A large area archaeological excavation at Cuddie Springs. (News & Notes).

Field, Judith ; Fullagar, Richard ; Lord, Garry 等

Key-words: megafauna, Cuddle Springs, stone artefacts, environmental change

There are three problematic but connected processes during the last 100,000 years of Australian prehistory. These are: the date of initial human settlement; understanding the period of climatic flux culminating in the Last Glacial Maximum around 18-22,000 years ago; and explaining the extinction of the megafauna. The timing of human arrival and population expansion rates are not well understood though most environments were occupied by about 30,000 BP (Mulvaney & Kamminga 1999: 172-89). While the broad framework of climatic change during the Late Pleistocene has been established, localized environmental conditions are more difficult to resolve, particularly in the arid zone. The megafaunal extinctions were a global phenomenon and explanatory models, at least for North America and Australia, depend in different ways on the role of people and climate change (Martin & Klein 1984; Flannery 1994; Choquenot & Bowman 1998; Horton 2000; Head 2000; Wroe & Field 2001).

If we accept recently reported ages of selected megafaunal localities in Australia and West Papua (Roberts et al. 2001) and luminescence dates for a human burial in Australia's southeast (Thorne et al. 1999), then a temporal overlap could be as much as 50,000 years or as little as 10,000 years. Either way it is hard to continue to argue for humans as the primary agent in the extinction process, especially if, as argued by Flannery (1994), human hunters dispatched the megafauna within a short time after their arrival. On the other hand, widely accepted dates for initial human arrival in Australia are from 40-45,000 years and a case could be made that most megafaunal extinctions had already occurred (O'Connell & Allen 1998). In Tasmania, megafauna appear to have become extinct prior to the arrival of people (see Cosgrove & Allen 2001). Ecological data suggest more complex processes at work, whether or not humans are directly implicated. For example, browsers dominate the extinct faunal assemblage in Australia; those that survived underwent phyletic dwarfing and conditions improved for grazers. Furthermore, the same restricted range of species are consistently represented in Late Pleistocene sites. Moreover, it is not clear precisely when, where or how rapidly any particular species became extinct (e.g. Miller et al., 1999; Field & Boles, 1998). Wright (1986) predicted that megafaunal extinctions probably represented a mosaic of events across the continent and as such the evidence needs to be evaluated on a site-by-site basis.

It is rare to find megafaunal bones in association with artefacts anywhere in Australia, and Cuddie Springs is the only known site on the Australian continent where such a stratified record can be found. The aim of this paper is to summarize the results of the 1997 excavations, that provide new data on site structure, and support the broad stratigraphic sequence described in earlier work.

Cuddie Springs is an ephemeral lake in the semi-arid southeast. Flaked stone artefacts are found in direct physical association with a range of megafauna that includes Genyornis newtoni, Diprotodon sp. and Sthenurus sp. in a stratified deposit of lacustrine clays, dated to between ~36,000 and 27,000 years ago (Field & Dodson 1999; Fifield et al. in press; TABLE 1). An environmental record spanning the period of human/megafauna overlap provides a picture of local and regional conditions through time (Field et al. in press).

The human/megafauna association at Cuddle Springs is in a sealed unit between ~1 m and ~1.7 m depth (FIGURE 1). The upper limit, at ~1 m depth, is defined by a deflation pavement probably formed over a 10,000-year period (Field et al. in press). It consists almost entirely of flaked stone artefacts (~50,000 artefacts/cu. m) and is less than 5 cm in depth. The lower limit, at ~1.7 m depth, is a second old land surface described as a beach lag deposit that caps a band of concreted ferruginized sands. Within this horizon are two identifiable stratigraphic units representing different environmental phases (Field & Dodson 1999). The assemblages associated with each stratigraphic unit are distinctly different from each other and megafauna are present in both horizons (Furby 1995).

[FIGURE 1 OMITTED]

The association of bones and stones implies contemporaneity of people and animals, and this is supported by recent dating studies indicating that there are no older sediments in the horizons which would suggest intrusion of material from elsewhere (Roberts et al. 2001). Direct dating of the bones by Amino Acid Racemisation (AAR) or the AMS radiocarbon technique (Clarke 1999; Field & White, unpublished results) have been unsuccessful and electron spin resonance (ESR) studies are pending. Establishing a link between the people and animals is also difficult. Surface modifications from butchering, in the form of cutmarks or breakage patterns, can be absent on bones of large animals (Pickering 1995) and there are few cutmarks on any bones at Cuddie Springs. For this reason usewear and residue studies are important in identifying tasks associated with artefact use and site functions. Spatial patterning and site structure are important aspects of reconstructing site activities. The sheer size of the fauna means a large area excavation is imperative.

