Scholars' Mine
Masters Theses Student Theses and Dissertations
Summer 2012
Palynomorph and palynofacies assemblages of neutral-alkaline and acid lakes south of Norseman, Southern Western Australia
Lutfia Grabel
Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses
Part of the Geology Commons Department:
Recommended Citation Grabel, Lutfia, "Palynomorph and palynofacies assemblages of neutral-alkaline and acid lakes south of Norseman, Southern Western Australia" (2012). Masters Theses. 5209. https://scholarsmine.mst.edu/masters_theses/5209
This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected].
PALYNOMORPH AND PALYNOFACIES ASSEMBLAGES OF NEUTRAL-
ALKALINE AND ACID LAKES SOUTH OF NORSEMAN, SOUTHERN WESTERN
AUSTRALIA
by
LUTFIA GRABEL
A THESIS
Presented to the Faculty of the Graduate School of the
MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY
In Partial Fulfillment of the Requirements for the Degree
MASTER OF SCIENCE IN GEOLOGY
2012
Approved by
Francisca E. Oboh-Ikuenobe, Advisor Wan Yang Melanie R. Mormile
iii
ABSTRACT
The Yilgarn Craton in Western Australia hosts hundreds of shallow ephemeral hypersaline lakes, the majority of which have acid to neutral pH values. As part of a multidisciplinary study of the evolution of hypersalinity and acidity in the region, three drill cores were studied for their palynofacies and palynomorph contents in order to characterize palynofloral response to environmental changes. Drill cores from two acid lakes, Prado Lake (PL1-09 and PL2-09) and Twin Lake West (TLW1-09), and the neutral-alkaline Gastropod Lake (GLE1-09) south of Norseman recovered Miocene to Holocene sediments of the Revenge and Polar Bear formations. Transmitted light microscopy was used to identify the dispersed organic matter (DOM) as well as palynomorphs. Statistical analyses were performed only for palynofacies since the palynomorph abundances were low. The palynofacies study revealed that the comminuted phytoclasts are the dominant components in the four drill cores; however; there are subtle differences in DOM distributions, even in drill cores from the same lake due to the dynamic nature of the environment. Lake dynamics appear to be controlled by flooding, evapoconcentration, desiccation, and reworking and eolian erosion. Modern observations indicate the possibility of a lake undergoing more than one process at the same time, resulting in different depositional mechanisms. Palynomorph analysis revealed that: 1) an open woodland vegetation with shrubs and herbs (Chenopodiaceae and Myrtaceae) had succeeded the much wetter climate of the Paleogene; 2) reworking has been a part of lake history as evidenced by the recovery of late Eocene palynomorphs (Nothofagidites and Aglaoreidia cyclops) at almost all depths; 3) the first record of a salt tolerant alga, Dunaliella, in the drill cores is likely be an indicator of the onset of salinity in the region; and 4) the apparent absence of Dunaliella in the most recent sediments in the neutral-alkaline Gastropod Lake may be related to either predation by the gastropod Coxiella or the possibility that this Dunaliella species is acidophilic. Both probabilities suggest that Gastropod Lake has become more neutral-alkaline with time.
iv
ACKNOWLEDGMENTS
First of all, I would like to sincerely thank Allah, my God, the Most Gracious and Most Merciful, for blessing me and guiding me through out my life and my study, and for enabling me to complete my M.S. degree by placing good people who have helped me along the way. “If you should count the favors of Allah, you could not enumerate them.” (14:34) “The more you thank Me (Allah), the more I (Allah) give you” (14:7). My sincere thanks and deep gratitude are expressed to my wonderful advisor Dr. Francisca Oboh-Ikuenobe who has been more than an advisor to me. Thanks to her for accepting me as one of her students, for her guidance, for her support not only academic but also socially, especially during the 2011 Libyan crisis. Without her I would not have reached my goal and received my M.S. degree. I also gratefully thank Drs. Wan Yang and Melanie Mormile for serving on my committee, and for their help and cooperation. Sincere thanks also to the U.S. National Science Foundation for funding this project, and to all the other researchers involved in this project, who helped me during my studies. Special thanks to my fellow students Carlos Sanchez Botero, who has taught me and helped me a lot, Robert Haselwander who always offered his advise and help, Kate Schlarman for her contribution to analysis of Twin Lake sediments, and Marissa Spencer for being such a good friend. Last but not least, no words can express my everlasting gratitude, thanks and appreciation to my beloved parents and grandparents for their love, care, and sincere prayers especially during my time in the U.S.A. Their support and encouragement were my motivation toward accomplishing my dream. Thanks to my beloved sisters and brothers, in particular my brother Emad who accompanied me during my study journey. Without him accompanying me I would not have succeeded in the U.S.A.
v
TABLE OF CONTENTS
Page
ABSTRACT………………………...……………………………………………………iii
ACKNOWLEDGMENTS…………..……………………………………………………iv
LIST OF ILLUSTRATIONS………………………………………………………….....vii
LIST OF TABLES……………………………………………………………………..viii
SECTION
1. INTRODUCTION…………………...…………..……………………………..…..1
2. GEOLOGICAL SETTING……………...... ……………………………………..3
2.1. INTRODUCTION ………………………....………….……………………..3
2.2. STRATIGRAPHY……………………………………………………… …...4
2.3. LAKE CHARACTERISTICS ………………………………………… ……5
3. LITERATURE REVIEW……………………………………………………..……9
4. METHODS……………………………………………….…..…………………...12
4.1. CORING………………………………………………………………….…12
4.2. SAMPLE PROCESSING AND ANALYSIS…………………….…………14
5. RESULTS…………………………………………………………………………16
5.1. LITHOLOGY……………………………………………………………….16
5.2. DISPERSED ORGANIC MATTER………………………………………..16
5.3. PALYNOMORPHS…………………………………………………………27
5.3.1. GLE1-09 and PL1-09……………………………..……………….27
5.3.2. TLW1-09…………………………………………………………..32
vi
6. DISCUSSION…………………..…………………………………………………41
6.1. LAKE DYNAMICS AND PALEOENVIRONMENTS…………………....41
6.2. PALYNOFLORAS …………………………………..….………………….43
6.3. PALYNOSTRATIGRAPHY………………………………………………..47
6.4. DUNALIELLA AS A SALINITY PROXY………………………………….47
6.5. NEUTRAL-ALKALINE VS. ACID LAKES……………………………….49
6.6. EVIDENCES OF REWORKING…………………..………….……………50
7. CONCLUSION………………………………………..…….……………….……51
APPENDICES
A. PHOTOGRAPHS OF COREHOLES TRAYS………………………….……53
B. SAMPLE INVENTORY AND QUANTITATIVE
PALYNOMPRPH RECORD…………….…………………………………...58
C. AVERAGE LINKAGE CLUSTER ANALYSIS FOR EACH INDIVIDUAL
DRILL CORE………...... …..61
BIBLIOGRAPHY…………………………….………………………………………….64
VITA………………………………………………..……………………………………71
vii
LIST OF ILLUSTRATIONS Figure Page
1.1. Map of the study area in southern Western Australia………………..……..………..2
2.1. Lithostratigraphy of Lefroy and Cowan Paleodrainages ………….…………………6
2.2. Geological settings of saline lakes in southern Western Australia. ……….…………7
4.1. Rotosonic drill rig coring at the four sites studied ………………..…………..….…13
5.1. Idealized lithologic column shows the main deposits occurring in the coreholes ….17
5.2. Lithologic columns and scanned cores of some horizons in the Prado Lake coreholes…………………………………………………….………………………18
5.3. Photomicrographs of DOM in the four drill cores ………………………………….20
5.4. Distribution graphs of relative abundances of DOM……………………….……….24
5.5. Dendrograms for average linkage cluster analysis of the entire palynological samples from the four drill cores……....…………………………..………………...26
5.6. Photomicrographs of reworked trilete spores in GLE1-09 and PL1-09………..…...29
5.7. Photomicrographs of reworked gymnosperms in GLE1-09 and PL1-09…………...30
5.8. Photomicrographs of reworked angiosperms in GLE1-09 and PL1-09……………..31
5.9. Photomicrographs of contemporaneous pollen in GLE1-09, PL1-09 and TLW1-09……………………………………………………………………………33
5.10 Photomicrographs of contemporaneous pollen in GLE1-09, PL1-09 and TLW1-09……………….……………………..………………………………..34
5.11. Photomicrographs of selected algae and fungi in GLE1-09, PL1-09 and TLW1-09…………………………………………...……………………..…....35
5.12. Palynomorph abundance distribution graphs………………………………………39 6.1. Core scans of TLW1-09 sediment at 25-36 cm interval show oxidation …………..46
viii
LIST OF TABLES
Table Page
5.1. Description of dispersed organic matter identified in the four drill cores ….………19
5.2. Relative abundances (in percent) of dispersed organic matter in the four drillcores..21
5.3. Principal component loadings for the dataset of the four drill cores. ………………22
5.4. Palynomorph abundances ………………………….…………………………..…...36
6.1 Radiocarbon dating of shallow sediments from the three lakes……………....……..50
1. INTRODUCTION
Vast numbers of ephemeral hypersaline lakes prevail over much of the Australian landscape, where many of them exist in arid and semi arid regions (Van De Graaff et al.,
1977; Timms, 2005). These lakes align in chains following the traces of the paleodrainage systems or occupying the deepest depressions in the region (Van De Graaff et al., 1977). Commonly, they range in area and shape from small rounded to large elongated bodies with shallow water depths, even during flooding periods (Benison et al.,
2007). These ephemeral lakes have caught the attention of many researchers because of their origin, unique chemistry, sedimentary processes and biological components (De
Deckker, 1983; Pinder et al., 2002; Benison and Bowen, 2006; Bowen and Benison,
2009; Benson et al., 2007; Benison, 2008; Dickson and Giblin, 2008; Timms, 2005,
2009a, 2009b). The occurrence of these lakes appears to have been triggered by climatic change from humid to arid conditions, which resulted in the cessation of paleodrainage flow (Van De Graaff et al., 1977). Chemically, the salt lakes have a wide range of salinity and pH value as well as variation in mineral concentration.
The southwestern portion of the Yilgarn Craton in Western Australia is the focus of a multidisciplinary biogeochemical study of 10 coreholes drilled in seven hypersaline lakes or sites (Bowen et al., 2009; Benison et al., 2011). For the present study, four coreholes in three lakes south of Norseman, namely Gastropod Lake, Prado Lakes and
Twin Lake West (Figure 1.1), were studied for their palynofacies and palynomorph contents. Gastropod Lake is neutral-alkaline whereas the others are acidic. Published palynological studies are very few for the study area. Therefore, the objectives of this 2 study were to: (1) learn more about the lake history; (2) reconstruct the paleovegetation in study area; (3) detect the onset of salinity through palynological record; and (4) compare neutral-alkaline and acid lakes.
B
C
A D
Figure 1.1. A) Map of the study area in southern Western Australia; inset shows the map of Australia. B, C, D) Aerial views of corehole locations PL1-09 and PL2-09 (Prado Lake), TLW1-09 (Twin Lake West) and GLE1-09 (Gastropod Lake), respectively.
3
2. GEOLOGIC SETTING
2.1. INTRODUCTION
The Yilgarn Craton is one of the relict Archean blocks that constitute the western
Plateau of Australia and is located in the southwest corner of the continent. The craton extends over an area of approximately 657,000 Km2 and comprises Archean granitoid and greenstone rocks (Anand and Paine, 2002), which date back to 2,500 to 2,900 mya
(Morgan, 1993). These rocks enclose arched belts of metamorphosed sedimentary and volcanic rocks (Anand and Paine, 2002). The Precambrian rocks have been subjected to intensive weathering that has resulted in well-preserved regolith due to the stability of much of the continent during Phanerozoic (Anand, 2005). In some places, the weathering is as deep as 200 m, but the depth varies because of the variation in lithology, structure, land surface relief and the upper sediment during the weathering (Anand, 2005). Benison et al. (2007) reported the existence of regolith in and near some lakes at superficial depths
(0.5 m or less), where it blends with the overlain sediments. This makes it difficult to distinguish between the regolith and sedimentary rocks. Mesozoic and Cenozoic sedimentary rocks now cover both bedrocks and weathered rocks (Anand, 2005).
