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2002 Alluvial, aeolian and lacustrine evidence for climatic and flow regime changes over the past 250 ka, Cooper Creek near Innamincka, South Australia Maria Coleman University of Wollongong
Recommended Citation Coleman, Maria, Alluvial, aeolian and lacustrine evidence for climatic and flow regime changes over the past 250 ka, Cooper Creek near Innamincka, South Australia, Doctor of Philosophy thesis, School of Geosciences, University of Wollongong, 2002. http://ro.uow.edu.au/theses/1963
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ALLUVIAL, AEOLIAN AND LACUSTRINE EVIDENCE FOR CLIMATIC AND FLOW REGIME CHANGES OVER THE PAST 250 KA, COOPER CREEK NEAR INNAMINCKA, SOUTH AUSTRALIA
A thesis submitted in fulfilment of the requirements
for the award of the degree
DOCTOR OF PHILOSOPHY
from
UNIVERSITY OF WOLLONGONG
by
Maria Coleman
BEnvSc(Hons), MSc(Hons)
School of Geosciences
2002 i
DEDICATION
Moje roditeli su dosli u Australia bez nista i ostavili su meni puno. Bez nji nebi imala priliku da radim ovaj doctorat i da imam ovaj zivot ovdi. Moj otac je uvjek kazo kad sam dila mala da cu bit doktor. Moja mama opet je uvjek mi kazala da radim sta volim samo da budem zadovoljna sa zivot. Ovaj doctorat je za moj pokonji otac, Gabriel Halili, i pokonja mama, Manda Halili. Volim vas obadvojme jako puno sa sve moj srce. Hvala. DECLARATION
I declare that this thesis is a report of research work carried out by me and has not been submitted in any form for a higher degree at any other university. Information obtained from the published or unpublished work of others has been acknowledged.
Maria Coleman
2002 iii
ABSTRACT
Cooper Creek at Innamincka in South Australia is one of very few places where evidence of palaeoclimatic history from the Quaternary Period is preserved in at least three stratigraphic settings; fluvial, aeolian and lacustrine. The significance of this study location is enhancedfirstly because here this semi-arid to arid partly tropical catchment has a drainage area of nearly 237 000 km2 and therefore constitutes a very significant portion of the 1.3 million km2 Lake Eyre basin, Australia's largest dryland drainage system. Secondly, and very unusually for such a large river system, the flow of the Cooper at Innamincka bifurcates; north to Coongie Lakes, west towards Lake Eyre, and south down Strzelecki Creek and into the Lake Frome basin.
This study attempts to reconstruct the palaeoenvironmental Quaternary history of a complex system of dividing drainage. Sixty nine thermoluminescence dates and numerous stratigraphic and sedimentological analyses, including particle size, mineral content, and petrographic and scanning electron microscopy, reveal interacting depositional conditions in alluvial (channel and overbank), aeolian (source-bordering and longitudinal dune) and lacustrine (lunette) environments, information that provides an improved understanding of Australian Quaternary climatic and flow-regime changes in central Australia. These results point to a progressive but probably oscillating drying trend on Cooper Creek during the Mid to Late Quaternary. The oldest dated alluvium near Innamincka suggests extensive fluvial activity at about 250 ka to 230 ka (OI Stages 7/8), some of it well away from the existing channel. In agreement with work done by others further upstream on Cooper Creek, there appears after this to have been a period of reduced fluvial activity until extensive channels operated again along both Cooper and Strzelecki Creeks during the middle of OI Stage 6. This was followed by another probable hiatus until OI Stage 5 when significant fluvial activity was this time associated with the development of source-bordering dunes adjacent to palaeochannels on Cooper Creek, and with the formation lunettes in the Coongie Lakes region. Pronounced fluvial activity appears to have continued through to OI Stage 4, ceasing at locations other than near the existing channel of Cooper Creek by about 60 ka to 52 ka. While Cooper Creek had sufficient power to continue to iv
slowly migrate in the vicinity of its present channel from about 55 ka until the LGM, the region was clearly significantly drier and less fluvially active from early OI Stage 3 to the present.
Source-bordering dunes dating at 40 ka to 25 ka do not correspond to older adjacent palaeochannels on Cooper Creek (the youngest dating at -52 ka) and therefore suggest substantial aeolian reworking in OI Stages 3 and 2. Cooper Creek beyond the Innamincka Dome ceased to transport any significant sand at around the LGM. Only within the flow-confining and thereby stream-power amplifying effect of the Dome is there evidence on Cooper Creek of a final period of enhanced fluvial activity in the Early to Mid Holocene. However, it appears that Strzelecki Creek remained fluvially active even after the LGM, transporting clean channel sands at 15 ka to 10 ka.
The accumulated dune ages from this study indicate a pronounced period of aeolian activity from the LGM to the present, initially with the reworking of existing source-bordering dunes but then, particularly during the Holocene, with the extension northwards of derivative longitudinal dunes. There appears to have been two stages of longitudinal dune formation in the Strzelecki dunefield: 16 ka to 9 ka and 5 ka to 1 ka, probably signifying two periods of local dryness and windiness. Lacustrine lunettes were reworked from older lunettes in the Coongie Lakes region during the Holocene providing further evidence for the region as a whole becoming drier. Cooper Creek and Strzelecki Creek near Innamincka became a low-energy largely mud-transporting system from the Mid Holocene, vastly different to their Mid to Late Pleistocene precursors. V
ACKNOWLEDGMENTS
Many people have assisted in the preparation of this thesis with helpful discussion, criticism, assistance and support, without whom this thesis would not have been possible. These include:
Professor Gerald Nanson (University of Wollongong) for his critical comments of drafts, encouragement, guidance, digging the Tilcha Waterhole section 'in his younger years' and providing me with a scholarship from his research grant.
Associate Professor Brian Jones (University of Wollongong) for helping me out with fieldwork, laboratory work, editing and critical feedback on sedimentological work.
David Price (University of Wollongong) for conducting all those TL dates and reminding me that I have beaten the postgraduate TL record at the University. Also, special thanks to Jose Abrantes for his assistance with the TL dating, encouragement and friendship through both good and difficult times.
Santos (Moomba) Ltd for allowing me the use of their facilities while conducting fieldwork.
Allan Mauger (Mines and Energy South Australia) for the remote sensing images used in this thesis.
Greg Campbell (Landcare Manager, Kidman and Company) for his friendly advice and access to Kidman property.
Graham and Marie Morton from Innamincka Homestead, Pam Reik from Merty Merty Homestead and Mick Brazel from Gidgealpa Homestead, thankyou for allowing access to your properties, advice and hospitality.
Department of Environment and Natural Resources Port Augusta for allowing me to conduct work in National Parks areas.
David Carrie (University of Wollongong) for preparing thin sections and conducting the X-ray diffraction.
Many thanks goes to my field assistants and friends including: Roger Callen, David Kennedy, Terrence Coleman, Geoff Black, Jerry Maroulis, Jenny Atchinson, John Leake, Stephen Tooth, Lynne McCarthy, Sue and Paul Brown, Tim Cohen, Sue Murray, Sue Fyfe, Rachel Nanson, Tim Pietch and Ingrid Wotton.
Finally, and by no means least, I wish to thank my mother Manda Halili and husband Terrence Coleman for their unconditional support, encouragement and love since I started university. I will always be in your debt. vi
TABLE OF CONTENTS
DEDICATION I
DECLARATION D
ABSTRACT m
ACKNOWLEDGMENTS V
TABLE OF CONTENTS VI
LIST OF TABLES X
LIST OF FIGURES XI
CHAPTER 1 INTRODUCTION 1 1.1 CONTEXT OF THESIS 1 1.1.1 Quaternary Palaeoenvironmental Reconstruction of the Australian Arid-Zone 1 1.1.2 Lake Eyre Basin 6 1.2 AIMS 7 1.3 THESIS OUTLINE 8 CHAPTER 2 GEOLOGICAL EVOLUTION AND PHYSIOGRAPHY OF THE LAKE EYRE DRAINAGE BASIN 9 2.1 INTRODUCTION 9 2.2 GOELOGICAL EVOLUTION 9 2.2.1 Warburton Basin (Early Palaeozoic) 9 2.2.2 Cooper, Pedirka and Simpson Basins (Carboniferous-Triassic) 12 2.2.3 Eromanga Basin (Early Jurassic-Late Cretaceous) 15 2.2.4 Stratigraphy of the Lake Eyre Basin 17 2.2.4.1 Phase 1: Late Paleocene to Middle Eocene 20 2.2.4.2 Phase 2: Late Oligocene? to Early Miocene 21 2.2.4.3 Phase 3: Pliocene? to Quaternary 22 2.3 REGIONAL SETTING OF THE STUDY AREA 25 2.3.1 Cooper Creek and Strzelecki Creek 25 2.3.2 Innamincka Dome and Cooper Creek 'Fan' 26 2.3.3 The Gibber Plains 27 2.3.4 Simpson/Strzelecki Dunefield 28 2.3.4.1 Morphology, Sedimentology, Chronology and Provenance of the Dunefield 28 2.3.5 Coongie Lakes 35 2.4 CLIMATE 38 2.5 HYDROLOGY 44 2.6 VEGETATION 48 2.7 SOITS 49 vii
CHAPTER 3 A REVIEW OF QUATERNARY CLIMATIC OSCILLATIONS WITH SPECIFIC REFERENCE TO AUSTRALIAN QUATERNARY TERRESTRIAL RECORDS 51 3.1 INTRODUCTION 51 3.2 GROWTH OF ANTARCTIC ICECAP AND DECLINING TEMPERATURE 54 3.3 CLIMATIC EVENTS FROM THE CHINESE LOESS DEPOSITS, NORTH ATLANTIC SEDIMENTS AND ICE CORES FROM GREENLAND AND ANTARCTICA 56 3.4 MIDDLE TO LATE QUATERNARY RECORD FOR AUSTRALIA 61 3.4.1 Tropical Northern Australia 62 3.4.2 Central Australia 65 3.4.2.1 Fluvial and Lacustrine Evidence 65 3.4.2.2 Aeolian Evidence 70 3.4.3 Southeastern Australia 71 3.5 CONCLUSION 75 CHAPTER 4 METHODS 77 4.1 SITE SELECTION AND SAMPLE COLLECTION PROCEDURE 77 4.2 THERMOLUMINESCENCE (TL) DATING 78 4.2.1 Summary of the TL Dating Technique 79 4.3 PARTICLE SIZE ANALYSIS 81 4.4 SCANNING ELECTRON MICROSCOPE (SEM) 82 4.5 X-RAY DIFFRECTTON AND MINERALOGY 82 CHAPTER 5 DIFFERENTIATING MAJOR DEPOSITIONAL ENVIRONMENTS USING SEDIMENT CHARACTERISTICS 84 5.1 INTRODUCTION 84 5.2 GRAIN-SIZE PARAMETERS OF ALLUVIAL SEDIMENTS 85 5.2.1 Lower Palaeochannel Sediments 86 5.2.2 Upper Palaeochannel Sediments 87 5.2.3 Overbank Deposits 88 5.2.4 Sand-Sized Clay Aggregates 88 5.3 GRAIN-SIZE PARAMETERS OF SOURCE-BORDERING DUNES 89 5.3.1 Source-Bordering Dune Sediments 89 5.4 GRAIN-SIZE PARAMETERS OF AEOLIAN DUNES 90 5.4.1 Dune Surface Sediments 91 5.4.2 Diagenetically Altered Dune Sediments 92 5.5 GRAIN-SIZE PARAMETERS OF LUNETTE 94 5.6 TWO-TAILED T-TEST 94 5.7 SEDIMENT COLOUR 97 5.8 MINERALOGICAL COMPOSITION 98 5.8.1 Clay Mineralogy (Standard X-Ray Diffraction Analyses) 98 5.8.2 Petrographic Interpretation 99 5.8.3 Cluster Analysis 103 5.9 SEM ANALYSIS OF QUARTZ GRAIN SURFACE FEATURES 105 5.9.1 V-Shaped Etching 106 5.9.2 Abrasion and Roundness 107 5.10 CONCLUSION 109 viii
CHAPTER 6 STRATIGRAPHIC INTERPRETATIONS AND THERMOLUMINESCENCE CHRONOLOGY OF ALLUVIAL, AEOLIAN AND LACUSTRINE SEDIMENTS 113 6.1 INTRODUCTION 113 6.2 STRATIGRAPHIC AND SEDIMENTARY FACIES DESCRIPTIONS AND INTERPRETATIONS 113 6.2.1 Coongie Lakes 113 6.2.1.1 Lake Marroocutchanie Lunette 114 6.2.1.2 Coongie Longitudinal Dune 118 6.2.1.3 Interpretation of Coongie Lakes 119 6.2.2 Northwest Branch of Cooper Creek 120 6.2.2.1 Scrubby Camp, "Aarpoo" and Marpoo Waterholes 120 6.2.2.2 Interpretation of Scrubby Camp, "Aarpoo" and Marpoo Waterholes 123 6.2.2.3 Tilcha Waterhole 124 6.2.2.4 Wills Grave 131 6.2.2.5 Interpretation of Tilcha Waterhole and Wills Grave 136 6.2.2.6 Cullyamurra Waterhole 137 6.2.2.7 Interpretation of Cullyamurra Waterhole 141 6.2.2.8 Innamincka Racetrack 142 6.2.2.9 Interpretation of Innamincka Racetrack 142 6.2.3 Turra 142 6.2.3.1 Turra Channel and Overbank Facies 151 6.2.3.2 Turra Source-Bordering Dune 152 6.2.3.3 Turra Longitudinal Dune 153 6.2.3.4 Interpretation of Turra 155 6.2.4 Gidgealpa Area 156 6.2.4.1 East Dog Bite Lake 156 6.2.4.2 North Dog Bite Lake 1 159 6.2.4.3 North Dog Bite Lake 2 159 6.2.4.4 Gidgealpa South 159 6.2.4.5 Gidgealpa Dune 160 6.2.4.6 Interpretation of Gidgealpa Area 160 6.2.5 Strzelecki Creek and Strzelecki Dunefield 160 6.2.5.1 Mudlalee Channel and Overbank Facies 161 6.2.5.2 Mudlalee Dunes 166 6.2.5.3 Merty Merty 169 6.2.5.4 Interpretation of Strzelecki Creek and Dunefield 173 CHAPTER 7 SUMMARY AND REGIONAL CONTEXT 175 7.1 INTRODUCTION 175 7.2 SUMMARY OF PALAEOENVIRONMENTAL CHANGES AT SPECIFIC LOCATIONS IN THE INNAMTNCKA REGION 176 7.2.1 Coongie Lakes 176 7.2.2 Northwest Branch and Cooper'Fan'Palaeochannels 177 7.2.3 Cullyamurra Waterhole 179 7.2.4 Strzelecki Creek Palaeochannels 180 7.2.5 Aeolian Sites (Turra, Gidgealpa, Mudlalee and Innamincka Racetrack) 281 IX
7.3 COMPARATIVE CHRONOLOGIES 182 7.3.1 Comparative Palaeoenvironmental Conditions within the Lake Eyre Basin 185 7.3.1.1 OIStage5(130kato74ka?) 185 7.3.1.2 OI Stage 4 (74 ka to 60 ka) 186 7.3.1.3 OI Stage 3 (60 ka to 25 ka?) 187 7.3.1.4 OIStages2and 1 (24kato 11 kaand lOkatoOka) 188 7.3.1.5 Dune Activity 189 7.3.2 Comparative Palaeoenvironmental Conditions with Tropical Northern Australia 190 7.4 CONCLUSION 192 REFERENCES 195
APPENDICES 214 X
LIST OF TABLES
Table 2.1: Monthly rainfall (mm), evaporation3 (mm) bssed upon Class A pan, lenth of rain days and temperature (maximum and minimum) for Hughenden, Windorah and Moomba stations (Bureau of Meterology, 1998) 43 Table 5.1: Mean grain-sizes and standard deviations of the major depositional environments used to perform a two-tailed t-test (P=0.05) assuming unequal variances 95 Table 5.2: Two by two table construction of the two-tailed t-test (P=0.05) performed on the 14 (J) to -2 (|) mean grain-size analysis of the major depositional environments 96 Table 5.3: Two by two table construction of the two-tailed t-test (P=0.05) performed on the sand fraction (4 (j) to -2 (f>) mean grain-size analysis of the major depositional environments 96 Table 5.4: XRD clay mineralogy from different depositional environments within the study area 99 XI
LIST OF FIGURES
Figure 1.1: Map of Australia showing the location of Cooper Creek study area in the Lake Eyre basin, the Channel Country and other important Quaternary sites mentioned in this thesis 2 Figure 1.2: Map showing the location of the study site, Lakes Eyre, Frome, Callabonna, Blanche and Gregory within the Lake Eyre basin of South Australia (Nanson et al, 1998) 3 Figure 1.3: The study area and location of sampling sites referred to in the thesis. Arrows indicateflow directio n 4 Figure 1.4: (A) Coongie Lakes region showing the location of Coongie Lake longitudinal dune and Lake Marroocutchanie lunette samplings sites. (B) Northwest branch of Cooper Creek showing the location of sampling sites along the branch and Cooper 'fan' area. Arrows indicate flow direction 5 Figure 2.1: Location of Lake Eyre basin and its major geographical features (Kotwicki and Allan, 1998) 10 Figure 2.2: Sedimentary basins of the northeast desert region, South Australia. Note that Poolowanna 1 is an oil discovery well used to identify a thick Mesozoic sequence (Krieg et al, 1990) 11 Figure 2.3: Geological summary of the Warburton Basin (modified Mines and Energy South Australia, 1998) 12 Figure 2.4: Geological summary of the Cooper Basin (Mines and Energy South Australia, 1998) 13 Figure 2.5: Geological summary of the Pedirka, Arckaringa, Simpson and Eromanga Basins (modified Mines and Energy South Australia, 1998). Fm=Formation 14 Figure 2.6: Geological summary of the Eromanga Basin and its relationship with the Cooper and Warburton Basins (modified Mines and Energy South Australia, 1998). Sst=Sandstone 16 Figure 2.7: Stratigraphic section from North Lake Eyre Basin to the Southern Strzelecki Basin showing the relationship between stratigraphic units (Tertiary and Quaternary) and the three depositional phases discussed in Section 2.2.4.2 to Section 2.2.4.3 (Krieg et al., 1990) 18 Figure 2.8: Tertiary stratigraphic units in the Lake Eyre Basin (modified Krieg etal. (1990). Lst=Limestone, Cong=Conglomerate 19 Figure 2.9: Palaeogeography of the Lake Eyre Basin during the Late Paleocene to Early Eocene (Krieg etal, 1990; Alley, 1998) 20 Figure 2.10: Palaeogeography of the Lake Eyre Basin during the Late Oligocene to Miocene (Krieg etal, 1990; Alley, 1998) 22 Figure 2.11: Palaeogeography of the Lake Eyre Basin during the Pliocene to Early Quaternary (Krieg et al, 1990; Alley, 1998) 23 xii
Figure 2.12: Illustrating the stratigraphic correlation for Quaternary units in the Lake Eyre Basin (Alley, 1998) 24 Figure 2.13: Palaeogeography of the Lake Eyre Basin during the Late Pleistocene (Krieg etal, 1990; Alley, 1998) 25 Figure 2.14: Cooper Creek as it flows through the Innamincka Dome north of Innamincka. Flow direction is from right to left of the picture 27 Figure 2.15: Cooper 'fan' located downstream of Innamincka with the Santos Moomba gasfield locate d in the background 27 Figure 2.16: Main dune trends, the annual resultant of sand-shifting winds and the principal synoptic systems effecting sand movement of the Australian dunefields (Wasson etal, 1988) 30 Figure 2.17: Aeolian sand colours of the Simpson and Strzelecki dunefields (Wasson, 1983a,b; Pell etal, 2000) 31 Figure 2.18: Major proto-source identified by Pell et al (2000) for the Simpson, Strzelecki and Tirari Deserts. SP221, SP53, SP60, ABH62A and CTJ98 are sampling sites used by Pell etal (2000) 35 Figure 2.19: The Coongie Lakes region illustrating the major lakes that form the area including Lakes Coongie and Marroocutchanie, which are sampling sites in this study (Reid and Puckridge, 1990). Arrows indicate flow direction 36 Figure 2.20: The northwest branch of Cooper Creek terminating at Coongie Lake 37 Figure 2.21: Summer/winter rainfall zones and ratios of Australia and major streams of the Lake Eyre basin (Magee, 1997) 38 Figure 2.22: A typical weather pattern (A) and related air masses (B) across Australia during summer (February) (from Sturman and Tapper, 1996). Air masses include: Em (Equatorial maritime), Sm (Southern maritime), Tc (Tropical continental), sTc (subtropical continental), iTm (Tropical maritime Indian), tTm (Tropical maritime Tasman) and pTm (Tropical maritime Pacific) 39 Figure 2.23: A typical weather pattern (a) and related air masses (b) across Australia during winter (July) (from Sturman and Tapper, 1996). Air massed include: Tc (Tropcial continental), sTc (subtropical continental), pTm (Tropical maritime Pacific), tTm (Tropical maritime Tasman), Sm (Southern maritime) and NPm (Polar maritime Northern). The 'baric ridge' represents the link between the centres of high pressure in the Pacific and Indian oceans. The result of this ridge is the form of Tc air massess over the Australian continent with maritime airmasses over the ocean 40 Figure 2.24: Monthly rainfall (mm) plotted against evaporation (mm) data derived from a Class A pan for Hughenden, Windorah and Moomba stations (Bureau ofMeterology, 1998) 42 Figure 2.25: Major waterholes and primary anastomosing channels between Currareva and Innamincka (Knighton and Nanson, 1994). W indicates location of waterholes 46 Figure 2.26: Total flow volume (output/input ratio) verses total input volume over definable flow periods for Currareva-Nappa Merrie (A) and Nappa Merrie-Innamincka (B). The data points are differentiated according to the seasonality factor represented by SF and either the presence or absence of background flow at output point (Knighton and Nanson, 1994) 47 Figure 2.27: Coolabahs {Eucalyptus microtheca) over hundreds of years old fringe the northwest branch of Cooper and Strzelecki Creeks 48 Figure 2.28: Spinifex (Triodia basedowii) hummocks located on the crests of longitudinal dunes in the Strzelecki Desert and the Coongie Lakes region 49 Figure 2.29: Soil landscape sub-regions classified by Wright et al. (1990) for the northeast desert region of South Australia 50 Figure 3.1: Astronomical theory of climate change based on A, eccentricity of the Earth's orbit, B, obliquity of the ecliptic and C, the precession of the axis of rotation (Lowe and Walker, 1997) 53 Figure 3.2: (A) Six million years ago the continental ice sheet in Antarctica bought about ocean cooling with the northerly shift and intensification of high-pressure cells. Aridity during the Quaternary reached its maximum in the Nullarbor region of southern Australia. (B) Approximately 2 Ma the Ross Sea was closed and there was a northerly extension of winter sea ice from Antarctica. The high- pressure cell moved farther north over southern Australia producing cool winter rains and westerly winds (Bowler, 1982) 55 Figure 3.3: Vostok time series and ice volumes from Petit et al (1999). (A) Deuterium record as a function of depth expressed as 5D (in %o with 18 respect to Standard Mean Ocean Water, SNOW). (B) 8 Oatm profile. (C) Seawater S180 (ice volume proxy) and marine isotope Stages. (D) Sodium (Na) profile (ppb). (E) Dust profile (ppm) 58 Figure 3.4: Vostok time series and insolation from Petit et al. (1999). (A) Carbon dioxide. (B) Isotopic temperature of the atmosphere. (C) 18 Methane. (D) 8 Oatm profile. (E) Insolation during mid-June at 65°N (Win2) 58 Figure 3.5: Loess accumulation rate from China compared with the 5180 record (SPECMAP) stack to 620 ka and ODP 677 older than 620 ka (Shackleton et al 1995) 59 Figure 3.6: Pollen diagram from Lynch's Crater, northeastern Queensland illustrating the major features (Kershaw et al, 1983) 63 Figure 3.7: Lake Amadeus sediments illustrating the eight major stratigraphic units in the Winmatti Beds (core AM3) overlying the Uluru Clay. TL dates of the youngest gypseous dunes cluster between 60 ka and 45 ka. The palaeomagnetic results indicate an uncertainty of the Bruhnes- Matuyama boundary between the gypsum and sandy clay units (modified from Chen et al 1993). Note: stratigraphic units are not drawn to scale 66 Figure 3.8: Summary log of Williams Point section and Core 83/6 with a palaeo-lake level curve after Magee et al (1995). The dates have been reported from thermoluminescence and amino acid racemisation 69 Figure 3.9: The extent of Lake Bungunnia in southeastern Australia illustrated by the thicker dashed line and the location of the two sections (Chowilla and Lake Tyrrell) used for palaeomagnetic analyses (An etal., 1986) 72 Figure 3.10: Schematic stratigraphic summary of the Murray Basin units. Silcrete-lateritized weathering profiles developed on the marine sand (Parilla Sands) are overlain by Lake Bungunnia (Blanchtown Clay and Bungunnia Limestone) sediments. Surficial deposits consisting of aeolian and saline lake deposits discomformably overlie the lacustrine sediments, which form the present landscape (modified An et al 1986). Note: stratigraphic units are not drawn to scale 73 Figure 5.1: A schematic cross-section across the northwest branch of Cooper Creek showing the location of Wills Grave (27°46'45"S, 140°36'35"E) Auger Holes 1 to 4 where samples for sediment analysis were obtained 86 Figure 5.2: A schematic cross-section across Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) showing the location of Auger Holes 1 to 4 where samples for sediment analysis were obtained 87 Figure 5.3: A schematic cross-section across Mudlalee channel and overbank section (Strzelecki Creek 28°16'43"S, 140°29'33"E) located between West Mudlalee (28°16'29"S, 140°27'34"E) and East Mudlalee (28°16'00"S, 140°31'45"E) dune sites showing the location of auger holes where samples for sediment analysis were obtained 87 Figure 5.4: Bivariate plot of mean grain-sizes compared to standard deviations for upper palaeochannel, source-bordering dune and dune surface sand fractions 90 Figure 5.5: Bivariate plot of mean grain-size verses standard deviation for dune surface, diagenetically altered dune, source-bordering dune and lunette sand fractions 92 Figure 5.6: Quartz grain surface features characteristic of fluvial and aeolian sediments of Cooper Creek: (A) numerous small three-sided V-shaped etch pits and percussion fracture pits due to collision of fluvial grains. (B) aeolian quartz grain with numerous but less dense V-shaped etch pits. (C) sub-angular to angular shaped aeolian quartz grains characteristic of Strzelecki Desert dunes. (D) rounded edges and smooth surface of the larger fluvial quartz grains 108 XV
Figure 5.7: Flow diagram illustrating how sand from Cooper and Strzelecki Creeks is transported to source-bordering dunes which longitudinal dunes have evolved formed. Additionally sand-sized clay aggregates are transported by wind from adjacent floodplains and swales and deposited on longitudinal dunes 110 Figure 6.1: LANDSAT TM image of the Coongie Lakes region including sampling sites Lake Marroocutchanie (27°07'31"S, 140°13'36"E) lunette and Coongie longitudinal dune (27°13'32"S, 140°10'45"E) 114 Figure 6.2: Crestal view to the west of Lake Marroocutchanie lunette showing the location of Auger Hole 1 and Auger Hole 2 referred to in Figure 6.3 115 Figure 6.3: Stratigraphic cross-section of Lake Marroocutchanie lunette showing the location of the auger holes, TL dates and depositional environments 116 Figure 6.4: Stratigraphic cross-section of the Coongie Longitudinal Dune site showing the location of auger holes, TL dates, isochrons and depositional environments 117 Figure 6.5: Crestal view looking north along Coongie Lake longitudinal dune site and the swale, located on the left hand side of the photo, looking towards Coongie Lake 118 Figure 6.6: LANDSAT TM image of the Scrubby Camp Waterhole (27°38'50"S, 140°22'34"E) site located along the northwest branch of Cooper Creek which flows into the Coongie Lakes region 120 Figure 6.7: LANDSAT TM image of the Marpoo Waterhole (27°45'10"S, 140°33'57"E), "Aarpoo" Waterhole (27°46'50"S, 140°31'40"E), Tilcha Waterhole (27°45'8"S, 140°36'43"E) and Wills Grave (27°46'45"S, 140°36'35"E) sites located along the northwest branch of Cooper Creek 121 Figure 6.8: Stratigraphic cross-sections of Scrubby Camp, "Aarpoo" and Marpoo Waterhole sites showing exposed cut-bank sections, TL dates and depositional environments. Note that the water level through this reach of the Cooper is probably within 1 m between the three sites 122 Figure 6.9: Tilcha Waterhole sequence, northwest branch of Cooper Creek. The stepped trench in the side of a cut-bank section showing fluvial sediments overlain by aeolian sediments further illustrated in Figure 6.12 125 Figure 6.10: Upper portion of the Tilcha Waterhole section showing palaeosol sand (Palaeosol 1) overlain by an aeolian sand unit (Aeolian Unit 5) which inturn is overlain by a second palaeosol sand unit (Palaeosol 2) illustrated in Figure 6.12 126 Figure 6.11: Trough cross-stratification of medium-grained sand (St) overlain by a gravel layer representing the erosional gravel lag at the base of the OI Stage 5 succession 126 Figure 6.12: Stratigraphic cross-section at Tilcha Waterhole, northwest branch of Cooper Creek, showing the relationship between stratigraphic units and TL dated samples 127 Figure 6.13: Overlying the large floodplain mud unit is a series of aeolian sediments, calcrete and palaeosol units 130 Figure 6.14: LANDSAT TM image of the Wills Grave and Tilcha Waterhole (27°45'8"S, 140°36'43"E) sites showing the location of the surveyed section at Wills Grave (27°46'45"S, 140°36'35"E) and the distinctive scroll bar patterns of Cooper Creek along the northwest branch 132 Figure 6.15: A Schematic section across the northwest branch of Cooper Creek showing the relationship of Tilcha Waterhole (27°45'8"S, 140°36'43"E) fluvial section and Wills Grave (27°46'45"S, 140°36'35"E) section. Note that AH1 to AH4 represent auger holes at Wills Grave referred to in Figure 6.16 132 Figure 6.16: Stratigraphic cross-section of the Wills Grave site showing the location of the auger holes, stratigraphy and TL dates. Note that the surveyed water level is recorded at 0 mon the section 133 Figure 6.17: Surveyed cross-section of Wills Grave site showing the relationship between the TL dates and the isochrons. This section identified evidence of lateral migration overlying 250 ka basal deposits. .. 134 Figure 6.18: LANDSAT TM image of Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) and Innamincka Racetrack (27°43'56"S, 140°44'23"E) sites located along Cooper Creek as it enters the confinement of the silcrete capped Innamincka Dome. Flow direction is from east to west. ..138 Figure 6.19: A schematic section across Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) showing the location of Auger Holes 1 to 4 where the surveyed cross-section, illustrated in Figure 6.20, was taken from 138 Figure 6.20: Stratigraphic cross-section of Cullyamurra Waterhole site showing the location of auger holes, TL dates and isochrons 139 Figure 6.21: Stratigraphic cross-section of Innamincka Racetrack site showing the location of the auger hole, TL dates and depositional environment 143 Figure 6.22: LANDSAT TM image showing the location of Turra (27°52'33"S, 140°22'00"E), Gidgealpa Dune (27°55'59"S, 140°13'51"E), Gidgealpa South (28°52'34"S, 140°15'45"E), East Dog Bite Lake (27°53'45"S, 140°9'22"E) and North Dog Bite Lakes 1 (27°55'14"S, 140°9'00"E) and 2 (27°57'36"S, 140°9'40"E) 144 Figure 6.23 :LANDSAT TM image showing the location of Turra fluvial transect, Turra source-bordering dune and Turra longitudinal dune sampling sites 145 Figure 6.24: Surveyed cross-section of Turra fluvial, source-bordering and longitudinal dune auger holes 146 Figure 6.25: Plan view of Turra Longitudinal and Source-Bordering Dune sites showing the surveyed dune crest, the outline of the longitudinal dune, swale and Cooper floodplain 147 Figure 6.26: Stratigraphic cross-section of Turra fluvial succession showing the location of Auger Holes 1 to 4 and TL dates. Note that source- bordering dune Auger Hole 1 is at-1800 m 148 Figure 6.27: Stratigraphic cross-section of Turra Source-Bordering and Longitudinal Dune showing the location of the auger holes and TL dates. Auger Hole 1 does not correspond to the surface profile of the source-bordering dune and longitudinal dune because it was obtained -300 m east of the dune crest longitudinal profile 149 Figure 6.28: Surveyed cross-section of Turra site, showing the relationship between sedimentary facies and marine OI Stages 150 Figure 6.29: Stratigraphic cross-section of East Dog Bite Lake, North Dog Bite Lakes 1 & 2, and Gidgealpa South showing the location of the auger holes and TL dates 157 Figure 6.30: Stratigraphic cross-section of Gidgealpa Dune showing the location of the auger hole, TL dates, isochron and depositional environments. North Dog Bite Lakes 1 and 2 are also shown schematically to illustrate their relationship with Gidgealpa Dune 158 Figure 6.31: LANDSAT TM image of Mudlalee site showing the location of Mudlalee channel and overbank facies (28°16'43"S, 140°29'33"E), West Mudlalee Dune (28°16'29"S, 140°27'34"E) and East Mudlalee Dune (28°16'00"S, 140°31'45"E) sites 162 Figure 6.32: A schematic cross-section across the Mudlalee channel site (Auger Holes 1 to 4) and associated longitudinal dunes (West Mudlalee 28°16'29"S, 140°27'34"E and East Mudlalee 28°16'00"S, 140°31'45"E) 163 Figure 6.33: Stratigraphic cross-section of Mudlalee channel and overbank facies site showing the location auger holes and TL dates 164 Figure 6.34: Surveyed cross-section of Mudlalee showing the relationship between fluvial sedimentary facies, isochrons and marine OI Stages 165 Figure 6.35: Stratigraphic cross-section of East Mudlalee site showing the location of auger holes, TL dates, isochron and depositional environments 167 Figure 6.36: Stratigraphic cross-section of West Mudlalee site showing the location of auger holes, TL dates, isochron and depositional environments 168 Figure 6.37: LANDSAT TM image Strzelecki Creek and the Strzelecki dunefield showing the location of the Merty Merty (28°35'39"S, 140°16'04"E) site 170 Figure 6.38: Stratigraphic cross-section of Merty Merty site showing the location of auger holes and TL dates 171 Figure 6.39: Surveyed cross-section of Merty Merty showing the relationship between sedimentary facies, isochrons and marine OI Stages 172 Figure 6.40: A schematic cross-section across Strzelecki Creek and Strzelecki Desert showing the stratigraphy and chronology of the depositional units 174 Figure 7.1: Comparison of TL frequency histograms from this study with those of Maroulis (2000) and Nanson et al. (1988, 1990, 1992a) classified according to depositional environments 184 Figure 7.2: Combined TL frequency histograms from this study, Maroulis (2000) and Nanson et al. (1988, 1990, 1992a) classified according to depositional environments 185 1
CHAPTER 1 INTRODUCTION
1.1 CONTEXT OF THESIS
Around 60 Ma to 50 Ma ago Australia separated from Antarctica and began to move northward, drifting to within approximately 4°S of its present latitude by the Early Miocene. During the Late Miocene to Pliocene, there was a gradual transition to more arid conditions on a global scale, marking the transition from the Tertiary to the Quaternary. The distinctive feature of the Quaternary has been a series of pronounced, global climatic oscillations that have driven glacial-interglacial cycles.
It is generally accepted that the mechanism for broadly controlling the timing of glacial and interglacial oscillations are the variations described by Milankovitch's astronomical theory. The nature and intensity of these climatic oscillations is determined from numerous and diverse sources throughout the world, including analyses of material from aeolian dunes, rivers, lakes, swamps, loess, corals, ocean cores, ice cores and glacial deposits. The sedimentary, stratigraphic and chronological record preserved in the Cooper Creek basin near Innamincka in northeast South Australia is investigated here in order to provide evidence of Australia's Quaternary climatic oscillations over the past -250 ka particularly in relation to changes that characterised the Channel Country river systems in the continent's arid-zone (Figure 1.1, Figure 1.2, Figure 1.3 and Figure 1.4).
1.1.1 Quaternary Palaeoenvironmental Reconstruction of the Australian Arid- Zone
The Australian continent extends from the tropical to temperate zone, from about 11°S to 39°S, providing widespread evidence for climatic oscillations during the glacial- interglacial cycles of the Quaternary within alluvial, aeolian and lacustrine deposits. The Australian arid-zone contains the largest subtropical desert outside of Africa. It occupies approximately 33% of the Australian continent while 75% of the continent is semi-arid and arid (Bowler, 1976; Bowler et al, 1976). Aeolian deposits cover approximately 50% of Australia and consist of largely longitudinal (linear) dunes and some source- bordering or transverse dunes near contemporary rivers or palaeochannels (Oberlander, 1994). Desert dunes record periods of aridity, windiness, wind direction and seasonality cd t-i
CZJ X! • C/PNl U CQ / e / )L3 c« NV2
t/J o O 3
Figure 1.2: Map showing the location of the study site, Lakes Eyre, Frome, Callabonna, Blanche and Gregory within the Lake Eyre basin of South Australia (Nanson et al, 1998). Ephemeral Lakes Source-Bordering Dunes
Ephemeral Creeks Longitudinal Dunes Roads /ll //
Figure 1.3: The study area and location of sampling sites referred to in the thesis. Arrows indicate flow direction. Figure 1.4: (A) Coongie Lakes region showing the location of Coongie Lake longitudinal dune and Lake Marroocutchanie lunette samplings sites. (B) Northwest branch of Cooper Creek showing the location of sampling sites along the branch and Cooper 'fan' area. Arrows indicateflow direction .
''',0km 10km M \ : | I
B :'•."',
Scrubby Camp WH '• • «.% .
.. IfaAamincka Marpoo "i : '• '•- Racetrack WH Tilcha WH
INNAMINCKA Aarpoo Wills { :.'.•/ Gidgealpa; • '. WH _j Grave \ *'•'* ; Dune :*'; * 1^ i? ytiiu**-*-*- : /. :"•' East Dog Turra • .Bite. Lake • : 3:-':iJ/. 5 Ml j -,*"• V m • i • ; ;; * •
• -'' .* { * ; *• ** »" * .' •»' J \ : .-North Dog '•. . •" .: -' • • • **-* •* Bite Lake 1 .';,. *.' t; ; • • ; • •* •| • Gidgeafpa. \ South «»••••• *""t«.;,J,: 6
whereas the palaeochannels and lakes retain information on changing precipitation, flow regime and sediment supply. Due to the extent of the Lake Eyre basin (1.3 million km2) and its central position on the continent, the rivers, dunes and lakes have responded to widespread climatic changes throughout Australia's Quaternary history. The Lake Eyre basin is a source of palaeoenvironmental data from which Australia's Quaternary climatic changes and their relationship to global climatic changes can be determined.
1.1.2 Lake Eyre Basin
The Lake Eyre basin is occupied by internally draining river systems. The largest discharge and sediment load originates from the northeast part of the basin where Cooper Creek, the Diamantina River, Warburton Creek and Georgina River all of which anabranch extensively to form an area known as the Channel Country (Figure 1.1). These rivers receive rainfall during summer, are characterised by extreme variations in discharge and flow duration, and transport water and sediment into the interior of the continent. Typical of the other large Channel Countryrivers, Coope r Creek is a low gradient (0.0002), mud transporting, predominantly anastomosing system with braided flood channels (Nanson et al, 1986, 1988). While the eastern tributaries originate in the more humid areas of the basin and can receive extensive summer rainfall, due to large transmission losses only a smallfraction if any of the water ultimately reaches Lake Eyre (Knighton and Nanson, 1994). Major flooding covering the playa surface of Lake Eyre occurs once every twenty years or so and is usually associated with exceptional La Nina phases of ENSO (Allan, 1988; Kotwicki and Allan, 1998).
The development and application of thermoluminescence (TL) dating of alluvial, aeolian and lacustrine deposits has allowed the interpretation of Quaternary histories in areas such as the arid-zone of Australia where there is abundant suitable quartz sand. Lakes, aeolian landforms and ephemeral rivers preserve information within their stratigraphy of climatic changes and the effect of such changes on depositional environments over time. However, the majority of research into climate change in the arid regions of Australia has been undertaken on lakes with relatively few studies on river systems. Partly because of this, and partly because arid regions have limited suitable depositional sites for palaeoclimatic interpretation, the geomorphology, sedimentology and Quaternary record of arid Australia remains relatively poorly investigated compared to the glaciated humid 7
areas of the world's temperate zones. Nevertheless, researchers are gradually gaining a greater understanding of the major palaeoenvironmental changes in central Australia and their relationships to global Quaternary changes as recorded in the loess deposits of China, marine sediments from various oceanic basins and ice cores from Antarctica and Greenland.
While there are some source-bordering, crescentic, parabolic and network dunes, extensive longitudinal dunes are by far the dominant feature of the Australian arid-zone. The predominant source of sand for dune construction was found to be the sandy alluvium deposited by streams within the basin before being reworked by wind. The other sources are probably the weathered regolith, especially east of Strzelecki Creek and palaeolacustrine sediments (Wasson, 1982, 1983a,b). The preliminary Quaternary chronology proposed by Wasson (1982, 1983a,b) for the dunes is further investigated in this thesis to determine dune-building phases for this area of Cooper Creek (Figure 1.3 and Figure 1.4).
Cooper Creek near Innamincka (Figure 1.3) provides an excellent opportunity to study the sedimentary and chronostratigraphic record preserved as palaeochannels, aeolian dunes (longitudinal and source-bordering) and lunettes representing climate and flow regime change over the past 250 ka in central Australia. The region also presents an opportunity to study fluvial and aeolian interaction over this period. This study extends the Quaternary record, not just for Cooper Creek, but also for the Lake Eyre basin as a whole.
1.2 AIMS
The four principle aims of this research are:
1. to describe the alluvial, aeolian and lacustrine stratigraphy and chronology of Cooper Creek, the Coongie Lakes, Strzelecki Creek, and sections of the Strzelecki dunefield, all within the vicinity of Innamincka in South Australia;
2. to establish stratigraphic and geomorphic evidence for interactions between alluvial, aeolian and lacustrine systems as evidence for Middle to Late Quaternary climatic history in this region; 8
3. to determine when Coongie Lake formed as the present terminus or distributary of Cooper Creek, and when Strzelecki Creek carried substantial flows from Cooper Creek to greater Lake Frome;
4. to compare the Quaternary record of climate and flow regime changes in this region with other Australian terrestrial records.
1.3 THESIS OUTLINE
Chapter 2 describes the physiography of the Lake Eyre basin with specific reference to the northeast desert region of South Australia and the study area of Cooper Creek near Innamincka. A detailed literature review of this part of the Lake Eyre basin includes geological history, climate, hydrology, vegetation and soils. Chapter 3 reviews the progressive development of Late Cainozoic climatic changes in Australia, growth of the Antarctic ice cap and declining temperatures from the Tertiary to Quaternary. It briefly examines evidence for orbital variations, related Quaternary oscillations, and correlations between the loess deposits of China, marine sediments from the North Atlantic and ice cores from Greenland and Antarctica. The majority of the chapter reviews the existing Middle to Late Quaternary record in Australia with specific examples from northern, central and southern Australia. Chapter 4 outlines the methods used in this thesis including thermoluminescence dating, grain-size analysis, petrographic analysis, scanning electron microscopy (SEM) analysis of quartz surface grains and X-ray diffraction of clays conducted on the sediment samples collected from the region's major depositional environments. Chapter 5 discusses the sedimentological results obtained using the above methods. Chapter 6 compares and contrasts the surveyed Quaternary stratigraphic sections from alluvial, aeolian and lacustrine sites. Chapter 7 draws together the results obtained from Chapters 5 and 6, constructing a Quaternary history of Cooper Creek near Innamincka over the past 250 ka. The second part of Chapter 7 concludes the thesis by comparing and contrasting the palaeoenvironmental history of this portion of Cooper Creek with records from other Australian terrestrial Quaternary study sites. 9
CHAPTER 2 GEOLOGICAL EVOLUTION AND PHYSIOGRAPHY OF THE LAKE EYRE DRAINAGE BASIN
2.1 INTRODUCTION
With an area of 1 300 000 km2, the Lake Eyre drainage basin is Australia's largest covering one-seventh of the continent. It is a wide, shallow, low-gradient, intracratonic basin bounded to the east by the highlands of Queensland, the MacDonnell Ranges of the Northern Territory in the north, the Musgrave, Everard and Stuart Ranges in the west and by the Flinders Ranges in the south (Figure 2.1). Spreading over mostly arid central Australia, more than 90 % of the Lake Eyre basin is less than 500 m in elevation and it is composed of a complex array of floodplains and channels with gradients less than 0.0002 (Kotwicki, 1986; Nanson et al, 1988; Magee et al, 1995), aeolian dunes, gibber plains, stony desert plateaux, playa lakes and freshwater wetland systems. The geological evolution and physiography of the Lake Eyre drainage basin is described in this chapter with special reference to northeastern South Australia where the study site is located.
2.2 GOELOGICAL EVOLUTION
The sedimentary succession in northeastern South Australia illustrates numerous unconformities that represent times of erosion, weathering and relative inactivity in the region. Sedimentary strata can be divided into five unconformity-bounded sedimentary sequences overlying each other as a result of erosional events related to uplift and/or climatic change. Each sequence of strata represents a distinct depositional entity occupying a separate sedimentary basin. The oldest basin is the Warburton Basin, followed by the Cooper and Pedirka Basins, Simpson Desert Basin, Eromanga Basin and the Cainozoic basins (Figure 2.2).
2.2.1 Warburton Basin (Early Palaeozoic)
The Warburton Basin formed during the Early Palaeozoic and lies along the southwestern edge of the Thomson Fold Belt. The majority of the Warburton Basin lies north of the Flinders Ranges, extending into Queensland and the Northern Territory (Gatehouse, 1986; Krieg et al, 1990). The Warburton Basin includes the Early Cambrian Mooracoochie Volcanics, and shallow marine deposits of the Ordovician Dullingari Group and Innamincka Formation (Figure 2.3). 10
Study Site
Figure 2.1: Location of Lake Eyre basin and its major geographical features (Kotwicki and Allan, 1998). 11
Cainozoic basins 1H Early Tertiary sandstone and siicreta (section onlyl Eromanga Basin
Simpson Desert Basin ^ Cooper Basin© Pedirka Basin© (ticka towards Warburton Basin iaiini_-
Figure 2.2: Sedimentary basins of the northeast desert region, South Australia. Note that Poolowanna 1 is an oil discovery well used to identify a thick Mesozoic sequence (Krieg et al, 1990).
3 0009 03295245 4 12
Age (Ma) ROCK UNIT
Carb-Cret Cooper/Eromanga Basin
Dullingari Group
Ordovician
Innamincka Formation
Kalladeina Formation
Cambrian Mooracoochie Volcanics
Pando Formation
Proterozoic
Figure 2.3: Geological summary of the Warburton Basin (modified Mines and Energy South Australia, 1998).
2.2.2 Cooper, Pedirka and Simpson Basins (Carboniferous-Triassic)
Subsidence along zones of crustal weakness within the Warburton Basin during the Devonian could have resulted in the intracratonic depressions, which eventually formed the Cooper (Figure 2.4) and Pedirka Basins (Figure 2.5; Veevers, 1984). These two basins unconformably overlie the Early Palaeozoic strata of the Warburton Basin and are overlain disconformably by the central Eromanga Basin sequence. Melting and retreat of ice in the Early Permian mobilised large volumes of sandy sediment which were
deposited as glacial debris or formed bed-load supplied to river systems. These deposits are known as the Merrimelia Formation and Tirrawarra Sandstone in the Cooper Basin,
and the Crown Point Formation in the Pedirka Basin. The overlying sediments, named the Patchawarra Formation (Cooper Basin) and Purni Formation (Pedirka Basin), are 13
interbedded with 30 m thick coal seams dated to the Early Permian (Gatehouse, 1972). Widespread lake deposits covered parts of the southern Cooper Basin towards the end of the Early Permian, forming the Epsilon and Daralingie Formations and the Murteree and Roseneath Shales. During the Late Permian, meandering river deposits alternated with flood basin lake sediments forming the Toolachee Formation. Deposition then continued into the Early Triassic where the Nappamerri Group overlies the hydrocarbon reservoirs.
Figure 2.4: Geological summary of the Cooper Basin (Mines and Energy South Australia, 1998). 14
Age (Ma) ROCK UNIT
Algebuckina Sandstone
Jurassic Poolowanna v Formation J
EROMANGA BASIN
1 Peera Peera 1 Formation Triassic
1 Walkandi / 1 Formation /
SIMPSON BASIN
Mt Toondina Formation
Permian PurniFm \ \ Cfimrt i3 lUd.lL Range Fm s Crown Boorthanna Point Fm Formation
Late Carb PEDIRKA ARCKARINGA BASIN BASIN
Undifferentiated Warburton Cambrian- Officer and Amadeus Basin Devonian sediments.
Figure 2.5: Geological summary of the Pedirka, Arckaringa, Simpson and Eromanga Basins (modified Mines and Energy South Australia, 1998). FnHFormation. 15
The Pedirka Basin is in part disconformably overlain by Triassic sediments of the Simpson Basin (Figure 2.5). These include the Walkandi Formation, which is restricted to the Poolowanna Trough (major depocentre), and the overlying Peera Peera Formation. The Walkandi and Peera Peera Formations are at present separated by the Birdsville Track Ridge (Krieg et al, 1990).
2.2.3 Eromanga Basin (Early Jurassic-Late Cretaceous)
Mesozoic sediments of the Eromanga Basin (Figure 2.5 and Figure 2.6) cover a total area of 50 000 km2 in northeastern South Australia alone, with Tertiary strata of the Lake Eyre basin underling much of eastern central Australia. Following relatively stable tectonic conditions towards the end of the Triassic and the beginning of the Jurassic; renewed crustal downwarping over the northeastern part of Australia in the Early to Late Jurassic initiated the development of the Eromanga Basin. The Eromanga Basin is an intracratonic sedimentary basin containing predominantly terrestrial clastic strata with a thinner marine clastic sequence deposited in a shallow epicontinental sea during an Early Cretaceous transgression (Simon-Coincon et al, 1996).
The Algebuckina Sandstone (Figure 2.5 and Figure 2.6) was initially deposited by large, northerly flowing, moderately energeticrivers wit h fluctuating discharge but the rivers became more active and more uniform in flow over time. The Early Jurassic Poolowanna Formation (meandering-anastomosing fluvial) occurs in the Poolowanna Trough and integrates southwards with the Algebuckina Sandstone. Krieg et al. (1990) suggested that braided to anastomosing moderate to high-energy fluvial environments were responsible for the deposition of the Poolowanna Formation. The Early Jurassic Hutton Sandstone (Figure 2.6) is considered to represent widespread low sinuosity braided stream deposits and is widely distributed. The Hutton Sandstone forms a major aquifer in the Great Artesian Basin and is also a reservoir rock for oil. Elsewhere the Hutton Sandstone and Birkhead Formation (fluvio-lacustrine backswamp) are in transitional contact. The Murta Formation is recognised as a lacustrine unit conformably overlain by the Cadna-owie Formation that represents a transition from fluvial conditions (Algebuckina Sandstone) to a marine environment (Marree Subgroup; Figure 2.6). The Marree Subgroup (Bulldog Shale, Coorikiana Sandstone, Oodnadatta Formation and Mackunda Formation) represents the marine deposited interval of the Eromanga Basin 16
Age ROCK UNIT (Ma) WEST EAST
Tertiary- LAKE EYRE BASIN Recent
Lake Eyre Basin (Callabonna sub-basin) Mt Howie Winton Fm Sandstone
Mackunda Fm
Alleru Fm Oodnadatta Fm Toolebuc Fm Cretaceous Z -(Coorikiana Sst 5) Wallumbilla Fm Bulldog Shale
Cadna-Owie Formation Murta Fm —Z Namur Sandstone
rt ^> Westbourne Fm Jurassic I Adori Sandstone 60 J^> Birkhead Formation Hutton Sandstone .X" Poolowanna Fm
Late Triassic Cuddapan Formation
Carb-E.Trias COOPER BASIN
Cambro-Ordov WARBURTON BASIN Proterozoic
Figure 2.6: Geological summary of the Eromanga Basin and its relationship with the Cooper and Warburton Basins (modified Mines and Energy South Australia, 1998). Sst=Sandstone. 17
(Figure 2.6). It was deposited over a time interval of approximately 15 Ma giving way to terrestrial conditions approximately 100 Ma ago. The Winton Formation and Mount Howie Sandstone (Figure 2.6) represent a return to terrestrial,fresh water conditions laid down in a fluvio-lacustrine phase of deposition (sluggish meandering streams, shallow lakes and marshes) during the Late Cretaceous when the vegetation consisted of extensive forests with ferns and aquatic plants (Krieg et al, 1990; Alley, 1998).
