【摘要】 目前,锆石定年技术被广泛应用于盆地演化恢复重建中。通过对柴达木盆地北缘(柴北缘)关键变形期地层——上侏罗统进行地层序列、沉积环境、碎屑锆石定年等研究,深入探讨了燕山晚期—喜马拉雅早期的柴北缘的时空演化格局。多个证据表明,中晚侏罗世,祁连山开始隆升,整个柴北缘处于弱挤压的环境之下,构造属性发生了反转。①祁连山前的绿草沟以及团鱼山的野外露头表明,上侏罗统为一套干旱环境下的辫状河、滨浅湖体系的沉积序列,与中侏罗统差异较大;②地震剖面及野外露头中,上侏罗统与上下地层为角度不整合或平行不整合接触;③绿草沟及团鱼山的上侏罗统粗砂岩锆石U-Pb年代学分析结果表明,2个地区的上侏罗统具有相似的年龄谱特征,锆石年龄介于2 800～222Ma之间,其中,团鱼山样品的碎屑锆石年龄分别为242～226Ma,峰值年龄为242Ma;414～255Ma,峰值年龄为383Ma;964～559Ma,峰值年龄为559Ma;1 515～1 125Ma,峰值年龄为1 130Ma;2 437～1 746Ma,峰值年龄为1 960Ma,通过与周边物源区年龄谱的对比,上侏罗统的主要物源区为南祁连地区,与中侏罗统的年龄相比,上侏罗统碎屑锆石年龄表现出反序剥蚀的特征。弱挤压环境下形成的中上侏罗统之间的不整合面,是油气运移的高效通道,上侏罗统岩性圈闭是下一步油气勘探的主要方向。更多还原

【Abstract】 At present,zircon dating technology is widely used in basin evolution and reconstruction.On the research of the stratigraphic sequence,sedimentary environment and source analysis of the Upper Jurassic that is the critical deformation period of the northern margin of Qaidam Basin,the spatial and temporal evolution pattern of the north margin of Qaidam Basin in late Yanshan-early Xishan period was discussed.Several evidences show that during the Middle and Late Jurassic,the Qilian Mountains began to uplift,and the whole north margin of the Qilian mountains was in a weak compression environment.The tectonic properties were reversed.The Lvcaogou and the Tuanyu mountains field outcrops show that the Upper Jurassic is a series of sedimentary sequences of braided river and shallow lake system in arid environment,which is quite different from the Middle Jurassic strata.In seismic section and field outcrop,the Upper Jurassic was in angular unconformity or parallel unconformity contact with the upper and lower strata.The zircon U-Pb chronological analysis of the Upper Jurassic coarse sandstone in Lvcaogou and Tuanyu Mountains shows that the Upper Jurassic has similar age spectrum characteristics.The zircon age is between 2 800 and 222 Ma.The age distribution of detrital zircons in Tuanyushan one of tue Upper Jurassic samples is 242-226 Ma with main peak of 242 Ma,414-255 Ma with main peak of 383 Ma,964-559 Ma with main peak of 559 Ma,1 515-1 125 Ma with main peak of 1 130 Ma,2 437-1 746 Ma with main peak of1 960 Ma.Compared with the age spectrum of the peripheral provenance area,the main provenance area of the Upper Jurassic is the South Qilian area.Compared with the Middle Jurassic age,the detrital zircon age of the Upper Jurassic is characterized by reverse sequence denudation.The unconformity between the Middle and Upper Jurassic formed in the weak compressional environment is an efficient channel for oil and gas migration,and the lithologic trap of the Upper Jurassic is a main direction for oil and gas exploration in the next step.更多还原