The most significant features in Yilgarn Craton are the chains of saline lakes that have occupied much of landscape. These lakes are believed to be remnants of the Yilgarn palaeodrainage system (Van De Graaff et al., 1977; Salama, 1994). The good preservation of the palaeodrainage is attributed mainly to the tectonic stability of the craton, in addition to the reduction in erosion due to climatic change from humid to arid during either the Eocene-Oligocene (Van De Graaff et al., 1977) or the Pliocene (Dodson and Macphail, 2004; Dodson and Lu, 2005). The time during which the palaeodrainage
4 started incising the craton is still debatable. According to De Graaff et al. (1977), the formation of the palaeodrainage probably happened during the Late Cretaceous to the early Paleogene, although in the Ponton Creek area (in the southeastern part of the craton) some patterns appear to have formed since the Permian. Clarke (1994b) estimated the age of the palaeodrainage to be as old as the Jurassic. However, other researchers favor Eocene times as the beginning of the palaeodrainage incision (e.g., Morgan 1993;
De Broekert and Sandiford, 2005). De Broekert and Sandiford (2005) ascribed the formation of the palaeodrainage to the uplifting of the Yilgarn Craton, which in turn reduced the geomorphic base level and increased the stream slope. Morgan (1993) referred the incision of the palaeodrainage to the erosion event in early Eocene times. In addition, he considered three contributory factors that initiated the incision as follows: (1) the shape of the craton land surface before the break up of Gondwana; (2) the break up of
Gondwana itself; and (3) the craton movement to the north after the breakup. The runoff in palaeodrainage ceased due to climatic change during Eocene to Oligocene (Van De
Graaff et al., 1977; Salama 1994).
2.2. STRATIGRAPHY
Cenozoic sediments ranging from continental to shallow marine filled the paleodrainage in the study area (Clarke, 1994b; De Broekert, 2005). Clarke (1993,
1994a, 1994b) described the lithostratigraphy of Lefroy and Cowan palaeodrainage sediments and proposed two successions: Eocene succession represented by the Eundynie
Group and post-Eocene succession represented by the Redmine Group (Figure 2.1). The
Eundynie Group in the Lefroy palaeodrainage consists of the Hampton Sandstone,
5
Pidinga Formation and Princess Royal Spongolite, while in the Cowan palaeodrainage, it comprises of the Werillup Formation, Norseman Limestone and Princess Royal
Spongolite. The Redmine Group includes the Revenge Formation, Gamma Island
Formation and Roysalt Formation in Lefroy palaeodrainage, while in the Cowan paleodrainage it comprises the Revenge Formation, Cowan Dolomite and Polar Bear
Formation. He also noted two major transgressions responsible for the deposition of the
Hampton Sandstone and Princess Royal Spongolite. The Tortachilla and Aldinge transgression occurred during mid-Eocene and late Eocene, respectively.
2.3. LAKE CHARACTERISTICS
The Australian ephemeral lakes vary considerably. Based on their morphological appearance, De Deckker (1983) categorized these lakes into four types: larger closed basin, small closed basin, crater lakes and coastal lakes. Larger closed basins are characterized by extensive internal drainage areas and are usually called playa lakes.
Small closed basins have small internal drainage areas and form under different conditions such deflation, while crater lakes have small, distinct internal catchments. The balance between precipitation and evaporation determines the salinity and lake level in these three lake types. Coastal lakes are those connected to the sea, and are not considered to be athalassohaline. In our study in southern Western Australia, large and small closed basin lakes are present. Benison et al. (2007) illustrated the general settings of these lakes (Figure 2.2).
6
!! Cowan Lefroy Palaeodrainage Palaeodrainage LithologyLLLLL! Epoch
Polar Bear Formation: sandy silts and Roysalt clays; bedded gypsum in silty matrix. Polar Bear Roysalt Formation: sandy silts, clays Formation Formation with gypsum crystals in silty carbonaceous and pyrite matrix Pliocene- Pliocene- Holocene Holocene
Cowan Gamma IS Revenge Formation: red brown silts, ferruginous fine sand Dolomite Formation Gamma IS FormationCR! : massive Revenge Group Redmine dolomite, dolomite carbonite mudstone, lenses of oolitic Oligocene - Miocene Princess Royal Spongolite Princess Royal Spongolite: siliceous sponge spicules, some silt and clay, SST Princess minor of quartz sand and glauconitic Norseman Royal peloids limestone Spongolite Werillup Formation: carbonaceous Werillup clays, silts, sand with lignite Late Eocene Eocene Late Formation
Hampton SS Pidinga Formation: red brown to Eundynie Group Eundynie green silts, white, gray or black clays Middle Middle Eocene and silts, and lignite ? Pidinga Formation Early Early Eocene Eocene
Mesozoic Rocks Mesozoic Mesozoic
Basement Rocks Pre- Cambrian Cambrian
Figure 2.1. Lithostratigraphy of Lefroy and Cowan Paleodrainages. Modified after Clarke (1993).
7
Figure 2.2. Geological settings of saline lakes in southern Western Australia. Top: closed basin lake types formed in fault block valleys. Bottom: A, B) Lakes on thin laterally discontinuous Cenozoic sediment. C) Lake situated directly on Archean bedrocks. D, E) Lakes hosted by loose sediment. Modified after Benison et al. (2007).
Another common variation among Australian ephemeral lakes is their water chemistry, which could be affected by the interaction between water and bedrocks.
Timms’s (2009a) study of the Esperance Hinterland salt lakes south of the study area showed that the lakes hosted by carbonate-rich sand tended to be alkaline whereas those in the north (close to the study area) lying on granite or sandstone were more acidic.
Based on pH values, Benison et al. (2007) classified the lakes in southwestern Australia into four categories: extremely acid (pH <4), moderately acid (pH = 4 to 6), neutral- alkaline lakes (pH = 6 to 8) and moderately alkaline (pH >8). The salinity of both lake water and groundwater range from freshwater (seldom) to saline water (>280 ppt)
(Bowen and Benison, 2009). The main brines in these waters range from Na-Cl to Na-
Mg-Cl-SO4 with changeable, regionally high amounts of Ca, K, Al, Fe, Si and Br
8
(Bowen and Benison, 2009). The acidity of groundwater appears to be constant while that of the lakes fluctuates due to surface processes (Bowen and Benison, 2009). Four major processes, namely flooding, evapoconcentration, desiccation and eolian erosion, govern the sedimentation in these lakes, with each process producing unique facies (Benison et al., 2007).
9
3. LITERATURE REVIEW
A great deal of interest has been placed on palynological studies of Paleogene,
Neogene and Quaternary sediments in Australia because they contain significant information about climatic and environmental fluctuations the continent has experienced.
However, a majority of these studies have focused on the eastern and southern parts of the continent (Dodson, 1977, 1983; Mildenhall and Crosbie, 1979; Luly, 1997; Harle,
1997; Field et al., 2002; McKenzie and Kershaw, 2004; Kershaw Van Der Kaars, 2007;
Kershaw et al., 2007; Fletcher and Thomas, 2007, 2010). Only limited palynological studies have been published on the Western Australia, and many of these have published information about the onset of aridity and salinity and their effects on vegetation during the Neogene. One of these studies conducted by Dodson and Ramrath (2001) on a
Cretaceous meteor crater at Yallalie in semiarid to subhumid southwest Western
Australia analyzed sediments that dated back to the upper Pliocene. This study was an integrated research that included the paleomagnetic record, sediment patterns, chemical analyses, and preliminary results from pollen, charcoal and diatom analyses. Dodson and
Ramrath (2001) found that the vegetation during this time interval was similar to the present-day vegetation. All the data obtained from this multidisciplinary study indicated that the Pliocene was not a period of regular cooling as previously thought but experienced episodes of climate variability.
Working on the same site Dodson and Macphail (2004) studied 110 m of late
Neogene lacustrine sediments. They were able to distinguish three distinct episodes of aridification around 2.90 Ma, 2.59 Ma and 2.56 Ma within and beyond the crater.
10
However, it is still unknown whether this climatic trend occurred in all middle latitude continents of the southern hemisphere. They concluded that the Pliocene was a warm epoch with gradual cooling trend towards the Quaternary.
Seeking more information on Pliocene climate, Dodson and Lu (2005) studied fossil pollen in conjunction with grain size analysis of sediments from the Yallalie Basin.
They were able to reconstruct the aridity and salinization history of the region between
2.63 and 2.56 Ma. Three distinctive episodes of aridity, around 2.59 Ma, 2.56 Ma and
2.558 Ma, were recognized based on the comparison of pollen abundances (decrease in humid woodland and increase in chenopod bush). Grain size analysis enabled them to defined short cycles of wetting and drying between 2.59 and 2.56 Ma, which correspond with sub-Milankovitch time scales.
As with the Pliocene, the climate during Holocene has also been debatable; it is not clear if it was wetter or drier than today’s climate. In order to assess paleoclimatic evidence for the Holocene, Newsome and Pickett (1992) studied two swamp sequences
(Boggy Lake and Loch McNess Swamp) in southwestern Western Australia. The results from their study did not support climatic change during the mid-Holocene; earlier studies reported that this interval was either wetter than the present-day conditions (Churchill,
1968) or experienced an arid phase (Semeniuk, 1986).
Other studies were focused on the types of vegetation in Western Australia. Van
Der Kaars and De Deckker (2003) utilized pollen assemblage distribution extracted from sediments offshore to define bioclimatic zones in the region. They identified five bioclimatic zones that they related to the rainfall seasonality, amount of rainfall, and vegetation distribution. These zones are: 1) the open Eucalyptus forest and woodland of
11 northern Western Australia (WA) with high summer rainfall; 2) the open Eucalyptus woodlands with Acacia and grassland of northwestern WA with lower summer rainfall;
3) the open Acacia shrubland with grasses and grasslands of northwestern WA with low summer rainfall; 4) the open Acacia shrubland of central WA with low summer and winter rainfall; and 5) the open Eucalyptus forest with mixed shrublands of southwestern
WA with low winter rainfall.
Newsome (1999) was more interested in the relationship between pollen and vegetation in southwestern Australia. He used pollen traps over two years in two regions to identify pollen assemblages and recorded vegetation types at each location. By using the statistical programs TWINSPAN and detrended correspondence analysis, he found moderately strong relationships between the pollen assemblages and vegetation.
Although some vegetation details were not represented in the pollen assemblages, he was able to recognize different vegetation types as follow: woodland sites in Kalgoorlie,
Acacia and mixed scrub sites, scrub-heath vegetation, thickets, and hummock grassland and Chenopod.
This present study documents the recovery of palynomorphs from the Revenge and Polar Bear formations. It should be noted that Clarke (1994) stated that no palynomorphs had been recovered from the Revenge Formation because of the oxidized nature of the sediments. In addition, this study provides evidences of reworking contrary to Bint (1981). Finally, it documents the presence of the salt tolerant alga Dunaliella and its usage as a salinity proxy.
12
4. METHODS
4.1. CORING
Four coreholes were drilled in three lakes as part of a drilling expedition by research team from Missouri University of Science and Technology (Missouri S&T),
Purdue University and Central Michigan University (CMU) (Figure 4.1). The coreholes were drilled at four sites as follow: on the shore of Gastropod Lake (GLE1-09;
33°4ʹ52.89ʺS, 121°41ʹ5.35ʺE), within Prado Lake (PL1-09; 32° 25ʹ 55.31ʺS, 121° 43ʹ
4.19ʺE), on the shore of Prado Lake (PL2-09; 32°25ʹ54.23ʺS, 121°43ʹ3.40ʺE), and within
Twin Lake West (TLW1-09; 33°3ʹ14.83ʺS, 121° 40ʹ 30.58ʺE). Shorelines were drilled either because of flooding in the lake (as in Twin Lake West and Gastropod Lake), or for comparison with corehole inside a dry lake (Prado Lake). Each corehole was labeled to reflect the locality, the number of the drillhole and the year of drilling (e.g. the code for
Prado Lake is PL, and the cores were labeled as PL1-09 and PL2-09). The approximate depths of the coreholes are 1 meter for TLW1-09, 13 meters for both GLE1-09 and PL2-
09, and 20 meters for PL1-09.
