Mailonggang Gr
Type Locality and Naming
The type section is located in Mailonggang, Linzhou County, Tibet and named by Tibet Lazi Geological Survey Brigade in 1962.
Synonym: The original "Wheat Longgang" group represents a set of limestone near Tibet Lhasa, clastic rock and volcanic rock strata, age were identified as the late Triassic to team to Tibet area in 1979 changed its name to "Wheat Longgang" group, at the same time period in late Triassic to Jurassic in 1983 Wang Naiwen reclassify the meaning of "Wheat Longgang" group, such as the limited to late Triassic Marine fossils.
Lithology and Thickness
It is mainly composed of carbonate clastic rocks and volcanic rocks, and can be divided into three parts from bottom to top: Lower part is interbedded limestone and argillaceous limestone. Middle part is interbedded with quartz sandstone and shale. Upper part is tuffaceous sandstone interbedded with andesite. Thickness is 1787~1895 m.
Relationships and Distribution
Lower contact
No bottom is seen. Within the outcrop range, it is in contact with the underlying strata by faults. Next older regional unit is the Chaqupu Gr of volcanic tuff.
Upper contact
No top is seen. Within the outcrop range, it is in contact with the overlying strata by faults. Next younger regional unit is the middle Jurassic Quesangwenquan Fm sandstones.
Regional extent
GeoJSON
Fossils
There are abundant fossils of the family Procycloitidae, as well as brachiopods and gastropods of hydrozoa and conodonts. Important bivalves include Halobia cf. beyrichi, Nuculana yunnanensis, and Costatoria sp. etc. The top can be divided into four conodont zones: Epigondolella multidentata zone; E. postera zone; E. bidentata zone.
Age
Depositional setting
Marine facies
Additional Information