柴达木盆地新生界湖盆咸化特征及沉积响应

柴达木盆地新生界发育咸化湖盆沉积,但是对于湖盆的咸化程度一直没有详细论述,其沉积响应特征亦不清楚。文中利用系统测试得到的硼元素及黏土矿物资料来开展古水体盐度恢复,结果表明:(1)柴达木盆地新生界为咸化湖盆沉积,最高盐度大于20‰;(2)不同盐度地区的沉积响应特征不同,其中陆源碎屑物供给区古盐度小于12‰,滨浅湖区古盐度在10‰~18‰之间,半深湖区古盐度大于18‰。在中高咸化湖盆水介质的控制作用下,沉积物分布表现为单层厚度小(一般为1~3m)、砂/泥岩互层频繁、三角洲沉积相带分布较窄、细粒沉积物分布范围较广、发育特有湖相碳酸盐岩和膏盐岩及与陆源细碎屑呈混积等特征。

Palaeosalinity characteristics and its sedimentary response to the Cenozoic salt-water lacustrine deposition in Qaidam Basin

The salt￣water lacustrine deposition was developed during the Cenozoic in Qaidam Basin,but its salinity and sedimentary response have not been known. Based on boron and clay mineral data,palaeosalinities of the Cenozoic in Qaidam Basin were reconstructed by Couch formula,which testified that: (1) The Cenozoic sediments belonged to the salt￣water lacustrine deposition with the maximum salinity over 20‰. (2) The zones with different palaeosalinities had different sedimentary responses,that is,the palaeosalinity values of terrigenous clastics supplying areas were commonly less than 12‰,while those of shore-shallow lake ranged from 10‰ to 18‰,and those of semi-deep lake exceeded 18‰. Under the control of salt￣water with middle to high salinity, the salt water lacustrine deposition in Qaidam Basin has the following characteristics: single layer is thin usually with 1-3 m thickness, sand layer and mud layer are frequently interbedded, delta sedimentary facies belt is relatively narrow, fine grained sediments are distributed in a wide range, and typical lacustrine carbonate rocks, gypsum and terrestrial fine detritus are mixed.