摘要： 根据野外露头剖面,结合区域地质资料,对塔里木盆地乌什凹陷西部的石炭系—二叠系沉积演化进行了分析。乌什凹陷西部在石炭纪夹于南天山残留海盆地和柯坪—温宿隆起之间,其地层和沉积与塔里木盆地内部有较大差异。早石炭世早期,本区为碎屑岩和碳酸盐岩混积的浅海陆棚环境,以索格当他乌断裂为界,早期的柯坪—温宿隆起控制了该时期的沉积作用。早石炭世晚期,本区首次海侵,早期的柯坪—温宿隆起部分被淹没,并伴随着强烈的构造沉降,形成半深水斜坡环境,沉积了一套以库鲁组和索格当他乌组为代表的近端—远端浊积扇的复理石沉积,并一直持续到晚石炭世早期。晚石炭世晚期,本区又一次规模较大的海侵,柯坪—温宿隆起大部分被淹没,原隆起区为开阔海台地环境,北部和西部边缘发育典型的台地边缘相生物礁,向北延伸可达乌什北的克孜布拉克地区,再向北为礁前斜坡和浅海陆棚环境,并持续到中二叠世早期。中二叠世以后,伴随周缘地区大规模的陆内火山喷发,该区发生大规模海退。晚二叠世末,随着塔里木板块与中天山地块的拼合以及海西期天山造山带的形成,南天山洋消失,结束了海相沉积,进入了陆相沉积阶段。

关键词: 石炭系—, 二叠系, 沉积演化, 乌什凹陷, 塔里木盆地

Abstract: Based on the outcrop profile and regional geological data,the sedimentary evolution of Carboniferous-Permian in western Wushi sag was investigated. The Carboniferous western Wushi sag is located between the southern Tianshan residual sea basin and Keping-Wensu uplift,and is quite different from that of the inner Tarim Basin. During the early stage of Early Carboniferous,as the boundary of Suogedangtawu Fault in the northern margin of Keping-Wensu uplift controlling the sedimentation,there were shallow shelf environment that was dominated by shore littoral and diamictic carbonate. During the late stage of Early Carboniferous,the first marine-flooding made Keping-Wensu uplift partially submerged,which was accompanied by a strong subsidence,forming bathyal slope environment. The flysch deposition of the proximal-distal turbidite fan typified by Kulu Formation and Suogedangtawu Formation are seen to occur within such bathyal slope environment,and continued until the early stage of Late Carboniferous. During the late stage of Late Carboniferous,another large-scale transgression occurred in this area,which,in turn,made Keping-Wensu uplift mostly submerged. The original uplift,then shifted to the open platform environments. Typical platform margin reef were well developed in the north and west edge of the study area,and northward extended to Kezibulake area,outward to the reef front slope and shallow shelf environment,which was continued until the early stage of Middle Permian. After the Middle Permian,due to the large-scale intracontinental volcano activity,large-scale regression developed in this area. At the end of the Late Permian,accompanied by the combination of Tarim Plate and Middle Tianshan Massif,the South Tianshan Ocean disappeared and formed the ancient Tianshan orogenic belt of the Hercynian period. This completely ended the marine sediments and entered the stage of continental deposition. In addition to the Carboniferous shoreline facies sandstones,the reef limestone reservoirs of the Early-Middle Permian were widely distributed,the buried depth of the reservoirs is relatively shallow and the physical properties are relatively good,giving rise to an important target for oil and gas exploration.

Key words: Carboniferous-Permian, sedimentary evolution, Wushi sag, Tarim Basin

中图分类号: 

• P512.2