Recorded deposition of the Eromanga Basin concluded approximately 95 Ma ago and for the next 35 Ma, no sedimentary record exists for the region. Widespread erosion is thought to have occurred during this time, as indicated by the erosional contact with the overlying Eyre Formation and the preservation of only the lower part of the Winton Formation around the margins of the basin. A long phase of weathering and erosion prevailed from the Cenomanian to Late Paleocene. Downwarping produced a number of shallow sedimentary basins, the largest being the Lake Eyre Basin in which thin sheets of clastic strata were deposited at various phases during the Late Paleocene to Middle Eocene, Late Oligocene to Miocene, and the Quaternary (Krieg et al, 1990; Simon- Coincone?a/., 1996).
2.2.4 Stratigraphy of the Lake Eyre Basin
Three depositional phases occurred in the Lake Eyre Basin during the Cainozoic (Figure 2.7). Thefirst depositional phase was from the Late Paleocene to the Middle Eocene when the Eyre Formation and equivalents were deposited during warm, wet conditions in a landscape dominated by river systems (Figure 2.7, Figure 2.8 and Figure 2.9). The second depositional phase (Late Oligocene? to Early Miocene) includes the Etadunna Formation, Namba Formation, Doonbara Formation and Cadelga Limestone (Figure 2.7 and Figure 2.8). This phase was dominated by shallow freshwater lakes and was much drier than the previous depositional phase (Figure 2.10). The third depositional phase (Figure 2.11; Pliocene? to Quaternary) was drier still, consisting of the Wipajiri, Tirari, Kutjitara, Katipiri, Eurinilla, Millyera, Coomb Spring and Coonarbine Formations, Simpson Sand in the central part of the basin and Willawortina Formation on the basin boundary (Figure 2.12). The present Simpson and Strzelecki dunefields, playas and contemporary rivers are the result of these three major sedimentary depositional phases that formed successively since the beginning of the Cainozoic Era 18
(~65 Ma ago; Krieg et al, 1990). The latest of these three phases involved the deposition of fluvial sands, aeolian dunes and saline lake deposits, influenced by several glacially related wetting and drying cycles, and these deposits are the subjects of this study (Figure 2.13).
Figure 2.7: Stratigraphic section from North Lake Eyre Basin to the Southern Strzelecki Basin showing the relationship between stratigraphic units (Tertiary and Quaternary) and the three depositional phases discussed in Section 2.2.4.2 to Section 2.2.4.3 (Krieg etal, 1990). 19
Age Tirari Sub Basin Callabonna Sub Basin (Ma) atgrnary Sediments Quaternary
I iranMn Pliocene
Silcrete and Ferricrete Development
Wipajiri Fm Yardina Miocene '"' Claystone/ Alberga Fm Limestone
Mirackina Cong
Muloorina Member
Oligocene Silcrete and Ferricrete Development
Cordillo Surface and Silcrete
Mirachina Cong
Paleocene Weathering and Silcrete Development
Figure 2.8: Tertiary stratigraphic units in the Lake Eyre Basin (modified Krieg et al (1990). Lst=Limestone, Cong=Conglomerate. 20
2.1 A.l Phase 1: Late Paleocene to Middle Eocene
Eyre Formation
The Eyre Formation (Figure 2.7, Figure 2.8 and Figure 2.9) is widespread throughout the Lake Eyre Basin forming the basal unit of the Tertiary strata. It is related to the Glendower Formation (Northern Territory and southwestern Queensland) and the Marion Formation (western Queensland and New South Wales). The Eyre Formation mainly consists of pyritic, carbonaceous sand, silt and several gravel horizons. The base of the unit is characterised by polished gravel composed of milky quartz, chert, jasper, agate and silcrete pebbles in parts of the basin. In some areas the formation reaches over 100 m in thickness and the carbonaceous clays (swamp deposits) exceed 80 m in the southern section of the basin. Braided streams deposited the early Eyre Formation, in areas of subsidence associated with the Eocene epeirogenic uplift of the Olary Block and Barrier Ranges source areas (Krieg et al, 1990; Alley, 1998).
LATE PALEOCENE- EARLY EOCENE
Figure 2.9: Palaeogeography of the Lake Eyre Basin during the Late Paleocene to Early Eocene (Krieg etal, 1990; Alley, 1998).
During the Early Eocene, extensive erosion occurred, followed by fluvio-lacustrine deposition of the Eyre Formation in the Middle Eocene (Krieg et al, 1990; Alley, 1998).
The most prominent and complex units of this region are the river channels, consisting of sandy bars, small-scaleripples and scour hollows each with characteristic cross-bedding 21
structures. Present also are clay lenses, sapropels and fine laminated silts representative of floodplain deposits. These sediments are common in humid environments of modern river deposits where there is an abundant sand supply (Krieg et al, 1990).
2.2.4.2 Phase 2: Late Oligocene? to Early Miocene
Etadunna andNamba Formations
Epeirogeny occurred in the Late Oligocene to Early Miocene, deforming the Eyre Formation into broad anticlines and synclines. Downwarping at this time produced two centres of deposition, thefirst i n the Lake Eyre region and southern Simpson Desert, and the second extending from the northern Strzelecki dunefield to Lake Frome (Krieg et al, 1990). The phase 2 deposits extend throughout the northeastern part of the basin, unconformably overlying the Eyre Formation and extending into the Northern Territory and southwest Queensland.
Dolomite and clay of the Etadunna Formation (Tirari Sub-basin), Namba Formation (Callabonna Sub-basin) and co-related formations in other parts of the basin were deposited during the Early Miocene (Figure 2.7, Figure 2.8 and Figure 2.10). The Mampuwordu Sand, Muloorina, Yardina Claystone and Alberga Limestone are members of the Etadunna Formation (Figure 2.7 and Figure 2.8). In the Lake Eyre region, the Etadunna Formation can reach 80 m in thickness, disconformably overlain by Quaternary deposits.
Borehole data and outcrops indicate that the Namba Formation has an average thickness of 90 m in the southwestern Callabonna Sub-basin and a maximum thickness of 170 m. The Namba Formation is lithologically similar to the Etadunna Formation, comprising fine to medium-grained sand, silt, clay and dolomite (Krieg et al, 1990; Alley, 1998).
Doonbara Formation and Cadelga Limestone
The Doonbara Formation is approximately 7 m to 10 m thick. It overlies the Cordillo Silcrete or Eyre Formation and is overlain by the Cadelga Limestone (Figure 2.8). The Doonbara Formation is interpreted as a lateral fluvial facies of the Etadunna Formation (Wopfher, 1974), while to the east of Strzelecki Creek the Namba Formation is possibly equivalent to the Doonbara Formation (Callen, 1983). The Cadelga Limestone is a 22
lacustrine limestone up to 5 m thick that overlies and incorporates fragments of the Doonbara Formation (Krieg et al, 1990; Alley, 1998).
LATE OLIGOCENE - MIOCENE
Figure 2.10: Palaeogeography of the Lake Eyre Basin during the Late Oligocene to Miocene (Krieg etal, 1990; Alley, 1998).
2.2.4.3 Phase 3: Pliocene? to Quaternary
Wipajiri, Tirari and Willawortina Formations
The Wipajiri Formation is defined from central Tirari Desert where it consists of a fine grained channel-fill deposit cut into the Etadunna Formation (Figure 2.8). Unnamed black clay and white sand underlying the Tirari Formation (Tirari Desert) is thought to be part of the Wipajiri Formation and is interpreted as a meandering fluvial system in a lacustrine fan-delta (Figure 2.8 and Figure 2.11). The Tirari Formation (Figure 2.12) is extensively exposed over the central Tirari Desert and Simpson Desert and consists of red/brown silt, sandy channel deposits and massive gypcrete. The depositional environment was probably intermittent stream flow under semi-arid conditions. The Tirari Formation also contains the bones of various extinct marsupials, including Diprotodon and numerous species of kangaroo. The Willawortina Formation (Figure 2.7 and Figure 2.12) is located in the Callabonna Sub-basin as a sandy mud and silty dolomite unit deposited under alluvial fan, floodplain and lacustrine conditions. Coarser facies consist of gravels deposited by channel and debris flow processes. Its age ranges from Late Pliocene to recent (Krieg et al, 1990; Alley, 1998). 23
7PLI0CENE - QUATERNARY Former strandllnes
Figure 2.11: Palaeogeography of the Lake Eyre Basin during the Pliocene to Early Quaternary (Krieg etal, 1990; Alley, 1998).
Kutjitara Formation
In the Tirari Desert the Kutjitara Formation (Figure 2.12) was deposited under fluvio- lacustrine and aeolian conditions. The unit is well exposed along lower Cooper Creek, where it overlies the Etadunna Formation, and at Warburton River where it forms channel-fills cut into the Tirari Formation. The Kutjitara Formation is regarded as a predominantly fluvial unit in the east, but is classified as a lacustrine facies near Lake Eyre. Based on TL and ESR dating, the formation is probably Middle Pleistocene (Krieg etal, 1990; Alley, 1998).
Katipiri, Eurinilla, Millyera and Coomb Spring Formations
Meander belts up to four times wider than at present have been cut into the Tirari and Kutjitara Formations and contain several sets of fluvio-lacustrine sediments and recessional shoreline dunes. The Katipiri Formation (fluvial and aeolian unit) was deposited under similar conditions to the Tirari Formation but is more visible throughout the region (Figure 2.12). It has been thoroughly dated with TL and was deposited largely during the interglacial periods of OI Stages 7 and 5 (Nanson etal, 1991, 1992a). Late Pleistocene units containing similar facies to the Katipiri Formation occur in the
Strzelecki Desert (Eurinilla Formation) and in the Lake Callabonna area (Millyera Formation; Figure 2.12). Beach sand around Lake Frome, named the Coomb Spring 24
Formation, intertongues with the Millyera Formation representing higher lake levels at Lake Frome and perhaps some connection with Lake Eyre (Krieg et al, 1990; Alley, 1998). The Katipiri, Coomb Spring and Millyera Formations (300 ka to 200 ka) are represented in the meander scrolls of the former tracts of the Cooper, Warburton and Strzelecki Creeks.
Coonarbine Formation and Simpson Sand
The linear dunes, which form the large whorl pattern around central Australia, are named Coonarbine Formation in the Strzelecki Desert and Simpson Sand in the Simpson Desert (Figure 2.12). The transverse dunes, which formed along the lee side of Lakes Eyre, Frome and Callabonna, are due to deflation of sediments from the basin'sfloor (Krieg et al, 1990; Alley, 1998) or by sediment deflated from beaches during lake-full periods. The morphology, sedimentology, chronology and provenance of the Simpson/Strzelecki dunefield are discussed further in Section 2.3.4.1.
Figure 2.12: Illustrating the stratigraphic correlation for Quaternary units in the Lake Eyre Basin (Alley, 1998). 25
LATE PLEISTOCENE
Figure 2.13: Palaeogeography of the Lake Eyre Basin during the Late Pleistocene (Krieg et al, 1990; Alley, 1998).
2.3 REGIONAL SETTING OF THE STUDY AREA
2.3.1 Cooper Creek and Strzelecki Creek
The study area consists of dunefields, mesas, gibber plains, wetlands, playas, claypans, ephemeral channels and contemporary rivers and creeks. Throughout its geological history the region has experienced interspersed periods of deposition, weathering and erosion, warming and cooling, and wetting and drying leading to the evolution of large rivers (meandering with extensive floodplains), shallow lakes and swamps forming a number of sedimentary depositional basins which have been discussed in Section 2.2.
Cooper Creek is approximately 1 520 km long with a total catchment area of approximately 306 000 km2. At Innamincka, drainage from the upstream catchment (236 700 km2) is restricted to a single channel by silcrete outcrops, with a scoured section forming Cullyamurra Waterhole (Figure 1.3). Downstream of Innamincka, Cooper Creek branches into two main flow systems, one flowing northwards into Coongie Lakes and the other west towards Lake Eyre (Figure 1.1 and Figure 1.2). Every 9 to 10 years when the Australian monsoon is intense and extends farther south than normal, floodwater from the Cooper (at Innamincka) flows south into Lake Blanche via a third channel known as Strzelecki Creek (Figure 1.2). The present partial dislocation of Strzelecki Creek appears to be due to uplifting of the Innamincka Dome (Figure 2.14). This course may have previously been a regular distributary channel for 26
Cooper Creek, flowing southwards into expanded versions of Lakes Blanche and Frome. The beginning of Strzelecki Creek at Innamincka is presently elevated and receives overflow from Cooper Creek only when stage heights there exceed approximately 8 m. The creek descends 20 m in its 100 km traverse, a gradient of 20 cm per km similar to that of Cooper Creek in the Channel Country (Callen and Bradford, 1992).
2.3.2 Innamincka Dome and Cooper Creek 'Fan'
The Innamincka Dome is a faulted anticline bringing the upper part of the Mesozoic succession to the surface (Figure 2.14). The age of the uplift and whether it is still proceeding is unknown, and whether Tertiary sediments thin near the dome, or whether they were eroded and removed during deposition of the Namba Formation is also uncertain. The Innamincka Dome reaches a height of approximately 245 m above the river plain north of Innamincka and approximately 70 m in height above the gibber plains along the South Australia/Queensland border. The broadly fan-shaped area north of Moomba (Figure 1.2 and Figure 2.15) is interpreted by Callen and Bradford (1992) as a very large 'low-angle alluvial fan' formed by the Cooper as it emerges from its confined course through the Innamincka Dome. The maximum westward regional slope on the Cooper 'fan' is about 0.00027, which is close to double the slope of 0.00014 on the adjacent plains. The area of the 'fan' is approximately 30 x 22 km, characterised by east- trending source-bordering dunes located on the northern margins of abandoned watercourses and floodout areas (Figure 1.2 and Figure 1.3). Linear dunes appear to have formed from these source-bordering dunes and extend northwards. These features are common on the 'fan' where there is rapid sedimentation and watertable fluctuation providing access to adequate sand and some clay pellets for dune construction.
The Cooper 'fan' area is formed of palaeochannels and fluvial scroll deposits. Wasson (1983a) described the 'fan' surface as consisting of uniform grey muddy fluvial fine grained silty sand, approximately 1 m thick, overlying orange/yellow mottled alluvial fine-grained sand with laminae of clay up to 0.02 m thick and extending to at least 3 m in depth. This lower unit becomes coarser with depth, containing sub-horizontally bedded granules and coarse-grained sand. 27
Figure 2.14: Cooper Creek as it flows through the Innamincka Dome north of Innamincka. Flow direction is from right to left of the picture.
Figure 2.15: Cooper 'fan' located downstream of Innamincka with the Santos Moomba gas field located in the background.
2.3.3 The Gibber Plains
Extensive areas of the Strzelecki and Simpson Deserts, the mnamincka region, the Lake Eyre region, and the Sturt Stony Desert are covered with angular to rounded cobbles of silicified Tertiary strata. This gibber surface originates from the in situ breakdown of sihcified Tertiary strata associated with scarp retreat and the intermittent alluvial and colluvial transport of these sediments. Gibber derived by alluvial transport also contains 28
clasts from basement areas and from reworked Mesozoic strata (Callen and Benbow, 1995).
Some of the gibber material resulted directly from the erosion of the Early to Late Tertiary silcrete that formerly extended over most of the Lake Eyre depression. The formation of silcrete in the region is uncertain. However silcrete in the region is thought to have originated from acid groundwaters dissolving silica, iron and titanium oxides with the subsequent precipitation of silica in the evaporative zone of soils, either as opal or more likely as quartz (Krieg et al, 1990). Some of the material may have been transported to the Lake Eyre basin and its depressions by theriver systems that drain into the basin (Twidale, 1972). The gibbers were either derived as a lag deposit from scarp retreat undermining the silcrete duricrusts, such as those deposits surrounding Innamincka, or is of pebble size and has been locally transported by streams and rivers flowing towards the centre of the drainage basin (Twidale, 1972).
2.3.4 Simpson/Strzelecki Dunefield
2.3.4.1 Morphology, Sedimentology, Chronology and Provenance of the Dunefield
According to Wasson's (1983a) interpretation, the major phase of dune construction occurred between 23 ka B.P. to 12 ka B.P. The source of the sand to form transverse dunes was derived from sandy alluvium under presumably more active river flow conditions. Then, mud-rich sand pellets and mineral grains derived from mixed load alluvium dominated the dune building. The stratigraphic data shows that during much of the last 23 ka B.P., most dunes were adjacent tofloodflats and thus receiving a mud-rich load. The presence of alluvium beneath the dunes throughout the northern Strzelecki Desert (west of Strzelecki Creek) and the Simpson Desert illustrates that these dunes were not derived from lakeshore dunes (Wasson, 1983 a) as previously thought. An interpretation of the litho-stratigraphic record in the subsurface of the Moomba gas field area concluded that the sediments forming the upper 50 m are all alluvial (Wasson, 1983a).
Morphology of dunes
Figure 2.16 depicts the orientation of the Australian continental dunefield as an anti clockwise whorl stretching from Gibson Desert in southwestern Australia to the Great 29
Sandy Desert in the northwest, a spread of 19° in latitude and 30° in longitude (Brookfield, 1970). The sand has been transported to the east in the southern section of the whorl, towards the north in the east and towards the west in the northern part of the whorl pattern (Wasson, 1986). Narrow crested, linear dunes dominate the majority of dunefields in central Australia whereas broad crested linear dunes, network dunes, and parabolic and irregular dunes cover a small percentage of the area. The linear dunes, also known as longitudinal can extend for tens of kilometres in length and most commonly are spaced between 300 m to 600 m apart (Twidale, 1972; Wasson, 1986; Wasson etal, 1988).
Dune spacing or frequency varies from more than 15 dunes per kilometre to approximately three dunes or less per kilometre. Dune height, taken as its elevation above the surrounding desertfloor, varies with dune frequency. In areas of low dune density the dunes reach their greatest height whereas in areas of high dune frequency the sand ridges are lowest. In the deserts surrounding Lake Eyre, dune height varies from 10 m to 12 m to very occasionally more than 50 m. As the sand is swept diagonally across the dunes, the larger dunes trap more sand than the small ones. It is believed that the smaller dunes become starved and gradually disperse as their sediment is transferred to the larger dunes, which increase in height and volume (Twidale and Wopfher, 1990).
Rubin (1990) concluded that the dunes of the Strzelecki Desert have migrated laterally while they extended or migrated northward. However, Nanson et al (1992b) have shown that there is no evidence for any extensive lateral migration. At Birdsville, some slight eastward migration is evidenced by dune asymmetry, by surficial sediment distribution and by bedding within the dunes. Wind data demonstrate that the dunes are oblique to the modern transport direction, and the asymmetric accumulation of Holocene sediment demonstrates that a different wind direction has prevailed through much of the Holocene (Nanson et al, 1995). The orientation of the extensive linear dunefields almost certainly dates from the Pleistocene (Wasson, 1983a,b; Nanson et al, 1992b,
1995). Sand is currently being transported along the crests, causing some dunes to continue to extend or migrate northward, however, this is not a significant process when seen in context of the length of some of these linear dunes. 30
i i i i i 1 * annual resultant of sand-shifting wind 0 400
Figure 2.16: Main dune trends, the annual resultant of sand-shifting winds and the principal synoptic systems effecting sand movement of the Australian dunefields (Wasson et al, 1988).
Sedimentological composition
The dunes of the Simpson and Strzelecki dunefields are primarily composed of moderately to well-sorted quartz grains (-98 %) ranging in size from 0.05 mm to 1.2 mm; other components of dunes are carbonates, heavy minerals, gypsum and clay minerals (illite, kaolinite, smectite). The quartz grains are generally sub-angular to sub- rounded, frequently displaying hollows and other concave surfaces (Twidale, 1972; Wasson, 1983b; Twidale and Wopfner, 1990).
Another significant feature of the Simpson and Strzelecki dunefields is their colour. Wasson (1983b) recorded pale brown (10YR 7/4 to 5YR 6/8) and red/brown (5YR 6/8 to 2.5YR 4/8) dune sands as the two dominant colour groups (illustrated in Figure 2.17), whereas Twidale and Wopfher (1990) describe the dunes as white to dark orange/red. The red/brown colour of the sand grains is the result of iron oxides coating the sand grains, groundwater having leached the iron from iron-rich substrates prior to aeolian transport (Wasson, 1983a,b). The strikingly red colour of the dunes east of Strzelecki Creek results from mobilisation of iron from ferruginised Tertiary sediments that formed 31
the local regolith in the region from which the sand was derived. The pale dunes to the west of Strzelecki Creek are the result of sand derivation from Strzelecki Creek, which also supplies a small proportion of mud pellets to the dunes in the northern areas (Wasson, 1982; Gravestock et al, 1995; Sheard, 1995a). A transition zone which varies from 10 km to 20 km wide exists between the pale brown and red/brown dunes east of Lake Frome, while to the north of Lake Frome, Strzelecki Creek forms the boundary between pale brown and red/brown dunes.
Figure 2.17: Aeolian sand colours of the Simpson and Strzelecki dunefields (Wasson, 1983a,b; Pell etal, 2000).
Wasson (1983a,b, 1986) found that the heavy mineral content of the red/brown dunes was lower than the pale dunes, and the iron content is higher. Pale colour sands (fine grained) occur near the modern channels of the Diamantina River and Cooper Creek, with the coarser red/brown sands located away from the channels in the northern 32
Simpson Desert and eastern Strzelecki Desert. Thin section analysis showed that sand- size clay pellet content of sands ranged between 5 % and 12 % in the southern Simpson Desert and was less towards the north.
Chronology
In the southern Strzelecki Desert Callen etal. (1983) dated pedogenic carbonate, located in the fluvial sand deposits underlying dunes and fluvial muds, obtaining ages of 35kaB.P. to 22kaB.P. At Lake Frome, Bowler (1976) illustrated, by dating carbonates on aeolian islands within the lake, that gypsum deposits were formed between 20 ka B.P. and 16 ka B.P. Additionally, Gardner et al. (1987) TL dated younger periods of dune formation giving ages between 9.9 ka and 5.5 ka at Lake Frome (Strzelecki Desert), whereas a quartzose aeolian unit underlying these younger dunes dated at 48.1 ka. Carbonates precipitated in palaeosols, which separate aeolian sediments have been dated by Callen et al. (1983) at Lake Moko, east of Lake Frome to range between 26.1 ka and 7.2 ka. However, these results reply on dating pedogenic carbonates and such results are now regarded with suspicion (Callen et al, 1983).
In the northern Strzelecki Desert near Moomba, Wasson (1983a) radiocarbon dated charcoal particles at the base offluvial sediment s obtaining ages between 22.3 ka B.P. and 12.5 ka B.P. Longitudinal dunes containing charcoal record an age between 2.3 ka B.P. and 1.0 ka B.P. (Wasson, 1983b). These dates were supported by Gardner et al. (1987) who TL dated linear dunes ranging from 3.7 ka to 0.8 ka and who also stated that aeolian activity near Moomba began approximately 243 ka.
In the northeastern Simpson Desert, Nanson et al (1988) recorded three sand units separated by clayey sand as part of a duneflanking th e Diamantina River. Using TL, the lowermost clayey sand unit was dated at 274+22 ka and the second gave a TL age of
32.5 ±6ka. Another dune consisting of two sand units located in the same region, gave a
TL date of 55.5+6 ka for the lower unit. Wopfher and Twidale (1988) and Twidale and Wopfher (1990) believed that the Simpson Desert dunefield wa s mostly Holocene in age and definitely younger than 40 ka, but this has been clearly contradicted by Gardner et al (1987) and Nanson et al. (1988, 1992b). The most intense or possibly best preserved 33
and dated aeolian activity occurred at or near the lower boundary of the Last Glacial Maximum.
Sand provenance
The dunes of the Simpson and Strzelecki dunefields lie in well-defined Cainozoic basins that adopted their basic shape during the Eocene period (Wasson, 1982). The dunefields continue to accumulate non-aeolian fluvial sediment, which contrasts with the dunefields of the Great Sandy, Great Victoria and Gibson Deserts where very little non-aeolian sediment has been deposited during the Quaternary (Wasson, 1983a).
There has been a difference of opinion regarding the cause of the whorl of dunes in central Australia (Figure 2.16). Researchers have speculated on the relationship between past and present wind systems to the formation of Australia's continental dune systems. It was generally accepted that the anticlockwise whorl of dunes is related to the winter anticyclonic circulation over the continent (Sprigg, 1963; Mabbutt, 1967), however Brookfield (1970) showed that the strongest winds are related to summer cyclones rather than winter anticyclones in central Australia as proposed by Sprigg (1963) and Mabbutt (1967). Kalma et al. (1988) argued that the pattern might be coincidental with different strong sand-moving winds not being the product of a single system of anticyclone circulation. This suggests that an anticyclonic system combined with contraction of the arid-zone to the north of the continent and/or strengthening of high-pressure belts to the south, is more probable to explain dune trends rather than a 'single system'. Nanson et al (1995) used the chronology, alignment and asymmetry of dunes in the Finke region (Northern Territory) to infer changes in the anticlockwise wind pattern, concluding that there was a northward shift in the anticlockwise whorl of sand-transporting winds during the last glacial. Thus supporting latitudinal movement of the anticlockwise wind patterns that deposited and aligned the longitudinal dunes of central Australia.
Twidale (1972, 1981) described how linear dunes are initiated and extended downwind from source-bordering dunes located on the northern sides of playas and alluvial plains, particularly in the Simpson Desert. He argued that there is a long-term cycle of long distancefluvial transport and deposition followed by aeolian transport and deposition. In contrast, Wasson (1983a, 1986) argued that the Simpson and Strzelecki dunefields are 34
derived from a wide number of sediment sources by different mechanisms and not just from source-bordering deposits as suggested by Twidale (1972). Wasson (1983a, 1986) suggested that in the Simpson Desert the dunes were derived directly from alluvium along rivers in the south, from groundwater controlled deflation of old alluvium and lake beds in the south-centre, from old alluvium in the north, and from weathered regolith east of Strzelecki Creek.
Recently, Pell et al (2000) utilised SHRIMP U-Pb dating of single zircon grains from the Simpson, Strzelecki and Tirari Deserts. They constructed 'expected' zircon age histograms to determine provenance or proto-source areas for the supply of sediment not only for the above dunefields already mentioned, but additionally for the Mallee and Tanami dunefields, Great Victoria, Gibson and Great Sandy Deserts (Pell et al, 1997). The principal sand source areas, in order of decreasing relative input, for the southeastern Simpson, Tirari and Strzelecki Deserts are from the Tasman Orogenic System (New England and Lachlan Fold Belts), Georgetown Inlier, Musgrave and Arunta Blocks, Gawler and Curnamona Cratons; whereas for the northeastern and western Simpson Desert sand was derived from Arunta, Musgrave and Mount Isa Blocks and Tennant Creek Inlier (Figure 2.18). They concluded that the zircon age measurements indicate that sands are derived from areas only a few hundred kilometres in distance.
The recent work by Pell and Chivas (1995) also concluded that the surface features on the sand grains (irregularity, absence of features characteristic of aeolian transport, presence of intricate surface features and an abundance of chemically produced features) indicate that the Simpson and Strzelecki dunefields are currently stabilised and have not undergone long distance transport. That is, the sand was initially transported by rivers during the Cretaceous and Cainozoic, and then weathered and eroded from rocks of that age and reworked by wind locally. 35
Figure 2.18: Major proto-source identified by Pell et al. (2000) for the Simpson, Strzelecki and Tirari Deserts. SP221, SP53, SP60, ABH62A and CTJ98 are sampling sites used by Pell et al (2000).
2.3.5 Coongie Lakes
The Coongie Lakes are approximately 108 km northwest of Innamincka (Figure 1.2 and Figure 1.3) and occupies a total area of 19 800 km2. This freshwater wetland system is listed under the Australian Ramsar Convention, Site 27, and is composed of a mosaic of channels, floodplains, lakes, waterholes, and interdune corridors and swamps that provide a variety offloral an d faunal habitats. The area specifically includes Lakes Coongie, Marroocoolcannie, Marroocutchanie, Marradibbadibba, Toontoowaranie, Goyder, Marradibbadibba, Apachirie, Mundooroounie, Apanburra and Warra Warreenie (Figure 2.19). Lakes Coongie, Marroocoolcannie and Marroocutchanie are fed by the northwest branch of Cooper Creek, while the northern lakes Toontoowaranie and Goyder are fed by Browne and Ellar Creeks (Figure 2.19; Lange and Fatchen, 1990; Morelli, 1995). Modelling conducted by Kotwicki and Clark (1991) indicated that between 1889 and 1989, the northwest branch of Cooper Creek flowed on 75 occasions 36
7023000N 7023000^
«»62O00N 6962000N
Figure 2.19: The Coongie Lakes region illustrating the major lakes that form the area including Lakes Coongie and Marroocutchanie, which are sampling sites in this study (Reid and Puckridge, 1990). Arrows indicate flow direction. 37
but only reached Coongie Lake itself on 50 of those occasions. As described by Krieg and Callen (1990), the Coongie Lakes system is one of net sediment accumulation with the surrounding dunefield undergoing burial and preservation.
The channels of Coongie Lakes form the major conduits between the lakes (Figure 2.20), which are 4km to 2km across and with a maximum depth of 2.5m to 2m. The foreshore unit consists of fine-grained, white sand with large Coolabah woodland and rashes growing in the shallows around the lake margins. The dunefield consists of lunettes on the northern boundaries of the lakes and linear red/orange, normerly-trending elongate dunes that extend lengthwise for tens of kilometres and average 10 m to 20 m in height. The floodout areas consist of undifferentiated alluvialflats o ffine-grained clayey sand, and the swamp areas are characterised by anastomosing channel networks (Krieg and Callen, 1990).
Figure 2.20: The northwest branch of Cooper Creek terminating at Coongie Lake.
Approximately half of the Coongie Lakes area is held as Crown Land-Pastoral Lease and the remaining is Crown Land-National Park Reserve, with the surrounding catchment being Crown Land-Pastoral Lease. The area is mainly used for cattle grazing and petroleum exploration (oil and gas) by Santos Ltd, but is becoming increasingly popular for tourism. Culturally, the Cooper Creek system sustained a significant Aboriginal population, especially during major flooding events, and was a major Aboriginal trading route across Australia (Morelli, 1995). Aboriginal sites include middens, artefacts, rock engravings, arrangement sites, burial sites and quarries. 38
2.4 CLIMATE
The Lake Eyre basin extends across the tropical northern summer-rainfall and temperate
southern winter-rainfall zones from 39°S to ITS shown in Figure 2.21 (Magee, 1997). The major influence on climate within the Lake Eyre basin is the position of the southeasterly trade belt. Seasonal variations result from the shifting position of the high- pressure belt from southern Australia in summer to central Australia in winter (Figure 2.22 and Figure 2.23). The principal synoptic influence on rainfall in the basin is of tropical origin, resulting in an area with the highest rainfall variability, both spatially and temporally, in Australia. This includes moist tropical air mass incursions, rain and monsoon depressions and thunderstorms, with mid-latitude influences allied to frontal activity that forms over the Great Dividing Range during the Australian monsoon (Allan, 1990).
Figure 2.21: Summer/winter rainfall zones and ratios of Australia and major streams of the Lake Eyre basin (Magee, 1997).
The summer rainfall maximum is related to the incursion of humid tropical air masses where there is a shift in the inter-tropical convergence zone (ITCZ; Figure 2.22). Equatorial maritime air located over the northern region of Australia is incorporated 39
within monsoonal circulation and the development of lows which contribute to the development of the inter-tropical convergence zone consisting of equatorial maritime, tropical maritime and tropical continental air masses. Within this zone extensive convective activity and precipitation occur during the wet season. The easterly movement of tropical maritime and tropical continental air occurs over central Australia, where the maritime air becomes modified to continental air as it is carried inland by the trade winds.
Figure 2.22: A typical weather pattern (A) and related air masses (B) across Australia during summer (February) (from Sturman and Tapper, 1996). Air masses include: Em (Equatorial maritime), Sm (Southern maritime), Tc (Tropical continental), sTc (subtropical continental), iTm (Tropical maritime Indian), tTm (Tropical maritime Tasman) and pTm (Tropical maritime Pacific). 40
Figure 2.23: A typical weather pattern (a) and related air masses (b) across Australia during winter (July) (from Sturman and Tapper, 1996). Air massed include: Tc (Tropcial continental), sTc (subtropical continental), pTm (Tropical maritime Pacific), tTm (Tropical maritime Tasman), Sm (Southern maritime) and NPm (Polar maritime Northern). The 'baric ridge' represents the link between the centres of high pressure in the Pacific and Indian oceans. The result of this ridge is the form of Tc air massess over the Australian continent with maritime air masses over the ocean.
In winter, southern continental and maritime air masses influence the basin (Figure 2.23) while the ITCZ is located north of the equator and the southeast trade winds cover most of the northern region. In the north, the dominant air masses are either tropical 41
continental or tropical maritime, tending to be stable. The high-pressure belt moves northward over the continent, dominating central Australia and making it cooler (Sturman and Tapper, 1996). Occasionally, cut-off low-pressure systems of mid-latitude origin are responsible for widespread rainfall, especially when they interact with the relief of the northern Flinders Ranges (Allan, 1990).
Maximum temperatures average between 39°C to 36°C (hot and dry) during summer and 24°C to 18°C in winter. Between spring and autumn, the prevailing winds are from the south-southeast, becoming more variable in winter when the subtropical anticyclonic belt is over the centre of the continent (Kotwicki, 1986; Allan, 1990; Kotwicki and Clark, 1991; Sheard, 1995a; Simon-Coinconera/., 1996).
Mean annual precipitation varies from 500 mm to 400 mm in the upper reaches of the Georgina and Diamantina Rivers and Cooper Creek, where regular rainfall is received in summer months, to less than 120 mm at the point of entry to Lake Eyre. Mean annual pan evaporation (class A pan) varies from 2 400 mm in the northeast of the basin to more than 3 600 mm at Lake Eyre (Kotwicki, 1986; Kotwicki and Isdale, 1991; Magee et al, 1995). Rainfall, evaporation and temperature (maximum and minimum) for three stations, Hughenden, Windorah and Moomba, are displayed in Table 2.1, with rainfall and evaporation shown in Figure 2.24. The dry climate is a consequence of extremely high evaporation that exceeds rainfall by an order of magnitude or more throughout the year. However, marked seasonal variations in evaporation occur, with average values reaching 500 mm to 450 mm in January (summer) but only 100 mm to 90 mm in July
(winter) (Allan, 1990).
Major rainfall and flooding extremes are a manifestation of the El Nino Southern Oscillation (ENSO) with extensive rainfall events and majorfillings of Lake Eyre linked to the La Nina phase. During this phase cloud cover and convective activity are enhanced in the Australasian region, with above average rainfall during the winter-spring seasons, often extending into summer following an early onset and southerly incursion of the monsoon. Less extensive floods are associated with transient synoptic features influencing the basin. From April 1962 to May 1963 the Coongie Lakes region flooded as a result of La Nina conditions with the flow down Cooper Creek. La Nina activity also occurred from May 1973 to October 1974, and February 1975 to March 1976 42
causing flooding in all of the major rivers, tributaries and interdune corridors and filling Lakes Eyre and Frome (Allan, 1990). The 1984 flood was produced by a tropical depression that built up in the northwest of Australia and moved southeast through northern Australia (Kotwicki, 1986). Major floods in the basin are the result of annual rainfalls exceeding 500 mm with the runoff coefficient approaching 0.05. The main catchment areas of the basin lie under what has been called the 'fluctuation zone' of the seasonal migration of the monsoonal trough (Kotwicki and Isdale, 1991).
140 j j 600
120 - 500
•'
100- i 1 400 < ilS Mooniba rainfall •g' 80 I I Windorah rainfall C i 'Uugh«idtn rainfall s 300 « i " Moomba evaporation r"\ / r S —*— Windorah evaporation 1 "j . c. —«— Hu^icnden evaporation Vc 03 - \ J^ - 200 40- r- 1 | 100 20 1 J rr r •-, " _r {
0 - \ ffl ] th IM n -- u Jan Feb Mar Apr May lJuln Ju l Aug Sep Od 1Nov Dec Montinh
Figure 2.24: Monthly rainfall (mm) plotted against evaporation (mm) data derived from a Class A pan for Hughenden, Windorah and Moomba stations (Bureau of Meterology, 1998). 43
Hughenden (Queensland] Station No: 30024 Record Period 1884-1998 Altitude: 324 m Location: 20° 51'S 144°12'E Rainfall Evaporation0 Length of Temperature (°C) Month (mm) (mm) Rain Days Maximum Minimum Jan 116.6 238.7 as 35.8 22.5 Feb 97.5 198.8 7.5 34.7 22.0 Mar 58.7 198.8 47 33.7 20.5 Apr 25.6 186.0 2.2 31.4 17.0 May 18.2 145.7 1.8 27.9 13.2 Jun 18.6 120.0 1.8 25.0 9.8 Jul 12.2 127.1 1.4 25.0 8.8 Aug 7.1 161.2 0.9 27.5 10.3 Sep 8.9 207.0 1.3 31.0 13.9 Oct 20.3 257.3 2.6 345 17.9 Nov 32.9 264.0 4.0 36.2 20.5 Dec 69.6 266.6 5.9 37.0 22.0 .Annual 486.1 2372.5 42.3 Mean=31.6 Mean=16.5 Windorah (Queensland) Station No: 38024 Record Period 1887-1996 Altitude 126 m Location: 25° 42' S 142° 66" E FSainfal! Evaporation8 Length of Temperature (°C) Month (mm) (mm) Rain days Maximum Minimum Jan 41.1 384.4 4.6 38.0 24.0 Feb 49.2 313.6 42 36.4 234 Mar 40.2 297.6 3.6 34.4 21.0 Apr 20.3 219.0 22 2a9 15.8 May 19.5 148.8 2.4 25.2 11.2 Jun 16.0 108.0 25 21.5 7.5 Jul 15.2 1147 23 21.2 6.4 Aug 10.2 158.1 1.8 23.8 7.9 Sep 10.6 222.0 20 27.9 11.7 Oct 18.6 291.4 3.0 32.2 16.2 Nov 19.8 351.0 3.4 35.4 19.7 Dec 29.6 JJJ. -J 3.8 37.7 22.3 Annual 290.1 3008.5 35.3 Mean=30.3 Mean=15.6 Moomba (South Australia) Station No: 17096 Record Period: 1972-1998 Altitude: 39 m Location 28° 1V S 140°21'E RairrfaB Evaporation8 Length of Temperature (°C) Month (mm) (mm) Rain days Maximum Minimum Jan 47.6 486.7 3.8 37.3 23.1 Feb 23.8 411.6 28 36.7 228 Mar 12.1 387.5 1.8 •JO q 19.5 Apr 143 252.0 2.3 28.6 148 May 19.5 161.2 3.0 23.6 10.8 Jun 11.7 111.0 23 19.8 7.4 Jul 17.3 117.8 3.1 124 6.3 Aug 9.2 170.5 2.3 220 7.6 Sep 9.5 2420 2.3 25.9 10.8 Oct 20.9 337.9 3.6 29.9 148 Nov 12.8 405.0 3.4 33.5 18.6 Dec 21.3 480.5 3.0 36.5 21.3 Annual 219.9 3540.5 33.5 Mean=28.9 Mean=148
Table 2.1: Monthly rainfall (mm), evaporation" (mm) bssed upon Class A pan, lenth of rain days and temperature (maximum and minimum) for Hughenden, Windorah and Moomba stations (Bureau of Meterology, 1998). 44
2.5 HYDROLOGY
Kotwicki (1986) modelled the Lake Eyre drainage basin and found that the Warburton, Diamantina and Georgina catchments contribute 64 % of the mean annual inflows entering Lake Eyre, with 17 % coming from the Cooper catchment and 19 % from other sources. Frome Creek and Clayton River periodically carry floodwaters to Lake Eyre from the northern Flinders Ranges and the Neales and Macumber Rivers and Margaret Creek bring runoff from the western uplands (Allan, 1990; Armstrong, 1990).
The summer monsoon in northern Australia is presently the major source of water to Lake Eyre in the form of overflows from the Channel Country that pass through the Innamincka Dome and the Tirari Desert along a gradually diminishing channel. For extended periods (commonly 5 to 10 years) there is no flow along the lower reaches of Cooper Creek and it has been reported that windblown dunes blocked the Cooper in the 1930s and 1940s prior to the first recent filling of Lake Eyre in 1949 (Kotwicki, 1986). An exception to a monsoon source was the 1984 flood when Lake Eyre South filled due to localised heavy rains in southwest South Australia causing flooding of the Warriner, Margaret, Gregory and Frome Creeks (Armstrong, 1990). Both the 1984 and 1989 floods were unusual in that they were both caused by very large flows in the western tributaries of Lake Eyre, mainly the Neales River due to localised rainfall. Lake Eyre wasfilled withi n a few days by inflows ranging up to 30 000 mV1 (Kotwicki and Clark, 1991).
Cooper Creek, Diamantina River and Georgina River are the three major (ephemeral) river systems of the Lake Eyre drainage basin. All three streams have low slopes (mean 15 to 25 cm per km) and while they transport some sand in their main anastomosing channels, their principal load is mud, which is transported across extensive floodplains (Nanson et al, 1988). The channels of Cooper Creek form complex patterns with low- sinuosity braided floodplain channels and deeper anastomosing systems predominating, the latter varying from straight to highly sinuous (Nanson et al, 1986, 1988; Rust and Nanson, 1986). This coexistence of multiple channel systems is a feature that had not been recognised in previous modern or ancientfluvial studies. 45
The Cooper Creek drainage basin includes the Barcoo and Thomson Rivers, which drain the western side of the Great Dividing Range in central and northern Queensland (Figure 2.1). A well-defined pattern of anastomosing channels is maintained for approximately 1 500 km, particularly from Currareva in southwest Queensland (mean annual flow 3.35 km3) to Innamincka (mean annual flow 2.06 km3) where the channel becomes more constricted (Figure 2.25). Only 0.72 km3 of the mean annual flow enters Lake Eyre, however, in most years there is no input to the lake (Kotwicki, 1986; Knighton and Nanson, 1994). Lake Eyre itself isfilled onl y during periods of extensive tropical inland rainfall, although on average, some waters from the Diamantina and Warburton Rivers reach Lake Eyre North every few years (Allan, 1990).
The largest flood recorded for the Cooper was in February 1974, with a maximum daily discharge of 24 974 mV1 (recorded at Currareva) and the highest monthly flow of 6.49 km3 (recorded at Innamincka) and the highest instantaneous flow 3 740 mV1 (recorded at Innamincka) on 18 February 1974 (Kotwicki, 1986; Knighton and Nanson, 1994).
A large range of flow volumes can be accommodated with the capacity of the channel- floodplain system varying from less than 1 000 m2 where the flow is concentrated into a single primary channel at Meringhina Waterhole (Figure 2.25; Queensland) to greater than 100 000 m2 along the Cooper floodplain. Between Currareva and Nappa Merrie (>400 km) transmission losses exceed 75 % on average above a threshold flow of 25 % duration (Figure 2.26). This is due to the very widefloodplain and multichannel pattern of Cooper Creek, with drainage diffusion, infiltration and evaporation the principal cause of transmission loss (Knighton and Nanson, 1994). Between Nappa Merrie and Innamincka the more confined channel and shorter distance (32 km) reduces evaporation and drainage diffusion. Therefore, peak flows are better correlated and transmission losses are less, varying from 60 % above the threshold discharge to less than 10 % for higher magnitude flows of under 20 % duration (Figure 2.26). 46
Currareva Waterhole
Tanbar Waterhole/---'
JACKSON •
WILSON RIVER
Figure 2.25: Major waterholes and primary anastomosing channels between Currareva and Innamincka (Knighton and Nanson, 1994). W indicates location of waterholes. 47
IJO 25% 20% 10% 5% 2% 0.5% Duration o»m«xlmuni dally w™ discharga during flow A pariod al Curraravt
0 1976 0,8
/ 0.6 / >° / 0 t974 "s « / z * • / > 0.4
' \ /
02
* / • O * *;„• i ,i . "i .i 1 10 100 1000 'OOOO 100000 3 TOTAL FLOW VOLUME AT CURRAREVA |VC). 10* m
40% 30% 20% 10% 2% 0.5% rjwatian ol rnanrnum daily B discharge during flow pariod at Nappa MKIW 1 13.
