Malasongduo Fm
Type Locality and Naming
The type section is located at Randa, Chaya County, Tibet Autonomous Region. It was named by Yang Qingshan in 1983.
Synonym:
Lithology and Thickness
It is a set of clastic, volcanic and pyroclastic rock. From bottom to top, there are three members: Lower member is black-gray sandy shale, intercalated with thin limestone and muddy limestone. Slate and marble are locally present. The total thickness of the lower part is about 1500 m. Middle member is composed of a set of gray white rhyolite, green-gray dacite rhyolite with sandy shale and cinerite with a thickness of 600 m. Upper member is dominated by gray-black shale, quartzose sandstone, gray-white thick laminar rhyolite, cinerite and tuffaceous breccia, about 419 m thick.
Relationships and Distribution
Lower contact
It is disconformable in contact to the underlying Carboniferous-Permian limestone.
Upper contact
Regionally, the next younger unit is the Xiariduo Fm of Anisian.
Regional extent
It is well-developed in Changdu county and extends southward to Malasongduo area in Chaya County and Zongxi, Laoran area in Mangkang county with a distribution in the range of about 200 km long and 20 km to tens of kilometers wide. Coeval with the Jiazhila Fm in nearby region.
GeoJSON
Fossils
Fossils are rare, only bivalves: Claraia sp., Gervillia cf. pannonica, Promyalina intermedia, P. subtrigona, Posidonia sp., Pteria cf. murchisoni in the upper part of this formation.
Age
Depositional setting
It is interpreted as marine volcanic-sedimentary rocks.
Additional Information