Dalakongma Fm
Type Locality and Naming
The type section is about 70 km south of Bangkog, Tibet, from Duojiagunba to Dalakongma of Dêqên District. It was named by Han Tonglin in 1983.
Lithology and Thickness
Siltstone, Volcanic ash, and Clayey Limestone. The formation is a suite of clastic and carbonate rocks from a littoral-neritic setting. Lower part consists of gray-green−purple tuffaceous, calcareous and clayey siltstones, and gray−gray-white tuffaceous feldspar and quartzose sandstone, intercalated with green tuffaceous siltstone, having large ripple marks and worm trails (?). Upper part is dominated by gray and gray-green bioclastic limestones and organic marls, intercalated with gray-green tuffaceous bioclastic marl and moderately-fine metamorphic sandstone. Total is over 640 m thick.
Relationships and Distribution
Lower contact
Unknown: at the type section, it is in faulted contact with the underlying stratum. Next older regional unit is the Cobuza Fm
Upper contact
Unknown: at the type section, it is in faulted contact with the overlying Boqu Fm, Dêqên Gr of Upper Jurassic.
Regional extent
GeoJSON
Fossils
Lower part contains Coral Tachylasma sp., and Brachiopods Syringothyris sp., Rotaia sp. and Productus sp. Upper part yields Coral Tachylasma sp., and Brachiopods ?Choristites sp., Reticularia sp., Brachythyrina sp., Composita sp. and Martinia sp.,
Age
Depositional setting
It is interpreted as littoral-neritic sediments
Additional Information