R) G. truncat (L) N. N. dutertrei inflata G. universaO. G. crassiformisG. sdtulaG. G. falconensis aequilaterialisH. G. ruberG. C. nitida C. bulloides G. G. calida G. ungulataG. digitataG. Total G. G. fimbriata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 280 568 2.29 3.17 3.70 0.18 0.70 0.53 0.53 0.35 0 .8 8 0.70 0 .8 8 11.27 53.17 260 540 1.85 3.14 4.05 5.73 0.18 8.32 0.18 0.55 0.37 0.18 15.34 17.61 12.38 49.17 240 330 7.53 5.42 6.93 5.42 2.59 0.30 2.71 7.83 6.63 4.82 0.30 0.30 0.60 0.30 50.90 2 2 0 375 1.58 1.05 1.32 6.32 2.89 2 .1 1 0.53 3.95 10.53 13.95 41.84 2 0 0 508 6.27 7.89 8.63 7.06 0 .2 0 0 .2 0 0 .2 0 6 .8 6 0.59 4.90 8.82 6.05 2.75 0.59 0.59 46.86 1 0 0 756 5.15 1.85 3.33 0 .6 6 0.53 7.27 0.26 0 .6 6 0.92 1.76 15.46 44.39 160 1.09 3.83 1.90 2.99 7.88 6.25 9.51 0.54 6.79 0.82 1.59 0.27 0.54 0.40 0.27 11.14 7.40 1 1 .6 8 47.55 I- 0.27 0.13 0.39 365 367 1.37 6.28 4.10 9.84 0.27 9.02 0.82 0.55 0.27 1 0 .6 6 40.16 494 5.05 3.55 5.05 7.07 8.89 2.63 1.09 0 .2 0 0 .2 0 0.61 1.09 1 1 .1 1 1 0 .1 0 130 140 150 1.03 0.81 1.03 3.91 3.70 5.97 0 .2 1 0 .2 1 0 .2 1 0.62 0.61 13.37 14.34 10.93 12.35 17.90 26.34 32.73 1 2 0 378 486 1.05 9.16 8.64 6.54 0.52 0.41 0.61 4.97 12.76 0.26 0.52 10.47 1 1 0 1.23 2.36 2.91 5.67 3.93 3.06 0.31 0.26 0.31 1 2 .1 0 12.71 11.94 too 767 651 1.43 1.43 0.46 8.19 7.28 7.15 0.13 4.94 6.76 2 .8 6 1 .6 8 0.13 0.39 13.91 45.12 47.63 51.31 Species/Core Depth (on) G. menardii G. complex obliquiloculataP. S. S. dehiscens G. conglobatusG. dutertreiN. G. ruberG. G. sacculiferG. G. sdtulaG. G. crassiformisG. O. universaO. G. truncatG. (L) H. aequilaterialisH. ungulataG. fimbriataG. C. nitida C. G. G. truncat (R) Inflata G. falconensisG. G. bulloides G. calida G. G. digitataG. 0.26 Total with permission of the copyright owner. Further reproduction prohibited without permission. 474 1.04 1 .8 8 3.97 0.84 0.42 0.42 0.84 0 .2 1 425 500 520 3.53 6.26 5.65 4.59 0.24 4.24 0.94 1.67 0.71 0.63 1.14 480 0.38 0.57 470 1.96 2.94 6.275.23 4.00 3.42 3.55 4.00 6.54 6.27 5.23 2.47 0.330.33 0.95 0.98 0.33 0.33 0.65 0.19 71.57 74.14 75.53 73.70 1 .2 0 1 .0 0 2.79 0 .2 0 0.40 0 .2 0 0 .2 0 637 502 306 523 440 460 1.56 1.56 1.99 6.25 0.80 1.31 1.71 0.949.22 0.16 0.40 0.94 2.29 2.47 1.18 0.47 0.47 0.16 7.37 11.72 1.85 0.31 4.63 4.94 0.78 0.62 0.47 14.81 4.69 13.35 47.84 60.63 70.12 1 .6 8 4.49 0.19 3.74 0.37 335 534 324 1.19 5.67 2.39 2.06 1.23 5.07 5.42 4.18 3.74 6.48 0.30 0.19 11.34 21.87 12.04 34.03 36.64 468 360 380 400 420 1.06 5.30 5.37 3.81 3.81 0.420.64 0.90 0.19 0.93 2.75 0.85 0.85 4.87 5.37 4.30 4.32 13.35 40.68 494 340 1.42 3.24 2.23 0 . 2 0 0.40 3.39 6.28 14.57 14.83 24.18 14.39 11.94 345 2 .0 2 5.49 0.87 0.58 0.29 0.40 0.42 7.51 5.06 1 0 .1 2 530 1.69 1.31 1.16 3.75 1.45 4.05 0.38 0.58 4.50 0.56 0.29 0.81 0.56 0.29 0.19 0.38 0.75 4.32 12.72 17.64 46.15 35.26 49.39 . universa. 0 sdtulaG. G. crassiformisG. 2.97 C. nitida C. ungulataG. fimbriataG. digitataG. S. S. dehiscens Species/Core Depth (cm) 300 320 G. calida G. G. inflata G. N. N. dutertrei falconensisG. 7.50 aequilaterialisH. 21.39 4.88 G. conglobatusG. Total G. menardii G. complex sacculiferG. 6.19 G. bulloides G. G. G. truncat (R) G. truncat (I.) ruberG. P. P. obliquiloculata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 473 740 1.05 1 .6 8 2.52 2.73 5.87 5.03 0.42 0.63 0 .2 1 0 .2 1 0.84 13.63 10.90 53.67 1.06 2 .6 6 6.38 9.57 0.27 11.44 567 375 1.58 710 720 2.81 2.13 4.04 2.39 0.63 0.35 4.22 0.18 0.53 0.35 7.91 4.26 0.18 10.72 60.63 49.73 3.14 6 .0 2 4.97 2.81 1.06 0.52 0.52 8.64 3.51 8.51 515 380 680 700 1.16 1.83 1.93 1.83 7.32 6.94 6.28 4.05 3.403.85 0.70 2.36 2 .1 2 0.77 0.19 7.13 0.58 8.67 3.14 1.92 1.49 3.28 466 1.49 1.28 3.41 2.70 6.18 0.64 0.77 0 .2 1 60.77 48.55 57.33 172 660 665 1.73 5.78 2.89 2.31 3.47 0.58 4.05 6.40 0.589.25 1.28 6.18 8.67 5.33 4.05 1.28 0.58 2.13 54.91 533 1.31 2.62 0.19 0.58 0.19 0.58 0.19 363 1.38 5.06 620 640 1.38 2.43 1.93 3.56 1 .1 0 2.48 0.75 6.34 11.80 0.28 7.44 5.24 0.55 0.28 2 .2 0 11.57 57.02 53.37 1.21 1.73 0.35 0 .8 6 0.17 0.17 577 579 1.73 4.15 580 600 1.55 0.35 0.28 1.38 3.11 5.23 11.05 3.97 4.84 3.80 6.39 4.66 4.49 0.17 0.35 0.17 0 .8 6 0.17 4.32 7.43 0.35 72.71 63.04 326 1.53 0.61 0.35 0.55 2.25 0.31 1 1 .6 6 540 560 392 1.28 1.53 6.63 7.36 4.34 2.45 0.26 4.34 4.910.26 1.73 0.51 0.77 2.15 0.26 0.51 0.26 0.31 1.73 1.73 10.46 70.15 67.18 . unlversa. Species/Core Depth (cm) S. dehiscens G. sacculiferG. truncatG. (R) P. obllquiloculataP. N. dutertrelN. G. conglobatusG. ruberG. inflata G. crassiformisG. G. menardiiG. complex aequilaterlallsH. bulloides G. G. ungulataG. fimbriataG. 0 callda G. G. G. truncat (L) sdtulaG. Total C. nitida C. digltataG. G. falconensisG. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 418 1 .2 0 940 1.44 1.67 1 .2 0 0.24 0.24 6 .2 2 0.24 0.72 0.24 7.18 11.48 65.55 623 1 .1 2 2.56 2.40 0.48 0.32 0.64 0.80 0.80 4.00 2.39 11.84 60.48 392 920 930 3.32 3.57 7.36 2.81 0.26 0.26 6.89 0.51 11.99 7.20 63.27 1.11 1.11 910 1.11 5.85 4.59 3.90 3.34 2.55 0.84 477 359 0 .2 1 2.52 3.14 3.56 5.87 3.06 0 .2 1 9.22 12.81 0 .2 1 0.42 63.31 66.85 ------84 1.19 1.19 1.19 2.73 880 900 2.38 7.14 8.60 3.57 8.33 17.86 10.71 46.43 ------469 860 1.28 2.77 0 .2 1 2.77 6.18 11.30 12.58 57.36 ------1 oC O | ,'C o O 93 840 1.08 1.08 1.08 3.23 1.28 4.30 4.26 7.53 6.45 4.30 67.74 ------6 6 5.46 0.17 4.14 0.17 0.50 6.13 8 .1 1 0.33 9.93 13.58 47.52 ~ ~ L ------— ...... 339 604 1.77 1.32 1.08 1.47 0.50 1.18 M 7 800 820 1.47 1.18 1.77 0.59 18.58 57.52 — ------780 1.98 2 .2 2 7.65 12.98 0.25 0.74 0.25 0.25 0.50 48.15 ------760 1.82 1.73 492 405 1.62 1.48 5.875.47 21.73 4.44 2.83 6 .8 8 2 .0 2 0 .2 0 4.25 0.40 0.61 10.32 9.14 52.02 “ 5767“ . universa. Species/Core Depth (cm) S. S. dehiscens P. P. obliquiloculata N. N. dutertrei G. menardiiG. complex sacculiferG. truncatG. (R) inflata G. G. calida G. G. G. truncat (L) G. fimbriataG. G. bulloides G. Total G. G. conglobatus ruberG. 0 G. crassiformis sdtulaG. nitidaC. H. aequilaterialisH. G. ungulataG. G. digitataG. G. G. falconensis i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 233 140 1 1 .1 1 1 1 .1 1 1 1 .1 1 1 1 .1 1 2 2 .2 2 14 9 130 7.14 7.14 7.14 14.29 14.29 14.29 35.71 33.33 25 1 2 0 4.00 8 .0 0 32.00 2 0 .0 0 24.00 18 5.56 5.56 4.00 5.56 0.27 1 1 .1 1 8 .0 0 25 1 0 0 1 1 0 8 .0 0 4.00 8 .0 0 4.00 4.00 "1 90 283 2.47 7.07 4.95 7.77 4.00 94 1.06 0.35 5.32 12.72 5.32 3.53 4.00 5.56 4.26 3.89 4.26 7.07 5.56 2.13 0.3S 8.51 9.57 3.89 501 1 .2 0 0 .2 0 5.99 7.45 3.39 0.40 0 .2 0 0 .2 0 9.98 60 70 80 433 6 .0 0 3.23 8.31 5.99 0.46 11.78 10.78 11.32 41.34 42.12 48.94 45.94 64.00 55.56 386 5.18 6.99 3.46 6.79 2.59 6 .2 2 9.59 0.26 1 0 .1 0 40 50 537 1.30 3.11 3.46 3.17 0.19 8.94 0.74 0.26 0.56 8 .0 1 0.93 0.52 0.23 0.40 10.24 30 1.39 2.59 3.35 2.59 3.00 4.59 0 .2 0 4.98 0 .2 0 2.19 13.55 10.16 2 0 465 502 1.94 3.44 1.79 0.43 0 .2 2 0 .2 2 8.17 4.30 8.82 6.57 7.08 7.77 7.39 7.78 3.19 11.40 10.56 8.19 372 1 .8 8 1 .8 8 3.49 4.52 0.810.54 0.60 9.68 3.76 3.87 6.18 3.54 7.53 9.41 12.26 8.06 2.15 0.81 12.63 9.03 37.37 30.75 39.04 43.76 44.82 . . universa Species/Core Depth (cm) IG-21-26-10 G. digitataG. Total Counted 0.65 N. N. dutertrei P. P. obliquiloculata crassiformisG. sdtulaG. C. nitida C. H. aequilaterialisH. calida G. G. fimbriataG. G. menardii G. complex S. S. dehiscens G. truncat (L) ruberG. inflata G. 0 G. G. falconensls G. truncatG. (R) bulloldes G. G. ungutataG. G. sacculiferG. G. conglobatusG. I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. g 345 360 1.16 1.74 7.83 0.29 6.09 7.25 0.29 2.32 3.48 0.29 0.29 0.29 11.30 14.78 37.10 396 340 1.01 1.77 4.80 7.83 4.55 9.34 5.51 0.76 0.25 4.04 0.51 1 0 .1 0 46.46 320 593 1.69 1.18 1.85 3.88 5.23 2.19 7.08 0.34 4.55 0.17 9.11 8.59 0.17 54.81 300 510 7.84 2.75 3.73 0 .2 0 9.22 7.76 7.65 9.22 9.02 0.39 0 . 2 0 0 . 