Longtan Fm

Conformable contact with the sandy shale or siltstone on the top of the underlying Yanqiao Fm,

Conformable contact with the black shale and siliceous shale of the overlying Dalong Fm. But in portions of South China, there is an intervening Talung Fm that spans the Changhsingian interval.

Distributed in the southern and southeastern parts of Hunan Province, the southern part of Anhui Province, the southern part of Jiangsu Province, and the northern part of Zhejiang Province. The typical stratigraphic sequence for the Longtan Fm described above occurs in the southern and eastern parts of Jiangsu Province and in the southern part of Anhui Province. In the southern part of Hubei Province the thickness of the Longtan Fm is only of several meters, and being composed largely of siltstone. In the southeastern part of Hubei Province the formation is composed mainly of fine-grained sandstone and siltstone, intercalated with two coal layers, with a thickness of 40-70 m. The Limestone Member is otherwise known as the Xiayao Fm. Eastward to the southwestern part of Jiangsu Province and the northern part of Zhejiang Province, the thickness of the Sandstone Member of the Longtan Fm reaches as much as of 40-70 m; with the Coal-bearing Member being intercalated with 2-3 layers of sandy limestones and 6-10 layers of coal; the Limestone Member is composed of sandy limestone and ammonoid-bearing sandy siltstone and pure siltstone, with a thickness of 40-80 m. Its top part represents the Upper Coal-bearing Member, which is composed of fine-grained sandstone, siltstone and siltstone, intercalated with coal seams, with a thickness of 40-70 m.