基于ESR测年的泥河湾早更新世遗址和地层年代序列研究

The accurate age of archaeological sites is the basis for Quaternary geology and paleoanthropology research. Due to the lack of isotope precise dating materials in the Nihewan Basin sediment, previously dating mainly rely on magnetic stratigraphy. However, because of the complex fluvial deposition process and the limitations of paleomagnetic method, it is not enough to be based solely on the geomagnetic polarity reversal boundaries and insert with average deposition rate to estimate sites strata ages, especially for ancient human sites that located far away from the geomagnetic pole translation boundary. Thus, the independent chronological study of the basin sedimentary strata and the ancient human sites are particularly important. The current study is based on the previous theory and preliminary application of ESR dating in Quaternary sediment supported by Youth Fund of NSFC. Combined with paleomagnetism, stratigraphy, sedimentary geology, we plan to use ESR method to date ten important archaeological sites which are far away from the geomagnetic polarity transition boundaries and some sedimentary strata on two profile sections which have integrated strata and clear sedimentary sequence in the Nihewan Basin This will provide independent ESR ages of the main sites and some important sedimentary strata, which will supplement and improve the Nihewan basin chronostratigraphy framework and to build independent age sequence of ancient human sites.

泥河湾盆地因富含早期人类遗址而备受关注，这些遗址的精确年代是第四纪地质学、古人类学等领域的基础科学问题之一。泥河湾盆地沉积物因缺乏同位素精准定年物质，此前的遗址定年工作主要依赖磁性地层学方法。但由于复杂的湖相沉积过程及古地磁法自身的局限性，仅依据地磁极性倒转界限和平均沉积速率内插估计获得的遗址地层年龄是不够的，特别是对所处地层远离地磁极性转换界线的重要古人类遗址。因此，有必要对盆地沉积地层和古人类遗址进行系统的独立年代学研究。本申请拟在青年基金取得的理论与实践应用成果上，以ESR测年法为主要手段，结合已有古地磁学、地层学、沉积地质学等资料，对泥河湾盆地早期人类遗址（尤其是远离地磁极性转换界限的遗址），以及地层发育完整、沉积序列清楚的两个剖面，进行详细的石英ESR年代测定，以期获得泥河湾盆地重要遗址和地层层位的ESR独立年龄，补充和完善泥河湾盆地年代地层学框架及其古人类遗址的独立年代序列。

本项目利用石英ESR测年法对泥河湾盆地内小长梁、山神庙咀、半山、马圈沟I、马圈沟II、马圈沟Ⅲ、飞梁等多处古人类遗址以及郝家台剖面的多个重要地层界限（Jaramillo正极性亚时顶、Cobb Mt. 漂移事件和Bjorn漂移事件之间、Gilsa漂移事件、Olduvai正极性亚时顶）进行了独立年代学研究，并给出了其形成的独立年代，补充和完善了泥河湾层的年代地层学框架，建立了泥河湾盆地早期人类遗址的ESR独立年代序列。.同时，因泥河湾层部分层位样品颗粒较细（＜100 μm），无法提取常规的（100-200 μm）ESR测年样品，本项目通过对已知年龄样品的不同粒径组分（50-100 μm，100-150 μm，150-200 μm，200-300 μm和300-450 μm）年龄的对比研究，建立了细颗粒石英ESR测年流程及方法，为细颗粒沉积物测年提供了重要手段。.此外，近年来随着野外便携式gamma谱仪的出现，环境剂量的野外就地测量也容易操作实现了。部分学者认为，野外实地测量的环境剂量比室内的更加准确，而更倾向于使用野外便携式gamma谱仪获得被测样品的环境剂量。因此，本项目增加了野外就地环境剂量测量和室内环境剂量测量的对比研究，为今后石英ESR测年研究中的环境剂量测定提供了重要依据。.在本项目资助下，已取得成果8项，其中发表文章6篇（SCI收录5篇，核心期刊收录1篇），专利1项，获奖1项。