2 0 0.98 44.90 559 280 5.55 3.40 0.27 0.89 6.62 0.72 1.18 8.94 2.55 0.54 0.72 0.89 14.85 10.55 42.04 ------260 331 1.51 1.51 5.14 2.72 5.74 4.11 4.53 3.63 6.95 3.63 0.30 0.30 0.30 57.40 240 389 1.29 7.46 9.00 8.23 3.863.34 4.83 1.51 2.83 0.77 4.88 0.51 0.51 0.77 0.51 47.81 2 2 0 385 1.30 3.12 2.34 0.26 4.42 4.63 2.60 3.12 8.57 3.60 0.52 0.52 0.26 0.26 10.39 55.32 2 0 0 431 1 .8 6 5.57 7.01 3.71 5.80 3.02 9.05 0.70 0.23 0.23 13.46 12.06 10.67 32.95 180 444 5.63 6.76 5.63 0 .6 8 9.91 2.93 0.23 0.45 0.23 0.23 0.70 10.36 13.06 40.32 ------160 532 1.13 0.45 f.13 1.69 3.15 1.13 1.69 9.21 ‘ 0.38 9.77 0.38 11.09 43.42 r~ 15G 1 .8 8 4 2 5 1.18 5.88 4.47 0.71 0.94 0.24 14.12 10.82 9.40 12.94 9.59 42.35 T . 4 — — 14 150 7.14 7.14 3.06 7.14 ------_ 7 .1 4 _ - ~71.43~ ------. universa. Species/Core Depth (cm) S. S. dehiscens G. conglobatusG. P. P. obliquiloculata G. ruberG. 0 N. N. dutertrei G. menardiiG. complex sdtulaG. G. sacculiferG. truncatG. (R) G. truncat (L) Inflata G. G. aassiformisG. nitidaC. aequilaterialisH. ungulataG. G. falconensisG. G. fimbriataG. digitataG. G. bulloides G. calida G. Total Counted Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 580 639 1 .8 8 1.41 2.82 4.23 0.16 3.44 0.27 4.07 0.16 15.18 16.90 47.57 560 653 1.07 0.78 1.23 1.84 1.25 3.06 0.61 2.60 0.31 0.15 15.31 34.00 582 558 1.03 1.55 3.61 5.50 3.83 3.78 0.34 2.75 2.58 1.23 0.34 0.31 9.28 0.54 4.64 7.50 0,69 4.81 0.69 10.65 46.74 26.95 540 1.40 1.63 1.63 0.69 8.39 3.96 0.23 4.90 0.23 4.43 0.23 0.23 18.18 13.05 38.93 525 477 429 1.05 6.92 2.94 2.56 5.24 0 .2 1 0.63 4.19 0.63 2.73 4.19 0 .2 1 18.66 41.30 510 756 1.08 1.32 1.59 4.10 6.75 3.97 3.97 0.53 0.53 0.63 0.53 0.13 0.13 18.39 11.24 10.48 46.30 399 490 4.01 8.52 0.75 4.76 6.52 3.51 0.27 0.75 0.50 13.28 17.54 470 802 1.62 1.25 2.76 3.87 0 .1 2 2.87 2 .1 2 0.81 0.25 0.50 0 .1 2 0 .1 2 10.97 43.02 36.34 450 651 6.91 4.45 ’ 0.27 0.61 7.22 7.36 2 .0 0 5.84 1.75 3.38 0.31 0.15 0.61 0.92 12.44 24.19 430 5.47 1 .6 8 9.47 " 6.32 0.27 4.63 3.99 0.42 0.31 0 .2 1 lT779~ 50.95 50.69 "~ 4 7 S ~ ' 358 410 1.40 5.03 6.42 7.54 3.35 3.63 3.07 2.53 0.56 0.63 0.56 0.56 0.28 52.51 "4.47 ~ ~ 3.35 £T~ 2 . 400 8.79 9.05 0.54 8.29 2.76 3.02 2.23 2.51 0 0.50 8.54 5.03 3.16 10.55 ------~ 380 620 398 6.13 1.94 6.94 9.35 9.19 0.27 0.32 2.58 9.03 5.78 2.26 3.06 2.26 0.16 0.25 0.32 0.16 46.13 39.20 . . universa P. obliquiloculataP. S. dehiscens Species/Core Depth (cm) G. menardii G. complex G. conglobatusG. G. truncatG. (R) N. N. dutertrei G. fimbriata G. digitataG. G. sacculiferG. G. truncatG. (L) ruberG. sdtuiaG. C. nitida C. G. inflata G. bulloides G. calida G. H. aequilaterialisH. ungulataG. Total Counted G. crasslTormis G. G. G. falconensis 0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.38 5.50 2.29 6.42 8.72 0.46 0.92 0.46 0.46 800 820 1.59 5.24 2.75 7.292.73 4.59 2.51 1.38 3.64 2.73 1.38 0.81 0 .6 8 7.97 0.23 0.23 0.23 64.24 63.30 1.45 798 1.45 1 .6 6 5.80 3.93 0.41 0.41 0.41 10.35 563 483 439 218 1.60 5.38 1.42 3.11 1.07 5.18 3.55 0.54 7.64 3.93 0.18 0.36 542 760 780 1.48 1.11 3.14 0.27 8.67 17.94 4.240.37 5.150.55 7.25 2 .2 1 0.18 53.87 44.40 49.28 451 1.11 5.54 5.99 2 .8 8 2 .8 8 2 .6 6 2.44 7.20 7.28 0 .2 2 14.41 10.15 9.06 16.41 6.64 34.81 622 720 740 1.45 1.61 3.38 0.32 0.64 0.27 13.99 10.64 43.57 700 1.34 2.09 3.49 3.70 0.27 0.54 0.27 0.16 0.54 0.27 14.25 5.63 12.63 680 1 .6 8 1.49 4.03 1 .1 2 1 .1 2 3.35 3.76 2.05 1.08 2.794.84 3.76 4.84 3.22 11.09 2.23 0.19 0.19 0.19 0.54 299 537 372 2.34 9.50 4.03 9.00 3.68 1.49 0.81 2 .0 1 2 .0 1 6 .0 2 0.27 0.27 4.01 16.72 5.21 640 660 1.11 1.11 2.05 3.63 3.68 3.79 3.34 0.16 0.33 9.16 0.16 19.75 19.40 8.75 1.05 0.32 0.33 2.11 2.53 0.27 4.84 1.74 2.53 4.424.42 5.06 0.42 0.63 0.16 0.84 0.16 0.67 0.84 10.32 5.85 44.21 39.97 35.12 53.63 43.55 384 475 633 600 620 1.82 1.56 3.65 3.13 3.13 7.55 7.16 5.85 0.54 0.78 2.34 0.26 9.64 9.89 0.52 1 0 .6 8 50.26 1 1 3.91 3.58 Species/Core Depth (cm) S. S. dehiscens aequilaterialisH. P. obliquiloculataP. N. dutertreiN. G. flmbriataG. G. ruberG. inflata G. crassiformisG. sdtulaG. nitida C. G. falconensis bulloides G. Total Counted G. menardii G. complex G. conglobatusG. calida G. ungulataG. digitataG. 0.26 G. truncatG. (R) O. O. universa G. sacouliferG. G. G. truncat (L) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 3 Benthic foraminiferal percentage data for core-top study. 237 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 238 1.38 1.38 3.67 1.38 5.50 0.46 0.46 5.05 IG-41-13 5.12 7.85 0.34 1.38 0.34 0 .6 8 0 .6 8 0 .6 8 0 .6 8 1.90 1.78 4.78 4.27 4.44 4.270.36 0.47 13.310.71 0.34 5.96 0.24 0 .1 2 0.36 0.36 0.24 13.74 13.31 0.60 0.30 0.30 0.30 PC-5 IG-38-10 IG-38-18 1.83 0.59 0.61 3.30 0.31 0.31 6.42 21.92 0.92 0.31 18.65 18.02 38.86 0 .6 8 0.23 6.61 0.91 0.23 0.23 0.27 0.23 0.30 0.55 PC-1 PC-2 PC-3 - 8 0.29 0.34 BC 24.81 13.66 1.81 1.45 0.36 0.18 7.41 0.18 BC-7 39.42 64.15 20.49 27.33 1.65 2,16 0.55 0.41 3.95 0 .8 8 0.44 0.44 0.27 5.70 17.70 BC-30 .8 8 BC-4 Boiivina ordinariaBoiivina 0.82 0.90 Species/Sample No. Cassidulina crassaCassidulina neocarinata 0.41 0.18 Cassidulina subglobosaCassidulina 3.07 0.82 3.07 0.91 0.82 Boiivina minima Boiivina Boiivina barbataBoiivina Ammonia parkensonianaAmmonia Ammodiscus tenuis Boiivina paula Boiivina pusilla Boiivina subaerienesisBoiivina mexicana subsplnensisBoiivina Boiivina lowmani Boiivina translucensBoiivina aculeataBulimina alazaensisBulimina marginataBulimina mexicanaBulimina elegantissimaBuliminella Cassidulina carinata Cassidulinoidesmexicanus/tenuls Chilostommella oolinaCiblcdoides pachydermus bathyalis 3.98 0.18 0.31 Ammotium salsa fragile albatrossiBoiivina cf. lanceolataBoiivina Alveolophragmium sp. A Ammobaculites filiformis Ammodiscus incertus Ammodiscus sp. A Ammogloblgerina sp. A Adercotryma glomerata Alabaminella turgidus Bathysiphon spp. Ammovertellina sp. A Astacolus crepidulus Boiivina fragilis Boiivina Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 239 1.38 1.83 0.46 2.75 0.46 0.92 0.46 4.13 IG-41-13 3.41 0.46 0.34 0.34 0.46 0.34 1 .0 2 0.34 0 .6 8 IG-38-18 2.84 1.37 0.46 0 .1 2 0.24 0.34 2.29 0.24 0.34 0.24 0.24 0.47 1.50 2.40 0.90 0.95 0.30 0.59 1 .2 2 3.67 1 .2 2 0.31 1.53 2.40 0.83 0.61 0.30 0.47 0.31 PC-3 PC-5 IG-38-10 0.23 0.23 0.90 1.42 PC-2 3.55 2.73 0.5S 0.46 3.01 0.23 0.55 0.31 0.82 PC-1 -8 1.71 1.64 1.37 7.97 2.75 8 .2 1 0.34 0.34 0.29 0.34 1.45 2.17 0.18 0.18 0.18 0.18 0.36 BC-7 BC 1.65 0.41 0.54 2.19 0.44 0.24 0.44 1.81 2.19 0 .8 8 2.19 0.36 0.96 BC-3 BC-4 Gyroldna altiformis Gyroidinoides cf. roundimargo Giobobulimina affinisGiobobulimina orbicularis Gyroidina 0.27 Cibiddoides mundulus 0.82 Cibiddes wuellerstorfi 1.75 0.41 0.54 Glomospira gordaliasGlomospira 0.60 Glomosplra charoldes 5.26 8.23 Eggerella propinqua Epistominella exigua Eponideantlllarium Eponides sp. AFursenkoina paudloculataGaudryina sp. A 0.44 0.46 Cibiddoides cf. mollisCornuspira planorbis Cribostromoides sp. A Cribrostomoides nitidium Cribrostomoides sp. A Cribrostomoides subglobosumCribrostomoides wiesneriCydammina cancellata Eggerella bradyi 0.44 0.18 2.47 3.27 0.82 0.91 2.45 0.30 0.47 Species/Sample No. Cibiddes rugosa Cibiddes sp. B Cibiddes sp. C Cibiddes sp. D Epistominella vitrea Elphidium spp.Elphidium Gavelopnopsis translucens 0.36 0.34 Cibicides Cibicides corpulentus Cibiddes pachydermus sublittoralis Cibiddes robertsoniensis Cibiddes robustus Cibiddes umbonatus Cibiddes incrassatus Cibiddes bradyi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.92 0.46 4.13 4.59 0.92 0.46 IG-41-13 1 .0 2 0.34 1 .0 2 0.34 3.41 1.07 0.34 0.46 1.07 2.05 4.59 1.54 2.05 0 .1 2 1.54 1.07 0 .1 2 3.00 0.30 2 .1 0 0.30 0.59 0.30 2.40 3.00 0.47 0.60 PC-5 IG-38-10 IG-38-18 1.83 1 .2 2 0.31 1.53 0.31 2.70 0.36 0.46 0 .6 8 2.05 4.89 0.23 2.05 0.23 0.31 12.76 10.70 0.27 0.27 4.92 0.27 0.27 0,27 0.55 0.820.82 0.23 0.23 4.92 0.55 PC-1 PC-2 PC-3 -8 1.92 2.31 0.61 0.57 4.94 3.55 0.34 2.55 0.29 0 .6 8 BC 1.27 0.54 0.18 0.72 0.72 BC-7 2.06 0.41 0.72 0.41 7.41 0.54 5.58 3.01 2.510.41 6.42 0.41 0.54 BC-4 1.32 0.44 3.51 0.44 0.41 0.34 0.55 0.44 3.95 0.44 0.31 0 .8 8 BC-3 Neolenticulina peregrina Nodosaria flinti Nonlon depressulaNonlon Nonionella opima Nonionella Neocrosbyia glabra Neocrosbyia minuta Neolenticulina sp. A Nonionellina sp.Nonionellina B Nonionoidesgrateloupi Hormosina globuliferaHormosina Hormosina Hormosina spp. Haplophragmoides sp. B Species/Sample No. Karrerulina