Daheshen Fm
(20), early Middle Permian
Type Locality and Naming
The type section is section is located in the Yantonglazi and the Xihan Mt. by the Yinglin Village, Daheshen area, Changshan Country, Huadian County, Jilin Province. In 1980 Mang Donghong recommended that the Xishan section of the Sandaogou area in the Changshan Forestry Center be a supplement to represent the lower member of the formation. It was named by the Jilin 2nd Geological Survey Party et al. in 1975, and was cited publicly first by the Compiling Group for the Regional Stratigraphic Chart of Jilin Province (1978).
Lithology and Thickness
Volcaniclastics. It is divisible into three lithologic members: Lower member is composed of grey and yellow-brown acidic volcaniclastics, with a thickness of 832 m. Middle member is composed of dark-grey and grey-green intermediate volcaniclastics, intercalated with intermediate-acidic and acidic tuffs and lavas, with a thickness of 1327 m. Upper member is composed of interbeds of yellow-brown and grey-green acidic volcaniclastics, rhyolite, and grey-black sandstone, sandy conglomerate and slate, yielding abundant animal and plant fossils, with a thickness of 2070 m. The basal part of the formation consisting of rhyolitic tuffs. The formation is predominated by tuffaceous rocks whose ratio of volcaniclastics to lavas to normal sedimentary rocks is of 75:10:15. The total thickness of the formation is of 1000 m (at Jiaohe River) to 4300 m (at Changshan Mt.).
Relationships and Distribution
Lower contact
Unconformable contact with the underlying Shoushangou Fm.
Upper contact
Unconformable contact with the overlying Fanjiatun Fm
Regional extent
This formation is distributed in the Huadian, Panshi, Yongji and Jiaohe areas. In the northern part it is the acidic lavas that are predominant and are intercalated with limestone, with the amount of interbeds of volcaniclastics and normal sedimentary rocks increasing southerly. Meanwhile up to the Daheshen of the Huadian-Shoushangou area, it is the normal sedimentary rocks that are predominant. In the region from north to south sea-water depths were getting shallower, and the volcanic activities were getting weaker, with the volcanic rocks having changed from being acidic to intermediate or intermediate-basic in composition.
GeoJSON
Fossils
Corals such as Lytvolasma, Szechuanophyllum, Waagenophyllum; Fusulinida such as Parafusulina, Schwagerina, Monodiexodina sutschanica, etc., as well as Angara flora represented by Cardioneura, Crassinervia, Noeggerathiopsis and Paracalamites.
Age
Depositional setting
It is interpreted as a volcaniclastic paralic-facies deposits of the oceanfront.
Additional Information