Lajiangshan Fm
Type Locality and Naming
The Lajiangshan Formation was erected by the Comprehensive Geological Prospecting Brigade of the Xizang Bureau of Geology and Mineral Resources in 1979. The section for the designation in Pengriarnongba-Takaxiagei of the Lajiangshan Town of the Baingoin County, Xizang (90°10′E; 30°30′N).
Lithology and Thickness
Lower part of the formation is represented by purple red and gray green medium and coarse-grained sandstone, siltstone and mudstone intercalated with calcareous mudstone and tuffaceous sandstone, constituting rhythms. Upper part is gray green and purple red conglomerate, gravel-bearing sandstone, fine and coarse-grained sandstone and siltstone. The thickness of the formation is over 950 m.
Relationships and Distribution
Lower contact
The base of the formation marked by dark purple and purple red conglomerate with break red sandstone lies unconformably on the underlying volcanics of the Wuoronggou Fm (Woronggou Fm) that consists of variegated tuffaceous sandstone and conglomerate. Regionally, the next younger unit is the Tithonian-Berriasian Qusumpo Fm sandy claystone.
Upper contact
The top of the formation marked marked by purple red sandstone and conglomerate lies conformably below the gray white sandstone with limestone of the overlying Xizhashan Fm,
Regional extent
The present formation is mainly distributed in Deqing, Lajiangshan and on the northern side of Namucuo of the Baingoin County. It is persistent in lithology.
GeoJSON
Fossils
None listed
Age
Depositional setting
Additional Information