apicularisKarrerulina sp. A Multifideila 3.51 4.12 loanella tumidulus 2.19 13.17 1.63 14.70 Hyalantica balthica bradyi Karreilla sp.Nonionellina A Lagenamminaspp. Latacarinina pauperata 0.62 Hormosineila sp.Hormosineila A Hansenica sp. A Hanzawaia concentrica llanzawaia concentrica strattoni V. Haplophragmoidesbradyi Haplophragmoides sp. A Hoglundina elegans Loxostomum truncatum Melonis pompiloides Melonis Neoconorbina terquemi Martinottilla occidentalis Hormosinella Hormosinella sp. B Gyroidinoides Gyroidinoides sp. A Gyroidinoides polius Gyroidinoides Hansenica regularis Gyroidinoides spp.Gyroidinoides umbonatusGyroidinoides Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.38 1.38 2.75 0.46 0.46 0.92 0.92 6.42 IG-41-13 0.34 1 .0 2 0.34 1 .0 2 3.07 2.75 0 .6 8 IG-38-18 1.30 2.05 0.47 0 .1 2 1.54 1.37 0.240 .1 2 0.92 0 .1 2 0 .6 8 0 .1 2 0.83 0.36 0 .1 2 2.37 3.07 IG-38-10 1.50 1 .2 0 1 .2 0 2.40 0.90 1 .2 2 1.83 5.20 3.90 0.92 3.98 2.51 0.23 0.30 0 .6 8 PC-2 PC-3 PC-5 11.39 3.01 2.46 1.64 0.31 0.55 0.55 0.60 6.83 PC-1 -8 7.69 2 .8 8 2 .0 0 1.14 0.29 0.29 1.99 9.95 9.30 1.23 1.23 1.27 0.57 2.06 0.29 BC-4 BC-7 BC 19.34 5.26 1.75 0.54 0.57 0.61 2.63 3.95 2.16 1.64 0.44 1.75 1.32 0 .8 8 5.70 BC-3 6 umbonatus Saccammina shpaerica Sacchoriza elongata Saccammina cf. socialis Saccammina difflugiformis Sacchoriza friablis Rhumbler orEggerelloides sp. A 0.82 1.30 0.55 0.91 Planulina meditereanensisPlanulina Robertinoides bradyi Paumotua cf. terebre Pullenia sp. A bulloides Pullenia Reussella sp. A 0.44 algaformisRhizammina Rhizammina sp. A 0.29 Polystomammina nitldia Pseudocancris sp. A Pyrgo lucernulaPyrgo murrhyna 0.44 Pseudononion davatumQuadramorphina glabraReophax cf. dentaliniformis Reophax sp. A. 0.44 0.30 0.34 Psammosphaerasp. A Pseudonodosinella sp. A Pullenia subcarinataPullenia Pseudononion atlanticus Quadramorphlna sp. A Osangularla culter 0.41 Oridorsalis westi Osangularia rugosa Species/Sample No. Oridorsalis Oridorsalis sp. A Oridorsalls Oridorsalls sp. Oridorsalis Oridorsalis tener Oculosiphon linearis Nummoloculina Nummoloculina irregularis Nuttalides decorata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 218 1.83 1.83 1.83 2.75 2.75 0.46 11.01 1.37 1.02 3.41 1.02 0.68 0.34 0.34 IG-38-18 IG-41-13 844 293 0.36 0.24 2.05 0.95 0.47 0.71 0.47 0.36 IG-38-10 333 1.20 1.80 1.50 0.30 ------327 5.50 3.90 2.84 4.10 3.062.75 3.00 0.90 0.61 0.92 3.00 0.36 PC-3 PC-5 ------439 1.59 2.70 1.37 0.61 0.68 2.51 0.68 ------1.91 2.51 0.27 PC-1 PC-2 ------8 646 366 4.26 2.34 0.82 2.86 BC ------553 1.99 0.54 0.900.72 1.37 oTTe 0.90 7.38 3.28ia o. 1.14 0.36 1.14 1.09 0.36 BC-7 ------' ------3.70 0.82 BC-4 ------— ------228 243 1.32 4739 4.82 4.94 5.24 6.36 5.19 2.73 0.88 0.44 BC-3 ------Trochammina cf. inflata Total Picked Stainforthi complanta 0.44 Siphotrochammina squamata Textularia gramen bradyi Trifarina Spharoidina bulloides Spiroplectella cyclindroides peregrinaUvigerina peregrinaUvigerina parvula Valvulineria "A" Quinq, Fiss, Milio Misc. Trochammina globeriniformis auberianaUvigerina 1.75 hispido-costataUvigerina 0.27 Trochammina sp. A 0.44 Siphotextularia affinis Siphonina Siphonina bradyiana Indet. Rotalids 0.36 1.97 Trochamminajaponica Tretomphalls atlanticus Indet. Texularids Trochammina advena 0.44 opima Valvulineria Species/Sample No. sdilumbergeriSigmoilopsis Trochammina pauciloculata Valvulineria Valvulineria sp. A Sacchoriza ramosa 11.40 humilisValvulineria 0.82 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.97 1.57 1.57 2.76 0.39 2.36 0.39 13.78 IG-45-9 1.09 4.37 0.73 2.91 11.81 0.73 1 1 .1 1 IG-41-29 1.95 1.39 1.39 0.55 4.46 1.67 0.84 0.28 3.62 2.91 0.28 0.73 0.56 0.56 0.84 1 .2 0 0.40 2 .0 0 0.80 2 .0 0 2.80 0.40 0.56 0.55 1 1 .2 0 IG-41-26 IG-41-28 6 .6 8 0 .2 2 0 .2 2 0.45 0 .2 2 0 .2 2 0 .2 2 0.67 20.71 19.60 20.89 20.40 IG-41-24 ------2 .0 2 1.01 1.01 2 .0 2 0.34 0.67 0.34 0.89 0.34 0.34 ------7.20 0.77 0.26 0.34 0.89 2.31 7.71 45.12 1.78 0.77 0.26 0.51 12.85 7.74 IG-41-21 IG-41-23 ------____ 0.19 9.68 2.28 4.36 3.04 0.95 0.38 4.17 0.19 IG-41-19 ------___ ------1.27 1.91 5.10 0 .2 1 2.76 0 .2 1 0.64 ------Cibicdoldes pachydermus bathyalis 0.19 Buliminella elegantissimaBuliminella Cassidulinoidesmexicanus/tenuis Chilostommella oolina Cassidulina neocarinata subglobosaCassidulina 5.73 Bulimina alazaensisBulimina Cassidulina Cassidulina carinata 1.14 Astacolus crepidulus albatrossiBoiivina Species/Sample No.Ammodiscus sp. A IG-41-18 barbataBoiivina Ammotium salsa fragile ordinaria Boiivina Boiivina paula Boiivina pusillaBoiivina subaerienesisBoiivina mexicana 0.42 0.19 1.03 Bulimina marginatdBulimina 1.91 Cassidulina crassa Bulimina mexicanaBulimina 0.19 0.26 Ammoglobigerina sp. A Ammodiscus tenuis Ammonia Ammonia parkensoniana Ammovertellina sp. A Alveolophragmium sp. A Bathyslphon spp. Ammodiscus incertus cf. lanceotataBoiivina fragllis Boiivina lowmani Boiivina Boiivina minima Boiivina translucensBoiivina aculeataBulimina 6.58 0.38 3.23 2.23 Boiivina subspinensisBoiivina Alabaminella Alabaminella turgidus Ammobaculites filiformis Adercotryma glomerata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.54 IG-45-9 2.73 0.91 0.18 2.37 0.55 5.12 0.36 0.18 0.55 0.36 2.37 0.73 0.79 0.36 1.11 1.39 0.28 1.39 0.28 0.28 0.28 IG-41-28 IG-41-29 1 .2 0 4.40 2.51 0.80 0.80 1.60 0.40 0.56 0.40 1.11 1.34 1.39 0.89 0 .2 2 1.11 0 .2 2 0 .2 2 0 .2 2 0 .2 2 IG-41-24 IG-41-26 0.34 0.67 IG-41-23 1.29 2.31 2.23 0.19 0.51 1.71 1.03 0.45 0.76 0.26 1.35 0.38 0.19 0.57 0.95 0.38 IG-41-19 IG-41-21 1.49 1.33 1.54 1.49 0.64 1.06 0 .2 1 2.76 0 .2 1 0.42 Gyroidina orbicularisGyroidina Gyroidinoides cf. roundimargo 1.60 Glomospira charoidesGlomospira gordalias altiformisGyroidina 0.38 1.54 Eponides sp. A Species/Sample No. IG-41-18 Eponide antillarium Fursenkoina paudloculata Gaudryina sp. A Gavelopnopsis translucens Globobulimlna affinis Epistominella vitrea Cribrostomoides nitidium Cribrostomoides sp. A Cribrostomoideswiesneri Eggerella bradyi 0.42 0.19 Eggerella propinqua spp. Elphidium Epistominella exigua 3.82 3.98 Cibiddes sp. B Cibiddes miellerstorfi Cibiddoides cf. mollis Cribrostomoides subglobosum Cyclammina cancellata Cibiddes bradyi Cibiddes corpuientus Cibiddes incrassatus Cibiddes robertsoniensis Cibiddes robustus Cibiddes rugosa Cibiddes sp. C Cibiddes sp. D Cibiddesumbonatus Cibiddoides mundulus Cornusplra planoibis Cribostromoidessp. A 0.19 Cibiddespachydermus subliuoralis Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 245 6.30 0.79 1.57 4.33 IG-45-9 1.28 0.36 1.82 1.46 0.55 0.73 0.36 0.36 0.91 IG-41-29 1.11 1.39 1.1 1 2.23 0.36 0.84 0.28 0.91 0.56 2.23 0.84 0.28 IG-41-28 1 .2 0 0.80 0.40 0.80 0.40 0.80 2 .0 0 4.80 1.11 0 .2 2 0 .2 2 0 .2 2 0 .2 2 0 .2 2 0.45 4.01 2.40 0.67 2 .0 0 0 .2 2 0.45 0.89 0.34 | 1.39 2 .0 2 2.83 1.54 1.35 0.51 2.83 0.38 1.34 1.71 1.54 0.3B IG-41-19 IG-41-21 1G-41-23 IG-41-24 1G-41-26 1.91 2.09 0.51 1.34 1.27 1.14 1.03 0.42 1.33 1.29 1.35 0.42 Nonionoides grateloupi Nonionella Nonionella opima sp.Nonionellina A sp.Nonionellina B 0.34 Karrellla bradyi Karrellla apicularisKarrerulina Lagenammina spp. Nodosaria flinti 1.14 Nonion depressula Neoconorbina terquemi Neocrosbyia mlnuta 0.85 Loxostomum truncatumNeolenticulina peregrinaNeolenticulina sp. A 0.51 0.26 loanelia loanelia tumidulus Latacarinina pauperata Neocrosbyia glabra Multi fidella sp. fidella A Multi 0.34 Hanzawaia concentrica strattoni V. Martinottilla ocddentalis pompiloides Melonis Haplophragmoides sp. A Hormosina globulifera Hormosina spp. Hormosinella sp. A Hormosinella sp. B Hyalantica balthica Species/Sample No. IG-41-18 Hansenica regularis 1.70 Hoglundina elegans Hansenica sp. A Hanzawala concentrica Haplophragmoides bradyi Haplophragmoides sp. B Gyroidinoides sp. A umbonatusGyroidinoides Gyroidinoides polius Gyroidinoides Gyroidinoides spp. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 246 1.57 0.39 0.39 8.27 0.79 13.78 IG-45-9 2.19 0.18 0.91 0.91 4.37 7.65 14.57 IG-41-29 1.67 1.39 1.67 0.36 3.62 0.84 5.57 0.28 0.56 3.10 0.28 0.28 0.28 2.79 0.84 0.84 10.31 1.60 1.60 1.60 0.28 2 .0 0 2 .0 0 0.40 0.40 IG-41-26 IG-41-28 1.11 1.11 0 .2 2 0.67 0.89 0 .2 2 0.67 0.89 0 .2 2 0.89 0.67 IG-41-24 1.01 0.34 4.71 0.34 7.74 16.26 14.40 0.26 2.83 0.51 12.85 IG-41-21 IG-41-23 3.23 2.85 1.54 0.34 1.56 0.19 0.51 2.47 9.77 11.45 0.76 0.51 30.17 2 .1 2 0.2 1 0 .2 1 0 .2 1 0 .2 1 0.G4 0.19 4.37 39.92 16-41-18 IG-41-19 Saccammina shpaerlca Sacchoriza friabiis Paumotua cf. terebre Sacchoriza elongata Saccammina diffiugiformis Saccammina cf. socialis Species/Sample No. Planulina Planulina meditereanensis Rhizammina sp. ARobertinoides bradyi 0.73 Osanguiaria rugosa Oridorsalis umbonatus Oridorsaliswesti Osangularia culter 4.25 Pullenia Pullenia sp. A 0.42 Polystomammina nitidia Pseudononion atlanticus Pseudononion davatum Pullenia Pullenia bulloides Pyrgo murrhyna Reophax cf. dentaliniformis Reophax sp. A. Reussella sp. ARhizammina algaformis Rhumbler orEggerelloides sp. A 0.19 Oculosiphon linearis Oridorsalis sp. A Oridorsalis sp. B Psammosphaera sp. A Pseudocancris sp. A Pullenia subcarinataPullenia Pyrgo lucernula Quadramorphina glabraQuadramorphina sp. A 0.19 Nummoloculina irregularis Pseudonodosinelta sp. A Oridorsalis tener Nuttalides decorata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 247 254 0.39 0.39 549 1.64 1.28 0.39 1.28 0.36 0.55 0.18 0.18 0.18 0.55 0.36 IG-41-29 IG-45-9 1.11 1.11 2.23 4.55 1.39 1.09 0.28 0.28 1 .2 0 0.40 0.80 0.40 0.80 1.11 3.12 0.56 2.23 0.280.67 0.55 0 .2 2 0.89 0.45 IG-41-24 IG-41-26 IG-41-28 297 449 250 359 1 .6 8 0.34 0.34 0.28 ------1.29 0.34 0.89 3.08 0.51 0.26 0.51 ------1.33 0.51 1.33 0.34 0.89 0.80 0.38 0.57 1.29 1.78 ------IG-41-19 IG-41-21 IG-41-23 ~ 0 3 8 ~ " ------1 1.49 2.47 2.57 2.36 4.45 6.40 1.70 0.85 0 .2 1 0 .2 1 0.640.42 0.38 0.38 0 .2 1 O.Z Uvigerina peregrinaUvigerina Trochammina globerinifotmis 0.95 Uvigerina peregrinaUvigerina parvula Total Picked 471 527 389 Indet. Rotalids Quinq, Fiss, Milio Misc. Spharoidina bulloides TrochamminaJaponlca Trochammina pauciloculata sp.Valvulineria AIndet. Texularids 1.71 1.54 Trochammina cf. inflata Siphotrochammina squamata Stainforthi complanta Tretomphalis atlanticus opima Valvulineria Trochammina advena Trochammina sp. A auberianaUvigerina Species/Sample No.Siphotextularia affinis IG-41-18 Valvulineria Valvulineria "A" humilis Valvulineria Splroplectella cyclindroides Uvigerina hlspldo-costata Sacchoriza ramosa Siphonina bradyiana Textularia gramen Sigmoilopsis schlumbergeriSigmoilopsis Trifarina Trifarina bradyi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.03 9.04 0.26 0.52 3.10 0.52 1.29 13.70 IG-46-12 ___ 1.24 1.24 0.78 2.48 2.17 0.78 0.62 0.93 0.31 0.31 17.65 IG-46-11 2.50 3.33 7.50 0.83 0.83 1 .0 2 1 .0 2 1 .0 2 0 .2 0 0 .2 0 0 .2 0 24.13 2.50 IG-46-8 IG-46-9 1.57 1.57 3.92 2.61 0.26 0.52 0.52 0.61 0.26 12.53 IG-46-7 ------1.32 0.26 2.31 8.09 0.83 3.80 0.17 0.17 3.47Boiivina lowmani 3.42 2.87 0.61 3.47Boiivina 0.33 0.33 0.50 3.42 5.04 2.34 0.54 0.36 14.39 17.02 IG-45-14 IG-45-15 Cibicdoides pachydermus bathyalis Cassidulinoidesmexicanus/tenuls 0.18 Cassidulina subglobosaChilostommella oolina 8.81 6.78 7.05 5.73 4.17 6.81 Boiivina albatrossi Boiivina Buliminella elegantissimaBuliminella Cassidulina crassaCassidulina neocarinata 1.43 0.26 Bathysiphon spp. Species/Sample No. Bulimina alazaensisBulimina Boiivina puslllaBoiivina marginataBulimina mexicana Bulimina Cassidulina carinata 0.18 1.62 Ammovertellina sp. A Astacolus crepidulus Boiivina barbataBoiivina cf. lanceolataBoiivina ffagilis Boiivina Boiivina subaerienesisBoiivina mexicana subspinensisBoiivina translucensBoiivina aculeataBulimina 0.26 Boiivina minima Boiivina ordinariaBoiivina paula Boiivina 0.18 Ammodiscus sp. A Ammotium salsa fragile Ammodiscus tenuis Ammoglobigerina sp. A Alveolophragmium sp. A Alabamlnella Alabamlnella turgidus Ammonia parfcensoniana Ammobaculites fill for mis for Ammobaculites fill Ammodiscus incertus Adercotryma glomerata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.81 1.03 0.26 0.26 IG-46-12 1.55 1.24 0.52 0.310.93 0.78 0.93 0.26 0.93 0.31 0.31 IG-46-11 6.67 2.48 2.33 14.17 0.52 0 .2 0 0.41 0 .2 0 14.11 2.35 0.78 1.57 2.35 0.78 0.26 0.31 0.26 IG-46-7 IG-46-8 IG-46-9 1.16 0.17 0.52 0.62 2.64 0.83 0.33 0.26 0.82 0.17 0.83 0.17 1.80 2.98 2.35 1.98 3.31 3.92 0.41 1.08 1.65 0.36 0.36 IG-45-14 IG-45-1 5 Glomospira gordaliasGlomospira altiformisGyroidina orbicularisGyroidina Cibiddoides cf. mollis Cornuspira planorbis Eponides sp. A Gaudryina sp. A Gavelopnopsis translucens affinis Globobulimina 1.26 Species/Sample No. Epistominella vitrea Gyroidinoides cf. roundimargo Elphidlum spp. Elphidlum Cibiddoides mundulusCribostromoides sp. A Cribrostomoides nitidium Cribrostomoidessp. A Cribrostomoides wiesneri 0.18 Eggerella propinqua Eponide antillarium Fursenkoina paudloculata Cibiddes umbonatus Cibicides wuellerstorfi 1.08 Cibiddes sp. B Eggerella bradyi Epistominella exigua Cribrostomoides subglobosum Glomospira charoides 1.44 1.31 Cibiddesincrassatus Cibiddes robertsoniensis Cibiddes mgosaCibiddes sp. C Cydammina cancellata 0.26 0.33 0.26 Cibiddes pachydermus sublittoralls Cibiddes robustus Cibiddessp. 0 Cibiddes bradyi Cibiddes corpulentus Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0 . 2 6 1 . 2 9 5 . 1 7 2 . 8 4 0 . 2 6 I G - 4 6 - 1 2 1 . 2 4 0 . 6 2 1 . 2 9 2 . 1 7 2 . 3 3 1 . 5 5 0 . 7 8 0 . 6 2 1 . 2 9 0 .3 1 0 .3 1 IG - 4 6 -1 1 0 . 8 3 5 . 5 7 I G - 4 6 - 9 1 .2 3 0 .2 0 0 .4 1 0 .3 1 1 . 4 3 0 .2 0 0 .2 0 2 2 . 0 9 2 . 5 8 I G - 4 6 - 8 0 . 2 6 I G - 4 6 - 7 H 1 . 1 6 ^ 0 . 5 2 0 .6 6 2 .8 1 2 . 3 5 0.17 0.83 0.31 0 . 9 9 2 . 0 9 0 . 1 7 0 . 2 6 1 . 8 0 1.44 0.83 0.26 0 . 5 4 1.44 0.50 0.26 0 . 1 8 0 . 3 6 1 .5 7 0 . 9 0 0 . 7 2 0 . 7 2 0.90 1.98 0.78 IG-45-14 IG-45-15 Nonionellina sp. Nonionellina A sp. Nonionellina B Nonionoides grateloupi Nonionella opima Nonionella Nodosaria flinti depressulaNonion Neolenticulina sp. A Neolenticulina peregrina Hormosina globuliferaHormosina Hormosina spp. Hoglundina elegansHoglundina Neocrosbyia minuta Martinottilla occidentalis Kaneruiina apicularis Loxostomum truncatum Hormosinella sp.Hormosinella A Hormosineila sp. B Haplophragmoides sp. A Haplophragmoidessp. B Species/Sample No. Melonis pompiloides Melonis sp. A Multifidella Neoconorbina terquemi Neocrosbyia glabra Karreilla bradyi Karreilla Hyalantica balthica loanella tumidulus Lagenammina spp. Hanzawaia concentrica Hanzawaia concentrica V. strattoni Haplophragmoidesbradyi Gyroidinoides umbonatusGyroidinoides Latacarinina pauperata Hansenica sp. A Hansenica regularis Gyroidinoides Gyroidinoides sp. A Gyroidinoides polius Gyroidinoides Gyroidinoides spp.Gyroidinoides Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.29 1.03 3.10 0.78 3.36 0.78 0.52 16.80 IG-46-12 1.24 0.31 2.79 0.62 0.31 0 .9 3 0 .7 8 0.62 0.31 IG-46-11 0.83 0.93 5.00 2.50 0.83 IG-46-9 IG-46-8 0.78 0.26 0.78 0.26 7.57 13.32 4.91 1.67 17.96 IG-46-7 1.16 0.33 0.26 0.31 0 .33 23.80 IG-45-1 5 0.54 0.41 1.29 0.18 2.70 3.97 1.31 0.18 3.GO 2.64 3.390.5 4 34.17 0 .5 2 Saccammina cf. socialis Saccammina shpaerica Sacchoriza elongata 0.93 Sacchoriza friablis 0.54 0.52 Pseudonodosinella sp. A Pseudononion atlanticus ReusSella sp.ReusSella A Rhumbler orEggerelloides sp. A Robertinoides bradyi Saccammina diffluglformis Species/Sample No. IG-45-14 Polystomammina nitidia Psammosphaera sp. APseudocancrissp. A Pseudononion davatum 0.54 Nummoloculina Nummoloculina irregularis Nuttalides decorata 13.85 Reophax sp. A. Rhizammina algaformis Rhizammina sp. A Osangularia rugosa Planulina meditereanensis 0.90 Oculosiphon linearis Oridorsalis sp. B Paumotua cf. terebre Pullenia sp. 1.08A bulloidesPullenia 0.36 Quadramorphina sp. A Reophax cf. dentaliniformis Oridorsaliswestl Osangularia culter Oridorsalis sp. A Oridorsalis tener Pullenia subcarinataPullenia Pyrgo lucemula Pyrgo murrtiyna Quadramorphina glabra 0.62 Oridorsalis umbonatus 1.08 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 252 1.03 0.26 0.52 0.26 323 387 1.24 1.29 1.24 0.93 0.52 0.93 8.05 6.98 0.62 1.29 0.93 0.62 0.31 0.62 0.26 IG-46-11 IG-46-12 1 2 0 1.6 7 1.6 IG-46-9 489 1.43 2.45 1.67 3.07 IG-46-8 383 1.31 1.04 0.52 0.82 0.26 0.26 IG-46-7 2.98 4.70 0.50 0 .6 6 0.17 0.26 556 ' 605 6 .1 2 0.72 2 .8 8 0.36 0.17 0.72 0.50 0.54 0.17 0.54 0.18 0.78 IG-45-14 IG-45-15 Trochammina globeriniformis 1.08 Siphotrochammina squamata Spiroplectella cyclindroides Textularia gramen Stain fort hi hi complantafort Stain Species/Sample No. Spharoidina bulloides 0.99 Indet. Texularids Siphonina bradyianaSiphonina Siphotextularia affinisTretomphalis atlanticus bradyi Trifarina 0.18 peregrinaUvigerina 0.18 0.50 Uvigerina peregrinaUvigerina parvula 0.90 0.26 Sacchoriza ramosa Total Picked Indet. Rotalids Quinq, Fiss, Milio Misc. 0.54 0.50 2.09 0.61 5.83 Trochammina advena Trochammina cf. inflata Trochammina Japonica Trochammina pauciloculata Trochammina sp. A opimaValvulineria sp.Valvulineria A 1.49 0.61 Valvulineria "A" Valvulineria humilis Valvulineria Sigmoilopsis schlumbergeriSigmoilopsis Uvigerina hispido-costataUvigerina Uvigerina auberianaUvigerina Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 4 Benthic foraminiferal percentage data for downcore study. 