° 1.0
Jff-o"'p * 0
% y 0 1*74 2 >5 OJ.). / s ;T a/ 0 / • / ° 08 / J / O SFJiO / • SF<0 / O • No backgroundflow a t output point 0 0 Non-zaro background flow at output point M 9
.1 • 1 1 1 1 10 100 1000 10000 100000
3 TOTAL FLOW VOLUME AT NAPPA MERRlE Figure 2.26: Total flow volume (output/input ratio) verses total input volume over definable flow periods for Currareva-Nappa Merrie (A) and Nappa Merrie-Innamincka (B). The data points are differentiated according to the seasonality factor represented by SF and either the presence or absence of background flow at output point (Knighton and Nanson, 1994). 48 2.6 VEGETATION Coolabah trees (Eucalyptus microtheca) fringe the channels (Figure 2.27) and are scattered across thefloodplains of therivers flowing into the Simpson Desert, and occur along Cooper and Strzelecki Creeks in the Strzelecki Desert. Old man saltbush (Atriplex nummularia) is also common, while lignum (Muehlenheckia cunninghamii) dominates the swamp communities and Queensland bluebush (Chenopodium auricomum) is associated with the levees andfloodplains of therivers within the study area (Lange and Fatchen, 1990). Corkbark (Hakea eyreana), Bauhinia spp. and other tree and shrub species typical of the central and northern Australian deserts, including Acacia spp., Eucalyptus spp., Eremophyla spp. and Atriplex spp., become prominent in northeastern Strzelecki (Gravestock et al, 1995; Sheard, 1995b). Figure 2.27: Coolabahs (Eucalyptus microtheca) over hundreds of years old fringe the northwest branch of Cooper and Strzelecki Creeks. Vegetation along parts of Cooper Creek channel, near Innamincka, includes large river red gums (^Eucalyptus camaldulenis) with tall mixed woodland of coolabah, Acacia salicina and Eremophila bignoniflora. On thefloodplains there is lignum and grassland or sedgeland (Cynodon dactylon, Cyperus spp.) present. Floodout areas associated with Strzelecki Creek include mixed grasses and Eragrostis setifolia, Dactyloctenium radulans, Enneapogon spp., Sclerolaena bicornis, S. intricata and Senecio gregorii (Lange and Fatchen, 1990). 49 Figure 2.28: Spinifex (Triodia basedowii) hummocks located on the crests of longitudinal dunes in the Strzelecki Desert and the Coongie Lakes region. In the Strzelecki Desert the dune crests are partially bare, with scattered sandhill canegrass (Zygochloa paradoxa) and the annuals buckbush (Salsola kali) and Crotalaria eremea, while slope and interdune areas are occupied by 'spinifex' or porcupine grass (Triodia basedowii) with occasional sandhill wattle (Acacia ligulata) and Nicotiana velutina (Lange and Fatchen, 1990). The spinifex forms large dense hummocks spreading outwards from the centre foraiing doughnut-shaped spinifex rings up to several metres across (Figure 2.28). The most important sand-binding grass on the dunes is the canegrass, which grows to a height of 120 cm, and has ridged, branched stems. Ephemeral plants, such as roly-poly (Plagiosetum refractum) and Trichodesma zeylanicum, appear after rains and help stabilise the dunes (Specht, 1972). 2.7 SOILS Siliceous sands are the dominant soils of the Simpson and Strzelecki dunefields with earthy sands and to a lesser extent, grey/brown and red calcareous soils (Figure 2.29). The dominant soils of the floodplains, braided channels and lakes (sub-region 2) are grey clays. These grey and brown clays are dominated characteristically by abundant smectite, display self-mulching properties and form gilgai. Red clays, red earths and desert loams are mainly located on the stony tablelands and downs (sub-region 3). Shallow sands and clay loams prevalent in sub-region 3 are located on tops of mesas, 50 ridges and steep slopes. Some red clays and desert loams are located on the gently sloping alluvial plains (sub-region 4) where smectite is the dominant clay. This sub- region is dominated by solonised brown soils (earthy and calcareous) and can occur in swales. The Innamincka low hills and plains (sub-region 5) are composed of siliceous sands. These are the most fertile soils, storing a large amount of water following rains, allowing stabilisation of dunes by vegetation. There are also, to a lesser extent, red earth soils and grey/brown and red calcareous soil in this sub-region. Red and brown hardpan soils are located only in this sub-region, occurring on red platy silica-cemented palaeosol. The hardpan is coated with a hard crust of calcium carbonate and is often mistaken for calcrete (Wright etal, 1990). Figure 2.29: Soil landscape sub-regions classified by Wright et al. (1990) for the northeast desert region of South Australia. 51 CHAPTER 3 A REVIEW OF QUATERNARY CLIMATIC OSCILLATIONS WITH SPECIFIC REFERENCE TO AUSTRALIAN QUATERNARY TERRESTRIAL RECORDS 3.1 INTRODUCTION The Quaternary Period is characterised by distinctive global climatic changes that resulted in major eustatic changes and expansion and contraction of glaciers and deserts and various biomes worldwide. The beginning of the Quaternary period is somewhat disputed but is generally accepted to have started about 2 Ma. The Quaternary is further sub-divided into the Pleistocene (~2 Ma to -10 ka) and Holocene (-10 ka to present) epochs. The Pleistocene sub-divisions are defined by the Brunhes-Matuyama magnetic reversal at -780 ka (Shackleton et al, 1990; Bassinot et al, 1994) that separates the Early and Middle Pleistocene, and the end of the penultimate glacial at -130 ka (Shackleton et al, 1990; Bassinot et al, 1994) that separates the Middle and Late Pleistocene. By measuring the oxygen isotope (OI) ratios (180/160) in planktonic foraminifera obtained from deep ocean cores, the major temperature and sea level changes associated with the glacial-interglacial fluctuations have been determined (Aitken, 1990; Andersen and Borns, 1994; Bender et al, 1994). Glacial episodes were found to coincide with intervals of relatively enhanced 180 and depleted 160 in foraminifera due to changes in oceanic isotope composition coinciding with the growth of 160-rich continental ice sheets, while the interglacial episodes coincide with the relative depletion of 180 in microfossils due to higher ocean temperatures and the addition of meltwater in the oceans (Emiliani, 1955; Shackleton and Opdyke, 1973; Budd and Smith, 1979; Lorius et al, 1985; Nelson et al, 1985; Bassinot et al, 1994). The Marine OI Stage boundaries correspond to rapid isotopic changes in the oceans representing major climatic shifts (Shackleton and Opdyke, 1973; Chappell and Shackleton, 1986; Martinson etal, 1987; Duplessy etal, 1991; Bassinot etal, 1994). The glacial stages during the Quaternary were characterised by major continental ice sheets and glacial activity throughout extensive areas of the northern hemisphere. In Australia direct glacial activity was limited to sections of southeastern Australia and Tasmania. The glacials (cold stages) were interspersed with interglacials (warm stages) where temperatures were generally higher than at present. These are further sub-divided into interstadials (warm periods during glacials) and stadials (cold periods during 52 interglacials). Based upon deep-ocean sediment cores, it is estimated that between thirty andfifty glacia l stages and a corresponding number of interglacials occurred during the Quaternary (Shackleton et al, 1995; Lowe and Walker, 1997). Each isotopic Stage has been assigned a number; the even numbers representing glacial episodes while the interglacial phases are odd numbers. The OI Stages are further divided into varying substages, such as the warmest part of the OI Stage 5 being designated as substage 5e (Shackletonetal, 1990; Cortijo etal, 1994; Adkins etal, 1997). The causes for the glacials and interglacials are complex, however Milankovitch theory (or astronomical theory) has become generally accepted as describing the basis of global variations during the Quaternary (Berger, 1992; Bassinot et al, 1994; Lowe and Walker, 1997; Williams et al, 1998). The Milankovitch theory relates climatic changes on a global scale with three orbital parameters of the Earth and the solar energy subsequently reaching the Earth. These parameters are: (1) eccentricity of the Earth's orbit, (2) obliquity of the ecliptic and (3) the precession of the axis of rotation. Eccentricity refers to changes in the Earth's orbital shape, and hence its distance from the sun, between almost circular to elliptical occurring with a periodicity of approximately 96 ka (Figure 3.1 A). The obliquity describes the changes in the tilt of the Earth's axis of rotation relative to the orbital plane and hence the tilt of the northern hemisphere towards the sun. The obliquity varies from 24.5 ka to 21.5 ka over a period of 42 ka (Figure 3.IB). Precession, describes the 'wobble' of the Earth's axis of rotation occurring over a period of 21 ka (Figure 3.1C). While Milankovitch theory is successful in defining the timing and intensity of the major global climatic variations over the past 2 Ma, it is still unclear as to whether it can explain all of the climatic oscillations during the Quaternary (Imbrie and Imbrie, 1980; Bassinot et al, 1994; Shackleton et al, 1995; Boyle, 2000). The cooling that occurred at the end of the Tertiary appears to have undergone a change to the Quaternary oscillations that saw dramatic fluctuations in climate, including glaciations and related changes in sea level (Bowler, 1986). As Australia moved northward during the Tertiary it was overtaken by cooling and associated arid conditions. This occurred initially in the south due to cooling of the oceans and the formation of the Antarctic icecap that produced changes in atmospheric circulation such 53 as the increase in high-pressure systems, reduced temperatures and stronger winds (Bowler, 1986). Figure 3.1: Astronomical theory of climate change based on A, eccentricity of the Earth's orbit, B, obliquity of the ecliptic and C, the precession of the axis of rotation (Lowe and Walker, 1997). 54 This chapter starts by briefly looking at the relationship between the Quaternary loess deposits of China, the deep-sea sediments from the North Atlantic and the ice cores from Greenland and Antarctica, as these sites contain high-resolution, long records that characterise global climatic changes spanning more than one glacial cycle. The second part of the chapter reviews the Australian Quaternary climatic events that are evident in the dune, lake and river deposits and from palaeosols, beginning with examples from the wet-dry climatic zones of northern Australia. Evidence from central Australia is then reviewed, with specific reference to the Lake Eyre basin and the study site. Finally, the detailed evidence of Late Quaternary climate change in southeastern Australia is assessed. This systematic review is important as it places in context the evidence obtained here for climate and flow regime changes in what is presently one of the driest parts of the Australian continent. 3.2 GROWTH OF ANTARCTIC ICECAP AND DECLINING TEMPERATURE Oxygen isotope palaeo-temperature analysis of Antarctica obtained from deep-sea cores indicates that Antarctica was free of ice during the Early Cainozoic (Bender et al, 1994; Brook et al, 1996; Blunier et al, 1998). The ocean temperatures surrounding Antarctica during the Eocene were approximately 18°C with the climate generally warmer and more humid than at present with major equatorial ocean currents encircling the globe (Bowler, 1976, 1982). From approximately 50 Ma Australia's northward movement resulted in a Southern Ocean seaway opening between Antarctica and Australia. The westerly wind circulation began to establish the Antarctic Circumpolar Current (ACC), which circles Antarctica and prevents warm currents from reaching the Antarctic coast. Even though the ACC was not able to develop fully due to the presence of shallow barriers around the South Pole, oceanic cooling proceeded in the higher latitudes due to the restriction of heat exchange imposed by the ACC. The end of the Eocene (-38 Ma) saw the development of a major cooling period where deep-water temperatures declined resulting in freezing temperatures at sea level around Antarctica and the expansion of extensive sea ice (Bowler, 1976, 1982; Williams etal, 1998). The movement of India towards the Eurasian landmass during the beginning of the Miocene (30 Ma) resulted in the closure of the equatorial currents and the widening of 55 the Southern Ocean, which produced further cooling and the formation of ice on Antarctica. Mikolajewicz et al (1993) suggested that parallel changes in atmospheric carbon dioxide levels in association with changes in thermohaline circulation of the Southern Ocean and not just oceanographic changes, may have been required for Antarctic ice sheet expansion between 34 Ma and 30 Ma. The Middle Miocene saw the presence of extensive Antarctic ice and cooling, and by the Late Miocene global cooling resulted in a sea level fall of 50 m to 40 m. As the sea temperatures cooled sufficiently, southern Australia came under the seasonal influence of oscillating high-pressure cells (Bowler, 1976, 1982; Williams etal, 1998). Figure 3.2: (A) Six million years ago the continental ice sheet in Antarctica bought about ocean cooling with the northerly shift and intensification of high-pressure cells. Aridity during the Quaternary reached its maximum in the Nullarbor region of southern Australia. (B) Approximately 2 Ma the Ross Sea was closed and there was a northerly extension of winter sea ice from Antarctica. The high-pressure cell moved farther north over southern Australia producing cool winter rains and westerly winds (Bowler, 1982). As high-pressure cells intensified moving towards the north of the Australian continent, aridity during the Cainozoic began in the Nullarbor region approximately 6 Ma (Figure 3.2A). The Early Pliocene had a slightly warmer interlude, but the conditions were still cooling. At the same time the northern hemisphere had also cooled with ice sheets having grown there by 2.4 Ma. Marked cooling occurred during the Early Pleistocene driving the paths of the anticyclones farther north into the Australian 56 continent (Figure 3.2B; Bowler, 1982). These climatic conditions brought about the cooling and aridity towards the end of the Tertiary, and initiated the onset of Quaternary climatic oscillations (Bowler, 1976), with their periodicity possibly controlled by the Milankovitch astronomical variations. Numerous rhythmic climatic oscillations from cold to warm conditions are apparent in the OI analyses from marine foraminifera, global sea level records and terrestrial evidence (e.g. Chinese loess deposits). After -0.9 Ma the amplitude of environmentalfluctuations in the marine sediments increased along with the increasing size of the ice sheets, andfluctuations occurre d every 100 ka (Cortijo et al, 1994; Field et al, 1994; Fronval and Jansen, 1996; Seidendrantz et al, 1995). The maximum glaciation period during the past 130 ka occurred between about 25 ka and 18 ka. By about 10 ka extensive land ice had receded, marking the beginning of the Holocene interglacial conditions (Bond et al, 1992; Broecker et al, 1992; Lowe and Walker, 1997; Williams et al, 1998; Cortijo et al, 2000). 3.3 CLIMATIC EVENTS FROM THE CHINESE LOESS DEPOSITS, NORTH ATLANTIC SEDIMENTS AND ICE CORES FROM GREENLAND AND ANTARCTICA Bender et al. (1994) investigated the link between the climates of Greenland and Antarctica during the last glacial by correlating OI data in the GISP2 (Greenland) and Vostok (Antarctica) ice cores. The ice core recovered from Greenland recorded twenty- four interstadials (Chen et al, 1997) during the last glacial spanning 105 ka to 20 ka, whereas the Vostok core from Antarctica only records nine interstadials during the same time span. The twenty-four interstadials from Greenland are characterised by very rapid warming, moderate cooling and then rapid cooling towards the end of these interstadials. This Greenland record shows a high degree of similarity to the deep-sea sediment record from the Atlantic (Bender et al, 1994) and they both indicate climatic instability throughout the North Atlantic region during the last glacial (Bender et al, 1994). In contrast, the Vostok ice core shows that the related events in Antarctica were characterised by slow warming and cooling and that warm interstadials occurred there only when those in Greenland lasted longer than 2 ka. Therefore, this suggests that glaciations and changes in ocean circulation are only partially responsible for the climatic relationship between Greenland and Antarctica, and that some other factor or factors are involved. However, Chen et al. (1997) suggested that more evidence is required to 57 confirm the occurrence of global climatic instability during the last glacial. Additionally, ice older than 115 ka in the GISP2 core shows rapid variation in 8180, which is not evident in the Vostok record (Bender et al, 1994). The Antarctic ice sheet appears to have bee a much less responsive system than the Greenland ice sheet. Most recently, preliminary data from the Vostok project yielded an ice core to a depth of 3 623 m indicating four-climate cycles for the past 420 ka (Figure 3.3; Petit et al, 1999). The record shows both similarities and differences between the successive interglacial periods. Petit et al. (1999) also confirmed strong correlations between atmospheric gases (carbon dioxide and methane) with Antarctic air temperature, and their correlation with the Earth's obliquity and precession (Figure 3.4). The Loess Plateau of central China has provided a climatic record based upon sequences of loess-palaeosol record (cold to warm climatic cycles) spanning the last 2.5 Ma, from which comparisons with the ice record (SPECMAP Stack to 620 ka and ODP 677 older than 620 ka) can be made (Figure 3.5; Kukla et al, 1990; Shackleton et al, 1995). High dust accumulation is indicative of cold dry glacial conditions and low accumulation of warm humid conditions. Figure 3.5 illustrates the significant increase in dust accumulation rate corresponding to expanded ice volume (high 5180), rather than with orbital insolation or with an orbitally modelled ice volume record. Shackleton et al. (1995), therefore, suggested that dust accumulation is possibly related to continental ice sheet formation rather than being controlled by insolation variations. The high-resolution loess record representing climatic variation in China has been derived from magnetic susceptibility, granulometry, sediment fabric, mineralogy, micromorphology, carbonate and organic carbon data (Derbyshire et al, 1995). China's climate is influenced by the seasonal alternations of East Asian summer and winter monsoons. The winter monsoon controls the outward transport and deposition of central Asian aeolian dust. Grain-size peaks and ages in the loess record match those of the last six Heinrich events (Heinrich, 1988) and are interpreted as the changing strength of the winter monsoon. 58 Figure 3.3: Vostok time series and ice volumes from Petit et al (1999). (A) Deuterium record as a function of depth expressed as 5D (in %o with respect to Standard Mean Ocean Water, 18 18 SNOW). (B) 5 Oatm profile. (C) Seawater 5 0 (ice volume proxy) and marine isotope Stages. (D) Sodium (Na) profile (ppb). (E) Dust profile (ppm). Figure 3.4: Vostok time series and insolation from Petit et al. (1999). (A) Carbon dioxide. (B) 18 Isotopic temperature of the atmosphere. (C) Methane. (D) 5 Oatm profile. (E) Insolation during mid-June at 65°N (Wm2). 59 Figure 3.5: Loess accumulation rate from China compared with the 8180 record (SPECMAP) stack to 620 ka and ODP 677 older than 620 ka (Shackleton et al 1995). During the last glacial there was periodic accumulation of sediment in the North Atlantic, transported by icebergs from icecaps in Greenland and North America and termed Heinrich events. These events occurred at 69 ka, 52 ka, 41 ka, 28 ka, 21 ka and 14.3 ka B.P. A smaller event occurred at 11.5 ka B.P. marked the end of the Last Glacial and lasted about 2 ka to 1 ka characterised by marked decreases in sea surface temperature, salinity and planktonic foraminifera growth (Heinrich, 1988; Broecker et al, 1992; Cortijo et al, 2000; Stocker, 2000). The Heinrich events represent meltwater associated with iceberg discharges from the Canadian Shield (Bond et al, 1992), British (McCabe and Clark, 1998), Laurentide and Fennoscandian-Greenland ice sheets (Cortijo et al, 2000). The majority of the debris originated from north of Hudson Bay (Gwiazda et al, 1996). While Heinrich events have overall been studied extensively in the North Atlantic Ocean, other oceanic basins also illustrate similar rapid climatic changes (Behl and Kennett, 1996; Schulze/a/. 1998). Prevailing surface water currents during the LGM transported the icebergs across the North Atlantic Ocean. In the North Atlantic the polar front and the Gulf Stream were farther to the south, there was an anticlockwise cold-water circulation in the North Atlantic Ocean, thus surging of the ice sheets must have caused the sedimentation associated with Heinrich events (Leuschner and Sirocko, 2000; Maslin, 2000; Stocker, 60 2000; Cortijo et al, 2000). During the Last Glacial, the deep-water conveyor belt was reduced supporting a cooler climate and the heat exchange between the northern and southern hemispheres is almost balanced. The deep-water circulation is not confined to an individual hemisphere or ocean basin and the North Atlantic deep-water (NADW) could be traced as far as the North Pacific (Stocker, 2000). However, during Heinrich events, melting icebergs produced freshwater input decreasing the surface density of the North Atlantic resulting in the cessation of deep-water accumulation. As a result, this reduced the heat transfer northwards so that the southern hemisphere 'stole' heat from the northern hemisphere, resulting in a colder climate in the North Atlantic region and warmer conditions in the southern hemisphere. When the Heinrich eventsfinished, ic e melting decreased, the deep water circulation restarted and heat was then transferred back to the northern hemisphere warming that part of the Earth while the southern hemisphere became cool (Leuschner and Sirocko, 2000; Maslin, 2000). Heinrich events were also associated with recurring episodes of cold North Atlantic surface water known as Bond cycles (Bond et al, 1992) lasting on average 15 ka to 10 ka associated with cold air temperatures over Greenland and Antarctic icecaps. Dansgaard-Oeschger cycles known as high-frequency climate oscillations (Dansgaard et al, 1971, 1982, 1993) occurred between 34 ka and 17 ka lasting 2 ka to 1.5 ka. Dansgaard-Oeschger cycles are associated with Heinrich events indicating climate variability over both hemispheres. Recent findings by Leuschner and Sirocko (2000) illustrate that both the Heinrich events and Dansgaard-Oeschger cycles have a global signature from numerous global records, with subtle differences between Greenland and Antarctica and the forcing mechanism or mechanisms still unknown (Jouzel et al, 1995; Blumer etal, 1998). The mechanisms for climatic variability during the last glacial is uncertain. Heinrich (1988)first suggested that these oscillations were linked to half-precessional cycle and therefore to insolation variations. This hypothesis however has been rejected and glaciological models have been proposed (Cortijo et al, 2000) and suggest that internal processes of the Earth's climatic system that are independent of orbital therories have driven these climatic oscillations. 61 Heinrich events have a signature in the Chinese loess record that is consistent with the glacial climatic data from the North Atlantic, implying that the North Atlantic and Chinese climates were linked by westerly winds (Porter and An, 1995). The loess record also shows a high degree of similarity to the warm interstadials recorded in the ice cores from Greenland and Antarctica, and with Heinrich events in the North Atlantic during the last glacial. Bond cycles are also evident within the Chinese loess records (Chen et al, 1997). Furthermore the decrease in loess from China coincides with wetter conditions (increase in fluvial activity) during OI Stages 7 and 5 from the Lake Eyre basin and southeastern Australia. During OI Stage 3 reduced loess deposits from China is associated with fluvial activity in southeastern Australian along the Riverine Plain (Page et al, 1991; Nanson et al, 1992a), and high water levels in ephemeral lake systems of southeastern Australia (Bowler, 1986). The last glacial (OI Stage 2) was characterised by an increase in loess in the Chinese sequence which coincides with dune building in Australia (Wasson 1983a, 1986; Bowler, 1986; Callen and Nanson, 1992; Magee and Miller, 1998) and in the Innamincka region during this time. The high-resolution northern hemisphere continental record of Quaternary climate from the Chinese Loess Plateau has therefore made a useful comparison with other Quaternary Australian terrestrial records, such as those from this study of Cooper Creek near Innamincka. 3.4 MIDDLE TO LATE QUATERNARY RECORD FOR AUSTRALIA Landforms caused by aridity in Australia formed during the last -2 Ma and illustrate evidence of Quaternary climatic oscillations represented by cycles of wetting and drying, that are responsible for many changes in the present landscape (Bowler, 1976, 1982, 1983, 1986; Bowler et al, 1976, 1998, 2001; Chappell, 1991; Wasson and Donnelly, 1991; Harrison, 1993; Nanson et al, 1992a; Magee etal, 1995; Williams etal, 1998). Analyses of stratigraphy and sedimentology, and the development of new dating techniques including TL and OSL, have resulted in an increased understanding of Quaternary environmental changes in Australia. The Lake Eyre basin covers about one seventh of the continent and extends from the monsoon tropics to the temperate zone, and, as such, provides wide spread evidence of terrestrial climatic change. 62 3.4.1 Tropical Northern Australia In tropical northern Australia, Nanson et al. (1993) found alluvium from Magela Creek near East Alligator River (Figure 1.1) to date from OI Stages 7 and 5, suggesting enhancedfluvial conditions. Nanson et al. (1993) suggested that the same monsoonal conditions that formed the Magela Creek deposits are linked with the extensive Katipiri Formation identified in the Lake Eyre basin. Nanson et al. (1988, 1992a) record of changes in flow regime in the Channel Country of western Queensland is also evidence for the source of these flows originating in the tropical north of the continent. Their data shows pronounced fluvial activity during Stages 7, 5 and to a lesser extent Stage 3. Alluvial deposits from the Gilbert River in the Gulf of Carpentaria (Figure 1.1; Nanson et al, 1991) provide additional evidence of widespreadfluvial activit y during OI Stages 5 and 3. Additionally, in northwestern Australia, Wende et al (1997) found evidence for enhancedfluvial activit y on Cabbage Tree Creek in the east Kimberley at about 37 ka (subpluvial Stage 3) and a return tofluvial activit y in the Early to Middle Holocene between 12 ka and 5 ka. Therefore the Quaternary climatic record obtainedfrom fluvial deposits from northern Australia indicates enhancedfluvial activit y during OI Stages 7, 5 and 3. The most detailed palynological evidence for Quaternary climatic changes in tropical northern Australia is from Lynch's Crater on the Atherton Tableland, Queensland (Figure 1.1). The pollen record shows that rainforests appear to have peaked at certain times during OI Stages 5 and 3, and the Early to Middle Holocene (Figure 3.6; Kershaw, 1983; Hiscock and Kershaw, 1992). Additionally, Kershaw et al. (1993) conducted a pollen and charcoal analyses of Ocean Drilling Program (ODP) Site 820 off the northeastern coast of Queensland, a sequence believed to cover from -1.3 Ma to the present. The vegetation pattern did not change significantly throughout this record, although there were minorfluctuations tha t are possibly related to climate change and sea level. Kershaw et al. (1993) found that the most significant change in the Site 820 record occurred between 500 ka to 100 ka with the regional replacement of a drier rainforest by open sclerophyll vegetation. This change corresponds with a similar change fromfire-sensitive tofire-promoting vegetatio n at Lake George in southeastern Australia (Singh, 1981). Kershaw et al. (1993) concluded that this could support a case for Aboriginal burning with their arrival in Australia between 500 ka and 100 ka. 63 Alternatively or additionally it could suggest significant drying of the northeast parts of the continent over that period. z i i *° *" LIJSJ x - £l iS S^ * g 3 i >.: -ess IS E s| *§ «jS -3 ? * S I b || §1 I KSWXfl ||| i| i| 3 fip sisfi/ E ns>2 .o 5 Bj 7i i do " (/>< 5. »MUM O o.' •500^50025003500. 6 200 400 600 COMPLEX RAINFOREST SCIEROPHYLL WOODLAND ARAUCARIAN RAINFORESI COMPLEX RAINFOREST ARAUCARIAN RAINFOREST LIU COMPLEX RAINFOREST C.1IOC o ago 4i?o ego i is So re 160 ***** Figure 3.6: Pollen diagram from Lynch's Crater, northeastern Queensland illustrating the major features (Kershaw etal, 1983). At Lake Woods in the Northern Territory (Figure 1.1), large strandline deposits, which define a former lake, indicate a major Late Quaternary expanded lacustrine phase. These strandlines are composed of red quartz sands that rise up to 12 m above the present lake floor (Bowler et al, 1998). The site provides new information on hydrologic response to changes in the monsoon during at least the last full glacial cycle. Bowler et al (1998) identified several major lacustral stages dating back to the Early Pleistocene. Additionally, three palaeo-shoreline ridges associated with interglacial conditions have been dated using TL, optical luminescence and photo-transferred luminescence techniques. The oldest ridges date from 180 ka (OI Stage 7) and 96 ka (OI Stage 5). 64 Drying occurred between 96 ka and 60 ka returning to lacustral conditions from about 60 ka to 30 ka. By 30 ka, the region had become drier, followed by aeolian longitudinal dune formation in arid Australia and the Cooper Creek region near Innamincka. In contrast to the previous evidence of a drier climate in northern Australia during the past 30 ka, ridges and terraces deposited at the base of waterfalls at Waterfall Creek and Wangi Falls in northern Australia (Figure 1.1), provide evidence of extreme flooding from 30 ka to 18 ka possibly associated with the strengthening of the northwest monsoon despite lower sea levels at that time (Nott and Price, 1994, 1999; Nott et al, 1996). The result is contradictory evidence as to whether the period just prior to the LGM was dry or wet. The pollen record from Lynch's Crater suggests that rainfall was lower than at present, which Kershaw (1978) stated was a response to a reduction in rain-bearing southeast trade winds. In contrast, Nott and Price (1994, 1999) and Nott et al (1996) argue for increased mobility of the polar highs and increased precipitation. They suggest two possible mechanisms. Thefirst is that the wet phases were associated with an active monsoon trough or dissipating tropical cyclones were more intense than those of the Middle Holocene. Alternatively, they suggest that broadening of lows off Western Australia across to northern Queensland could have increased rainfall by producing a stronger temperature gradient between the poles and equator. Due to more intense high-pressure systems, the tropical cold fronts could have displaced the heat trough farther north into a moister air mass resulting in convection. It is possible that high-pressure systems were more active during the LGM, causing the monsoon to intensify in northern Australia, contributing to extreme flooding and the formation of plunge pools in the Northern Territory. The Gilbert River in Queensland also provides convincing evidence of the Early Holocene being wetter than the Late Holocene in northern Australia (Nanson et al, 1991). The plunge pool evidence shows a decline in flooding from about 18 ka until the Early to Middle Holocene (10 ka to 5 ka) when the area became wetter again (Nott and Price, 1994, 1999; Nott et al, 1996). This Early to Middle Holocene increase in the effective precipitation signal was also identified by (Shulmeister, 1992, 1999; Shulemister and Lees, 1995) from pollen evidence from northern Australia and is attributed to the intensification of the northern Australian monsoon. The enhancement of Walker Circulation around 5 ka, which resulted in the intensification of the monsoon, was 65 attributed to a combination of an increased polar-equatorial pressure gradient, the intensification of the mid-latitude westerlies and the trade winds in the southern hemisphere (Shulmeister, 1992, 1999; Shulmeister and Lees, 1995). There is generally agreement that northern Australia was relatively dry in the Late Holocene, with Wende et al (1997) providing evidence of enhanced aeolian activity in the west Kimberley. 3.4.2 Centra! Australia 3.4.2.1 Fluvial and Lacustrine Evidence The Late Tertiary and Quaternary history of moisture changes in central Australia can be inferred from sedimentation in Lake Amadeus, a large groundwater discharge basin (Figure 1.1; Chen et al, 1991, 1993). The lake is composed of two major units, the Uluru Clay and overlying Winmatti Beds. The Uluru Clay is estimated to be over 5 Ma and the Winmatti Beds has a basal age of 910 ka (Figure 3.7). The clay was deposited in a shallow lacustrine and fluvial environment where the conditions were predominantly saline and dry. The transition from Uluru Clay to Winmatti Beds (910 ka) indicates major hydrological changes from a surface water dominated system to a groundwater- controlled playa (Chen et al, 1993). Chen et al. (1993) states that the Uluru Clay and Winmatti Beds are comparable with the Blanchetown Clay and Tyrrell Beds of the Murray basin (An et al, 1986) to be discussed in Section 3.4.3, representing major depositional events. The period of high watertable that formed the youngest gypseous dune dated between 60 ka to 45 ka (Figure 3.7) from Lake Amadeus is possibly associated with the high lake levels between 55 ka and 40 ka in southeastern Australia. Aridity and dune formation in the Amadeus region appears to have occurred earlier than in southeastern Australia (Chen et al, 1991, 1993). Aeolian sand deposition followed the younger gypseous dune formation during a regionally drier period at Lake Amadeus and Lake Lewis (Figure 1.1) with dune building peaking between 23 ka and 21 ka (Chen et al, 1995). This drier period is possibly associated with the low lake levels (25 ka to 16 ka) of southeastern Australia (Lake Willandra), central Australia (Lake Frome) and the dune building episodes in central Australia (Cooper Creek and Strzelecki Desert). Playa Surface i L ::::$:$$& ^^8^9^^,^K®^^>^Kv85l Winmatti Beds ;:>Xv:v:v:; 60 ka to 45 ka :•;•:;:•:;:;:;:•:;:•:•:;: XZtf'tffif/^:-^:':;:-:/;'^ | 730 ka •I'X'X'X^'X'X'X'XV^ 1 • 910 ka Uluru Clay lllll Uluru Clay 'v Gypsum :£'::• Light Grey Sand Red Sand •••; Sandy Clay Figure 3.7: Lake Amadeus sediments illustrating the eight major stratigraphic units in the Winmatti Beds (core AM3) overlying the Uluru Clay. TL dates of the youngest gypseous dunes cluster between 60 ka and 45 ka. The palaeomagnetic results indicate an uncertainty of the Bruhnes-Matuyama boundary between the gypsum and sandy clay units (modified from Chen et al. 1993). Note: stratigraphic units are not drawn to scale. The Lake Eyre basin provides evidence of past fluvial activity, with Nanson et al. (1992a) illustrating that both Cooper Creek and the Diamantina River were much more active during OI Stages 7 and 5 than is presently the case. Along the channels of the Cooper and Diamantina, extensive alluvial sand deposits are buried beneath 3 m to 2 m of overlying mud, resulting in two groupings of alluvial TL dates (Nanson et al, 1992a). Large meandering sand-load channels (Katipiri Formation) correspond to OI Stages 7 and 5, while OI Stage 6 represented a period of limited fluvial activity. Towards the end of the OI Stage 5 pluvial period, the large meandering sand-bed channels were replaced by numerous low-energy anastomosing and braided streams, transporting mud rather than sand. The TL dates from these muddy sediments range from 85 ka to modern corresponding to a period of increasing aridity and aeolian activity. Additionally, Wasson (1983a,b) found evidence in the Strzelecki Desert of fluvial deposits (meandering channels) ranging in age from 23 ka to 12 ka 67 Croke et al (1996, 1998) described four major episodes of Quaternary activity spanning approximately 200 ka in the lower Neales River catchment on the western margin of the Lake Eyre basin (Figure 1.1). The Neales River catchment provides further evidence that Australia's Quaternary climate oscillated between wet and dry episodes which were linked to the interglacial and glacial cycles. Croke et al. (1996) concluded that there is a good correlation between the timing of thefluvial and lacustrine activity throughout the Lake Eyre basin, especially during OI Stage 5. The Neales catchment also indicates intermittentfluvial activity continued from around 30 ka through to the present which conflicts with Magee and Miller's (1998) evidence of a dry Lake Eyre during this time. Croke et al. (1996, 1998) represent the sole stratigraphic and chronological work conducted on the Quaternary sediments in the western catchment system of Lake Eyre. Consequently, relatively little is known of the Middle to Late Quaternary hydrology and flow regime changes of the western tributaries, and their contributions to the overall fluctuation of Lake Eyre. The work conducted by Magee et al. (1995) and Magee (1997) at Lake Eyre (Williams Point shoreline cliff and core 83/6) provides the longest continuous sequence with a number of different facies for Lake Eyre (Figure l.land Figure 3.8). A lacustral phase (130 ka to 90 ka) was identified from transgressive sand overlying the Etadunna Formation. It is possibly related to a major fluvial phase associated with the Katipiri Formation in the Channel Country (Nanson et al, 1992a) and beach ridges (+10 m AHD) south of Lake Eyre (Nanson et al, 1998). Lacustrine conditions returned to Lake Eyre around 90 ka until just prior to 70 ka, when pedogenesis correlates with beach ridges at +5 m AHD (Nanson et al, 1998), with a return to lacustral conditions again at 70 ka. Due to deflation of the playa, material from the lake floor contributed to the formation of dunes from 60 ka to 50 ka and soils began to form on the dunes. Magee (1997) and Magee et al. (1995) suggested that there was a possible return to a lacustral environment between 50 ka and 25 ka. Between 25 ka and 10 ka a thick halite crust formed during the LGM and Magee and Miller (1998) conclude that the lake was not filled during or after the LGM. Shallow lake levels returned at 10 ka and 4 ka with the partial dissolution of halite before the deposition of laminated gypseous clays, resulting in the modern ephemeral playa (3 ka to present). 68 Nanson et al. (1998) dated beachridges marginal to Lakes Eyre, Frome, Callabonna and Blanche to determine hydrological changes in the Lake Eyre basin (Figure 1.1). Beach ridges at Lake Eyre South, were dated at 111+18 ka and 88.9+15.8 ka (OI Stage 5), indicative of a high lake stand due to increased runoff from the rivers which flow into the basin from monsoonal northern Australia, combined with reduced temperature and evaporation rates. Thefilling o f Lake Eyre during OI Stage 5 is possibly due to a spillway (Warrawoocara Channel), which connected Lakes Gregory, Blanche, Callabonna and Frome to Lake Eyre. One beach ridge from Lake Frome (22 m AHD) dates from 69.6+20.6 ka and two TL dates of 70.0+15.4 ka and 62.7±6.3 ka from Lake Eyre (11m AHD) may correspond to aeolian deposition on theseridges during OI Stage 4. Five dates from Lakes Eyre and Frome (54.9±9.2 ka, 54.9+4.8 ka, 46.9+7.3 ka, 46.5+5.1 ka and 38.8+11.2 ka) indicate high lake stands during OI Stage 3 and correspond to wet phases from southeastern (Bowler, 1986; Page and Nanson, 1996; Ayliff et al, 1998) and northern Australia (Bowler et al, 1998). Additionally, three dates of 26.2+3.7 ka, 22.8+2.3 ka and 26.2+3.0 ka from Lakes Eyre and Blanche suggest high lake stands during late OI Stage 3 or early OI Stage 2 correlating with the plunge pool data in Northern Australia (Nott and Price, 1994, 1999; Nott et al, 1996). However, there are no known deposits from the floor of Lake Eyre that support high lake levels at the start of the LGM (26 ka to 22 ka). Nanson et al (1998) suggested that this 'high' lake stand is a short-lived event due to the enhanced monsoonal activity in northern Australia resulting from tropical runoff intorivers, which terminate at Lake Eyre. A major deflation episode between 60 ka to 50 ka excavated the present Lake Eyre basin and deposited gypsum and clay-rich aeolian sediments known as the Williams Point aeolian unit (Figure 3.8). After the deflation episode a thick secondary gypsum profile developed on the aeolian unit during OI Stage 3. Whereas mollusc and bird eggshells have been dated by AAR at OI Stage 5, Magee and Miller (1998) suggested that the shells might have been reworked from older deposits. The AAR results of Magee and Miller (1998) conflict with Nanson et al. (1998) OI Stage 3 TL date from the beach ridge (+5 m AHD). A total of 40 AMS radiocarbon dates (Magee and Miller, 1998) from Shelly Island (aeolian unit) and aeolian sediments close to Lake Eyre indicate a dry phase dating from 35 ka to 10 ka. These OI Stage 2 dates conflict with Nanson et al 69 (1998) ages of 01 Stages 3 and 2 from the Lakes Eyre and Blanche beach ridges. From 10 ka to 4 ka there was a minor lacustral phase, and from 4 ka to 3 ka the modern ephemeral playa regime formed (Magee and Miller, 1998). The period between 23 ka and 15 ka saw the construction of gypsum lunettes and islands within Lake Frome and longitudinal dunes surrounding the lake in the Strzelecki dunefield (Wasson and Donnelly, 1991), indicating aridity in the Lake Frome and Strzelecki Desert areas. Lake level metres Dry mAHD Full AHD Williams Point -3 6-i _J_ 4- I I I ! I I I I 1 I I I I ll Deflation? , \ :*t4444*4**-i\ii: -*-50ka •\ti*.*.:\V-:tt*.*.i '•:•**•'?'••'• *?:•*&/:•* j *.*!=: • f *j "' 4 tf&i Lake or playa 0- marginal dune :•:•:: 58 ka -2- Deflation i u,y ••« .viji»/• A,WP.••. • v J Beach L HJTO^^S SS zCoquin a r 9 Deflation? I4*V*VA A*V * * A mf+\ X iBsE? 69 ka Oscillating -6- saline and >**•***** biackish deep v .f: n TTT :: TWT: rri -.-rrrrr 111 and shallow -8 - lacustrine rii Figure 3.8: Summary log of Williams Point section and Core 83/6 with a palaeo-lake level curve after Magee et al (1995). The dates have been reported from thermoluminescence and amino acid racemisation. A Late Quaternary salinity record was produced by Ullman and McLeod (1986) at Lake Frome from the analysis of Na+ in gypsum. It indicated three periods of high lake levels from 17 ka to 11 ka, and drying prior to 17 ka, between 16.5 ka and 13 ka, and 6 ka to 70 4 ka. This contradicts Bowler et al. (1986) who used radiocarbon dating that suggests an early lacustral phase prior to 18 ka giving way to aridity and aeolian activity, and then becoming wetter from 16 ka to 13 ka before returning to an arid phase. Lake water levels were low between 13 ka to 10 ka and remained similar through the Holocene (Draper and Jensen, 1976; Colhoun, 1991). Palynological evidence indicates that Lake Frome was predominantly dry prior to 9.5 ka with wet conditions from 9.5 ka to 8 ka and 7ka to 4.2 ka (Singh, 1981). The Early Holocene (7 ka) saw the drying and formation of playa facies with a brief return to lacustrine conditions between 6 ka and 4 ka and continuing as a playa to the present (Colhoun, 1991). The present lakeshore dunes began to form at 2.5 ka and a slight increase in shrubland occurred around 2.2 ka (Colhoun, 1991; Wasson and Donnelly, 1991). 3.4.2.2 Aeolian Evidence The age of dune deposits in central Australia provide further evidence of climate change in the Late Quaternary. Early work by Crocker (1941, 1959) and Browne (1945) viewed Pleistocene climate as much wetter than present, with the Australian deserts the result of a Middle Holocene arid phase. Mabbutt (1967), Folk (1971) and Langford- Smith (1983) argued that the Simpson dunefield is essentially of Pleistocene age and that the dunes are therefore relict features with contemporary sand transportation being minor, restricted to some reworking of the dune crests. Using stratigraphic and chronological data from the Strzelecki and Simpson dunefields, Wasson (1983a, 1986) found that the last major phase of dune construction occurred during the LGM between 22.3 kaB.P. and 12.5 kaB.P. However, there must have been dunes in the Simpson Desert at various times in the Middle Pleistocene as evidence from a dune dated at 274+22 ka near the Diamantina River by Nanson et al. (1988). The application of TL dating of aeolian sediments (Wasson, 1983a,b; Gardner et al, 1987) has provided a greater understanding of the age of Australian continental dunefields. TL dating of the Katipiri Formation (fluvial sediments) that underlies large areas of the Simpson and Strzelecki dunefields, ranges between 125 ka and 85 ka and indicates that most of the dunes there must be younger than that (Nanson et al, 1992b, 1995). Longitudinal dunes near Birdsville were deposited by around 80 ka and reworked during even the Holocene, with considerable dune activity occurring at or near the LGM 71 (Callen and Nanson, 1992; Nanson et al, 1992b). The transition from a dominantly fluvial phase to an arid phase is supported by alluvium containing indurated calcretes, ferricretes and gypcretes that gave a mean U/Th age of 102.9+3.5 ka, and the TL dating of aeolian sediments indicating dune deposition commencing at approximately 95 ka (Nanson et al, 1992b). TL dating of the dunefield in western Simpson Desert by Nanson et al. (1995) also supports the findings from Birdsville suggesting that source- bordering dunes there were formed as early as 100 ka. Wasson (1983a), Callen et al (1983) and Gardner et al. (1987) provide the most detailed evidence for aeolian Pleistocene activity in the southern section of the Lake Eyre basin. In the Strzelecki Desert in particular aeolian deposits have been dated between 23 kaB.P. and 13 kaB.P. with two phases of Late Holocene dune activity, one at 3 ka B.P. to 2 ka B.P. and a present mobile phase (Wasson, 1983a,b). 