Late Cenozoic Chemical Weathering and Environmental Changes Recorded in the Co Ngoin Sediments, Central Qinghai-Tibet Pl
A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In this paper, we present the weathering history and paleoclimatic changes in the last 2.8 Ma based on studies of high-resolution temporal distributions of Sr, Rb and Zr concentrations, Rb/Sr and Zr/Rb ratios and δ 13C and TOC for the Co Ngoin sediments, in combination with the sediment properties, grain size distribution and clay mineralogy. The sedimentary records indicate three environmental stages in the last 2.8 Ma. At the core depth of 197-170 m (about 2.8-2.5 Ma), low-intensity chemical weathering in the Co Ngoin catchment was experienced under warm-dry to cool-wet climate conditions with relatively low Sr concentration and high Rb/Sr and Zr/Rb ratios. The sudden occurrence of both subalpine coniferous forest and coarse sand and gravel sediments in the Co Ngoin core reflects a strong tectonic uplift. The high Sr concentrations and low Rb/Sr and Zr/Rb ratios reflect a relatively strong chemical weathering between 2.5 Ma and 0.8 Ma (at the core depth of 170-38.5m) under a temperate/cool and wet climate, characterized by mud and silt with fine sand, probably indicating a stable process of denudation and planation of the plateau. Above the depth of 38.5 m (about 0.8-0 Ma), the coarsening of sediments indicates a strong tectonic uplift and a relatively low intensity of chemical weathering as supported by the record of sediments having relatively low Sr concentrations and high Rb/Sr and Zr/Rb ratios. Since then, the plateau has taken the shape of the modern topographic pattern above 4000 m a.s.1.
作 者： Chen Shiyue JIN Zhangdong WANG Sumin SHEN Ji 作者单位： Chen Shiyue(Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing,Jiangsu 210008;School of Environment and Planning,Liaocheng University,Liaocheng,Shandong 252059)JIN Zhangdong(Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing,Jiangsu 210008;Institute of Earth Environment,Chinese Academy of Sciences,Xi'an,Shaanxi 710075)
WANG Sumin,SHEN Ji(Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing,Jiangsu 210008)
刊 名： 地质学报（英文版） SCI 英文刊名： ACTA GEOLOGICA SINICA 年，卷(期)： 2005 79(3) 分类号： P5 关键词： Qinghai-Tibet Plateau Co Ngoin Rb/Sr Zr/Rb δ 13C TOC environmental evolution