Xiaomeigou Fm
Type Locality and Naming
It was named by Yang Fan, Di Hengshu in 1972, and was first cited publicly by the Compiler
Jingeng Sha (coordinator) Group for the Regional Stratigraphic Chart of Qinghai Province in 1980. The naming section is located in the area extending from the Xiaomeigou Gully to the Dameigou Gully about 80 km east of the Taglagan, Qinghai Province.
Synonym: （小煤沟组）
Lithology and Thickness
Lower part is composed largely of grey-yellow, yellow-green and purple conglomerate, sandy conglomerate and pebble-bearing gritstone, intercalated with a small amount of grey and grey-black siltstone, claystone and carbonaceous shale, containing basal conglomerate with a thickness of 29 m. Middle part is grey-yellow, yellowish-pink and grey-white sandstone, siltstone and pebble-bearing sandstone, intercalated with a small amount of claystone and a thick coal layer (11.6 m thick), with a thickness of 89 m. Upper part is mainly of brown-black and grey-black oil shale and shale, intercalated with grey and grey-yellow fine-grained sandstone, siltstone, medium- and coarse-grained sandstones and coal seams, with a thickness of 82 m. The total thickness is 200 m.
Relationships and Distribution
Lower contact
It overlies unconformably the paleo-Proterozoic Kendaban Gr in type region; but regionally, the next older unit is the upper Triassic Galedesi Fm (uppermost formation in Mole Gr).
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Dameigou Fm
Regional extent
The formation is known so far to be distributed only in the Xiaomeigou Gully area on the northern margin of the Chaidamu Basin.
GeoJSON
Fossils
The lower, middle and upper parts of the formation are found to yield plant fossils key members of which comprise Neocalamites carcinoides, N. nathorsti, Cladophlebis ingens, Cl. nebbensis, Cl. denticulate, Todites williamsoni, Hausmannia ussuriensis, Ginkgoites ferganensis, Pityophyllum longifolium, Czekanowskia elegans and etc.
Age
Depositional setting
Additional Information
Age:
Schematic stratigraphic column assigns as Early Jurassic.
Age span:
Beginning stage: Hettangian
Fraction up in beginning stage: 0.0
Beginning date (Ma):
Ending stage: Toarcian
Fraction up in ending stage: 1.0
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information
Compiler
Jingeng Sha (coordinator)