3.4.3 Southeastern Australia The Riverine Plain in southeastern Australia (Figure 1.1) is the result of prolonged Cainozoicfluvial activity (Brown and Stephenson, 1991). The Murray-Darling River system once flowed into a large lake called Lake Bungunnia (Figure 3.9), which existed from the Middle Pleistocene. Tectonic damming of the Murray River outlet by the uplift of the Padtheway Horst controlled the lake producing a sequence of lacustrine clastic sediment (Figure 3.9; An et al, 1986). Palaeomagnetic reversal analysis from sections at Chowilla and Lake Tyrrell was applied to Lake Bungunnia sediments to establish their chronology and therefore to determine the age of the major hydrologic transition from the expansive freshwater system to the saline playas and dunes, which form the present landscape (Figure 3.9; An et al, 1986). Lake Bungunnia deposits consist of two principal lithologic units: the Blanchetown Clays and the Woorinen Formation (Figure 3.10). The bedded Blanchetown Clays occur in sections up to 30 m in depth and represent an essentially permanentfreshwater lak e until about 700 ka. The calcareous dunes of the Woorinen Formation overlie these clays and were deposited within the last 700 ka. The transition from Lake Bungunnia to the present arid landscape took place between 700 ka and 400 ka (Figure 3.10; An et al, 1986), however the lake disappeared due to downcutting of the outlet channel sometime after the Brunhes-Matuyama boundary. Lake Bungunnia deposits therefore provide a 72 link between the retreat of the ocean during the Late Tertiary, the formation of silcrete- lateritized weathering profiles that formed on the marine sands and the aeolian deposits formed during the Quaternary that dominate the present landscape (Figure 3.10). NEW SOUTH WALES Figure 3.9: The extent of Lake Bungunnia in southeastern Australia illustrated by the thicker dashed line and the location of the two sections (Chowilla and Lake Tyrrell) used for palaeomagnetic analyses (An etal, 1986). Thermoluminescence dating of Riverine Plain sediments by Page and Nanson (1996) revealed four phases of palaeochannel activity between 105 ka and 12 ka. These include the Coleambally Phase (105 ka to 80 ka) during OI Stage 5; the Kerarbury Phase (55 ka to 35 ka) during OI Stage 3; the Gum Creek Phase (35 ka 25 ka) during OI Stage 2 prior to the LGM and the Yanco Phase (20 ka to 13 ka) during OI Stage 2 post LGM. The Coleambally and Kerarbury Phases were characterised by large palaeochannels with greater discharges than the present river. The Gum Creek and Yanco Phases also indicated pronounced fluvial activity and larger discharges than at present, but these 73 deposits are not so laterally extensive as the former two phases. Additionally, during the Yanco Phase after the LGM, source-bordering dunes formed and reworking of the Riverine Plain. Figure 3.10: Schematic stratigraphic summary of the Murray Basin units. Silcrete-lateritized weathering profiles developed on the marine sand (Parilla Sands) are overlain by Lake Bungunnia (Blanchtown Clay and Bungunnia Limestone) sediments. Surficial deposits consisting of aeolian and saline lake deposits discomformably overlie the lacustrine sediments, which form the present landscape (modified An et al. 1986). Note: stratigraphic units are not drawn to scale. High lake levels recorded at 55 ka to 32 ka for Lakes Willandra, George and Tyrrell, and approximately 30 ka for Lake Frome (Bowler, 1983, 1986; De Deckker, 1986; Colhoun, 1991) and beach ridge formation at Lakes Eyre and Blanche all correspond to palaeochannel activity on the Riverine Plain (Page and Nanson, 1996). They are evidence of OI Stage 3 being at times, considerably wetter than the Holocene. The growth of speleothems has been used as an indicator of warmer and wetter conditions, especially in arid or semi-arid regions. At the Naracoorte Caves in South Australia (Figure 1.1), speleothems have been dated using thermal ionisation mass spectrometry (TIMS) providing an extended palaeoenvironmental record for 74 southeastern Australia. Ayliffe et al. (1998) document four main growth periods: 420 ka to 340 ka, 300 ka to 270 ka, 220 ka to 155 ka, and 115 ka to 20 ka, broadly corresponding to the stadials and interstadials of the past four glacial cycles and indicating high precipitation phases during this these times. In more detail over the last full glacial cycle, speleothem deposition occurred at 115 ka to 105 ka, 100 ka to 90 ka, 85 ka to 70 ka, 50 ka to 40 ka, and 35 ka to 20 ka broadly corresponding to wet phases within OI Stages 5 and 3. Willandra Lakes is a chain of lakes connected by a distributary (Willandra Creek) of the Lachlan River and marks the western extent of the Riverine Plain in semi-arid southeastern Australia (Figure 1.1 and Figure 3.9) located close to the summer-winter rainfall boundary on the plains of the Murray basin (Bowler, 1986). During the Late Pleistocene, Willandra Creek flowed as a distributary of the Lachlan River from the southeastern highlands into the Mallee dunefield area of the present day Willandra Lakes system. The lakes system reflects a characteristic asymmetry from west to east associated with the prevailing wind direction and deflation. The removal of sediment from the west formed lakeshore lunettes in the east, providing evidence of past environmental changes (Bowler and Smith, 1996). Luminescence dating (TL) conducted by Bowler (1998) and Bowler and Price (1998) have provided a more reliable chronology for Willandra Lakes than the radiocarbon chronologyfirst carried out by Bowler (1981). The five major stratigraphic units recognised from lacustrine sediments of Lakes Mungo, Mulurulu and Outer Arumpo (including the Mungo I and Mungo III burial sites) are: the Golgol unit (126 ka to 98 ka), a major palaeosol representing a long period of non-deposition, the Mungo unit (40 ka to 35 ka) representing a high freshwater lake level phase, the Arumpo unit (35 ka to 22 ka) representingfluctuating water levels leading to a major dry phase represented by the Zand unit (20 ka to 19 ka) followed by the Mulurulu unit (19 ka to 17 ka) that involved the return of lake full conditions to the Willandra Lakes system (Bowler, 1981; Bowler, 1998; Bowler and Price, 1998). The Golgol unit is recognised as the same period as the widespread occurrence of palaeosols in the cores of lunettes across the Riverine Plain (Bowler and Price, 1998), and as a period of palaeochannel activity in the Murray basin recognised by Page and Nanson (1996). The Mungo unit consists of lakeshore quartz sands indicative of a major deep-water phase associated with freshwater shells throughout the Willandra Lakes 75 region and is represented on the Riverine Plain as the Kerarbury wet phase. The initiation of pelletal clay facies in the region and dust accretion at around 35 ka in the Arumpo unit indicates regional drying andfluctuating wate r levels. An equivalent period of palaeochannel activity is recognised by Page and Nanson (1996) on the Riverine Plain represented by the Gum Creek phase whenfluvial activit y was not as pronounced as in the earlier Coleambally and Kerarbury phases. Major drying and deflation represented by the Zanci unit (post LGM) at Willandra Lakes, has also been recognised previously at other ancient lakes throughout the Murray basin at this time by Bowler (1976) and Magee (1991). The presence of freshwater facies (quartz sand dunes and beach sands) represented by a 3 m to 4 m lunette between 19 ka and 17 ka, marks a short-lived return of freshwater to the Willandra Lakes system after the Zanci drying. It roughly corresponds to the Yanco Creek phase of fluvial activity on the Riverine Plain (20 ka to 13 ka), although it appears to have been of shorter duration. Bowler (1998) suggested that the absence of pelletal clay facies during this time at Willandra Lakes is probably the result of a changing local groundwater regime, where freshwater was available in this part of the lake system. Since about 15 ka, Willandra Lakes has only experienced occasional flooding (Bowler, 1998). 3.5 CONCLUSION The climatic changes that occurred during the Quaternary on the Australian continent are evident in the stratigraphy and chronology of Quaternary deposits in northern, central and southeastern Australia. Interglacials were marked by the deposition of deepwater lacustrine clays (Lake Eyre), shoreline sands (Lake Woods), beach ridges (Lakes Eyre, Frome, Callabonna and Blanche) and river terraces of abundant alluvial sands and gravels and large meandering channels in the Lake Eyre and Murray basins. Glacial periods in Australia are associated with deflation of lake sediments (Lake Eyre), the construction of clay lunettes (Willandra Lakes), and the formation and the reworking of dunes (Strzelecki and Simpson Deserts). Australia appears to have had a much wetter climate in the Middle Quaternary becoming drier in the Late Quaternary, with therivers becoming less efficient. It is clear that OI Stages 7, 6, 5 and 3 were generally wet stages. Early OI Stage 4 seems to be dry, but then becomes wet by mid OI Stage 4. Evidence from northern Australia suggests that OI 76 Stage 3 was a less pluvially active stage than previous interglacials, whereas in southeastern Australia Stage 3 consisted of two major phases of increased flow regime. At present, the Holocene is much drier than the previous interglacials of OI Stages 7 and 5 and this remains an interesting but as yet unexplained contrast. This thesis provides further evidence of major climatic change in central Australia, adding to the very substantial existing body of research. 77 CHAPTER 4 METHODS 4.1 SITE SELECTION AND SAMPLE COLLECTION PROCEDURE The major depositional environments (alluvial, aeolian and lacustrine) were initially identified using LANDSAT TM images (bands 5, 4 and 3) and topographic maps. This survey was then followed by extensivefield investigations . The criterion used to select field sites was based upon locating and sampling palaeochannels of both Cooper and Strzelecki Creeks, often difficult to identify buried beneath contemporary floodplain sediments on the Cooper, and beneath the Strzelecki dunefield. The location of sampling sites are illustrated in Figure 1.3 and Figure 1.4. In order to determine how the alluvial history of the region correlates and possibly interacts with aeolian landforms, the depositional history of source-bordering dunes, lunettes and longitudinal dune formation was a primary objective in site selection. In particular, dunes adjacent to Strzelecki Creek and the palaeochannels of Cooper Creek were selected for detailed investigation. Additionally, sampling of the chronostratigraphy of lacustrine and aeolian sediments took place in the Coongie Lakes region where the flow from the Cooper presently terminates in most years. Field sampling of sediment was conducted using a truck mounted Gemco 210D drill rig, hand augering and trench excavation. The depth of each auger hole was determined by the capacity of the drill rig or the hand auger to penetrate the various units. Whenever a recognisably different facies was encountered in outcrops or auger holes, sediment samples were taken. All sediment samples were collected in sealed plastic airtight bags. Along the northwest branch of Cooper Creek, at Scrubby Camp, 'Aarpoo' and Marpoo Waterholes (Figure 1.4), the exposed cut-bank sections were sampled for TL dating and sediment analysis. At Tilcha Waterhole (Figure 1.4) stepped trenches were excavated into the eroded bank to expose fluvial sediments overlain by a series of aeolian and palaeosol units. The Gemco 210D power auger was used at Cullyamurra Waterhole and Wills Grave (Figure 1.3 and Figure 1.4) to obtain samples for TL dating and sedimentological analyses, since compared to hand augering this method was quicker and could reach greater depths than a hand auger. 78 The crests of longitudinal and source-bordering dunes located in the Strzelecki Desert (West and East Mudlalee), Turra, Gidgealpa Dune, Innamincka Racetrack, Coongie Lakes and a lunette located at Lake Marroocutchanie (Figure 1.4) were all hand augered. A hand auger was also used to sample alluvial sediments from Strzelecki Creek at Mudlalee and Merty Merty (Figure 1.3). Samples from these sites were taken for TL and sedimentological analyses. TL samples were either collected either by hammering a steel or PVC tube into an exposed outcrop or by collecting from a power auger or hand auger. In the case of auger samples, every care was taken to shield the sample from direct sunlight. A black plastic sleeve was slid over the auger as it was withdrawn from the ground, and the sample was removed in darkness. The sample was then wrapped in black plastic and sealed for later analyses. A full outline of the TL laboratory procedures for the University of Wollongong lab is provided in Shepherd and Price (1990) and Nanson et al (1991). 4.2 THERMOLUMINESCENCE (TL) DATING One of the major aims of this thesis is to establish a Quaternary chronology of Cooper Creek (near Innamincka), Strzelecki Creek, Coongie Lakes and the Strzelecki dunefield. At the time of fieldwork and data analyses (1996-1998) the dating method most suitable for obtaining an extensive chronology of the landforms of the area was thermoluminescence. David Price conducted all thermoluminescence dating performed in this study at the University of Wollongong's TL laboratory. The optically stimulated luminescence (OSL) dating technique was not used in this study since the OSL laboratory at the University of Wollongong had not been established when this thesis was undertaken. Future research prior to publication of the results obtained here will include OSL dating of aeolian and especiallyfluvial sediment s taken from the same sedimentary units dated to assess the accuracy of the TL dates obtained. In this regard, preliminary OSL results obtained by Dr Deba Banerjee are producing very similar ages to those obtained by TL from both fluvial and aeolian sedimentary units. At this point in time all crosschecks using OSL on alluvial sediments have verified the TL ages where the TL characteristics have been classed as good. 79 4.2.1 Summary of the TL Dating Technique Luminescence emission following thermal stimulation is termed thermoluminescence. The basic theory and background to the technique is outline by Aitken (1974, 1985, 1990) and Wintle and Huntley (1982). The following provides a summary of the TL dating technique and its application in earth sciences with a potential to provide a chronology for aeolian and fluvially transported quartz and felspathic minerals as far back as 500 ka years (Aitken, 1985), and a summary of the methods used in the Wollongong laboratory. Aeolian sediments from warm desert environments are very suitable for luminescence dating since aeolian sediment transport processes allow the luminescence signal for grains to be minimised or perhaps reset (i.e. exposed to the sun) prior to burial, thus giving accurate ages for the deposition of the sediment (Clarke et al, 1999; Stokes, 1999). In contrast, alluvial sediments undergo water transportation, often very turbid in this region, and these sediments are less likely to be exposed to sufficient sunlight to minimise the luminescence signal. Therefore, the potential for errors in dating alluvial sediments is greater than for aeolian sediments (Berger, 1988; Clarke et al, 1999). Thermoluminescence dating has been widely used and accepted as a dating technique for both alluvial and aeolian sediments throughout Australia's arid-zone. For example Wasson's (1983a,b, 1986) work in the Strzelecki dunefield; Gardner etal (1987) in the Simpson and Strzelecki dunefields; Nanson et al. (1988, 1992a,b) in the Channel Country and Chen et al. (1990, 1991, 1995) at Lake Amadeus (southwest Northern Territory). Thermoluminescence dating allows the age of sediment deposition to be established for a wide range of sedimentary environments, as stated by Stokes (1999). Thermoluminescence dating indicates the time interval since quartz grains were last exposed to sunlight, which minimises any prior TL signal (i.e. the energy stored in the form of trapped electrons). After burial, the quartz grains are subjected to radiation from naturally occurring radioisotopes of uranium ( U), thorium ( Th) and potassium ( K), with a small contribution from cosmic rays and from the presence of rubidium resulting in an accumulation of trapped electrons (Aitken, 1985). Quartz is one mineral that has the ability to store electrons in a reliable fashion over long periods of time (500 ka years). The electrons accumulate within the crystalline mineral subject to continuous irradiation. 80 This stored energy can be released in one of two ways. Firstly, by natural exposure to ultra-violet or visible light and secondly, by controlled heating under laboratory conditions. In the laboratory this thermally stimulated emission of light from crystalline minerals following the previous absorption of energy from ionising radiation is thermoluminescence (Aitken, 1990). Thermoluminescent data are plotted as the intensity of light emitted by the sediment as the sample is heated from room temperature through to approximately 500°C, which is sufficient to release all of the electrons which give rise to a TL spectrum. This glow curve is indicative of the natural TL properties of the minerals. The TL intensity is dependent upon three factors: one, the ability of crystals to trap electrons which is dependent upon the crystalline lattice imperfections; two, the radiation dose rate of that environment; and three, the time of burial. Therefore, if TL sensitive minerals are present in a sedimentary sample and the radiation dose rate can be calculated, then the time elapsed since sample deposition can be determined. Thermoluminescence dating of sedimentary deposits is based upon the assumption that exposure to sunlight during transportation by wind or water, removes the previously acquired TL from the minerals. A small amount of TL remains in the minerals at the time of burial and this is termed the 'residual' TL. Upon burial the minerals reacquire TL at a rate dependent on the environmental radiation dose rate and to a level determined by the length of burial. Therefore, the time since the sediment was last exposed to sunlight is determined by measuring the total amount of TL energy absorbed since deposition (the palaeodose), and the rate at which the energy was acquired (the annual radiation dose) give by the following equation: TL Age = Palaeodose / Annual Radiation Dose The palaeodose is the 'natural' TL less the residual TL that represents the total amount of TL energy absorbed and stored since deposition. The annual dose is the rate at which this energy is acquired (Aitken, 1985, 1990). The methodology used at the University of Wollongong TL laboratory follows the general procedure outlined in Aitken (1985, 1990) and Nanson et al. (1991). The combined regenerative/additive method described by Readhead (1984, 1988) is utilised for evaluating palaeodose and uses the TL signal 81 from the 90 urn to 125 uin quartz fraction of the sediment. Annual dose rates were estimated in the Wollongong TL laboratory. The uranium and thorium specific activity determinations were measured by calibrated thick source alpha counting over a 42 mm scintillation screen. Potassium was measured using atomic absorption spectroscopy at the University of Wollongong's Chemistry Department. The radiation dose was computed using equations derived by Readhead (1984). The TL results are presented in Appendix 1. 4.3 PARTICLE SIZE ANALYSIS Particle size analysis by sieving is the most widespread method used for the analysis of gravel-size and sand-size sediment. The advantage of sieving is that it works with relatively large samples, which is important for preparative procedures and error analysis (Bernhardt, 1994). Aggregated samples were gently ground using a mortar and pestle to break down large aggregates and to provide maximum surface area for physical and chemical treatment. Care was required not to break the individual clasts and grains during this process. Large fragments of organic material were picked out and calcium carbonate nodules were removed with hydrochloric acid prior to any sedimentological analysis. The samples were split and oven dried, then placed in an ultrasonic bath in order to break down any fine matrix and aggregates. The size distribution of the silt and clay fraction (<63 pm) was determined using a Hariba Cappa-700 particle size distribution analyser. The sand-size and larger sediments (63 um to 4000 urn) were determined by a combination of wet sieving to remove the fines and dry sieving thefraction large r than 63 nm using nested sieves at half phi (((>) intervals (Appendix 2 and Appendix 3). Grain-size parameters of mean grain-size, inclusive graphic standard deviation, inclusive graphic skewness and kurtosis, for each individual sample were calculated using Grainsize® software. Bivariate plots and a two-tailed t-test, p=0.05 were carried out to determine whether different facies had significantly different sediment characteristics, and whether sediment transported by wind differed significantly in character to that transported by water. This was achieved by using the parameters of mean grain-size and inclusive graphic standard deviation (Appendix 4, 5, 6 and 7). The sediment samples were divided according to seven major depositional environments found in the study 82 including: lower palaeochannel, upper palaeochannel, overbank deposits, source- bordering dune, dune surface sands, lunette sands and diagenetically altered sand (diagenetic refers only to reworking of wind pellets). Both the grain-size analysis and statistical tests of the major depositional environments are discussed in Chapter 5. 4.4 SCANNING ELECTRON MICROSCOPE (SEM) Quartz sand grains obtained from alluvial, aeolian and lacustrine environments were examined using a Stereoscan 440 Scanning Electron Microscope (SEM). The aim was to observe if there were recognisable differences betweenfluvial, aeolian and lacustrine environments or evidence indicating the origins or sediment transport process between these groups. Prior to examination with the SEM, the samples were pre-treated with 10% hydrochloric acid (HCl) and 5% stannous chloride (SnCl2) and placed in an ultrasonic bath (these processes do not alter the surface grain features) to remove any coating on the sand grains, washed with distilled water, oven dried (<40°C), coated with gold and mounted on disks (refer to Bull, 1986 for further details regarding preparation of samples for SEM analysis). The results of this work are discussed in Chapter 5. 4.5 X-RAY DIFFRECTION AND MINERALOGY X-ray diffraction was used for the identification of minerals in the clay-size sediments from this study area. The method used by the University of Wollongong to identify the mineralogy of samples is described in Hutchinson (1974). X-ray diffraction was carried out using a Philips PW 1150 diffractometer using a copper broad focus X-ray tube at 40 keV and 30 mA. X-ray diffraction using untreated samples, glycerol solvation and heating to 500°C was carried out on selected clay samples. Diffractograms were obtained with CuKa radiation over the range 4° to 20° for clays. The mineralogy was identified using Traces® and UPDSM software and the clay diffraction patterns were reported in terms of interplanar spacing (d spacings). Sediment samples from the major depositional environments were also prepared for thin section analysis. The variables used for this analysis were mineralogical composition, matrix material, sand-size clay aggregates, roundness and iron oxide or haematite coating of sand grains. A cluster analysis program was used to determine clustering or grouping between individual samples and their related environments (Appendix 9 and 10). 83 The colour of the alluvial, aeolian (longitudinal and source-bordering dunes) and lacustrine sediments was determined on wet samples using a Munsell Colour chart, tabulated in Appendix 8. 84 CHAPTER 5 DIFFERENTIATING MAJOR DEPOSITIONAL ENVIRONMENTS USING SEDIMENT CHARACTERISTICS 5.1 INTRODUCTION The correct identification of fluvial, aeolian and lacustrine environments from sedimentary characteristics utilises grain-size statistical parameters which provide the researcher with a method for understanding the depositional conditions of each environment. However, despite numerous papers pertaining to this area of research, there is still no clear, definitive method which enables researchers to confidently differentiate between various depositional environments of sands using statistical techniques alone (Boggs, 1987). This chapter reviews the sedimentary grain-size parameters (mean grain-size and standard deviation), sediment colour, mineralogical composition (clay mineralogy and petrographic interpretation) and quartz grain surface features of sediments obtained from alluvial, aeolian and lacustrine environments in the Cooper Creek area near Innamincka. The combination of these different parameters provides a better basis to identify which depositional environment a sample originated from. The Quaternary stratigraphic sequences within this study area contain a number of major depositional environments which have been classified as channel sediments (lower and upper palaeochannels and overbank); source-bordering dunes; dune surface sands; diagenetically altered sediments and lunette. Samples were collected predominantly from known depositional environments which included alluvial, aeolian and lacustrine. The alluvial sediments were separated into lower and upper palaeochannel sediments and overbank deposits based on their grain-size analyses. These distinctions of the alluvial sediments are for sediment comparison and there is no suggestion, at any point in the study area, that these three alluvial environments were not part of a single palaeochannel system. Here, the lower palaeochannel sediments probably represent bed-load sediment, while the upper palaeochannel deposits consist offiner sedimen t and are probably the source material for the formation of source-bordering dunes in the region. The source- bordering dunes were formed of alluvial sand derived from the channels during seasonal low flow and are aligned as transverse dunes roughly west-east and parallel to the palaeochannels (Figure 1.3 and Figure 1.4B). Longitudinal dunes in the region, which 85 trend northwards, have been derived from the older and higher source-bordering transverse dunes (Figure 1.3 and Figure 1.4B). Sediment grain-size analyses have allowed the aeolian dunes to be differentiated into dune surface sands and diagenetically altered sands. The dunes from this study are unusual in that they contain sand-sized clay aggregates/pellets that have since been broken down by pedogenesis, altering sediment texture. Consequently, the fines from these samples had to be removed and the remaining portion of these samples examined as a separate group. Surface crestal samples from aeolian dunes were investigated so that they could be compared with the work mostly conducted on surfaces of dunes elsewhere in the world. These samples have not been diagenetically altered. Throughout this chapter diagenesis refers to alteration of the mud pellets and not to other diagenetic processes such as ferruginisation or carbonisation. Additionally, sediments from the lunette (Figure 1.4A) are mainly composed of quartz-grain sand formed during high water phases when sand is worked by wind and inner shore drift to the leeward end of the lake and then blown into the lunette, similar to present coastal dunes. Thus, the lunette sediments have also been analyses to help determine the depositional history of lunettes in the Coongie Lakes region and its link with the northwest branch of Cooper Creek. A cluster analysis was performed to determine any textural or compositional similarities or differences between the major depositional environments. This was followed by Scanning Electron Microscopic (SEM) study of quartz-grain surface features from each major facies. The results of this chapter, along with the thermoluminescence dates presented in Chapter 6, provide valuable information for interpreting the palaeoenvironmental history of the region over the past -250 ka. 5.2 GRAIN-SIZE PARAMETERS OF ALLUVIAL SEDIMENTS For grain-size analysis, the fluvial sediments in this study have been differentiated according to the following broad environments identified in the field: (1) lower palaeochannel sequences consisting of coarse bed-load material; (2) upper palaeochannel sequences consisting of medium tofine-textured sand ; (3) overbank deposits. The mean grain-size and standard deviation (sorting) of these three groups were analysed as two groups: the sandfraction ( 4 <|) to -2 <|)) and the full grain-size (14 q> to —2 and Appendix 3). Bivariate plots were constructed for each of these three sedimentary environments to help in differentiating and interpreting grain-size parameters of fluvial sediments (Appendix 4 and Appendix 5). 5.2.1 Lower Palaeochannel Sediments A total of 8 samples from lower palaeochannel sediments were obtained from Wills Grave (Figure 5.1; WIL1-1, 2-4, 2-5 and 2-6), Cullyamurra Waterhole (Figure 5.2; CUL1-2), Gidgealpa South (Figure 1.4B; GSP1-1) and Mudlalee palaeochannel (Figure 5.3; MUP1-2 and 4-2; Appendix 4 and Appendix 5). Mean grain-size ranges from coarse tofine-grained san d (0.58 Figure 5.1: A schematic cross-section across the northwest branch of Cooper Creek showing the location of Wills Grave (27°46'45"S, 140°36'35"E) Auger Holes 1 to 4 where samples for sediment analysis were obtained. Comparing the full analysis to the sand fraction for the lower palaeochannel sediment samples, the data did not show any significant differences in mean grain-size or standard deviation (sorting) for the Cullyamurra Waterhole and Wills Grave samples. The only samples that showed any significant differences in mean grain-size and standard deviation after removing the fines were Gidgealpa South (GSP1-1) and Mudlalee palaeochannel (MUP1-2 and MUP4-2). These particular samples contained 34% to 8% fines, whereas 87 the Cullyamurra Waterhole and Wills Grave samples contained 3% to 2% fines (Appendix 2 and Appendix 5). Figure 5.2: A schematic cross-section across Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) showing the location of Auger Holes 1 to 4 where samples for sediment analysis were obtained. West Mudlalee Dune Auger Hole East Mudlalee Dune Auger Hole A Mudlalee Channel and 00MM1^K Overbank Section /: \ AHl AH2 AH3 AH4 / \ ii i i / 11111k :q:::q:::q:iii:i:::c::!:rv Fluvial Sediments I i j r ; Figure 5.3: A schematic cross-section across Mudlalee channel and overbank section (Strzelecki Creek 28°16'43"S, 140°29'33"E) located between West Mudlalee (28°16'29"S, 140°27'34"E) and East Mudlalee (28°16'00"S, 140°31'45"E) dune sites showing the location of auger holes where samples for sediment analysis were obtained. 5.2.2 Upper Palaeochannel Sediments A total of 72 samples were taken from what were believed to be upper portion of the palaeochannel sequences with the mean grain-sizes ranging from medium sand to medium silt size (1.01 c|) to 5.97 (J>) and the standard deviations ranging from well sorted to very poorly sorted (0.35 or the Cooper 'fan' (Figure 1.4B; 52% to 13%) sites. The overall higher proportion of mud in the upper palaeochannel samples compared to lower palaeochannel samples reflects the greater preservation potential of low flow deposits in upper part of the channel succession. This is also reflected in the lower mean grain-size and slightly improved sorting in the upper palaeochannel deposits (Appendix 3 and Appendix 5). The lower percentage offines alon g the northwest branch suggests that more clean sand was being transported and reworked by high-energy flows here than along Strzelecki Creek or the Cooper 'fan'. 5.2.3 Overbank Deposits A total of 15 samples were collected as overbank sediments on the Cooper 'fan' (Figure 1.4B), along the northwest branch (Figure 1.4B) and along Strzelecki Creek (Figure 1.3). This suggests a change over time from a system of mixed-load channels to mud-dominated overbank deposits across the region as a whole. The mean grain-size of the full analysis ranged from fine sand to fine silt size (2.20 5.2.4 Sand-Sized Clay Aggregates Nanson et al. (1986, 1988) found that some of the alluvial mud in the Channel Country (Figure 1.1; Cooper Creek, Diamantina and Thomson Rivers) occurred in the form of sand-sized mud aggregates. Much of the mud on thefloodplain is in the form of sand- sized mud aggregates whose formation is attributed to the wetting and drying of swelling clay such as smectite. In contrast, Bowler (1973) and Wasson (1983a,b) suggested that clay pellets formed as a result of desiccation of mud and rising saline groundwater. However, Nanson et al (1986, 1988) concluded that as the salt concentrations of the Cooper are low (< 200 ppm), salt is unlikely to be a requirement in forming clay aggregates in these fluvial conditions. Sand-sized clay aggregates/pellets have been observed in abundance in thefluvial sediment s of Cooper Creek and Strzelecki Creek 89 near Innamincka. Their presence in small proportions in nearby dunes suggests that they have probably blown out of channels and off thefloodplains during dry periods or times of seasonal variation and have become deposited in the dunes (Section 5.3 and Section 5.4). 5.3 GRAIN-SIZE PARAMETERS OF SOURCE-BORDERING DUNES 5.3.1 Source-Bordering Dune Sediments A total of 16 samples were obtained from source-bordering dunes in the area, including Tilcha Waterhole (Figure 5.1), Turra and Gidgealpa Dune. Mean grain-sizes range from fine to veryfine-grained sand (2.23 § to 3.77 §) typical of aeolian sediments. Standard deviations range from moderate to very poorly sorted (0.75 (j) to 2.57 When the fines were removed, not unexpectedly the mean grain-size of the sand fraction increased and sorting improved, reflecting the significance of sand-sized clay aggregates and fines in these dunes as a major sedimentary characteristic (Appendix 3). Overall, the percentage fines seem to increase slightly down the profile for Tilcha Waterhole but remained fairly constant for the Turra source-bordering dune site (Appendix 2). Insufficient samples were collected from Gidgealpa dune to make comparisons down the auger hole. The mean grain-size of the upper palaeochannel sediments (Turra fluvial) located adjacent to the source-bordering dune (Turra source-bordering) ranged from coarse to very fine-grained sand (0.82 (j) to 3.26 (|>). In comparison, the mean grain-size sand fraction of the source-bordering dune samples wasfine-grained sand (2.21 (j) to 2.69 (()). This leads to the conclusion that the coarser sand in the upper palaeochannel samples has not been transported and deposited by wind into the adjacent source-bordering dune, which only containsfine-grained sand , but instead was left behind as a lag in the channel. 90 • Upper Palaeochannel Sands • Source-Bordering Dune Sands Dune Surface Sands 1 50 2.00 Mean (phi) Figure 5.4: Bivariate plot of mean grain-sizes compared to standard deviations for upper palaeochannel, source-bordering dune and dune surface sand fractions. A bivariate plot of mean grain-size verses standard deviations for upper palaeochannel, source-bordering dune and dune surface sands was produced to determine any relationships between these groups (Figure 5.4). This plot illustrates that the source- bordering dune sand and dune surface sand was probably derived from the upper palaeochannel sequences. Dust would have been blown and the sand-sized clay aggregates were transported with the medium to fine sandfraction an d deposited as part of source-bordering and longitudinal dunes for Cooper Creek and the Strzelecki dunefield. The dune surface samples generally have a slightly lower standard deviation (are better sorted) than the lower part of the dunes as a result of fewer diagenetically altered clay pellets. 5.4 GRAIN-SIZE PARAMETERS OF AEOLIAN DUNES Aeolian dune samples in the Cooper Creek area include Coongie, Iimamincka Racetrack, Turra, East Mudlalee and West Mudlalee. These sites have been classified into two categories: dune surface sediments (11 samples) and diagenetically altered dune sediments (23 samples). The dune surface sands were those samples obtained within the upper 2.0 m of the dunes, while the diagenetically modified sands were located below the surface sands and above the contemporary floodplain. 91 5.4.1 Dune Surface Sediments The mean grain-sizes of dune surface sediments to the depth of 2.0 m below dune crests throughout the region were fine-grained aeolian sand (2.12 (() to 2.84 ()>; Appendix 2). When the sand fraction alone was analysed for the dune surface samples, it was found that the mean grain-size increased slightly, ranging from 2.05 (J) to 2.66 1999), Simpson Desert (1.89 2.90 Pell et al. (2000) found that the mean grain-size of dunes located east of Strzelecki Creek arefine-grained sand (2.02 (j) to 2.39 (j>) and those west of Strzelecki Creek are also fine-grained sand (2.05 (J) to 2.27 (EMD1-1) dune sampled in this study had a mean grain-size of 2.43 (j) and the dune west of Strzelecki Creek (WMD2-1) had a mean grain-size of 2.51 (J). While the dune surface samples from Strzelecki Creek in this study have slightly finer mean grain-sizes in comparison to the data from Pell et al (2000), the results of both studies are consistent. The dune surface samples including the fines gave sorting values from 0.55 (j) to 1.94 (J>, indicating that the dune crests for the region are moderately well sorted to poorly sorted (Appendix 4). The poor sorting of the dune sands is a function of the quantity of silt- clay present in the samples. These fines probably represent disaggregated mud pellets that have been blown out of the channels and floodplains and deposited as part of the source-bordering dunes and longitudinal dunes throughout the area, as well as dust blown onto the dunes during dust storms. Some of the sand-sized clay pellets have probably become disaggregated by wetting within the dune. Those remaining readably disaggregated in the laboratory during grain-size analyses when the samples were subjected to ultrasonic pre-treatment. This indicates that the existing clay pellets within 92 the dunes were probably not formed in situ, but rather deposited by aeolian processes during dune formation. The clays are poorly crystalline and mixed-layered and they break down over time to a diagenetic clay matrix within the dune. The sand-sized clay aggregates make these particular dunes in the Strzelecki Desert unusual examples of poorly sorted aeolian deposits. 2.50- 2.Q0 JE a. B 1-50 X Lunette Sands O • S3 n • X • Dune Surface Sands > • Source-Bordering Sands Q • ^x •o 5 ' oo • Diagenticaiiy Altered Sands E s 0.50 • 0.00- -1 50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4 0 0 Mean (phi) Figure 5.5: Bivariate plot of mean grain-size verses standard deviation for dune surface, diagenetically altered dune, source-bordering dune and lunette sand fractions. For the sand-sizefraction, th e standard deviation of the dunes ranged from moderately well sorted to moderately sorted (0.54 § to 0.76 §; Figure 5.5), which is typical for aeolian sands (Appendix 5). This supports the assumption that dunes in this study area contain of a high percentage of sand-size mud pellets (6.2% to 0.2% counted) and silt- clay (18% to 2% by weight) content which determines the sorting characteristics of the disaggregated dune surface sands. The two dunes located adjacent to Strzelecki Creek (samples WMD2-1 and EMD1-1) have the highest percentage of clay pellets (4.4% and 6.2%). This suggests that the sand-sized clay pellets formed during long dry periods caused by infrequent flooding down Strzelecki Creek, indicating that the majority of the flow in the region has been along Cooper Creek rather than down Strzelecki Creek. 5.4.2 Diagenetically Altered Dune Sediments Much of the previous research conducted regarding mean grain-size characteristics of aeolian dunes in the Kalahari, Simpson, Strzelecki and Tiari Deserts (Folk, 1971; 93 Lancaster, 1981, 1986; Wasson, 1983a,b; Livingston etal, 1999; El-Sayed, 1999; Pell et al, 2000) concentrated on samples taken from dune crests (0.50 m to 0.10 m). To determine how mean grain-size is related to position on the dune, this study obtained samples from aeolian dunes at various depths, ranging from 11.30 m to 1.0 m. These samples are therefore representative of the complete stratigraphic and geomorphological history of the dunes in this region of Cooper Creek. Part of this history has been the diagenetic alteration of the dune deposits. A total of 23 diagenetically modified dune samples were obtained from longitudinal dunes within the study area. The mean grain-size ranged from medium grained sand to coarse silt size (1.66 (moderately well sorted to poorly sorted) (Figure 5.5; Appendix 3 and Appendix 5). Removing the fines (<63 urn) and undertaking just a sand fraction analysis, the diagenetically altered dune sands were found to be better sorted and typical of dune sands. The fines in these modified dune samples are attributed to diagenetic processes such as the in situ break down of clay aggregates, the addition of floodplain clay by infiltration in the lower parts of the dune during flooding, the addition of aeolian dust, and the breakdown of disaggregated clay pellets from within the dune. The possible destruction of feldspar and/or lithic grains during diagenesis and the pealing off and disaggregation (during grain-size analyses) of iron oxide coatings and clay cutans attached to the dune sands also contributes to an increase infines i n these dunes. The results of the mean grain-size analyses conducted on diagenetically altered sediments showed that samples become slightly coarser grained with depth, suggesting either that wind may only be able to transport coarser material a short distance up the dune or that winds were stronger in the past when older and deeper parts of the dune were formed. Additionally, the diagenetically altered sand might have a thicker grain coating of clay than other dune sands making grains larger. At Coongie, Turra, East Mudlalee and West Mudlalee, the proportion offines also increases with depth. The West Mudlalee (32% to 94 8% fines) and East Mudlalee (48% to 16%fines) dune sites had the highest percentages of fines (Appendix 2). The increase in fines with depth resulted in the sorting being poorer towards the base of the dunes and might be a function of reworking within the dune profile. 5.5 GRAIN-SIZE PARAMETERS OF LUNETTE The mean grain-sizes for the Marroocutchanie lunette (MAR2-1 to MAR2-5) were fine grained sand (2.57 (|) to 2.95 ({>), with the standard deviation ranging from moderately well sorted to moderately sorted (0.75 § to 0.91 4>) typical of aeolian deposits. However, for sample MAR1-2 the mean grain-size was coarse silt (4.43 ((>; Appendix 2 and Appendix 4) with a standard deviation of 2.89 (j) (very poorly sorted). This particular sample was taken from the same general location but from the remnants of an older lunette located 120 m to the south of the present day lunette. With the removal of fines the mean grain-size and standard deviation of samples MAR2-1 to MAR2-5 were not significantly altered (Appendix 3 and Appendix 5). However, sample MAR1-2 (the older lunette) had a very high percentage offines (28%) and the removal of fines from the sample significantly altered both the mean grain-size and sorting, with the results being similar to samples MAR2-2 to MAR2-5. The higher percentage offines in sample MAR1-2 is possibly due to the older lunette being located closer to the lake. The stratigraphy of the lunette, shown in Chapter 6, suggests that a younger aeolian unit has formed downwind of the original lunette. The fines would have originated as pellets deflated from the lakebed and deposited beside the lake. 5.6 TWO-TAILED T-TEST Further statistical analysis, including a two-tailed t-test (P=0.05) was performed on the grain-size analysis for the complete samples (14 The two-tailed t-test (P=0.05) for the mean grain-size concluded that there was no statically significant difference (i.e. accepting the null hypothesis) between the mean grain-sizes of upper palaeochannel sediments and dune surface sediments, and that 95 diagenetically altered dune sediments, dune surface sediments and source-bordering dune sediments have statistically similar mean grain sizes to lunette sediments (Table 5.1 and Table 5.2). The t-test however rejected the null hypothesis at the 95% confidence interval between dune surface sediments and source-bordering dune sediments and diagenetically altered sediments. This rejection might possibly be associated with the inadequate number of samples from dune surfaces to statistically justify any accurate conclusions, or due to the higher sand-sized clay aggregate content and better sorting of dune surface samples when compared with the diagenetically altered and source- bordering dune sediments. Complete Sand Fraction Samples Mean St.Dev Mean St.Dev Landforms liiil Lower Palaeochannels m w 1.79 (n = 8) 1.01 0.55 1.24 Upper Palaeochannels (n = 72) 2.39 1.46 1.93 0.79 Overbank (n = 15) 4.23 2.25 2.55 0.83 Source-Bordering 2.87 1.61 2.44 0.72 Dunes (n = 16) Diagenetically Altered 3.14 1.90 2.37 0.83 (n = 23) Dunes Surface 2.52 1.09 2.40 0.63 (n = 11) Lunette (n = 6) 2.96 1.25 2.63 0.48 Table 5.1: Mean grain-sizes and standard deviations of the major depositional environments used to perform a two-tailed t-test (P=0.05) assuming unequal variances. When performing a two-tailed t-test (P=0.05) on the sand fraction of the major depositional environments, the mean grain-size analysis concluded that diagenetically altered sands, source-bordering dune sands, dune surface sands and lunette sands could possibly be derived from floodplains since there was no significant difference in mean grain-sizes (Table 5.1 and Table 5.3). That is, the sand located within channel splays located on thefloodplains has been blown out to form aeolian features in this region. 96 Diagenetically Source- Mean Grain- Lunette Dune Surface Overbank Upper Altered Dune Bordering Size Sediments Sediments Deposits Palaeochanne Sediments Sediments 1 Sediments Lower Palaeochannel Reject Ho Reject Ho Reject Ho Reject Ho Reject Ho Reject Ho Sediments Upper Palaeochannel Accept Ho Reject Ho Accept Ho Reject Ho Reject Ho Sediments Overbank Reject Ho Deposits Reject Ho Reject Ho Reject Ho : :;:;:Souree*:::;: :ii Bordering Accept Ho Accept Ho Reject Ho ;:• Sediments i-Dune Surface Accept Ho Reject Ho Sediments Diagenetically Altered Dune Accept Ho Sediments j: Table 5.2: Two by two table construction of the two-tailed t-test (P=0.05) performed on the 14 § to -2 t}> mean grain-size analysis of the major depositional environments. Diagenetically ]]-: Source- : . Upper Mean Grain- Lunette Dune Surface Overbank Altered Dune Bordering Palaeochanne Size Sands Sands Sands Sands ::::..':Sands: 1 Sands ••::::::::1LoweiT:^ Palaeochannel ! Reject Ho Reject Ho Reject Ho Reject Ho Reject Ho Reject Ho :::;:::;,:Sah(f8.:i::': Upper Palaeochannel Reject Ho Reject Ho Reject Ho Reject Ho Reject Ho Sands Overbank Accept Ho Accept Ho Accept Ho Sands Accept Ho Bordering Reject Ho Accept Ho Accept Ho DuneSurface ^Sarid*..;:. Reject Ho Accept Ho Diagenetically Altered Dune Reject Ho Sands Table 5.3: Two by two table construction of the two-tailed t-test (P=0.05) performed on the sand fraction (4 ([) to -2 <))) mean grain-size analysis of the major depositional environments. 97 The statistical test also rejected the null hypothesis in that the mean grain-size of lunette sands is significantly different from source-bordering, diagenetically altered and dune surface sands (Table 5.3). The lunette contains morefines and has probably been derived from the lake floor either by wind or wave action, rather than from channels or floodplains as is the case for source-bordering and longitudinal dunes. 5.7 SEDIMENT COLOUR Munsell colour indices were examined for those samples classified asfluvial and aeolian sediments across the Cooper Creek region near Innamincka (Appendix 8). The fluvial sediments on the Cooper 'fan' area range in hue from 2.5 Y to 10 YR. Specifically, Turra palaeochannel sediments all have a hue of 2.5 Y ranging from pale yellow, yellow, light grey and white with the yellows dominating. The samples taken from the Turra and Gidgealpa dune sites were found to be generally pale and clean with little mud content. In contrast, the North Dog Bite Lake palaeochannel samples were muddy with a hue of 10 YR. Thefluvial sediment s buried beneath the Turra longitudinal dune site were also muddy, like the North Dog Bite Lakefluvial sediments, with a hue of 10 YR. Along the boundary of Strzelecki Creek, the fluvial sediments located beneath West Mudlalee dune have a hue index range between 2.5 Y to 10 YR and those buried beneath East Mudlalee dune, range from 5 YR to 10 YR. Thefluvial sample s at Mudlalee palaeochannel range in hue index from 2.5 Y to 10 YR with a few of the samples being white or pale yellow with no mud or clay present. The Merty Merty channel sediments, located farther south along Strzelecki Creek, have a hue index range of 2.5 Y to 10 YR. The northwest branch fluvial samples from Tilcha Waterhole, Wills Grave and Marpoo Waterhole all had a hue of 10 YR, except for "Aarpoo" Waterhole which had a hue of 2.5 Y. The hue of the source-bordering dune sites and lunette samples ranges between 2.5 YR and 10 YR, but are generally 10 YR. The palaeosols located at Tilcha Waterhole are an intense red colour of 2.5 YR hue to 5 YR (yellow). These samples lie within the same hue range as that found for longitudinal dune samples located in the Cooper 'fan' area and those reported by Pell et al (2000) and Wasson (1983a). 98 Munsell colour indices were examined for longitudinal dunes across the study area. Regionally, hue index ranges from 2.5 YR to 10 YR, generally being 7.5 YR north of Innamincka and 10 YR south of Innamincka. However the dominant group is 10 YR, which is probably related to the larger sampling density from the south of Innamincka. Longitudinal dune samples located along the western boundary of Strzelecki Creek are 7.5 YR to 10 YR becoming paler with depth. Longitudinal dune samples along the eastern boundary of Strzelecki Creek range between 5 YR and 10 YR, being mainly 5 YR. Pell et al (2000) found that samples takenfrom crests of dunes (depth of 5 cm to 10 cm) east of Strzelecki Creek show hue of 2.5 YR to 5 YR, while those west of the creek are 7.5 YR, which is consistent with previous work by Wasson (1983 a). The hue index of longitudinal dunes located in the Cooper 'fan' area is 10 YR, but ranges from 7.5 YR to 10 YR. Generally, the longitudinal dunes located in the Cooper 'fan' area and along the boundary of Strzelecki Creek are predominantly 10 YR suggesting that sands have been derivedfrom the transverse dunes that were formed from the palaeochannels. 