Paoshan Fm
Type Locality and Naming
The type section of the Paoshan Formation, measured by Sun (1939), is the Kongquesi section, near the Kongquesi Temple in Pupiao Township, Longyang District, Baoshan County, western Yunnan Province. As the formations is better outcropped at the Daguanshi-Lengshuqing area, a section was measured between Daguanshi and Lengshuiqing villages by Shen Xinfu and Li Shanji in 1959, which has been usually selected as representative section for the Paoshan Formation. However, even in this section the Paoshan Formation is still incomplete as its basal part is cut off by fault. No better section for the formation is known yet. The Daguanshi-Lengshuiqing section lies also in Longyang District of Baoshan City (99°07’E, 25°00’N), about 14 km southwest of the seat of Baoshan City. The Paoshan Formation was named by Sun (1939). The name is derived from Paoshan County (now Baoshan City) (spelled Baoshan in Hanyu Pinyin); the county is now renamed Longyang District of Baoshan City), western Yunnan Province. Originally the formation was called Paoshan Shale, and was renamed Paoshan Formation by the No. 1 Brigade of Yunnan First Regional Geological Survey Team (1966).
Synonym: （保山组）
Lithology and Thickness
The Paoshan Formation is essentially a classic sequence, consisting of yellowish brown, yellowish green and greyish brown silty shale, siltstone and shale. It bears some interbeds of limestone up-section. In this section, the exposed Paoshan Formation is 377.5 m thick.
Relationships and Distribution
Lower contact
The Paoshan Fm rests conformably on the underlying Liushui Fm, although in the Daguanshi-Lengshuqing section, the lowermost exposed yellowish-brown sandstone of the formation is in fault contact with the underlying Dingjiazai Formation of the Carboniferous System. The lower boundary of the Paoshan Formation is marked by the disappearance of limestone at the top of the Liushui Formation and appearance of shale or siltstone at the base of the Paoshan Formation.
Upper contact
The Paoshan Fm is comfortably overlain by the Laojianshan Fm of the Ordovician System, which bears greyish purple and yellowish brown, thin-bedded, micaceous sandstone at its base.
Regional extent
The Paoshan Formation is exposed in the Baoshan-Northern Tibet Region, distributed in Nujiang Lisu Autonomous Prefecture (Lushui County), Baoshan City (Longling, Longyang, Shidian counties), Lincang City (Yongde and Zhenkang counties) and Dehong Dai-Jingpo Autonomous Prefecture (Luxi County), western Yunnan Province. The maximum thickness of the formation is 1198 m at Liushui, thinning southward to 495–566 m in the Shidian-Longling-Luxi area, and thickening again further southward to over 1000 m at Zhenkang.
GeoJSON
Fossils
The Paoshan Formation yields rich fossils, including trilobites Calvinella, Changia, Eosaukia, Homagnostus, Lonchopygella, Lophosaukia, Mansuyia, Metacalvinella, Mictosaukia, Pagodia, Proceratopyge, Pseudagnostus, Saukia, and Tsinania. and brachiopods Billingsella, Eoorthis, and Finkelnburgia.
Age
Depositional setting
The formation represents normal shallow-water continental shelf setting.
Additional Information