Luminescence dating at the archaeological and human burial site at Roonka, South Australia

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Quaternary Science Reviews 25 (2006) 2586–2593

Luminescence dating at the archaeological and human burial site at Roonka, South Australia G.B. Robertson, J.R. Prescott Department of Physics, University of Adelaide, Adelaide 5005, Australia Received 1 December 2004; accepted 4 July 2005

Abstract Roonka, the Aboriginal habitation and burial site on the River Murray, South Australia, was excavated from 1968 to 1983. In 1983, thermoluminescence (TL) ages were obtained for several fireplaces at the East Bank site. Sandy dune sediments collected from East Bank were also analysed using traditional TL methods and ages were found at depths down to the base at 2.6 m. Now, 20 years on, with optical dating methods well established, it seemed instructive to repeat the measurements using new techniques, specifically the single aliquot regeneration dose protocol. This has provided confirmation of the TL ages and provided an age framework for both the archaeological and geological aspects of Roonka. The ages confirm the archaeological description of the structure of the dune and show that only the top 20% is the Holocene Bunyip formation. The lower part is assigned to the Woorinen Formation, formed during and after the last glacial maximum. Burials at East Bank took place between about 16 and 20 ka, substantially earlier than those on the Roonka Flat, but consistent with the earliest evidence of occupation on the Flat. They are one of the very few securely dated Pleistocene burials in Australia. Whether the individuals were gracile or robust is not known. r 2006 Elsevier Ltd. All rights reserved.

1. Introduction Beginning in 1968, excavations were carried out at a prehistoric site at Roonka on the River Murray in South Australia by archaeologists from the South Australian Museum (Fig. 1). They comprised two locations: Roonka Flat in the river valley itself and East Bank, on higher ground across the river (Fig. 2). The project was led by Pretty (1977) who, with the agreement of the descendents of the Ngaiawang people, excavated a most productive site at Roonka Flat and found many Aboriginal artefacts and over two hundred burials. A 14C age was obtained for charcoal fragments from one of three buried fireplaces at the base of the excavation and it was concluded that occupation of the site dated back 18,000 years and there was a succession of burials 9000 years old to modern (Pretty, 1977, 1988). It was one of the first Pleistocene sites to be excavated in Australia. Corresponding author.

E-mail address: [email protected] (J.R. Prescott). 0277-3791/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2005.07.017

In 1975–1977, to locate living sites, a further trench was dug on the other, east, side of the river in a stable dune which contained evidence of Aboriginal artefacts. The site became known as East Bank (EB1) (Fig. 2). A 6 m
5 m trench was dug to a depth of 2.6 m (Fig. 3). The excavation was meticulously recorded by Pretty. In particular, three former surfaces, which separate the stratigraphic divisions of the dune, were cleared as surfaces, before excavation proceeded to greater depths. These surfaces mark significant time divisions for both geological and archaeological discussion. The sequence of sediments can be divided into several layers. The top layer 1, about 0.1 m thick, consists of modern wind blown sand, layer 2, 0.1–0.5 m, contains Aboriginal fireplaces. Layer 3 consists of an upper layer, 3a, 0.5–1 m, formed by dune remobilization and archaeologically sterile, and a lower layer 3b, an undisturbed remnant of the original dune, which held two burials and part of a third. Beneath the dune is an indurated layer of red-brown silt and below that a calcrete horizon. There is no obvious palaeosol development within the dune itself.

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eP

en in

Eyre Peninsula

Yo rk

Lake Mungo Roonka Kow Swamp

0

100 200 300 400 km Roonka

South Eastern Australia

Fig. 1. South eastern Australia showing the location of Roonka and other places mentioned in the text.

0

200 400 600 800 1000 Metres The East Bank N MU

Trench 1

Y

RRA

‘Roonka’

RIV

ER

Roonka Flat

Trench A

Fig. 2. Map of the Roonka area showing excavation sites at Roonka Flat and East Bank. After Rogers (1990). Light shading shows the alluvial deposits of the Roonka flat; heavier shading shows sand deposits of East Bank and the Roonka Flat.

