| 摘要: |
| 柴达木盆地东部三湖地区早更新世湖相沉积层中,阶段性地发育了具季节性韵律层理的钙质泥岩和泥灰岩。组构、粒度、矿物成分、氧碳同位素及沉积相等研究表明:这是一种成因上与湖水年季节性分层相关的非冰川碎屑纹泥。冬季泥质层中粘土矿物和泥晶碳酸盐矿物的混合沉积呼应于总体气候干旱背景。纹泥的发育与大幅度湖侵的同步性反映了区域构造运动对湖相纹泥形成的宏观控制;纹泥的物质组成、厚度等差异则指示了细微的环境变化。 |
| 关键词: 非冰川碎屑纹泥 柴达木盆地 早更新世 |
| DOI：10.18307/1995.0302 |
| 分类号: |
| 基金项目: |
|
| Preliminary study on nonglacial varved sediments of early pleistocene lake in Qaidam Basin |
|
Wang Yongjin
|
|
Geography Deportment of Nanjing Normal University, Nanjing 210024
|
| Abstract: |
| The Weil Sezhong 6 core from Sebei Gas Field in the three-lake area in East Qaidam Basin contains 870m-long section of continuous lacustrine deposits during Early Pleistocene. The characteristics of varved sediments in the part of deep lacus have been recognized by observations of the core. Varved sediments are thinly laminated and made up of alternately dark clay and light silty layers of average 0.75mm thick. The varves could be subdivided into three kinds of couplets:1) silt-clay couplets; 2) organism-bearing clay and silt couplets; 3) marl layer and silty intraclastic couplets. Data of size analysis can be interpreted as the results of suspension setting in deep lake for both coarser silty layer and clayey layer of varves. δ18O and δ13C of the different types of varved sediments show that lake water in Early Pleistocene was of relatively high salinity and seasonally stratified. Varved sediments were deposited in lake transgression sequence related to the regional subsidence of the basin. The depositional sequences of varved sediments could be classified into stable and fluctuated lake level sequences according to the associations of microfacies. Therefore, it can be concluded that the varves axe nonglaciaJ clastic, differing remarkably from glacial varves. The genesis of the varves is further discussed. The deposition of the varves depends mainly upon annually seasonal stratified water column and influx forms, both of which have been controlled by tectonic subsidence of the basin and climatic changes. Carbonates in the varves are considered to be genetically related to arid climate condition during Eariy Pleistocence in this area. Finally, the varved sediments play an important part in environmental reconstruction, i. e.:1) depth of the lake water; 2) changes of supply amount; 3) fluctuation of lake levels; 4) changes of paleoclimates. |
| Key words: Nonglacial clastic varve Qaidam Basin Early Pleistocene |
