Mianxian Gr
Type Locality and Naming
It was named by Zhao Yazeng, Huang Jiqing as the “Mianxian System” in 1931. The naming section is located in the Yanhe River valley 5 km north of the Mianxian County town, Sha’anxi Province.
Synonym: （沔县群）. It is known as the Longjiagou Fm at the Longjia Gully of Wudu County, with its lithology being consistent.
Lithology and Thickness
Composed of sandstones and conglomerates, intercalated with coal beds. Lower part consists mainly of dark-grey and black shales, siltstones and grey sandstones, intercalated with coal beds and seams, with its basalt part representing 10 m thick variegated conglomerates, being of 93 m thick. Middle part of the group is composed largely of dark-grey and grey poststones (= fine-grained sandstone), siltstones, grey-white and variegated conglomerates, intercalated with shales, with a thickness of 246 m. Upper part of the group is composed of multicycles of deposition of grey sandy conglomerates, conglomerates, yellow-grey and grey-brown poststones, siltstones and shales, with a thickness of 552 m.
Relationships and Distribution
Lower contact
The group overlies unconformably the Early Paleozoic Baishui Gr. Regionally, it is in false conformable contact onto the Houlaomiao Gr of late Triassic.
Upper contact
Regional extent
The group is distributed in the Dangchang, Zhouqu, Lixian, Wudu, Liangdang, Fengxian and Mianxian Counties in the West Qinling Mts region.
GeoJSON
Fossils
It yields plant fossils such as Neocalamites carcinoides, Cladophlebis whitbyenssis, Coniopteris hymenophylloides, Pityophyllum startatschini, Pterophyllum aequale, Ctenis chinenesis and Podozamites lanceolatus, as well as bivalve fossils.
Age
Depositional setting
Additional Information