Ganchaigou Fm
Type Locality and Naming
Qaidam Basin. The naming section is located at Ganchaigou in the Qaidam basin, Qinghai. The strata were originally named by the Research Institute of the Qinghai Petroleum Administration as the Ganchaigou rock series in 1959 and renamed by Pei Wenzhong et al. as the Ganchaigou Formation in 1963.
Lithology and Thickness
Mainly grayish green, yellowish green and purplish red sandstone, oil-bearing sandstone, calcareous shale and sandy mudstone, with conglomerate, marlstone and pebbly sandstone lenses and locally with oil accumulations. The thickness is 1526 m.
Relationships and Distribution
Lower contact
It has a locally unconformably or conformable contact with the underlying Paleogene Lulehe Fm.
Upper contact
It has a conformable contact with the overlying Neogene Youshashan Fm.
Regional extent
The formation shows relatively great lateral change. It is thicker in the west and east and becomes thinner in the central part. In the vicinity of Changweitai and Qingmingshan the rocks become fine and conglomerate decreases, and the thickness is 899 m; in Da Qaidam and Xiao Qaidam the thickness is 226 m.
GeoJSON
Fossils
The formation yields ostracods represented by the Hemicyprinotus-Candoniella-Ilyocypris assemblage, Charophytes represented by the Maedlerisphaera-Hornichara assemblage, Plants such as Populus, Phyllites, etc. and gastropods; in addition, there are four sporopollen assemblages.
Age
Depositional setting
This formation is predominantly of lacustrine facies and subordinately of fluvial and piedmont facies.
Additional Information