5.8 MINERALOGICAL COMPOSITION 5.8.1 Clay Mineralogy (Standard X-Ray Diffraction Analyses) The mineralogy of 18 clay-separates from the major depositional environments was examined using X-ray diffraction (XRD), with the results presented in Table 5.4. These samples were chosen to investigate the clay mineralogy and to determine the origin and transport history of unconsolidated sediments in the study area. All the samples are dominated by quartz with feldspar, muscovite and calcite often being the principle additional minerals present. Clay minerals (kaolinite and montmorillonite) form only a minor component, with the dominant detrital clay mineral in the study area being illite. Montmorillonite forms in magnesium-rich environments under moderate leaching (alkaline) conditions from igneous rocks containing plagioclase felspars, volcanic ash and basalt. The montmorillonite clays in the study area are poorly crystalline mixed-layer clays derived from the modern Cooper Creek waters and are bought infrom the black soil plains (basalt) in Queensland (B. Jones pers. comm., 2000). The distribution of montmorillonite is determined by modern floodwaters through the Innamincka Dome and onto the Cooper 'fan', forming part of the Turra longitudinal dune and North Dog Bite Lake 2 andflowing alon g the northwest branch to Coongie Lakes (Table 5.4). In the 99 latter area it was noted that inter-layered illite-montmorillonite dominated over kaolinite (Table 5.4). These results are consistent with previous work by Wasson (1983b) who reported kaolinite, illite and mixed-layer illite-montmorillonite in the Cooper Creek region and Strzelecki Desert. Site Name Sample Number XRD Mineralogical Analysis Quartz, Feldspar, Kaolinite, Illite and Turra Longitudinal Dune 2 S2-2 Montmorillonite. Turra Longitudinal Dune 2 S2-4 Quartz, Montmorillonite and Kaolinite. Turra Longitudinal Dune 6 S6-2 Quartz, Kaolinite and Illite. Turra Longitudinal Dune 6 S6-3 Quartz, Illite and Kaolinite. Turra Longitudinal Dune 6 S6-4 Quartz, Kaolinite and Illite. Turra Longitudinal Dune 4 S4-2 Quartz, Illite and Kaolinite Turra Longitudinal Dune 3 S3-4 Quartz, Calcite and Kaolinite. Turra Palaeochannel 4 S4-1 Quartz, Kaolinite and Illite. Turra Palaeochannel 4 S4-2 Quartz, Illite and Kaolinite. Quartz, Feldspar, Montmorillonite and Turra Palaeochannel 4 S4-4 Kaolinite. Quartz, Feldspar, Montmorillonite, Kaolinite Coongie Longitudinal Dune S1-4 and Calcite. Quartz, Calcite, Kaolinite, Illite and Coongie Swale S1-5 Montmorillonite. Quartz, Feldspar, Kaolinite and North Dog Bite Lake 2 S2-1 Montmorillonite. North Dog Bite Lake 2 S2-3 Quartz, Kaolinite, Montmorillonite and Illite. Will's Grave 4 S4-4 Quartz, Kaolinite and Illite. Cullyamurra Waterhole 1 S1-5 Quartz, Calcite and Kaolinite Mudlalee Palaeochannel 2 S2-2 Quartz, Kaolinite and Calcite. Tilcha Waterhole S2-11 Quartz, Calcite and Kaolinite. Table 5.4: XRD clay mineralogy from different depositional environments within the study area. Illite is known to be abundant in temperate and semi-arid areas world wide, the result of weathering of potassium feldspar-rich rocks and micas under alkaline weathering conditions. Illite can also come from metamorphic rocks and be reworked from earlier illitic sediments. The illitic clays in the study area are poorly crystalline due to the wetting, drying and leaching in the desert environment. Much of the illite and kaolinite have originated from the erosion of Early Mesozoic and Tertiary strata such as the Winton and Eyre Formations found in the Lake Eyre basin. 5.8.2 Petrographic Interpretation The variables analysed from a total of 64 samples from the major depositional environments include quartz, metaquartzite, feldspar, zircon, chert, rock fragments, opaque minerals, clay pelletsA (counted as part of the mineralogy), haematite cement, clay pellets8 (counted separately), iron coating (relative scale) and roundness of grains (rho scale; Appendix 9). There was no difference in quartz content between aeolian (97.0% to 85.5%) and fluvial (97.5% to 84.5%) sequences. Quartz is resistant to 100 chemical weathering, whereas other minerals, like feldspar (0.5 % to 0.0 % of aeolian andfluvial sediments , respectively), tend to be altered to clay minerals. This results in an increasing relative abundance of quartz over time. The more angular and larger fluvial quartz grains were found within Strzelecki Creek and along the northwest branch of Cooper Creek. Thefluvial sediments of the Cooper 'fan' area consisted of smaller quartz grains that had been broken down and fractured due to mechanical and/or chemical weathering processes. After quartz, the next dominant component is metaquartzite (metamorphic quartzite) making up 10 % to 0.5 % of aeolian sediments and 9.5 % to 0.5 % offluvial sediments. Rock fragments (sandstone, siltstone, schist and mudstone) make up 6.5 % to 0.0 % of aeolian sediments and 7.5 % to 0.0 % offluvial sediment s (Appendix 9). Metaquartzite, some rock fragments and chert (consisting of nearly pure microcrystalline silica) are known to survive transportation and abrasion under high-energy environments but, none theless, are still subject to further breakage after deposition such as post-depositional chemical weathering (Friedman and Sanders, 1978). Rock fragments and chert were found in all of the depositional environments with the chert content in both fluvial and aeolian sediments being only 1.5 % to 0.0 %. This similar mineralogical composition for both the aeolian and fluvial sediments suggests that they were derived from a similar source. Feldspars were found throughout the region in all of the major depositional environments and the provenance of the feldspars might be either igneous or metamorphic. The feldspars display diagnostic twinning (polysynthetic or multiple twinning in cross- polarized light) and are identified as plagioclase feldspars possibly derived from basalt. The feldspars, including weathered single crystals, became more rounded by transport than quartz grains of comparable size since feldspar is a softer mineral. Additionally, feldspar is prone to breakage and is thus less likely to survive numerous cycles of weathering than quartz. Zircon was identified in thin sections and comprised 0.5 % to 0.0 % of the grains in both aeolian and fluvial sediments (Appendix 9). Zircon, a stable heavy mineral, can survive multiple recycling and is commonly rounded. Zircon was only found at two aeolian sites, 101 Turra and Innamincka Racetrack, whereas in the fluvial sites it occurs at Turra, Gidgealpa South and Cullyamurra Waterhole. Haematite cement was identified at Turra and Tilcha Waterhole in aeolian sediments but only at Gidgealpa South in fluvial sediments. Haematite cement is the mineral responsible for the red colour of the terrigenous red-beds, such as the Innamincka Red-beds of the Lake Eyre basin. Haematite precipitates under oxidizing conditions, forming at or near the sediment-water interface and is known to be stable under reducing conditions at moderately high pH levels (Boggs, 1987). Haematite is also known to act as a replacement mineral and haematite cements are very common in siliciclastic sedimentary rocks. In order to determine any significant difference between aeolian and fluvial sediments in relation to iron oxide coating/haematite cement of grains, the grains were ranked according to how red the sediments were under thin section analysis, such that a rating of 0 indicates no coating, 1 very little coating up to a rating of 5 indicating that the grain is heavily coated in iron oxide/haematite (Appendix 9). It can be seen in that the majority of aeolian samples have a rating of 1 and are only slightly coated in iron oxide/haematite cement. However, the longitudinal dunes located along the west and east boundary of Strzelecki Creek, at Innamincka Racetrack, Tilcha Waterhole and Coongie Lakes had an iron oxide rating between 3 and 5. The aeolian samples from Tilcha Waterhole (S2-6 and S2-7) had the highest rating of 5. In comparison, there were only 7fluvial sample s which had any iron oxide/haematite coating on the surface on the grains, and were rated 1 to 4. These coated quartz grains, both aeolian and fluvial, also contain cupules entrapping the iron oxide this colour refracts throughout the grain and gives the quartz a distinctive red/brown colour. Roundness (rho scale) basically measures the shape of sediments and is an estimate of the smoothness of the surface of a grain. The roundness of sand-size particles was determined by matching the outlines of individual particles to the roundness scale that contains six classes: very angular, angular, sub-angular, sub-rounded, rounded, and well rounded and is reported as a rho scale (Folk, 1955). The shape of sediments is controlled by their parent rock and their sedimentary history of transportation, deposition, mechanical and chemical weathering. For example, quartz, zircon and chert are less rounded during transportation than feldspars and their roundness is more readily preserved through several cycles of sedimentation. 102 The roundness of aeolian sands was found to have a rho range between 2.85 p to 4.20 p (Appendix 9). The aeolian sediments in this study are more angular than those found in other desert regions of the world, which indicates that the sand grains have been fairly rapidly deposited in the dunes and have not been transported back and forth, thus preserving their angularity. The roundness offluvial sediments ranged from 3.1A p to 4.85 p, essentially the same shape as aeolian sediments but slightly more rounded (Appendix 9). Roundness is also a function of grain size with larger grains rounding more rapidly than smaller ones. Fluvial sands are coarser and therefore, contain more rounded quartz. Sand-sized clay pellets or aggregates in the Strzelecki Desert were first reported by Wasson (1982) and he suggested that special watertable conditions were necessary for clay pellet formation and dune construction. However, Nanson et al. (1986) showed that an abundance of self-mulching floodplain clay-soils on Cooper Creek upstream of the 'fan' are likely to have been the source of these pellets. This study found sand-sized clay aggregates/pellets ranging in from 6.2 % to 0.0 % for aeolian sediments and 4.4 % to 0.0 % for fluvial sediments (Appendix 9). Those aeolian sediments that contained the highest percentage of sand-sized clay aggregates were located on the crests of dunes on the western and eastern boundary of Strzelecki Creek, and the Innamincka Racetrack dune located north of Innamincka on the modern Cooper floodplain. The pale dune (West Mudlalee S2-1) formed on the western boundary of Strzelecki Creek had the highest percentage of clay pellets (6.2 %), but the red/brown dune (East Mudlalee Sl-1) on the eastern boundary of Strzelecki Creek contained 4.4% clay pellets. This is in contrast with the work by Wasson (1986) who reported that the pale dunes contained large quantities of clay pellets while generally the red/brown dunes located on the eastern side of Strzelecki Creek contained none. The reason for the high percentage of clay pellets reported from the eastern side of Strzelecki Creek in this study is possibly due to this particular site being adjacent to Strzelecki Creek, which is the provenance for the sand-sized clay pellets. Clearly, clay aggregates can be reworked by wind and water as sand-sized particles. 103 Other aeolian samples that contained clay pellets (2.4 % to 0.2 %) are from sites located on the Cooper 'fan' directly adjacent to palaeochannels of Cooper Creek. Since Strzelecki Creek, the Cooper 'fan' and thefluvial plains north of Innamincka do not contain permanent water, sand-sized clay pellets can be formed by wetting and drying, and are blown out of the modern alluvium and deposited on the dunes. Additionally, the clay pellets can get broken down into dust sizes in both aeolian andfluvial environments, thus contributing to the increase in percentage offines i n both of these. 5.8.3 Cluster Analysis Cluster analysis was performed on 157 samples to identify any groupings (measure of similarity) between the various sites or environments. The variables analysed were mean grain-size (Mz), inclusive graphic standard deviation (IGSD), inclusive graphic skewness (IGS), kurtosis graphics (KG), fluvial (F), aeolian (A), rock fragments (Rockf), metaquartzite (Metaq), chert, feldspar (Felds), opaque (Opaq), zircon (Zirc), quartz (Qtz), clay pellets (A and B), roundness (round), roundness standard deviation (RndSD) and iron oxide/haematite coating (FeCot). The cluster analysis program ('Cluster.exe') reduces a set of objects to groups of objects that show a greater degree of similarity to members of their group than to members of other groups. The benefit of clustering is that identification of the clusters provides direct evidence for variations in the data. Four clusters or groups were identified from the resulting dendrogram (see Appendix 9 and 10). The cluster analysis identified four major groups that can be assessed according to their depositional environments and/or sedimentary textural analysis (mean grain-size and standard deviation). Group 1 consists mainly of aeolian sediments that are fine-grained; Group 2 consists mainly of upper palaeochannel sediments that are fine to medium- grained; Group 3 consists of fine to very fine-grained source-bordering, diagenetically altered aeolian andfluvial sediments; and Group 4 consists mainly offine-grained uppe r palaeochannel sediments. The first group contains two sub-groups, Group 1A and IB. Group 1A (Appendix 9) comprises those samples classified asfine-grained, poorly sorted dune surface sediments (East Mudlalee, Turra and West Mudlalee), source-bordering dunes (Gidgealpa Dune and Tilcha Waterhole), diagenetically altered dune sands (Innamincka Racetrack, Turra 104 and West Mudlalee), overbank (Gidgealpa Dune) and upper palaeochannel (Turra) deposits. Group IB (Appendix 9) is also composed offine grained , but moderately well sorted, dune surface sediments (Coongie Longitudinal Dune and Innamincka Racetrack), diagenetically altered dune sands (Coongie Longitudinal Dune and Turra), source- bordering dune (Turra), lunette (Marroocutchanie) and upper palaeochannel sediments (Cullyamurra Waterhole). While those samples forming Groups 1A and IB are derived from the same depositional environments, Group 1A has a higher percentage of fines (21% to 2% by weight) than Group IB (6% to 2% by weight) which is reflected in the standard deviation of mean grain-size (sorting). The largest group is Group 2A (Appendix 9) consisting of medium-grained, moderately sorted, upper palaeochannel sediments (Cullyamurra Waterhole, Gidgealpa South, Tilcha Waterhole, Wills Grave, North Dog Bite Lake and Mudlalee Palaeochannel), lower palaeochannel (Cullyamurra Waterhole and Wills Grave) and overbank sediments (North Dog Bite Lake and Wills Grave). The majority of these samples have been derived from upper palaeochannels located at Cullyamurra Waterhole and Wills Grave, and only include one sample from Strzelecki Creek (MUP1-1). Group 2B (Appendix 9) is a small dominantly fine grained, moderately well sorted, upper palaeochannel group (Cullyamurra Waterhole, Tilcha Waterhole, Wills Grave and North Dog Bite Lakes) with one overbank sample from Cullyamurra Waterhole and from North Dog Bite Lakes, and Coongie Lakes swale samples. This group contains a lower percentage offines ranging from 9% to 2% when compared with Group 2A (20% to 0%), and has afiner mea n grain-size which separates these two groups. The next group is Group 3 A (Appendix 9), an aeolian group consisting very fine-grained, very poorly sorted, mainly diagenetically altered dune sediments from West Mudlalee, East Mudlalee and Turra, and source-bordering dune samples from Tilcha Waterhole. Group 3B is similar, consisting of veryfine-grained t o silt size, very poorly sorted, upper palaeochannel (East Mudlalee, Merty Merty, Mudlalee Palaeochannel and Turra), lower palaeochannel (Mudlalee Palaeochannel), overbank (East Mudlalee, Tilcha Waterhole, Turra and West Mudlalee) and diagenetically altered dune sand (East Mudlalee, Turra and West Mudlalee) sediments (Appendix 9). These samples from Group 3B contain a very high percentage of fines ranging from 97% to 17% which affects the standard 105 deviation and, therefore, splits these two subgroups apart as a response to their depositional environments. The final group is Group 4 consisting of mainly fine-grained, poorly sorted fluvial sediments located on the Cooper 'fan' (Appendix 9). The group consists of a mixture of upper palaeochannel sediments (Cullyamurra Waterhole, East Dog Bite Lake, Gidgealpa South, Marpoo Waterhole, Merty Merty, Mudlalee Palaeochannel, Tilcha Waterhole and Turra), lower palaeochannel (Gidgealpa South and Mudlalee Palaeochannel), overbank (Turra), diagenetically altered dune sands (Turra) and source-bordering dune (Tilcha Waterhole) samples. 5.9 SEM ANALYSIS OF QUARTZ GRAIN SURFACE FEATURES Scanning Electron Microscopy (SEM) analyses of quartz grain surface features revealed evidence of mechanical and chemical processes that acted upon the grains, the preceding depositional environment, and the mode of transportation of these sediments to their present depositional environment. The SEM was utilised in this study to identify similarities or differences between fluvial and aeolian quartz grain surface features in order to assist with reconstructing the sedimentological history of the quartz sand grains. Krinsley and Donahue (1968) provided the most detailed and comprehensive study of the SEM characteristics of sand grains by examining over 400 samples and 4000 individual quartz sand grain surfaces of littoral (beach), aeolian, glacial, diagenetic and a combination of all four groups. They concluded that there are specific differences and that it is possible to distinguish between these sediments depending on the environment of transportation and deposition. Krinsley and Donahue's (1968) results are considered to be reliable qualitative environmental indicators, however they found that some environments could not be related to textural patterns on the surface of sediments because they were not related to specific mechanical or chemical processes. For example, river abrasion does not produce any distinctive textural patterns on grain surfaces, concluding that river abrasion is not sufficient to cause distinctive breakage patterns such as those found on aeolian sediments. The study by Pell and Chivas (1995) of aeolian quartz grain surfaces from the Strzelecki and Simpson Deserts found chemically precipitated features and minor mechanically 106 induced features dominated these grains. Pell and Chivas (1995) identified two different forms of chemically precipitated features. Firstly, Type I is characterised by precipitated sheets of silica, ranging in form from small disseminated globules to larger sheet structures on the grain surfaces, with little evidence of other ions. Secondly, Type II is characterised by precipitated plates with associated polygonal cracking and craters which are composed primarily of silica, along with small quantities of aluminium (<6%) and minor amounts of iron, titanium and potassium (<2%). Type II precipitation results when a clay coating is overlain by a Type I precipitated sheet. This cover acts as a barrier to chemical attack, protecting the clay coating. Thus the polygonal cracking found by Pell and Chivas (1995) on aeolian sand associated with Type II precipitation, results from the dehydration of the underlying clay layers and is not due to past climate. This effect is associated with large quantities of clay pellets within the Strzelecki Desert and, in the absence of clay, the re-precipitation of silica from pore water leads to the formation of Type I precipitated sheets. The abundance of Type II precipitated plates and associated polygonal cracking indicates that quartz grains were associated with clay-rich material, probably from the numerous salt lakes in the region (Pell and Chivas, 1995). This study however illustrated that clay pellets have been derived from theriver deposits and not as a result of lake deflation. Type I precipitation characteristics were not identified on either aeolian or fluvial quartz grains in this study, which is probably a function of the presence of sand-size clay aggregates in thefluvial an d aeolian environments. Type II precipitation, characterised by polygonal cracking, was however observed in both environments from this study and, as concluded by Pell and Chivas (1995), is associated with large quantities of clay pellets. 5.9.1 V-Shaped Etching Etch-pits appear as V-shaped patterns on the surfaces of both fluvial and aeolian quartz grains. The V-shaped etching is produced chemically (Pell and Chivas, 1995) and is the result of rapid dissolution of silica within the desert environment. These features are scattered on the rounded smooth surface of both fluvial and aeolian quartz grains in no particular orientation. The V-shaped etching has formed along the crystal planes of the quartz grain surface, etching along a crystallographic intersection (Figure 5.6A). The V- shaped patterns are three-sided, narrowing towards the grain interior and are observed to 107 be incised (chemically) into the surface of the grain. These V-shaped patterns observed on the surfaces of fluvial grains are also present on aeolian quartz grain surfaces. However, this feature is more numerous and smaller in size on the surface of aeolian grains when compare to fluvial quartz grain surfaces (Figure 5.6B). Therefore it can be concluded that these V-shaped pits are characteristic of bothfluvial and aeolian quartz grain surfaces in the study area; that there are no significant differences in the appearance of these pits on fluvial or aeolian quartz grains; and aeolian grains are essentially derived from the fluvial environment. 5.9.2 Abrasion and Roundness Under hot desert conditions sand grains go through a cycle of solution and precipitation when the grain is stationary, followed by abrasion when saltation takes place (Folk, 1978). This process is repeated and the smoothness of the quartz grain surface becomes a function of the time spent in each part of the cycle. Abrasion occurs from impact-induced fracture during transport of the quartz grains following the transfer of kinetic energy between grains (Leeder, 1982). In water, the high effective buoyancy exerted on grains and the high viscosity of the medium reduces the kinetic energy and effects of impacts on the grain surface. Wind abrasion, on the other hand, is more effective than the mechanical action of a river, due to the low viscosity of air, and is found to have a stronger abrading effect than water. The SEM work conducted in deserts has tended to show that aeolian sands are well rounded (Kuenen and Perdok, 1962; Krinsley and Doornkamp, 1973). In contrast, Folk (1978) found that quartz grains from the Simpson Desert were sub-angular to angular in shape with no noticeable rounding, diagnostic of the contemporary environment; thus the dunes have stabilised and the aeolian grains have not been transported long distances during their sedimentary history. This study also concluded that aeolian sediments in the Strzelecki Desert are sub-angular to angular in shape, supporting a conclusion that the grains have not been transported far by wind (Figure 5.6C). In this study it was found that those aeolian sand grains located farther from the source are, however, more rounded in shape that those located adjacent to Cooper and Strzelecki Creeks. *o a fl J3 can 3bO .-fl B ex «J -tr-: >-i w rt 1? 3 S 5o .A ? 22 -?> -fla rt.s TK3^ ^c n j-0.0 « O N :csn ~• t:d q u pit s three - h ia l rflu v e d et c — smal l Q, CD c3n eci^f t_tt* S M JS ^H 1 V th e num e o f ns e /""s CD „•, ^•^ cn ,cS •a-sP -M lOT U^J -g in cn O o a y O s_ cn oa Bo fl1 C4H 3 rt O fl vi +J ^3 bo fl -5 13 CD £ '3> J^ l tcio •S^5«SQ 2 -9 3 '-J3 rt o oi k O •C ««T3 <0 -^ N tOi -j-wi +-C> & > w ° % .a feamr e ollisio n racteri s ;§—> 8<0 r^j fe aw 109 In most deserts, abrasion by wind leads to upturned plates on thefractured surface s as a result of impacts between grains. Abrasion also removes the corners of grains, therefore, tending to round the grains (Kuenen and Perdok, 1962; Krinsley and Doornkamp, 1973). These findings contrast with those here from the Strzelecki Desert where the aeolian quartz sand grains are sub-angular to sub-round in shape (Figure 5.6C) while the larger fluvial sediments contain rounded edges (Figure 5.6D) This study found in the Cooper Creek region that there are very few differences between fluvial and aeolian quartz grain surface features. There is a diagenetic effect, which occurs especially in the older sediments. V-shaped etchings are more prominent in lower lying and wetter fluvial sediments, which indicates that they are probably the result of chemical etching rather than mechanical abrasion as supported by the study by Pell and Chivas (1995). Overall the aeolian grains have been derived from a fluvial environment and deposited to form aeolian features such as longitudinal and source-bordering dunes. 5.10 CONCLUSION Mean grain-size and sorting are fundamental physical properties that can reflect sedimentation mechanisms and depositional environments. Fluvial strata are generally considered to consist of coarse-grained sediments whereas aeolian sediments primarily consist offine-grained sediments. However, if onlyfine-grained sediment s are available for transport by Cooper and Strzelecki Creeks, then they will transport only such sand regardless of velocity or energy. Thus, grain-size of alluvial, aeolian and lacustrine sediments depends on a combination of both sediment availability (mud, sand or gravel) and the fluvial energy at the time of transport. Alluvial sediments generally consist of more poorly sorted sediment due the wider range of particle sizes which can be transported by river systems. However, within this study site, the sand has clearly been reworked between adjacent fluvial and aeolian environments reducing the possibility of truly diagnostic sediment change for each environment as shown in Figure 5.7. Aeolian sediments tend to be better sorted on dune crests where they are extensively reworked. The poorly sorted aeolian sediments in this study differ from those aeolian environments reported by Folk, 1971; Lancaster, 1981, 1986; Wasson, 1983a,b; El- Sayed, 1999; Livingston et al. 1999 and Pell et al 2000. The poor sorting of dunes in the Strzelecki Desert is associated with a higher percentage offines (<6 3 nm) due to the 110 presence of sand-sized clay aggregates/pellets. Once the clays have been removed, the aeolian samples show similar sorting to that described from other aeolian environments (Folk, 1971; Lancaster, 1981, 1986; Wasson, 1983a,b; El-Sayed, 1999; Livingstone?al. 1999 and Pell et al. 2000). Grain-size and sorting were used to determine the depositional environment of sediments, which was concluded to be that source-bordering dune sand in this study area were transported and deposited by wind from adjacent upper palaeochannels (Figure 5.7). The sand-sized clay aggregates found in aeolian dunes have also been derived from the adjacent channels and floodplains. The longitudinal dunes formed from the reworking of sand from older source-bordering dunes and the lunettes were derived from lake floor sands. f ~\ ['Oyei^Hfe.;! Palaeochannel Palaeochannel l-pep Reworking and ^_ Addition of refining of dune fluvial pelleted crests. mud from floodplains and swales. Figure 5.7: Flow diagram illustrating how sand from Cooper and Strzelecki Creeks is transported to source-bordering dunes which longitudinal dunes have evolved formed. Additionally sand- sized clay aggregates are transported by wind from adjacent floodplains and swales and deposited on longitudinal dunes. Examination of clay minerals by X-ray diffraction revealed kaolinite, montmorillonite and illite as the principle clays found in the depositional environments, with illite dominating the samples. The clays were observed to be poorly crystalline, mixed-layered clays consisting of illite-montmorillonite. The origin of these clays is probably from the weathering of the Winton and Eyre Formations. These clays have been transported by Ill the modern Cooper as floodwaters travel from the black soil (basalt) plains in Queensland through the Innamincka Dome and then deposited throughout both the Cooper 'fan' area and the Coongie Lakes region via the northwest branch. Investigation of mineralogy revealed quartz as the dominant mineral found in alluvial, aeolian and lacustrine environments with metaquarzite, feldspars, zircon, chert and rock fragments making up the other components of the samples. Alluvial samples from Strzelecki Creek and the northwest branch of Cooper Creek contained very large angular quartz grains in comparison to the fluvial samples derived from the palaeochannels located within the Cooper 'fan'. This possibly suggests that the flow through the Innamincka Dome was contained within the Cooper 'fan' and that there was more frequent flooding, resulting in the weathering (mechanical and/or chemical) of quartz in the 'fan' region. The more angular shape and larger size of quartz derived from Strzelecki Creek and the northwest branch, possibly suggests that lessfrequent flooding occurred along these channels than the Cooper 'fan'. In contrast to other desert regions of the world, in this study area, aeolian dune samples were identified as more angular rather than rounded in shape. The angularity of these dunes suggests that the sand, which has been derived from upper palaeochannels, located adjacent to both source-bordering and longitudinal dunes, has been deposited rapidly and that possibly the sand has not been transported back and forth on the crests of the dunes in the Cooper Creek region near Innamincka. The SEM work conducted by Pell and Chivas (1995) and this study both concluded that there was very little difference between fluvial and aeolian quartz grain surface features in the Strzelecki Desert. All of the depositional environments contained the same feature, principally the V-shaped etching or grooves. When examining the colour of these sediments, there was no real noticeable difference apart from the longitudinal dunes, but even colour varied between dunes depending on their physical location and the presence of outcropping silcrete in the region. This study, however, examined colour of alluvial, aeolian and lacustrine environments from a localised area with a complex history, whereas Wasson (1983a,b) was researching the broad picture across the Simpson and Strzelecki Deserts. 112 The cluster analysis identified four major groups from a number of variables, mainly based upon grain-size parameters such as mean, standard deviation, kurtosis and skewness. The first group (Group 1) consisted mainly of fine-grained, poorly to moderately well sorted aeolian samples. Those samples that are poorly sorted contained a higher percentage offines an d clay pellets which divided Group 1 into two sub-groups. The second group (Group 2) consisted on upper palaeochannel, lower palaeochannel and overbank samples which are moderately sorted but are either fine or medium grained which resulted in two sub-groups of Group 2. The third group (Group 3) resulted in a mixture of fluvial, diagenetically altered and source-bordering sediments that are very fine tofine-grained, very poorly sorted with a high percentage of fines. The last group (Group 4) identified by the dendrogram was a fluvial group consisting of fine-grained poorly sorted sediments located within the Cooper 'fan' area. Therefore, the cluster analysis identified four major groups and six sub-groups based upon mean grain-size analysis and the standard deviation of samples taken from different depositional environments in this study area. Comparison between the grain-size parameters of sediments from alluvial, aeolian and lacustrine environments from Cooper Creek near Innamincka shows them to be different. In contrast when examining the mineralogy, clay type, shape of grains, colour and quartz surface grain features, it can be concluded that regardless of the present depositional environment (i.e. palaeochannels, lunette, source-bordering or longitudinal dunes) the sedimentary characteristics of the sands in all of these environments is similar. This similarity indicates that the sand has been derived from the same source, that is,rivers are the main supplier of sand which has been transported by wind from the palaeochannels, floodplains and swales and deposited to form source-bordering dunes which have been reworked by wind to form longitudinal dunes in the area. Additionally, the quartzose lunette in the Coongie Lakes region has been formed from sand derived from the lakebed. This leads to the conclusion that in this region there is a continuous reworking of sand from rivers, dunes and lunettes and that there are no fundamental differences in sediment characteristics between these depositional environments. 113 CHAPTER 6 STRATIGRAPHIC INTERPRETATIONS AND THERMOLUMINESCENCE CHRONOLOGY OF ALLUVIAL, AEOLIAN AND LACUSTRINE SEDIMENTS 6.1 INTRODUCTION This chapter examines the alluvial, aeolian and lacustrine stratigraphy and TL chronology of Cooper Creek near Innamincka, Coongie Lakes, Strzelecki Creek and the Strzelecki Desert. The sites are organised by geographical location so that adjacent stratigraphic and sedimentary facies can be readily compared. The geographical locations include Coongie Lakes, northwest branch of Cooper Creek (Scrubby Camp, "Aarpoo", Marpoo, Tilcha and Cullyamurra Waterholes, and Innamincka Racetrack), Turra, Gidgealpa and Dog Bite Lakes located in the Cooper 'fan' area, Strzelecki Creek and Strzelecki Desert (Figure 1.2, Figure 1.3 and Figure 1.4). Each individual site is interpreted according to sedimentary facies description and TL chronology. This data is then discussed in Chapter 7 where the Quaternary history for the study region is described and compared with Australian terrestrial Quaternary records. 6.2 STRATIGRAPHIC AND SEDIMENTARY FACIES DESCRIPTIONS AND INTERPRETATIONS 6.2.1 Coongie Lakes The Coongie Lakes region is classified as afreshwater wetlan d system listed under the Australian Ramsar Convention (Site 27) and is located about 108 km northwest of the township of Innamincka. It is composed of numerous lakes that are fed by the northwest branch of the Cooper and other creeks in the north of the study area. Lake Marroocutchanie (Figure 1.4A and Figure 6.1) was selected as a location to investigate the stratigraphy and chronology of a large lunette situated on the northern side of the lake. The second sampling site, Coongie longitudinal dune (Figure 1.4A and Figure 6.1), is one of the many such dunes located in the Coongie Lakes region. It was chosen to investigate the chronology and stratigraphy of the dunes in the area and the relationship of these dunes to Coongie Lakes and Cooper Creek. 114 Figure 6.1: LANDSAT TM image of the Coongie Lakes region including sampling sites Lake Marroocutchanie (27°07'31"S, 140°13'36"E) lunette and Coongie longitudinal dune (27°13'32"S, 140°10'45"E). 6.2.1.1 Lake Marroocutchanie Lunette Auger Hole 1 Auger Hole 1 is located approximately 200 m from the present lake-full shoreline on the flank of the northern lunette of Lake Marroocutchanie (Figure 6.2 and Figure 6.3). The lowermost unit consists of at least 0.70 m of mottled (grey/white) clay (lake sediments) with small gypsum and carbonate nodules (Figure 6.3). The middle unit (0.37 m) consists offine-grained sandy clay overlain by 3.42 m of very poorly sorted (2.90 Figure 6.3). The coarse silt consists of quartz (97%), metaquartzite (0.5%), feldspars (0.5%), rock fragments (2%) with heavy minerals and micrite matrix. The sand grain surfaces arefree o f any coating and have a sub-angular to well rounded shape. Auger Hole 2 Auger Hole 2 is located 120 m north of Auger Hole 1 on the crest of the lunette of Lake Marroocutchanie (Figure 6.2 and Figure 6.3). The base of Auger Hole I (Figure 6.3) consists of at least 0.50 m of poorly sorted (1.23 §), yellow (10YR7/4), fine-grained (2.63 <|>) sand containing very large secondary gypsum nodules reworked by wind or water. Here the mineralogy consists of quartz (88.5%), rock fragments (6.5%), metaquarzite (2.5%), opaque minerals (2.0%) and clay pellets (0.5%). This is overlain by 10.70 m of moderately sorted (0.75 Figure 6.2: Crestal view to the west of Lake Marroocutchanie lunette showing the location of Auger Hole 1 and. Auger Hole 2 referred to in Figure 6.3. o o IN o 00 o o t/J o o o o MD (N (s9.usui) susunq 9Aoqe juSraH C/J o OH OJ T3 cn (D i- 1 (0 a C/(Dj T3 rt .6 •a, O -J o to o (ss49ui) grBAVg 3AoqB tqSiSH MD a | E 8 118 6.2.1.2 Coongie Longitudinal Dune Figure 6.5 illustrates the local topography in the vicinity of Auger Holes 1 and 2 located on the longitudinal dune and adjacent swale immediately south of Coongie Lake (Figure 6.1). This dune is just one of a number of longitudinal dunes that extend northwards onto terrain that has in the past been part of an expanded Coongie Lake (Figure 1.4A). Auger Hole 1 is located on the dune crest and about 150 m south of the present lake shoreline, whereas Auger Hole 2 is located approximately 170 m west of Auger Hole 7 in the swale area. Samples from Auger Hole 1 were TL dated but it was not possible to obtain material suitable for TL dating from Auger Hole 2 (swale) due to the presence of sticky blue/grey clay which was difficult to remove from the auger. Auger Hole 1 Figure 6.5: Crestal view looking north along Coongie Lake longitudinal dune site and the swale, located on the left hand side of the photo, looking towards Coongie Lake. Auger Hole 1 In Auger Hole 1 (Figure 6.4) the lowermost unit consists of at least 1.0 m of moderately sorted (0.75 §) light brownish grey (10YR6/2),fine-grained (2.7 9 showed a slight increase in mud content with depth. This uppermost sand unit has a very distinctive reddish yellow colour due to a thick coating of iron oxide lodged in the cupules of the quartz grains. Thin section analysis reveals that the aeolian sand consists of quartz (89%), rock fragments (5.5%), metaquartzite (3.5%), chert (1.0%), feldspar (0.5%), and opaque minerals (0.5%). The clay pellets (0.2%) are well rounded and red/brown in colour due to strong oxidisation characteristic of arid and semi-arid environments. Auger Hole 2 The stratigraphy of Auger Hole 2 (Figure 6.4) consists of a lower 2.85 m thick moderate to well sorted (0.70 a>-0.93 <|)), light grey (10YR7/2) and light brownish grey (10YR 6/2),fine-grained (2.34 (f>-2.93 (j>) clayey sand. The sand content is low and the unit is dominated by mottled (grey/brown) clay with manganese (sulphides); carbonate nodules and fine-grained sand increase with depth. This unit is overlain by 1.15 m of moderate (0.72 d)-0.96 (j)) to well-sorted (0.60 (j)), light brownish grey (10YR 6/2), light grey (10YR 7/2), pale brown (10YR 6/3), lacustrine clay with somefine-grained (2.3 3 (()- 3.09 (j>) secondary sand. The source of the sand is probably the adjacent longitudinal dunes. The grey/brown colour of the lacustrine clay observed in thefield i s indicative of less oxidising conditions and indicates a shallow water environment such as in an expanded Coongie Lake. 6.2.1.3 Interpretation of Coongie Lakes Lacustrine sediments in the swale are probably OI Stage 5 or earlier and were deposited during a high watertable and a wetter climate regime. The initial Lake Marroocutchanie lunette was dated at around OI Stage 5. Quartz-rich lunettes form during high water phases when sand is worked by wind and near-shore drift to the leeward end of the lake and then blown into dunes, similar to present coastal dunes. During OI Stage 2 or earlier, the Coongie Lakes region became drier and lake levels receded with evidence of longitudinal dunes progressing onto the lake floors after the LGM (-16 ka), and the reworking of longitudinal dune crests and lunettes in the lake area during the Holocene. This formation of longitudinal dunes in the region coincides with the prevailing anti clockwise wind pattern (northwards at this location) previously identified by Brookfield 120 (1970), Twidale (1972) and Wasson (1986). During OI Stage 1, it appears that the sand from the original lunette built near Lake Marroocutchanie has also been eroded and transported by wind to form the present day lunette located farther to the northwest. 6.2.2 Northwest Branch of Cooper Creek 6.2.2.1 Scrubby Camp, "Aarpoo" and Marpoo Waterholes Scrubby Camp Waterhole is located approximately 20 km northwest of "Aarpoo" Waterhole, which is located about 5 km northwest of Marpoo Waterhole along the present northwest branch of Cooper Creek (Figure 1.4B, Figure 6.6 and Figure 6.7). These three sites are cut-bank exposures consisting of gravel lag deposits, abandoned channel sands and overbank deposits (Figure 6.8). S N Scrubby Camp Waterhole i ' ~i Kilometers 1«*BTE 1W2SE Figure 6.6: LANDSAT TM image of the Scrubby Camp Waterhole (27°38'50"S, 140°22'34"E) site located along the northwest branch of Cooper Creek which flows into the Coongie Lakes region. 121 l+O'JS'E Figure 6.7: LANDSAT TM image of the Marpoo Waterhole (27°45'10"S, 140°33'57"E), "Aarpoo" Waterhole (27°46'50"S, 140°31'40"E), Tilcha Waterhole (27°45'8"S, 140°36'43"E) and Wills Grave (27°46'45"S, 140°36'35"E) sites located along the northwest branch of Cooper Creek. At Scrubby Camp Waterhole, the base of the exposure consists of 2.0 m of muddy, gritty, coarse-grained, cross-bedded fluvial channel sand that gave a TL date of 66.5+5.8 ka (W2245; Figure 6.8). The middle unit consists of 0.80 m of gritty, fine grained,fluvial sand overlain by only 0.30 m of silty sand overbank deposit (Figure 6.8). At "Aarpoo" Waterhole, the 1.9 m basal sequence visible at water level consists of green/grey clay and dolomite and probably represents weathered Etadunna Formation (Figure 6.8). This clay is overlain by 1.2 m of moderately sorted (0.75 (j>), angular to well rounded, pale yellow (2.5Y 7/4), medium-grained (1.19 §)fluvial channe l sand that gave a TL date of 154+17 ka (W2242; Figure 6.8). The channel sand is very finely laminated and cross-bedded, and consists of quartz (98%), metaquartzite (1.0%), feldspars (0.5%) and rock fragments (0.5%). The sand is overlain by 2.5 m of silty sand overbank deposit from the modern Cooper. t C3 Ofl Ti V) O &OJ T3 T3 fl rt t/j cj 4_1 H a ToJ O CJ w Xi 3 Tol cn CJ CJ cn CJ O CyJ CJ S3 5 j2 en> 6 CJ 43 to CJ -o &o S CJ .—i O 43 "p;—d> i- •> p. a ^ £o o O l-i OH 1 on •^ ttJ 2& OH «- o o o o u £< 52 3 •3 ^ CoM q,4 3 rt ° s on o en CJ is 9. <- cj cj cn +3 i c3 in > c2 a O -M u (SSJtOUl) |9A9T J9t^yV\. 1U3S3J(J QAOqB tqSiSH 5 .& ° is on « • • c oo o B I a| £ 8 123 At Marpoo Waterhole (Figure 6.8) the stratigraphy consists of at least 4.30 m of fluvial channel sands. The sediment is poorly sorted (1.71 d>), sub-angular to well rounded, brownish yellow (10YR6/6), medium-grained (1.50 d>) sand. At water level, the unit consists of a mixture of gravel and coarse sand with interbedded sand/pebbles fining upwards through the sequence. There is also a gravel layer at the top of this unit. The sand gave a TL date of 77.5+8.1 ka (W2241; Figure 6.8) and is overlain by 2.0 m of silty sand with small gypsum nodules. Thin sections reveal that the palaeochannel sand unit consist of quartz (94.5%), metaquartzite (3.5%), rock fragments (1.0%) and clay pellets (1.0%). 6.2.2.2 Interpretation of Scrubby Camp, "Aarpoo" and Marpoo Waterholes The Scrubby Camp Waterhole section is a single channel sequence of coarse bed-load material and channel sands deposited in a relatively high-energy fluvial environment during early OI Stage 4. It is overlain by contemporaryfloodplain sedimen t transported by the Cooper. Possibly the upper part of the channel sequence has been eroded prior to OI Stage 1. At "Aarpoo" Waterhole the thick clay unit is interpreted as fluvial overbank mud deposited by vertical accretion on afloodplain prio r to or during OI Stage 6 (possibly Etadunna Formation). The clay is cohesive and not as easily eroded as sand. Bed material was then deposited during OI Stage 6 in a high-energy fluvial channel environment similar to that of Scrubby Camp during OI Stage 4, with the laminated sand at "Aarpoo" Waterhole indicating a decrease in the stream energy (flood intensity) of the Cooper during the end of OI Stage 6. Finer sediment (silty sand) similar to that at Scrubby Camp and Marpoo Waterholes was deposited as overbank material sometime after OI Stage 6 to the present. At Marpoo Waterhole the fluvial palaeochannel sequence includes a basal layer of gravel and coarse bed-load sand which was deposited in either late OI Stage 5 or early OI Stage 4. A second gravel base is located at the top of this sand sequence at Marpoo Waterhole that probably formed towards the end of OI Stage 4 to the present. This upper gravel base probably representsfluvial deposition in a high-energy channel environment. The channel was again abandoned with overbank deposits forming the uppermost unit sometime from OI Stages 4 to 1. The modern channel returned to its present location 124 eroding the Marpoo Waterhole section to the current water level. The reason for 7.0 m of erosion could be due to either increased stream energy, or local uplift. It may indicate that the Cooper 'fan' is out-of-grade with present conditions causing incision. In summary, the three sites of Scrubby Camp, "Aarpoo" and Marpoo Waterholes suggest that Cooper Creek downstream of the Innamincka Dome was significantly active during OI Stages 6, 5 and 4. This supports similar evidence from other sites examined below. 6.2.2.3 Tilcha Waterhole Like Scrubby Camp, "Aarpoo" and Marpoo Waterholes, Tilcha Waterhole is an exposure on a cut-bank of present Cooper Creek. However, it is described separately here because it is a very extensive vertical section incorporating both fluvial and aeolian deposits. It is located approximately 17 km west of Innamincka along the northwest branch of Cooper Creek and about 5 km east of Marpoo Waterhole (Figure 1.4B and Figure 6.7). An extensive cut-bank section exposes basal palaeochannel sands that have given TL dates of between OI Stage 6 and OI Stage 5 (Figure 6.9), overlain by approximately 2.0 m offloodplain overban k mud. This is overtopped with five aeolian units totalling 13.4 m and TL dated between OI Stage 3 and OI Stage 2. Two palaeosol units occur, one on Aeolian Unit 2 and the other on Aeolian Unit 1 (Figure 6.10). From scroll patterns on the meander bend at Wills Grave directly opposite Tilcha Waterhole there is evidence of lateral migration of Cooper Creek into the cut-bank section of Tilcha Waterhole (Figure 6.7). The relationship between the meander bend at Wills Grave and Tilcha Waterhole is discussed further in Section 6.2.2.5. Fluvial Sequence An extensive fluvial sequence makes up the lower part of the Tilcha Waterhole exposure consisting of channel sands that became coarser with depth (Figure 6.12). At the base of the fluvial sequence these sands consist of medium-grained, slightly indurated trough cross-bedded strata with set thicknesses ranging from 0.10 m to 0.50 m and a mean palaeocurrent orientation of 351°. They gave a TL date of 146+13 ka (W2469; Figure 6.11). This is overlain by a well-sorted (0.49 (J>), very pale brown (10YR 7/4), fine-grained (2.01 $) sand lens, which in turn is overlain by moderately well sorted (0.67 (j>) to poorly sorted (1.26 (J)), light yellowish brown (10YR6/4) and very pale 125 brown (10YR7/4), medium-grained (1.06 <})-1.58 d>) sand that gave a TL date of 152+18 ka (W2468; Figure 6.12). Set thicknesses range from 0.15 m to 0.20 m, consisting of trough cross-stratified sand showing palaeocurrent trends between 289° and 304°. Above the sand unit is an erosional gravel lag unit about 0.10 m thick that is overlain by a well-sorted (0.40 Aeolian/Palaeosol } Section Fluvial Section Figure 6.9: Tilcha Waterhole sequence, northwest branch of Cooper Creek. The stepped trench in the side of a cut-bank section showing fluvial sediments overlain by aeolian sediments further illustrated in Figure 6.12. 126 Palaeosol 1 Figure 6.10: Upper portion of the Tilcha Waterhole section showing palaeosol sand (Palaeosol 1) overlain by an aeolian sand unit (Aeolian Unit 5) which inturn is overlain by a second palaeosol sand unit (Palaeosol 2) illustrated in Figure 6.12. Figure 6.11: Trough cross-stratification of medium-grained sand (St) overlain by a gravel layer representing the erosional gravel lag at the base of the OI Stage 5 succession. 127 0 1 2 3 W2232 14.3+/-1.0ka 4 Palaeosol 2 I Clay 5 Palaeosol 6 Aeolian Unit 5 Sand 7 W2234 C/J co 20.1+/-1.5ka 8 W2235 Palaeosol 1 29.4+/-2.8 ka - 9 Aeolian Unit 4 CU W2464 36.1+/-3.2ka- Aeolian Unit 3 10 Calcrete Unit C+H O 11 19 20 21 22 W2469 23 146+/-13ka 24 , , , w + -+- -10 0 10 20 30 40 50 60 Distance from Waterhole (metres) Figure 6.12: Stratigraphic cross-section at Tilcha Waterhole, northwest branch of Cooper Creek, showing the relationship between stratigraphic units and TL dated samples. 