广西早更新世巨猿地点的ESR/U-系结合法定年研究

The Gigantopithecus blacki is the largest species of primates, and the single extinct ape during the Pleistocene. Up to date, there are more than ten Gigantopithecus fauna localities known in the southern China, where uncovered numerous Gigantopithecus blacki fossils and coexisted mammalian fossils, associated with cultural relics of early humans. These archeological findings have significant implications for the studies of the Quaternary mammal evolution, human origin and environmental changes. However,dating of these Gigantopithecus fauna localities is a long-lasting challenge. In this programme, we are planning to use the method of combined ESR/U-series dating of fossil teeth to study the geochronology of the Mohui cave, the Chuifeng cave and the Sanhe cave, which are the recently discovered the Early Pleistocene Gigantopithecus fauna localities in Guangxi Province. Considered the possibility of U-leaching occurred during burial period for a small number of samples, we are going to develop new U-uptake model for ESR dating of the fossil teeth to overcome the limits of the present combined ESR/U-series dating method, which is not applicable to the samples with 238U-234U-230Th system beyond secular equilibrium.Through this programme, we will be able to yield directly dated ages for the Mohui cave, the Chuifeng cave and the Sanhe cave. These results will contribute to establishing a chronological framework of the Gigantopithecus faunas. Additionally, this research will also provide experiences for the dating of other Gigantopithecus localities.

我国华南地区已发现10多处步氏巨猿化石地点，出土了三个巨猿下颌骨和上千枚巨猿牙齿以及丰富的伴生动物化石和文化遗存。这些材料对研究第四纪哺乳动物演化，人类起源以及环境变迁有重要意义。然而测定这些巨猿地点的地质年代一直是科学难题，如今多数地点没有绝对测年数据。本项目拟选择新近发现的广西早更新世巨猿地点么会洞、吹风洞和三合大洞为研究对象，用电子自旋共振与铀系结合测年方法(ESR/U-系结合法)，以伴生哺乳动物牙化石为样品，研究这三个巨猿动物群的地质年代。针对少数牙化石样品可能发生U-淋失问题，本项目将发展新的U-吸附模型以克服目前ESR/U-系结合测年法不能用于238U-234U-230Th系统超越放射性衰变平衡的局限性。通过开展本项目，我们将获得么会洞、吹风洞和三合大洞巨猿动物群的直接测定的地质年代，为建立巨猿动物群的年代框架积累测年数据，同时也为开展其他巨猿地点的定年研究打下基础。

华南的第四纪喀斯特洞穴堆积含有丰富的哺乳动物群化石，其中以步氏巨猿(Gigantopithecus blacki)为代表的巨猿动物群化石一直备受学术界关注。本项目采用牙化石ESR/U-系结合测年法测定广西田东吹风洞和么会洞以及广西崇左三合大洞动物群的地质年代。牙化石ESR/U-系结合测年法是将牙化石样品的ESR分析(古剂量和年剂量)与U-系分析(U-Th同位素)相结合用来模拟牙齿各个组织在地质时期的U-吸附过程，以计算牙组织中的U对古剂量的贡献，因此ESR/U-系年代比常规ESR年代更准确。项目测定了11个大型哺乳动物牙化石的ESR/U-系年代，结果表明吹风洞和么会洞动物群的地质年代在误差范围内一致，为1.97~1.38Ma；三合大洞动物群的地质年代为早更新世晚期至中更新世之初，910~600ka。这些研究结果为建立巨猿动物群的起源和演化的年代框架提供了绝对测年数据。