Jiadengda Fm
Type Locality and Naming
The type section is located at Maqingpo-Jiadainong, the south of Jiadengda, Qinghai Province. It was named by Ma Baofu, Wang Xiulin and Che Yi in 1984. This formation was originally the coal-bearing clastic rock group in the upper part of the Jiezha Gr. Uppermost formation in Jiezha Gr.
Synonym:
Lithology and Thickness
The section mainly consists of clastic rocks. Lower member is dominated by gray, dark gray fine and siltstone, intercalated with argillaceous siltstone and shale, with a thickness of 963m. Upper member is composed of feldspar quartz sandstone, with quartz sandstone intercalated with siltstone and argillaceous siltstone, with a thickness of 800 m.
Relationships and Distribution
Lower contact
The yellow-brown calcareous sandstone at the bottom is in conformable contact with the limestone and bioclastic limestone on the top of the underlying Xiaoqiacuo Fm. Not peaked.
Upper contact
Initial entry said "conformable with Batang Gr of Jurassic", but Batang Gr entry implies it is largely coeval Late Triassic (TJ32 column). Therefore, the next younger regional unit is the Middle Jurassic base of the Qoimaco Fm (Yanshiping Gr); with apparent absence of Lower Jurassic?
Regional extent
This group is mainly distributed in the middle and lower reaches of Ziqu River and south of Duocai in Qinghai Province. From Duoduodeng to the east, it is widely developed in Xiao Sumang and eastern Tibet.
GeoJSON
Fossils
Ammonoids: Cyrtopleurites sp., Pinacoceras sp., Paratibetites sp., Proarcestes sp., Pseudosirenites cf. elegans, Bivalves: Halobia qinghaiensis, H. cf. superbecens, Pteria sp., Costatoria mansuyi, Brachiopods: Zedleria lingulata, Oxycoipella zhidoensis, Rhaetinopsis zadoensis, Plants: Neocalamites hoerensis.
Age
Depositional setting
It is interpreted as mainly marine deposits, with interbedded continental deposits.
Additional Information