The coreholes were drilled by Boart Longyear’s semisonic drill Rig 1415 using the Rotosonic drilling technique (Figure 4.1; Benison et al. 2007). This technique minimized the dissolution of evaporite sediments and the possibility of contamination from drilling mud because it did not utilize fluids during drilling process. The cored sediments were briefly described in the field before transportation to the Joe Lord Core
Library at the Geological Survey of Western Australia in Kalgoorlie. Core sections were split into three parts, measured, digitally scanned, photographed and sampled for multiple
13 studies. Samples analyzed for accelerator mass spectroscopy (AMS) 14C dating and palynology were carefully selected from dark gray horizon suspected of having the most organic matter. One-third of each core is archived at the Core Library (Appendix A).
!" #"
$" %"
Figure 4.1. Rotosonic drill rig coring at the four sites studied. A) On the shore of Gastropod Lake (GLE1-09). B) Inside Prado Lake (PL1-09). C) On the shore of Prado Lake (PL2-09). D) On the shore of Twin Lake West (TLW1-09).
14
4.2. SAMPLE PROCESSING AND ANALYSES
Eleven samples were sent to the National Ocean Sciences AMS Facility at Woods
Hole Oceanographic Institution in Massachusetts for 14C dating; however, only four samples were datable. Fifty samples from the four coreholes (Appendix B) were processed using standard palynological techniques of digesting sediments in hydrochloric and hydrofluoric acids (Faegri and Iversen, 1989). Oxidation, sieving and heavy mineral separation were omitted for the residues used to prepare kerogen slides for palynofacies analyses (Lorente and Ran, 1991). Only 36 of the 50 samples produced enough residues for sieving and were used for detailed morphological analysis of palynomorphs. Two tablets of Lycopodium was added to the each sample prior to processing in order to quantify palynomorph abundance shifts (Stockmarr, 1971).
A Leica CME transmitted light microscope was used for routine identification, description and counting of the dispersed organic matter (DOM). Three hundred DOM particles were counted per slide at a magnification of 400x and converted to percentages to determine their relative abundances. A Nikon Eclipse 50i transmitted light microscope was used for identifying and counting palynomorphs in the sieved slides. The number of palynomorphs counted varied considerably because of poor recovery, except in four samples that yielded more than 200 specimens. A Nikon DS-Fi1 digital camera controlled by the software NIS-Elements D version 3.10 (SP3) attached to the Nikon
Eclipse microscope was used for photomicrography. Coordinates of specimens were recorded using an England Finder slide. Online databases were the main sources used to identify palynomorphs based on their morphological features (e.g. The Newcastle
Pollen Collection, 2005; Raine et al., 2011).
15
Distribution graphs of DOM and palynomorphs were plotted with the Tilia software, version 1.7.16 (Grimm, 1992). Multivariate statistical analyses (principal components analysis [PCA] and average linkage cluster analysis) programs written by
Kovach (2002) were preformed only for the DOM data due to the paucity of palynomorphs in many samples. PCA is useful in identifying the most statistically important DOM components. Minimum variance cluster analysis on a data matrix generated by Euclidean correlation coefficient was performed for palynofacies interpretation because it allowed DOM components with low percentage values to play a bigger role in grouping samples. Slides of all the samples used in this study are stored in the palynological collection in the Paleontology Laboratory at Missouri University of
Science and Technology.
16
5. RESULTS
5.1. LITHOLOGY
Lithologic information has been derived from brief descriptions of the cored sediments in the field and scanned cores (Figure 5.1). The four coreholes consist mainly of sandstone, clay, and sand mixed with clay, in addition thin layers of halite and gypsum. Regolith (weathered bedrock) is found at the base of each corehole. In some cases, such as GLE1-09, the regolith appeared to be intermixed with sediments, suggesting that sedimentation was contemporaneous with bedrock weathering. The sediments varied in color from yellowish, maroon, pale blue, pale brown to dark gray.
Some of these color variations are indicative of digenetic processes (Benison et al., 2011;
Story, 2012). Sediments penetrated by the four coreholes belong to the Revenge and
Polar Bear formations (Miocene to Holocene). Figure 5.2 shows the correlation between
PL1-09 and PL2-09.
5.2. DISPERSED ORGANIC MATTER
Three categories of dispersed organic matter representing eight types of components have been recognized following the classification of Oboh-Ikuenobe et al.
(2005). These components are comminuted phytoclasts, degraded phytoclasts, structured phytoclasts, opaques or black debris, amorphous organic matter, pollen and spores, fungal remains and algae (Table 5.1; Figure 5.3). The most abundant components are comminuted phytoclasts, followed by structured phytoclasts, degraded phytoclasts and
17 amorphous organic matter (Table 5.2). Principal components analysis confirms that these four components are the most statistically significant in the dataset (Table 5.3).
Thin layer of evaporite 0 m
Alternating beds of sand, clay and sandy
Lake clay
sediments Some nodules of iron
oxides and evaporite
Veins of OM
Sediment mixed with Transition zone bedrock materials
Regolith In situ weathered ∼1-20 m bedrock
Figure 5.1. Idealized lithologic column shows the main deposits occurring in the coreholes.
18
Sandstone Clay
Sandy- clay Clayey-sand Regolith Basement
Figure 5.2. Lithologic columns and scanned cores of some horizons in the Prado Lake coreholes PL1-09 (left) and PL2-09 (right). The red lines represent possible correlation between the lithologic units in the drill cores.
19
Table 5.1. Description of dispersed organic matter identified in the four drill cores.
Category Dispersed Organic Matter Descriptions Phytoclasts Structured phytoclasts Fragments derived from terrestrial plants with internal cellular structures or sharp outlines, such as cuticles and tracheids. They usually range in color from light to dark brown. Comminuted phytoclasts Fragmented plant remains occurring as small pieces <5µm. Degraded phytoclasts Highly degraded plant fragments without distinct cellular structure. Opaque Phytoclasts Oxidized or carbonized woody particulars Unstructured Amorphous organic matter Structureless organic material derived mainly organic matter from degradation of phytoplankton. They appear fluffy with colors ranging from colorless to pale brown. Palynomorphs Pollen and spores Palynomorph grains derived from terrestrial plants. Fungal remains Dark brown fungal spores, hyphae and fruiting bodies. Algae Salt tolerant algae with various sizes, possibly acidophilic.
The distribution graphs of the relative abundances of DOM in the corehole sediments (Figures 5.4.A, 5.4.B) reveal that comminuted phytoclasts are the most dominant components (counts up to 97%) except in GLE1-09 sediments, where they show a covariance with amorphous organic matter. The highest abundances of structured phytoclasts (19-47%) and degraded phytoclasts (14-34%) occur in TLW1-09. The preservation of structured phytoclasts appears to decrease with depth; cuticles and tracheid structures tend to be more abundant at shallow depths while massive phytoclasts that lack internal structures or cells increase with depth.
Opaques and palynomorphs (pollen and spores, fungal remains and algae) have the lowest percentages in all the kerogen samples. Although opaques are consistently present
(0-9%) in nearly all the sediments, they appear to be virtually absent in GLE1-09.
20
Figure 5.3. Photomicrographs of DOM in the four drill cores. See Table
5.2 for abbreviations.
21
Table 5.2. Relative abundances (in percent) of dispersed organic matter in four drill cores. STR = structured phytoclasts; COM = comminuted phytoclasts; DEG = degraded phytoclasts; OPQ = opaques; P&S = pollen and spores; FUG = fungal remains; ALG = algae; AOM – amorphous organic matter.
Corehole Slide Depth STR COM DEG OPQ P&S FUG ALG AOM Number (cm) PL1-09 83-1 11 23.00 15.00 2.33 0.67 4.33 6.33 0.67 47.67 84-1 61.5 3.00 95.00 0.67 0.00 0.00 0.00 0.67 0.67 85-1 111..5 33.00 37.33 18.00 0.00 0.00 0.33 0.00 11.33 86-1 178.5 1.00 92.67 0.33 0.00 0.00 0.00 3.33 2.67 89 438.5 15.67 67.00 6.67 0.00 0.00 0.3 0.00 10.33 90 488.5 3.33 87.00 4.33 1.00 0.00 0.00 0.00 4.00 91 571.5 27.00 59.67 7.67 0.33 0.00 0.00 0.00 5.33 94 701.5 3.33 89.00 2.00 5.67 0.00 0.00 0.00 0.00 95 758.5 2.33 95.33 0.67 1.67 0.00 0.00 0.00 0.00 96 806.5 5.33 88.67 3.67 2.33 0.00 0.00 0.00 0.00 97 941.5 4.33 87.33 1.00 3.00 0.00 0.00 0.67 3.67 98-1 990.5 2.00 97.67 0.33 0.00 0.00 0.00 0.00 0.00 99-1 1143.5 0.00 95.00 0.00 1.00 0.00 0.00 4.00 0.00 100 1211.5 2.00 86.00 3.00 5.67 0.00 0.00 1.00 2.33 101 1261.5 5.67 78.33 5.33 9.33 0.00 0.67 0.00 0.67 102 1311.5 6.33 31.33 11.67 4.67 0.00 0.00 0.00 46.00 103 1501.5 6.67 57.33 5.30 2.00 0.67 0.67 0.00 27.33 PL2-09 104 71.5 27.67 40.33 3.33 0.33 0.00 11.67 1.33 15.33 105 155 8.67 81.00 6.67 0.00 0.33 0.67 0.00 2.67 106 211.5 4.00 94.67 1.33 0.00 0.00 0.00 0.00 0.00 107 258.5 17.33 63.00 9.67 0.67 0.00 0.00 3.67 5.67 108 311.5 17.67 35.33 29.00 0.00 0.00 0.00 0.00 18.00 109 361.5 37.33 46.33 3.33 4.00 0.00 0.00 0.00 9.00 110 387.5 4.67 93.00 2.33 0.00 0.00 0.00 0.00 0.00 111 487.5 14.33 67.67 8.00 0.33 0.00 2.33 0.33 7.00 112 538.5 11.33 72.33 7.67 0.67 0.00 2.67 0.33 5.00 113 590.5 19.33 65.00 7.00 0.33 0.00 1.00 2.00 5.33 114 616.5 10.33 75.00 1.67 0.67 0.00 0.00 7.67 4.67 115 669 14.67 44.33 25.67 1.00 0.00 4.33 0.00 10.00 116 711.5 11.00 69.67 6.00 4.00 0.33 1.33 1.33 5.67 117 781.5 6.00 30.67 3.00 1.00 0.00 0.33 0.33 58.67 118 831.5 23.33 48.33 8.67 2.00 0.33 1.67 0.33 15.33 GLE1-09 119 41.5 35.00 51.33 4.00 0.00 0.33 0.33 0.00 9.00 120 81.5 4.67 92.00 3.00 0.00 0.00 0.33 0.00 0.00 121 121.5 7.33 84.00 6.33 0.00 0.00 1.67 0.00 0.00 122 171.5 5.00 81.00 1.67 0.00 0.00 0.00 2.67 9.67 123 212.5 1.33 93.00 1.00 1.33 0.00 0.00 0.67 2.67 124-1 271.5 22.33 30.33 5.33 0.00 0.00 0.00 0.67 41.33 125-1 351.5 6.00 22.33 1.33 0.00 0.00 0.00 0.00 70.00 126-1 401.5 3.33 18.33 3.00 0.00 0.00 0.33 0.00 75..33 127-1 451.5 1.33 52.00 1.67 0.33 0.00 0.00 0.67 44.00 128-1 521.5 6.00 18.00 2.67 0.00 0.00 0.00 3.33 70.00 129 581.5 9.67 8.33 6.33 0.00 0.67 0.00 0.00 75.00 130-1 701.5 3.33 27.67 1.67 0.00 0.33 0.00 0.33 66.67 131-1 1031.5 2.00 87.67 1.67 0.00 0,00 0.00 2.00 6.67 TLW1- 132-1 5 28.00 29.00 16.50 2.17 2.17 2.33 0.00 20.50 09 133-1 15 19.05 38.49 14.45 0.97 0.97 0.32 0.00 25.26 134-1 30 47.12 6.06 23.80 3.27 3.27 4.53 0.34 10.35 135-1 45 35.33 24.83 34.50 1.00 1.00 0.50 0.00 3.17 136-1 55 42.78 27.97 23.29 1.82 1.82 1.15 0.00 2.16
22
Table 5.3. Principal component loadings for the dataset of the four drill cores. The asterisk indicates absolute value > ± 0.1; Eigenvalues (Axis 1) = 1195.926 (76.370% of the total variance); Axis 2=326.445 (20.846%).
