Dating the northernmost evidence of Gigantopithecus by combined ESR and U-series method.

Gigantopithecus was a giant ape once lived in Southeast Asia and China during the Pleistocene period. Longgupo and Jianshi Longgudong sites in West-Hubei and Three Gorges region in South China are the northernmost evidences of Gigantopithecus presence in the world up to date. To obtain the detailed chronology of these two sites, paleomagnetic and radiometric dating methods were attempted, including cosmogenic burial dating of the sediment. However, the efforts failed because of the scarce of quartz minerals in the sediment. Combined electron spin resonance and uranium series (ESR/U-series) method which could date the fossil teeth directly with the age range from Early to Late Pleistocene was also applied and the results obtained at Longgupo site already published. Here, we report the first radiometric dating results for teeth carried out from Jianshi Longgudong Western Branch cave which is renowned for the discovery of both Gigantopithecus fossils and undoubted stone artifacts. The main challenge of dating Jianshi Longgudong site is the reconstruction of external dose rate of the fossil samples where their provenance sections were not preserved. The mean radioelement concentrations in the sediments measured in the laboratory with different water content estimation were initially used to calculate the ESR/U-series ages. Our ESR/U-series dating of two mammalian fossil teeth from the lower layer 8 gives a weight mean age of 1512 ± 94 ka, while a mean age of 1044 ± 53 ka was obtained for two teeth from the upper layer 4. These ages support one of the previous paleomagnetic dating interpretation which propose that the hominin fossil layer in Jianshi site was not older than 1.78 Ma, i.e. that the upper boundary of the Olduvai subchron, and are in agreement with the faunal evidence which suggest that Jianshi site is younger than the adjacent Longgupo site dated also by combined ESR/U-series and paleomagnetic methods to 2.0-2.5 Ma. Further study of the site including the radiometric dating study of the fossil layers preserved in the Eastern Branch cave may help to achieve a definitive conclusion of the chronology of Gigantopithecus settlement in Jianshi Longgudong site. [ABSTRACT FROM AUTHOR]