2. Previous luminescence dating work on the East Bank dunes In layer 1 (the top 50 cm) two fireplaces containing hearth stones provided suitable material for TL dating using both fine grains and 100 mm quartz grains extracted from the heated calcrete stones. The method followed that

used for pottery (Aitken, 1985). Dates obtained were 1000770 years and 25007150 years (Prescott, 1982; Prescott et al., 1983). The first attempt to date the dune sand itself at Roonka was made by Prescott (1983). The method recognised that, for sediments, the zeroing mechanism is by sunlight bleaching rather than by heating but used TL methods. The method measured first and second glow curves and the full growth curve was constructed by combining the two using the Australian Slide Method (Prescott et al., 1993). At East Bank, ages of 2.770.3 ka at about 30 cm and 14.572 ka at 1 m were found. It was recognised that the bleaching of the sand may not have been complete, so these ages may have been overestimated. At the same time an age of 65712 ka was obtained in the terra rossa which forms the base of the Roonka Flat site, below the occupation level. This age is likely to mark the time of deposition of the sand rather than that of formation of the terra rossa itself. In 1984, the late John Hutton collected samples of sand at different levels throughout the profile and made extensive measurements of element composition. These showed the dune to be composed of nearly pure quartz sand. He also collected data on trace elements to clarify the history of the formation of the dune. In addition, he obtained TL ages at a number of depths down the profile of the pit. Dose-rate measurements were made at the site using a gamma ray scintillometer and independently for potassium using XRF, for uranium and thorium using thick-source alpha counting, delayed neutron activation (DNA) and neutron activation analysis (NAA) (Prescott and Hutton, 1995). Ages were obtained ranging from 3.5 ka at 0.3 m–45 ka at 2 m but the results were not published. Hutton’s systematic study of the geochemistry of the dune supports the archaeological evidence for its

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structure. Table 1 taken from his unpublished manuscript, summarises the results. He writes, ‘‘ythe total potassium and aluminium indicate low clay and/or feldspar [as for] a

F11 F2

N

F13

OS 1M

F2 F11

OS F13

1M Fig. 3. Plan and elevation of the Roonka East Bank trench 1 excavation. F2 and F11 are fireplaces. F13 shows the location of one of the burials. The two well-defined former surfaces, OS, are shown. After Prescott (1983). Most samples were taken from behind the face indicated by the triangle.

nearly pure quartz sand dune. Titanium, zirconium and thorium, for all except the 60–80 cm sample, are about average for surface sediments but the average Ti/Zr and Al/Y ratios show important variations. These ratios suggest that the 60–80 cm samples are very different from the rest of the dune and support the field and other evidence that there are two old surfaces, one at 45 cm and another at 100 cm. Although the ratios of Ti/Zr and Al/Y, which are associated with minerals that do not weather, show discontinuities, the Ca/Sr ratio which progressively decreases from surface to 180 cm, suggests stability of long enough duration for the slightly soluble calcium carbonate minerals to come to an equilibrium with repeated solution and crystalisation. During this process low strontium calcite forms at the surface and at the lower depths the solutions progressively contain more strontium and lead to lower Ca/Sr ratio in the calcite (Hutton and Dixon, 1981). At 190 cm there is an abrupt change in all properties to what appears to be the much older surface on which the dune has developedy’’. Hutton’s geochemical analyses therefore support the archaeological excavation evidence for the structure of the dune, viz, two old surfaces, a different base and a stability long enough for high strontium calcite to form. No attempts were made at that time to use any of the new TL methods being developed to allow for the possible incomplete bleaching of samples, such as partial bleach (Wintle, 1997) and selective bleach (Prescott and Mojarrabi, 1993). One of the most significant developments in luminescence dating was the recognition by Huntley that emission of light could be stimulated by optical means as well as by heat and this has led to the development of optical dating methods, known as optically stimulated luminescence (OSL) (Huntley et al., 1985). Overcoming the question of

Table 1 Element analyses for Roonka East Bank Sample depth (m)

No. of samples

Al (mg/g)

K (mg/g)

Ti (mg/g)

Zr (mg/g)

Th (mg/g)

Ca/Sr

Ti/Zr

Al/Y

Y/Th

0–0.3 0.6–0.8 1.0–1.2 1.7–1.8 1.9–2.3

4 2 3 2 2

19,000 16,000 17,000 21,000 36,000

10,000 10,000 10,000 12,000 11,000

1500 700 1100 1600 2800

280 80 240 310 310

7 3 7 9 11

400 200 180 100 350

5.2 8.8 4.6 5.0 9.0

1500 2000 1400 1400 1800

2.0 2.0 1.9 1.8 2.0

Depth (m)

Uranium (mg/g)

Thorium (mg/g)

%K

0.3 0.6 1.1 1.4 1.8 1.9 2.1 2.6

1.2270.19 0.9370.11 1.2070.19 0.9070.10 1.7170.12 1.6270.12 2.0370.13 1.9270.13

6.8170.23 3.1070.30 6.0070.22 3.2770.30 7.2670.30 9.8170.30 3.2670.30 2.8670.30

0.9370.01 0.9370.01 0.9670.03 0.8870.01 1.1070.03 1.2270.05 0.8970.05 0.9670.05

The upper section of the table shows the analyses used by Hutton in analyzing the structure of the dune and shows the changes in trace element composition linked to the various layers. The lower section of the table shows the element analyses used in the age determinations.