253 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 254 0 CM U1 CO o i q CM 1 CM o i CM* O CM CM d CL 0 cn r T CO CD CO 0 1 0 1 1 CO r r d (SI CO o U CM CM CL 0 CM CO r r CD 1/1 CM f- 1 i n CM CD* o *“ V CM CO 0 . 0 CM CM tT CO 1 CD CO CO 0 1 CM M* 0 0 O o o o (J CO C- CD i n o CO r**. CO i n CM CO* o o CO i n P C 2 - 1 0 0 1 m rT CM M* CM CM q 0 0 CM Is*. CM CM r r s i O o O o m P C 2 - 9 0 1 ! 0 0 r r CD CO CD i 01 N. o ! CM* d 0 1 i n o P C 2 - 6 0 1 i 0 0 CD CM »—* i CM C l | i CO 0 1 C l j CO* d o oo* rT 1 P C 2 - S 0 1 ! i ! o N. r r 0 1 N- CM 0 0 i / i d d O r r P C 2 - 4 0 1 i 1 o CO 0 1 cn N. N- r**- CM c d co CJ CM CL i 1 M* CM CO O q CM* d P C 2 - 2 0 | 1 I r r o i N. CO M* m Is- co* ! o c n o i P C 2 - 1 5 | O) 3 .q “a> n JZ o 3 O) c V § in re £ O) 01 & ■ o in CJ o > Q. k . •s. a c X a ■D re c .Q 3 c CO in 3 re CO • o s O l £ o O) .O Q. <0 m N 03 s re e- 3 re O) V) ? 3 ’(ft .Q c 8 - U a in a O u ■5 ■5 Q. CL E D3 o **o XI CO re re E Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Q. o PM in CL a CM 0 i 1 1 Sample | PC2-20 | PC2-30 | PC2-40 | PC2-50 | PC2-60 | PC2-90 | PC2-100 I 1 I PC2-120 I PC2-130 1 I PC2-140 1 CJ .Q 3 O) 8 in 19'Z 1 CO cn s CM CM CO CM CO rT jCbwue | 26.64 | 5.06 1 0.64 1 0.64 1 3.07 1 | 2.69 1 3.69 jChilool | 1 I 1 ! i i |Cominvol | i ' i |Cribr spp. ] O CM m [Cushbrow | 0.39 | 0.32 | 0.22 | | | Discam spp ] 0.25 | 9 | S90 rv. 19'0 1 o rr ci o CO o CD •«** CO fs. r-*. *— in d |Eggbrad | 0.73 | 2.74 | 1 0.85 1 o \ c *— | 0.82 (Elphspp | 1 0.16 0.29 zso 1 m CO [ O (Epiex | 0.31 I UJ Q. > ‘D CO CO rr o CM in o CD d O CD O ci d m O Oi m o o CO CM CO 0.64 | 0.22 | I 0.92 I CM d |6 avtrans | o CM CM |Globaff | 0.29 | (Globova | 0 6 1 fs. __ rCD rr d CO oi in e? 5 o CD o CM o E CO w 2.95 | (Glomgord | 0 9E | 0.32 | CM o a in CD in CO rr o CM d CD o' a 4.28 | CM CM f— o CM (Gumbo ] 1 1.17 | [ 0.46 | a JQ ! O a [ 0.29 1 a ■2 >* £ CO I I I 1 I o jGyroid spp. | CM jGyroidneo | jHanzconc | 0.25 | X CO C 07 V) O) 07 >* X d fr* CO CM o o rT O 0 O) 07 0 > ) 2'1 I 21'01 |! 0.32 | in GO isl CO 01 CO CD CO m* CO rr CM CO CO o o rr |ltum | | 14.97 | 1 14.16 o CO rr in q d CM rr N- CM (Karapic | d r— CD CM m [Karbrad | o o |Latpaup | CM 01 o CM m o CO |l_ent spp. ] o CD [Loxtrun |M artschk 60 | 16'0 GO N. d f*. CO o |Mbar1 | 1.82 | 0.87 r 0.64 1 0.64 I 1 0.32 1 tS | It'S S‘ | S8‘0 | a5 7 S0 I S60 1| ' 2 in 01 r rr CM a o E a | 2.33 | 0.87 1 1 0.91 | 0.31 1.64 6Z'9l 01 | 2001 | OZ'6 'l 1 i'll S 1 1 1 9 6 1 1-72 | 'll 68 | i S 00 | CO cd CO CO (Ndec I| 13.51 | 10.47 | 9.83 | I 11.22 I 1 rr (Neocmin o 256 l 0 I ‘0 I l* I lfr‘0 I CO CO CM CM 1.64 4.10 2.46 2.46 I PC2-140 1 __ 900 0 9 I 1 ci CD CM in CO 1.72 o 2.29 0.57 1 O o PC2-130 1 1 1 2.01 | | 0.29 | I 0.86 | 0.29 I | CD CD to CO CO 01 in d 2.05 0.16 0.32 o o o o PC2-120 1 | | I 0.63 0.95 | I CM oi CO CO CO CO 1.53 1.53 | o 0.61 o 0.61 | o d o PC2-110 1 | | 1.53 tt I t-tz I | 0.92 ] | 0.31 o o in CM CM CM 00 1.07 1.07 | CM 1.07 | U o o 6 O CL | | 0.64 Tj" 1 CO N. 0.22 0.22 | 0.22 | 0.22 0.22 1 o 0.22 | PC2-90 PC2-90 | l CO TT 1.37 1.37 | d PC2-60 PC2-60 | i [ 1.37 | 0.46 | 0.46 (0 O! ! Cl i m 0.96 0.96 I o 0.32 | PC2-50 PC2-50 | i 1 | 0.32 0 Z 6 p*. !m CO 0.58 0.58 | 0.29 0.29 | o PC2-40 PC2-40 | | | 2.62 GO p-* 1.17 0.39 0.39 | 0.39 | o PC2-30 PC2-30 | I | 9E‘0 ! 0 I | I60" CO I 60' (0 N. CO 1.09 1.09 | 0.73 0.73 | 0.36 0.36 | o o PC2-20 PC2-20 | 860 6 8 f | 1.09 I M* CO CM rs. ! CM 01 0.25 0.25 | cm’ 0.49 1 O i PC2-1 5 PC2-1 5 | i d CL 3 ■o in > COL. N Sample Sample j CL a 3 03 CL V) CL.Q £ *o 3 •<3 E 3 c/> O XIw CO c VI a> C (A *3 CO 3 E Ui O 03 3 8 x: a -e .Q s- Q> CO Q. Q_ a. O' O' QC * C/3 m £ 0£ jSpirocycl IStanfsp O. |Pseunonclav IPsubcarln | I jSigmschl ISiphaff | Istanfcom |Trocglob O IPryluc IPseunonatl jPsubsph | | | jSaccsphar |Sigmoten | | IQIamrk IQIamrk IQspp | |Rosal spp. | |Neoienpere |Neoienpere | jOsangcul jOsangcul (Osanrug (Pauter | ] | jNeoterq jNeoterq (Nonopim |Numin | | | |Oridtene |Oridtene | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 5 7 I I PC2-140 1 | 2.05 | 1 239 | PC2-130 PC2-130 1 | | 4.30 | 1 334 cn CO PC2-120 PC2-120 1 E' ] EB'S I | 3.16 | i r— co o* PC2-110 PC2-110 1 r r 0.92 I I 303 ] 1 CO CO o’ I I PC2-100 1 r 0.43 | 3.63 | 1 PC2-90 1 1 | 3.05 | 1 445 | 1 CO 00 00* | | PC2-60 | | 2.28 I 2.74 | I 203 ] ! I 0* 00 i ! | 1 ; 1 1 PC2-50 1 I 2.87 | 1 301 ] o j i ! i i CO ? : r t CD* a ! ! i i I 326 | i j i 1.95 1.95 PC2-30 l | 5.06 I 1 234 | OJ 00 PC2-20 I I 0.36 | 2.92 | 1 259 | LD ICO oo | rr O* ioo PC2-15 i I I 3.19 | | 383 | 2 CTJ o d c r Q. (A w *§ *> C 3 |lndet. Miliolid llndet. Textular | Lag/Fis |Misc. spp | IValspp IValspp 1 (Valmex (Valmex | |Total I | | ITrocfiadv Sample (Uviaub |UvigH-C |Uvigper | |Val sp 202 | | | | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced cn o 0 OZ-lOd 1 Q- U CNJ Sample PC2-1S5 PC2-180 | PCZ-200 | PC2-215 | PC2-260 | 1 PC2-320 1 PC2-380 1 PCI-10 1 PCI-40 1 PCI-60 1 |Aderglom | 1.09 o’ hw (Ampark | 0.32 | 0.38 __ 1 I i ! i ! 0.26 i |Amphisgib I i i i (Anglocfbel | 1 ! i ! Anomlglob I \rf 19 i ico jin 06 06 21 N-* o 1 CNJ V CO ID CNJ cn Cl o' o O CNJ n i CNJ CNJ CO ID CNJ Aturg ; 8 .6 8 7.91 |Balb | o’ CNJ i ! j 1 , I t i 0.25 | 0.26 i |Bbarb | I CD .fc e r O) i i CO V) O . a d |o SOZ | CM u r z ci P^ cn cn |Bolow | 8.97 \ 13.18 | 18.39 1 14.11 I 7.65 CM 10.44 0 2 9 9S0 S 9 I I 4.67 CD 1 ■S o c (Bpaula | i j jBpusi) 1 q ID 1 | 0.26 O* m (Bsubar | CM N. o CM m o' CM o' M* o' CO (Bsubspin I CO CM i 1 |Btrans | 0.83 | |Bul spp | (Bulacul | ! | 1 |Bulalz 1 0.25 1 i i j | I 1 ! |Bulimin eleg ! | 1 1-29 I I [Bulmarg | (Bulmex | |Bulspic | | SZ0 I 0.47 I O in re re b jCasscurv | 0.25 I o’ cn o | (Cassidtenu i 1 |Cassneo | I 0.25 0.26 o’ CM in r- o tn cn O CD o’ o cn q CO ci CM U A tj* cn cn q CO •*r CM* Cl in CM CM re s 1 2.70 U A in 1 0.47 o ID 1 n c q GO CM N. cn o' CO |Cbbrad |_ 0.23 | 1.24 ___ 1.15 0.40 | 2.1 1 i I | 2.79 V A a o e- O JO b re in c I \ o' A o' r-* Cl cn U "O rr o* E 3 c o JO A A £ . a O re i 1 i I 1 t j 1 U A -5 A . Q in 3 U JQ A O 6.27 2.61 0.52 4.18 0.52 0.52 15.14 ------2.79 2.87 1 .8 6 0.47 2.79 0.47 6.51 0.52 6.98 3.72 0.47 2.33 0.26 13.49 PCI-40 PC1-60 ------1.47 1.57 4.18 1.97 0.25 5.65 0.25 0.25 0.26 0.49 0.25 1.37 3.28 2.70 0.27 0.55 4.92 7.62 1.40 4.18 4.64 3.01 0.55 2.73 4.18 0.27 0.25 2.46 1.47 0.55 0.49 0.27 0.74 10.38 13.02 16.28 PCI-10 PC1-20 “ 1.64 "" ~ T.09 ------053" “ 1.05 2.63 PC2-380 ------0.56 0.56 1.05 0.56 0.56 6756“ “ 2779 10.61 10.53 0.56 PC2-320 ------""'7 .6 8 ------0 4 0 2.42 13.31 ------__ — 0 7 7 1.92 1.61 “ 14.94 __ ------___ ------___ 0.31 2.45 0 3 l _ ------2745 11 .0 1 ------PC2-215 PC2-260 PC2-300 ------0.64 0.328 .6 8 0.92 0.38 0.32 0.32 0.32 0.38 2.89 0.96 16.08 ------__ ___ ------1.24 7.88 0.41 1.24 4.82 3.45 1 .6 6 5.39 0.41 0 4 1 31.12 PC2-180 PC2-200 ------___ >3 ------1.84“ 0.23 0.23 0.23 0.23 10.57 12.18 9.13 14.47 15.60 I 7.28 8.06 8.38 9.47 .?J PC2-155 ------Sample Mpomp Ndec Neocmin Mbarl Karbrad Lent spp. 0.41 Latpaup Loxtrun Martschk Gyorblc Iturn Karapic 0.46 Gyrmard Hanzconc Gyroid spp. Gyroid Haynesgerm Gpoli Eggbrad 1.15 Hoegele 1.09 1.23 Cushbrow Dlscam spp Gumbo Gyroidneo Cribr spp. Cribr Elphspp Eplex Epvit Galti Gavtrans ft Globa ova Glob Glomchar 0.23 Chilool Glomgord Corninvo! Cbwue Cbrugos I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0 to fs. CM CO CO 1 CO m CM o fs. 1 . 