Dongdahe Fm
(65), Kungurian Stage (late-Cisuralian Epoch; late-Early Permian)
Type Locality and Naming
The type section is located at Dongdahe 50 km to the north of Baoxing County Town, Sichuan Province, while its reference section is situated at Shilama 30 km to the north of Bangda Country, Kangding County, Sichuan Province. It was named by the West Sichuan Geological Research Party under the Chinese Academy of Geological Sciences in 1965.
Lithology and Thickness
Limestone and Shale. It is divisible into two parts: The Lower part is composed of grey calcareous slate and clayey limestone, intercalated with carbonaceous shale, with a thickness of 14 m; and with a basal fine-gravel conglomerate. The Upper part is composed of grey and dark-grey thin- and medium-bedded limestones, intercalated with shale, siliceous rocks and skeletal limestone, with a thickness of 82 m.
Relationships and Distribution
Lower contact
Disconformable contact to the limestone on top of the underlying Shilama Fm; except for a conformable contact with the underlying strata in the Dongdahe area of Baoxing County.
Upper contact
Disconformable contact is inferred due to the lack of fossils between the formation and the overlying strata.
Regional extent
Distributed in the northern part of Sichuan Province with a stable lithology. In the Lianhua Mt. area it represents grey thick-bedded quartz-bearing sandstone, intercalated with carbonaceous slate, with a thickness of 105 m. In the Xindianzi area of Wenchuan County it is composed mainly of grey medium-, and thick-bedded limestone and clayey limestone, intercalated with slate, with a thickness of 20-30 m. In the Huanglong area of Songpan County the formation is composed of black carbonaceous sericite-slate and phyllite, with a thickness of 20 m
GeoJSON
Fossils
The limestone in the standard section yields Fusulinida such as Misellina claudiae and Parafusulina sp., etc. In the vicinity of the standard section there also occurs Pisolina subsphaerica, etc., whose stratigraphic horizon is corresponding to that for the Qixia Fm, belonging to the early stage of the Yangsingian Epoch.
Age
Depositional setting
It is interpreted as carbonate platform-slope deposits.
Additional Information