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incomplete bleaching is best resolved using a method which involves the rapidly bleaching 325 1C TL peak and optical selection. A component of OSL in quartz is understood to come from rapidly bleached levels (e.g. Prescott and Robertson, 1997; Wintle, 1997). Another important development was the introduction of single aliquot regeneration (SAR) techniques, which increase the accuracy of measurements by reducing intersample variability (Murray and Wintle, 2003). These techniques are now well established. It was therefore timely to return to the original East Bank samples and date them again using single aliquot techniques. Comparison of ages found by different methods is essential in validating the methods used. Furthermore, due to the untimely death of Pretty, developments implicit in his 1988 paper have not followed. It is hoped that the present paper will go some way to putting at least the age determinations on record.

3. New measurements Many of the samples prepared by Hutton were usable and others for this study were prepared from the original sand samples. The preparation of 100 mm quartz grains followed the usual procedures of HF etching and heavy liquid separation at a specific gravity of 2.67. Eight samples were measured, corresponding to different depths to 2.6 m, as shown in Table 2. Because the method used for the estimation of equivalent dose in the present study differs in some respects from those commonly used for single aliquots, we set them out in some detail. We have used it for many years in processing dosed samples for calibration. In its present version, it is a modified form of the SAR procedure of Murray and Wintle (2003). About 5 mg of grains were deposited on stainless steel discs, confined to the central part of the disc, and measured in a Risø DA-12 reader fitted with an EMI 9635QA photomultiplier and U340 filter. After preheating for 10 s at 250 1C, each disc was given 100 s of shine-down with green-filtered halogen lamp at 125 1C. On the basis of a pilot run, a trial calibration dose was chosen for each sample, approximately equal to that previously measured. The same dose was administered four times with the preTable 2 Equivalent doses (ED) determined from OSL measurements, dose rates and calculated age values for the East Bank samples Depth (m)

ED (Gy)

Dose rate (Gy/ka)

Age (ka)

0.3 0.6 1.1 1.4 1.8 1.9 2.1 2.6

8.371.3 25.270.6 40.371.7 38.572.6 54.171.3 63.676.0 90.075.0 88.676.1

1.9270.06 1.5670.04 1.8470.06 1.4770.04 2.1770.05 2.4570.05 1.7470.07 1.7570.07

4.370.7 16.270.6 21.971.2 26.271.9 24.970.9 26.072.6 51.773.6 50.674.0

2589

heat/shine-down cycle repeated each time. In the language of Murray and Wintle, each irradiation acts as its own test dose. The data for each disc then consists of a ‘‘natural’’ value and first, second, third and fourth test doses. About ten discs were measured for each sample. The procedures can be summarised as follows: Step 1: preheat at 250 1C for 10 s. Step 2: Shine-down for 100 s at 125 1C. Step 3: Irradiate with matching beta dose. Repeat three more times. The protocol begins with the ‘‘natural’’ measurement and is followed by four calibration measurements. After the final shine-down, a further shine-down is repeated immediately, to give a measure of the accumulated slowly bleached background. This can be used to ‘‘trim’’ the background correction at low count rates, although it was not necessary in the present measurements. The luminescence values from each test dose can be regarded as a measure of the sensitivity of the sample to radiation after the preceding shine-down, i.e. before the next one. We determine the sensitivity before the ‘‘natural’’ (zero) shine-down by fitting a curve to the first, second, etc. calibration values at the arguments 1, 2, 3, 4 and extrapolating it back to the y-axis. Call this C0. This corresponds to the signal that would have been produced by the test dose D, had it been possible to administer it before the natural dose was acquired. If Cn is the observed natural value, then the corresponding equivalent dose Ed is given by E d ¼ C n D=C 0 .