128 The next overlyingfluvial unit consists of poorly sorted (1.01 d)-1.03 q>) to moderately sorted (0.97 (|>), rounded to angular, yellow (10YR 8/6) and very pale brown (10YR 8/4 and 7/4), medium-grained (1.32 (W2240) and 97.0±8.4 ka (W2467; Figure 6.12). These sands are trough cross-stratified with set thicknesses of 0.25 m to 0.30 m, indicating a palaeoflow trend towards 343°. Small mud clasts occur at the base of the unit. It is overlain by about 3.60 m of poorly sorted (1.17 Overlying the fine-grained sand unit is 2.0 m of floodplain overbank mud consisting of very poorly sorted (3.29 (j>-3.35 (f>), pale brown (10YR6/3) and very pale brown (10YR7/3), massive, blocky clay and some silt (5.14 Palaeosol and Aeolian Sequences Directly above the mud unit begins the aeolian and palaeosol sequence. Aeolian Unit 1 consists of 1.0 m of poorly sorted (1.78 (2.61 §) laminated sand that gave a TL date of 56.3+A6 ka (W2677; Figure 6.12). The unit is capped with mud andfine-grained sand (0.20 m) containing CaC03 rhizomorphs, root channels and evidence of soil development, including manganese oxides. This is overlain by Aeolian Unit 2 which is 1.60 m thick and consists of very poorly sorted (2.38 (j)), angular to rounded, very pale brown (10YR7/4), very fine-grained (3.69 (()) sand that gave TL dates of 58.0±5.3 ka (W2465) and 55.5±5.1 ka (W2237; Figure 6.12). The mineralogy of this unit consists of quartz (90.5%), rock fragments (5.5%), 129 metaquartzite (3.5%) and chert (0.5%) along with traces of feldspar, heavy minerals and clay pellets. This unit contains very fine-grained wind ripples, abundant CaC03 rhizomorphs and a few manganese oxide coated rhizomorphs. The old root channels and CaC03 rhizomorphs randomly distributed through the unit indicate aeolian processes were once acting upon a vegetated surface of accreting sand. There is a dramatic change at the top of this unit, to a hard calcrete unit 0.9 m thick, which probably represents a palaeosol capping to the Aeolian Unit 2 (Figure 6.12). This calcrete is overlain by Aeolian Unit 3 composed of poorly sorted (1.47 dune cross-bedded, with the palaeowind orientated towards 245°, and is indurated with CaC03 along bedding planes, manganese oxide mineralisation and CaC03 rhizomorphs. These factors, and an absence of wind ripples, suggest rapid sedimentation on a slip face. A thin (0.18 m) palaeosol unit (Palaeosol 1) overlies Aeolian Unit 4 and is described as horizontally bedded sand with wind ripple crests orientated at 170°, manganese oxide mineralisation, occasional CaC03 rhizomorphs and gypsum crystals. This in turn is overlain by the uppermost aeolian unit (Aeolian Unit 5) situated between depths of 7.7 m and 3.9 m in the section (Figure 6.10 and Figure 6.12). This unit consists of dune cross- bed sets (0.20 m-0.50 m thickness, orientated at 338° and 322°), containing a few fine (<5 mm) long vertical cracks, manganese oxide mineralisation, CaC03 rhizomorphs and distinctive CaC03 leisegang bands. The leisegang bands present are the result of 130 secondary mineral deposition as they transect the dune structure. There is also evidence of reactivation of the surfaces, pedogenesis and sand accretion around the palaeo- vegetation on the dune structure. Aeolian unit 5 (3.75 m thick) is composed of very poorly (2.19 4»-2.57 <))) to poorly (1.61 <|)) sorted, angular to rounded, yellow (10YR 7/6), very pale brown (10YR 7/4) and brownish yellow (10YR 6/6), very fine (3.62 Figure 6.13: Overlying the large floodplain mud unit is a series of aeolian sediments, calcrete and palaeosol units. This extensive Aeolian Unit 5 is capped with 0.85 m of the last palaeosol sand unit (Palaeosol 2) composed of poorly sorted (1.44 4>), sub-angular to rounded shaped, reddish yellow (5YR 6/6), fine-grained (2.70 $) sand that gave a TL date of 14.3+1.0 ka (W2232; Figure 6.10 and Figure 6.12). The quartz sand grains are heavily coated in iron oxide with thin section analysis revealing quartz (92.0%), metaquartzite (4.0%), rock fragments (3.0%) and chert (1.0%). Heavy minerals, feldspar and clay pellets were also 131 noted in the sample. This unit is characterised by simple planar cross bedding, a few fine (<5 mm) vertical cracks, minor root formation, carbon and manganese oxide materialisation. The palaeosol and aeolian sequences are overlain by 3.1 m of poorly sorted, reddish yellow (7.5YR6/6),fine-grained moder n aeolian sand, forming the uppermost unit at Tilcha Waterhole. This unit was not dated but elsewhere in the study region similar dunes have been TL dated as Holocene. The crest of the dune is mobile forming part of a longitudinal dune. 6.2.2.4 Wills Grave Wills Grave is located on the meander bend directly opposite the cut-bank Tilcha Waterhole section (Figure 1.4B, Figure 6.14 and Figure 6.15). This site was selected because a series of point bars are visible in the LANDSAT TM images of the site (Figure 6.14), indicating that the river bend has migrated north westwards into the Tilcha cut-bank exposure. Samples were collected for TL dating to see how recently this migration has taken place. As expected thefluvial deposit s are younger at Wills Grave than those in the exposed cut-bank at Tilcha Waterhole. Auger Hole 1 Auger Hole 1 is located 220 m south of the present Cooper Creek channel directly opposite Tilcha Waterhole (Figure 6.16) and is surveyed at approximately 9 m above the low-flow water level in Cooper Creek at the time. The base of Auger Hole 1 (Figure 6.16) consists of at least 1.0 m of moderately well sorted (0.67 (()), sub-rounded to rounded, very pale brown (10YR7/3), medium-grained (1.61 dp) sand and large pebbles. The mineralogy of the sand in the pebble unit is composed of quartz (90.5%), rock fragments (4.5%), metaquartzite (3.5%), and feldspar (0.5%), chert (0.5%) and opaque minerals (0.5%). This sand and pebble unit is overlain by 1.60 m of poorly sorted (1.09 (J>), sub-rounded to rounded, very pale brown (10YR7/3), coarse-grained (0.86 <|>) sand that gave a TL date of 26.2+2.7 ka (W2574; Figure 6.16). This unit is overlain by 3.40 m of well-sorted, creamy,fine-grained sand (floodplain). 132 140°33'E Tilcha Waterhtole 27°47'S Figure 6.14: LANDSAT TM image of the Wills Grave and Tilcha Waterhole (27°45'8"S, 140°36'43"E) sites showing the location of the surveyed section at Wills Grave (27°46'45"S, 140°36'35"E) and the distinctive scroll bar patterns of Cooper Creek along the northwest branch. Longitudinal Dune Tilcha N < > S Waterhole Channel Migration A Source-Bordering Dune Wills Grave AH1 AH2 AH3 AH4 LLW Figure 6.15: A Schematic section across the northwest branch of Cooper Creek showing the relationship of Tilcha Waterhole (27°45'8"S, 140°36'43"E) fluvial section and Wills Grave (27°46'45"S, 140°36'35"E) section. Note that AH1 to AH4 represent auger holes at Wills Grave referred to in Figure 6.16. OJ -t-1 T3 OJ C/J OJ •1-1 ca OJ O T3 C co OH « feb \S cd tl Oj bD c/3 ca CU I-H I a "o o •6 ca8 OJ C/J U Q > ca ac« £ CO .£3 CfH a c o o g u •n M CJ (/] (oJ OJ V£> l-c cu Ol H — Rn OJ ^ C4-I o OJ I -a •g T3 1 T3 •f-H c o o o cu CO 3 o •3 IT) Ul o O•VJ X cV3 •n 8 !• • • o g e o ro o &n o OJ o > f on ."t•yti a O PH •S C+£H Tn o O in a 8 ,J3 •-B OJ 5O on •Y) on (N oOn 61) I • I' I +^+ •6 © 00 KO "* NOrMTtvooOONi'WOOO Tl fS -H c-H ^H I i I • ,-H H i-H i-H ,-H Auger Hole 2 This auger hole is located 50 m south of Auger Hole 1 along the Wills Grave section (Figure 6.16) and is surveyed at 8.73 m above the present water level. The lowermost unit of Auger Hole 2 consists of 0.40 m of basal clay mixed with poorly sorted (1.22 (J)), light yellowish brown (10YR6/4), medium-grained (1.42 q>) sand that might represent the Tertiary basement. The basal clay unit is overlain by 2.60 m of moderately sorted (0.79 (|>) to poorly sorted (1.06 (j>), light brownish grey (10YR 6/2) and very pale brown (10YR7/4), coarse-grained (0.74 4>-0.82 d>) fluvial sand that gave a TL date of 45.5±5.9 ka (W2575; Figure 6.16). This sand is overlain by 5.0 m of a sand and pebble unit which consists of coarse (0.94 d)) to medium-grained (1.38 (0.64 (j)) to moderately sorted (0.71 Auger Hole 3 Auger Hole 3 is located 50 m south of Auger Hole 2 and is surveyed at 8.56 m above the present water level (Figure 6.16). The basal unit consists of at least 2.0 m of poorly sorted (1.08 (J>), light grey (10YR 7/2), medium-grained (1.84 overlain by 5.50 m of mainly clay with some poorly sorted (1.02 q>-1.25 ([)), light grey (10YR7/2), fine (2.20 d>) to medium-grained (1.62 q>)fluvial sand. About 2.0 m of fluvial sand and pebble overlies the clay unit that is probably Tertiary in age. This in turn is overlain by a 1.50 m thickfluvial uni t of moderately sorted (1.00 <))), very pale brown (10YR7/3), medium-grained (1.64 d>)fluvial sand that gave a TL date of 250+60 ka (W2578; Figure 6.16). A 1.0 m thick sand and pebble unit overlies the 250 ka fluvial unit, which in turn is overlain by 2.0 m of moderately well sorted (0.67 (|)), very pale brown (10YR 7/3), medium-grained (1.03 d))fluvial sand. Above this a third sand and pebble unit, 4.0 m in thickness and consisting of moderately well sorted (0.69 sand that gave a TL date of 55.3+7.6 ka (W2577; Figure 6.16). The sand in the sand and pebble unit is composed of quartz (92%), metaquartzite (4%), rock fragments (3.5%) and chert (0.5%). This is overlain by 2.0 m of moderately well sorted (0.70 Auger Hole 4 Auger Hole 4 is located 55 m south of Auger Hole 3 (Figure 6.16) and is surveyed at 8.43 m above the present water level. The base of this section consists of about 2.50 m of mottled (brown/grey), moderately sorted (0.56 •$), pale brown (10YR 6/3), very fine grained (3.17 d>) clay which is possibly of Tertiary origin. This mottled clay unit is overlain by 2.0 m of medium-grained sand and large pebbles that appear to be a basal channel deposit. This in turn is overlain by a 6.4 m thick moderately well sorted (0.59 0.68 (J)), sub-rounded to rounded, light grey (10YR 7/2) to very pale brown (10YR 7/3), fine-grained (2.16 rounded, very pale brown (10YR 7/3), medium-grained (1.57 TL date of 35.9±4.3 ka (W2579; Figure 6.16). The sand consists of quartz (97.5%), rock fragments (1.5%), metaquartzite (0.5%) and chert (0.5%). 6.2.2.5 Interpretation of Tilcha Waterhole and Wills Grave About 250 ka an active channel migrated across the general location of Wills Grave truncating what is probably Tertiary-age Etadunna Formation (Figure 6.17). Subsequent lateral activity by Cooper Creek truncated these -250 kafluvial deposits replacing them with OI Stage 6 (~152ka to 146 ka) channel sands and gravels which inturn were superimposed with OI Stage 5 (-120 ka to 97 ka)fluvial deposits, as recognised in the lower part of the Tilcha Waterhole section (Figure 6.9 and Figure 6.15). During OI Stage 3, the precursor to the present channel migrated through the OI Stage 5 fluvial deposits and laying down a clearly defined scrolledfloodplain unit (Figure 6.14) at Wills Grave dating at OI Stage 3 (-55 ka to 26 ka; Figure 6.17). As the channel was 137 migrating north westwards, southerly winds appear to have been producing source- bordering dunes infront of it, dating at OI Stage 3 (-58 ka to 55 ka) and again at -36 ka to 29 ka (Figure 6.9). Further substantial aeolian activity produced similar dunes during the LGM (-22 ka to 20 ka). During OI Stage 3 the river at this point has migrated about 150 m to 200 m northwards (i.e. a very slow rate). After about 25 ka, the river appears to have stayed roughly in its present position flowing along what is known as the northwest branch. 6.2.2.6 Cullyamurra Waterhole Cullyamurra Waterhole is located about 10 km east of the township of Innamincka forming a major permanent waterhole reaching -30 m in depth (Figure 1.3, Figure 6.18 and Figure 6.19). This site was chosen to investigate the flow regime changes of Cooper Creek by locating 'recent'fluvial sediment s and comparing them to the older fluvial deposits from the Cooper 'fan' area (North Dog Bite Lakes 1 and 2, East Dog Bite Lake, Gidgealpa South and Turra). Because of flow confinement within the Innamincka Dome, old alluvium has been reworked and deposited during the Late Pleistocene and Holocene despite the declining flow regime of Cooper Creek during the Late Quaternary. The Cullyamurra Waterhole section consists of a series of channel sands and overbank deposits that have provided TL dates between OI Stage 3 and OI Stage 1 (Figure 6.20). Auger Hole 1 Auger Hole 1 is located 120 m south on a surface about 5.0 m above the typical low- stage water level of Cullyamurra Waterhole (Figure 6.20). The lower part of the auger hole consists of at least 3.20 m of mottled (blue/grey) clay with manganese and iron oxide mineralisation, overlying silcrete pebbles located at the base of the hole. This clay is overlain by a 1.30 m medium to coarse-grained sand and pebble unit, which, in turn, is overlain by 3.0 m of mottled (blue/grey) clay, which is similar to the clay found at the base of this auger hole. A 0.45 m thick splay lens composed of gritty, medium-grained sand overlies the clay, and is overlain by a further 0.50 m of clay. Overlying the clay is 1.60 m of poorly sorted (1.07 d)-1.36 qj), yellowish brown (10YR5/4) and brown (10YR5/3), medium to coarse-grained (0.92 <|)-1.48 cp) sand with pebbles. A 2.50 m thick moderately sorted (0.97 (2.43 <|>) sand unit that gave a TL date of 9.7+1.3 ka (W2669) overlies the sand and pebbles (Figure 6.20). This sand is capped with 1.30 m of silty sand (floodplain). 140*45"E l^'SO'E 140e55'E 140*45"E 140*50'E 140*S5'E Figure 6.18: LANDSAT TM image of Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) and Innamincka Racetrack (27°43'56"S, 140°44'23"E) sites located along Cooper Creek as it enters the confinement of the silcrete capped Innamincka Dome. Flow direction is from east to west. Figure 6.19: A schematic section across Cullyamurra Waterhole (27°42'24"S, 140°51'58"E) showing the location of Auger Holes J to 4 where the surveyed cross-section, illustrated in Figure 6.20, was taken from. o cn _ o OJ o ra I •O TJ HJ c c o H ro co o cn co co ON OJ i I o & o tan 00 S3 u ca 2 — S3 UH_ o O o •V r- cVJ • -H o Q o o o (N o o e A. o o 2 § \ ** \ V ca I TS Z ca a I1 I'l1 I'l tl WD 00 O (N •* VO 00 o (N VD (sai;9ui) J9A9T lsyefa 9A.oqB uoi;BA9ig OJ 140 Auger Hole 2 Auger Hole 2 is situated 300 m south of Auger Hole 1 (Figure 6.20). The base of the auger hole consists of at least 0.50 m of moderately well sorted, coarse-grained sand and silcrete pebbles. This is overlain by 4.0 m of light yellowish brown (10YR 6/4), coarse grained sand that gave a TL date of 62.5±7.7 ka (W2671; Figure 6.20). In turn, this sand is overlain by 2.50 m of moderately well sorted (0.67 fine-grained (2.06 1.50 m in thickness, consisting of moderately well sorted (0.66 ()>), sub-angular to well rounded, very pale brown (10YR7/4), medium-grained (1.01 cb) sand that gave a TL date of 20.1±2.9 ka (W2580; Figure 6.20). The medium-grained sand consists of quartz (91%, some with rutile), metaquartzite (5.5%), rock fragments (2.5%), zircon (0.5%) and chert (0.5%). The sand and pebble unit is overlain by 1.30 m of well sorted; fine grained sand, andfinally 1.20 m of silty sand, to the present surface. Auger Hole 3 This auger hole is located 200 m south of Auger Hole 2 with a distributary channel situated between these two holes (Figure 6.20). Auger Hole 3 consists of three units; the lowermost unit is composed of at least 2.0 m of light brownish grey (10YR 6/2) clay unit with very little carbonate nodules and some moderately well sorted (0.68 ())), fine-grained (2.84 (|)) sand. This is overlain by the second unit, a 3.0 m thick moderately well sorted (0.97 <|)), sub-rounded to rounded, greyish brown (10YR 5/2),fine-grained (2.43 sand consists offractured quart z (94%), rock fragments (2.5%), metaquartzite (2%) and chert (1.5%). The uppermost unit consists of 2.0 m of silty sand (floodplain). Auger Hole 4 Auger Hole 4 is located about 130 m south of Auger Hole 3 and 200 m north of a second but larger distributary channel (Figure 6.20). The base of Auger Hole 4 consists of a 0.50 m thick medium-grained sand and pebble unit that could not be penetrated. This unit is overlain by 1.80 m of poorly sorted (1.45 (3.22 <|>) fluvial sand that gave a TL date of 27.8+2.5 ka (W2582; Figure 6.20). The uppermost unit consists of 3.0 m of poorly sorted (1.07 (j)), pale brown (10YR 6/3), fine grained (2.20 (j>) silty sand (floodplain). 6.2.2.7 Interpretation of Cullyamurra Waterhole Stratigraphic and chronological studies of Cooper Creek (Nanson etal, 1988; Maroulis, 2000) show that most of thefloodplain alluvium is Early to Middle Pleistocene in age with relatively little evidence of reworking of these deposits during OI Stage 4 or younger. Wills Grave (Figure 6.16) provides evidence of about 150 m to 200 m of lateral migration during OI Stage 3. The stratigraphy of Cullyamurra Waterhole shows considerable reworking of alluvium since the LGM (Figure 6.20). Over this period, confined flow within the Innamincka Dome has eroded and replaced sediment to depth of about 12 m below the current floodplain surface and up to 700 m from the present southern edge of the waterhole. Whilefluvial activit y between the LGM and the end of the Pleistocene appears to have been significant in this relatively high-energy location, there seems to have been very little activity during the Holocene. It is believed that flow confinement has amplified evidence for flow regime changes on Cooper Creek by reworking alluvium within the Innamincka Dome at a time even when flow energy has been low and most areas of thefloodplain hav e not been reactivated. 142 6.2.2.8 Innamincka Racetrack The Innamincka Racetrack site is a 5 m high longitudinal dune situated approximately 5 km northwest of Innamincka along the northwest branch of Cooper Creek (Figure 1.4B and Figure 6.18). The investigated section is composed entirely of 4.0 m of moderately sorted (0.99 <|)) to moderately well sorted (0.59 (j)), sub-angular to rounded, reddish yellow (7.5YR 6/6),fine-grained (2.3 9 d)-2.45 6.2.2.9 Interpretation of Innamincka Racetrack Based upon the two TL dates obtained from the longitudinal dune at Innamincka Racetrack, over the last 5 ka to 4 ka, 4 m of aeolian sand has been deposited to form the very young longitudinal dune located north of the township of Innamincka, on the Cooper floodplain. Deposits at this location on the dune in the Early to Middle Holocene have been slight. Between about 5 ka and 1 ka deposition was more rapid and then increased even more rapidly from about 1 ka to present (Figure 6.21). The aeolian quartz grains are a very distinctive red colour due to iron oxide coating from the weathering of Tertiary sediments in the Innamincka Dome region. The sand that formed these longitudinal dunes more than likely originated from the adjacent channels of Cooper Creek. Dune orientation is related to the whorl pattern discussed previously in Chapter 2. 6.2.3 Turra The Turra site, located approximately 47 km southwest of Innamincka (Figure 1.4B and Figure 6.22), exhibits a series of palaeochannels buried beneath the modern Cooper floodplain. These palaeochannels have provided sediment to adjacent source-bordering dunes that in turn have supplied sand for a series of longitudinal dunes extending northwards. Samples for TL dating and sedimentological analysis were taken from a series of auger holes in the palaeochannel area, the source-bordering dune and 144 longitudinal dune with the stratigraphic sections (Figure 6.24, Figure 6.25, Figure 6.27 and Figure 6.26) described in sections 6.2.3.1 to 6.2.3.3. Figure 6.22: LANDSAT TM image showing the location of Turra (27°52'33"S, 140°22'00"E), Gidgealpa Dune (27°55'59"S, 140°13'51"E), Gidgealpa South (28°52'34"S, 140°15'45"E), East Dog Bite Lake (27°53'45"S, 140°9'22"E) and North Dog Bite Lakes 1 (27°55'14"S, 140°9,00"E) and 2 (27°57'36"S, 140°9'40"E). 145 HOTZtTE Turra Source- Turra Bordering Dune Longitudinal Dune Turra FlUvial J Transect \m •i ; *n —| ,N .-;• . ."*. "; y: •' 5 iiiy^^JK-r-^jicr t Kilometers I •Hf-''ciiiflHBl 140°2G'E 14©*25'E Figure 6.23:LANDSAT TM image showing the location of Turra fluvial transect, Turra source- bordering duneandTurnjTon^ (S9.II.9UI) urejdpooT^ 9AoqB tq§T9H o in i CN —'r~ n X Si o .ri rt i- <; o UJ cu 00 S •v-i o 3J a K ri VO n 3 o 00 •3 < T3 3 o o 147 West - East (metres) -200 -100 100 200 300 400 500 600 700 800 i i i i i i I 0 ;- -100 - -200 -300 - -400 •- -500 : - -600 - :- -700 Swale -800 -900 6 1 -1000^ 1 -1100W2 -1200 Cooper Creek Floodplain --1300 -1400 •--1500 - -1600 •--1700 Auger Hole 1 ; Source-Bordering -1800 i Dune -1900 • Dune Edge Dune Crest Auger Holes Figure 6.25: Plan view of Turra Longitudinal and Source-Bordering Dune sites showing the surveyed dune crest, the outline of the longitudinal dune, swale and Cooper floodplain (so-uaui) urBidpoojj sAoqs tuSigjj o ^ ° ' 10 —i —i m o i o +T- + 4- o 00 o o o O o O o •51- O o VO (N o o 00 o o o m a- TJ X o S a o Sand y San d Cla y o Silt y z 1 O O m -, "g .3> 1 (S9.U91U) ure|dpoo|j oAoqu ;uSi9H tq B ^ "Rh o bo IN J! R ^ tHJ CJ CO l-c •4-CJ1 o 3 _-ia TJ H CJ o TJ 6 o U <+H (N *-ol OJ CO S3 CJ CJ .3 E CJ o o 6frsi o o ca *cr CJ 7 cd TJ •a CJ % o .a § X)ca o o •r«i1 CO o (B oO VO S5 1 H-J CJ OJ 2 £6D CO 3 ri(Cj ca CoJ o CH—I o -O OJ .3 o CO 00 s0 Q .5 ri•M TJ 3 "ed "p. 13 .3 Q T3 •8 "ra 4! C o o ra o •i 1 OT o i g 3bo J33 J "32 00 TJ (0 ro O 3 O .s .Q - CN OJ 6u0 T3J (IS b tH .s 60 1CO ToJ • •H o h .3 W 5 TJ ra TJ >, • o u OJ T3 >. E PQ PQ ra ra J2S O I CJ o » o OJ o OJ - ^r o ... I-H % i L^i. ••'--'•-' on o o c3 CD CJ C/j l-c ,3 obO c H C(-H o o Qo co^ o o o IT) 61) 3 .3 CO O o C/1 o o l-l co in O S 5M? o o o CN rt — o o o 3 3 o UH o f«-J 00 00 3 5 CO CO o o in m 151 6.2.3.1 Turra Channel and Overbank Facies Auger Hole 1 A clay unit of at least 0.80 m thickness is located 4.80 m below the present surface (Figure 6.26) and consists of mottled (grey/brown), manganese and carbonate- mineralised clay. The clay is overlain by 0.30 m of creamyfine-grained fluvial san d which is overlain by 0.40 m of grey clay, similar to the lower clay unit and 0.20 m of very poorly sorted (2.25 3.10 m consists of very poorly sorted (3.03 (J>), sub-angular to rounded, olive yellow (2.5Y 6/6), veryfine-grained (3.83 (J)) silty sand which forms the modern floodplain. Auger Hole 2 The lowermost unit starting at 5.0 m below the surface consists of at least 1.0 m of fine grainedfluvial sand that has not been lithified (Figure 6.26). Also present in the sand is mottled (brown/grey/black) clay and carbonate precipitates which increase with depth. The base of this unit gave a TL date of 84.9+12.1 ka (W2472; Figure 6.26). This fluvial sand unit is overlain by 0.15 m offine-grained sand , mottled clay and carbonate, which in turn is overlain by 2.65 m of very poorly sorted (2.84 (|)-3.20 ())), sub-angular to well rounded, yellow (2.5Y 7/6), indurated sandy coarse silt (4.67 Auger Hole 3 The base of the auger hole at about 9.20 m below the surface, consists of at least 1.25 m of poorly sorted (1.70 d>), sub-angular to well rounded, white (2.5Y 8/2), fine-grained (2.40 (|))fluvial sand . This is overlain by 3.00 m of poorly sorted (1.17 §), sub-angular to 152 well rounded, yellow (2.5Y7/4), medium-grained (1.22 (j>)fluvial sand fining upwards that gave TL dates of 231+54 ka (W2475) and 118+14 ka (W2474; Figure 6.26). The medium-grained sand consists of quartz (91%, some with inclusions), metaquartzite (7.5%) and rock fragments (1.5%). Overlying this is a 0.60 m thick, mottled (grey/brown/black) clay unit that underlies 3.00 m of very poorly (2.80 (j>) to poorly sorted (1.30 q>), angular to well rounded, pale yellow (2.5Y 7/4),fine-grained (2.8 5 (j>) fluvial sand that gave a TL date of 74.7+13.3 ka (W2473; Figure 6.26). Thin section analysis of thefluvial sand shows it consists of quartz (84.5%, some with inclusions), metaquartzite (8.5%), rock fragments (5.0%), chert (1.5%), and feldspar (0.5%). The uppermost unit consists of 1.40 m of modern silty sand. Auger Hole 4 Auger Hole 4 is located at the point where the source-bordering dune comes into contact with thefluvial sediment s (Figure 6.26). At the base of the auger hole at 5.20 m below the surface is a 1.00 m thick compacted, mottled (brown/grey/black) silty clay unit consisting of poorly sorted (1.90 §) to very poorly sorted (2.42 (J>), light brownish grey (2.5Y 6/2),fine to medium silt size (6.78 3.30 m of very poorly (2.80 (j>) to poorly sorted (1.07 <])), sub-angular to rounded, pale yellow (2.5Y 7/4), coarse silt (5.11 (()) tofine-grained (2.6 4 (j>) floodplain sand with some clay pellets, root traces and a thin clay lens suggesting watertable movement and cementation. Thefloodplain sand gave a TL date of 71.2+6.8 ka (W2470; Figure 6.26). Thin section analysis revealed a composition of quartz (90.5%), metaquartzite (4.5%), opaque minerals (0.5%), zircon (0.5%), rock fragments (3.0%), clay pellets (0.5%) and feldspar (0.5%). Approximately 1.50 m of hard, silty sand with gypsum nodules overlies this sand and forms the modern Cooper floodplain. 6.2.3.2 Turra Source-Bordering Dune Auger Hole 1 Auger Hole 1 is located on an 11.80 m high source-bordering dune approximately 600 m north of Turra Palaeochannel Auger Hole 4 and 290 m southeast of Auger Hole 2 located on the longitudinal dune (Figure 6.24 and Figure 6.27). This section is composed entirely of aeolian sand. The base of the section consists of at least 2.0 m of 153 poorly sorted (1.06 d))? sub-angular to well rounded, yellow (10YR7/8), fine-grained (2.23 (j>) aeolian sand and carbonate nodules that gave a TL date of 116+17 ka (W2674; Figure 6.27). The mineralogy of the sand and carbonate unit consists of quartz (96.5%), metaquartzite (2.5%), chert (0.5%), opaque minerals (0.5%) and clay pellets (0.5%). This is overlain by 3.70 m of moderately sorted (0.75 <|)), sub-angular to well rounded, reddish yellow (7.5YR 6/8), fine-grained (2.54 (j)) sand that gave a TL date of 41.4+4.0 ka (W2673; Figure 6.27). This is overlain by 1.30 m of moderately sorted (0.77 (()), brown (10YR 5/3),fine-grained (2.72 (f>) clayey sand. The uppermost unit consists of 3.0 m of moderately sorted (0.75 (|)), sub-angular to well rounded, brownish yellow (10YR 6/6),fine-grained (2.3 4 6.2.3.3 Turra Longitudinal Dune Auger Hole 2 This auger hole is located 16.3 m above thefloodplain o n the crest of most southern location on a longitudinal dune (Figure 6.27) near where it adjoins the source-bordering dune it was derived from. It forms one of a series of auger holes drilled along the length of this dune. The lowermost unit is aeolian and consists of at least 5.30 m of very poorly sorted (2.51 <))), angular to well rounded, brownish yellow (10YR 6/6), very fine-grained (3.88 d>) aeolian sand that gave TL dates of 25.4+2.5 ka (W2477) and 21.0+1.9 ka (W2476; Figure 6.27). The mineralogy of the aeolian sand unit consists of quartz (94.0%), metaquartzite (2.0%), chert (0.5%) and rock fragments (93.5%). This is overlain by 1.70 m of poorly sorted (1.77 (J>), yellow (10YR 7/6),fine-grained (2.56 (1.51 <()-1.66 d>), angular to well rounded, brownish yellow (10YR6/6), fine-grained (2.66 d>-2.83 The uppermost sand unit contained quartz grains that were coated with iron oxide/haematite, which was absent from the lowermost sand unit. 154 Auger Hole 3 This section consists of 11.40 m of moderately (0.87 4>) to moderately well sorted (0.65 ())), sub-angular to rounded, yellow (10YR 7/6) and brownish yellow (10YR 6/6), fine-grained (2.21 Auger Hole 4 The base ofAuger Hole 4 is composed of at least 1.70 m of very poorly sorted (3.14 §), brownish yellow (10YR6/6), medium silt size (5.05 TL date of 103+12 ka (W2481; Figure 6.27). This is overlain by 1.70 m of very poorly sorted (2.56 d>), yellow (10YR7/6), very fine-grained (3.97 cb) sand and carbonate nodules (aeolian). This, in turn, is overlain with 0.10 m thick lens of poorly sorted (1.88 (J>), sub-angular to well-rounded, brownish yellow (10YR6/8), medium-grained (1.66 ()>)fluvial sand, the mineralogy of which consists of quartz (95.5%), metaquartzite (3.0%), rock fragments (1.0%) and clay pellets (0.5%). The quartz grains contained inclusions of rutile and occasional heavy minerals are present. The longitudinal dune unit, 6.90 m in thickness, consists of very poorly sorted (2.95 (J>) to poorly sorted (1.12 <))), sub-angular to well rounded, brownish yellow (10YR6/8) silt (4.12 to fine-grained (2.60 <))) aeolian sand that gave a TL date of 4.3+0.4 ka (W2480; Figure 6.27). The mineralogy of the aeolian sand unit consists of quartz (91.0%), metaquartzite (5.5%), rock fragments (1.5%), chert (1.5%) and clay pellets (0.5%). Auger Hole 5 The base of Auger Hole 5 (Figure 6.27) consists of at least 0.50 m of moderately sorted (0.79 (f)-085 <|>), sub-angular to rounded, yellow (10YR 6/6),fine-grained (2.1 9 fluvial sand with a few carbonate nodules. Its mineralogy consists of quartz (92.5%), rock fragments (4.0%), metaquartzite (2.5%), feldspar (0.5%) and chert (0.5%), with 155 very little iron oxide/haematite coating of the quartz grains. This unit appears to be eitherfluvial or slope wash in origin as it occurs below the level of the present day floodplain. A very thick 10.50 m aeolian unit overlies this, consisting of moderately well sorted (0.63 Auger Hole 6 The lowermost unit of Auger Hole 6 consists of at least 2.30 m of coarse silt size (4.63 §), very poorly sorted (3.03 (J)), angular to rounded, brownish yellow (10YR 6/8) clayey sand (fluvial) that gave a TL date of 82.1+7.0 ka (W2479; Figure 6.27). The mineralogy consists of quartz (95.5%), metaquartzite (2.0%), rock fragments (1.0%), feldspars (0.5%), chert (0.5%) and opaque minerals (0.5%). Haematite, zircon and some carbonate nodules were also noted. This is overlain by 8.70 m of poorly sorted (1.01 §- 1.94 (|)), sub-angular to well rounded, yellow (10YR7/6) and light yellow brown (10YR 6/4),fine-grained (2.12 d>-2.84 (|>) aeolian sand that gave a TL date of 3.7+0.6 ka (W2478; Figure 6.27). The aeolian sand grains were heavily coated in iron oxide and the mineralogy consists of quartz (93%), metaquartzite (3%), rock fragments (2%), clay pellets (1%), zircon (0.5%) and chert (0.5%). 6.2.3.4 Interpretation of Turra Sometime between late OI Stage 8 to early OI Stage 5 palaeochannels deposited channel sands and probablyfloodplain mud s over a wide are (Figure 6.28). These deposits were reworked during a period fluvial activity in OI Stage 5 and sand was blown out of these channels and deposited northwards adjacent to source-bordering dunes at the same time. Between OI Stage 4 and OI Stage 1, the area supported channels that continued to transportfine-grained channel sands. Southerly winds produced a second stage of the source-bordering dunes from these channels during OI Stage 3 (Figure 6.28). During the LGM (-25 ka to 20 ka) there was nofluvial activit y recognisable in this area however there was further aeolian activity, probably sand eroded from the windward south face of the source-bordering transverse dune being moved to the leeward or northern face. The 156 LGM is commonly associated with strong winds transporting and reworking large amounts of aeolian sand into substantial dunes (Wasson, 1983a,b). During OI Stage 1 additional aeolian sand was eroded from the source-bordering dune to produce a longitudinal dune extending in the direction of the prevailing wind. The longitudinal dune started to form in the Early Holocene or very Late Pleistocene. After about 5 ka, there was substantial growth with sand extending northwards at approximately 1 m per year until about 3.7 ka. In summary, the longitudinal dune started forming around 9 ka and steadily migrated northward towards one of the present Cooper Creek channels. There does not appear to have been much northward extension after about 3.7 ka. 6.2.4 Gidgealpa Area East Dog Bite Lake, North Dog Bite Lake 1, North Dog Bite Lake 2, Gidgealpa South and Gidgealpa Dune are located in the Cooper 'fan' area known as Gidgealpa which is located 62 km southwest of Innamincka (Figure 1.4B and Figure 6.22). The Dog Bite Lake sites and Gidgealpa South site consist of auger holes drilled near palaeochannels and source-bordering dunes previously identified by Wasson (1982, 1983a,b). 6.2.4.1 East Dog Bite Lake The stratigraphy of this 4.50 m auger hole (Figure 1.4B and Figure 6.29) consists of at least 0.20 m of a grey clay unit at the base containing gypsum crystals, which is overlain by 0.45 m of poorly sorted (1.14 <|>), sub-angular to well rounded, yellow (2.5Y 7/6), medium-grained (1.93 87.5+8.3 ka (W2246; Figure 6.29). The mineralogy of the channel sand consists of quartz (93%), metaquartzite (3%), and rock fragments (4%). About 0.65 m of coarse grained sand, 0.35 m of fine-grained sand and 0.55 m of mottled clay overlie the lowermost sand unit. The uppermost unit consists of 2.30 m of silty sand and pelleted floodplain mud with carbonate nodules and gypsum crystals. CO •IJ "o .3 i- "3 § •ja w ca co J3 60 O .3 co 1 2 C/J ca f o 60 TJ 5 •a ca (N•a OJ .3 PQ 6D O Q o Z CJ" ca oa 60 o Q ca W | -i-» o CJ CO (S9.U9UI) uiBjdpooi j A\opq qjdoa • I—I ta 3 C/3 ON (N CO vo CJ 1 2 OT >. -a u c 2 CO SL O O ro OT PQ 60 O Q ca t § o o CO | 2 I •a H-l OJ s H o (N 4Q3 JJ Q a t. Tt "o ca o £ DO .3 £< • c/3 i— ca S3 CJ o So 60 3 TJ o '> *- .3 "8 £ 3 •& O 43 s i o .2 .2 13 —— ra •a *o • ro O 3 co i3 w S3 ca u< _ ft §•8 ca "ca 60 o TJ ca o 5 a to '•2£ ?S CJ 3 B A cu 4n3 CO CO CO O CO CO oUc ca o o Ui ca % O o ca TJ o o o o o o o feb3 o q o o o ca o o o o •—M •"* oo ca 6.2.4.2 North Dog Bite Lake 1 The lowermost unit of this 4.0 m deep auger hole consists of at least 1.55 m of moderately well sorted (0.54 (J>), rounded to angular shaped, white (10YR 8/2), fine grained (2.94 $) laminated fluvial sand that gave a TL date of 66.3+6.7 ka (W2247; Figure 6.29). The mineralogy of the fluvial sand consists of quartz (87%), rock fragments (7.5%), metaquartzite (4%), sand-sized clay pellets (1%) and feldspar (0.5%). Heavy minerals such as zircon were also present. The uppermost 2.45 m of floodplain silty sand is the same as the uppermost unit described previously at East Dog Bite Lake. 6.2.4.3 North Dog Bite Lake 2 North Dog Bite Lake 2 is only -100 m south of North Dog Bite Lake 1 (Figure 6.29). This auger hole was drilled with a drill rig since the North Dog Bite Lake 1 auger hole could not penetrate any farther than 4.0 m with a hand auger. The lowermost 0.35 m consists of mottled (blue/grey) clay and could not be penetrated by the auger drillrig any farther than 7.80 m in depth (Figure 6.29). This predominantly clay unit includes some poorly sorted (1.20 The overbank clay is overlain by 2.45 m of poorly sorted (1.01 (10YR6/4), medium-grained (1.68 5.0 m of moderately sorted (0.86 ((>), greyish brown (10YR 5/2),fine-grained (3.2 9 (J>) silty sand, which also forms the uppermost unit of North Dog Bite Lake 1, East Dog Bite Lake and Gidgealpa South (Figure 6.29). 6.2.4.4 Gidgealpa South At a depth of 6.95 m, the Gidgealpa South auger hole is composed of at least 1.80 m of poorly sorted (1.38 (j)-1.64(j)), pale yellow (2.5Y7/3) and light grey (2.5Y7/2), fine (2.07 (f>) to very fine-grained (3.25 <))) sand (Figure 6.29). The unit includes some mottled clay; carbonate nodules and pedogenesis indicatingfluvial floodplain origins. Overlying the fine sand is 0.20 m of medium-grained sand which, in turn, overlain by a 0.45 m thick grey clay unit. This is overlain by a 3.90 m thick very poorly sorted (2.22 (j>) to moderately well sorted (0.73 (2.5Y7/8) and pale yellow (2.5Y7/3), coarse to medium-grained (0.97 d>-1.34 d>) channel sand. The fluvial sand consists of quartz (95.5%, some with inclusions), 160 metaquartzite (3.5%) and rock fragments (1%). The channel sand is overlain by 0.60 m of the same type of silty sand present at East Dog Bite Lake and North Dog Bite Lakes 1 and 2. 6.2.4.5 Gidgealpa Dune This section consists of at least 0.60 m of poorly sorted (1.63 <)>), reddish yellow (7.5YR 6/8),fine-grained (2.67 (W2249; Figure 6.30). This is overlain by 6.85 m of poorly sorted (1.59 cj)), sub-angular to well rounded, reddish yellow (7.5Y 6/6),fine-grained (2.62 sand that gave a TL date of 23.6+6.7 ka (W2248; Figure 6.30). The aeolian sand is composed of quartz (93%), metaquartzite (4%) and rock fragments (3%). 6.2.4.6 Interpretation of Gidgealpa Area The palaeochannels indicate an actively meandering channel during late OI Stage 5 and Stage 4 (-87 ka to 66 ka). These meandering channel patterns can be seen through the Gidgealpa area in the LANDSAT TM images (Figure 6.22). It is very likely that the large source-bordering dune (Gidgealpa Dune) originally formed at that time, supplied with sand from the palaeochannels, as at Turra. A single date of 23.6+6.7 ka from the upper part of this dune (at Gidgealpa) suggests aeolian reworking of the prior dune during the LGM, similar to that discussed for the Turra dune (see Section 6.2.3.4). 6.2.5 Strzelecki Creek and Strzelecki Dunefield Strzelecki Creek has been recognised as an alternative path for flow from Cooper Creek during large floods (e.g. Wasson, 1982a,b) and as a possible earlier main channel of Cooper Creek. For this reason, both the alluvium from palaeochannels along its length, and the deposits from longitudinal dunes parallel to the creek, andflanking th e present course of the creek east and west, have been sampled and analysed for sediment characteristics and TL ages. The Mudlalee site is located on the contemporary channel of Strzelecki Creek approximately 85 km south of Innamincka along the Old Strzelecki Track (Figure 1.3 and Figure 6.31). The location consists of the Mudlalee 'channel' of Strzelecki Creek and associated overbank facies, the West Mudlalee Dune, immediately west of the 161 Strzelecki Creek, and the East Mudlalee Dune immediately east of Strzelecki Creek (Figure 6.32). The Mudlalee 'channel' is an extremely subdued feature about 4 km wide mostly covered in vegetation consisting of river gums and lignum. Auger holes were drilled through the floodplain to locate the overbank facies and Strzelecki Creek palaeochannels (Figure 6.31, Figure 6.33 and Figure 6.34). The two Mudlalee Dunes (West and East) are longitudinal dunes located adjacent and parallel to the contemporary Strzelecki Creek and are probably derived from source-bordering dunes associated with palaeochannel meanders some 5 km to 6 km to the south (locations near Strzelecki Creek where it appears to have flowed west to east across the prevailing wind direction) (Figure 6.31). West Mudlalee Dune is pale brown in colour and East Mudlalee Dune is a red/brown colour, but both are approximately the same height. The relationship between the Strzelecki palaeochannels and the dunes is discussed further in Section 6.2.5.4. 6.2.5.1 Mudlalee Channel and Overbank Facies Auger Hole 1 The base ofAuger Hole 1 (Figure 6.33) consists of at least 5.10 m of very poorly sorted (3.29 §) to poorly sorted (1.18 (f>), sub-angular to rounded, white (5Y 8/1) to pale white (2.5Y 8/3)fine-grained (2.4 4 4>-2.46 §) channel sand that gave TL dates of 169+18 ka (W2664) at a depth of 5.50 m and 110+12 ka (W2736) at a depth of 2.30 m (Figure 6.33). The mineralogy of the channel sand consists of quartz (90.5%), metaquartzite (6%), chert (1.5%), rock fragments (1.5%) and opaque minerals (0.5%). Overlying the sand is about 1.0 m of clayey sand, which in turn, is overlain by about 0.10 m of silty sand that forms the uppermost sequence (floodplain). Auger Hole 2 The lowermost unit (Figure 6.33) consists of at least 0.20 m of extremely poorly sorted (4.80 (J)), very pale brown (10YR7/4);fine-grained (2.2 6 (j)) channel sand, mottled clay and ferricrete pebbles. This is overlain by 0.80 m of very poorly sorted (3.41 (|>), sub- angular to well-rounded, pale yellow (2.5Y 7/4),fine-grained (2.2 6 (|>) channel sand and carbonate nodules. The mineralogy consists of quartz (92.5%), metaquartzite (5%), rock fragments (1%), chert (1%), and opaque minerals (0.5%). This is overlain by 162 0.60 m of clayey sand (upper point bar or overbank), which in turn is overlain by 0.60 m of silty sand (floodplain). 1W2S'E 140'3O-E Contemporary ff Strzelecki Creek fi\- East Mudlalee + + West Mudlalee\ 1 1 Mudlalee Channel and w Overbank J ransect , • i / '> ' t I '• r m ..Wif: I M % O o H < ••:. Hi • CM -# Flow Directi* M,' -. i > ' i kilometers '. * W i £ • ." - f 140°25"E 140*30^ Figure 6.31: LANDSAT TM image of Mudlalee site showing the location of Mudlalee channel and overbank facies (28°16'43"S, 140°29'33"E), West Mudlalee Dune (28°16'29"S, 140°27'34"E) and East Mudlalee Dune (28°16'00"S, 140°31'45"E) sites. 1 West Mudlalee Dune Auger Hole East Mudlalee Dune Auger Hole i i f . • \ Mudlalee Channel and / \ Overbank Section M Pale Longitudinal filik AH1 AH2 AH3 AH4 / Red Longitudinal \ / '*"" Wk ii /i i Dune \ . , Fluvial Sediments 9 ^\ :^ ? • \!-H-l..! H.-! S-H V.~H~i / Figure 6.32: A schematic cross-section across the Mudlalee channel site (Auger Holes 1 to 4) and associated longitudinal dunes (West Mudlalee 28°16'29"S, 140°27'34"E and East Mudlalee 28°16'00"S, 140°3r45"E). Auger Hole 3 The lowermost unit (Figure 6.33) consists of at least 0.20 m of fine-grained clayey sand with large carbonate nodules located at the base of this section (upper point bar or overbank). This in turn is overlain by 1.60 m of clean, white,fine-grained channe l sand, which is overlain by 0.40 m of clayey sand (upper point bar or overbank) with 0.80 m of silty sand forming the uppermost unit (floodplain). Auger Hole 4 The base of the auger hole (Figure 6.33) consists of at least 1.20 m of moderately sorted (0.99 ())), white (2.5Y 8/2),fine-grained (2.5 6 (|>) channel sand. This is overlain by about 0.20 m of medium-grained sand, large carbonate nodules and fluvial gravels which formed a channel base. This in turn is overlain by 1.45 m of very poorly sorted (2.64 §), sub-angular to rounded, pale yellow (2.5Y 7/3), coarse-grained (0.58 <|>) channel sand that gave a TL date of 159+29 ka (W2666; Figure 6.33). The mineralogy of the channel sand consists of quartz (97%), metaquartzite (2%), chert (0.5%) and rock fragments (0.5%), with heavy minerals and quartz with rutile needles. This is overlain by 1.75 m of medium-grained channel sand and 1.20 m offine-grained channe l sand that gave a TL date of 118+11 ka (W2662; Figure 6.33). The channel sand is overlain by 1.0 m of fine grained clayey sand (upper point bar or overbank) which in turn is overlain by 1.20 m of •o TJ C c ra TJ ra CO co >. 5 8> 3? S. -a TJ -Q .s v5 ra CS -CQJ rt co 0 CO CO 0- CL -o o nrr— W: n. f v - - - ? •E 'rZ-Z-Z '. «"." f>w \--~-** * A u8 3 « tal CO «* 4J ;J O .'.*..'.j ,, .*.'.'.*.} ' X : 1 i- ^pvj:-:-:-»:-:*:*: : •X>>>> 4) i •Y//:':7:Y:Y: bO i •••• • "^L' •'•' - • < U tiE J2 l 1 J2 2I] 1 O N. jg cn - C3 ^ ' ITIO) +*-7I ^ IDCO CM ro i <° N 7 co + CM T- B *-< o .3 vo VO ci] aj $ SP fO c/} 55 CJ E O o o "ra ~3 ui 8 3 Ui 3 % E 3 •3 I I • • H-H o 1 1 OH • • § ( | /\ OJ 1 1 " !>• '•8 Ui • • f • X 1 ^ Cfl l-c "N 1 1 1/1 •* £ u • • bO § 11 1 1 1 • i' c 111 c c > i 111 , , 1 "i , . 1 c I c , 1 c I 1 c 1 1 1 1 1 1 1 1 1 1 1 •S 1 F i i i 1 1 1 1 1 1 c o o o OOOOOO c3 O OC o o o o o o o o o 3 —i moderately well sorted (0.96 (|>), sub-rounded to well-rounded, white (2.5Y 8/2), medium-grained (1.12 Clearly, there is a major age reversal with depth in this profile (Figure 6.33). This is the only significant stratigraphic age reversal obtained in this study and the reason for it is unknown. Samples W2665 and W2662 both have excellent TL properties and it is possible that they were reversed during labelling. If this were to be the case and their locations corrected, then all five TL dates at this cross-section would show good age consistency in relation to their stratigraphic position. 6.2.5.2 Mudlalee Dunes East Mudlalee Dune The base of this section at 11.54 m below the dune crest (Figure 6.35) consists of at least 0.20 m of very poorly sorted (3.16 (j>), light yellowish brown (10YR 6/4), mottled clayey medium silt (5.10 ())). This is overlain by 1.30 m of very poorly sorted (3.85 (j)), sub- angular to well-rounded, reddish yellow (5YR 6/8), very fine-grained (4.00 (j>) clayey sand that gave a TL date of 56+6.6 ka (W2461; Figure 6.35). It consists of quartz (92.5%), metaquartzite (4%), rock fragments (3%) and feldspar (0.5%). Overlying the fluvial units is a 0.75 m thick very poorly sorted (3.34 §), sand silt (4.97 (j>) unit which is overlain by 7.80 m of very poorly sorted (2.51 5YR6/8), very fine (3.60 SSS .-.V •••••••• O - o it cn U T3 •* 2 — C o Ui _ >> d — in - CmN a « u ~ +H an M 53 1 St a St a 0 1 0 1 OJ i uvia l solia n o Q < E -- o CN -a /- / -v— -^ • • ^\ ( ^"^^ —»^^ " o ^"\ ' s\\ in •* ^\ . g .s \ • 3 3- ^ ^I •83 -o2 -s^ \\ -. - gu, \ «* - an \ 1 1 _1 cell c . c 1 c J C 1 1 c C • c 1 C • c C 1 C 1 c l_l | | | 1 1 1 1 1 1 - o H-1 1 ' 1 11'1 1 1 1 1 I 1 O O O O O O C D o o O O O O p p C3 tin § c -T O CO m >. o >. CO ra O o (N u. •JT* ^ > M 8 C/J o u Ui Ui 3 l-H O K I Q t o gp o o u. - OJ -a bii p 3 CJ o o o o CN (SQXJSUI) uiBidpoou 9Aoq^ tqSiSH iH 169 West Mudlalee Dune The base of this auger hole at about 11.50 m below the crest of the dune (Figure 6.36) is 2.60 m of very poorly sorted (2.56 (j)-3.20 1.84 §), well rounded to angular shaped, yellow (10YR7/6) and brownish yellow (10YR 6/8), veryfine-grained (3.6 5 6.2.5.3 Merty Merty The second site located along Strzelecki Creek was located at Merty Merty, near Merty Merty Homestead approximately 42 km south of the Mudlalee site and 127 km south of Innamincka along the Old Strzelecki Track (Figure 6.37). Here the auger holes were drilled through the contemporary Strzelecki Creek floodplain to locate palaeochannel sediments for TL dating and sedimentological analyses (Figure 6.37 and Figure 6.38). No dune samples were obtained from the Merty Merty location. Auger Hole 1 The base of the auger hole consists of at least 0.30 m of mottled (grey/brown) clay with carbonate nodules (Figure 6.38). Overlying the clay is 0.50 m of a medium-grained sand unit that gave a TL date of 41.2+3.9 ka (W2253; Figure 6.38). This is overlain by 1.15 m of very poorly sorted (3.24 (2.5Y 7/3), coarse silty (4.00 (b-4.64 §)fluvial sand unit gave TL dates of 10.9+0.9 ka (W2252; Figure 6.38) and 14.1+1.2 ka (W2251; Figure 6.38). The mineralogy of the fluvial sand consists of quartz (91.5%), metaquartzite (4.5%), rock fragments (2%), 170 chert (1.5%) and feldspar (0.5%). The uppermost unit consists of 3.85 m of silty sand that forms the modernfloodplain o f Strzelecki Creek. Figure 6.37: LANDSAT TM image Strzelecki Creek and the Strzelecki dunefield showing the location of the Merty Merty (28°35'39"S, 140°16,04"E) site. Auger Hole 2 The lowermost unit (Figure 6.38) consists of at least 2.20 m of poorly sorted (1.79 <|)- 1.90 (j>), sub-angular to well-rounded, yellow red (5YR5/6) and yellow (2.5Y 7/8), medium-grained (1.50 Ui u 0< . (sonoui) ureidpoou Mojsq qjd3Q Ui u s VI O u 8 o O o O OT E OT 00 P Ui •1M u Ui 3 <8 ~\ ^~ ~->> S P 'o OT X P fe P I f OT cn w g p u O "8 ro bO fe .a o SP I •V5 5 OT P I J P O fe-> OJ 2 o «4M I o g •8 " p o OT Ui I w "8 a p & OT OT 1 3' Q % I 2 § o E S, i i i i i i _l I I P-l L. -H o o o o o o o o E © 3 o o o o o q VO o fN V) (S9jj9ui) ureidpoo^ Mopq qidaQ 6\ cn vo I 173 Auger Hole 3 A well-sorted, creamy, fine-grained sand unit at least 2.80 m thick is located 5.0 m below the present surface (Figure 6.38). This is overlain by 0.75 m of well-sorted, clean, orange/brown, coarse-grained channel sand, which in turn is overlain with 0.45 m of gritty, medium-grained channel sand. The uppermost unit consists of 1.20 m of silty sand (floodplain). Auger Hole 4 The base of the auger hole (Figure 6.38) consists of at least 0.20 m of a well-sorted, creamy, medium-grained channel sand unit. This is overlain by 3.0 m of well-sorted, creamy, fine-grained channel sand, which in turn is overlain by 0.90 m of silty sand (floodplain). 6.2.5.4 Interpretation of Strzelecki Creek and Dunefield Abandoned channel sands beneath Strzelecki Creek date from OI Stage 6 or earlier (Figure 6.34). OI Stage 5 sands overlie these channel sands and at Merty Merty there is a thin unit of OI Stage 3 alluvial sand with a Late Pleistocene or Holocene channel infill. Scrolls at the surface suggest that the OI Stage 5 and Stage 3 channels migrated laterally infilling with sand around OI Stage 5 and is overlain with overbank deposits. The TL date of 171+17 ka which overlays a younger date of 118+11 ka could be the result of incorrect labelling of samples in the field. An alternative explanation is that W2665 could result from older fluvial sediments deposited without there being suitable conditions for bleaching of the previous TL signal. If the former is assumed, a schematic cross-section can be constructed placing the fluvial and aeolian units in context (Figure 6.40). Fine uppermostfluvial clayey sand deposits buried beneath the dune at Mudlalee were dated at OI Stages 5 and 3. Deeper and coarser channel sands and finer overbank sands at Merty Merty were deposited during OI Stage 3 and late Stage 2, respectively (Figure 6.35, Figure 6.39 and Figure 6.40). Directly above the overbank deposits (West Mudlalee Dune) the longitudinal dunes formed during OI Stage 2 (Figure 6.36). An estimate of the accumulation rate from the two TL dates in the dune indicates that the dunes may have begun to form between 25 ka 174 and 20 ka, an interpretation that agrees with Wasson's (1983a,b) interpretation that dune formation commenced around 23 ka in the Strzelecki Desert. However, Gardner et al. (1987) dated dunes in the Simpson Desert between 240 ka and 220 ka. Figure 6.40: A schematic cross-section across Strzelecki Creek and Strzelecki Desert showing the stratigraphy and chronology of the depositional units. A similar extrapolation of TL ages suggest the East Mudlalee Dune formed around 13 ka with rapid accumulation of sand building the dune up to almost to its current height by about 10 ka. From such extrapolations there is possibly 10 ka difference in TL age between the two dunes that are only separated by roughly 5 km in distance, the West Mudlalee Dune being older than East Mudlalee Dune. While Strzelecki Creek has been constrained between the longitudinal dunes since OI Stage 2, prior to this it was probablyfree to laterally migrate along much of its length. 