四川盆地西部晚三叠世早期地层及其沉积环境

四川盆地西部晚三叠世地层发育,层位齐全,最厚达三千余米。但晚三叠世早期(卡尼期)地层,分布比较局限。1959年全国第一届地层会议上,把朱森(1942)创立的天井山灰岩作为卡尼阶。因未发现重要化石,许多单位把天井山灰岩划归拉丁阶,与贵州法郎组对比,认为普遍缺失中、晚三叠世之间的地层。

THE EARLIER LATE TRIASSIC SEQUENCE AND ITS SEDIMENTARY ENVIRONMENT IN WESTERN SICHUAN BASIN

The Ma'antang formation was found in Jiangyou County,Sichuan province as early as 1973.Based on its fossils such as Ammonite,Conodont,Bivalvia,Foraminifera and Sporo-pollen collected and studied in recent years,the writers refer it to the earlier Late Triassic,that is Carnian stage.Its lithofacies and fossilassemblages are described here in detail.This formation is distributed over Jiangyou,Mianzhu,Shifang,Emei,and Yanting regions.At the beginning of this stage,the transgression of Tethys sea came from Aba and Garze areas,and reached the western part of the basin.A series of carbonate rocks deposited there.At the middle and later stages,the sea extended towards the south-east and clastics took place in the area of Anyue.In this way,the western part of Sichuan basin comprised the eastern shelf of Aba-Garze sea.