Madatun Fm
Type Locality and Naming
The type section is located to the south of the Yingbeishan Mt.-Huanglingzi Ridge of the Madatun Village, Jiutai City, Jilin Province. It was named by Liu Guoliang from the Regional Geological Reconnaissance Expedition of Jilin Province in 1980.
Lithology and Thickness
Volcaniclastics and Volcanics. Composed mainly of intermediate-acidic volcanic rocks. Lower part is composed of grey-black and purple intermediate-acidic volcaniclastic rocks, intercalated locally with very thick spherulitic rhyolite and amphibole-andesite. The base of the formation consists of thick-bedded grey-green fine-grained sandstone. Upper part is composed of black-grey and grey-green intermediate brecciated tuff, agglomerate, and tuffaceous breccia, while the top part consists of purple tuffaceous conglomerate. Thickness ranges 970-4607 m.
Relationships and Distribution
Lower contact
Conformable contact with the light-brown fine-grained sandstone at the top of the underlying Yangjiagou Fm
Upper contact
Disconformable contact with the overlying Lujiatun Fm of the Lower Triassic Series
Regional extent
Significant variation in its lithology and thickness. In the Lijiagou-Yaojiagou area its lower part is characterized by the increase of the intermediate-acidic volcanic rocks, with a thickness of 4600 m. In the Yangjiagou area in the southwestern part of the region its lower part is composed largely of intermediate volcanic rocks, and its upper part is composed mainly of acidic volcanic rocks, with a thickness of 2300 m; in the areas of the Yingbei Mt. and Mada Mt. in the northeast of the region the formation is predominated by such intermediate rocks as andesite, dacitic tuffaceous lavas, etc., with a thickness of 1031 m.
GeoJSON
Fossils
No fossils have been discovered.
Age
Depositional setting
It is interpreted as a continental intermediate-acidic volcanic-rock series.
Additional Information