Purco Fm
Type Locality and Naming
It was proposed by the Party of Regional Geological Survey, Xizang Bureau of Geology in 1985 and published by Guo Tieying et al in 1991. The type section is located on the northern bank of Yinshuihe River in Domar Township, Rutog (Dêrub) County, the Xizang Zizhiqu.
Synonym: (普尔错组) , Puercuo Fm
Lithology and Thickness
The Purco Fm, about 800 m in thickness, consists of gray, light gray medium-bedded limestone, bioclastic limestone intercalated with quartzose sandstone and siltstone.
Relationships and Distribution
Lower contact
It rests conformably on the Yinshuihe Fm of the Upper Ordovician (not in Ordov lexicon). Regionally, the next older unit is the Xialazi Fm of the Upper Ordovician.
Upper contact
It is disconformably overlain by the Middle Devonian
Regional extent
It is exposed in the area of Yinshuihe River — Wanquanhe River, shaped in nearly latitudinal narrow band of about 40 km long and upmost 5 km wide at the middle sector. The clastic rock increases considerably from Yinshuihe River northwards to Shouxinhu Lake and the granularity changes from fine-grained to coarse-grained as well; slightly metamorphosed lithic sandstone and phyllite may locally appear; the thickness of quartzose sandstone and lithic sandstone increases from 350 m to more than 900 m, and the total thickness from 800 to 1300 m.
GeoJSON
Fossils
The limestone yields rich cephalopods Dawsonoceras sp., Harrisoceroides sp., Geisonoceras cf. rivale, Kopanioceras sp., Harrisoceras sp., Kionoceras sp., Arionoceras submoniilform, Temperoceras (Orthoceras) tritionuum; trilobite Encrinuroides meitanensis, Scotoharpes meitanensis, Latiproetus donqiaoensis; brachiopod Striispirifer sp., Eospirifer cf. subradiatus and crinoid columnal, etc.
Age
Depositional setting
Additional Information