Qusumpo Fm
Type Locality and Naming
It was named by the Petroleum Prospecting Party of Qinghai Province under the former Ministry of Geology as the Qusumpo Rock Series in 1957. The naming section is located at Konglong Sunguo-Longmala area of Duoba region, Bange County, Tibet (E 89°45′, N 31°25′).
Synonym: （曲松波组）
Lithology and Thickness
Lower part of the formation represents grey and grey-black shales, siltstones, quartz-sandstones and conglomerates, containing andesite lenses, with the shales containing concretions and being rich in ammonites fossils, and with the carbonaceous shales yielding plant fossils. Upper part of the formation represents an alternating layer of variegated conglomerates, sandstones, siltstones and shales, yielding a small amount of Foraminifera fossils. It is 2000 m in thickness.
Relationships and Distribution
Lower contact
Its basal part with grey and grey-black concretion-bearing shales is in an unconformable contact onto the limestone of the underlying lower Permian Xiala Fm (Perm column 48). Regionally, there is a Late Jurassic volcanic unit of the Woronggou Fm (about 1 degree further south).
Upper contact
Not given. Regionally, the next younger unit is the dark-violet and purple conglomerate and sandstone of the Lajiangshan Fm (mid-Early Cretaceous).
Regional extent
The formation is distributed in the Duoba region of Bange County and the Xiongmei region of Shenza County, with a consistent lithology and a changeable thickness in a range from 2000 m to 2500 m.
GeoJSON
Fossils
In the Duoba region the formation yields such ammonites as Himalayites sp., Kilianella sp. and Neocomites sp.; plant fossils as represented by Zamiophyllum sp.; as well as Foraminifera fossils such as Orbitolina sp. and etc.
Age
Depositional setting
Additional Information