柴达木盆地西部新生代砂岩碎屑组分变化记录的沉积转型事件

Cenozoic sedimentary transformation event record by detrital components in western Qaidam basin,Qinghai,China

应用砂岩碎屑成分分析法对柴达木盆地西部干柴沟地区新生代地层进行了系统的物源分析。砂岩组分镜下鉴定和含量统计分析结果表明,研究区内砂岩类型以长石砂岩和岩屑长石砂岩为主,岩屑类型以沉积岩岩屑为主。镜下识别出一些标志性的矿物和岩屑,它们的出现及其含量在剖面垂向上的变化,指示柴达木盆地西部干柴沟地区上干柴沟组与下油砂山组界线附近的沉积物源发生了明显变化,说明柴达木盆地西部地区在渐新世与中新世之交约20Ma时发生了一次重大的沉积转型事件。这次沉积事件在青藏高原北部其他地区也可以找到一系列踪迹和响应,是探索青藏高原北缘构造隆升历史的一个重要界线。

We＇ve adopted sandstone detrital component analysis in Cenozoic strata of Ganchaigou area,western Qaidam basin,to analyze the provenance systematically.The microscopic identification and content statistics results of the sandstone components showed that the major types of sandstone are arkose and lithic arkose,and sedimentary rock debris is main in this area.Some signature minerals and debris are identified from sandstone components.The appearance of these special minerals and debris and its content vertical change on section indicated that the sedimentary provenance changed obviously near the boundary of upper Ganchaigou and lower Youshashan formations,implied a sedimentary transformation event occurred at the transformation era from Oligocene to Miocene,which happened at about 20Ma ago,in western Qaidam basin.This event was also supported by a series of evidence in other areas of northern Qinghai-Tibet Plateau.It is an important clue to study the tectonic uplift history of the northern margin of Qinghai-Tibet Plateau.