四川盆地西部晚三叠世海相碳酸盐岩—碎屑岩的转换过程

The Late Triassic transition from marine carbonate rock to clastics in the western Sichuan Basin

通过对上三叠统马鞍塘组及其生物礁的分布特征、岩相特征、古生物特征和物源区等的研究,认为上三叠统海相碳酸盐岩—碎屑岩的转换过程约束了马鞍塘组生物礁的发育范围和绝灭时间。川西海相碎屑岩物源主要来自北面的秦岭地区,在时间上从卡尼期开始到结束经历从无到有,从少到多的碎屑注入过程,在空间上经历了从北向南的扩展过程。揭示出龙门山造山带的形成与崛起具有从北到南的递进过程,并受控于秦岭造山带的形成和演化。这个转变过程是四川叠合盆地构造演化的一个关键点,它约束了马鞍塘组海相烃源岩的发育和生物礁发育序列。近川中地区地腹中可能有马鞍塘组高能礁体发育,值得油气勘探关注。

Based on study of the features of distribution,lithofacies and palaeontology of the Upper Triassic Maantang Fm.and its bioherm as well as their provenience,this paper suggests that the distribution area and extinction of the bioherms in the Maantang Fm.be controlled by the Late Triassic transition from marine carbonates to marine clastics.The clastics of the marine strata in western Sichuan Basin were mainly sourced from the northern Qinlin area.The clastic input beginning in the Carnian increased in amount progressively and spread from north to south.It is indicated that the formation and uplifting of Longmen Mountain is a progressive process from north to south and is controlled by the formation and evolution of Qinling orogenic zone.The transition is critical to the structural evolution of the superimposed Sichuan Basin and constrained the development of marine source rocks in the Maantang Fm and the development sequence of the bioherms.The Maantang Fm is worthy of further exploration as high energy reefs might have developed in areas near the central Sichuan Basin.