Dongka Fm
Type Locality and Naming
Chen Bingwei and Ai Changxing were named in 1983. The named section is located in the north of Alashi, Jiangda County, Tibet.
Synonym:
Lithology and Thickness
Mainly volcanic rocks. Lower part is gray-green basaltic andesite, andesite with tuffaceous shale; the middle part is neutral tuff with breccia andesite. Upper part is intermediate-acid breccia lava with dacite tuff, rhyolite, and fusion tuff. The total thickness is 2600 m.
Relationships and Distribution
Lower contact
At the top, the intermediate-acid breccia lava and basaltic andesite are in integrated contact with the underlying Fu Gongye Nong Fm (Gongyenong Fm in this lexicon's usage)
Upper contact
At the bottom, the intermediate-acid breccia lava and basaltic andesite are in conformable contact with the overlying Bolila Fm
Regional extent
This group is distributed in Jiangda County, Gongjue County, Leiwuqi County and other places in Tibet.
GeoJSON
Fossils
Only in the upper part are the bivalves Costatoria napengensis, Pergamidia attalea, leaf limbs and plant fossil fragments.
Age
Depositional setting
The lithological combination of this group represents the evolution process of the volcanic rock series from medium basic to medium acidity, which finally leads to acidity.
Additional Information
The investigation team of the Sichuan Geological and Mineral Bureau and the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (1982) will see a set of lower red beds, central limestone beds and upper volcanic rocks in the Jiangdawaxu area of Tibet representing the Carnian deposits of the Late Triassic Collectively referred to as the Jiapila Formation, the Dongka Formation is equivalent to the upper volcanic rock layer of the Yuanjiapila Formation.