DOM Axis 1 Axis 2 Structured phytoclasts -0.145* -0.593* Comminuted phytoclasts 0.805* -0.325* Degraded phytoclasts -0.080 -.0328* Amorphous organic matter -0.570* 0.658*
However, palynomorphs are consistently present in TLW1-09 samples, but are absent in some PL1-09, PL2-09 and GLE1-09 samples. Among the four drill cores, GLE1-09 has the lowest relative abundance of palynomorphs. The common pollen families are
Myrtaceae, Poaceae, Chenopodiaceae and Asteraceae. In comparison with pollen and spores, fungal remains are more abundant, with the highest percentages (up to 11%) recorded at shallow depths in PL2-09.
Dunaliella, a salt tolerant alga, was identified in the four drill cores at depths ranging from 30 cm to 1211.5 cm. The relative abundances of Dunaliella vary in each drill core, with the highest percentage (7%) recorded in PL2-09 at 616.5 cm. Although
Dunaliella was found at 30 cm in TLW1-09, it appears to be absent in the upper 170 cm of GLE1-09. Specimens of the acidophobic gastropod Coxiella were found within
Gastropod Lake and along its shore, but are absent in the shallowest sample (40-43 cm) and at depths below. Any specimens that might have been present in the shallow sample was likely dissolved by hydrochloric acid during sample processing.
Average linkage cluster analysis was conducted for each individual drill core as well as for all the drill cores. Results for individual drill core datasets (see Appendix C) appear to be validated by those derived for the entire dataset shown in the dendrograms in
Figure 5.5. The top and left-hand dendrograms represent DOM components (R-mode),
23 and samples (Q-mode), respectively. The less abundant DOM components always cluster together. Similarly, the most significant DOM cluster together.
Three groups of samples, designated as palynofacies assemblages A, B, and C, have been identified. Palynofacies assemblage A is characterized by high percentages
(>78%) of comminuted phytoclasts. Moreover, the samples in this group have either the lowest relative abundances (<9%) of AOM, or lack AOM. The samples in this assemblage are mainly dominated by PL1-09 and GLE1-09, but few PL2-09 samples are present. Assemblage B samples have the highest percentages (41%-75%) of AOM and the lowest relative abundances (<35) of comminuted phytoclasts in the four drill cores.
This assemblage consists of seven GLE1-09 samples and one PL2-09 sample (Figure
5.5). An increase in structured phytoclasts as well as opaque, degraded phytoclasts and palynomorphs characterizes assemblage C. There are considerable variations in the
24
Figure 5.4. Distribution graphs of relative abundances of DOM in (a) PL1-09 (above) and PL2-09 (below).
25
Structured phytoclastsComminuted phytoclasts DegradedOpaque phytoclasts phytoclasts Pollen & Spores Fungal remains Algae AOM 50 100 150
200 250 300
350
400
450
500
550 Depth 600 650
700
750
800
850
900 950 1000
1050 20 40 20 40 60 80 100 0.4 0.8 1.2 1.6 0.4 0.8 0.9 2.1 0.9 2.1 3.0 20 40 60 80
Structured phytoclastsComminuted phytoclastsDegraded phytoclastsOpaque phytoclasts Pollen & Spores Fungal remains Algae AOM 5
10
15
20
25
30 Depth 35
40
45
50
55 20 40 20 40 20 40 2 3 6 2 3 2 3 6 0.3 20
Figure 5.4. (cont) Distribution graphs of relative abundances of DOM in (b) GLE1-09 (above) and TLW1-09 (below).
26 percentages of comminuted phytoclasts (31-75%) and AOM (1-47%), but unlike assemblage A, the latter is present in all the samples. This assemblage consists of all five
TLW1-09 samples, majority of the PL2-09 sample, few PL1-09 samples, and one GLE1-
09 sample (Figure 5.5).
A B C
Figure 5.5. Dendrograms for average linkage cluster analysis of the entire palynological samples from the four drill cores (Q–mode, left- hand side) and of dispersed organic matter (R-mode, top) with the data matrix displayed between them.
27
5.3. PALYNOMORPHS
Palynomorph counting revealed that reworked material was deposited in GLE1-
09 and PL1-09. Interestingly, this was not detected in the very short corehole TLW1-09, which is located closer to GLE1-09 (Figure 1.1). Both GLE1-09 and PL1-09 have poor recovery in comparison with TLW1-09. All three drill cores have a similar contemporaneous palynomorph assemblage (see below; Figures 5.6-5.11). PL2-09 samples were barren except at 71.5 cm and 311.5 cm, where very few grains were identified. The shallowest PL2-09 sample has considerable amounts of fungal remains
(up to 453; Table 5.4). In general, palynomorph preservation in the drill cores ranges from good to poor. Some specimens are highly degraded, fragmented and folded, especially in GLE1-09 and PL1-09.
5.3.1. GLE1-09 and PL1-09: Pollen and spore abundances in GLE1-09 samples range between 6 and 22 specimens, except in two samples at 401.5 cm and 701.5 cm with counts of 49 and 154, respectively. For PLI-09, a majority of the samples have total pollen and spore counts of 2 to 23; 67 and 66 specimens were counted in two samples located at 488.5 cm and 806.5 cm, respectively. Only three PLI-09 samples exceed 200 specimens. These samples are located at 11 cm, 111.5 cm and 571.5 cm in the corehole.
The distribution of pollen and spores in both lakes sediments does not appear to have been influenced by the type of sediments or location. The abundances of other palynomorphs (algae and fungal remains) appear to increase whenever pollen and spores increase (Table 5.4; Figure 5.12).
28
Palynomorphs referable to six pollen families, bisaccate pollen, several form- genera, spores, three types of algae, and one diatom group were identified, in addition to reworked taxa belonging to five fossil pollen genera, one spore genus, and two groups of algae. The pollen families are Poaceae, Chenopodiaceae, Myrtaceae, Asteraceae,
Casuarinaceae, and Haloragaceae (Figure 5.9-5.10). The contemporaneous bisaccates were indistinguishable. Form-generic taxa of unknown affinities were rare and have been grouped together as one category in the distribution charts illustrated in Figure 5.12. The reworked pollen specimens identified were attributed to Nothofagidites, Araucariacites,
Sparganiceaepollenites, Podocarpidites, and Aglaoreidia cyclops.
All the spores recovered are reworked. They are very few in both drill cores except in the samples that are characterized by higher recovery of palynomorphs. The spores are trilete and include Herkosporites elliottii and Cyathidites asper (Figure 5.6).
Two types of the salt-tolerant algal genus Dunaliella were identified, and confirmed by T. Lowenstein (March 2011, email communication) and M. Borowitzka
(July 2011, email communication). Dunaliella Type A occurs in PL1-09, while
Dunaliella Type B is found in GLE1-09. The differences between both types of
Dunaliella appear to be their color and sculpture. Type A is light brown with “bumpy” sculpture, whereas Type B is greenish and smoother (Figure 5.11). There are no obvious differences in their shapes. Spheroid palynomorphs of unknown affinity with faint yellow color that sometime makes them appear to be transparent are present. These specimens are few and occur in some samples. Two types of diatoms, one of which is identified as
Coscinodiscus hallettii, were found in GLE1-09. They are few and have been grouped together in Figure 5.12.
29
1 2 3
4 5 6
7 8 9
Figure 5.6. Photomicrographs of reworked trilete spores in GLE1-09 and
PL1-09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar is 10µm. 1. Gleicheniidites spp. (SN PL1-09/96; EF G22/4). 2. Psilatriletes sp. (SN PL1-09/85; EF V32/2). 3.
Cyathidites spp. (SN PL1-09/85; EF Q29/4). 4. Unidentified trilete spore
(SN PL1-09/96; EF F37/0). 5. Herkosporites elliottii Stover 1973 (SN PL1- 09/91; EF L21/4). 6. Selaginellidites sp. (SN PL1-09/93; EF Q37/3). 7. Unidentified trilete spore (PL1-09/85; T40/2). 8. Triletes fragilis Couper
1953 (SN GLE1-09/122; EF P13/3). 9. Cyathidites asper Mildenhall 1994
(SN PL1-09/91; EF F27/0).
30
1 2 3
4 5 6
7 8 9
Figure 5.7. Photomicrographs of reworked gymnosperms in GLE1-09 and PL1-09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar = 10µm. 1. Dacrydiumites praecupressinoides (Couper 1953) Truswell 1983 (SN GLE1-09/123; EF G18/2). 2. Podocarpidites sp. (SN PL1-09/85; EF S17/1). 3. Dacrycarpites australiensis Cookson & Pike 1953 (SN PL1-09/85; EF F19/0). 4. Parvisaccites? sp. (SN PL1-09/85; EF K40/0). 5. Araucariacites australis Cookson 1947 (SN PL1-09/91; EF H32/4). 6. Phyllocladidites mawsonii Cookson 1947 ex Couper 1953 (SN PL1-09/85; EF E40/3). 7. Phyllocladidites sp. (SN PL1-09/85; EF M26/0). 8. Trisaccate pollen (cf Microcachrydites antarcticus Cookson, 1947) (SN PL1-09/91; EF A32/3). 9. Podosporites erugatus Mildenhall 1978 (SN PL1-09/91; EF G26/3).
31
1 2 3
5 6 4
7 8 9
Figure 5.8. Photomicrographs of reworked angiosperms in GLE1-09 and PL1- 09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar = 10µm. 1. Nothofagidites vansteenisii (Cookson
1959) Stover & Evans 1973 (SN GLE1-09/128; EF J23/0). 2. Nothofagidites
sp (SN PL1-09/83; EF N35/0). 3. Nothofagidites Matauraensis? Couper 1953 Hekel 1972 (SN PL1-09/85; EF F41/2). 4. Proteacidites annularis Cookson 1950 (SN PL1-09/85; EF J34-3). 5. Crassus? (Proteacidites) Cookso, 1950
(SN PL1-09/91; EF N45/0). 6. Aglaoreidia cyclops Erdtman 1960 (SN PL1-
09/90; EF R23/0). 7. Sparganiceaepollenites sp. (SN PL1-09/85; EF R37/2). 8. Bombapollis sp. (SN PL1-09/85; EF H16/2). 9. Dicrassipollis sp. (SN PL1- 09/85; W32/2).
32
Reworked specimens of the freshwater-brackish water alga Botryococcus and several types of marine dinoflagellate cysts (dinocysts) are present in both coreholes. The former is more abundant. Identified dinocysts are Palaeohystrichophora infusorioides,
Homotryblium sp. and Odontochitina porifera (Figure 5.11).
Fungal remains are consistently present with variations in abundances. The highest numbers can be found in PL1-09 samples at 11 cm and 571.5 cm, which contain 494 and
266 specimens, respectively.
5.3.2. TLW1-09: Pollen and spore recovery in TLW1-09 samples was good except in one sample at 30 cm, where 36 specimens were counted (Table 5.4). The dominant pollen grains belong to Poaceae, Chenopodiaceae, Myrtaceae, and Asteraceae.
Casuarinaceae, Haloragaceae, Acacia (Fagaceae) and bisaccates are very few. There are several other rare pollen form genera that have been grouped together in Table 5.4.
Although some of the above families are present in GLE1-09 and PL1-09, their abundances are higher in TLW1-09, where some families have slightly different morphologies. For example, Poaceae pollen grains appear to be bigger. Clumping of
Asteraceae, Myrtaceae and Chenopodiaceae is common in all the samples but is absent in
GLE1-09 and PL1-09 samples. Few specimens (0.3%) of Dunaliella Type A are present in the kerogen samples but are absent in the sieved samples. The unknown palynomorph specimens found in the other drill cores are also present. Fungal remains are consistently present and vary between 10 and 338 in all TLW-1 samples. Unlike those in GLE1-09 and PL1-09 samples, these fungal remains are mostly hyphae and fruiting bodies (Figure
5.11).
