等时线Al-26/Be-10埋藏测年法研究西侯度等重要早期人类遗址的年代

Based on the results achieved when carrying out our previous projects from National Natural Science Foundation of China, the present proposal aims at studying the chronology of key Early Pleistocene hominin sites in China with recently established isochron Al-26/Be-10 burial dating. If the Al-26 and Be-10 concentrations of a set of coeval quartz samples, preferably quartzite gravels, can be fitted into an isochron by least square regression, the samples' burial age can be derived from its slope. If the quartz samples conform to the model of "simple steady-state erosion", and they are sufficiently shielded from cosmic rays to ignore post-burial production of cosmogenic nuclides, the resultant isochron should pass the origin of the coordinate plane and the age derived from its slope should be consistent within errors with the weighted mean of the individual burial ages. The positive case can be cited as firm evidence in support of the reliability of the results of burial dating. In case of failure to obtain an isochron with reasonable precision, at least part of the samples fails to conform to the preconditions of burial dating. .The present project will give priority to the Paleolithic site of Xihoudu in Ruicheng County, Shanxi Province, where preliminary burial dates of ~2 Ma have been obtained, and to hominin/Paleolithic site of Longgupo in Wushan County, Chongqing Municipality, where systematic excavations are currently under way. The hominin site of Yuanmou in Yuanmou County, Yunnan Province, and the Paleolithic sites of Yulong Park in Chongqing Municipality and Ganlian in Tiandong County, Guangxi Zhuang Autonomous Region are selected as its alternative targets. .It is expected that robust temporal frames for Xihoudu and several other key Early Pleistocene hominin sites in China may come out by carrying out this project. This will mark a substantial progress in studying the earliest hominin appearance in China, and provide firm chronological evidence for addressing whether or not the first human population in China was as early as ~2 Ma. Moreover, the results of this project may possibly lead to changes in the patterns of human evolution, and bear importance to relevant science disciplines as well.

本项目拟用新近建立的等时线Al-26/Be-10埋藏测年法研究我国重要早更新世人类遗址的年代。将同一层位多个石英矿物样Al-26、Be-10浓度拟合成等时线，从其斜率可解得样品的埋藏年代。若一组样品符合"简单恒态侵蚀模式"，埋深足以忽略后期生成的宇生核素，所得等时线应过坐标原点，且其斜率和单个样品给出的年代应在误差范围内一致。如是，应是年代结果可信的有力证据。若难以获得精度合理的等时线，则至少部分样品不满足埋藏测年的前提条件。本课题研究重点为已有初步埋藏测年数据的山西芮城西侯度和正在进行系统发掘的重庆巫山龙骨坡，云南元谋上那蚌、重庆玉龙公园和广西田东甘莲等地点列为候补。预本课题可给出西侯度等重要早期人类遗址可信的年代界限，为确立约2 Ma前人类是否已出现在中国提供坚实的年代学证据，这将是对我国人类最早起源研究的重要贡献，有可能导致人类起源和演化理论的重要修正，对相关学科的研究亦具重要意义。

等时线技术数年前被引入 26Al/10Be 埋藏测年，这一地质年代测定新技术可鉴别并剔除个别经历复杂埋藏史的样品，也可在很大程度上规避因埋深不足后期宇生核素生成的干扰，埋藏测年法因此可跻身独立、可信的第四纪同位素地质年代测定法之列。本课题在上二个国家基金研究成果的基础上，用等时线 26Al/10Be 埋藏测年法重点研究旧石器时代早期遗址山西芮城西侯度的年代，所获结果 (2.47 ± 0.07 Ma) 表明，该地点是我国乃至欧亚大陆最早的石器地点，人类在中国出现应比原认为的早得多。尽管数度冲击高层次国际期刊未果，且现已在一定程度上被人“弯道超车”，但埋藏测年数据坚实，西侯度石制品确信无疑出土于地层，其人工性质无可非议。假以时日，这一成果的重要性终将为学界广泛接受，并将较大幅度改写人类最早起源、迁移和演化的理论模型。此外本课题还研究了湖北郧县曲远河口 (郧县人遗址)、陕西蓝田公王岭 (蓝田人遗址)、河北阳原马圈沟等其他重要早期人类遗址的埋藏年代，探索了云南元谋上那蚌 (元谋人遗址) 和广西田东高岭坡等地点埋藏测年的可行性，并基于次生碳酸盐岩铀系测年研究了湖北郧西黄龙洞、广东韶关狮子岩 (马坝人化石地点)、云浮蟠龙洞等中、晚更新世洞穴人类遗址。已在国际期刊发表论文 6 篇，预近 1-2 年还将有多篇论文发表。本课题成果对古人类、旧石器时代考古、古生物和第四纪地质、地貌及其相关学科的研究有重要意义。