Yanghugou Fm
Type Locality and Naming
The type section is located in the Yanghugou coal mine, 5−6 km southwest of Yanghugou, Shandan County, Gansu. It was named by Grabau in 1924.
Lithology and Thickness
Sandstone, Siltstone and Limestone. Lower member consists of gray-white quartz grit, and the top with gray-black shale and sandy shale intercalated with thin coal seams, thin-bedded limestone and siderite nodules, 34.4 m thick. Middle member is formed by interbeds of soil-gray calcareous siltstone, black shale and limestone, intercalated with thin coal streaks, 47.5 m thick. Upper member is dominated by gray and black moderately thick-bedded limestones, intercalated with shale and chert, 41 m thick.
In the west part there are plenty of limestone interbeds, which decrease toward the east. It is 517 m thick around the Tongxin slope of Ningxia, and the thinnest is only 18 m in the areas of Sunan and Qilian of Gansu.
Relationships and Distribution
Lower contact
Conformable contact with the underlying Hongtuwa Fm
Upper contact
Disconformable contact with the overlying Early Permian Liuhuanggou Fm [Not in Permian Lexicon set]
Regional extent
Distributed in the east segment of Hexi Corridor and the areas from Shandan and Jingtai of Gansu to Zhongwei of Ningxia; also scattered in the areas such as Qilian and Sunan in the west segment of north slope of the Qilian Mts. The most complete sequences occur at Heishan of the Alxa Left Banner of Inner Mongolia, Xiaoyuchuan of Zhongwei of Ningxia and the Yushuliang-Hongtuwa section of Jingyuan of Gansu.
GeoJSON
Fossils
The Lower member contains Ammonoids Gastrioceras weristerence and G. (Lissogastriceras) fittsi, which correspond to the early G2 zone of the Westphalian (Western Europe); the Fusulinid Profusulinella paranibelensis zone; Conodonts Idiognathodus delicatus, I. sinuatus, Neoganthodus symmetricus, etc. At Yanghugou of Shandan, there are multiple limestone interbeds, yielding Fusulinid Fusulina cylindrica.
Age
Depositional setting
Additional Information