Abstract: There exists a succession of shallow-water,thick-bedded carbonate sediments a few hundred meters thickabove the Middle Triassic Sanbao’ao Formation in southeastern Hunan. In respect to the sedimentary sequence,lithology and lithofacies ,this succession ls different from the Yangjia Group in the Pingxiang-Shangrao area of cen-tral Jiangxi to its east and also notably distinct from the Baifeng and Hekou formation in central Guangxi to itswest,whereas vertically it is entirely different from its underlying Sanbao’ an Formation too;so in this paper it isnamed the “Shijing Formation”and used to represent a transition type of east-directed transformation from activesediments to stable sediments in the Nanhua sea basin in the early and middle parts of the Middle Triassic.