Poduan Fm
Type Locality and Naming
"In 1977, the Eighth General Survey and Exploration Group of Guizhou established the "Dujishan Formation" 2 km north of Qingyan in Guiyang to represent the reef (shoal) facies deposits of the Middle Triassic Anisian in Central Guizhou. In 1980, in view of the Dujishan Fm near Qingyan mainly composed of dolomite, the Diao Team of Guizhou District established another Lipo Fm." (text provided by Triassic lexicon compilers; but seems to not explain name/locality of the Poduan Fm).
Synonym:
Lithology and Thickness
It is mainly composed of endoclastic limestone and bioclastic limestone composed of a large number of algal debris, algal masses and bioclasts. The algal debris and algal masses are mainly composed of cyanobacteria, followed by green algae and few red algae. The bioclasts were mainly gastropods, brachiopods, foraminifera, bivalves, crinoids, and a few sponges, hydra, "calcium ball" coral, bryozoans, etc. The thickness of the stratum is 500 to 1100 m.
Relationships and Distribution
Lower contact
Conformable contact between the clastic limestone in the bottom and the underlying Anshun Fm.
Upper contact
Conformable below the overlying Longtou Fm.
Regional extent
The formation is distributed intermittently along Qingyan, Zhenning, Zhenfeng, Anlong and Xingyi mud lines with a width of 0 to 10 km in Guizhou.
GeoJSON
Fossils
It contains bivalves fossils Neomorphotis magneauritus, N. elongatus, N. intermedius, N. giganteus, Ovulthopecten subarcoides, Leptochondria cf. illyrica, L. cf. subillyrica, brachiopod fossils Diholkorhynchia sinensis, Nudispiriferina minima and ammonoid fossils Japonites sp., Leiophyllites sp.
Age
Depositional setting
It is interpreted as reef (shoal) facies deposit.
Additional Information