(1)

It should be noted that this is not a dose growth-curve. It is a sensitivity curve and defines the change in sensitivity as a function of repeated test doses. It differs from other procedures in that the test doses are approximately equal to the natural dose rather than a fraction of it. The shine-down curves obtained confirmed that the OSL increases with each successive repeat irradiation and shinedown, indicating that there is some change in sensitivity that needs to be corrected for (Fig. 4). The change is commonly linear or close to linear. In the present instance this proved to be the case for younger samples. However, for samples below 1 m, the sensitivity curve became nonlinear and a linear fit to the data underestimated the equivalent dose. It is an interesting question as to what shape the curve is, i.e., what non-linear function should be used for extrapolation. Since the response to a test dose presumably reflects much the same physics as determines the shape of the dose curve, it is plausible to try a mathematical model that has been found useful in fitting dose curves, viz., a saturating exponential. Support for this is found by Chen and Leung (1999) who predicted and confirmed that the pre-dose effect could be modeled by an exponential. Leung et al. (1997) have used a similar method to deal with nonlinear pre-dose. We used a saturating exponential and tested it with dose recovery. Dose recovery measurements

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Counts x100 125

OSL

100

4 3 2 1 N

75

Shine down curves for EB1 : Depth 0.6 m

50 25 1500 10

20

30 40 50 60 70 Shine Down Time in seconds

80

90

100

Fig. 4. A set of shine-down curves for EB1/0.6.

were made on all but two samples. The fitting underestimated the given dose by an average of 8% (variable among the samples). An adjustment, based on doserecovery measurements, was applied. The correction is demonstrated in Fig. 5(a), where the results have been fitted with a linear relationship and extrapolated back to zero. The equivalent dose is the ratio of the natural OSL to the extrapolated value; see relation (1). An example of a non-linear (saturating exponential) fit is given in Fig. 5(b). Dose-rate measurements were obtained from XRF, NAA and DNA for K, Th and U, respectively, and showed good agreement with results obtained previously. The water content of the site was estimated to be 5%. Element concentrations are given in Table 1. The cosmic ray contribution (Prescott and Hutton, 1994) was adjusted for depth and varied from 0.20 to 0.12 Gy/ka from the top to the bottom of the sequence. The cosmic ray dose contributes less than 10% to the total dose rate in this particular environment. The total dose-rates are given in Table 2 together with the equivalent doses and the calculated ages. It is seen that, within the experimental errors, there is an increase from the shallowest level to the deepest, spanning the range 4–50 ka. For comparison with previous measurements, the new OSL ages are tabulated in Table 3 along with the TL ages of Hutton (unpublished data) and of Prescott (1983). Not all samples came precisely from the same positions in the profile but are from corresponding stratigraphic depths obtained from the archaeological surveys. The general trends are well-maintained and reaffirm the history of the sequence from modern to ca 50 ka. Contrary to expectation, the ages found by OSL did not come out younger than those obtained by TL, suggesting that there was no problem with insufficient bleaching in the samples. 4. Discussion In addition to the demonstration that consistent ages are obtained for the Roonka East Bank profile with both TL and OSL, the ages found are of significance in both geological and archaeological contexts.

1000

N

0

2 Run number

(a)

Photon Counts

0

Photon Counts

0

4

2500 N 2000

0 (b)

1

2 Run number

3

4

Fig. 5. Sensitivity curves for East Bank samples illustrating the method of equivalent dose measurement described in the text. N denotes the natural OSL and runs 1–4 are the OSL following successive irradiations. These are used as estimates of sensitivity change. A linear or exponential fit is shown, extrapolated back to the y-axis. Note: the zero is suppressed. (a) Sample EB1/0.3 natural sample. Successive doses of 7.0 Gy were administered. The extrapolation is linear. (b) Sample EB1/1.8 dose recovery. Successive doses were 37.5 Gy. The sensitivity curve is non-linear and the data points have been fitted with a saturating exponential. The recovered dose is 3% high.