33
1 2 3
4 5 6
7 8 9
10 11 12
Figure 5.9. Photomicrographs of contemporaneous pollen in GLE1-09, PL1-09 and TLW1-09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar =10µm.1. Myrtaceidites lipsis, Macphail & Truswell 1993 (SN PL1-09/83; EF M42/2). 2. Callistemon? sp. (Myrtaceae) (SN PL1-09/83; EF M40/3). 3. Eucalyptus sp. (SN TLW1-09/ 135; EF T34/2). 4. Glischocaryon? sp. (Haloragaceae) (SN GLE1-09/130; EF O44/2). 5. Myriophyllum? sp. (Haloragaceae) ( SN PL1-09/90; EF J33/2). 6. Asteraceae (SN PL1-09/83; EF P38/0). 7. Linguliflorae type (Asteraceae) (SN TLW1-09/133; EF Q45/1). 8. Chenopodiaceae (SN PL1-09/83; EF N30/2). 9. Acacia sp. (SN TLW1- 09/136; EF F31/2). 10. Gyrstemon (SN PL1-09/83; EF M39/4). 11. Casuarinaceae (SN PL1-09/83; EF L27/0). 12. Psilatriporites sp. (SN GLE1-09/123; EF P18/2).
34
1 2 3
4 5 6
7 8
Figure 5.10. Photomicrographs of contemporaneous pollen in GLE1-09, PL1-
09 and TLW1-09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar =10µm. 1. Poaceae (SN TLW1- 09/133; EF P41/2). 2,3. Rititricolporites sp. (Frankeniaceae?) (SN GLE1- 09/130; EF W27/1) (SN GLE1-09/130; EF F40/3). 4. Restionaceae (SN TLW1-09/132; EF S25/0). 5. Tricolpites sp (SN TLW1-09/136; EF O28/2). 6. Stephanoporites sp (SN TLW1-09/133; EF R39/0). 7. Brassicaceae (SN TLW1-09/132; EF U27/0). 8. Clumped pollen specimens.
35
1 2
3 4 5
6 7 8
9 10 11
Figure 5.11. Photomicrographs of selected algae and fungi in GLE1-09, PL1-09 and TLW1-09. Specimen names are followed by slide number (SN) and England Finder® coordinates (EF). Scale bar=10µm. 1. Odontochitina porifera Cookson 1956 (SN PL1-09/94; EF Q25/0). 2. Palaeohystrichophora infusorioides Deflandre,1935 (SN GLE1-09/126; EF Q40/1). 3.Unidentifed dinoflagellate cyst (SN PL1-09/84; EF K43/0). 4. Homotryblium sp. (SN GLE1-09/128; EF D28/0). 5. Unknown palynomorph (SN PL1-09/83; EF J29/1). 6. Coscinodiscus hallettii Fleming (Diatom) (SN GLE1-09/124; EF M21/2). 7. Botryococcus sp. (SN PL1- 09/85; EF N41/4). 8. Dunaliella Type A (SN PL1-09/86; EF N32/0). 9. Dunaliella Type B (SN GLE1-09/122 [Kerogen slide]; EF K22/4). 10. Fungal fruiting body (SN TLW1-09/136; EF N20/4). 11. Tetraploa sp. (Fungi) (SN PL1-09/90; EF J22/3).
36
Lycopodium 76 789 5568 2346 4734 8393 7494 5002 8409 7126 4902 10415 4731 2000 1126
Fungal remains Fungal
494 8 8 15 10 67 266 23 7 66 2 12 12 453 13
Total Palynomorph Total
535 19 340 108 12 73 300 27 9 74 2 17 27 6 4
Others
35 2 10 2 0 1 18 7 4 1 0 2 0
1 2 cysts Dinoflagellate
0 1 0 0 0 0 0 1 0 1 0 0 0 0 0
Botryococcus
0 0 108 0 2 13 31 2 0 7 0 0 0
0 0
Herkosporites
0 0 8 0 0 3 12 0 0 0 0 0 0
0 0
Spores
3 3 37 0 0 5 47 0 0 14 1 1 0
0 0
pollen Bisaccate
0 0 19 2 1 3 16 0 0 4 0 1 0
0 0
Araucariacites
1 0 11 0 0 0 27 0 0 6 0 0 0
0 0
.
yclops c Aglaoreidia
09 0 0 5 0 0 4 10 1 0 2 0 0 0
-
0 0
Reworked Palynomorphs Reworked
Sparganiceaepollenites
09 09
- - 0 0 11 0 0 5 13 1 0 3 0 0 0
0 0
Nothofagidites PL1
PL2
4 0 95 1 7 26 87 2 1 21 0 1 5
0 0
alynomorph p Unknown 09 and PL209 and
-
10 0 1 0 0 0 0 0 0 0 0 3 0 3 0
A Type Dunaliella
PL1
0 0 0 93 0 0 3 0 0 0 0 2 15 0 0
(a)
Psilatriporates
0 0 1 2 1 0 0 1 2 0 0 5 0 1 1
in
s pollen Bisaccate
2 1 0 0 0 0 0 0 0 0 0 0 0 0 0
Haloragaceae
1 0 0 0 1 1 2 1 0 0 0 0 0 0 0
Casuarinaceae
98 3 14 1 0 5 29 3 0 7 0 0 2 0 1 abundance
Asteraceae
55 2 2 1 0 0 0 1 0 1 0 0 0 0 0
Palynomorphs oraneous
Myrtaceae
247 3 5 4 0 0 0 2 1 1 0 1 4 0 0
Chenopodiaceae
Contemp
55 0 1 2 0 2 0 2 0 2 0 1 1 1 0
Poaceae Poaceae
24 4 12 0 0 5 5 3 1 4 1 0 0 0 0
(cm) Depth able Palynomorphable 5.4. 1.5 T 11 61.5 11 178.5 438.5 488.5 571.5 701.5 758.5 806.5 941.5 990.5 1143.5 71.5 311.5
! ! !
37
Lycopodium
1951 2628 7919 4817 4217 5757 8029 7331 8270 8778 4408 2289
remains Fungal 1 5 5 1 2 8 2 19 13 13 18 27
tal Palynomorph tal To 7 10 15 33 39 61 41 61 24 47 12
168
R Others 1 0 2 3 1 3 4 4 2 0 0
13
cysts Dinoflagellate
0 0 1 0 0 0 1 2 1 0 0 0
Botryococcus
0 0 0 2 6 0 5 0 1 0 0 0
Spores Spores
0 0 3 0 0 0 7 0 0 0 0 0
Bisaccate pollen pollen Bisaccate
0 0 0 1 0 0 5 0 2 0 0 0
Sparganiceaepollenites
0 0 0 0 0 0 1 0 2 0 1 0
Nothofagidites Reworked Palynomorphs Reworked 0 0 7 1 1 1 3 0 1 0 11 10
09 Diatom
-
0 0 1 0 6 7 0 6 1 0 0 2
Unknown Palynomorph Unknown
0 0 0 0 2 0 0 2 0 0 0 0 09. GLE1 -
B Type Dunaliella
0 0 9 8 0 0 0
28 41 24 21 13
Psilatriporates
0 0 2 2 2 2 2 0 0 0 0 3 (b) GLE1
in
Retitricolpates s 0 0 0 0 0 0 0 0 0 0 0 36
Haloragaceae 0 0 0 0 0 0 0 0 0 0 0 60
abundance
Casuarinaceae
1 3 0 0 0 0 3 3 3 3 2 0
Asteraceae 0 1 0 0 0 0 1 0 2 0 7 0
Myrtaceae 5 6 0 0 0 1 5 0 0 0 2 22
Palynomorphs Contemporaneous
Chenopodiaceae
1 0 3 2 1 1 3 1 2 1 1
10
Poaceae
2 5 5 0 1 2 5 3 0 3 3 4
(cm) Depth 1.5 able (cont)Palynomorphable 5.4. 41.5 121.5 171.5 212.5 27 351.5 401.5 451.5 521.5 581.5 701.5 1031.5 T
! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! 38
Lycopodium 534 1596 4311 315 173
remains Fungal 163 76 10 167 338
Total
261 281 38 243 258
Others
15 10 1 3 15
Palynomorph
Unknown
17 10 2 3 0
Gyrostemon
3 5 0 4 5
Acacia
1 1 0 1 3
09
pollen - Bisaccate 09.
- 0 0 2 1 0
Restionaceae TLW1
6 0 0 0 0
(c) TLW1 (c)
Haloragaceae
in
2 3 0 1 0
s
eae Casuarinac
16 19 0 3 6
Palynomorphs Contemporaneous
abundance
Asteraceae
18 16 5 31 47
Myrtaceae
76 76 4 22 31
Chenopodiaceae
39 70 3 62 64
Poaceae
68 71 21 112 87
(cm) Depth
5 15 30 45 55 5.4.(cont)PalynomorphTable ! ! ! ! ! !
39
PoaceaeChenopodiaceaeMyrtaceae AsteraceaeCasuarinaceaeHaloragaceae Retitricolpites PsilatriporatesDunaliella Type B UnknownDiatom PalynomorphNothofagiditesSparganiceaepollenitesBisaccateSpores pollenBotryococcusDinoflagellateOthers cysts Fungal remainsLycopodium 50 100 150 200 250 300 350 400 450 500 550 Depth 600 650 700 750 800 850 900 950 1000 1050 10 10 30 10 10 30 60 20 40 5 50 10 10 20 10 10 10 10 10 20 30 5000 10000
Poaceae Chenopodiaceae Myrtaceae Asteraceae CasuarinaceaeHaloragaceaeAcaciaBisaccateGyrostemon pollenRestionaceaeOthers UnknownFungal palynomorph spores Lycopodium 5
10
15
20
25
30 Depth
35
40
45
50
55 50 125 35 70 40 80 25 50 20 10 10 10 10 10 20 20 200 400 2500 5000 Figure 5.12. Palynomorph abundance distribution graphs in (a) GLE1-09 (Top) and TLW1-09 (Bottom).
40
12000
6000 Lycopodium
500
250 Fungal remains Fungal
40
Others Dinoflagellate cysts Dinoflagellate 5
150 Botryococcus
20 Herkosporites 09. -
50 Spores
20 pollen Bisaccates s in (b) PL1 (b) in s 30
Araucariacites
cyclops Aglaoreidia 10 20
Sparganiceaepollenites
100
50
distribution graph distribution Nothofagidites
Palynomorph Unknow 10
100
50 A Type Dunaliella
5 Psilatriporites
pollen Bisaccates 5 5
Haloragaceae
100
50 Casuarinaceae
60
30 Asteraceae
abundance Palynomorph (cont) 5.12. ure 300
Fig
150
Myrtaceae
60
30 Chenopodiaceae
25
Poaceae 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950
1000 1050 1100 1150 Depth
41
6. DISCUSSION
6.1. LAKE DYNAMICS AND PALEOENVIRONMENTS
Lakes are very dynamic environments that are easily affected by changes in climate, tectonism and surrounding environments (Rosen, 1994; Cohen, 2003; Prothero and Schwab, 2004). Thus, sediments and evidences of life preserved in lakes reflect these factors. Tectonism affects their sizes, shapes, and locations such as documented for the study area in Figure 2.2. Gastropod Lake and Prado Lake sit on Cenozoic sediments, while Twin Lake West rests directly on bedrock. The four major processes of flooding, evapoconcentration, desiccation, and eolian erosion and deposition in present-day southern Western Australia (Benison et al., 2007) result in very dynamic and evolving lake conditions. These processes occur at different scales (temporal and spatial) during the year or even in one day. For example, Lake Aerodrome located about 25 kilometers north of the study area experienced all four stages in 24 hours on 19/20 January 2009 (C.
Sanchez Botero, personal communication, June 2012). The processes affect water level and chemistry (pH, salinity), lithofacies, fossils and DOM; sediments in the lake are reworked by eolian erosion. It is likely that sediments in the four studied coreholes reflect the consequences of these lake processes over time.
The lithologic columns of PL1-09 and PL2-09 in Figure 5.5 show some degree of correlation and facies change between sediments in coreholes that are only meters apart.
The lithified sandstone upon which PL2-09 was drilled (see Figure 5.2) is missing in
PL1-09. This sandstone appears to be modern sand that has undergone rapid cementation
(K. Benison, personal communication, June 2012) and is contemporaneous with the salt
42 crust and underlying clay and clayey sand drilled by PL1-09 inside the lake. In the two
Prado coreholes and GLE-09, sand content appears to increase with depth.
Several studies have noted good correlation between palynofacies assemblages and lithology (e.g., Baird, 1992; Oboh-Ikuenobe, 1992; Oboh-Ikuenobe et al., 1997).
