塔里木盆地晚奥陶世构造-沉积环境与原型盆地演化

摘要

塔里木盆地晚奥陶世构造-沉积环境经历了快速而剧烈的变化,恢复该时期盆地原型有助于揭示盆地充填演化和盆山耦合.利用最新的钻井、地震及露头资料以沉积相为研究实体,将盆地充填与周缘构造演化相结合,由点→线→面进行分析,恢复了塔里木盆地晚奥陶世不同时期(以组为单位)的构造-沉积环境,并建立了相应的盆地充填演化和盆山耦合样式.吐木休克组沉积期,塔里木盆地西部发育淹没台地-深水台盆沉积体系,巴楚塔中和塘南为暴露剥蚀区;良里塔格组沉积期,盆地西部发育开阔台地-深水台盆沉积体系,其中玉北东部-塘古巴斯碳酸盐岩台盆反转为浊流盆地;桑塔木组沉积期,盆地西部发育混积陆棚-浊流盆地沉积体系,仅在柯坪发育欠补偿沉积;铁热克阿瓦提组沉积期,盆地西部广大地区为暴露剥蚀区,并发育碎屑滨岸-陆棚沉积体系.吐木休克组-桑塔木组沉积期,塔里本盆地东部持续发育深水浊流沉积体系;铁热克阿瓦提组沉积期,演变为碎屑陆棚沉积体系.研究认为塔里木盆地晚奥陶世在东西分异的台-盆格局基础上叠加了南北分异的隆-坳格局:吐木休克组沉积期,盆地西部差异升降显著,南北向隆-坳榴间的格局初步形成;良里塔格组-桑塔木组沉积期,盆地发生整体的沉降与充填,沉积格局由西厚东薄反转为东厚西薄;铁热克阿瓦提组沉积期,盆地南部和北部发生强烈隆升,古地理格局具南北陆中间海的特征,南北向隆-坳相间的格局定型.在塔里木地块与南部岛弧耦合作用不断加强的背景下,大量陆源碎屑的注入和盆内差异升降作用使得晚奥陶世构造-沉积环境发生了快速变迁.奥陶纪未,在南北双向挤压背景下,大规模的海退和盆内物源区的出现使得塔里木盆地结束了震旦纪以来碳酸盐岩大面积发育的历史,标志着盆地演化进入一个新的阶段.%The tectonic-depositional environment of the Tarim Basin underwent a rapid and dramatic change in the Late Ordovician.The restoration of the proto-type basins has a great significance for the reveal of the basin-mountain coupling and basin fill process.Based on the newest data of drillings,seismic profiles and outcrops,with the analysis of sedimentary facies and the combination of basins and orogenic belts,this paper reconstructed the Late Ordovician tectonic-depositional environment of the Tarim Basin and established the models of basin-mountain couplings and basin fill processes,by employing the method of "point→line→face".In the Tumuxiuke Formation stage,the inundated platform-deep water basin sedimentary system was developed in the western part of the Tarim Basin,and the Bachu-Tazhong area was denudated;In the Lianglitage Formation stage,the open platform deep water basin sedimentary system was developed and the Yudong-Tanggubasi area underwent the transition from the carbonate basin to the turbidite basin;in the Sangtamu Formation stage,the mixed shelf deposit-turbidite basin sedimentary system was developed and the under-filling deposit was only developed in the Kalpin;In the Tierekeawati Formation stage,the shore-shelf sedimentary system was developed.In the Tumuxiuke Formation-Sangtamu Formation stages,the turbidite basin sedimentary system was continually developed in the eastern part of the Tarim Basin;In the Tierekeawati Formation stage,the clastic shelf sedimentary system was developed in this area.The tectonic-depositional pattern of Tarim Basin in the Late Ordovician had the feature as the following:the platform-basin pattern differentiated from east to west was overlaid with the uplift-depression pattern differentiated from north to south.In the Tumuxiuke Formation stage,the unified platform in the west of the basin had broken down leading to the development of uplift-depression pattern differentiated from north to south.In the Lianglitage Formation-Sangtamu Formation stages,the subsidence and deposition fill occurred overall the basin,the depression died out making the depocenter reversed.In the Tierekeawati Formation stage,the northern and southern part of basin uplifted severely and became land,only the middle part of the basin was covered by water,marking the formation of the uplift-depression pattern differentiated from north to south.Under the background that the coupling between basins and orogenic belts increasingly strengthened,the injection of large terrigenous clastics and the up and down of topography made tectonic-depositional environment change rapidly.At the end of the Ordovician,with the sea level descended drastically and the emergence of provenance basin within the basin,the Tarim Basin terminated the history that carbonate sediment grew extensively,signing that basin evolution entered into a new stage.