Liangshan Fm
Type Locality and Naming
The type section is located in the Liangshan Mt. of the Nanzheng County, Shaanxi Province. It was named by Zhao Yazeng, T.K. Huang (Huang Jiqing) in 1931.
Lithology and Thickness
Claystone, Soil/Coal, and Sandstone. The Lower part of a typical stratigraphic sequence is habitually called an aluminum-bearing rock series, which is composed of grey massive plant-rhizome-bearing clay rocks, intercalated sometimes with carbonaceous shale, with its base commonly representing a layer of chlorite trihydrallite or Lingula-bearing variegated hydromica-shale which has transversally changed facially to bauxite (ores). The Middle part is habitually known as a carbonaceous layer, being composed largely of black carbonaceous shale, intercalated locally with poor-quality coal. The Upper part is composed of dark-grey shale, intercalated commonly with thin-bedded siliceous rocks, sandstone and limestone lenses. The claystones are commonly possessed of dense and massive structure, silt-, and pebble-rank inner-clastic structure, and oolitic structure. Among the clay minerals, it is the illite that predominates. Another stratigraphic sequence consists chiefly of yellow-grey and grey-white medium- and thin-bedded quartz-siltstone and quartz-fine-grained sandstone both cemented by siliceous substance, intercalated with dark-grey and grey-black brachiopod fossil-yielding shale and a small amount of carbonaceous shale and coal seams. The basal part of the formation is composed mainly of clay rocks, yielding continental plants, with a thickness commonly of 40-100 m, and sometimes of over 200 m.
Relationships and Distribution
Lower contact
Disconformable contact with the underlying Maping Fm of the Lower Permian Series for the "another stratigraphic sequence". Disconformable, or a conformable contact with the underlying strata, or in an unconformable contact with the underlying Carboniferous System through the Cambrian System for the "type sequence"
Upper contact
Conformable contact with the overlying Qixia Fm
Regional extent
The typical stratigraphic sequence of the formation is distributed along the Xikang-Yunnan (Xikang-Yunnan), Yangtze, South Changqiang and Xuefeng Oldland areas, with a thickness commonly of 10 m, sometimes of over 20 m. The Middle part of the formation very often contains a coal layer, which is mineable locally, with its basal part commonly containing mineable bauxite and clay mineralizations. The coastal-beach barrier-bar facies stratigraphic sequence is distributed in the Zhaotong, Huize, Bijie, Shuicheng, Weining and Fuyuan areas on the eastern side of the Xikang-Yunnan (Kam-Yunnan) Oldland, with a thickness commonly of tens of meters, and sometimes of over 200 m, containing 3-6 layers of coal. In such surrounding areas of the Xuefeng Uplift as the West Hubei, West Hunan, Northeast Guizhou, the thickness of the formation is of 10 to over 40 m.
GeoJSON
Fossils
The variegated shale on the base of the formation commonly contains phosphorous substances, yielding occasionally sludge-cutting lower-rank brachiopods, with its top part yielding abundant brachiopods, bivalves and Ostracoda fossils.
Age
Depositional setting
The "typical sequence" has soil horizons, and the "another stratigraphic sequence" is a coastal beach barrier-bar facies.
Additional Information
GeoJSON estimate by Can Cai and Xinyi Zhang (Chengdu Univ. Tech. students)