Other studies such as Gadel and Texier (1986) did not show distinct correlation. In the study there is no apparent correlation probably because of the dynamic nature of the lakes
(Sanchez Botero et al., 2011). Since changing lake processes affect hydrologic and sedimentologic conditions even in different parts of a lake, variations can be expected in the distribution of organic matter. It is possible for a lake to experience more than one process at the same time. For example, during the desiccation stage, the lake may not dry up completely, and the center will still have some water. However, other parts of the lake may experience evapoconcentration and eolian erosion and reworking of the sediments at the edges. Thus, evaporite minerals will eventually precipitate in the lake center, while the lake edges will deposit clastic sediments. Such a scenario can promote the settling and better preservation of DOM below the salt crust, while OM on the shore or edges may experience oxidation and subarial erosion. This scenario appears to have occurred in
Prado Lake and its shore as recorded by the differences in DOM distribution and lithology.
Apparent lack of correlation between palynofacies and lithology notwithstanding, paleoenvironmental inferences can be deduced from the three palynofacies assemblages
(Figure 5.5). Overall, all three assemblages indicate very strong terrestrial influence and deposition near parent floras as reflected in the high percentages of phytoclasts (Tyson,
1995). The high relative abundances of comminuted phytoclasts may be attributed to
43 reworking of lake sediment that broke down the DOM. The higher percentages of AOM in assemblage B are likely indicative of high nutrient production and productivity at the time of deposition (Traverse, 2007). Assemblage C recorded increases in palynomorphs and structured phytoclasts, suggesting better preservation in those samples.
6.2. PALYNOFLORAS
Palynomorphs identified in Gastropod Lake and Prado Lake revealed two different vegetation communities (see section 5.3.1): contemporaneous palynomorphs
(identified mainly to paleobotanical family level) representing the actual surrounding vegetation at the time of deposition, and reworked palynomorph representing older vegetation that were recycled and mixed with contemporaneous palynomorphs. Climatic preferences and depositional environments were the criteria used for distinguishing between both palynomorph groups.
The contemporaneous palynomorphs such as Myrtaceae and Poaceae are generally more commonly associated with warm, arid climate, while others such as
Chenopodiaceae and Dunaliella are salt tolerant (Guma et al., 2010; Lowenstein, 2011).
In addition, Asteraceae can proliferate in environmentally stressed condition (Vivar-
Evans et al., 2006). These plant families still flourish in southern Western Australia today which experiences Mediterranean climate-type (hot dry summer and mild wet winter)
(Salama, 1994; Martin, 2006). The reworked palynomorphs represent swampy communities that prevailed in South Australia and southern Western Australia during the early Paleogene period when the climate was humid and seasonal rainfall was high
(Stover and Partridge, 1981; Macphail et al., 1994). Presently, these conditions are
44 restricted to the eastern part of the continent. The reworked palynomorphs are characteristic of the palynofloras of the upper Eocene Werillup Formation (Stover and
Partridge, 1982; Sanchez Botero et al., 2011). Bint (1981) recorded elements of Eocene rainforest (Nothofagidites and Podocarpidites) in Pliocene sediments from Lake Tay located southwest of Norseman but did not consider them to be reworked. He suggested that the climate was wetter and that these taxa persisted and survived in refuge at high land until at least the early Pliocene. However, the recovery of Botryococcus and dinoflagellate cysts, especially Odontochitina porifera that are believed to be Cretaceous
(Oboh-Ikuenobe et al., 2012) and reworked in Eocene sediments, supports the idea of reworking. Moreover, the presence of the pollen Aglaoreidia cyclops recorded in
Werillup Formation and also found in upper Eocene-lower Oligocene freshwater deposits in Europe and North America (Sanchez Botero et al., 2011) supports reworking.
It appears that woodland communities (tree taxa, mainly Myrtaceae and
Casuarinaceae) and a healthy understory represented by a variety of shrubs and grasses contributed palynomorphs to the lakes. Most taxa recovered are angiosperms; gymnosperms (Pinus) are rare and spores are absent. The scarcity of the contemporaneous pollen and spores, and to some extent, the high abundances of reworked palynomorphs may be attributed to different factors: 1) the source areas were far away from the depositional sites (lakes); 2) low productivity of parent plants coinciding with relatively high amounts of reworked palynomorphs may have diluted the contemporary grains (Tyson, 2005); and 3) predominance of oxidizing or alternating dry and wet conditions.
45
During dry periods the water in the lakes evaporates and eventually result in desiccation, which in turn promotes eolian erosion and reworking of lakes sediment.
Oxidation also increases during this dry period. As a result of desiccation and oxidation palynomorphs with low sporopollenin contents can be easily destroyed (Traverse, 2007), resulting in their low abundances in the sediment. It is noteworthy to mention that dry periods may also promote an increase in deposition of palynomorphs by wind. During wet periods, palynomorph quantities may increase as a result of runoff that contributes a variety of palynomorphs (both contemporaneous and reworked) into the lakes and cause flooding. Based on these scenarios, it appears that both lakes were mostly dry with some periods of flooding represented by increases in palynomorphs.
The lack of robust data from GLE1-09 and PL1-09 makes it hard to detect any pattern in pollen distribution that may be related to local or regional climatic change. A notable exception is the presence of taxa that were present only at 701.5 cm in GLE1-09, where Haloragaceae and Retitricolpites sp. (Frankeniaceae?) dominate the assemblage.
This may be indicative of local change in vegetation, although this change was not likely related to climatic shift because both plant families grow in arid climate.
Palynological data from the very short (~1 m) TLW1-09 corehole indicate that palynofloras surrounding did not differ much from those around GLE1-09 and PL1-09.
Woodland communities represented by mainly Myrtaceae, followed by Casuarinaceae and to lesser extent Acacia prevailed with grass and shrub canopy. Other palynofloras that were present but represented by very few pollen specimens were Fabaceae,
Brassicaceae, Restionaceae and Gyrstemon; Restionaceae was identified only at 5 cm depth (Figure 5.10). The high relative abundances of pollen and clumping of specimens
46 prevalent in the samples indicate that the source areas for the plants are very close to the lake. It appears that palynomorph preservation was good except at 30 cm depth, which shows evidence of oxidation (Figure 6.1). All five TLW1-09 samples suggest that wet conditions likely occurred periodically during sedimentation in the lake, but the environment did not promote the growth pteridophyte and bryophyte plants near the lake.
This may explain why contemporaneous fern spores are absent in all three lakes.
It is unusual to recover microorganisms with inorganic walls (silica or calcite) in palynological residues because of the acid digestion processing techniques. It is, however, possible for such microfossils to survive during sample preparation if they were trapped in AOM or their wall compositions were replaced by other minerals such as pyrite (Batten, 1996). A few specimens of diatoms were recovered in GLE1-09.
Figure 6.1. Core scans of TLW1-09 sediment at 25-36 cm interval show oxidation (reddish color).
47
6.3. PALYNOSTRATIGRAPHY
The contemporaneous pollen assemblage identified in this study comprises
Asteraceae, Myrtaceae, Chenopodiaceae, Poaceae, Haloragaceae, Acacia, etc., which are characterized by long age ranges. As a result, it is difficult to determine an exact age for the sediments in our coreholes. Prior to the Oligocene-Miocene, palynomorphs of swampy and forest origins, such as Aglaoreidia cyclops and Nothofagidites were common in southern Western Australian environments (Macphail, 1994; Martin, 2006;
Sanchez Botero, 2011). Onset of aridity changed the landscape and resulted in more open vegetation occupied by shrubs, herbs and more open woodland plants (Dodson and
Macphail, 2004); our contemporaneous pollen assemblage typifies this more open vegetation.
It appears that our coreholes drilled through the Polar Bear Formation (earliest
Pliocene-Holocene) and Revenge Formation (Miocene), based on Clarke’s (1993, 1994b) descriptions of the Cowan and Lefroy palaeodrainage sediments, and recent study of a
Lake Aerodrome corehole 24 kilometers north of Prado Lake by Story (2012). Our sediments correspond to mineralogical units LA6-LA9 of Story (2012). Palynological data suggest that TLW1-09 drilled through only the Polar Bear Formation.
6.4. DUNALIELLA AS A SALINITY PROXY
Dunaliella is a unicellular organism that is considered to be the most halotolerant alga. It is known to adapt to a variety of salt environments varying from as low as 0.1M to 5.5M of salt (Seckbach, 1999). It is also the primary producer in hypersaline environments (Lowenstein et al., 2011). Because of its incredible adaptation to harsh
48 environments and its commercial value (harvesting for beta carotene), it is of great interest to many researchers (Garcia et al., 2007; Chen and Jiang, 2009). It is not surprising to find Dunaliella in modern southern Western Australian lakes. Timms (2009) identified this alga in the Esperance Hinterland lakes in water samples obtained in 2007.
Specimens of Dunaliella are present in our drill cores, in both un-sieved kerogen and sieved samples. They vary in numbers, and have variable morphologies and two different colors (Section 5.3). Variations in morphology are aided by the nature of the cell and response to the environment (Seckbach, 1999). Instead of a rigid polysaccharide cell wall, a thin plasma membrane covered by mucus surface coat encloses the organism, that can result in easy changes in morphology. Therefore, the absence of a rigid cell wall allows rapid changes in cell volume as a response to extracellular change in osmotic pressure. The orange and green colors of ancient Dunaliella result from good preservation of pigments such as carotenoids and chlorophyll (Lowenstein et al., 2011).
Dunaliella with orange color (that accumulates large amounts of β-carotene [such as that found in PL1-09, PL2-09 and TLW1-09]) tolerates more light intensity than that with green color (in GLE1-09) (Oren, 2009). The amount of irradiance received during cell division cycle, nutrient limitation or supraoptimal salt concentration determine the amount of β-carotene in Dunaliella (Oren, 2009).
Dunaliella can be used as salinity indicator since it thrives in waters with a wide range of salinity. In the four coreholes it has been recovered in many samples straddling various depths but not at above 170 cm in GLE1-09 and below 1,211 cm in PL1-09. It is reasonable to presume that its first record in the drill cores suggests the onset of salinity in the study area. Increases in their relative abundances may be indicative of periods of
49 blooms related to favorable water chemistry and high water levels (e.g., at 178.5 cm in
PL1-09 and at 271.5 cm in GLE1-09). Oren et al. (2009) performed simulation experiments to determine the factors that promote blooms of Dunaliella and halophilic
Archaea in the Dead Sea. They found that during dilution of Dead Sea water by Red Sea water and addition of phosphate, Dunaliella showed some development and its growth increased as the concentration of phosphate increased and salinity decreased.
6.5. NEUTRAL-ALKALINE VS. ACID LAKES
Comparison between one neutral-alkaline lake (Gastropod Lake) and two acid lakes (Prado Lake and Twin Lake West) revealed one major difference. Dunaliella is absent in samples from the shallowest depths in GLE1-09 whereas it is present in the shallow acid lake samples. This absence coincides with the presence of the acidophobic gastropod Coxiella. Since gastropods are known to prey on algae (Williams and Mellor,
1991) it is possible that Coxiella preyed upon Dunaliella and eventually exhausted all the specimens in the lake. Moreover, the fact that Dunaliella lacks rigid cell wall makes it desirable food for other organisms because it is easy to digest (Brock, 1975). If the species of Dunaliella recovered is acidophilic, then it could be absent from this lake today. The presence of Dunaliella below 170 cm in Gastropod Lake suggests a transition from acid to neutral-alkaline conditions.
50
6.6. EVIDENCES OF REWORKING
This section focuses on the confirmation of reworking by radiocarbon dating from shallow sediments. Four samples, one each from GLE1-09 and PL1-09 and two from
TLW1-09, were dated (Table 6.1). The two TLW1-09 dates revealed an age inconsistency. The age obtained for the sediment at 45 cm depth (1310 ±55 years BP) is older than that at 55 cm depth (190 ±25 years BP). Palynomorph data from GLE1-09 and
PL1-09 confirmed this inconsistency because reworked taxa the Werillup Formation
(sourced by outcrops in the region) were recovered with contemporaneous palynomorphs.
The reworked specimens occurred in a majority of the samples, and even from the shallowest depth (11 cm in PL1-09; see Table 5.4). Thus, it appears that the process of reworking has been a part of the lake history and continuous even today, as discussed in section 6.1.
