基于阶地暴露年龄的青藏高原东南缘第四纪构造隆升历史重建

It is tectonically active in the southeastern margin of the Tibetan Plateau since the late Cenozoic. Until now there are few studies have concerned the details of the Quaternary tectonic. The widely developed river terraces in this area are ideal for tectonic study. Because of the geological features, the traditional dating methods are difficult to apply. However, cosmogenic nuclides can be used to directly date geomorphic surface, which has a good prospect especially in terrace dating. This project select two terraces from the Jinsha River and Nu River respectively for dating using Be-10 or Cl-36 method according to lithology. The terrace exposure ages will be gained through the measuring results analysis and evaluation. That will provide useful guidance for future application. Meanwhile, the tectonic uplift stages of different regions will be calculated by combining the terrace ages with the measured relief geometry suing DGPS(Differential Global Positioning System). Then reconstructing the Quaternary tectonic history of the southeastern margin of the Tibetan Plateau, which will provide scientific basis for understanding the dynamical process and mechanism of the Tibet Plateau uplift.

青藏高原东南缘是晚新生代以来构造运动活跃地区，对于其第四纪以来的构造活动细节至今仍缺乏深入研究。该地区广泛发育的河流阶地是研究构造活动的理想媒介，然而其地质构造特点使得传统测年方法难以适用。宇宙成因核素测年方法能够直接用于地貌面的定年，尤其在阶地测年中具有良好的应用前景。本项目分别在金沙江和怒江流域南北地区各选择2个阶地序列，根据不同阶地的岩性特征应用宇宙成因核素Be-10和Cl-36进行测年。通过对结果的分析评价得到较可靠的阶地暴露年龄，并为今后的相关应用提供有益指导。同时结合差分GPS对阶地面的精确测量结果与所得阶地年代序列，计算出不同区域不同时段的构造抬升速率，进而重建青藏高原东南缘第四纪以来构造活动历史，为理解青藏高原隆升的详细过程及其动力学机制提供科学依据。

青藏高原东南缘是晚新生代以来构造运动活跃地区，然而第四纪以来的构造活动细节至今仍缺乏深入研究。通过在金沙江和怒江中段分别选取2个典型河流阶地序列开展宇宙成因核素定年研究，获得了两个流域的阶地序列年代，且具有很好的一致性。结合研究区阶地的构造成因，重建了中更新世晚期以来构造隆升的细节，其隆升速率分别为：3.2ka以来约为4.1m/ka、3.2～13.2ka约为2.6m/ka、13.2～55.3ka约为0.9m/ka、55.3～89.2ka约为1.8m/ka、89.2～185.7ka约为0.3m/ka。