塔里木盆地寒武纪构造-沉积环境与原型盆地演化

摘要

The Cambrian carbonate is the objective exploration strata in the Tarim Basin recently,and the restoration of the proto-type basins is the foundation for the research of the tectonic evolution and petroleum exploration.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 Cambrian tectonic-depositional environment of the Tarim Basin and established the models of basin fill processes,by employing the method of "point→line→face".The Cambrian of the Tarim Basin underwent a complete transgressive-regressive cycle which consisted of two secondary cycles which are the rapid transgression in the early of the Early Cambrian→the regression in the Middle Cambrian and the slow transgression in the Late Cambrian→the regression at the end of the Cambrian.The two secondary cycles responded to the two stages of sedimentary evolution,respectively:the Taxi intra-cratonic depression experienced the evolution from the clastic onshore facies-open shelf facies in the Early Cambrian→the restricted platform facies in the Early Cambrian→the evaporative platform facies in the Middle Cambrian and the restricted platform facies in the Late Cambrian→the exposed unconformity at the end of the Cambrian;the Tadong cratonic margin depression developed the basin facies and underwent the lithofacies evolution from the siliceous mudstone→the limestone thinly interbedded with clay-silt rock→the carbonate rock.The characteristics and evolution of the Cambrian proto-type basins of the Tarim Basin were controlled by the extension of the Rodinia supercontinent and the tectonic-depositional pattern of the Tarim Basin experienced the transition from the pattern of the end of the Sinian which was differentiated from north to south to the pattern of the Middle-Late Cambrian which was differentiated from west to east.%寒武系是塔里木盆地当前油气增储上产的重点层系,恢复寒武纪的盆地原型是油气勘探的重要基础.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,恢复了塔里木盆地寒武纪不同时期的构造-沉积环境,并建立了相应的盆地充填演化模式.塔里木盆地寒武纪经历了一次完整的海侵-海退旋回,包括早寒武世早期快速海侵→中寒武世海退、晚寒武世缓慢海侵→寒武纪末海退两个次级旋回,分别对应沉积演化的2个阶段:塔西克拉通内坳陷早寒武世的碎屑滨岸-陆棚相→局限台地相→中寒武世的蒸发台地相,晚寒武世的局限台地相→寒武纪末期的台地暴露不整合;塔东克拉通边缘坳陷为深水盆地相,经历了硅质泥岩→泥岩与灰岩薄互层→碳酸盐岩的岩相演化.寒武纪塔里木原型盆地特征及演化主要受控于Rodinia超大陆的裂解,其构造-沉积格局经历了由震旦纪末的南北分异格局向中-晚寒武世的东西分异格局的演变.