Table 6.1 Radiocarbon dating of shallow sediments from the three lakes
Core number Depth interval (cm) Dating age in years Error in years
GLE1-09-02-001 170-173 32600 1400
PL1-09-01-001 10-12 1600 35
TLW1-09-002 40-50 1310 55
TLW1-09-003 51-59 190 25
51
7. CONCLUSION
Palynological analysis of samples obtained from three ephemeral hypersaline lakes in southern Western Australia, two of which are acid lakes (Prado lake and Twin
Lake West) and one is neutral-alkaline lake (Gastropod Lake), provide insightful and new information on lake history. This study has documented the unequivocal presence of palynomorphs in the Revenge Formation contrary to previous studies noting otherwise.
Major findings include:
1. Palynofacies analysis revealed that comminuted phytoclasts are the main DOM in
the four coreholes. However the relative distributions of DOM differ between the
lake and in coreholes drilled a few meters apart.
2. The differences in DOM distribution and lack of correlation between palynofacies
assemblages and lithology are attributed to the processes of lakes dynamics,
namely flooding, desiccation, evapoconcentration, and reworking and eolian
erosion. Those processes occur at different temporal and spatial scales.
3. The probability of a lake experiencing more than one process at same time is very
high; each process will affect the nature and abundance of different DOM
components as well as lithology.
4. Palynomorph recovery was very poor in Gastropod Lake and Prado Lake except
in certain depths, while it was good in Twin Lake West.
5. Open woodland community with shrubs and herbs canopy has been prevalent in
the study area since the Miocene.
52
6. The presence of swampy rainforest pollen types along with the arid pollen types is
an indication of reworking. The reworked pollen taxa are sourced by the upper
Eocene Werillup formation assemblage.
7. Dunaliella is a salt tolerant alga that is found in the four drill cores, and its first
record is likely an indication of salinity onset.
8. The absence of Dunaliella from the uppermost sediments of GLE1-09 may be
related to either predation by the acidophobic gastropod Coxiella, which is found
in the lake and along the shoreline, or to the fact that this Dunaliella species is
acidophilic. Either scenario suggests that Gastropod Lake has become neutral-
alkaline in modern times.
9. The inconsistencies of radiocarbon dating and the long ranges of all pollen
families identified made it difficult to constrain the age of the sediments.
However; based on other studies that focused on lithology and mineralogy, it
appears that Gastropod Lake and Prado Lake sediments have age duration from
the Miocene to Holocene (Revenge and Polar Bear formations) while Twin Lake
west sediments are confined to Polar Bear Formation.
APPENDIX A: PHOTOGRAPHS OF DRILL CORE TRAYS
54
GLE1-09 core trays; arrow = 10 cm.
55
PL1-09 core trays; arrow = 10 cm.
56
PL2-09 core trays; arrow = 10 cm.
57
TLW1-09 core trays; arrow = 10 cm.
APPENDIX B: SAMPLE INVENTORY AND QUANTITATIVE PALYNOLOGICAL
RECORD
59
Table A.1. Sample inventory showing palynomorph recovery and lithology.
Coreholes Slide # Depth Recovery Lithology (cm) PL1-09 83 11 Good Wet greenish clay 84 61.5 Poor White clayey sand light brown (creamy) 85 111..5 Poor Clayey sand, Pale brown with maroon bands and Iron nodules 86 178.5 Poor White clay stained with red 89 438.5 Poor Pale blue clay 90 488.5 Poor Pale blue sand 91 571.5 Poor Earthy sand with Iron nodular 94 701.5 Poor White, earthy Sand with Iron nodular 95 758.5 Poor Earthy fine sand 96 806.5 Poor Pale pink coarse sand with maroon bands 97 941.5 Poor Bands of white maroon fine sand 98 990.5 Poor White fine sand with pale maroon bands 99 1143.5 Poor Earthy fine sand 100 1211.5 Poor Dark gray sand 101 1261.5 Poor Coarse bronzy sand 102 1311.5 Poor Coarse bronzy sand 103 1501.5 Poor Dark yellow sand PL2-09 104 71.5 Poor Pale yellow fine sand mixed with coarse 105 155 Poor White, maroon clay with Iron nodular 106 211.5 Poor White, maroon clay 107 258.5 Poor Coarse pinkish sand 108 311.5 Poor Pale yellow sandy clay 109 361.5 Poor Pale blue sandy clay stained with brown 110 387.5 Poor Pale yellow sandy clay stained with brown 111 487.5 Poor White sand stained with yellow 112 538.5 Poor Pale yellow sandy clay 113 590.5 Poor Coarse yellowish sand with maroon and brown bands 114 616.5 Poor Bronzy coarse sand 115 669 Poor Bronzy coarse sand 116 711.5 Poor Bronzy coarse sand 117 781.5 Poor Bronzy coarse sand 118 831.5 Poor Bronzy coarse sand GLE1-09 119 41.5 Poor Coarse sand, earthy white with Iron nodular 120 81.5 Poor Fine reddish sand 121 121.5 Poor Coarse reddish sand 122 171.5 Poor Greyish fine sand mixed with coarse 123 212.5 Poor Fine pale brown sand, veins of OM 124 271.5 Poor Massive coarse pale brown sand 125 351.5 Poor Greenish coarse sand 126 401.5 Poor Pale brown sand with carbonized materials 127 451.5 Poor Pale brown sand with layers of carbonized materials 128 521.5 Poor Pale brown sand 129 581.5 Poor Pale brown, greenish sand with carbonized materials 130 701.5 Poor Pale brown fine sand 131 1031.5 Poor Greenish sand with carbonized materials TLW-09 132-1 5 Good Fine sand, pale reddish brown 133-1 15 Poor Fine sand, pale reddish brown 134-1 30 Poor Oxidized sand , reddish 135-1 45 Good Coarse sand with reworked materials 136-1 55 Good Coarse sand with reworked materials
60
Table A.2. Quantitative palynological record for three drill cores analyzed. Grains per gram of dry sediment were calculated using the equation: ((palynomorphs counted / Lycopodium counted)* Lycopodium added)/ starting weight.
Coreholes Slide # Depth Starting Palynomorphs Lycopodium Lycopodium Grains per (cm) weight (g) counted counted added Gram Dry Sed. PL1-09 83 11 37.0 535 76 25084 4772.4 84 61.5 37.8 19 789 25084 16 85 111..5 39.4 340 5568 25084 38.9 86 178.5 40.0 108 2346 25084 28.9 89 438.5 39.6 12 4734 25084 1.61 90 488.5 37.0 73 8393 25084 5.9 91 571.5 37.2 300 7494 25084 27 94 701.5 37.9 27 5002 25084 3.6 95 758.5 39.2 9 8409 25084 0.69 96 806.5 38.4 74 7126 25084 6.8 97 941.5 40.0 2 4902 25084 0.26 98 990.5 38.3 17 10415 25084 1.07 99 1143.5 37.1 27 4731 25084 3.9 GLE1-09 119 41.5 39.4 10 1951 21358 2.8 121 121.5 40 15 2628 21358 3.05 122 171.5 39.4 33 7919 21358 2.3 123 212.5 35 39 4873 21358 4.9 124 271.5 38.9 61 4217 21358 7.9 125 351.5 39.5 41 5757 21358 3.9 126 401.5 39.8 61 8029 21358 4.08 127 451.5 39.2 24 7331 21358 1.8 128 521.5 39.2 47 8270 21358 3.1 129 581.5 39.4 7 8778 21358 0.43 130 701.5 39.2 168 4408 21358 20.7 131 1031.5 39.8 12 2289 21358 2.8 TLW-09 132-1 5 30.8 261 534 21358 339 133-1 15 39.6 281 1596 21358 95 134-1 30 39.6 38 4311 21358 4.6 135-1 45 39.5 243 315 21358 417.12 136-1 55 39.0 258 173 21358 817
APPINDIX C: AVERAGE LINKAGE CLUSTER ANALYSIS
FOR EACH INDIVIDUAL DRILL CORE
62
A: Top: GLE1-09; Bottom: TLW1-09
A B
C
63
Top: PL1-09; Bottom: PL2-09
A C
A C
Squared Euclidean-Data log(2) transformed
64
BIBLIOGRAPHY
Anand, R.R., and Paine, M., 2002. Regolith geology of the Yilgarn Craton, Western Australia: implications for exploration. Australia Journal of Earth Sciences, vol. 49, p. 3-162.
Anand, R.R., 2005. Weathering History, landscape evolution and implications for exploration, in Anand, R. R. and De Broekert, P., regolith landscape evolution across Australia — a compilation of regolith landscape case studies with regolith landscape evolution models. Cooperative Research Centre for Landscape Environments and Mineral Exploration; CRC LEME, p. 2–40.
Baird, J.G., 1992. Palynofacies of the eastern margin of the Gippsland Basin. Gippsland Basin Symposium. Melbourne, 22/23 June 1992, p. 25-42.
Batten, D.J.,1996. Palynofacies and paleoenvironmental interpretation, in Jansonius, J and McGregor, D.C., (eds), Palynology : Principles and Applications. American Association of Stratigraphic Palynologists Foundation, vol. 3, p. 1011-1064.
Bint, A.N., 1981. An Early Pliocene pollen assemblage from Lake Tay, South- western Australia, and its phytogeographic implication. Australian Journal of Botany, vol. 29, p. 287-291.
Benison, K.C., and Bowen, B. B., 2006. Acid saline lake systems give clues about past environments and the search for life on Mars. Icarus, vol. 183, p. 225-229.
Benison, K.C., Bowen, B.B., Oboh-Ikuenobe, F.E., Jagniecki, E.A., Laclair, D.A., Story, S.L., Mormile, M.R., and Hong, B.-Y., 2007. Sedimentology of acid saline lakes in Southern western Australia: newly described processes and products of an extreme environment. Journal of Sedimentology Research, vol. 77, p. 366-388.
Benison, K.C., 2008. Life and death around acid-saline lakes. Palaios, vol. 23, p. 571- 573.
Benison, K.C., Bowen, B.B., Haagsma, A.J., Oboh-Ikuenobe, F.E., Sanchez Botero, C., and Story, S., 2011. Multiple paleoclimate proxies from Eocene – Holocene lake, eolian, and paleosol facies in Western Australian cores: Preliminary results. Geological Society of America Annual Meeting. Abstracts with Programs, paper No. 172-5.
Bowen, B. B., and Benison, K. C., 2009. Geochemical characteristics of naturally acid and alkaline saline lakes in southern Western Australia. Applied Geochemistry, vol. 24, p. 268-284.
65
Bowen, B.B., Benison, K., Oboh-Ikuenobe, F.E., Sanchez Botero, C., and Story, S., 2009. Preliminary analyses of new acid saline lake cores in Western Australia: sedimentological, palynological, mineralogical, and geochemical analysis of spatial and temporal environmental changes in extreme environments. Geological Society of America Annual Meeting, Abstracts with Programs, paper No. 198-1.
Brock. T.D., 1975. Salinity and the ecology of Dunaliella from Great Salt Lake. Journal of General Microbiology, vol.89, p. 285-292.
Chen, H., and Jiang, J-G., 2009. Osmotic responses of Dunaliella to the changes of salinity. Journal of Cellular Physiology, vol. 219, p. 251-258.
Churchill, D.M.,1968. The distribution and prehistory of Eucalyptus diversicolor F. Muell., E. marginata Donn ex Sm., and E. calophylla R. Br, in relation to rainfall. Australia Journal of Botany, vol. 16, p. 125-151.
Clarke, J.D.A., 1993. Stratigraphy of the Lefroy and Cowan Palaeodrainges, Western Australia. Journal of the Royal Society of Western Australia, vol. 76, p. 13-23.
Clarke, J.D.A., 1994a. Evolution of the Lefroy and Cowan palaeodrainage channels, Western Australia. Australian Journal of Earth Sciences, vol. 41, p. 55-68.
Clarke, J.D.A., 1994b. Lake Lefroy, a palaeodrainage playa in Western Australia. Australian Journal of Earth Sciences, vol.41, p. 417-427.
Cohen, A.S., 2003. Paleolimnology: The History and Evolution of Lake Systems. Oxford University Press, Oxford, 525 p.
De Broekert, P., and Sandiford, M., 2005. Buried Inset-Valleys in the Eastern Yilgarn Craton, Western Australia: geomorphology, age, and allogenic control. The Journal of Geology, vol. 113, p. 471-493.
De Deckker, P., 1983. Australian salt lakes: their history, chemistry, and biota-a review. Hydrobiologia, vol. 105, p. 231-244.