At Cuddle Springs, a 15x15-m area was opened down to the deflation pavement, dated by radiocarbon and OSL to around 28,000 years (FIGURES 2 & 3, TABLE 1). A 15x15-m excavation is a minimum requirement if issues such as site structure and patterning of hunter-gatherer camps are to be investigated, as has been documented in ethnographic studies for the Central Australian arid zone (e.g. Spurling & Hayden 1984; O'Connell 1987; Nicholson & Cane 1991). Investigations of site function at Cuddle Springs have previously been limited by the small trench size (~2x2 m).

[FIGURES 2-3 OMITTED]

The 1997 excavations aimed at establishing the nature of the overburden which is thought to be disturbed, assessing the spatial continuity of the Pleistocene archaeological deposits, and to sample the earliest archaeological levels for further evidence of cultural material in association with megafaunal elements. The initial findings of the field season include:

i Conclusive evidence for disturbance of the overburden with the discovery of a number of cow skeletons lying on top of the deflation pavement. Radiocarbon dates show age inversions in the sediment directly overlying the deflation surface (TABLE 1) and the undifferentiated clays of the upper i m are in contrast to the stratified sediments below the deflation pavement. Glass flakes and historic material (including nails and wire) have also been recovered from the overburden. No modern material has been recovered from within or below the deflation surface.

The cow bones in the overburden represent individuals found in discrete locations. The bones were not all lying flat but in different orientations (FIGURE 4), consistent with trampling by large herbivores (see Haynes 1985: 61). Anderson & Fletcher (1934) found the remains of bullocks and horses in the upper sediments during Australian Museum excavations in 1933, but there were few contextual details reported. The orientation of the cow bones from the 1997 excavations is not dissimilar to those of the megafauna lying on the old land surface at ~1.7 m depth, suggesting that the depositional processes in train at Cuddie Springs have not changed significantly for many millennia.

[FIGURE 4 OMITTED]

ii Establishing the spatial extent of the Pleistocene deflation pavement at approximately 1 m depth. The deflation pavement was found to be continuous across the 15x15-m area, and in a series of backhoe excavated pits (~1x2 m) away from the main trench (see FIGURE 3). FIGURE 5 shows the deflation pavement surface as exposed in the excavation. A trench excavated between the well fence and the well proper has revealed that the pavement was intact across this area. The pavement appears to cover an estimated area of approximately 100 m in diameter; and, within the main trench, shows no evidence of disturbance (such as may occur with cracking or swelling clays); and forms a continuous capping to the Pleistocene deposits.

[FIGURE 5 OMITTED]

iii Establishing the spatial continuity of the archaeological deposits (Archaeological Levels 2,3 and 4). A series of 1x1-m pits were excavated to investigate the nature of the sub-deflation pavement deposits. Archaeological finds were recovered from each square in concentrations and composition consistent with the assemblages from the previously reported excavated squares F10 and G10 (Field & Dodson 1999).

iv At the base of the archaeology (AL) complete elements of Genyornis and flaked stone were recovered. The earliest archaeological levels in square F10 were excavated to the surface of the beach lag deposit. The assemblages recovered from these levels were consistent with material excavated previously from AL1, i.e. the complete lower limb bones of Genyornis, and also included macropod and wombat mandibles as well as flaked stone representing early manufacturing stages.

v Identifying the location of the 1933 Australian Museum trenches. Two of the 1933 excavation trenches were located when the deflation pavement was exposed (see FIGURE 2). These tally with a hand-drawn map of the claypan excavations by the Australian Museum palaeontologist C.S. Anderson (Anderson & Fletcher 1934). The clean breaks in the surface of the deflation pavement indicate it was sub-surface at the time of the 1933 excavations. The wall sections exposed in 1997, adjacent to these pits, clearly show where slumping has occurred confirming reports that the pits were not backfilled following the 1933 excavations.

vi The discovery of an historic well. The well was located over the centre of the depression delineated by the deflation pavement. It appears to be the well where the initial discovery of megafaunal bones was made in the late 1870s (Wilkinson 1885). The well is wood lined and is four feet (~1.2 m) square. There is a 12x12-foot (~4 m) fence made of Callitris sp. logs surrounding the well.

The preliminary results of the 1997 excavations have provided a clear insight into the structure of the upper claypan deposits, the location of the previous excavations of 1933 and the original well. The presence of cow bones in the upper metre of overburden (lying over the deflation surface) and in a number of locations across the excavated trench is further evidence of the disturbed nature of these sediments since European occupation. No cow bones, other introduced fauna or dingo have been found in the assemblages from the deflation pavement or the underlying Pleistocene deposits. This is taken as an indication that the human/megafauna association has not been contaminated by intrusive material. The overburden is also massive in structure, in contrast to the stratified horizon containing the megafauna/human association. The pollen/geomorphological evidence also supports this interpretation (Field et al. in press).