5 7 0 . 2 6 o ’ o 5 0 . 2 6 CNJ o ’ a , so' : '9 o s i I 0 . 5 2 0 V 1 0 . 9 3 G 3 . 2 6 0 . 9 3 o ’ CL [ [ 0 .9 3 1 I 0 . 9 3 0 CM m i n CO 1 CM fs. CM CM 1 . 2 3 0 . 7 4 0 .4 9 I U 0 .2 5 1 o* o ' o* CL , , | 4 -42 SS'O I I | 0 .4 9 | 1 0 . 4 9 91 fS- ps. fs. fs. fs. 9 ) fs. CM fs- CM CM CM CM CM o CM CO co CM o ’ o ’ O* o* o ' r*“ d O* P C I - 1 0 1 1> 1 I ' | 5 8 0 .5 12> 5 1 1 1 I 'l O S 1 | 1 . 3 7 1 0 . 8 2 CO CO i n fs. c i CO in in o fs. q V o i n CO P C 2 - 3 8 0 1 L . 7-37 I CO 9 ) CM m o CO m N. CO CM 2 .2 3 | 2 .7 9 | o CM 0 .5 6 | CO to CM* P C 2 - 3 2 0 1 L8‘0 8 L I 'O B I | r 2 1 .2 3 1 1 0 . 5 6 TT fs. i n CM CO q TT fsl 2 .4 2 | in CM 0 . 4 0 o ’ P C 2 - 3 0 0 1 | | 2 .8 2 | 1 2 .4 2 1 1 l'O l 1 j CO m m fs- CO CO CO CO q fs. CO CO CO I o ! | o o ’ O o ’ to* r l P C 2 - 2 6 0 | 1 : | | 2.3 0 | [ | 1.53 0 .3 8 | I | 1 3 .0 3 | | 0 . 3 8 | 1 1 m 1 i | T— CM in CM CO to | CM t CM fs. to to cn o CM CO 4 .8 9 CM* | o ’ d i t o* 1 to CM*! O CL j i £61 6 £ I i : | 3 .0 6 1 1 " 1 | CM in in to CM CM CM i 4 7 i s 3 . 8 6 CO 1 CM CM P C 2 - 2 0 0 1 | | 0 .3 2 | i 1 O ; 00 i o to c i to to r r q i l ° t ! CM 2.0 7 ] |C\J 0 .4 1 | CM* Io* O i **"* CL t 1 i 1 ! ! Ps. 01 CO ! i o j i o t o CM 1 o ’ o j 1' 5 P C 2 - 1 5 5 | ! r l | | 0 .2 3 | | | 0 . 4 6 0 .2 3 | | | | | | | | | | | | | | | k- Q. CO 3 a £ o> to CL c (O k-0 5 E 8 in CO (0 O £ o ' CO ( S p h a r b u l i S p i r o c y c l j S t a n f s p I P ry m u r [ S l g m o t ejSigmschl n jS ip h a f f | S t a I n f c o( T m r i f b r a ] d |T r o c g l o b jRosal spp. j P a u t e r |P b u ll |P q u in jP ry lu c | 1 jPseunonatl I Q b o s c l i Q c f s e m i IRobtinbrad jSaccorhz spp. jO s a n ru g jPseunonclav|Psubcarin ( P s u b s p h |Q sp p I Q v e n u s |Reus spp 1 (Neolenpere|N e o t e r q jN onopim | | | | | S a m p le |N u m irr |Orbitvalvu ] |Oridtene | | | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced . a o r— O | | Sample | PC2-155 | PC2-180 | | PC2-200 ]| PC2-215 || PC2-260 | 1 PC2-300 I 1 PC2-320 1 PC2-380 1 i | PC1-20 I PC I-40 1 PC I-60 1 (Trochadv | [Uvi spp. ] 1 j i 1 jUviaub | ’5 O ± u o> 0.47 ] (Uvigper | 0.47 1 |Val sp 202 | [ 1.47 0.93 iValmex | i 1 I I : O LO jValspp | i j t jlndet. Miliolid | 0.23 u-> ’ o GO CM Indet. Rotalid | 0.64 | 1.53 1 1.15 | I 1-21 I I 2.46 I I 2.33 I 1 1-04 I CM cn indet. Textular I 3.55 I 9KS 9KS | CM n i O 1 CM O . N CO (0 (0 cn CM CM ! s CM CO CM Tj* o <0 O CO |Misc. Lag/Fis spp I 0.93 1 191 191 1 1 | e | oee 1 2EZ 2EZ 1 CM O I Cv un CM CM cn m tn CO (Total | | 299 ] | 308 || 239 | I 232 | I 208 | 262 O' | OE'O | GO CM CM GO r*“ co 1.52 0 .3 0 0.61 CNJ 16.97 P C I-320 1 CO r- CO CO CM CNJ CM 0 .4 5 O CM o 16.78 P C I-300 1 1 1 2 .49 1 0 .6 8 I I 0 .45 V CO CM CM 0 .2 4 0 .2 4 o 0 .2 4 0 .2 4 o 19.29 2 3 .2 9 P C I-280 1 1 1 1.65 o cn o CO CO CO o CNJ ci o CM o P C I-260 1 1 1 1 0 2 | 1.02 | 0 .34 M* CO CD CD 0.66 0.66 1 o 14.75 1 30.16 1 P C I-240 1 | | 2 .3 0 I I 0.33 1 22.44 | 21.79 1 P C I-200 | I o s e CO ID N. in CM O o 0 .79 CO* CM* 15.30 | 24.54 | P C I-160 | O rr px. d CO CM 26.04 | PCI-140 | i ; 1 i M i l ! in I i i CO N. i j i CM ! ° j s | 00 i i ci i 0 .28 O 'in 1 |r— j S! i CNJ 13.03 | ’ i P C I-120 | ! i ; I | 0.28 | i MM i 1 EO'l CO CO *3“ o i ° ! i/i CO* i j 23.97 | | i i P C I-1 10 i i | | 0.34 | -Od l-lO O O GO CD 8.62 8.62 0.26 | | CM tJ- 35.51 | | | 0.26 | T CNJ CNJ I CM in CM CM ! d o 0 .65 o 20.22 | P C I-0 0 | | 0.22 | | 5.00 | I 1 i 3 *35 C a 0) cn u d Q. (A ■o re o a Q. 2 re T3 £ i re u vt tf> b in c o E Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced O CL G CO Q G CNJ O 1 i | Sample PCI-80 PCI-100 PCI-120 I | PCI-140 | PCI-160 | PCI-200 1 PCI-240 1 PCI-260 1 l PCI-300 1 PCI-320 1 (Cbrugos | o I 1^* n |c CNJ* co ps. co m cn ps Ps cn o ci CO Ps m CNJ in rs (0 in CNJ CNJ Cbwue 3.97 | J Chilool 'c u c > o fe |Cribr spp. | i : i i l 1 i ! i 1 1 1 1 1 I j 1 1 1 ! ; j u 1 3 i i IDiscam spp — 1 — s r n c cn j cn rs in CO CO CNJ Ps. [Eggbrad | 0 . 2 2 2.70 | ! 1 1 0.34 4.41 4.99 1 1.21 . c UJ in a . Q [00 i 1 m o s e cnj o* o in n c j o CNJ CNJ o CNJ r— * jEpiex 1 0.65 M’-O 1 0.33 1 jo ! 1 0.22 1 1-41 1 0.68 UJ *> Q. 0.53 | 0.23 o* in ps. o CNJ CNJ n c m CNJ |Galti | 1.06 | 0.33 | 0.34 I 0.45 1 n c o' n c d n c jGavtrans o* n c |Globaff | 0.34 1I 0.71 | 0.30 (Globova j |Glomchar H 1 1 1 1 i jGlomgord | im1 9' | 99'0 I i z e O CNJ CNJ o 5 jGpoli | 3.91 1 7.57 11.30 | 0.53 | 0.91 TT ps. CO o* TT ’ o cn NT Gumbo | 0.78 | I 0.25 1 | 0.33 | 1.13 O* in cn ID CNJ m o' CO CO 01 o* Gyorbic o CNJTT i i ! 1 (Gyrmard | ; i I 1 1 1 1 1 i | ! 1 1 IGyroid spp. ] i i | j *D o* CNJ CO o r— cn CO o in n" c 0) o >» w O (Hanzconc ] IHaynesgerm | cn CO CO | 860 | in o co in o o* n c tp CO 00 cn o |Hoegele | 0.26 | | 5.23 | 1 3.39 I CO Ps i C 1 tj CO ] Sfr> co* CNJ n c n c o n c q CNJ Ps in Ps q TT rs t CO o q CO cn* T jltum 1 * | 6.39 | 3.69 | [ S. ’S CO w CO a i i i I |Karbrad | 0.33 1 j 1 jLatpaup 1 0.24 | | OE'O | d CNJ | ‘0 9 9 | o CNJ [Lent spp. | | 0.26 | 1 1 1 1 i 1 0.30 1 |Loxtrun 90 | 89'0 o jMartschk CNJ*3“ S'l 2S 0.45 ; 0.61 ..... n c | 9E'l I n c Ps CO CNJ o CO m o CO CO CO i C jMbarl || 0.43 || 0.26 ] 2 CO n c Ps CO CNJ E a a o \ 3.26 | 0.85 0.98 J| 2.90 | | 2.30 |1 6.44 J| 3.29 | PS m CNJ o « cn CO Ci CNJ* n i n c |Ndec || 17.39 || 13.58 17.56 ‘ | 19.39 | I 10.82 |I 16.27 I 1 15.65 1 23.33 iNeocmin 1 264 1 0 | 0 16 1 | OE'O I i — i cn o o O i O cn to i cn cn cn cn i cn 0.61 1 O o’ o ’ o' d i PCI-320 1 i 89‘ 1 ' ‘0 9 8 0.91 [ 1 1 0.30 1 cn CMcn 0.45 0.23 0.23 I 3.17 0.45 0.45 0.23 o’ o’ PCI-300 1 V0 | V20 | 1 0.68 I 1 1 0.23 1 fs. CM CM 2.12 2.12 1 0.24 1 0.71 0.71 1 o’ d o’ PCI-280 1 1 1 0.24 | 1 0.24 1 2.35 | | 0.24 cn to CO | 89'0 IO cn CO cn 0.68 0.68 1 0.34 o’ | o’ PCI-260 1 EE'O I 1 EE'O | | 99'0 I 1 1.02 | tO to CO CNJ « G\ Tf* 1.64 | o O* PCI-240 | | | 0.33 | | 0.33 | 0.33 m CNJ (0 CM 0.44 0.44 1 0.44 1 2.83 2.83 o’ J o’ o’ PCI-200 1 E' | ES'O 1 | 0.22 a CO to to CO fs. CVJ CM CM 1.85 1.85 | CNJ o* 0.53 | o o’ o' PCI-160 | — | 0.26 1 I 0.26 CO 0.57 0.57 j 0.85 | j o* O* d ! o’ PCI-120 | j j Ol-Dd ll-ID O | | 0.85 | i m cn fs. o 2.74 2.74 | ^r 0.34 | OOl-LDd I I ! CO CNJ to to to tO CNJin cn q CMCM CMo 0.26 0.26 1 0.52 | CNJO o’ 0.52 | | O* o’ o* S0 1 S90 I | CM cn cn fs. N. cn CM CNJ 1 CM CO | 1-52 1-52 0.22 o' o’ CNJ 0.43 o’ | o’ 0.22 | o' PCI-80 PCI-80 | I I i aQ. i V) i C N C E i . c Q) Z T 3 v - : w u t s CQ C. CL O' in in CO £ [Spirocycl z CL [O. [Spharbul |Trocglob |Stanfsp [stanfcom z |Pyrg spp. iQcfsemi | spp [Reus | [Robtinbrad jSaccsphar | | jSiphaff | [Psubsph [Psubsph jQbosci | | spp. [Rosal | [Oridtene [Oridtene ( [Pquin (Pryluc jPseunonatl jpseunondav 1 | | | jQvenus | (Neoterq (Neoterq | & |Orbitvalvu |Orbitvalvu jOsangcul (Osanrug | | ( | | [Neolenpere Sample | | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 265 O' ] OE'O I 9) rs. 0.30 co' P C I-320 1 I I 300 | 0.45 | | PC I-300 1 I 12.70 1 I 383 | | TT cn CVJ CO o CO P C I-280 1 1 1 1-65 1 8.24 | fs. CVJ i i P C I-260 | I EE’O | | EE'O I 1 0.34 I | 7.80 | 0.33 0.33 1 I I PC I-240 1 | 6.56 | 1 284 | CO CO CO to 1 1 P1 C I-200 1 | 0.22 | | 0.22 | 1 | | PC I-160 | ! | 0.26 1 | 7.92 ] 1 348 | | 1.03 | i 1 ! CO 1 | CO | | PC I-100 | 1 5.74 | CO rs. CO o CVJ o [ PC [ 1-80 PC 1 I 0.22 | 1 5.22 | 1 ] Sample Sample | Q. 202 inCL &in "5 > > Lag/Fis |Misc. spp (indet. (indet. Textular | r> (indet. Miliolid (indet. Rotalid | ] jValmex jValmex | |Val sp |Val sp (Troctiadv (Troctiadv jllviaub | (UvigH'C (UvigH'C |Uvigper | | 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m I 7 6 6 CO • cq CM 2.56 0.32 0.64 0.64 CM CM 0.64 CDE 9‘ | 9Z‘0 1 1 m CO (D O | 9Z'0 i CO cn sr 3.93 2.36 3.40 3.40 1 2.36 I X 0.26 CM CM cn a. CD SOL-lXdfl 1 7 S 8 I 1 19'E 1 | 1 0.26 1 0.26 0.79 J 1 0.26 CD CM cn cn fs. cq 0.72 0.72 O | O CM 997 9 9 1 1 0.72 i | O 1 CO1 CO O 0 O CM j CO N. cq cq i 4.73 0.23 0.23 | o 0.45 | S3E 1 i ! ! 