Dickson, B.L., and Giblin, A.M., 2009. Features of acid-saline systems of Southern Australia. Applied Geochemistry, vol. 24, p. 297-302.
Dodson, J.R., 1977. Late Quaternary palaeoecology of Wyrie Swamp, southeastern South Australia. Quaternary Research, vol. 8, p. 97-114.
Dodson, J.R., 1983. Modern pollen rain in southeastern New South Wales, Australia. Review of Palaeobotany and Palynology, vol. 38, p. 249-268.
Dodson, J. R., and Ramrath, A., 2001. An Upper Pliocene lacustrine environmental record from south-Western Australia-preliminary results. Palaeogeography,
66
Palaeoclimatology, Palaeoecology, vol. 167, p. 309-320.
Dodson, J.R., and Macphail, M.K., 2004. Palynological evidence for aridity events and vegetation change during the Middle Pliocene, a warm period in Southwestern Australia. Global and Planetary Change, vol. 41, p. 285-307.
Dodson, J. R., and Lu, H., 2005. Salinity episodes and their reversal in the late Pliocene of south Western Australia. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 228, p. 296–304.
Faegri, K., and Iverson, J., 1989, Textbook of Pollen Analysis, 4th ed., Blackwell Scientific Publicatons, Oxford, 340 p.
Field, J.H., Dodson, J.R., and Prosser, I.P., 2002. A Late Pleistocene vegetation history from the Australian semi-arid zone. Quaternary Science Reviews, vol. 21, p. 1023-1037.
Fletcher, S.M., and Thomas, I., 2007. Modern pollen–vegetation relationships in western Tasmania, Australia. Review of Palaeobotany and Palynology, vol. 146, p. 146 – 168.
Fletcher, S.M., and Thomas, I., 2010. A quantitative Late Quaternary temperature reconstruction from western Tasmania, Australia. Quaternary Science Reviews, vol. 29, p. 2351-2361.
Gadel, F., and Texier, H., 1986. Distribution and nature of organic matter in recent sediments of Lake Nokoué, Benin (West Africa). Estuarine, Coastal and Shelf Science, vol. 22, Issue. 6, p. 767-784.
Garcia, F., Freile-Pelegrin, Y., and Robledo, D., 2007. Physiological characterization of Dunaliella sp. (Chlorophyta, Volvocales) from Yucatan, Mexico. Bioresourse Technology , vol. 98. Issue. 7, p 1359-1365.
Grimm, E.C. 1992. Tilia and Tilia-graph: pollen spreadsheet and graphics programs. Program and Abstracts, 8th International Palynological Congress, Aix-en- Provence [France], September 6-12, 1992, p. 56.
Guma, I.L., Padrón-Mederos, M.A., Santos-Guerra, A, and Reyes- Betancort, J.A. 2010. Effect of temperature and salinity on germination of Salaola vermiculata (Chenopodiaceae) from Canary Island. Journal of Arid Environments, vol. 74, p. 708-711.
Harle, K. J., 1997. Late Quaternary vegetation and climate change in southeastern Australia: palynological evidence from marine core E55-6. Palaeogeography, Palaeoclimatology, Palaeoecology, vol.131, p. 465-483.
67
Kershaw, A.P., Bretherton, S.C., and Van De Kaars, S., 2007. A complete pollen record of the last 230 ka from Lynch's Crater, northeastern Australia. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 251, p. 23-45.
Kershaw, A.P., and Van Der Kaars, S., 2007. Pollen records, Late Pleistocene, Australia and New Zealand. Encyclopedia of Quaternary, p. 2613-2623.
Kovach, W.L., 2002, Multivariate Statistical Package Plus, Versions 3.0 and 3.1, User’s Manual, Kovach Computing Services, Pentraeth, Wales, U.K., 127p.
Lorente, M.A., and Ran, E.T.H., Eds., 1991, Open workshop on organic matter classification: Hugo De Vries-Laboratory, University of Amsterdam, Special Issue, 72 p.
Lowenstein, T. K., Schubert, B. A., and Timofeeff, M. N., 2011. Microbial communites in fluid inclusions and long- term survival in halite. GSA Today, vol. 21, No. 1, p. 4-9.
Luly, J.G., 1997. Modern pollen dynamics and surficial sedimentary processes at Lake Tyrrell, semi-arid northwestern Victoria, Australia. Review of Palaeobotanyand Palynology, vol. 97, p. 301-318.
Macphail, M.K., Alley, N.F., Truswell, E.M., and Sluiter, I.R.K., 1994. Early Tertiary vegetation: evidence from spores and pollen, in Hill, R. S, ed., History of the Australian Vegetation: Cretaceous to Recent. Cambridge University Press, Cambridge, UK., p.189-261.
Martin, H.A., 2006. Cenozoic climate change and the development of the arid vegetation in Australia. Journal of Arid Environment, vol. 66, p. 533-563.
McKenzie, G.M., and Kershaw, P.A., 2004. A Holocene pollen record from cool temperate rainforest, Aire Crossing, the Otway region of Victoria, Australia. Review of Palaeobotany and Palynology, vol. 132, p. 281-290.
Mildenhall, D.C., and Crosbie, Y.M., 1979. Some porate pollen from upper Tertiary of New Zealand. New Zealand Journal of Geology and Geophysics, vol. 22, No. 4, p. 499-508
Morgan, K.M., 1993. Development, sedimentation and economic potential of palaeoriver systems of the Yilgarn Craton of Western Australia. Sedimentary Geology, vol. 85, p. 637-656.
New Castle pollen collection, 2005. http://www.aqua.org.au/AQUA/Pollen/.
Newsome, J.C., 1999. Pollen–vegetation relationships in semi-arid southwestern Australia. Review of Palaeobotany and Palynology, vol. 106, p. 103–119.
68
Newsome, J.C., and Pickett, E.J., 1992. Palynology and palaeoclimtic implication of two Holocene sequences from southwestern Australia. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 101, p. 245-261.
Oboh-Ikuenobe, F.E., 1992. Multivariate statistical analysis of palynofacies from the middle Miocene of the Niger Delta and their environmental significance. PALAIOS, vol. 7, p. 559-573.
Oboh-Ikuenobe, F.E., Yepes, O., and ODP Leg Scientific Party., 1997. Palynofacies analysis of sediments from the Côte d’Ivoire-Ghana transform margin: preliminary correlation with some regional events in the Equatorial Atlantic. Palaeogeography, Palaeoclimatology, Palaeoecology, vol.129, p. 291-314.
Oboh-Ikuenobe, F.E., Obi, C.G., and Jaramillo, C.A., 2005. Lithofacies, palynofacies, and sequence stratigraphy of Palaeogene strata in Southeastern Nigeria. Journal of Africa Earth Sciences, vol. 41, p. 79-102.
Oboh-Ikuenobe, F.E., Spencer, M.K., Campbell, C.E., and Haselwander. R.D., 2012. A portrait of Late Maastrichtian and Paleocene palynoflora and paleoenvironment in the northern Mississippi Embayment, southeastern Missouri. Palynology, vol. 36, p. 63-79.
Oren, A., 2009. Microbial Diversity and Microbial Abundance in Salt-Saturated Brines: Why are the Waters of Hypersaline Lakes Red?. Natural Resources and Environmental Issues, vol. XV, p. 247-255.
Oren, A., Gavrieli, J., Kohen, M., Lati, J., Aharoni, M., and Gavrieli, I., 2009. Long-term Mesocosm Simulation of Algal and Archaeal Blooms in the Dead Sea Following Dilution with Red Sea Water. Natural Resources and Environmental Issues, vol. XV, p. 145-151.
Pinder, A.M., Halse, S.A., Shiel, R.J., Cale, D.J., and McRae, J.M., 2002. Halophile aquatic invertebrates in the wheatbelt region of southwestern Australia. Verhandlungen der Internationalen Vereinigung Für Theoretische und Angewandte Limnologie, vol. 28, p.1687-1694.
Prothero, D.R., and Schwab, F., 2003. Sedimentary Geology: An Introduction to Sedimentary Rocks and Stratigraphy, 2nd Edition. W. H. Freeman and Company, New York, USA, 600 p.
Raine, J.I., Mildenhall, D.C., Kennedy, E.M., 2011. New Zealand fossil spores and pollen: an illustrated catalogue. 4th edition. GNS Science Miscellaneous Series N° 4. http://data.gns.cri.nz/sporepollen/index.htm.
Rosen, M.R., 1994. The importance of groundwater in playas: A review of playa classifications and the sedimentology and hydrology of playas, in Rosen, M.R.,
69
Paleoclimate and Basin Evolution of Playa Systems: Geological Society of America Special Paper 289, p.1-18.
Salama, R.B., 1994. The evolution of saline lakes in the relict drainage of the Yilgarn River, Western Australia, in Renaut, R., and Last, W., (eds)., Sedimentology and Geochemistry of Modern and Ancient Saline Lakes. SEPM Special Publication No. 50, p. 189-199.
Sanchez Botero, C.A., Oboh-Ikuenobe, F.E., Benison, K.C., Bowen, B.B., and Story, S. L., 2011. Dispersed organic matter in two lake brown cores, western Australia: do they reflect changes in lithology. Geological Society of America Annual Meeting, Abstracts with Programs, Paper No. 120-11.
Seckbach, J.ed.,1999. Enigmatic Microorganisms and Life in Extreme Environments. Kluwer Academic Publishers, Netherlands, 687p.
Semeniuk, V., 1986. Holocene climate history of coastal south western Australia using calcrete as an indicator. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 53, p. 289-308.
Stockmarr, J., 1971. Tablets with spores used in absolute pollen analysis. Pollen et Spores, vol. XIII, N°. 4, p. 615-621.
Story, S. (2012). Mineralogy of acid saline lake systems in southern Western Australia, (Unpublished doctoral dissertation). Purdue University, West Lafayette, Indiana, USA.
Stover, L.E., and Partridge, A.D., 1981. Eocene spore-pollen from the Werillup Formation, Western Australia. Palynology, vol. 6, p. 69-96.
Timms, B.V., 2005. Salt lakes in Australia: present problems and prognosis for the future. Hydrobiologia, vol. 552, p. 1-15.
Timms, B.V., 2009a. Study of the saline lakes of Esperance Hinterland, Western Australia, with special reference to the roles of acidity and episodicity. Natural Resources and Environmental Issues, vol. 15, p. 215-224.
Timms, B.V., 2009b. A study of the salt lakes and salt springs of Eyre Peninsula, South Australia. Hydrobiologia, vol. 626, p. 41-51.
Traverse, A., 2007. Paleopalynology, 2nd Edition, Springer , Dordrecht, Netherlands, 813 p.
Tyson, R.V., 1995. Organic facies and palynofacies, Chapman and Hall, London, 615 p.
70
Van De Graaff, W.J.E., Crowe, R.W.A., Bunting, J.A., and Jackson, M.J., 1977. Relict early Cainozoic drainages in arid Western Australia, Zeitschrift für Geomorphologie, vol. 21, p. 379-400.
Van Der Kaars, S., and De Deckker, P., 2003. Pollen distribution in marine surface sediments offshore Western Australia. Review of Palaeobotany and Palynology, vol. 124, p. 113-129.
Vivar-Evans, S., Barradas, V.L., Sánchez-Coronado, M.E., De Buen, A.G., and Orozco- Segovia, A., 2006. Ecophysiology of seed germination of wild Dahlia coccinea (Asteraceae) in a spatially heterogeneous fire-prone habitat. Acta Oecologica, vol. 29, p. 187-195.
Williams, W.D., and Mellor, M.W., 1991. Ecology of Coxiella ( Mollusca, Gastropoda, Prosobranchia), a snail endemic to Australian salt lakes. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 84, p. 339-355.
INTERNET REFERENCE:
Internet reference 1: http://apsa.anu.edu.au/
71
VITA
Lutfia Grabel was born in Al- Zawiyah City, Libya. She received her Bachelor of
Science degree in Geology in 2002 from the Geology Department of Seventh of April
University (now Al-Zawiyah University). In July 2010, she started her graduate study at
Missouri University of Science and Technology. She earned her Master of Science degree in Geology and Geophysics (emphasis: Palynology) in August 2012 from the
Department of Geological Sciences and Engineering, Missouri University of Science and
Technology, Rolla, Missouri, U.S.A.