175 CHAPTER 7 SUMMARY AND REGIONAL CONTEXT 7.1 INTRODUCTION This investigation of the Quaternary palaeoenvironmental history of the Innamincka region adds to thefirst detailed geomorphic, stratigraphic and chronological studies of this area of South Australia by Wasson (1982, 1983a, 1986). It also relates closely to similar studies further upstream in the Windorah to Wilson Swamp reach of Cooper Creek in Queensland conducted by Nanson et al (1986, 1988, 1992a), Rust and Nanson (1986) and Maroulis (2000), and studies of volume changes in Lake Eyre at the terminus of the Cooper (Magee et al, 1995; Magee and Miller, 1998; Magee, 1997, Nanson et al, 1998). The Innamincka region is particularly interesting because it consists of a very low-gradient alluvial 'fan' formed where Cooper Creek debouches from a valley incised through the Innamincka Dome. The Cooper has switched its course across the 'fan' at various times in the Middle to Late Pleistocene leaving a complex array of palaeochannels, source-bordering dunes with derivative linear dunes, terminal lakes and swamps (Figure 6.1, Figure 6.7 and Figure 6.22). At times during this period it appears as though a substantial portion of the Cooper Creek discharge was been diverted down Strzelecki Creek to the Lake Frome basin, making the region one of the most complex in Australia in terms of disrupted Quaternary drainage. In this study, sediments and stratigraphic sequences from 38 auger holes and 4 exposed cut-bank sections, dated using 69 TL determinations, were analysed for evidence of then- physical characteristics, modes of sediment transport and depositional chronology. It is apparent that, regardless of their present depositional environment, these sediments have undergone a diverse history of reworking influvial, aeolia n and some in lacustrine situations. This has made textural differentiation difficult, nevertheless, the sedimentary stratigraphy of the Innamincka region retains a detailed and revealing record of Quaternary environmental change in central Australia dating back at least two glacial cycles (-200 ka). The stratigraphy and TL chronology described in detail in Chapter 6 is summarised in this chapter so that comparisons can be made with previous research into Australian palaeoenvironmental change undertaken both within and beyond the Innamincka region. This summary takes the form of identifying the major findings from each of the study 176 locations, combining these into an overall synthesis of Quaternary environmental change in the region, andfinally a comparison of this region with other terrestrial records from northern and central Austalia. 7.2 SUMMARY OF PALAEOENVTRONMENTAL CHANGES AT SPECIFIC LOCATIONS IN THE TNNAMINCKA REGION 7.2.1 Coongie Lakes Quartz-rich lunettes form on the lee shore of some semi-arid environment lake systems during high water phases (Bowler, 1986). Basal lake-shore deposits in a well-developed lunette located on the northern shore of Lake Marroocutchanie (Figure 6.1) is convincing evidence that a substantial lake existed here at about 109+14 ka (Figure 6.1 and Figure 6.3). The lunette overlies lacustrine sediments, the upper part of which were probably associated with the same OI Stage 5 lake that formed the lunette. A lower well-mottled and gypcreted unit probably represents freshwater Tertiary Namba or Etadunna Formation. The bulk of the sand ridge forming the present lunette appears to have resulted from northward (leeward) Holocene reworking of the original OI Stage 5 feature but under relatively dry conditions to enable the reworking to occur. Although a comprehensive investigation of the Coongie Lakes area remains to be undertaken, this study obtained no evidence of lakes existing in this area during late OI Stage 5, Stage 4, Stage 3 or the LGM. Furthermore, it is clear that the lake system was essentially dry after the LGM, for longitudinal dunes composed offine-grained aeolia n sand TL dating at 16.1+1.4 ka and 8.6+0.9 ka advanced northwards over a mostly dry lake floor (Figure 6.1 and Figure 6.4). Although the present lakes have water in them, they appear to be significantly reduced in area from those of OI Stage 5, with longitudinal dunes having encroached on their southern margins. From the limited evidence obtained during this study it appears that the Coongie Lakes are most active during close-to-maximum interglacial conditions, although less so in the Holocene than in OI Stage 5. A question remains as to what happened to the Lakes during the fluvially active and presumably relatively wet periods from late OI Stage 5 to Stage 3. There are several possibilities. Firstly, Cooper Creek may have laterally migrated southwards across the Cooper 'fan' resulting in a reduction in the water supplied to the Coongie Lakes area in the north. Secondly, and perhaps similarly, the floodwaters that flowed 177 through the Innamincka Dome may have been largely diverted south down Strzelecki Creek, partly abandoning the northern lakes. Thirdly, the Cooper channel may have been flowing in its present northwesterly direction but with its northwards flow contained at Tirrawarra Swamp (a natural depression) (Figure 2.19), with insufficient water reaching the lakes further north. Finally, evidence may be found in the lunettes of the other Coongie Lakes for additional periods of inundation during OI Stages 5 and 3. 7.2.2 Northwest Branch and Cooper 'Fan' Palaeochannels Temporal changes in the extent and texture of alluvial deposits on Australian rivers have been previously interpreted as indicative of climate change (e.g. Nanson et al, 1988, 1992a; Page et al, 1996). Extensive alluvial deposits along Cooper and Strzelecki Creekfloodplains provide evidence of more active river systems than presently occur in the Innamincka region. Cooper Creek today supports no active gravel transport (some armoured gravel lags exist), very little sandy point-bar deposition and no evidence of lateral channel migration. Pleistocene palaeochannel planform and stratigraphy exhibit convincing evidence for all of these processes being operative at various times. There is evidence for Tertiary-age palaeochannels of Cooper Creek downstream of the Innamincka Dome. A basal layer of sand and silcrete pebbles located at Wills Grave (northwest branch of Cooper Creek) (Figure 6.16 and Figure 6.17) is probably Eyre Formation and is indicative of gravel stream deposition. Such relatively coarse alluvium may be indicative of the period of Tertiary uplift of the Olary Block and Barrier Ranges in central Australia ((Krieg et al, 1990; Alley, 1998). Of immediate regional significance would be similar Tertiary uplift and erosion of the Innamincka Dome (Callen and Bradford, 1992). Throughout the Lake Eyre basin the Eyre Formation is overlain with the Etadunna and Namba Formations exhibiting high clay content and indicating a Tertiary shallow freshwater environment. Weathered lacustrinefines o f this appearance are present at the base of the Wills Grave site and at "Aarpoo" Waterhole (Figure 6.8). Unconformably overlying these Tertiary clays is the Katipiri Formation that has been dated beyond 400 ka in places but is commonly 300 ka to 200 ka across extensive areas of the eastern Lake Eyre basin (Callen and Nanson, 1992; Nanson et al, 1991% Maroulis, 2000). Its undated but probable equivalent, the Eurinilla Formation (Krieg et al, 1990; Alley, 178 1998) has been identified in the Strzelecki Desert. Relatively old Katipiri Formation occurs widely across the study region near the base of the Wills Grave site (-250 ka; Eurinilla Formation?) (Figure 6.16 and Figure 6.17), beneath thefloodplain near Turra Dune (-230 ka; Figure 6.26), at "Aarpoo" Waterhole (-155 ka; Figure 6.8) and at Tilcha Waterhole (-55 ka-145 ka; Figure 6.12). It appears that from about 250 ka to 150 ka Cooper Creek catchment was probably wetter and certainly morefluvially active, with the river having a significantly greater ability to laterally migrate and transport a coarse bed-load. Above these oldest and coarsest Katipiri deposits, channel sands within very minor gravels were deposited on active point bars of meandering streams. These trough cross- stratified alluvial dune structures have been TL dated at about 120 ka to 97 ka at Tilcha Waterhole (Figure 6.12). Similar clean sands have been dated about 118 ka to 52 ka below Turra Dune (Figure 6.26 and Figure 6.27), 87 ka to 66 ka at Dog Bite Lake and Gidgealpa and Gidgealpa South (Figure 6.29 and Figure 6.30). The meandering, laterally migrating nature of these channels is evident in the surface expression of some of the channels, in a curved shape of their associated source-bordering dunes (e.g. Figure 6.7, Figure 6.14 and Figure 6.22), and in the stratigraphic evidence for lateral migration at sites such as Wills Grave (Figure 6.17). At most of these sites the channel sands are overlain with vertical-accretion overbank deposits that have been TL dated as old as 103 ka to 82 ka beneath Turra Dune (Figure 6.27), not dissimilar to the age of overbank mud dated at approximately 100 ka by Maroulis (2000) on the western side of the Cooperfloodplain near Durham Downs and Jackson in Queensland. Of course there are much younger overbankfines a s well, some being presently deposited. The youngest palaeochannel sediments that are evidence of lateral activity are located at Wills Grave very near the present Cooper channel. Here between 55 ka and 25 ka the Cooper has migrated more than 100 m into the Tilcha dune, forming an unconformity with material older than -250 ka beneath (Figure 6.17). At the same time as this bend was migrating, aeolian sands were being blown from it to form a source-bordering dune north of the river (the upper part of the Tilcha Waterhole section, Figure 6.12). This dune was presumably formed and also partially excavated by the northward shifting channel (Figure 6.14). The aeolian sands overlying the alluvium at Tilcha Waterhole are evidence of marked drying and dune formation between about 58 ka and 20 ka, but 179 under intermittent flow conditions when the seasonally active channel (Wills Grave) immediately adjacent to Tilcha section (Figure 6.14, Figure 6.15, Figure 6.16 and Figure 6.17) was a source of abundant fine sand from an active point bar. That the channel was completely dry during the periods of seasonal deflation is evidenced by the fact that sand must have crossed the channel from a southerly located point bar to a northerly located dune (Figure 6.14 and Figure 6.15). 7.2.3 Cullyamurra Waterhole Cullyamurra Waterhole on Cooper Creek is 7 km long, reaches the extraordinary maximum depth of 30 m and is a zone of marked channel confinement located within the Innamincka Dome (Figure 6.18). Whereas most of the Cooper floodplain is a low energy environment and was probably so even during periods of enhanced Pleistocene flow, confinement of the Cooper within the Innamincka Dome offered an opportunity for stream-power amplification of thefluvial record during those periods when the flow- regime changes were too subtle to be recorded in the unconfined reaches beyond the Dome. Interestingly, the lower sandy alluvium some 8 m below the surface and about 400 m from the present waterhole yielded a TL date of -62 ka, similar to several dates obtained from palaeochannels on the Cooper 'fan' well beyond the Dome (Scrubby Camp, North Dog Bite Lake and beneath Gidgealpa Dune). Clearly, this was a period of enhancedfluvial activity. The lack of significant sandy channel deposits on the Cooper 'fan' younger than about 60 ka suggests thatfluvial energy and alluvial reworking markedly declined from that time onwards. The gradual migration of the Cooper channel at Wills Grave enabled preservation of at least some of the alluvial record over this period of reduced activity, however, lateral activity effectively ceased just prior to the LGM leaving no record at Wills Grave after that. In a limited way, the post LGM record is partly preserved in the Cullyamurra section (Figure 6.20). While only the southern floodplain adjacent to the waterhole was described and sampled it appears from this evidence that a much larger channel operated through the Dome at about 62 ka, contracting but remaining large until about 28 ka. The stratigraphy and interpreted LGM and upper Holocene isochrons in Figure 6.20 suggest that contraction of the waterhole continued until the end of the LGM (-20 ka to 18 ka). The present relatively inactive Cooper system appears to have been in existence from about the LGM with some evidence in the form of uppermost floodplain sand bodies that the Early to Middle 180 Holocene (-10 ka to -6 ka) was somewhat more active than the Middle to Late Holocene (Auger Holes 1 and 3; Figure 6.20). Evidence for enhanced flows on Cooper Creek, sourced largely in northern Australia and recorded in the 'amplifier' of the Innamincka Dome at around the time of the LGM and in the Early Holocene, is additionally supported by the more detailed chronological and stratigraphic work of Nott and Price (1994, 1999) and Nott et al (1996) on waterfall plunge-pools in northern Australia. 7.2.4 Strzelecki Creek Palaeochannels At Mudlalee (Figure 6.31), about 85 km south of Innamincka and Cooper Creek, Strzelecki Creek was actively transporting coarse-grained channel sand southwards from about -170 ka to -160 ka, with the channel aggrading to deposit an upper sand body at -120 ka to -110 ka (assuming sample confusion to explain the age reversal in Auger Hole 4; Figure 6.33). These depositional periods broadly coincide with channel dates obtained at "Aarpoo" Waterhole, Tilcha Waterhole and the Turrafluvial succession , all on the Cooper 'fan', and with results from Maroulis (2000) who also reported enhanced flow conditions for the Cooper Creek floodplain identified from laterally active meandering sandy rivers during OI Stages 6 and 5. It appears that, within the errors associated with TL dating, flow may have bifurcated down Cooper and Strzelecki Creeks at this time. Palaeochannels visible beneath the aeolian dunes adjacent to Strzelecki Creek show meandering channels laterally migrate to form scrolls. Auger holes revealed fining upward sequences of coarse to fine sand overlain with overbank sandy muds that TL date beneath the adjacent aeolian dunes at -82 ka to -57 ka (Figure 6.35 and Figure 6.36), not dissimilar to the ages for overbank muds on the Cooper 'fan' and along the northwest branch (-103 ka to -67 ka). It is worth noting that coarse channel sands were still being deposited on the Cooper 'fan' and along the northwest branch (near Turra Dune, Gidgealpa, Scrubby Camp and Dog Bite Lake) from -67 ka to -52 ka and near the present channel of the Cooper (Wills Grave) from -55 ka to 25 ka. Only one small deposit of clean channel sand dating from OI Stage 3 was found in the stratigraphy of Strzelecki Creek (-41 ka at Merty Merty; Figure 6.38). It appears this channel remained active after the LGM depositing clean sand at -14 ka and -11 ka. This 181 location is the only evidence obtained in this study for Strzelecki Creek actively transporting channel sand after about 110 ka. 7.2.5 Aeolian Sites (Turra, Gidgealpa, Mudlalee and Innamincka Racetrack) The Innamincka region of South Australia supports the extensive Strzelecki Desert dunefield described by Wasson (1983a, 1986). In the vicinity of the Cooper 'fan' the dunes consist of well defined source-bordering transverse forms that appear to have been deposited flanking the northern banks of curvilinear palaeochannels meandering westward away from the apex of the 'fan' at the exit of the Innamincka Dome (Figure 6.7, Figure 6.22 and Figure 6.23). Linear dunes are derived from and were blown northwards from the transverse dunes in the manner described by Twidale (1972) and Wasson (1983a). In the base of a 12 m high source-bordering dune at Turra, sand with carbonate nodules present dated at 116± 17 ka. Interestingly, potentially the oldest aeolian date in this study was obtained from a sample 700 m north of this point in the base of a linear dune, however, the age of 156±46ka is not significantly different. Ignoring this oldest date with the large error, and comparing the basal age of the Turra source-bordering dune with the age of the lunette at Coongie Lakes, it appears there was a seasonal change at about 116 ka to 109 ka with the formation of source-bordering dunes and lunettes in the area. This phase was probably related to strongly seasonal river flow conditions coinciding with fluctuations in sand transport, strong unidirectional winds and sparse riparian vegetation. The source-bordering dune at Turra is located adjacent to the meandering palaeochannels dated between 250 ka to 118 ka. These sand dominated channels must have provided an ample supply of sediment under climatic conditions seasonally dry enough for wind to have blown sand from exposed river beds. Older source-bordering dunes have not been discovered in the Cooper Creek area near Innamincka. A logical interpretation is that climate was too wet, insufficiently seasonal and/or insufficiently windy to allow for their formation. Alternatively, the high-energy fluvial channel environment during and prior to OI Stage 5 may have reworked any earlier aeolian sediment. The possibility of there being older aeolian sand at Turra is intriguing and further research in the area may reveal older dunes associated with earlier palaeochannels. 182 A second stage of the source-bordering dune activity has been TL dated at Turra at -41 ka and another at -25 ka. Another source-bordering (Gidgealpa Dune) has been TL dated at -24 ka overlayingfloodplain sediment that TL dated at -67 ka. The absence of equivalent-age palaeochannels at -40 ka and -25 ka on the Cooper 'fan' and northwest branch could suggest that episodes of dune activity here after OI Stage 4 were due largely to reworking of existing aeolian sand rather than the formation of new source- bordering dunes. However, source-bordering dunes were forming further upstream on Cooper Creek as late as -45 ka (Maroulis, 2000), so conditions were probably suitable for their formation then in the Innamincka region as well, albeit that they have not been discovered in this study. Longitudinal dune building has been TL dated at numerous sites throughout the area including East Mudlalee (-12 ka to -10 ka), West Mudlalee (-14 ka to -3 ka), Turra (-9 ka to -4 ka), Innamincka Racetrack (-5 ka to -1 ka) and Coongie Lake (-16 ka to -9 ka). There appears to have been two stages of longitudinal dune building: 16 ka to 9 ka and 5 ka to 1 ka reflecting local aridity and windiness. Wasson (1982, 1983a,b) found that dunes in the Strzelecki desert area ranged in age between 23 ka and 13 ka. It appears from the results here that the linear dunes are a younger generation than the source-bordering dunes, although earlier phases of both types of dunes formed in OI Stage 5 and earlier could have been reworked by subsequent fluvial episodes across the Cooper 'fan'. Elsewhere in the central Australia there are significantly older linear dunes than those identified here (Nanson, et al, 1988, 1992a; Wasson and Donnelly, 1991), but not in such a vulnerable situation as those across the path of flow on the Cooper 'fan'. Clearly, as identified in Chapter 5 on sediment texture, this is an environment where the Late Quaternary has been characterised by widespread interaction between aeolian and fluvial processes and landforms. 7.3 COMPARATIVE CHRONOLOGIES The effect of climate change in central Australian is becoming better understood with a wider application of diverse dating techniques such as TL, OSL and AMS C applied to alluvial, aeolian and lacustrine sediments. As a consequence there are now relatively new Quaternary palaeoenvironmental chronological data obtained from within the Lake Eyre 183 basin by Magee etal (1995), Magee and Miller (1998), Croke et al. (1996, 1997, 1999), Nanson et al. (1998), and Maroulis (2000). Earlier TL and stratigraphic work from alluvial and aeolian deposits in the Channel Country of the Lake Eyre basin conducted by Nanson et al (1988, 1990, 1992a) concluded that the Middle to Late Quaternary was divided into alternating patterns of wet and dry phases over the past 300 ka (Figure 7.1). They found that OI Stages 7 to 5 were dominated byfluvial condition s resulting in the transportation and deposition of channel sands in high-energy large meandering rivers. Towards the end of OI Stage 5 (pluvial) these meandering sand-bed channels were then replaced by inset anastomosing and surficial braided channels transporting mud. This was a dry phase associated with dune building, becoming intense during the LGM, although some enhanced fluvial activity was recorded for OI Stage 3 (Figure 7.1). The clear implication from the work conducted by Nanson et al. (1988, 1990, 1992a; Figure 7.1) was that the interglacials and interstadials were relative wet 'pluvial' periods separated by glacials and stadials that were relatively dry. Maroulis (2000; Figure 7.1) broadly supported this interpretation. He showed Cooper Creek to have been a vast sand-transporting system from at least -750 ka, with younger TL dates indicating alluvial activity in OI Stages 8, 7 and 5, but also providing evidence of considerablefluvial activit y during the interstadial of OI Stage 6 and that of OI Stage 3 (Figure 7.1). As well as thesefluctuations he recognised a progressive drying trend with each of the last several glacial cycles apparently having progressively lessfluvial impact . The results from this study of Cooper Creek near Innamincka provide strong support for the concept of a drying trend from -250 ka (Figure 7.1). However, this study provides no evidence of clearly defined oscillations between wet and dry phases identified by Nanson et al. (1988, 1990, 1992a) and Maroulis (2000). Interestingly enough when combining TL dates from Nanson et al (1988, 1990, 1992a), Maroulis (2000) and from this thesis, the dates suggests no discrete periods of fluvial activity (Figure 7.2). However, switching flow in the Cooper 'fan' in the vicinity of the Innamincka Dome and Strzelecki Creek may not be a suitable location for obtaining evidence of temporal oscillatory trends in the record when the switching could be partly topographically controlled. 184 f 10 Fluvial Sands n=25 0 20 40 60 80 100 120 140 160 1 SO 200 220 240 260 280 300 J I rears (ka) A&oSian Sands TTR 18 0 20 40 60 80 100 120 140 160 180 200 220 240 260 2B0 300 r Years (tea) 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Years (ka) 8 o / >" Fluvial Muds n= 19 0 20 40 60 SO 100 120 140 160 180 200 220 240 260 230 300 I Years (ka) Aeolian Sands n=18 V 0 20 40 60 80 100 120 140 160 180 200 220 240 260 2&0 30G Years (ka) f 10 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Years (ka) Fluvial Muds n=5 a . g. e 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Years (ka) Aeolian Sands n=28 ,: JO 40 60 80 100 120 140 160 180 200 220 240 260 280 300 V Years (ka) Figure 7.1: Comparison of TL frequency histograms from this study with those of Maroulis (2000) and Nanson et al. (1988, 1990, 1992a) classified according to depositional environments. . 185 20 40 60 80 100 120 140 160 183 200 220 240 260 Years (ka) Fluvial Muds n=24 T3 3 O UMJU 20 40 80 100 120 140 160 180 200 220 240 260 280 300 Years (ka) Aeolian Sands n=64 12 •fi 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Years (ka) Figure 7.2: Combined TL frequency histograms from this study, Maroulis (2000) and Nanson et al. (1988, 1990, 1992a) classified according to depositional environments. 7.3.1 Comparative Palaeoenvironmental Conditions within the Lake Eyre Basin 7.3.1.1 OI Stage 5 (130 ka to 74 ka?) At Williams Point at Madigan's Gulf on Lake Eyre, a lacustral phase lasting from about 130 ka to 90 ka was identified by Magee et al. (1995) as probably associated with the fluvial Katipiri Formation in the Channel Country (Nanson et al, 1992a). OI Stage 5 sediments reveal pronounced fluvial activity along the Cooper floodplain peaking at about 110 ka to 90 ka (Nanson, et al, 1992a; Maroulis, 2000). During this wet phase Cooper Creek near Iimarnincka was actively transporting bed-load andfiner channe l sands, the latter supplying the formation of source-bordering dunes and lunettes. Magee et al. (1995) have argued that the lake wasfrill to about 10 m AHD in early OI Stage 5 (130 ka to 90 ka) and dropped to about 5 m AHD by late OI Stage 5 (90 ka to 75 ka) with the lake briefly dry between these two periods. There is evidence of pedogensis in the lacustrine units prior to 70 ka followed by another lesser period of lacustrine beach formation (about -3 m to -4 m AHD) at -70 ka to 60 ka. They argue for dune building, deflation of the lakefloor and playa formation occurring between about 60 ka and 50 ka, 186 but suggest a possible lacustral phase between about 50 ka and 25 ka. Their work suggests the period between 25 ka to 10 ka was particularly arid with groundwater- controlled deflation producing the present playa morphology. This was followed by a very shallow phase over the present playafloor from about 10 ka to 4 ka. Nanson et al. (1998) dated beach ridges marginal to Lakes Eyre, Frome, Callabonna and Blanche and found that during OI Stage 5 a laterally disjunct series of-10 m AHD beach ridges formed at Lake Eyre South. Their work suggested that Lake Eyrefilled durin g OI Stage 5 by flows down the Cooper and Diamantina systems, but also from water diverted from Cooper Creek down Strzelecki Creek and through a spillway they named the Warrawoocara Channel, connecting Lake Gregory to Lake Eyre (and hence also connecting equally low-lying Lakes Blanche, Callabonna and Frome with Lake Eyre) (Figure 1.2). Following publication of their 1998 results, alluvial sediments along the Warrawoocara Channel have been TL dated giving ages of 115±28 ka, 115±12 ka and 102+20 ka (Nanson, pers. comm., 2000). These coincide withfluvial sediments along Strzelecki Creek TL dated for this study and giving ages of 118+1.1 ka and 110+12 ka. While Magee et al. (1995) and Nanson et al (1998) disagree on whether there was pronounced pluvial and associatedfluvial activit y in very early OI Stage 5, there seems to be widespread agreement that mid to late OI Stage 5 wasfluvially activ e and marked by high lake levels (Nanson et al, 1992a; Magee et al, 1995; Croke et al, 1996; Maroulis, 2000; and this study), although with some debate as to how high. The Tilcha section (Figure 6.12) and alluvial TL dates from Coongie Lakes (Figure 6.3), Turra fluvial succession (Figure 6.26), thefloodplain beneath Turra Dune (Figure 6.27), East Dog Bite Lake (Figure 6.29) and Strzelecki Creek at Mudlalee (Figure 6.33) provide examples of mid to late OI Stage 5 high Coongie Lake levels and enhanced fluvial activity in the Innamincka region. 7.3.1.2 OI Stage 4 (74 ka to 60 ka) After Stage 5 the evidence from the Lake Eyre basin becomes more problematic. The early part of OI Stage 4 appears from Lake Eyre stratigraphy to be unclear. Magee et al. (1995) suggest fluctuating lake levels but a period of well-defined pedogenesis at Williams Point probably between 75 ka and 70 ka. There is the suggestion of fluvial activity in the Turra fluvial succession (-75 ka to 71 ka; Figure 6.26), however, there are 187 only two dates and the uncertainties around each date limit any interpretation other than it may have been, as Magee et al (1995) suggest, a period of fluctuating wet and dry conditions. For the latter part of OI Stage 4 Magee et al (1995) have suggested enhanced lacustrine activity with a low-level (-4 m to -3 m AHD) shell-rich beach forming at Williams Point between 70 ka and 60 ka. Nanson et al (1998) identified beach ridges adjacent to Lake Eyre (8 m to 9 m AHD) and Lake Frome (-18 m AHD) with clean sandy deposits dating at about 70 ka to 63 ka that on the basis of an absence of shell and grit they interpreted as probably aeolian. An alternative explanation is that these are clean sandy beach deposits, or the result of minor aeolian reworking coeval with beach-ridge formation (Nanson, pers. comm., 2001). That this was a wet period with enhanced fluvial and lacustrine activity on the Lake Eyre basin is supported by results of palaeochannel activity (the Mt Howitt site dating at -63 ka to -60 ka in the middle reaches of the Cooper Creek) (Maroulis, 2000) and from evidence of fluvial activity in this study from Scrubby Camp (-66 ka; Figure 6.8), Cullyamurra Waterhole (-63 ka; Figure 6.20), North Dog Bite Lake (-66 ka; Figure 6.29) and beneath Gidgealpa Dune (-67 ka; Figure 6.30). All in all, the period from about 67 ka to 60 ka does appear to have had enhanced runoff. 7.3.1.3 OI Stage 3 (60 ka to 25 ka?) Very few channel sands away from the present river on the Cooper 'fan' date after -60 ka, a single exception being an uppermost sandy palaeochannel date of-52 ka in the Turrafluvial successio n (Figure 6.26). This suggests that fluvial energy and alluvial reworking markedly declined on the distal parts of the 'fan' from that time onwards. However, from other evidence it appears thatfluvial an d pluvial conditions did continue in central Australia after -60 ka. At Lake Amadeus southwest of Alice Springs, an episode interpreted as reflecting enhanced monsoonal conditions dated at approximately 60 ka to 45 ka (OI Stage 3; Chen et al, 1990). Nanson et al (1998) and Gardner et al. (1987) have provided a convincing set of five TL dates from elevated ridges at Lakes Frome and Eyre from about 55 ka to 39 ka, indicating high lake stands there. At Tilcha, what are almost certainly source-bordering dune sands were being deposited from what therefore must have been a seasonally active channel to about 55 ka (Figure 6.12), and possibly as late as 30 ka to 25 ka. While arguing for a general drying trend on Cooper Creek since before OI Stage 5, Maroulis (2000) recognised two substantial sandy 188 palaeochannels operating in OI Stage 3 and dating at 48 ka to 42 ka, one being at the western end of the Shire Road and the other at Chookoo, the later supplying substantial source-bordering dune sand at about 47 ka to 44 ka. Interestingly, there is some evidence for coarse sand deposition at Merty Merty on Strzelecki Creek at about 41 ka (Figure 6.38). Although largely confined to a situation proximal to the present channel, Cooper Creek apparently had sufficient energy to laterally migrate into its source- bordering dune at Wills Grave opposite Tilcha in the period from about 55 ka to about 23 ka (Figure 6.16 and Figure 6.17). There is no doubt that at times during OI Stage 3, particularly early in OI Stage 3, there would have been substantial channel flows down Cooper Creek but, as indicated by the presence of adjacent source-bordering dunes, they were probably strongly seasonal events. It seems possible that Lake Eyre responded by filling to at least the 5 m AHD level at times during early to mid OI Stage 3, as recognised from beachridges reporte d by Nanson et al. (1998). Overall, the record of Cooper Creek in the Innamincka region during OI Stage 3 was for drier conditions compared to OI Stage 5, with flow activity contracting to locations proximal to the present river after about 60 ka to 55 ka. Indeed, at Wills Grave the Cooper channel was only able to shift laterally at about 4 mm per year after about 55 ka. 7.3.1.4 OI Stages 2 and 1 (24 ka to 11 ka and 10 ka to 0 ka) Relatively confined flow conditions within the Innamincka Dome have amplified the otherwise declining alluvial signal of Cooper Creek in the latter part of the last full glacial cycle. Evidence of channel migration and meander-bend deposition at Wills Grave (Figure 6.17) suggests that Cooper Creek lacked sufficient erosional energy to migrate into its cut-bank at the onset of the LGM (24 ka). However, within the Dome there appears to have been sufficient energy to maintain a much larger channel cross-section at Cullyamurra Waterhole until about 20 ka to 18 ka (Figure 6.20). After then, only sandy alluvium from the Early to Middle Holocene is preserved, and then only proximal to the waterhole and in what appears to be a southern anabranch. At Mt Howitt, further upstream on Cooper Creek (QLD), a Late Pleistocene palaeochannel infilled with mud in the Holocene (Maroulis, 2000). Similar to the process at Cullyamurra Waterhole, Maroulis (2000) found that Cooper Creek at the western end of the Shire Road contracted from a very much larger sandy channel in the Early Holocene to its present 189 mud-confined form. It appears that Cooper Creek ceased transporting any significant sand load since the Middle Holocene when it became a low-energy mud dominated anastomosing system. 7.3.1.5 Dune Activity Satellite imagery of the Innamincka region (Figure 6.23 and Figure 6.24) shows the Strzelecki Desert on the Cooper 'fan' to consist of irregularly shaped but roughly east- west aligned transverse dunes. These were source-bordering, receiving their sand from palaeochannels of Cooper Creek similarly aligned. From these transverse dunes younger longitudinal dunes have been blown northwards. Source-bordering dunes require both significant flows to provide a supply of sand and sufficiently seasonal conditions to allow deflation from the channel. TL dating suggests the transverse source-bordering dunes were formed between about 115 ka and about 40 ka at Turra, and at -55 ka and even as late as about 30 ka to 25 ka at Tilcha. However, the latter period at Tilcha could have simply been one of aeolian reworking, for the channel here was laterally inactive and therefore probably relatively sediment-limited at that time. Source-bordering dunes are known to have formed further upstream on Cooper Creek from about 87 ka at Durham Downs (QLD) to about 47 ka to 44 ka at Chookoo (Maroulis, 2000). Subsequent aeolian activity was probably largely in the form of the reworking of existing dune deposits, as there were no substantial sandy channels operating as sources for new dunes (Maroulis, 2000). The northerly-aligned linear dunes in the Innamincka region appear to have been derived from sand supplied in two stages from the previously formed transverse dunes; -16 ka to -10 ka, and -5 ka to -1 ka. These two periods bracket the Early Holocene period of fluvial activity at Cullyamurra Waterhole. Both stages probably reflected periods of local and associated windiness. Wasson (1982, 1983a,b) found that dunes in the Strzelecki desert area clustered in age at about 18 ka to 16 ka coinciding with the LGM and 3 ka to 2ka. As identified from sediment texture analyses in Chapter 5, the Cooper 'fan' is an environment where the Late Quaternary has been characterised by widespread interaction between aeolian andfluvial processes . Nanson et al (1992b, 1995) have identified dunes of similar age to those near Innamincka in the Simpson Desert at 190 Birdsville (100 ka to Early Holocene) and along the Finke River near the township of Finke (110 ka to 4 ka). The period between 23 ka to 15 ka also saw the construction of gypsum lunettes and islands within Lake Frome and longitudinal dunes formation in the Strzelecki Desert (Wasson, 1983a, 1986; Wasson and Donnelly, 1991). English et al. (2001) have identified dune formation starting in the Lake Lewis basin northwest of Alice Springs on the edge of the Lake Eyre basin prior to 90 ka and peaking at about 23 ka to 21 ka. Elsewhere in the Lake Eyre basin dunes significantly older than those identified here have been described. These include those of 240 ka to 220 ka in age in the Simpson Desert (Gardner, et al, 1987) and one of-275 ka in age at Diamantina Lakes near the Diamantina River (Nanson et al, 1988, 1992a). However, such old dunes are not located in such a vulnerable situation as that across the path of river-flow on the Cooper 'fan'. 7.3.2 Comparative Palaeoenvironmental Conditions with Tropical Northern Australia The tropical northern Australian lakes described briefly in Chapter 2 were most probably monsoon fed, recording an increase in runoff and lake levels during OI Stage 7. Bowler et al. (1998, 2001) have described lacustrine phases in Lakes Woods (NT) and Gregory (WA). They identify broadly synchronous wet phases with each of the OI Stages 9, 7 and 5. Intervening dry periods saw the development offields o f longitudinal dunes initiated well before 200 ka. Interestingly, Bowler et al (1998) identified a dry period at Lake Woods between 96 ka and 60 ka but this same period represented a wet phase in the Innamincka area. Lake Woods then returned to lacustral conditions around 60 ka to 30 ka which coincides with fluvial activity still operating along the Innamincka region of Cooper Creek, and to associated source-bordering dune formation. By 30 ka Lake Woods became drier, linked with declining fluvial activity and enhanced source- bordering dune activity in the Innamincka area. As proposed by Nanson et al. (1992a, 1993) and more recently proposed by Bowler et al (1998, 2001), progressively declining moisture availability and contracting lacustrine interglacial conditions prevailed in the monsoon north of Australia with each successive glacial cycle over the past 300 ka. These results coincide with the Cooper Creek record near Innamincka where there has certainly been a contraction offluvial activit y since OI 191 Stage 7 and possibly earlier. In this study coarse bed-load sands and gravel lag deposits identified in palaeochannels form part of an extensive system of river channels in the Innamincka region during OI Stages 6 and 5, with very little activity in the Holocene 'interglacial'. In the Gulf of Carpentaria, alluvial deposits from the Gilbert River (Nanson et al, 1991) indicate enhancedfluvial activity during OI Stages 5, 3 and early Stage 1, similar to the results obtained in this study. Evidence of elevated monsoonal activity in northern Australia during OI Stages 5 and 3 is further supported from palynological evidence from Lynche's Crater where Kershaw (1983) and Hiscock and Kershaw (1992) found an increase in rainforest counts at these times. Interestingly, evidence for enhanced flows recorded in the 'amplifier' of the Innamincka Dome at around the time of the LGM and in the Early Holocene is supported by the detailed work of Nott and Price (1994, 1999) and Nott et al. (1996) on waterfall plunge- pools in northern Australia. They provide convincing evidence that northern Australia was receiving enhanced rainfall possibly in the form of severe storms at 30 ka to 18 ka and 10 ka to 5 ka, similar to the periods when Cullyamurra Waterhole was operating as a much larger channel. The increase in rainfall during this time is believed by Nott et al (1996) to be associated with northwest monsoon, but the periods identified by them are not obtained from the analyses of palaeo-shoreline ridges at Lake Woods, an area presumably influenced by the same monsoonal system. Furthermore, the Innamincka region of Cooper Creek saw the formation of longitudinal dunes from source-bordering dunes at -16 ka. There are some unresolved issues that await further research. The Gilbert River in the Gulf of Carpentaria provides evidence of declining wet conditions until 10 ka to 5 ka when again northern Australia became wetter (Nanson et al, 1991). This coincides with Shulmeister (1992, 1999) and Shulemister and Lees (1995) work on Holocene terrestrial pollen record from tropical northern Australia which suggests increased precipitation in the Early Holocene (-10 ka) with an effective precipitation maximum occurring at about 5 ka to 4 ka and a decline thereafter. Similar results during this period have additionally been obtained from Kershaw (1983) on the Atherton Tablelands in northeast Queensland. Additionally, Wyrwoll and Miller (2001) provide evidence of an even earlier active summer monsoon in northwestern Australia at around 14 ka compared with the wider regional evidence over northern Australia for the Early Holocene, and a decrease in monsoonal activity during the Late Holocene. The 192 Early to Mid Holocene period of enhanced moisture correlates with fluvial activity through the Innamincka Dome at Cullyamurra Waterhole and Strzelecki Creek. 7.4 CONCLUSION Cooper Creek is one of three major ephemeral river systems on the eastern side of the 1.3Ma km Lake Eyre drainage basin. Passing through the study area near Innamincka, the Creek drains nearly 237 000 km2 of semi-arid tropical and hot-arid Australia, and its associated chronostratigraphic sequences provide an opportunity to investigate and reconstruct the palaeoenvironmental Quaternary history for a very significant part of the continent's inland drainage. This Innamincka region is one of those relatively few locations where evidence of palaeoclimatic history from the Quaternary Period is preserved in at least three stratigraphic settings;fluvial, aeolia n and lacustrine. The significance of this location on Cooper Creek is further enhanced because, very unusually for such a largeriver system , the flow diverges into three distinct distributaries; north to Coongie Lakes, west towards Lake Eyre, and south down Strzelecki Creek into the Lake Frome basin. The only other significant Quaternary chronostratigraphy conducted in the Innamincka region was that by Wasson (1982, 1983a, 1986). This latest study represents an extension of that pioneer work, but undertaken in a period when luminescence dating has become more widely available. As demonstrated from similar data obtained further upstream on Cooper Creek there is evidence in the Innamincka region of enhancedfluvial activit y in the Middle Pleistocene at about 250 ka, but the record here is not detailed. Following this, there appears to have been a hiatus in fluvial activity until the middle of OI Stage 6 when clearly there was enhanced flow down both Cooper and Strzelecki Creeks. Another probable hiatus later in OI Stage 6 was then followed in OI Stage 5 by a widely recognised wet phase in the Lake Eyre basin. During mid to late OI Stage 5 both Cooper and Strzelecki Creeks were clearly actively meandering and transporting abundant sand, and there were high water levels at Coongie Lakes. There is evidence from late OI Stage 4 in this study to suggest a continuation of enhanced fluvial conditions on the Cooper 'fan' below the Innamincka Dome and within the Dome. However, the acquisition of just one TL sample on the Cooper 'fan' dating from OI Stage 3 suggests that, across the 'fan' as 193 whole, this may have been a time of reducedfluvial activity compared to OI Stages 5 and 4. Importantly though, evidence by Maroulis (2000) further upstream recognised the existence of substantial palaeochannels and source-bordering dunes at about 45 ka. Such flows must have passed through the Innamincka area, possibly in close proximity to the location of the existing channel as recorded by channel migration on the Cooper at Wills Grave. In OI Stages 5 and 3 source-bordering dunes were forming on the Cooper 'fan' probably due to marked flow seasonality. In OI Stage 3 there is some evidence for palaeochannel activity along Strzelecki Creek and clear evidence of slow lateral channel- migration along Cooper Creek in OI Stage 3 until the LGM. Source-bordering dunes dating at 40 ka to 25 ka do not correspond to older adjacent palaeochannels on Cooper Creek with a minimum age of -52 ka. This suggests substantial aeolian reworking in OI Stages 3 and 2. Cooper Creek beyond the Innamincka Dome ceased to transport any significant sand at around the LGM. With flow confinement and the resulting amplification in the Dome of what would otherwise be relatively low stream energy, alluvial stratigraphy there records evidence for a final period of somewhat enhancedfluvial activit y in the Early to Mid Holocene. However, it appears that Strzelecki Creek remainedfluvially active even after the LGM, transporting clean channel sands at 15 ka to 10 ka. Accumulated dune ages from this study indicate a pronounced period of aeolian activity from the LGM to the present, initially with the reworking of existing source-bordering dunes but then, particularly during the Holocene, with the extension northwards of derivative longitudinal dunes. There appears to have been two stages of longitudinal dune formation in the Strzelecki dunefield: 16 ka to 9 ka and 5 ka to 1 ka, probably signifying two periods of local dryness and windiness. Additionally, lacustrine lunettes were reworked from older lunettes in the Coongie Lakes region during the Holocene providing further evidence of the region as a whole becoming drier. Cooper Creek and Strzelecki Creek near Innamincka became a low-energy largely mud-transporting system from the Mid Holocene. The results of this study are in broad agreement with other work conducted along Cooper Creek and in Lake Eyre (Nanson et al, 1986, 1988, 1992a; Maroulis, 2000; Rust and Nanson, 1986) and Lake Eyre (Magee et al, 1995; Magee and Miller, 1998; 194 Magee, 1997), albeit with some regional differences. When compared with other terrestrial Australian Quaternary sites such as Lake Woods and Lake Gregory (Bowler et al, 1998, 2001), Magela Creek (Nanson et al, 1993), Gilbert River (Nanson et al, 1991), the Riverine Plain (Page et al, 1991; Page and Nanson, 1996) and northern Australia (Nott and Price, 1994, 1999; Nott et al, 1996; Shulmeister, 1992, 1999; Shulemister and Lees, 1995) there is a broadly consistent picture of Quaternary climatic events within Australia. The continent appears to have been much wetter in the Mid Quaternary and to have dried significantly but cyclically, over the last few glacials. Broadly speaking, within that trend the interglacials (OI Stages 7 and 5) and interstadials (mid OI Stage 6 and OI Stage 3) appear to have been wetter, and the intervening glacials and stadials, drier. However, early to mid OI Stage 4 stadial represents an anachronism, as does the entire Holocene 'interglacial' thus far! 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Initiation of the Australian summer monsoon 14 000 years ago. Quaternary International, 83-85, 119-128. APPENDICES APPENDIX 1 THERMOLUMINESCENCE DATA AND AGES 215 APPENDIX 2 MEAN GRAIN-SIZE ANALYSIS (14d> TO -2<|>), STANDARD DEVIATION (<|>), SKEWNESS (<|>), KURTOSIS ((j)) AND PERCENTAGE FINES (%) 220 APPENDIX 3 RECALCULATED GRAIN-SIZE BASED ON >4(|) FRACTIONS ONLY. MEAN GRAIN-SIZE ANALYSIS (4(f) TO -2<|)), STANDARD DEVIATION ((|>), SKEWNESS (<|>) AND KURTOSIS ((j)) 225 APPENDIX 4 BIVARIATE PLOTS OF FULL MEAN GRAIN-SIZE (ty) AND STANDARD DEVIATION ((|>) 230 APPENDIX 5 BIVARIATE PLOTS OF SAND FRACTION MEAN GRAIN- SIZE (<|>) AND STANDARD DEVIATION ((|>) 236 APPENDIX 6 TWO-TAILED T-TEST (P=0.05) ON THE FULL MEAN GRAIN- SIZE AND STANDARD DEVIATION 242 APPENDIX 7 TWO-TAILED T-TEST (P=0.05) ON THE SAND FRACTION MEAN GRAIN-SIZE AND STANDARD DEVIATION 254 APPENDIX 8 MUNSELL COLOUR INDICES 266 APPENDIX 9 PETROGRAPHIC AND CLUSTER ANALYSES 272 APPENDIX 10 DENDROGRAM 280 q LO oo CM 00 <5t . .•££ q CM oo co CM IO 00 co LO od oo d <0i: j;';;':': +1 +1 +1 +1 +1 +1 +l +1 +1 +1 +1 +1 +l +i 00 it st LO CM CO •st +i < 00 O q LO "st d OJ IO CM CD q LO "St LO •:::;:::-:ii.;;:;;;:;; 0M o 00 CM CM LO co O) y'::UiliSi;s;:i.;::: LO CD oo CD O oo oo oo CM 00 oo co co oo CN CM CM CM CM CM CM CM CM CM +1 +! +1 +i +1 +1 +1 +1 +1 +l +l +1 +1 +1 +1 00 00 "St °9 00 co o co -t CM OJ OJ OJ O CM o oo CM 00 It -«t 00 CM co LO LO o CM O oo OJ oo O co rt St OJ CO oq CO oo •St 00 OJ LO co st LO 1--. : d d d d d d d d d d d d d d +1 "2 i i^ +i +i +i +i +i +i +1 +i +i +i +1 +i CD +1 +i OJ OJ CM LO £ a> *- a r«- st OJ oo CM q •st oq 00 LO d "St •st CD OJ LO oo oo «o a « m CM 00 00 oo CM d LO CM CM CM 3 05 < — CD +J _ q q q q q q q q q q q q q q q 3: » xf •£ oo oo CO oo oo 00 oo oo co oo oo oo oo oo oo +i +i +l +i +i +i +i +1 +i +i +i +l +i +l +1 O 0:-3S::.:S CM cq oo 00 oo LO CM OJ CD st CM q q q CM CM CM LO d d 00 00 oo d d d o o O o o o O O O o q o o o o d d d d d d d d d d d d d d d -"LO ^* ^!^ go £o O o LOQ go ^o ^o go ;V go oo Conten t "st LO st CM CM •*t 00 CM go CM K LO (%byAES ) d d d d d d d d d d d d d o 8° «t dL O "St q> q st q CM oo CM LO 00 CO OJ CM CM d ::::«»: :£i;:::: CM CM CM LO st LO 00 "St CD d 1 • OJ oo p^ CM co 00 CO st OJ CM CM CM CM CM CM CM co m .§ "»'C CM CM CM CM CM CM CM CM co +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 OJ OJ 00 OJ LO LO 1 S • £ CO OJ OJ CM CM CM O <2 CM O co co O co o w o LO o CM LO OJ LO < S Q LO o CM CM oo oo OJ CO OJ st st 1^ o oo OJ LO 00 00 OJ OJ CO st Oi r-. st st r- jg ** a d d d d d d d d d d d d d +1 +i +1 +1 •g '6 I £ +i +1 +i +i +1 +1 +i +i +i +i +i +i oq LO st LO £ a> *- a? 