0.23 | L L 0.45 I I 0.68 1 1.13 1 | ! ! r^ O rs. n. O rs. 1 EE'O tO O 10 |cd O j to 0.33 2.33 2.33 | CM 12.00 12.00 I O d | d BPX1-55 BPX1-55 | IV'E | 1 1 I 0.33 I CM rs. | cn M" cn cn cn cn CO CO 0 i O CM 0.68 CM o 24.57 24.57 | BPXt-25 BPXt-25 | ! | | 1 i 1 i 1 rs. *• rs. IO co 1 CMm 00 CM cn | j 5.39 5.12 5.12 1 d ! 0 O 0 0.54 O 30.19 30.19 1 1 PCI-440 | I | | 0.54 | 1 1 i | CNJ (NJ 1 rs. i ! CMCM in fs. CM CM CM ; <0 ! | CMCM CNJ CM 1.57 O O CMd CM* d o 19.73 | 0 i PCI-400 | d i | | 0.45 I ! i I 1 j I OS'I CM l CM CO CM 1.38 1.38 | O CM O 0.23 39.52 39.52 | PCI-380 | 1 ! 1 . i 1 1 n-o rs. 1 I I i CO 1 r^ fs. to i CO i TT i d 1 i TT 0 d CM 0.33 PCI-360 PCI-360 | i 1 9' | 91'0 I 1 i 1 1-16 1 I! 1 1 j I El'l CD CD I in I* 9.85 0.32 | O O 1 — 33.28 33.28 | PCI-340 | i | | 0.16 l 1 1 | | | | | ] | | | | 1 | ] | | 1 V £ *o u a z c o Q. iS 3 a 3 V) *cn 4 CA CA U> JO V) 5 (A E c CO ~0 S. 3 CO (0 JO JO Btrans spp Bui Bfragl CD Bbarb CD CO CO L) U u u |Cbcorp ICbincras < [Cbpchbath (Cbpchsubl (Cbrob 1 |Cbbrad |Cbbrad (Bsubspin (Bsubspin jButacul [Bulalz jAnomlglob jAnomlglob |Bolow [Cassidtenu (Cassneo (Casub [Bordin [Bordin (Bpauia (Bpauia eleg (Bullrnin |Bulmex (Aderglom (Aderglom (Ampark (Amphisgib | | Sample |Aturg |Aturg jBsubar (Bulmarg (Bulmarg Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. jNeocmin CM o ’ cn o p"-. CM o ’ cn 3.3 1 30.03 I 3.5 1 32.85 I 2.4 | 20.14 | 2 .2 0 2 | 2.0 1 24.10 I 1.4 | 18.74 | |Ndec 1.9 | 13.29 | o ps- ID CM o o CD CM ID o ci M- q _ .65 0 _ 1 [Mpomp 0. 3 .3 0 | CM o ’ f^. cn 0.52 0 1 0. 8 .6 0 | 92 .9 0 ] 0.32 | TZ o 2 CM CM o ' cn cn o* o 1? 1 1.?2 1 I 89'0 | 80' I 31 I 3.14 1 04 | 0.45 I 01 j 0.17 I 03 | 0.33 | (Martschk ID o 03 | 0.33 | Lxrn 1 |Loxtrun (O o ’ 0.81 1 Ln sp 1 spp. (Lent cn o* | St-0 1 cn CM d 1 710 | ID 09 | 0.96 I Q. 3 CO Q. CQ q CM N. in -J o rs. d co rs. q «v, CM o’ CM CM o ’ co o* 03 | 0.33 | Krrd | [Karbrad o* Tj- in ID o ’ (Karapic (Karapic i 2.33 | 0. 8 .6 0 | i Cl o* o m q CM CO CM q q rf* CM r* . cn jHoegele jHoegele 02 | 0.22 | i o* o o CM Cl (O q co’ cn CM N. q N.* cn CD V in rr o 80 8 ___ 0> O) (/I 0) c S' o q Hncn | (Hanzconc 43 | 4.33 1 25 ] 2.53 | (Gyroidneo 66 .6 0 ♦ | 2.39 | 1 1 960 | m 1 ! Grisp | jGyroidspp. 1 1 1 i ! i i i Grad | (Gyrmard in o 04 | 0.45 1 | 0.12 1 1.83 1 2 0.7 [1 06 | 0.67 | (Gyorbic .8 J 0.68 03 1 0.36 1 03 | 0.32 1 Gmo I (Gumbo 04 | 0.46 | Cl o Cl r*. d | | 890 | Z0‘2___ ] cn cn o* 88 .8 2 2.93 Goi 1 (Gpoli CM q CM P^ o o ’ to m o* Cl m o CM CM Gogr | (Glomgord Goca | (Glomchar 0 CNJ i i i i 1 1 i i 1 Gooa 1 jGlobova 04 | 0.45 | Goaf | jGlobaff o co o 00 1 6 2 ‘0 | CO q N-* 52 .5 0 Gvrn ] (Gavtrans Cl cn 1 1 06'0 1 O o r“• . 2 0.3 6 .2 0 Gli | |Galti Cl o N. CD o o CM m o CM o M- cn o ’ o* | OS'O 1 cn a cm UJ ’ > ' i .2 1 0.72 . 5 0.4 .5 | 0.45 Eix 1 (Epiex .5 | 0.35 in o N- q mcn s -jo* 00 Cl CO CM o Epsp | (Elphspp id o Cl o* 5.50 1 i I ! Egrd | jEggbrad q cn CO CM in cn cn T— co; VjtM* in ir- CM q to CM in 1 i° ’ i s 1 CD 1 ! icm p | spp Discam I j i i ! ! i i i r i w V) 3 .Q .C o i 1 Cirp. | (Cribrspp. .2 1 0.72 ; Crivl | (Corninvol | i ! ! Cio) | jChiloo) 2.09 . 8 2.8 .3 1 4.73 .3 | 2.33 .8 | 3.88 Cwe | |Cbwue Cl CO (\i CO o' CM N. (D o ' o in q CM j CVJ j Cmo | |Cbmgos P115 1 BPX1-105 P15 | BPX1-55 P12 | BPX1-25 P18 I BPX1-80 -0 | I-400 C P -4 | I-440 C P -6 | I-360 C P -8 | I-380 C P -4 | I-340 C P 1 | Sample X a. CD 1 1 S H -lX d fl Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. 268 m o Tj- CM o C i TT cq (O CO cq p%. CO CO 0.32 0.32 I r— d o o o BPX1-145 BPX1-145 1 , , 6.07 9' ] 9Z'0 I 1 0.32 1 1 0.32 1 Sl-Xdfl d ll-lX S | CM CMr“ O) fN. in m m CO CO «n in o 1.05 d 2.36 d CM d ZZ'O 1 1 0.26 | 1 0.26 1 0.52 in CO CM CO CO CM CO CM o CM o o o 1.44 1.44 I CO 397 1 P*I O BPX1-105 BPX1-105 1 , , 0 9 8 | | 1 0.36 £20 I 1 1 0.36 0 1 060 CO1 m m o O C i 1.35 1.35 I 0.23 0.23 I 0.45 | o E o CO Z9‘0 I | 0.68 o 1.33 d | d d BPX1-5S BPX1-5S | - | | 0.33 | 0.33 | | 1 0.33 1 m CNJt TT CO CM CO CO cO CO r»- q CO CO CO 1.02 1.02 | 0.68 0.68 | 0.68 0.34 | d d o o £ d d CM co fS 1 frSO 1 1 0.34 r». N- N. M* CM CNJ m CM m 4.58 4.58 | o o O o 6 PCI-440 I i : i j : io c\j CM 1 [S. CM TT i jtn I'M CM CO CM CM s 1.12 1.12 1 0.67 ! id 0.45 o o CO o CM* o PCI-400 I i | j ! ° 1 9- | 9t-0 | 1 0.67 | | 0.22 I | 0.67 j OS* I m CM i CO CO CO t CM M" o o O 14.06 o I PCI- 3 8 0 | i | 1 0.23 | 1 0-12 I | 1 0.12 I | 0.69 I O 1 CM CO N. i m 1 CO CO i o* |«n o* 0.66 o | 0.17 o | i PCI-360 i i 91'0 | 91-0 1 1 910 I 1 0.17 I | 0.33 | | 0.66 0.33 | 0.66 1 t si CO CM CM 00 CM CO CO CO CO 2 ! 5.49 ’ o* o o 0.16 o O o | | 0.81 | | | ( I d 10a . N Sample L. JZ a o 3 in 3 a E a . § E S' cfl O) Ou Q- & CO in (Spirocyd (stanfsp (Stanfcom |Trifbrad (Trocglob |Pyrg |Pyrg spp. iQbosci | ISaccsphar [Sigmoten , |Spharbul jPsubsph jPsubsph iQcfsemi iQlamrk | (Qvenus Reus spp I | |Robtinbrad spp. [Rosal | | (Siphaff jNeoterq jNeoterq INurnirr |Orbitvalvu [Oridtene (Osangcul jOsanrug | | IPauter iPbull |Pquin | | | | | (Nonopim (Nonopim (Pseunonatl (Pseunonclav | | [Neolenpere [Neolenpere |Psubcarin |Psubcarin | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LO CM LO T*«t CO fs- 0.32 0.32 o LO 2 CO I I 283 | 9Z‘0 I | 3.51 1 co CMo o cq tn r^ |S* r* d o CO BPX1-115 BPX1-115 1 E' | ES'Z | | 1.83 | CM LO CM CO o CO CM BPX1-105 BPX1-105 1 1 0 CO 2 * 8 1 O LO rs. CM CM £ * CQ : : 2.48 1 | 1.58 | 1 1 I o rs. o CD 281 1.67 1.67 o 5.67 BPX1-55 BPX1-55 | I L 1 | 89'0 CM 1 6ZZ o 0.34 0.34 | | | BPX1-25 | 1 | 0.68 | 0.68 | 2.39 | | rs. N. GO CM CM LO d V 3.77 leo PC1-440 PC1-440 | ! | | i 6601 I | I | i ji/i u , r r ! o 393 j I |3 PCI-400 PCI-400 ______ 1 ! | i ' 6 9 | j 0 S 8 ID | I CO __ PC1-380 j j j 1 o !cm LO ! I ® o |c \j 582 j PCI-360 i 1 1 9 i 1 CM ' 1 j '01 i CO CT) o t o I i 0.48 o o' CM i 1 PCI-3401 1 | | | | | | | | | | | | t Sample 202 [indet. Mill olid olid [indet. Mill (Indet. Rotalid jlndet. jlndet. Textular Lag/Fis |Misc. spp [Total |Valmex |Valmex (Valspp jTrochadv jTrochadv |Val sp |Uvi spp. |Uvi (Uviaub lUvigH-C (Uvigper (Uvigper Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced | Sample ] BPX1-160 1 BPX1-175 | BPX1-205 | BPX1-235 | BPX1-260 | BPX1-290 I BPX1-315 1 SZ-OlXdfl I BPX10-55 1 BPXIO-85 1 < ■o 0) h. D) o E i 1 0.31 1 1 (Ampark | ! j 1 i ! ! | t [Amphisgib | < a c 01 0 o |Anomlglob | __ coI 0 6 9 | CO |Aturg | 10.26 | 6.91 | 20.93 1 34.10 | CNJo’ LO j ; | 5.88 6.15 S. |Balb | CO cq CO CVJ cq o ! i i i I I ! I i 2.08 1 (Bbarb | 0.33 : |Bfragl | Bo! spp. t !cn* j 0.28 | 9 I 99' T GV 1 281 I CNJ(O q c fs» cq CO cn cn r— CNJ Bolow ___1.60 j 2 -9 ? (Bordin | [Bpaula | i cq CNJ O* in cn O* cn o CNJCO ’ o cn cn [Bpusil | \" 0.33 j ! 1 0.37 | jBsubar | O | 8E'l [ o’ CNJ o cn |Bsubspin (Btrans | |Bul spp | i 1 i i l 1 K | 6Kt cnj r- in cq pw jBulacul ] i 0.53 1 0.69 1 ’ (Bulaiz 1 0.93 |1 0.69 I 4.00 90 ] 990 1 o o |Bulimin eleg | (Bulmarg N. | EE'O | o d CT>cn |Bulmex ] 0.66 | 1.06 | | 3.73 || 0.84 | 1 0.35 I 1.23 'S. co CO CO CNJ <■ CNJ cn cn «— o CNJ o’ cn m o’ cn *» 3 e 3 ! i I (Cassneo 0.87 0.53 1 0.66 1 cn o cn o CO CNJ cn |Casub 2.33 | 3.31 f 0.33 | 2.61 L 2.52 1 1 7.96 1 |Cb spp. ] 1 | 817 0.92 N. 00 CO cn CNJ Cl CNJ cn O cn Gl CNJ*cq o o in jCbbrad , 4.65 | 1.56 r— CNJm CVJ m [Cbcorp ! 