四川广安谢家槽下三叠统碳酸盐微相及沉积环境

EARLY TRIASSIC CARBONATE MICROFACIES AND SEDIMENTARY ENVIRONMENTS OF THE XIEJIACAO SECTION AT GUANGAN,SICHUAN

依据碳酸盐岩的颗粒组分及结构构造特点,四川广安谢家槽剖面下三叠统夜郎组和嘉陵江组的碳酸盐岩可以划分出5个主要的微相类型和15个次一级的微相类型。在微相分析的基础上,结合岩性及构造特点,划分出台地边缘、开放海台地、局限海台地和蒸发台地4种主要的沉积相带,由夜郎组、嘉陵江组向上到雷口坡组构成从局限海台地逐渐演变为蒸发台地相,反映了该地区从早三叠世到中三叠世海水逐渐变浅、碳酸盐台地逐渐向蒸发台地总的演变历程。

According to our study of their grains, textures and structures, the limestones of the Early Triassic Yelang and Jialingjiang formations in the Xiejiacao Section of Guangan, Sichuan can be divided into five main microfacies types and fifteen second order ones. On this basis too, their sedimentary environments can be assigned to： I . plat-form margin; II. open marine platform; III. restricted marine platform; IV. platform evaporites. The sedimentary environments swiftly changed into platform evaporites from the end phase of the Early Triassic Jialingjiang Formation into the succeeding Middle Triassic Leikoupo Formation. In general the changes of depositional environments through the Lower and into the Middle Triassic refleet a continuing regressive sequence in the region.