Dameigou Fm

It was named by Wang Wantong and others in 1960, and was first cited publicly by the Compiler

Jingeng Sha (coordinator) Group for the Regional Stratigraphic Chart of Qinghai Province in 1980. The naming locality is situated at Dameigou 80 km to the east of Taglagan, Qinghai Province.

Synonym: （大煤沟组）

The formation is composed of sandstone and shale, intercalated with coal beds, and is divisible into three members. Lower part of the Lower member being composed mainly of grey sandstone, grey-black claystone and carbonaceous shale, with its basal part consisting of grey-white thick-bedded pebble-bearing sandstone, and with its upper part consisting of alternation of grey-green sandstone with purple mudstone and siltstone, with a thickness of 300 m. Middle member is composed essentially of grey-green and grey-white pebble-bearing sandstones, gradating upwards into grey claystone and black carbonaceous shale, intercalated with coal beds (26 m thick) while approaching to the top part of it, with a thickness of 265 m. Upper member, with its lower part consisting largely of grey, grey-green and grey-yellow fine-grained sandstones, siltstones and claystones, intercalated with gritstones and micro-conglomerate, and the upper part of which is composed of brown and black shales and oil shales, with a thickness of 248 m, with its basal part serving as a layer of grey-white pebble-bearing quartz-sandstone.

All the above-mentioned members are found to yield plant fossils, main members of which are Coniopteris hymenophylloides, C. burejensis, Cladophlebis suluktensis, Raphaelia diamensis, Eboracia lobifolia, Ginkgo cf. whitbiensis, Gonatosorus lobifolius and Pityophyllum sp., as well as Chareae fossils Aclistochara lufengensis, A. yunnanensis; Conchostracans Qaidamestheria dameigouensis, etc.; and Ostracods as represented by Darwinula sarytirmenensis.