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The Lancefield Swamp is a rich fossil deposit from the Pleistocene epoch was discovered in the 19th century near Lancefield, Victoria, Australia. ==Description== The site consists of a bone bed lying directly atop a layer of fluvial gravel between layers of clay.〔Gillespie R. et al. "Lancefield Swamp and the Extinction of the Australian Megafauna", ''Science'' 200, 1978, 1044-8.〕 The layer of bones is estimated to contain the remains of perhaps 10,000 individual Pleistocene animals.〔 A total of at least 6 Megafauna species are represented, although the majority of bones are from ''Macropus giganteus'' or ''Macropus titan''. Human artifacts were found in the bone bed and in the overlying clay. However, evidence of reworking by water flow has been noted.〔 Thus it appears possible such artifacts are intrusions. The Lancefield Swamp fossil site is important in the debate over the time of and causes of the extinction of Australian Megafauna. Humans are estimated to have arrived in Pleistocene Australia, or Sahul, at anything from 60 ka to about 45 ka. Initial radiocarbon dates yielded estimates of 31ka, a comparatively young age approaching the Last Glacial Maximum. Horton therefore claimed Lancefield as a decisive example of the survival of Australian Megafauna for many thousands of years after the arrival of modern humans in prehistoric Sahul.〔Horton D. ''The Pure State of Nature'', Allen & Unwin, Sydney 2000.〕 But when Lancefield Swamp was investigated by van Huet, it was found that the bones had indeed been reworked by fast flowing water at some time after the animals had died.〔van Huet S. "The Taphonomy of the Lancefield Swamp Megafaunal Accumulation, Lancefield, Victoria". ''Records of the Western Australian Museum'', supplement 57, 331-340, 1999.〕 This conclusion was based upon observations that the bones show signs of post-depositional wear, that they are all disarticulated, that complete skulls are lacking,〔 that the majority of bones are large and that they tend to be aligned along a common axis indicative of the direction of water flow. It thus appeared probable that lighter bones had been washed away whereas heavier bones remained in situ. Dating of Diprotodon teeth〔van Huet S. et al. "Age of the Lancefield Megafauna: a reappraisal". ''Australian Archaeology'', 46, 1998.〕 from the bone bed yielded ages of 46-56 ka by means of ESR and a minimum of 32 ka by means of Carbon-14. However, as result of excavations begun in 2004, Dortch et al. suggest that the Lancefield Megafauna remains have not in fact been disturbed since deposition.〔(Dortch 2004:Formal Report )〕 Thus it is hoped that dates assigned to the Lancefield bones are reliable and therefore represent their true age since burial. If age estimates turn out to be on the high side, say 60ka or greater, the Lancefield bones may contribute little to our understanding of the effects of human activities upon the Australian Megafauna since such an age would pre-date the arrival of modern humans in Sahul by a wide margin. On the other hand, if the dates are comparatively recent, say less than 35 ka, then humans would be exculpated as the causative agent. If however the estimate falls somewhere close to 46ka then human arrival and the final demise of the Megafauna would appear to be closely associated. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lancefield Swamp」の詳細全文を読む スポンサード リンク
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