Abstract:

The Qaidam Basin,situated at the intersection of the Palaeo-Asian and Tethys-Himalaya tectonic domains,exhibits a unique basin-mountain structural pattern. Its well-developed Cenozoic strata preserve continuous sedimentary records spanning from the early Cenozoic to the Quaternary period. Late Pleistocene sediments comprise four lithofacies types: gravel,sand,clay,and evaporite layers. Gravel and sand layers dominate the basin’s margins(1 to 45m thick),while clay and evaporite layers(150 and 300m thick)prevail in the basin center. Based on lithological,biological,climatic,event,and age classification and correlation,the late Pleistocene strata are subdivided into five genetic sedimentary types: diluvial,alluvial,fluvial,lacustrine,and chemical deposition. Through comprehensive analysis of 56 boreholes and outcrop profiles,the late Pleistocene sedimentary facies of the Qaidam Basin have been thoroughly studied. The results indicate five distinct sedimentary facies types: alluvial fan,braided river,lacustrine delta,freshwater lake,and saline lake. Braided river facies are primarily distributed in areas such as Alar,Utumeiren,Dagele,Xialiha,and Huaitoutala. Similarly,significant changes in braided river or river delta facies are observed along the northern margin of the basin,while minimal changes occur along the southern margin. Triggered by the Gonghe Movement,the unified Qaidam paleolake disintegrated into multiple isolated small lake basins. In these isolated basins,such as Dalangtan,Chahan Slatu,Kunteyi,and Mahai,rapid brine concentration led to the deposition of shore-shallow saline lake subfacies. The Yiliping area also exhibits shore-shallow saline lake subfacies,whereas the main bodies of the Qarhan and Da Qaidam areas maintained freshwater and brackish lacustrine environments. Gahai Lake,Keluk Lake,and Tuosu Lake formed a unified freshwater lake system.

Key words: lithofacies palaeogeography, Late Pleistocene, Qaidam Basin

摘要： 柴达木盆地地处古亚洲构造域和特提斯—喜马拉雅构造域的结合部,具有特殊的盆-山构造格局,盆地内新生代地层非常发育,保存了从新生代早期至第四纪之间连续、完整的沉积记录。柴达木盆地晚更新世沉积物分为砾石层、砂层、黏土层和盐岩层4大类,盆地边部以砾石层、砂层为主,厚度1~45 m;盆地中心以黏土层、盐岩层为主,厚度150~300 m。本次工作在对比56个钻孔、露头剖面资料基础上,对柴达木盆地晚更新世岩相古地理进行综合研究。结果表明: 柴达木盆地晚更新世发育冲积扇相、辫状河相、湖泊三角洲相、淡水湖相、咸水湖相5类沉积相和15类沉积亚相; 盆地边缘发育冲积扇相,辫状河相主要分布于阿拉尔、乌图美仁、大格勒、夏日哈、怀头塔拉等地区,辫状河相或河流三角洲相在盆地北缘面积变化明显,南缘变化不大。受共和运动的影响,柴达木古湖被完全肢解成彼此互不相连的多个小湖泊,大浪滩、察汗斯拉图、昆特依和马海等孤立湖盆的湖水急剧浓缩,为盐湖滨浅湖亚相沉积,一里坪地区为盐湖滨浅湖亚相,察尔汗、大柴旦地区主体仍为淡水—微咸水湖泊,尕海、可鲁克湖、托素湖为一个统一的淡水湖。

关键词: 岩相古地理, 晚更新世, 柴达木盆地

CLC Number: 

• P531