1 0.35 1 jCbincras ’ o cn m u ■o fs. | 660 o CO cn cn E 3 c | 0.33 CNJ CNJcn |Cbpchbath I 1 i cn 1 f o ^ Cbpchsubl | ! i i ! i i 100 i O* cn Ps. Cbrob I 0.33 I 0.28 1 1.54 | to 1.23 3.08 0.31 1.54 0.92 0.31 2.77 0.92 0.31 5.54 3.08 0.69 1.04 3.46 3.08 6.57 5.54 4.50 1.38 0.69 2.77 4.62 0.69 0.31 0.35 3.46 2.77 0.69 BPXIO-55 BPX10-85 1.25 1.56 1.87 2.08 0.31 1.25 1.87 0.31 0.62 0.62 2.80 0.93 2.49 0.35 3.08 4.36 0.93 0.31 BPXIO-25 1 .6 8 1 .1 2 0.56 0.93 0.84 3.64 0.62 0.56 BPX1-315 1 .1 2 1 .1 2 1.87 0.84 3.74 1 .1 2 1.87 1 .1 2 0.37 0.37 1.49 1.49 8.96 2.24 0.37 0.37 0.33 0.33 1.87 4.05 0.98 0.98 25.57 19.78 35.29 6.23 1 .0 0 1 .0 0 0 .6 6 0.33 0.33 0 .6 6 0 .6 6 0.33 2.33 0 .6 6 0 .6 6 0 .6 6 0 .6 6 1.33 0.33 1.33 1.33 0.33 0.75 0.28 1.33 1.33 1.06 0.33 1.31 0.37 1.33 1.33 0.27 2 .6 6 1 .0 0 0.80 2.13 7.71 2.33 1.64 0.27 0.33 0.33 0.75 0.53 30.32 22.26 BPX1-205 BPX1-235 BPX1-260 BPX1-290 1 .6 6 1 .6 6 1 .6 6 0 .6 6 0.33 0.53 0.99 0 .6 6 0.33 1.74 0.33 1.45 1.74 2.65 0.87 1.32 0.87 0.58 2.33 0.29 3.20 0.99 3.78 2.98 0.29 1.99 0.29 0.33 32.85 22.19 BPX1-1 GOBPX1-1 BPX1-175 Sample Karbrad Neocmin 0.58 Glomgord Martschk Mpomp Ndec Gavtrans Mbarl Gyroid spp. Gyroid Latpaup Hanzconc Haynesgerm Hum Karapic Loxtrun Globa ff Globa Globova Epiex Gpoli Epvit Galti Gyrmard Gyroidneo Hoegele Cbwue Chilooi Cushbrow Discam spp Eggbrad Elphspp Gumbo Gyorbic Lent spp. Cbrugos Glomchar Corn invol Corn Cribr spp.Cribr Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to 10 0.62 0.92 3.38 3.69 2.15 0.92 0.31 1.73 1.23 1.38 1.23 0.69 0.31 1.04 0.69 0.35 0.35 5.54 0.69 0.69 3.81 0.35 0.350.35 0.31 BPX 10-55 BPX BPX10-85 1.56 1.87 0.31 0.93 3.12 2.49 0.93 1 .1 2 1 .1 2 1.96 1.25 1 .6 8 0.56 0.31 6.72 0.84 3.74 5.19 0.28 0.84 0.31 0.28 BPX1-315 BPXIO-25 1 .1 2 1 .1 2 1 .1 2 1 .1 2 0.372.61 2.42 0.75 0.37 5.60 0.37 0.33 0 .6 6 0.33 1.31 3.36 0 .6 6 0.33 0 .6 6 9.84 BPX1-260 BPX1-290 1 .0 0 1 .0 0 1 .0 0 1 .6 6 0.33 0 .6 6 0.33 0 .6 6 BPX1-235 2.39 0.27 0.53 0.80 0.808.78 1.99 6.64 0.53 0.33 BPX1-205 1.32 1.32 1.32 0.80 1 .6 6 1.99 0.80 0.33 1.31 0 .6 6 0.99 0.99 6.95 0.330 .6 6 0.53 0.33 1.25 BPX1-175 8 .S 1.16 1.16 2.33 2.98 3.46 4.32 2.62 0.29 0 4.65 5.30 0.29 BPX1-160 Sample Spbarbul Trocglob Spirocycl Stanf sp(com Stan 0.27 PbullPryluc 1.45 Pry mu r mu Pry Pseunonatl Qcfsemi Qlamrk Saccsphar Sigmoten Sigmschl Siphaff Pquin 0.27 0.33 1.56 Reus sppTrifbrad 0.33 Saccorhz spp. Qspp Robtinbrad Neoterq Nonopim Numirr Osanrug Pauter 0.87 " Orldtene Pseunonclav Psubcarin Psubsph Pyrg spp. Qbosci 1.32 Rosal spp.Rosal Qvenus Neolenpere Osangoul Ortoitvalvu Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 273 LO CO cn in in r— cn 6 CM cq cn in r“- cn 2.15 tn to o CQE m m in CO co in co O 6 cn cn cn cn cn in h* o' d TT CM 03E CMcn jcn CM(0 cn k to in O o d ICO o cn BPXl 0-25 BPXl 1 m cn (0 CM CM Tf i m CO in TJ* O* o CVJ cn aE r-. o m tT cn to CM O) d CM o CM CM BPXl-290 BPXl-290 | (00 CM CO cn to CM O CO 1 cn O cn O in cn O cn a\ co d CM CM CM [ [ BPXl-235 | j in 1 0 i 1 CM cn cn G)\ ito 1 in k. V)& « Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced CQ 0. X LO CL 6 6 CD Z «• m | Sample | BPXl 0-140 | BPXl 0-185 | BPXl 0 -2 1 5 BPXl 0-260 1 BPXl 0-290 1 < ■o D 6 o> 5 < 1 & jAmphisgib | (Anglocfbet | (Anomlglob | 1 990 l I < 0- CD ZS'9 w CO LO* LO ^ o — 3 O) t t 4 .05 1 17.05 8.05 1 ©. CO -Q | 890 I • CM o N- 03 t____ 0-54 I |Bbarb | 0.38 I I 3.45 I Bfragl Bol spp. 0 2 0 I | I WO WO I o l o | Z9'9 I CD |o o c - CO cn O o 5 I 2.36 I| 4.55 I I o' |Bordln | CM CM jBpaula | 1 j i 8' ] 8£'0 I I ZS'O 1 _____ 0 28 CO ____ ps. O* CM ' o IO CD 3. V) jBsubar | o* cd CM (Bsubspin I (Btrans | CD 3 V) Q. Q. co; CO[CM! CD *3 CD CD *r CO CD ' o cq CM o *5 3 CO | 1.35 | 1 ! 11 j !1 (Bulalz o CM | | wo I o w 1 o* ps* CM o CM (Bulimin eteg | o’ jBulmarg | cq | ‘0 S 9 I CO lO cq CM fs* M- cq jBulmex | 0.22 ] 1 2.45 I CO (Bufspfc 4 .39 3.03 I 2.05 I 6.25 1I 9.48 I [Cascras | I 1-02 1.09 | 98'0 1 j I 1 | | jCasscurv I i i i i U ■o w CQ CO(A 3 CJC | M* 291 I o jCassneo | 3.79 | | 0.86 | t-l' 1 l 'l l - t 1 L ’ Et CM* N- CM CO CD CDo [Casub 1 3.89 10 N- ’ o 1 ZS’O | XJ u rr rr (/>a | 1 id; Ips-i j ! 1 L0 L 1 1-36 1I j [ 1 U .Q *o m Zl'Z CM CD fs* d m CD w CQ 2.70 ; 1 (Cbcorp 1 Cbincras I ’ o • |Cbmund | | 89'0 r [Cbpchbath | .09 1 1 1i 0.29 1 0 .5 6 (Cbpchsubl 1 . . . . rt a __ | ____ (Cbrob 1 2.62 1I 0 .6 8 0.20 1 1 ZS'O 275 1.11 1.11 3.33 6 .1 1 6.67 2.78 7.78 0.56 0.56 0.56 1.44 1.44 3.74 0.29 0.57 0.29 0.56 1.90 1.90 2.59 3.53 2.72 3.74 2.17 1.15 2.99 5.17 0.27 0.57 8.42 4.89 0.27 1.44 0.82 0.57 0.27 1.23 1.23 1 .0 2 1 .0 2 1.64 1.84 1.09 0 .2 0 0 .2 0 0.41 0.41 0.82 0.41 1.15 BPXl 0-215 BPXl 0-245 BPXl 10-260 BPX 0-290 BPXl 1.14 1.14 3.41 3.79 0.38 0.38 0.38 0.38 1.01 2.70 0.76 3.69 3.04 0 .6 8 8.78 4.17 1.64 1.36 BPXl 0-140 BPXl 0-185 BPXl 1.97 2.40 2.70 1.14 2.62 0.44 0.87 3.28 6.42 0.76 6.15 3.49 2.36 0.44 4.590 .2 2 4.05 4.92 9.63 0 .6 6 1.01 2.62 0.340 .2 2 1.52 1.43 1.63 0 .2 2 Sample0-115 BPXl Epvit Galti Globa ff Globa Elphspp Eplex Gavtrans Mbarl Cbrugos Cbwue Chilool Corninvol Discam spp Eggbrad Glob ova Glob Glomchar Glomgord Gpoli Gumbo Gyorbic Gyroidneo 7.86 Martschk Mpomp Cribr spp. Cribr Cushbrow Gyrmard spp. Gyroid Hanzconc Hoegele Hum Karapic Karbrad Latpaup Lent spp. Loxtrun Ndec Neocmin Haynesgerm Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 276 — ____ 1.11 1.11 1.67 0.56 0.56 5.00 0.56 8.89 BPXl 0-290 BPXl ____ ------1.72 0.57 0.57 0.57 2 .0 1 0.29 0.29 11 .2 1 5.16 0.27 2.72 0.54 1.44 7.34 1.72 0.27 0.29 1 .0 2 2.05 5.12 2 .6 6 0.41 0.61 0 .2 0 0 .2 0 0.61 BPXl 0-215 BPXl 0-245 BPXl 0-260 BPXl ------1.14 1.63 1.15 1.52 1.64 3.80 1.14 1.64 - 2.27 1.43 3.79 0.76 0.61 2.65 0.38 0.76 0.61 0.82 0.38 10.23 5.12 7.88 .... BPX10-185 ------• - - ___ 1.35 1.69 2.36 2.03 0 .6 8 0 .6 8 0 .6 8 7.43 0.34 0 .6 8 0 .6 8 0.34 6.44 0.34 0.34 4 .0 5 BPX1O-140 ------___ 1.97 3.49 2.40 0.34 0.76 0 2 2 0 .2 2 0 .6 6 0 .2 2 0.87 4.05 0.41 8.95 0 .2 2 0 .2 2 1.01 0 .2 2 BPXl 0-115 BPXl ------Sample Spharbul Sigmschl Spirocyd Stanfsp Stanfcom Saccsphar Siphaff Pbull Pryluc Trifbrad Trocglob Pseunonclav Psubcarin Psubsph Pyrg spp. Qcfsemi Numirr Qspp Osangcul Osanrug Pauter Neoterq^ Prymur Neolenpere Saccorhz spp. Sigmoten Orbitvalvu Oridtene Pquin Reus spp spp.Rosal Nonopim Pseunonatl Qvenus Robtinbrad Qbosci QJamrk Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 277 o 0) CM CM CO ■n- 6 CM r^. CO CM CM CO £ CQ O ID CM r - m r^. CO TT o 6 in CO CO rr O CM o cn s CQ m CO cn cn N. ^r 6 CQ in CO «n cn CM cn 2 CO t to 1 m rr CO ten a o CO N. ° ! iin CM CM TT CL m | , i i LO i CO i CM CO cn O 1 im 6 m CO cn O i m cn ! CM ° 2 i m i 1 1 i o ! i i CM cn CM Icn 6 rs. o O fM. ! rs. CO 1 cn 1 cm X — j u . 1 CQ i i m 1 i j CM CM cn 6 CM 21? CM m cn Io* CM o *- •— a . | CQ i i 1 I I | I 1 | a sp sp 1 202 .S2 > (Indet. Rotalid (Indet. Rotalid (indet. Textular | | | Sample jUviaub lUvigH-C |Uvigper |Uvigper (indet. Miliolid | Lag/Fis |Misc. spp | (Trochadv (Trochadv spp. (Uvi | | |Valmex | ITotal ITotal |Va Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA Megan H. Jones, daughter of Matthew and Joan Jones, was bom in Minneapolis, Minnesota, on Friday the 13th of January, 1956. Her interests in earth science, which began while watching Jacques Cousteau on many a Minnesota winter's night, led her to a Bachelor of Science degree in Geological Oceanography from Florida Institute of Technology in Melbourne, Florida, in 1983. After working for the U.S.G.S. Branch of Atlantic Marine Geology at Woods Hole, Massachusetts, she entered the Department of Geological Sciences at Old Dominion University in Norfolk, Virginia, where she obtained a Master of Science degree in Geology in 1990 under the direction of Dr. Randall Spencer and Dr. Stephen Culver. Her continued interests in foraminiferal ecology and stratigraphy and paleoceanography led her to Louisiana State University to work on a Doctor of Philosophy degree under the direction of Dr. Barun Sen Gupta. She plans to relocate in Minnesota, at least temporarily, where she hopes to enjoy a more humane climate. 278 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DOCTORAL EXAMINATION AND DISSERTATION REPORT Candidate: Megan H. Jones Major Field: Geology Title of Dissertation: Late Quaternary Foraminifera from Lower Bathyal and Abyssal Sediments, Gulf of Mexico: A Record of Paleoceanographic Change Approved: Major Professor and Chairman DeJ Luate School EXAMINING COMMITTEE: Date of Kxamination: February 26, 1997 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. d) + # • = A : Surface Water Surface Water Surface Water Bottom Water 1 Productivity Productivity & Nutrients Temperature Environmental StabiKty Mass Bottom Water Corrosivity % total % 513C warm cool steno eury SpDiv/E deeo inter Rvs.D Hoeg P&Q SAR CaCO, planktics X planktics planktics planktics planktics (Dentfoc) (UNADW) (GNAIW)