Progress in investigating the site has been slow during the last few years, mainly due to the ephemeral nature of the lake. Local thunderstorm activity can result in inundation of the claypan. Depending on the time of year and the depth of water (usually ~30 cm), the claypan can take months to dry. In 1997 excavation was again complicated by unpredictable rain squalls, with partial inundation of the site. The field season focused on test pitting across the exposed excavation area, targeting Archaeological Levels 2, 3 and 4. The site is now primed for further excavation of Archaeological Levels 1 and 2, horizons where flaked stone artefacts and the bones of megafauna are found in association.

Further studies at the Cuddie Springs site are improving our understanding of human interaction with megafauna. Using conservative estimates of human arrival, the Cuddie Springs sequence indicates a clear overlap of megafauna with people for at least 10,000 years (O'Connell & Allen 1998). Cuddie Springs may be representative of the events taking place through the arid zone in the lead up to the Last Glacial Maximum. Waterholes were drying up, larger animals started perishing because they were incapable of moving to better-watered areas, and people expanded their resource base to maintain a presence in an uncertain environment. Current evidence suggests that megafauna and smaller animals were initially targeted resources. Plant resources, including seeds became more important as higher-ranked resources declined (Furby 1995; Fullagar & Field 1997).

In summary, the discovery of cow bones at the base of the undifferentiated clays provides us with conclusive evidence for extensive bioturbation of the upper sediments, while at the same time providing an in situ taphonomic correlate for the earliest archaeological level. The extent of the deflation pavement, the continuity of that surface and the absence of any major surface deformations are all indications that it has not been breached by modern material, nor reworked in any significant way. The evidence for the integrity of the deflation pavement, and by default the underlying Pleistocene sediments, has been critical in eliminating the possibility that stone artefacts may have been introduced to the Pleistocene unit from more recent levels. Importantly, the OSL data, the archaeological and environmental evidence as well as the stratigraphic data from the 1997 excavations, support an interpretation of an intact record of megafauna and people in the lead up to the LGM (Field & Dodson 1999; Field et al. in press; cf. Roberts et al. 2001)

Acknowledgements. Excavations were funded by an ARC Large Project Grant and the Australian Museum and facilitated by the Brewarrina Local Aboriginal Land Council, the Johnstone, Green and Currey families and many volunteers especially Leanne Brass, Megan Mebberson, Harry Webber and Agnes Dubost. Thank you to Richard Cosgrove for comments and Andrew Wilson for FIGURE 2. We are also grateful to Miralwyn Cotton and the Walgett Shire Council for assistance. Field was the recipient of an ARC Postdoctoral Fellowship and a University of Sydney U2000 Postdoctoral Fellowship while undertaking this project.

TABLE 1. Radiocarbon and OSL determinations for the Cuddie Springs
sequence. The sediment facies are also shown.

sediment facies AL/SU radiocarbon age * lab. no.

surface AL6 1470 [+ or -] 70 Beta 81,385
 SU1

undifferentiated clays AL5 14,820 [+ or -] 70 Beta 81,376
 SU2-4 5,590 [+ or -] 60 Beta 81,375
 19,270 [+ or -] 320 Beta 44,374

deflation pavement AL4 28,770 [+ or -] 300 Beta 81,377
 SU5

clay/silts AL2&3 32,900 [+ or -] 510 Beta 81,378
 SU6a 28,310 [+ or -] 200 Beta 46,170
 33,660 [+ or -] 530 Beta 81,379
 30,280 [+ or -] 450 Beta 44,375

structured clays AL1 33,300 [+ or -] 530 Beta 81,379
 SU6b 30,990 [+ or -] 360 Beta 81,380
 32,580 [+ or -] 510 Beta 81,382
 29,570 [+ or -] 280 Beta 46,171
 32,420 [+ or -] 460 Beta 81,383
 29,170 [+ or -] 360 Beta 81,384

beach lag deposit SU7

sediment facies OSL age lab no.

surface

undifferentiated clays 16,700 [+ or -] 1200 #

deflation pavement 27,000 [+ or -] 2000 #

clay/silts 30,000 [+ or -] 2000 #

structured clays 36,000 [+ or -] 3000 #
 35,400 [+ or -] 2800 [ANU.sub.OD]118a

beach lag deposit >36,000 years not dated

* dates are presented in stratigraphic order; # data obtained from
Roberts et al. (2001).

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Received 22 November 2000, accepted 28 June 2001, revised 29 August 2001