4.1. Geology The Roonka dunes have a place in the wider study of the palaeo-dunes that extend from near Eyre Peninsula across

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Table 3 Age determinations from the present work (OSL 2004), compared with earlier work (TL 1983: Prescott 1983), (TL 1984: Hutton, unpublished data) Depth (m)

Adelaide code

0.3

AdGL04024

4.370.7

AdTL85007

AdGL04025

16.270.6

AdTL85008 AdTL85009

Layer 2 former surface Layer 3a 0.6 0.8 1

OSL 2004 (ka)

Former surface Layer 3b top 1.1 1.2 1.4

AdGL04030

21.971.2

AdGL04026

26.271.9

Burials 1.7 1.8 1.9

AdGL04027 AdGL04028

Layer 3b base 2.1 2.6

AdGL04029 AdGL04031

Adelaide code

TL 1984 (ka) 3.570.4

Adelaide code

TL 1983 (ka)

AdTL83029

2.770.3

AdTL83030

14.572.0

1371 1672

AdTL85010

2272

24.971.9 26.072.6

AdTL85011

2773

51.773.6 50.674.0

AdTL85012

4575

AdTL83031

414.5

Locations of the layers of the dune sediments are indicated. Adelaide code numbers should be used in quoting results.

Yorke Peninsula and the northern Adelaide Plains into the Murray Basin and north western Victoria (Fig. 1). At Roonka, they overlie a calcrete plain which, in turn, overlies the Murray Basin sediments of Pleistocene age. According to Rogers (1990, 1995), the Roonka dunes belong to the Holocene Bunyip Sand and are reworked from Late Pleistocene terrace deposits found in the river valley itself. They are related to the Molyneaux Sand, found further east in South Australia and Victoria. Both are derived from the Woorinen Formation which, in Victoria, has been assigned 14C ages ranging from 8 ka to 35 ka and TL ages to 26 ka. The present ages for the East Bank dune would appear to identify layer 2 with the Bunyip Sand and clearly place the formation of layers 3a and 3b before the Holocene. Layer 3b represents the core of the original dune, formed during the arid period before and during the Last Glacial Maximum (LGM); the overlying layers, 3a and 2 represent distinct periods of remobilization that occurred between 16 and 3 ka ago. The base of layer 3b at about 25 ka represents the onset of formation of the original dune. Gardner et al. (1987) report TL ages from four dune sites in the Murray Mallee south of Loxton and some 80 km east of Roonka (Fig. 1). Below a mobile cover of quartzose sand, ages of 19, 20, 28 and 35 ka lie within a unit described as Pleistocene aeolian quartzose sand. There is not a close stratigraphic correspondence with the present data but there is no doubt, on the basis of the age comparisons, that they represent the same dune-building period during the LGM. They can be related to the Woorinen Formation in Victoria. The layer 3b would then correspond to the Kyalite member of the Woorinen (Rogers, 1990).

A geological correspondence with the indurated red silt layer between the base of layer 3b at 2 m and the calcrete is harder to establish. With an age in the range 40–50 ka, it would correspond to a period of mild climate. It may correspond to the palaeosol underlying the dune and fluvial deposits of the archaeological site on the Roonka Flat, of age 65712 ka (Prescott, 1983). We return to this archaeological aspect below. In their review article, Hesse et al. (2004) discuss Late Quaternary climates, including the consequences of aridity on dune building. Based on 31 dates for 8 linear dune sites in south eastern Australia, they show that dune building was absent between the isotope stage 5e high sea stand at 125 ka and about 50 ka BP, when dune building began and peaked at and after the LGM. The ages of the various parts of the Roonka dune fit very well with this summary, although our ages show two distinct periods of dune mobilization. Hesse et al. (2004) also note earlier dunebuilding periods at around the time of high sea stands (5e, 125 ka; 7e, 250 ka). These do not seem to be represented at Roonka. 4.2. Archaeology In archaeological terms, the Roonka results are significant in that they set the time of the appearance of the Aboriginal antecedents of the Ngaiawang people as early as 20 ka ago, firmly in the Pleistocene, with presence continuing up to and beyond the time of European settlement. The East Bank excavation was initiated with the objective of finding areas that might have been used as

