印度河扇近海盆地沉积演化特征

Sedimentary evolution characteristics of offshore Indus river fan basin

印度河扇近海盆地位于印度板块西缘,其深水区是当今国际油气勘探的热点区域。基于二维地震测线、钻井、商业数据库和公开发表的文献资料,本文对印度河扇近海盆地的沉积演化特征进行了研究,结果表明,印度河扇近海盆地为裂谷型被动大陆边缘盆地,基底之上发育晚白垩世以来的沉积序列,其中晚白垩世末期—早古新世推测处于裂陷阶段,发生大规模岩浆喷发,形成喷发玄武岩相;晚古新世—始新世处于热沉降阶段,构造趋于稳定,主要为碳酸盐岩台地、生物礁及半深海沉积;渐新世—全新世为被动大陆边缘阶段,受板块碰撞、喜马拉雅山隆升及海平面下降的影响,发育大型海底扇沉积,以大规模的水道-堤岸沉积体系为特征。该盆地的形成及演化受控于印度板块的向北漂移、印度板块与欧亚板块的碰撞、海平面下降等事件。

The offshore Indus river fan basin is located at the western margin of Indian Plate,and its deepwater area is one of the hot spots of international oil and gas exploration.Based on2D seismic data,drilling,commercial database and published articles found in literature,the sedimentary evolution characteristics of the offshore Indus river fan basin are studied in this paper.Study results show that the offshore Indus river fan basin is a rift type passive continental margin basin developed with sedimentary sequences since the late cretaceous on the top of its basement.During late Cretaceous and early Paleocene Epochs the basin was in the chasmic stage and experienced a major magmatic eruption which formed the eruptive facies of basalts;during late Paleocene and Eocene Epochs,it was in the thermal precipitation stage in which the structures became stable and the depositions were mainly the carbonate platform,reef and semi-deep sedimentary.During Oligocene and Holocene Epochs it was in the passive continental margin stage in which it was developed with large scale of submarine fan depositions due to influences of plates collision,uplift of Himalayas and sea level falling,and was characterized by large scale of water channel and levee system depositions.The formation and evolution of the basin were controlled by the northward drift of India Plate,collision between the India Plate and Eurasia Plate,and sea level falling.