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Ps 00 CO CO CO CD CO CO Ps CM CM CM CM CM CM CM Numbe r Specime n ,¥¥¥¥¥:¥:::•:¥: : APPENDIX 2 MEAN GRAIN-SIZE ANALYSIS (14<|> TO -1$), STANDARD DEVIATION ((J)), SKEWNESS ((J>), KURTOSIS ( Appendix 2.1 Lower Palaeochannel Sediments 1 Std. Dev Mean OjO Skewness Kurtosis % Fines Sample Number Depth (m) CUL1-2 5.00 0.92 1.07 -0.16 0.95 2.00 GSP1-1 0.60 0.97 2.22 0.54 2.62 8.00 MUP1-2 8.60 0.58 2.64 -0.27 1.20 9.00 MUP4-2 2.20 2.26 4.80 0.40 0.53 34.00 WIL1-1 4.20 0.86 1.09 -0.18 0.98 2.00 WIL2-4 7.50 0.94 0.64 -0.04 0.81 2.00 WIL2-5 9.00 _ 0.74 0.79 0.06 1.01 3.00 WIL2-6 10.00 0.82 1.06 0.19 1.15 3.00 Appendix 2.2 Upper Palaeochannel Sediments Std.Dev Sample Number Depth (m) Mean §| Skewness Kurtosfs % Fines ARP1-1 3.10 1.19 •H0.75i -0.15 0.98 3.00 CUL1-1 2.80 2.43 0.97 0.13 0.72 5.00 CUL1-3 5.50 1.48 1.36 -0.25 1.18 3.00 CUL1-4 6.60 2.89 0.67 0.03 0.93 6.00 CUL1-5 9.50 2.85 1.78 -0.04 1.84 12.00 CUL2-1 2.80 1.01 0.66 -0.12 0.84 2.00 CUL2-2 4.60 2.06 0.96 -0.30 1.24 3.00 CUL2-3 5.70 2.85 1.02 -0.42 1.22 7.00 CUL2-4 8.50 2.74 0.60 0.22 0.91 5.00 CUL2-5 11.00 1.65 0.67 -0.10 1.30 3.00 CUL3-1 2.70 2.43 0.97 0.13 0.72 5.00 CUL4-1 2.60 2.20 1.07 0.00 1.11 5.00 CUL4-2 5.60 3.22 0.58 -0.25 0.96 6.00 CUL4-3 8.50 1.41 1.45 -0.44 2.65 3.00 EDB1-1 4.00 1.93 1.14 0.48 3.83 7.00 EMD1-6 8.10 3.87 3.38 0.52 0.88 27.00 EMD1-7 8.20 4.00 3.85 0.54 0.74 30.00 GSP1-2 2.00 1.34 0.73 -0.24 1.35 3.00 GSP1-3 4.45 1.32 0.91 0.11 1.79 5.00 GSP1-4 6.45 3.25 1.64 0.42 3.85 16.00 GSP1-5 6.80 2.07 1.38 0.36 5.91 7.00 MARP1-1 3.00 1.50 1.71 0.15 4.36 6.00 MM1-1 3.85 4.64 3.24 0.76 1.42 28.00 MM1-2 4.45 4.00 3.47 0.64 1.24 28.00 Sample Number Depth (m) Mean 0)0 Std. Dev 4) Skewness Kurtosls ]:% Fines MM2-1 1.80 1.52 1.79 0.41 4.16 12.00 MM2-2 2.00 1.50 1.90 0.41 3.92 13.00 MUP1-1 3.00 1.12 0.96 -0.14 1.16 4.00 MUP1-3 8.90 2.56 0.99 0.17 2.84 6.00 MUP2-1 2.30 2.44 1.18 0.35 3.64 6.00 MUP2-2 6.00 2.46 3.29 0.55 1.63 18.00 MUP4-1 1.80 2.26 3.41 0.68 2.03 20.00 NDB1-1 3.70 2.94 0.54 0.20 1.42 5.00 NDB2-2 5.40 1.68 1.01 0.00 0.94 2.00 TIL2-13 16.44 2.45 1.76 0.62 4.67 15.00 TIL2-14 17.58 2.52 1.50 0.53 4.38 10.00 TIL2-15 18.66 2.25 1.17 0.53 3.82 6.00 TIL2-16 19.30 1.32 1.01 0.41 0.88 2.00 TIL2-17 19.56 1.81 1.03 -0.19 1.02 5.00 TIL2-18 21.10 2.01 0.48 0.12 1.16 3.00 TIL2-19 20.24 2.36 0.40 -0.05 1.19 2.00 TIL2-22 20.99 1.06 1.26 0.17 1.34 18.00 TIL2-23 20.44 1.58 0.67 0.33 1.34 14.00 TIL2-24 19.69 1.68 0.97 -0.01 1.21 20.00 TLD5-4 10.80 2.19 0.85 0.11 0.82 2.00 TLD6-4 8.70 4.63 3.03 0.64 2.27 25.00 TP1-2 2.25 1.25 2.25 0.48 2.58 13.00 TP2-1 2.50 5.01 2.84 0.69 0.64 35.00 TP2-2 3.35 4.67 3.20 0.55 0.62 38.00 TP3-2 5.80 5.43 2.79 0.72 0.60 45.00 TP3-3 6.40 5.97 2.72 0.22 0.62 52.00 TP3-4 7.70 4.73 3.59 0.46 0.63 38.00 TP3-5 8.00 1.21 2.15 0.19 2.72 6.00 TP3-6 8.90 1.22 1.17 -0.01 1.12 4.00 TP3-7 9.10 2.42 1.69 0.38 4.21 12.00 TP4-1 3.75 5.11 2.80 0.78 0.77 28.00 TP4-2 4.20 2.64 1.07 0.41 3.83 6.00 WIL1-2 5.60 1.61 0.67 -0.04 1.28 2.00 WIL2-1 2.70 1.57 0.83 -0.01 1.03 1.00 WIL2-2 3.50 1.06 0.84 -0.08 0.94 2.00 WIL2-3 5.50 1.38 0.71 -0.05 1.26 2.00 WIL2-7 11.60 1.42 1.22 -0.05 1.15 3.00 WIL3-1 3.00 1.44 0.70 -0.13 1.17 2.00 WIL3-2 5.70 1.07 0.69 -0.09 0.93 2.00 WIL3-3 8.80 1.03 0.67 -0.07 0.81 0.00 WIL3-4 12.00 1.64 1.00 -0.26 1.21 3.00 WIL3-5 15.00 1.62 1.02 -0.05 1.32 3.00 WIL3-7 20.50 1.84 1.08 0.02 1.17 7.00 WIL4-1 3.00 1.57 0.83 -0.01 1.03 1.00 WIL4-2 8.50 2.04 0.59 0.31 1.34 4.00 WIL4-3 11.50 2.16 0.68 -0.30 1.70 2.00 WIL4-4 17.00 3.17 0.56 -0.14 1.02 6.00 WMD2-6 8.70 4.77 2.56 0.78 2.18 26.00 Appendix 2.3 Overbank Sediments StdDev Sample Number Depth (m) Jvleani^::llllll : : Skewness Kuftbsls % Fines CUL3-2 6.70 2.84 0.68 0.01 0.95 25.00 EMD1-8 9.00 3.74 3.32 0.60 2.22 37.00 EMD1-9 9.40 5.10 3.16 0.42 0.64 41.00 GD1-4 7.00 2.67 1.63 0.53 3.88 32.00 NDB2-1 2.50 3.29 0.86 0.07 1.85 39.00 NDB2-3 7.70 2.41 1.20 -0.24 1.05 35.00 TIL2-11 13.33 5.36 3.35 0.44 0.57 51.00 TIL2-12 14.33 5.14 3.29 0.54 0.56 47.00 TLD4-7 9.80 5.05 3.14 0.44 0.56 49.00 TP1-1 1.70 ^ 3.83 3.03 0.64 3.05 21.00 TP3-1 3.70 2.85 1.30 0.50 5.15 27.00 TP4-3 4.80 6.78 2.42 0.06 0.70 88.00 TP4-4 5.40 7.83 1.90 -0.04 0.89 97.00 WIL3-6 17.20 2.20 1.25 -0.09 1.04 25.00 WMD2-7 10.00 4.36 3.20 0.49 1.90 24.00 Appendix 2.4 Source-Bordering Dune Sediments Std.Dev Sample Number Depth (m) Mean (<(>) Skewness KurtQsIs % Fines GD1-2 3.00 2.62 1.59 0.42 3.70 9.00 TIL2-1 3.58 2.70 1.44 0.43 2.28 2.00 TIL2-2 4.27 3.62 2.19 0.64 2.37 4.00 TIL2-3 5.65 2.52 1.61 0.58 3.02 2.00 TIL2-4 6.46 3.69 2.49 0.65 2.08 5.00 TIL2-5 7.41 3.77 2.57 0.66 1.96 22.00 TIL2-6 8.48 2.35 1.49 0.54 3.18 9.00 TIL2-6A 8.70 2.65 1.66 0.42 2.53 11.00 TIL2-7 9.32 2.82 1.47 0.44 2.54 11.00 TIL2-8 9.63 3.05 1.79 0.52 2.34 18.00 TIL2-9 11.37 3.69 2.38 0.69 2.13 18.00 TIL2-10 12.29 2.61 1.78 0.47 2.52 14.00 TLD1-1 2.70 2.34 0.75 0.14 1.01 3.00 TLD1-2 4.00 2.72 0.77 0.03 0.84 5.00 TLD1-3 5.70 2.54 0.75 0.04 0.96 3.00 TLD1-4 8.70 2.23 1.06 -0.04 1.01 3.00 Appendix 2.5 Diagenetically Altered Sediments Std.Dev Sample Number Deplhlpi) Mean ( CLD1-3 9.80 2.59 0.65 0.09 1.02 3.00 CLD1-4 10.60 2.79 0.75 0.01 0.88 6.00 EMD1-2 4.25 3.60 2.61 0.68 2.85 16.00 EMD1-3 6.90 2.31 2.51 0.36 1.56 16.00 EMD1-4 7.50 3.93 F 3.86 0.46 0.74 30.00 EMD1-5 7.75 4.97 3.34 0.42 0.64 48.00 IRT1-4 3.60 2.45 0.99 0.33 1.97 6.00 TLD2-3 4.70 2.56 1.77 0.48 2.43 11.00 TLD2-4 8.00 3.88 2.51 0.70 2.53 21.00 TLD3-2 8.20 2.62 0.87 -0.03 0.98 4.00 TLD3-3 10.00 2.42 0.74 -0.04 1.15 3.00 TLD4-2 5.20 4.12 2.80 0.65 2.31 20.00 TLD4-3 6.00 4.56 2.95 0.65 2.26 23.00 TLD4-4 6.90 1.66 1.88 0.31 2.38 8.00 TLD4-5 7.20 3.97 2.56 0.62 2.00 20.00 TLD5-1 5.00 2.64 0.65 0.07 1.00 3.00 TLD5-2 6.40 2.68 0.63 0.11 0.98 3.00 TLD5-3 8.85 2.55 0.79 0.05 0.98 4.00 TLD6-3 7.20 2.52 1.44 0.31 2.23 7.00 WMD2-2 2.80 2.59 1.59 0.35 2.26 8.00 WMD2-3 3.80 2.86 1.84 0.27 2.21 15.00 WMD2-4 6.00 3.65 2.92 0.55 2.09 18.00 WMD2-5 7.40 4.33 3.01 0.67 0.77 32.00 Appendix 2.6 Dune Surface Sediments Std. Dev Kurtosis % Fines Sample Number Depth (m) Mean (<)>) m Skewhess CLD1-1 1.00 2.49 0.55 0.10 1.03 2.00 CLD1-2 2.20 2.67 0.58 0.07 0.98 3.00 EMD1-1 1.00 2.43 1.21 0.41 2.80 7.00 IRT1-1 2.00 2.39 0.59 0.02 1.03 3.00 TLD2-1 1.00 2.66 1.51 0.42 2.24 10.00 TLD2-2 2.00 2.83 1.66 0.41 2.52 12.00 TLD6-1 1.10 2.12 1.01 0.32 2.55 5.00 TLD6-2 1.65 2.84 1.94 0.67 [ 3.57 18.00 TLD4-1 1.30 2.60 1.12 0.34 2.16 6.00 TLD3-1 1.20 2.21 0.65 0.12 1.04 2.00 WMD2-1 1.20 2.51 1.18 0.26 1.69 6.00 Appendix 2.7 Lunette Sediments Std.Dev Depth (m) Skewness % Fines Sample Number Mean(<{>) iimi:^ Kurtosis MAR1-2 3.00 4.43 2.89 0.62 0.90 28.00 MAR2-1 1.20 2.95 0.91 -0.37 1.30 0.00 MAR2-2 3.90 2.61 0.75 0.04 0.97 3.00 MAR2-3 4.20 2.57 0.80 0.01 0.97 3.00 MAR2-4 8.70 2.57 0.89 -0.02 0.94 5.00 MAR2-5 10.70 2.63 1.23 -0.36 3.13 3.00 225 APPENDIX 3 RECALCULATED GRAIN-SIZE BASED ON >4<|> FRACTIONS ONLY. MEAN GRAIN-SIZE ANALYSIS (44 TO -2<|>), STANDARD DEVIATION (<|>), SKEWNESS (<|>) AND KURTOSIS ((J>) Appendix 3.1 Lower Palaeochannel Sands Sample Number Depth (m) Mean #) Std,Dev{ Appendix 3.2 Upper Palaeochannel Sands Sample Number Depth (m) Mean (<(>)_ Std.Dev (cj)) Skewness Kurtosis ARP1-1 3.10 1.17 0.71 -0.20 0.90 CULM 2.80 2.40 0.95 0.15 0.73 CUL1-3 5.50 1.47 1.36 -0.26 1.17 CUL1-4 6.60 2.87 0.66 0.02 0.93 CUL1-5 9.50 2.67 1.13 -0.42 0.81 CUL2-1 2.80 1.01 0.66 -0.12 0.83 CUL2-2 4.60 2.05 0.95 -0.31 1.23 CUL2-3 5.70 2.80 1.01 -0.44 1.17 CUL2-4 8.50 2.71 0.57 0.19 0.91 CUL2-5 11.00 1.65 0.66 -0.10 1.30 CUL3-1 2.70 2.40 0.95 0.15 0.73 CUL4-1 2.60 2.16 1.04 -0.02 1.12 CUL4-2 5.60 3.21 0.58 -0.26 0.95 CUL4-3 8.50 1.40 1.44 -0.46 2.63 EDB1-1 4.00 1.87 0.43 0.11 1.11 EMD1-6 8.10 1.84 1.25 -0.20 0.95 EMD1-7 8.20 1.57 1.31 -0.15 1.01 GSP1-2 2.00 1.31 0.69 -0.29 1.24 GSP1-3 4.45 1.25 0.70 -0.10 1.22 GSP1-4 6.45 3.04 0.57 -0.20 1.22 GSP1-5 6.80 2.04 0.35 -0.07 0.89 MARP1-1 3.00 1.40 0.76 -0.42 1.35 MM1-1 3.85 2.45 0.69 0.21 1.01 MM1-2 4.45 1.81 1.15 0.25 0.95 MM2-1 1.80 1.27 0.69 -0.12 1.30 Sample Number Depth (m) Mean (<|>) Std.Dev( SampleNumber Depth (m) Mean ( Appendix 3.4 Source-Bordering Sands Sample Number Depth (m) Mean (<{>) Std.Dev ( Sample Number Depth (m) Mean (4>) Std.Dev (c|>) Skewness Kurtosis CLD 1-3 i 9.80 2.58 0.64 0.08 1.01 CLD 1-4 10.60 2.75 0.72 0.01 0.88 EMD 1-2 4.25 2.29 0.76 -0.03 1.14 EMD 1-3 6.90 1.70 1.25 0.05 0.70 EMD 1-4 7.50 1.54 1.43 0.10 0.75 EMD 1-5 7.75 2.29 1.03 -0.10 1.08 IRT 1-4 3.60 2.36 0.60 0.06 0.97 TLD 2-3 4.70 2.34 0.80 0.14 0.95 TLD 2-4 8.00 2.65 0.65 0.08 0.94 TLD 3-2 8.20 2.59 0.84 -0.04 0.99 TLD 3-3 10.00 2.42 0.74 -0.04 1.15 TLD 4-2 5.20 2.56 0.82 -0.05 0.96 TLD 4-3 6.00 2.74 0.80 -0.04 0.80 TLD 4-4 6.90 1.48 0.95 -0.06 0.89 TLD 4-5 7.20 2.46 0.84 -0.09 1.16 TLD 5-1 5.00 2.63 0.63 0.05 0.99 TLD 5-2 6.40 2.66 0.62 0.10 0.97 TLD 5-3 8.85 2.53 0.77 0.03 0.98 TLD 6-3 7.20 2.39 0.84 -0.03 1.11 WMD 2-2 2.80 2.46 0.81 0.01 0.87 WMD 2-3 3.80 2.59 0.89 -0.12 0.84 WMD 2-4 6.00 2.18 0.99 -0.22 1.02 WMD 2-5 7.40 2.39 0.76 -0.09 0.91 Appendix 3.6 Dune Surface Sands Sample Number Depth (m) Mean(<|>) Std.Dev (i?) Skewness Kurtosis CLD 1-1 1.00 2.49 0.54 0.10 1.03 CLD 1-2 2.20 2.66 0.57 0.06 1.00 EMD 1-1 1.00 2.33 0.57 0.08 0.99 IRT 1-1 2.00 2.36 0.56 -0.02 0.98 TLD 2-1 1.00 2.49 0.76 0.09 0.93 TLD 2-2 2.00 2.64 0.74 0.03 0.86 TLD 3-1 1.20 2.20 0.65 0.12 1.04 TLD 4-1 1.30 2.51 ^ 0.64 0.04 0.99 TLD 6-1 1.10 2.05 0.54 -0.03 1.05 TLD 6-2 1.65 [ 2.26 0.54 0.09 1.02 WMD 2-1 1.20 2.41 0.77 0.01 0.90 Appendix 3.7 Lunette Sands Sample Number Depth (m) Mean ( APPENDK 4 BIVARIATE PLOTS OF FULL MEAN GRAIN-SIZE (<|>) AND STANDARD DEVIATION (<|)) Appendix 4.1 Lower Palaeochannel Sediments -Mean -Standard Deviation 0.00 CUL1-2 GSP1-1 MUP1-2 MUP4-2 WIL1-1 WIL2-4 WIL2-5 WIL2-I Sample Number Appendix 4.2 Upper Palaeochannel Sediments -Mean -Standard Deviation > J n> a* a? yy J? ^ S~ */ y / O^ dr* d* o „•$< ryc ryc rry cry c rry rf # c& c-? Sample Number -Mean -Standard Deviation o^ <£ <^ J? J? «N* -Mean -Standard Deviation TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2-TLD5-TLD6-TP1-2TP2-1 TP2-2 13 14 15 16 17 18 19 22 23 24 4 4 Sample Number 232 -Mean -Standard Deviation TP3- TP3- TP3- TP3- TP3- TP3- TP4- TP4- WIL WIL WIL WIL WIL WIL WIL WIL WIL 2 3 4 5 6 7 12 1-22-1 2-2 2-3 2-7 3-1 3-2 3-3 3-4 Sample Number 8.00 6.00 7.50 5.50 7.00 -5.00 6.50 6.00 y 4.50 5.50 - 4.00 5.00 1 3.50 | 4.50 n > -Mean S 4.00 ai -Standard Deviation S • - 3.00 Q 3.50 9- 2.50 j§ in 3.00 2.00 2.50 2.00 ; • 1.50 1.50 1.00 1.00 0.50 0.50 0.00 0.00 WIL3-5 WIL3-7 WIL4-1 WIL4-2 WIL4-3 WIL4-4 WMD2-6 Sample Number Appendix 4.3 Overbank Sediments -Mean -Standard Deviation 0.00 Appendix 4.4 Source-Bordering Sediments -Mean -Standard Deviation -t I 1 1 1 1 H GD1- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TLD TLD TLD TLD 2 1 2 3 4 5 6 6A 7 8 9 10 1-1 1-2 1-3 1-4 Sample Number Appendix 4.5 Diagenetically Altered Sediments -Mean -Standard Deviation J&W&WM'MfM&S/SSf Sample Number Appendix 4.6 Dune Surface Sediments -Mean -Standard Deviation H 1 1 1 1- CLD1-1 CLD1-2 EMD1-1 IRT1-1 TLD2-1 TLD2-2 TLD6-1 TLD6-2 TLD4-1 TLD3-1 WMD2-1 Sample Number 235 Appendix 4.7 Lunette Sediments -Mean -Standard Deviation MAR1-2 MAR2-1 MAR2-2 MAR2-3 MAR2-4 MAR2-5 Sample Number 236 APPENDIX 5 BIVARIATE PLOTS OF SAND FRACTION MEAN GRAIN- SIZE (<|>) AND STANDARD DEVIATION (<|>) Appendix 5.1 Lower Palaeochannel Sands 6.00 -Mean -Standard Deviation H H CUL1-2 GSP1-1 MUP1-2 MUP4-2 WIL 1-1 WIL 2-4 WIL 2-5 WIL 2-6 Sample Number Appendix 5.2 Upper Palaeochannel Sands -Mean -Standard Deviation ARP1-CUL1- CULL CUL1- CUL1- CUL2- CUL2- CUL2- CUL2- CUL2- CUL3- CUL4- CUL4- CUL4- 11345123451123 Sample Number 8.00 6.00 7.50 - - • - 5.50 7.00 6.50 : - • - 5.00 6.00:- 4.50 5.50 \ - 4.00 5.00 4.50 '• - > -Mean 4.00 - - oi - • 3.00 Q -Standard Deviation 3.50 - 2.50 3.00 2.50 2.00 f 1.50 1.00 0.50 0.00 oN C-f* rtK o* # # Mean Standard Deviation TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2- TIL2-TLD5-TLD6-TP1-2TP2-1 TP2-2 13 14 15 16 17 18 19 22 23 24 4 4 Sample Number 8.00 6.00 7.50 5.50 7.00 5.00 6.50 6.00 4.50 5.50 4.00 5.00 4.50 -Mean 4.00 -Standard Deviation 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 1 1 1 1 1 1 1 1 1 -+- 0.00 TP3- TP3- TP3- TP3- TP3- TP3- TP4- TP4- WIL WIL WIL WIL WIL WIL WIL WIL WIL 2 3 4 5 6 7 1 2 1-2 2-12-2 2-3 2-7 3-1 3-2 3-3 3-4 Sample Number 6.00 -Mean -Standard Deviation WIL4-4 WMD2-6 WIL3-5 WIL3-7 WIL4-1 WIL4-2 WIL4-3 Sample Number Appendix 5.3 Overbank Sands -Mean -Standard Deviation VVV f * * JJ/ Sample Number Appendix 5.4 Source-Bordering Sands 8.00 6.00 7.50 5.50 7.00 5.00 6.50 6.00 4.50 5.50 -4.00 5.00 -3.50 J 4.50 > -Mean : 4.00 01 -3.00 ° -Standard Deviation 3.50 •g m 2.50 3.00 T3 2.00 2.50 2.00 - 1.50 1.50 1.00 1.00 0.50 0.50 1 0.00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 0.00 GD TIL2-TIL2-TIL2-TIL2-TIL2-TIL2-TIL2-TIL2-TIL2-TIL2-TIL2- TLD TLD TLD TLD 1-2 1 10 2 3 4 5 6 6a 7 8 9 1-1 1-2 1-3 1-4 Sample Number Appendix 5.5 Diagentically Altered Sands 8.00 6.00 7.50 5.50 7.00 5.00 6.50 6.00 4.50 5.50 4.00 5.00 3.50 -Mean -Standard Deviation Sample Number Appendix 5.6 Dune Surface Sands -Mean -Standard Deviation CLD 1-1 CLD1-2EMD1-1 IRT 1-1 TLD 2-1 TLD 2-2 TLD 3-1 TLD 4-1 TLD 6-1 TLD 6-2 WMD 2- 1 Sample Number 241 Appendix 5.7 Lunette Sands 6.00 -5.50 -5.00 -4.50 ^4.00 c -3.50 o 15 a Mean -3.00 > 01 —•—Standard Deviation D -2.50 •a m •o -2.00 c s -1.50 in 1.00 0.50 0.00 MAR 1-2 MAR 2-1 MAR 2-2 MAR 2-3 MAR 2-4 MAR 2-5 Sample Number 242 APPENDIX 6 TWO-TAILED T-TEST (P=0.05) ON THE FULL MEAN GRAIN-SIZE AND STANDARD DEVIATION Appendix 6.1 Mean Grain-Size t-Test: Assuming Unequal Variances \^.. MeanGrain-Size< t-Test Lower Palaeochannel (mean) Diagenticatty Altered (mean) Mean 1.01 3.14 Variance 0.27 0.75 Observations 8.00 23.00 Hypothesized Mean Difference 0.00 df 21.00 tStat -8.26 P(T<=t) one-tail 0.00 t Critical one-tail 1.72 P(T<=t) two-tail 0.00 t Critical two-tail 2.08 P<0.05 reject Ho Overbank (mean) Diagenetically Atered (mean) Mean 4.23 3.14 Variance 2.71 0.75 Observations 15.00 23.00 Hypothesized Mean Difference 0.00 df 19.00 tStat 2.35 P(T<=t) one-tail 0.01 t Critical one-tail 1.73 P(T<=t) two-tail 0.03 t Critical two-tail 2.09 P<0.05 reject Ho Lower Palaeochannel (mean) Overbank (mean) Mean 1.01 4.23 Variance 0.27 2.71 Observations 8.00 15.00 Hypothesized Mean Difference 0.00 df 18.00 tStat -6.95 P(T<=t) one-tail 0.00 t Critical one-tail 1.73 P(T<=t) two-tail 0.00 t Critical two-tail 2.10 P<0.05 reject Ho Mean Gra'ai'SiZe t-Test ii Overbaftkftman) : Lunette (mean) Mean 4.23 2.96 Variance 2.71 0.54 Observations 15.00 6.00 Hypothesized Mean Difference 0.00 df 19.00 tStat 2.44 P(T<=t) one-tail 0.01 t Critical one-tail 1.73 P(T<=t) two-tail 0.02 t Critical two-tail 2.09 P<0.05 reject Ho Dune Surface (mean} Diagenetically Altered (mean) Mean 2.52 3.14 Variance 0.05 0.75 Observations 11.00 23.00 Hypothesized Mean Difference 0.00 df 28.00 tStat -3.18 P(T<=t) one-tail 0.00 t Critical one-tail 1.70 P(T<=t) two-tail 0.00 t Critical two-tail 2.05 P<0.05 reject Ho Dune Surface (mean) Source-Bordering (mean) Mean 2.52 2.87 Variance 0.05 0.28 Observations 11.00 16.00 Hypothesized Mean Difference 0.00 df 22.00 tStat -2.32 P(T<=t) one-tail 0.01 t Critical one-tail 1.72 P(T<=t) two-tail 0.03 t Critical two-tail 2.07 P<0.05 reject Ho DuneSurface (mean) Lunette (mean) Mean 2.52 2.96 Variance 0.05 0.54 Observations 11.00 6.00 Hypothesized Mean Difference 0.00 df 6.00 tStat -1.42 P(T<=t) one-tail 0.10 t Critical one-tail 1.94 P(T<=t) two-tail 0.21 t Critical two-tail 2.45 P>0.05 accept Ho Mean Grain-Size t-Test Diagenetically Altered (mean) Source-Bordering (mean) Mean 3.14 2.87 Variance 0.75 0.28 Observations 23.00 16.00 Hypothesized Mean Difference 0.00 df 36.00 tStat 1.21 P(T<=t) one-tail 0.12 t Critical one-tail 1.69 P(T<=t) two-tail 0.23 t Critical two-tail 2.03 ,P>0.05 accept Ho Diagenetically Altered (mean) Lunette (mean) Mean 3.14 2.96 Variance 0.75 0.54 Observations 23.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 tStat 0.52 P(T<=t) one-tail 0.31 t Critical one-tail 1.83 P(T<=t) two-tail 0.62 t Critical two-tail 2.26 P>0.05 accept Ho Source-Bordenng (mean) Lunette (mean) Mean 2.87 2.96 Variance 0.28 0.54 Observations 16.00 6.00 Hypothesized Mean Difference 0.00 df 7.00 tStat -0.28 P(T<=t) one-tail 0.40 t Critical one-tail 1.89 P(T<=t) two-tail 0.79 t Critical two-tail 2.36 P>0.05 accept Ho Lower palaeochannel (mean) Dune Surface (mean) Mean 1.01 2.52 Variance 0.27 0.05 Observations 8.00 11.00 Hypothesized Mean Difference 0.00 df 9.00 tStat -7.70 P(T<=t) one-tail 0.00 t Critical one-tail 1.83 P(T<=t) two-tail 0.00 t Critical two-tail 2.26 P<0.05 reject Ho Mean\ Grain-SizeUTest J Lower Palaeochannel (mean) Lunette (mean) Mean 1.01 2.96 Variance 0.27 0.54 Observations 8.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 tStat -5.55 P(T<=t) one-tail 0.00 t Critical one-tail 1.83 P(T<=t) two-tail 0.00 t Critical two-tail 2.26 P<0.05 reject Ho Lower Palaeochannel (mean) Upper Palaeochannel (mean) Mean 1.01 2.39 Variance 0.27 1.50 Observations 8.00 72.00 Hypothesized Mean Difference 0.00 df 18.00 tStat -5.89 P(T<=t) one-tail 0.00 t Critical one-tail 1.73 P(T<=t) two-tail 0.00 t Critical two-tail 2.10 PO.05 reject Ho Upper Palaeochannel (mean) Overbank(mean) Mean 2.39 4.23 Variance 1.50 2.71 Observations 72.00 15.00 Hypothesized Mean Difference 0.00 df 17.00 tStat -4.11 P(T<=t) one-tail 0.00 t Critical one-tail 1.74 P(T<=t) two-tail 0.00 t Critical two-tail 2.11 P<0.05 reject Ho Upper Palaeochannel (mean) Dune Surface (mean) Mean 2.39 2.52 Variance 1.50 0.05 Observations 72.00 11.00 Hypothesized Mean Difference 0.00 df 78.00 t Stat -0.86 P(T<=t) one-tail 0.20 t Critical one-tail 1.66 P(T<=t) two-tail 0.39 t Critical two-tail 1.99 P>0.05 accept Ho Mean Gram-Size t- Test Upper Palaeochannel (mean) Diagenetically Altered (mean) Mean 2.39 3.14 Variance 1.50 0.75 Observations 72.00 23.00 Hypothesized Mean Difference 0.00 df 52.00 tStat -3.26 P(T<=t) one-tail 0.00 t Critical one-tail 1.67 P(T<=t) two-tail 0.00 t Critical two-tail 2.01 P<0.05 reject Ho Upper Palaeochannel (mean) Lunette (mean) Mean 2.39 2.96 Variance 1.50 0.54 Observations 72.00 Hypothesized Mean Difference 0.00 df 8.00 tStat -1.73 P(T<:=t) one-tail 0.06 t Critical one-tail 1.86 P(T<=t) two-tail 0.12 t Critical two-tail 2.31 P>0.05 accept Ho I Upper Palaeochannel (mean) Source-Bordering (mean) Mean 2.39 2.87 Variance 1.50 0.28 Observations 72.00 16.00 Hypothesized Mean Difference 0.00 df 56.00 tStat -2.47 P(T<=t) one-tail 0.01 t Critical one-tail 1.67 P(T<=t) two-tail 0.02 t Critical two-tail 2.00 | P<0.05 reject Ho Lower Palaeochannel (mean) Source-Bordering (mean) Mean 1.01 2.87 Variance 0.27 0.28 Observations 8.00 16.00 Hypothesized Mean Difference 0.00 df 14.00 tStat -8.22 P(T<=t) one-tail 0.00 t Critical one-tail 1.76 P(T<=t) two-tail 0.00 t Critical two-tail 2.14 P<0.05 reject Ho Mean Grain-Sket-Test Overbank (mean) Dune Surface (mean) Mean 4.23 2.52 Variance 2.71 0.05 Observations 15.00 11.00 Hypothesized Mean Difference 0.00 df 15.00 tStat 3.96 P(T<=t) one-tail 0.00 t Critical one-tail 1.75 P(T<=t) two-tail 0.00 t Critical two-tail 2.13 P<0.05 reject Ho Overbank (mean) Source-Bordering (mean) Mean 4.23 2.87 Variance 2.71 0.28 Observations 15.00 16.00 Hypothesized Mean Difference 0.00 df 17.00 tStat 3.05 P(T<=t) one-tail 0.00 t Critical one-tail 1.74 P(T<=t) two-tail 0.01 t Critical two-tail 2.11 P<0.05 reject Ho Appendix 6.2 Standard Deviation t-Test: Assuming Unequal Variances Standard Deviation t- Test Overbank (st.dev) Dune Surface (stdev) Mean 2.25 1.09 Variance 1.03 0.22 Observations 15.00 11.00 Hypothesized Mean Difference 0.00 Df 21.00 tStat 3.87 P(T<=t) one-tail 0.00 t Critical one-tail 1.72 P(T<=t) two-tail 0.00 t Critical two-tail 2.08 P<0.05 reject Ho Overbank {stdev) Dfageneticaily Altered (stdev) Mean 2.25 1.90 Variance 1.03 1.03 Observations 15.00 23.00 Hypothesized Mean Difference 0.00 df 30.00 tStat 1.04 P(T<=t) one-tail 0.15 t Critical one-tail 1.70 P(T<=t) two-tail 0.31 t Critical two-tail 2.04 P>0.05 accept Ho Overbank(stdev) Source-Bordering (Stjdev) Mean 2.25 1.61 Variance 1.03 0.35 Observations 15.00 16.00 Hypothesized Mean Difference 0.00 df 22.00 tStat 2.11 P(T<=t) one-tail 0.02 t Critical one-tail 1.72 P(T<=t) two-tail 0.05 t Critical two-tail 2.07 P<0.05 reject Ho Overbank (stdev) Lunette (st.dey) Mean 2.25 1.25 Variance 1.03 0.68 Observations 15.00 6.00 Hypothesized Mean Difference 0.00 df 11.00 tStat 2.35 P(T<=t) one-tail 0.02 t Critical one-tail 1.80 P(T<=t) two-tail 0.04 t Critical two-tail 2.20 P<0.05 reject Ho Standard Deviation i-Test Dune Surface (st. dev) DiageneticaSy Altered (stdev) Mean 1.09 1.90 Variance 0.22 1.03 Observations 11.00 23.00 Hypothesized Mean Difference 0.00 df 32.00 tStat -3.17 P(T<=t) one-tail 0.00 | t Critical one-tail 1.69 P(T<=t) two-tail 0.00 ft Critical two-tail 2.04 P<0.05 reject Ho | Dune Surface (stdev) Source^B&rdeifRg (st.dev) Mean 1.09 1.61 Variance 0.22 0.35 | Observations 11.00 16.00 Hypothesized Mean Difference 0.00 df 24.00 tStat -2.53 P(T<=t) one-tail 0.01 t Critical one-tail 1.71 P(T<=t) two-tail 0.02 t Critical two-tail 2.06 j P<0.05 reject Ho Dune Surface (st.dev) Lunette (stdev) Mean 1.09 1.25 Variance 0.22 0.68 Observations 11.00 6.00 Hypothesized Mean Difference 0.00 - 7.00 tStat -0.42 P(T<=t) one-tail 0.34 t Critical one-tail 1.89 P(T<=t) two-tail 0.69 t Critical two-tail 2.36 P<0.05 accept Ho Diagenetically Altered fstrfev) Source-Bordering (st.dev) Mean 1.90 1.61 Variance 1.03 0.35 Observations 23.00 16.00 Hypothesized Mean Difference 0.00 df 36.00 tStat 1.11 P(T<=t) one-tail 0.14 t Critical one-tail 1.69 P(T<=t) two-tail 0.27 t Critical two-tail 2.03 P>0.05 accept Ho Standard'Deviationt-Test Diagenetically Altered (st.dev) Lunette (st.dev) Mean 1.90 1.25 Variance 1.03 0.68 Observations 23.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 tStat 1.65 P(T<=t) one-tail 0.07 I Critical one-tail 1.83 P(T<=t) two-tail 0.13 t Critical two-tail 2.26 P>0.05 accept Ho SourcerBordering (st.dev) Lunette (stdev) Mean 1.61 1.25 Variance 0.35 0.68 Observations 16.00 6.00 Hypothesized Mean Difference 0.00 df 7.00 I Stat 1.00 P(T<=t) one-tail 0.18 t Critical one-tail 1.89 P(T<=t) two-tail 0.35 t Critical two-tail 2.36 P>0.05 accept Ho Lower Palaeachannel (st.dev) Upper Palaeochannel (st.dev) Mean 1.79 1.46 j Variance 1.98 0.88 Observations 8.00 72.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 0.64 P(T<=t) one-tail 0.27 t Critical one-tail 1.86 P(T<=t) two-tail 0.54 t Critical two-tail 2.31 P>0.05 accept Ho Lower Palaeochannel (stdev) Overbank (st.dev) Mean i 1.79 2.25 Variance 1.98 1.03 Observations 8.00 15.00 Hypothesized Mean Difference 0.00 df 11.00 tStat -0.82 P(T<=t) one-tail 0.21 t Critical one-tail 1.80 P(T<=t) two-tail 0.43 t Critical two-tail 2.20 P>0.05 accept Ho Standard Deviation t» Test Lower Palaeochannel (st.dev) Dune Surface (stdev) Mean 1.79 1.09 Variance 1.98 0.22 Observations 8.00 11.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 1.34 P(T<=t) one-tail 0.11 t Critical one-fail 1.86 P(T<=t) two-tail 0.22 t Critical two-tail 2.31 P>0.05 accept Ho Lower palaeochannel (st.dev) Diagenetically Altered (st dev) Mean 1.79 1.90 Variance 1.98 1.03 Observations 8.00 23.00 Hypothesized Mean Difference 0.00 df 10.00 tStat -0.21 P(T<=t) one-tail 0.42 t Critical one-tail 1.81 P(T<=t) two-tail 0.84 t Critical two-tail 2.23 P>0.05 accept Ho Lower Palaeochannet (st.dev) Source-Bordering (stdev) Mean 1.79 1.61 Variance 1.98 0.35 Observations 8.00 16.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 0.34 P(T<=t) one-tail 0.37 t Critical one-tail 1.86 P(T<=t) two-tail 0.74 t Critical two-tail 2.31 P>0.05 accept Ho Lower Palaeochannel (st.dev) Lunette (st.dev) Mean 1.79 1.25 Variance 1.98 0.68 Observations 8.00 6.00 Hypothesized Mean Difference 0.00 df 11.00 tStat 0.90 P(T<=t) one-tail 0.19 t Critical one-tail 1.80 P(T<=t) two-tail 0.39 t Critical two-tail 2.20 P>0.05 accept Ho ___^_ Standard Deviation t-Test Upper Palaeochannel (stdev) Overbank (st.dev) Mean 1.46 2.25 Variance 0.88 1.03 Observations 72.00 15.00 Hypothesized Mean Difference 0.00 df 19.00 tStat -2.77 P(T<=t) one-tail ! 0.01 t Critical one-tail 1.73 P(T<=t) two-tail 0.01 t Critical two-tail 2.09 P<0.05 reject Ho Upper Palaeochannel (stdev) Dune Surface (st.dev) Mean 1.46 1.09 Variance 0.88 0.22 Observations 72.00 11.00 Hypothesized Mean Difference 0.00 df 24.00 tStat 2.04 P(T<=t) one-tail 0.03 t Critical one-tail 1.71 P(T<=t) two-tail 0.05 t Critical two-tail 2.06 PO.05 accept Ho Upper Palaeochannel (stdev) Diagenetically Altered (stdev) Mean 1.46 1.90 Variance 0.88 1.03 Observations 72.00 23.00 Hypothesized Mean Difference 0.00 df 35.00 tStat -1.84 P(T<=t) one-tail 0.04 K Critical one-tail 1.69 P(T<=t) two-tail 0.07 t Critical two-tail 2.03 P>0.05 accept Ho Upper Pafaeochannel (st;dev) Source-Bordering (stdev) Mean 1.46 1.61 Variance 0.88 0.35 Observations 72.00 16.00 Hypothesized Mean Difference 0.00 df 34.00 tStat -0.83 P(T<=t) one-tail 0.21 t Critical one-tail 1.69 P(T<=t) two-tail 0.41 t Critical two-tail 2.03 P>0.05 accept Ho 253 Standard Deviation t-Test Upper Palaeochannel (st.dev) Lunette (st.dev) Mean 1.46 1.25 Variance 0.88 0.68 Observations 72.00 6.00 Hypothesized Mean Difference 0.00 Df 6.00 tStat 0.61 P(T<=t) one-tail . 0.28 t Critical one-tail 1.94 P(T<=t) two-tail 0.57 t Critical two-tail 2.45 P>0.05 accept Ho 254 APPENDIX 7 TWO-TADLED T-TEST (P=0.05) ON THE SAND FRACTION MEAN GRAIN-SIZE AND STANDARD DEVIATION Appendix 7.1 Mean Grain-Size t-Test: Assuming Unequal Variances Mean Grain-Sizet-Test Lower Palaeochannel (mean) Upper Palaeochannel (mean) Mean 0.55 1.93 Variance 0.42 0.50 Observations 8.00 72.00 Hypothesized Mean Difference 0.00 df 9.00 tStat -5.63 P(T<=t) one-tail 0.00 t Critical one-tail 1.83 P(T<=t) two-tail 0.00 t Critical two-tail 2.26 P<0.05 reject Ho Lower Palaeochannel (mean) Source-Bordenng (mean) Mean 0.55 2.44 Variance 0.42 0.02 Observations 8.00 16.00 Hypothesized Mean Difference 0.00 df 7.00 tStat -8.08 P(T<=t) one-tail 0.00 t Critical one-tail 1.89 | P(T<=t) two-tail 0.00 t Critical two-tail 2.36 P<0.05 reject Ho Overbank (mean) Lower Palaeochannel (mean) j Mean 2.55 0.55 Variance 0.15 0.42 Observations 15.00 8.00 Hypothesized Mean Difference 0.00 df 10.00 tStat 7.97 P(T<=t) one-tail 0.00 t Critical one-tail 1.81 P(T<=t) two-tail 0.00 t Critical two-tail 2.23 | P<0.05 reject Ho | Mean Grain+Size t- Test Dune Surface Sands (mean) Lower Palaeochannel (mean) Mean 2.40 0.55 Variance 0.03 0.42 Observations 11.00 8.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 7.81 P(T<=t) one-tail 0.00 t Critical one-taii 1.86 P(T<=t) two-tail 0.00 t Critical two-fail 2.31 P<0.05 reject Ho Diagenetically Altered (mean) Lower Palaeochannel (mean) Mean 2.37 0.55 Variance 0.12 0.42 Observations 23.00 8.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 7.55 P(T<=t) one-tail 0.00 t Critical one-tail 1.86 P(T<=t) two-tail 0.00 t Critical two-tail 2.31 P<0.05 reject Ho Lunette (mean) Lower Palaeochannel (mean) Mean 2.63 0.55 Variance 0.03 0.42 Observations 6.00 8.00 Hypothesized Mean Difference 0.00 Df 8.00 tStat 8.67 P(T<=t) one-tail 0.00 t Critical one-tail 1.86 P(T<=t) two-tail 0.00 t Critical two-tail 2.31 P<0.05 reject Ho Overbank (mean) Upper Palaeochannel (mean) 1.93 Mean 2.55 0.50 Variance 0.15 Observations 15.00 72.00 Hypothesized Mean Difference 0.00 df 36.00 tStat 4.77 P(T<=t) one-tail 0.00 Critical one-tail 1.69 P(T<=t) two-tail 0.00 Critical two-tail 2.03 P<0.05 reject Ho Mean Grain-Size t'Test Source-Bordering (mean) Upper Palaeochannel (mean) Mean 2.44 1.93 Variance 0.02 0.50 Observations 16.00 72.00 Hypothesized Mean Difference 0.00 df 86.00 tStat 5.53 P(T<=t) one-tail 0.00 t Critical one-tail 1.66 P(T<=t) two-tail 0.00 t Critical two-tail 1.99 P<0.05 reject Ho DuneSurface Sands (mean):: Upper Palaeochannel (mean) Mean 2.40 1.93 Variance 0.03 0.50 Observations 11.00 72.00 ti Hypothesized Mean Difference 0.00 df 61.00 tStat 4.71 | P(T<=t) one-tail 0.00 t Critical one-tail 1.67 P(T<=t) two-tail 0.00 t Critical two-tail 2.00 P<0.05 reject Ho Diagenetically Altered (mean) Upper Palaeochannel (mean) Mean 2.37 1.93 Variance 0.12 0.50 Observations 23.00 72.00 Hypothesized Mean Difference 0.00 df 76.00 tStat 4.01 P(T<=t) one-tail 0.00 t Critical one-tail 1.67 P(T<=t) two-tail 0.00 t Critical two-tail 1.99 f P<0.05 reject Ho I Lunette (mean) Upper Palaeochannel (mean) Mean 2.63 1.93 Variance 0.03 0.50 Observations 6.00 72.00 Hypothesized Mean Difference 0.00 df 28.00 tStat 6.58 P(T<=t) one-tail 0.00 t Critical one-tail 1.70 P(T<=t) two-tail 0.00 t Critical two-tail 2.05 j P<0.05 reject Ho Mean Grain-'Size t-Test Overbank (mean) Source-Bordering (mean) Mean 2.55 2.44 Variance 0.15 0.02 Observations 15.00 16.00 Hypothesized Mean Difference 0.00 df 18.00 tStat 1.05 P(T<=t) one-tail 0.15 t Critical one-tail 1.73 P(T<=t) two-tail 0.31 t Critical two-tail 2.10 P>0.05 accept Ho Dune Surface Sands (mean) Overbank (mean) Mean 2.40 2.55 Variance 0.03 0.15 Observations 11.00 15.00 Hypothesized Mean Difference 0.00 df 21.00 tStat -1.31 P(T<=t) one-tail 0.10 t Critical one-tail 1.72 P(T<=t) two-tail 0.20 t Critical two-tail 2.08 P>0.05 accept Ho 0 Vejmank (mean) Diagenetically Altered (mean) Mean 2.55 2.37 Variance 0.15 0.12 Observations 15.00 23.00 Hypothesized Mean Difference 0.00 df 28.00 tStat 1.43 P(T<=t) one-tail 0.08 t Critical one-tail 1.70 P(T<=t) two-tail 0.16 t Critical two-tail 2.05 P>0.05 accept Ho Overbank (mean) Lunette (mean) Mean 2.55 2.63 Variance 0.15 0.03 Observations 15.00 6.00 Hypothesized Mean Difference 0.00 df 19.00 tStat -0.64 P(T<=t) one-tail 0.27 t Critical one-tail 1.73 P(T<=t) two-tail 0.53 t Critical two-tail 2.09 P>0.05 accept Ho Mean Grain-Size t-Test Source-Bordering (mean) Dune Surface Sands (mean) Mean 2.44 2.40 Variance 0.02 0.03 Observations 16.00 11.00 Hypothesized Mean Difference 0.00 df 19.00 tStat 0.55 P(T<=t) one-tail 0.29 t Critical one-tail 1.73 P(T<=t) two-tail 0.59 t Critical two-tail 2.09 P>0.05 accept Ho Source^Bordering(mean) Diagenetically Altered (mean) Mean 2.44 2.37 Variance 0.02 0.12 Observations 16.00 23.00 Hypothesized Mean Difference 0.00 df 33.00 tStat 0.77 P(T<=t) one-tail 0.22 t Critical one-tail 1.69 P(T<=t) two-tail 0.44 t Critical two-tail 2.03 P>0.05 accept Ho Source-Bordering (Mean) Lunette (mean) Mean 2.44 2.63 Variance 0.02 0.03 Observations 16.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 tStat -2.46 I P(T<=t) one-tail 0.02 t Critical one-tail 1.83 P(T<=t) two-tail 0.04 t Critical two-tail 2.26 P<0.05 reject Ho Dune Surface Sands (mean) Diagenetically Altered (mean) Mean 2.40 2.37 Variance 0.03 0.12 Observations 11.00 23.00 Hypothesized Mean Difference 0.00 df 32.00 t Stat 0.29 P(T<=t) one-tail 0.39 t Critical one-tail 1.69 P(T<=t) two-tail 0.77 t Critical two-tail 2.04 P>0.05 accept Ho Mean Grain-Size t-Test DuneSurfaCe Sands (mean) Lunette (mean) Mean 2.40 2.63 Variance 0.03 0.03 Observations 11.00 6.00 Hypothesized Mean Difference 0.00 df 12.00 tStat -2.62 P(T<=t) one-tail 0.01 t Critical one-tail 1.78 P(T<=t) two-tail 0.02 t Critical two-tail 2.18 P<0.05 reject Ho Diagenetically Altered (mean) Lunette (mean) Mean 2.37 2.63 Variance 0.12 0.03 Observations 23.00 6.00 Hypothesized Mean Difference 0.00 df 19.00 tStat -2.57 P(T<=t) one-tail 0.01 t Critical one-tail 1.73 P{T<=t) two-tail 0.02 t Critical two-tail 2.09 P<0.05 reject Ho Appendix 7.2 Standard Deviation t-Test: Assuming Unequal Variances Standard Deviation t-Test Lower Palaeochannel (stdev) UpperPalaeochannel (stdev)::: Mean 1.24 0.79 Variance 0.29 0.07 Observations 8.00 72.00 Hypothesized Mean Difference 0.00 Df 7.00 tStat 2.29 P(T<=f) one-tail 0.03 t Critical one-tail 1.89 P(T<=t) two-tail 0.06 t Critical two-tail 2.36 P>0.05 accept Ho Lower Palaeochmnei (stdev) Ovemahk:($tdev) Mean 1.24 0.83 Variance 0.29 0.07 Observations 8.00 15.00 Hypothesized Mean Difference 0.00 df 9.00 tStat 2.00 P(T<=t) one-tail 0.04 t Critical one-tail 1.83 P(T<=t) two-tail 0.08 t Critical two-tail 2.26 P>0.05 accept Ho Lower palaeochannel (st.dev) Source-Bordering (St.dev) Mean 1.24 0.77 Variance 0.29 0.03 Observations 8.00 5.00 Hypothesized Mean Difference 0.00 df 9.00 tStat 2.28 P(T<=t) one-tail 0.02 t Critical one-tail 1.83 P(T<=t) two-tail 0.05 t Critical two-tail 2.26 P<0.05 reject Ho Lower Palaeochannel (stdev) Dune Surface Sands ($t.dev) Mean 1.24 0.63 Variance 0.29 0.01 Observations 8.00 11.00 Hypothesized Mean Difference 0.00 df 7.00 tStat 3.16 P(T<=t) one-tail 0.01 t Critical one-tail 1.89 P(T<=t) two-tail 0.02 t Critical two-tail 2.36 P<0.05 reject Ho Standard Deviation t-Test Lower Palaeochannel (st.dev) Diagenetically Altered (st.dev) Mean 1.24 0.83 Variance 0.29 0.04 Observations 8.00 23.00 Hypothesized Mean Difference 0.00 df 8.00 tStat 2.06 P(T<=t) one-tail 0.04 t Critical one-tail 1.86 P(T<=t) two-tail 0.07 t Critical two-tail 2.31 P>0.05 accept Ho Lower Palaeochannel (stdev) Lunette (stdev) Mean 1.24 0.89 Variance 0.29 0.03 Observations 8.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 t Stat 1.72 P(T<=t) one-tail 0.06 t Critical one-fail 1.83 P(T<=t) two-tail 0.12 t Critical two-tail 2.26 P>0.05 accept Ho Upper Palaeochannel (stdev) Overbank (st:dev) Mean 0.79 0.83 Variance 0.07 0.07 Observations 72.00 15.00 Hypothesized Mean Difference 0.00 df 21.00 tStat -0.51 P(T<=t) one-tail 0.31 t Critical one-tail 1.72 P(T<=t) two-tail 0.61 t Critical two-tail 2.08 P>0.05 accept Ho Upper Palaeochannel (stdev) Source-Bordering (stdev) Mean 0.79 0.72 Variance 0.07 0.01 Observations 72.00 16.00 Hypothesized Mean Difference 0.00 df 59.00 tStat 1.79 P(T<=t) one-tail 0.04 t Critical one-tail 1.67 P(T<=t) two-tail 0.08 t Critical two-tail 2.00 P>0.05 accept Ho Standard Deviation t-Test Upper Palaeochannel (st.dev) Dune Surface Sands (st;dev) Mean 0.79 0.63 Variance 0.07 0.01 Observations 72.00 11.00 Hypothesized Mean Difference 0.00 df ' 44.00 t Stat 3.94 P(T<=t) one-tail ; 0.00 t Critical one-tail 1.68 P(T<=t) two-tail 0.00 t Critical two-tail 2.02 P<0.05 reject Ho Upper palaeochannet (stdev) Diagenetically Altered (stdev) Mean 0.79 0.83 Variance 0.07 0.04 Observations 72.00 23.00 Hypothesized Mean Difference 0.00 df 51.00 tStat -0.78 P(T<=t) one-tail 0.22 t Critical one-tail 1.68 P(T<=t) two-tail 0.44 t Critical two-tail 2.01 P>0.05 accept Ho Upper Palaeochannel (st.dev) Lunette (st.dev) Mean 0.79 0.89 Variance 0.07 0.03 Observations 72.00 6.00 Hypothesized Mean Difference 0.00 df 7.00 tStat -1.25 P(T<=t) one-tail 0.13 t Critical one-tail 1.89 P(T<=t) two-tail 0.25 t Critical two-tail 2.36 P>0.05 accept Ho Overbank (st.dev) Source-Bordering (stdev) Mean 0.83 0.72 0.01 Variance 0.07 Observations 15.00 16.00 Hypothesized Mean Difference 0.00 df 19.00 tStat 1.57 P(T<=t) one-tail 0.07 t Critical one-tail 1.73 P(T<=t) two-tail 0.13 t Critical two-tail 2.09 P>0.05 accept Ho Standard Deviation t-Test Overbank (st.dev) Dune Surface Sands (st:dev) Mean 0.83 0.63 Variance 0.07 0.01 Observations 15.00 11.00 Hypothesized Mean Difference 0.00 df 18.00 tStat 2.83 P(T<=t) one-tail 0.01 t Critical one-tail 1.73 P(T<=t) two-tail 0.01 t Critical two-tail 2.10 P<0.05 reject Ho Overbarik (stdev) Diagenetically Altered (stdev) Mean 0.83 0.83 Variance 0.07 0.04 Observations 15.00 23.00 Hypothesized Mean Difference 0.00 df 24.00 tStat -0.03 P(T<=t) one-tail 0.49 t Critical one-tail 1.71 P(T<=t) two-tail 0.97 t Critical two-tail 2.06 P>0.05 accept Ho | Overbank (stdev) Lunette Sands (st.dev) Mean 0.83 0.89 Variance 0.07 0.03 Observations 15.00 6.00 Hypothesized Mean Difference 0.00 df 14.00 tStat -0.59 P(T<=t) one-tail 0.28 t Critical one-tail 1.76 P(T<=t) two-tail 0.56 t Critical two-tail 2.14 P>0.05 accept Ho Source-Bordering Sands (st.dev) Dune Surface Sands (st.d&v) Mean 0.72 0.63 Variance 0.01 0.01 Observations 16.00 11.00 Hypothesized Mean Difference 0.00 df 24.00 tStat 2.32 P(T<=t) one-tail 0.01 t Critical one-tail 1.71 P(T<=t) two-tail 0.03 t Critical two-tail 2.06 P<0.05 reject Ho Standard Deviation t-Test Source-Bordering Sands (st.dev) Diagenetically Altered (st.dev) Mean 0.72 0.83 1 Variance 0.01 0.04 Observations 16.00 23.00 Hypothesized Mean Difference 0.00 df 36.00 tStat -2.35 P(T<=t) one-tail 0.01 t Critical one-tail 1.69 P(T<=t) two-tail 0.02 t Critical two-tail 2.03 P<0.05 reject Ho Source-Bordering Sands (stdev) Lunette Sands (stdev) Mean 0.72 0.89 Variance 0.01 0.03 Observations 16.00 6.00 ] Hypothesized Mean Difference 0.00 df 7.00 tStat -2.30 P(T<=t) one-tail 0.03 t Critical one-tail 1.89 P(T<=t) two-tail 0.05 t Critical two-tail 2.36 P<0.05 reject Ho Dune Surface Sands (stdev) Diagenetically Altered (stdev) Mean 0.63 0.83 Variance 0.01 0.04 Observations 11.00 23.00 Hypothesized Mean Difference 0.00 df 32.00 tStat -4.19 P(T<=t) one-tail 0.00 t Critical one-tail 1.69 P(T<=t) two-tail 0.00 t Critical two-tail 2.04 P<0.05 reject Ho Dune Surface Sands (stdev) Lunette Sands (stdev) Mean 0.63 0.89 Variance 0.01 0.03 Observations 11.00 6.00 Hypothesized Mean Difference 0.00 df 7.00 tStat -3.53 P(T<=t) one-tail 0.00 t Critical one-tail 1.89 P(T<=t) two-tail 0.01 t Critical two-tail 2.36 P<0.05 reject Ho 265 Standard Deviation t-Test Diagenetically Altered (st.dev) Lunette Sands (st.dev) Mean 0.83 0.89 Variance 0.04 0.03 Observations 23.00 6.00 Hypothesized Mean Difference 0.00 df 9.00 tStat -0.68 P(T<=t) one-tail 0.26 t Critical one-tail 1.83 P(T<=t) two-tail 0.52 rt Critical two-tail 2.26 P>0.05 accept Ho APPENDIX 8 MUNSELL COLOUR INDICES Sample Site: Name Depth i Number (m) Munsell Colour::; Aarpoo Waterhole S1-1 3.10 Pale Yellow 2.5Y 7/4 Coongie Longitudinal Dune S1-1 1 1.00 Reddish Yellow 7.5YR 6/8 Coongie Longitudinal Dune S1-2 1 2.20 ! Reddish Yellow 7.5YR 6/8 Coongie Longitudinal Dune 1 S1-3 9.80 Reddish Yellow 7.5YR 6/8 Coongie Longitudinal Dune S1-4 1 10.60 Light Brownish Gray 10YR 6/2 Coongie Swale 1 S1-1 0.10 Pale Brown 10YR6/3 Coongie Swale 1 S1-2 0.30 Light Gray 10YR 7/2 Coongie Swale 1 S1-3 0.75 Light Brownish Gray 10YR 6/2 Coongie Swale 1 S1-4 2.00 Light Brownish Gray 10YR 6/2 Coongie Swale 1 S1-5 2.70 Light Gray 10YR 7/2 Cullyamurra Waterhole 1 S1-1 2.80 Light Yellowish Brown 10YR 6/4 Cullyamurra Waterhole 1 S1-2 5.00 Brown 10YR5/3 Cullyamurra Waterhole 1 S1-3 5.50 Yellowish Brown 10YR 5/4 Cullyamurra Waterhole 1 S1-4 6.60 Light Brownish Gray 10YR 6/2 Cullyamurra Waterhole 1 S1-5 9.50 Light Gray 10YR 7/1 Cullyamurra Waterhole 2 S2-1 2.80 Very Pale Brown 10YR 7/4 Cullyamurra Waterhole 2 S2-2 4.60 Light Yellowish Brown 10YR 6/4 Cullyamurra Waterhole 2 S2-3 5.70 Light Brownish Gray 10YR 6/2 Cullyamurra Waterhole 2 S2-4 8.50 Pale Brown 10YR6/3 Cullyamurra Waterhole 2 S2-5 11.00 Light Yellowish Brown 10YR 6/4 Cullyamurra Waterhole 2 S2-6 14.70 Light Yellowish Brown 10YR 6/4 Cullyamurra Waterhole 3 S3-1 2.70 Grayish Brown 10YR 5/2 Cullyamurra Waterhole 3 S3-2 6.70 Light Brownish Gray 10YR 6/2 Cullyamurra Waterhole 4 S4-1 2.60 Pale Brown 10YR6/3 Cullyamurra Waterhole 4 S4-2 5.60 Light Yellowish Brown 10YR 6/4 Sample Depth Site Name Number (m) Munsell Colour Cullyamurra Waterhole 4 S4-3 8.50 Very Pale Brown 10YR 7/4 East Dog Bite Lake S1-1 4.00 Yellow 2.5Y 7/6 East Mudlalee Dune S1-1 1.0 Reddish Yellow 5YR 6/8 East Mudlalee Dune S1-2 4.25 Reddish Yellow 5YR 6/6 East Mudlalee Dune S1-3 6.90 Reddish Yellow 5YR 6/6 East Mudlalee Dune S1-4 7.50 Brownish Yellow 10YR 6/8 East Mudlalee Dune S1-5 7.75 Yellowish Red 5YR 5/6 East Mudlalee Dune S1-6 8.10 Brownish Yellow 10YR 6/6 East Mudlalee Dune S1-7 8.20 Brownish Yellow 10YR 6/6 East Mudlalee Dune S1-8 9.00 Reddish Yellow 5YR 6/8 East Mudlalee Dune S1-9 9.40 Light Yellowish Brown 10YR 6/4 Gidgealpa Dune S1-2 3.00 Reddish Yellow 7.5Y 6/6 Gidgealpa Dune S1-4 7.00 Reddish Yellow 7.5Y 6/8 Gidgealpa South S1-1 0.60 Yellow 2.5Y 7/6 Gidgealpa South S1-2 2.00 Pale Yellow 2.5Y 7/3 Gidgealpa South S1-3 4.45 Yellow 2.5Y 7/8 Gidgealpa South S1-4 6.45 Light Gray 2.5Y 7/2 Gidgealpa South S1-5 6.80 Pale Yellow 2.5Y 7/3 Innamincka Race Track S1-1 2.00 Reddish Yellow 7.5Y 6/6 Innamincka Race Track S1-4 3.60 Reddish Yellow 7.5Y 6/6 Marpoo Waterhole S1-1 3.00 Brownish Yellow 10YR 6/6 Marroocutchanie 1 S1-2 3.00 Yellow 2.5Y 7/6 Marroocutchanie 2 S2-1 1.20 Yellow 10YR 7/6 Marroocutchanie 2 S2-2 3.90 Yellow 10YR 7/6 Marroocutchanie 2 S2-3 4.20 Yellow 10YR 7/6 Marroocutchanie 2 S2-4 8.70 Very Pale Brown 10YR 7/4 Marroocutchanie 2 S2-5 10.70 Yellow 10YR 7/8 Merty Merty 1 S1-1 3.85 Pale Yellow 2.5Y 7/3 Sample Depth Site Name Number: (m) Muriisell Colour Merty Merty 1 S1-2 4.45 Light Blue/Gray 2.5Y 6/2 Merty Merty 2 S2-1 1.80 Yellow 2.5Y 7/8 Merty Merty 2 S2-2 2.00 Yellow Red 5YR 5/6 Merty Merty 2 S2-3 3.70 Pale Brown 10YR6/3 Mudlalee Palaeochannel 1 S1-1 3.00 White 2.5Y 8/2 Mudlalee Palaeochannel 1 S1-2 8.60 Pale Yellow 2.5Y 7/3 Mudlalee Palaeochannel 1 S1-3 8.90 White 2.5Y 8/2 Mudlalee Palaeochannel 2 S2-1 2.30 Pale Yellow 2.5Y 8/3 Mudlalee Palaeochannel 2 S2-2 6.00 White 5Y 8/1 Mudlalee Palaeochannel 4 S4-1 1.80 Pale Yellow 2.5Y 7/4 Mudlalee Palaeochannel 4 S4-2 2.20 Very Pale Brown 10YR 7/4 North Dog Bite Lake 1 S1-1 3.70 White 10YR 8/2 North Dog Bite Lake 2 S2-1 2.50 Grayish Brown 10YR 5/2 North Dog Bite Lake 2 S2-2 5.40 Light Yellowish Brown 10YR 6/4 North Dog Bite Lake 2 S2-3 7.70 Grayish Brown 10YR 5/2 Tilcha Waterhole S2-1 3.59 Reddish Yellow 5YR 6/6 Tilcha Waterhole S2-2 4.27 Yellow 10YR 7/6 Tilcha Waterhole S2-3 5.66 Very Pale Brown 10YR 7/4 Tilcha Waterhole S2-4 6.46 Brownish Yellow 10YR 6/6 Tilcha Waterhole S2-5 7.41 Yellow 10YR 7/6 Tilcha Waterhole S2-6 8.49 Yellow 10YR 7/6 Tilcha Waterhole S2-6A 8.70 Light Gray 10YR 7/2 Tilcha Waterhole S2-7 9.33 Red 2.5YR 5/8 Tilcha Waterhole S2-8 9.63 Red 2.5YR 5/8 Tilcha Waterhole S2-9 11.37 Very Pale Brown 10YR 7/4 Tilcha Waterhole S2-10 12.30 Very Pale Brown 10YR 7/4 Tilcha Waterhole 2-11 13.33 Pale Brown 10YR 6/3 Tilcha Waterhole 2-12 14.33 Very Pale Brown 10YR 7/3 Sample Depth SiteilSlame Munsell Colour::: Number (m) i Tilcha Waterhole 2-13 16.33 Brownish Yellow 10YR 6/6 Tilcha Waterhole 2-14 17.59 Light Yellowish Brown 10YR 6/4 Tilcha Waterhole 2-15 18.67 Very Pale Brown 10YR 7/4 Tilcha Waterhole 2-16 19.30 Yellow 10YR 8/6 Tilcha Waterhole 2-17 19.57 Very Pale Brown 10YR 8/4 Tilcha Waterhole 2-18 21.11 Very Pale Brown 10YR 7/4 Tilcha Waterhole 2-19 20.25 Very Pale Brown 10YR 7/4 Tilcha Waterhole 2-22 20.99 Light Yellowish Brown 10YR 6/4 Tilcha Waterhole 2-23 20.45 Very Pale Brown 10YR 7/4 Tilcha Waterhole 2-24 19.70 Very Pale Brown 10YR 7/4 Turra 1 S1-1 2.70 Brownish Yellow 10YR 6/6 Turra 1 S1-2 4.00 Brown 10YR 5/3 Turra 1 S1-3 5.70 Reddish Yellow 7.5YR 6/8 Turra 1 S1-4 8.70 Yellow 10YR 7/8 Turra 2 S2-1 1.00 Brownish Yellow 10YR 6/8 Turra 2 S2-2 2.00 Brownish Yellow 10YR 6/8 Turra 2 S2-3 4.70 Yellow 10YR 7/6 Turra 2 S2-4 8.00 Brownish Yellow 10YR 6/6 Turra 3 S3-1 1.20 Brownish Yellow 10YR 6/6 Turra 3 S3-2 8.20 Yellow 10YR 7/6 Turra 3 S3-3 10.00 Yellow 10YR 7/6 Turra 4 S4-1 1.30 Brownish Yellow 10YR 6/8 Turra 4 S4-2 5.20 Brownish Yellow 10YR 6/8 Turra 4 S4-3 6.00 Brownish Yellow 10YR 6/8 Turra 4 S4-4 6.90 Brownish Yellow 10YR 6/8 Turra 4 S4-5 7.20 Yellow 10YR 7/6 Turra 4 S4-7 9.80 Brownish Yellow 10YR 6/6 Turra 5 S5-1 5.00 Reddish Yellow 7.5YR 6/6 Sample Depth Site Name Number {m) Munsell Colour :: : : j :::: ::::: :::;:.:::::::::::::::::::::¥::: ••• 'i¥' ~' • Turra 5 S5-2 6.40 Reddish Yellow 7.5YR 6/6 Turra 5 S5-3 8.85 Yellow 10YR 7/6 Turra 5 S5-4 10.80 Yellow 10YR 7/8 Turra 6 S6-1 1.10 Yellow 10YR 7/6 Turra 6 S6-2 1.65 Light Yellow Brown 10YR 6/4 Turra 6 S6-3 7.20 Yellow 10YR 7/6 Turra 6 S6-4 8.70 Brownish Yellow 10YR 6/8 Turra Palaeochannel 1 S1-1 1.70 Olive Yellow 2.5Y 6/6 Turra Palaeochannel 1 S1-2 2.25 Yellow 2.5Y 7/8 Turra Palaeochannel 2 S2-1 2.50 Yellow 2.5Y 7/6 Turra Palaeochannel 2 S2-2 3.35 Yellow 2.5Y 7/6 Turra Palaeochannel 3 S3-1 3.70 Pale Yellow 2.5Y 7/4 Turra Palaeochannel 3 S3-2 5.80 Pale Yellow 2.5Y 7/4 Turra Palaeochannel 3 S3-3 6.40 Pale Yellow 2.5Y 7/3 Turra Palaeochannel 3 S3-4 7.70 Light Gray 2.5Y 7/2 Turra Palaeochannel 3 S3-5 8.00 Pale Yellow 2.5Y 7/4 Turra Palaeochannel 3 S3-6 8.90 Yellow 2.5Y 7/6 Turra Palaeochannel 3 S3-7 9.10 White 2.5Y 8/2 Turra Palaeochannel 4 S4-1 3.75 Pale Yellow 2.5Y 7/4 Turra Palaeochannel 4 S4-2 4.20 Pale Yellow 2.5Y 7/4 Turra Palaeochannel 4 S4-3 4.80 Pale Yellow 2.5Y 7/3 Turra Palaeochannel 4 S4-4 5.40 Pale Yellow 2.5Y 7/3 Turra Palaeochannel 4 S4-5 5.80 Light Brownish Gray 2.5Y 6/2 West Mudlalee Dune S2-1 1.20 Reddish Yellow 7.5YR 6/6 West Mudlalee Dune S2-2 2.80 Brownish Yellow 10YR 6/8 West Mudlalee Dune S2-3 3.80 Yellow 10YR 7/6 West Mudlalee Dune S2-4 6.00 Yellow 10YR 7/6 West Mudlalee Dune S2-5 7.40 Yellowish Brown 10YR 5/6 Sample Depth Munsell Colour Site Name Number 1 WMm West Mudlalee Dune S2-6 8.70 Pale Yellow 2.5Y 7/4 West Mudlalee Dune S2-7 10.00 Light Yellowish Brown 10YR 6/4 Wills Grave 1 S1-1 4.20 Very Pale Brown 10YR 7/3 Wills Grave 1 S1-2 5.60 Very Pale Brown 10YR 7/3 Wills Grave 2 | S2-1 2.70 Very Pale Brown 10YR 7/4 Wills Grave 2 S2-2 3.50 Very Pale Brown 10YR 7/4 Wills Grave 2 S2-3 5.50 Light Yellowish Brown 10YR 6/4 Wills Grave 2 S2-4 7.50 Very Pale Brown 10YR 7/4 Wills Grave 2 S2-5 9.00 Very Pale Brown 10YR 7/4 I Wills Grave 2 S2-6 10.00 Light Brownish Gray 10YR 6/2 Wills Grave 2 S2-7 11.60 Light Yellowish Brown 10YR 6/4 Wills Grave 3 S3-1 3.00 Very Pale Brown 10YR 7/3 Wills Grave 3 S3-2 5.70 Very Pale Brown 10YR 7/4 Wills Grave 3 S3-3 8.80 Very Pale Brown 10YR 7/3 Wills Grave 3 S3-4 12.00 Very Pale Brown 10YR 7/3 Wills Grave 3 S3-5 15.00 Light Gray 10YR 7/2 Wills Grave 3 S3-6 17.20 Light Gray 10YR 7/2 Wills Grave 3 S3-7 20.50 Light Gray 10YR 7/2 Wills Grave 4 S4-1 3.00 Very Pale Brown 10YR 7/3 Wills Grave 4 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CO 0 d O d m d d g O d 0 d d d d d d d d d d d i d ; ii:ii:ici:iii i *t CM • CO in r- 0 CN O CO CO CM m CO in in • aP JP aP aP aP XX.X-giX.mmmiX 0 0 xxxxaxx: - - 0 0 0 •* 0 0 - 0 0 0 ai ¥¥14-i¥¥i =P cu 03 (0 (0 (0 ra g ro CO ra CO ra ra c ra ¥::«¥?::: S ra ra ra ra ra (0 ra 2 (0 10 ro ro CO ra Q. (0 CL (0 ai CL (0 ra 3 i_ CL Q. CL Q UJ (0 ra CL 8. ra Q. i— a. CL CL 1— OJ L_ i— i_ '•a (0 a. 1— 1— O- 0 03 1— in 03 Q. CL m 1 CN CO i_ 0 CO •t T— CN CO i_ k. CiN_ a. 03 (0 CaNi in lx-01- 03 CL • OJ 03 1 1 (0 Q. 03 I CL 3 03 01 1 a.03 CN CaMi s. C0N3 1 4TJ 1 CO cQo. CL iii 4k- CL CL CQL. CCNL 0. a. Q. CO CL 4 5a. 51 Q. CL a. a. 51 _J 51 0. Q- CL _0l3 5. cc a. a. —31 O- Q Q- 0. 3 a. 0. a. E E OT OT CL Q. 5a. 2 Q. a. 3 3 O- Qa. Q. OT Q. 2 53 53 3 1- _l 13- H \- 1- Z) UJ 1 3 <3 1- 3 1- ro 3 CL O 3 3 3 1 3 O a « Z ' o3 5 1- < APPENDIX 10 DENDROGRAM 0.1183 0.0936 0.3055 0.5174 0.7292 0. 9411 0.2243 -0.0124 0.1995 0.4114 0.6233 0. 8352 1.0471 TTMni 1 0.8586 I I . WMD22 0.9835 I I I . TIL26A 0.9725 I I I TLD23 0.9281 I I I WMD23 0.9351 I I TLD63 0.7388 I TLD41 0.6891 . TLD22 0.9782 I TIL28 0.8916 ] ] . TLD24 0.9929 J I TIL22 0.8193 . TLD62 0.9711 I I. TIL26 0.9939 II _ TIL23 0.9052 I I . QD12 0.9799 I I 0.6015 I I . TLD21 0.9928 I I I 0.8915 I I I 0 .7993 I I 0.5728 I I WMD21 0.7704 I I 0.3007 0.9098 I I . TLD32 0.9984 I I I . MAR24 0.9888 I I I . TLD33 0.9712 I I I I.--- TLD53 0.9984 I II I I. MAR23 0.9919 I II I I. MAR22 0.9868 I II I. CLD14 0.9251 II TLD54 0.8365 I I . TLD11 0.9963 I I I - -- TLD31 0.9119 I I 281 -- TLD12 0.9959 -- TLD13 0.9542 -- TLD52 0.9982 -- CLD12 0.9932 -- CLD11 0.9975 -- CLD13 0.7337 -- TLD51 -0.0166 i i -- TP36 0.9967 i i -- WIL27 0.9859 i i -- WIL11 0.9997 i i -- CUL12 0.9670 i i i i.- -- TIL224 0.9922 i II i -- WIL35 0.9536 i i i i.-- -- WXL34 0.9724 i n i -- WIL36 0.9693 i.-- i i n -- CUL13 0.8756 i i i i -- ARP11 0.9815 i i i i -- GSP12 0.7872 i i i i .- -- GSP13 0.8306 i i i i i i -- TIL222 0.9761 i i i i -- WIL26 0.7115 i i -- NDB22 0.9941 i i -- WIL37 0.9766 i i -- TIL217 0.9603 i i -- CUL41 0.9430 i i i i .- -- WIL24 0.9951 i i i 0.9483 i -- WIL32 i -- CUL21 0.9318 i i i -- TIL216 0.9906 i i i i i -- MUP11 0.9857 i i i i.- -- WIL22 0.9574 i i n -- WIL25 0.8771 i i -- WIL21 1.0000 i i -- WIL41 0.9925 i i -- WIL33 0.9661 i i i i.- -- WIL23 0.9929 i II i 282 i I I . WIL31 0.9431 i I II i j . CUL25 0.8542 i I I i I I . TIL223 0.9980 i III i WIL12 0.5359 i i NDB23 0.9247 i i I . WIL43 0.9640 i I I i CUL22 0.8913 i i I . CSW13 0.9649 i I I i , CSW14 0.8663 i i CUL23 0.7582 i i CUL15 0.2480 i i i i TLD14 0.3736 i i i i i i MAR21 0.6760 i i i i MAR25 0.0434 i i . NDB11 0.9606 i I i . CUL24 0.9315 i I i I . TIL219 0.9763 i I I i I. CSW12 0.9435 i II i CUL14 0.8642 i i --- NDB21 0.7864 i i •-- TIL218 0.8392 i i •-- WIL44 0.9676 i i •-- CUL32 0.9409 i I i I •-- COL42 0.9860 i I I i •-- CSW11 0.7208 i i •-- WIL42 0.5812 i 1.0000 i . CUL11 i I CUL31 0.7609 i i CSW15 -0.1772 . EMD12 0.8798 I I . WMD24 0.9258 I I I I . TLD42 0.9732 III I I I. TIL25 0.9972 I I II TIL24 0.7292 TIL29 0.5356 EMD13 0.8198 283 I . EMD14 0.2426 I I I I . EMD15 1.0000 I I I I I . MM23 0.9414 II I II I . TIL211 0.9930 I I II I I . TIL212 0.7805 II I II I . TLD13 0.9832 I I II II I . TP33 0.9497 I I II I I . TP44 0.7331 II I II I . WMD26 0.9212 I I II II I . MM11 0.7996 I I II I I II . TP41 0.9965 I I III I I II . TP32 0.9944 I I III I I . TP21 0.6439 I II I II . EMD16 1.0000 I III I II . TP34 0.9217 I I II I I II . EMD19 1.0000 I I III I I II . TLD47 0.9880 I I III I II . TP22 0.9002 I I II I I I I . EMD18 1.0000 I I III I II . MM12 0.7402 I I II I I II . WMD25 0.9927 I I III ! I II . MAR12 0.8728 I I III ! I III. TLD64 0.9926 I I I I I I j ! II . TLD43 0.8397 I I III j ! . WMD27 0.3839 I II j ! I . EMD17 1.0000 I II I j j j . MUP42 0.7689 I II I r ! I I . MUP22 0.9766 I II II j. j x . MUP41 0.5798 I III I j j i . TLD45 0.7682 I I I I I I TP11 -0.0327 I I JJ . TLD44 0.9215 I I I j. j I . TP12 0.9880 II II j. j . GSP11 0.6935 I I I j j I . TP35 0.8874 II II I I I . MUP12 0.8912 I I II 284 i i CUL43 0.6191 i i i i MARP11 0.8037 i i i i MM21 0.9953 i i i i MM22 0.2940 i i i i TP42 0.8390 i i i i TIL210 0.7830 i i i i TP31 0.6606 i i i i TP37 0.7418 i i i i TIL215 0.8988 i i i i MUP21 0.8569 i i i i MUP13 0.5870 i i i i EDB11 0.6793 i i i i TIL213 0.9938 i i i i TIL214 0.8976 i i i i GSP15 0.8147 i i GSP14 +-- -- + -- - + + -- i, + -- + -- - + -0. 2243 -0.0124 0.1995 0.4114 .6233 0.8352 1.0471 -0.1183 0.0936 0.3055 0.5174 .7292 0.9411 DENDROGRAM - VALUES ALONG X-AXIS ARE SIMILARITIES ^ o vd o o m PH