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living space. Such evidence was found in both trench 1 (the site of the present dating) and trench 2 (not discussed here). Inter alia, fireplace features F2 and F11 were found, TL ages for which were reported by Prescott et al. (1983). Two samples from F2 gave ages of 960760 and 1070770 years. This feature is located within layer 2 and its age is consistent with the field evidence. Fireplace F11 had the appearance of having been exposed on the well-defined former surface of layer 3a and yielded a weighted mean age of 22607190 years (three samples). These ages are not entirely consistent with the three luminescence ages of sand from within layer 2. The OSL and Hutton (unpublished data) TL ages, which are from the same field sample, agree with one another but are apparently older than the TL ages from oven stones from fireplaces. The third TL age comes from a different sample but is compatible within statistical error. A possible explanation is that the sediment sample was not fully reset by exposure to sunlight. By contrast, the oven stones were reset by heat, which should guarantee resetting for them. The possibility of this scenario was already discussed by Prescott (1983) and by Prescott et al. (1983). An alternative explanation is that the fireplace was lit in a hole dug into the pre-existing dune. This is consistent with the archaeological evidence. In addition, two graves and part of a third were found. These were completely within the lower section, 3b, of layer 3; one of them, F13, is shown in Fig. 3. The archaeological evidence is unambiguous that they were inserted from the former surface at 1 m. Six luminescence ages in layer 3b range from 21.971.2 to 26.072.6 ka. It is inferred that the burials cannot have taken place much earlier than 20 ka and this provides a terminus ante quem. Four ages clustered about 16 ka come from layer 3a. This upper part of layer 3 consists of remobilised material and is archaeologically sterile. The burials evidently took place before this remobilization, which provides a terminus post quem. A time for these burials, between 16 and 20 ka, is significantly earlier than the oldest grave on the Roonka Flat viz, tomb 91, which is dated by 14C at 77107450 years BP (ANU 1409/2; OxCal 9150–7950 years). The time of the East Bank burials corresponds more nearly to the 14C age for feature 183, one of three fireplaces from the bottom of trench A on the Roonka Flat: 181507340 years BP (ANU 406; OxCal 22,400–21,450 years), an association made by Pretty (unpublished data). On the basis of a large number of 14C ages, Pretty (1988) argues that the Roonka Flat was first occupied in the Late Pleistocene, apparently abandoned at some time between 16 and 18 ka BP, with reoccupation resumed from about 10 ka onwards. Such a scenario is consistent with the East Bank ages reported here: in particular, the archaeologically sterile layer 3a and the age of the burials. Layer 3a corresponds to an arid period following the LGM. The Roonka East Bank burials are the only known Pleistocene burials in South Australia and may be compared with others of comparable age elsewhere

(Fig. 1). At Lake Mungo, the Mungo 3 skeleton has been dated directly by radiometric means (Simpson and Gru¨n, 1998; Thorne et al., 1999) at around 60 ka; and by the associated sediments in which it was found at 40 ka (Bowler et al., 2003). At Kow Swamp, luminescence ages, from sediments, of 19–22 ka have been found for some forty individuals. Whatever may be said about the actual age of Mungo 3, the skeletal remains are of a gracile individual. On the other hand, at Kow Swamp the people were robust (Stone and Cupper, 2003). These authors discuss possible implications of this difference. They suggest that there is scant evidence for robust humans younger than the LGM. Elsewhere, skull WLH 50 from Lake Garnpung, north of Lake Mungo in the Willandra Lakes, with a Late Pleistocene age of about 13 ka (Simpson and Gru¨n, 1998) has robust features but these have been called into question (see, e.g., Stone and Cupper, 2003). The burials on the Roonka Flat, beginning about 9 ka, show that the Roonka people were undoubtedly gracile and show continuity with present-day Aboriginal people at Gerard and Raukkan (Pretty et al., 1998). The East Bank burials have potential to contribute to this debate. The skeletal material from the burials, unlike those on the Roonka Flat, was much degraded and noted in the field book as, ‘‘little more than shadows in the sand’’. For this reason, they were lifted entire in the enclosing sediment. However, because of the untimely death of Graeme Pretty, they remain unexamined. There are no 14C ages for the burials themselves. It appears important to examine them to determine their morphology. Steps are being taken to do this. Acknowledgements The work reported here was originally carried out as a contribution to the Roonka Archaeological Project of the Museum of South Australia, initiated and supervised by the late Graeme Pretty. The late John Hutton was closely involved in dating work at East Bank. We have incorporated (with acknowledgement) some unpublished material of both these individuals. We are greatly indebted to them. Various people assisted in the collection of samples in the 1980s for which we are grateful. We acknowledge helpful suggestions from R. Chen, J. Feathers, A. Lang and R. Roberts. The work was supported by the Australian Research Council, the Australian Institute of Nuclear Science and Engineering and by the Archaeometry Special Fund of the Physics Department, University of Adelaide. References Aitken, M.J., 1985. Thermoluminescence Dating. Academic, London. Bowler, J.M., Johnston, H., Olley, J.M., Prescott, J.R., Roberts, R.G., Shawcross, W., Spooner, N.A., 2003. New ages for human occupation and climatic change at Lake Mungo, Australia. Nature 421, 837–840.

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