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.