Alengchu Fm
Type Locality and Naming
The type section is situated 0.7 km north of the Alengcuo village, about 15 km east of Mingyin Town, along the Jinshajiang River valley, Lijiang Zangzu Zizhixian (GPS: 100o30’34.1’’-27o17’6.6’’N). Yunnan Province. It was named by Duan Yanxu, Li Dingrong and Leng Conglin in 1974 and was published by Yu Changmin and Liao Weihua in 1978.
Lithology and Thickness
Clayey limestone. It is characterized by dark-gray medium- to thick-bedded limestone intercalated with shale. In the upper few thin-bedded calcareous shale and tentaculites-bearing bioclastic limestone are observed. The thickness is about 150 m.
[Figure Close-up to the outcrop bearing-tentaculites of the lower part of Alengchu Formation in the stratotype. The tentaculite Nowakia sp. is generally 4-5 mm long.]
Relationships and Distribution
Lower contact
The base is a conformable contact onto the underlying Shanjiang Fm, and is placed at the appearance of medium-thick bedded bioclastic limestone.
Upper contact
The upper boundary with the overlying Banmandaodi Fm is sharp, separated by thick-bedded sandy conglomerate.
Regional extent
This formation is mainly distributed in Lijiang, Ninglang, Luoshui and Mingyin areas of western Yunnan.
GeoJSON
Fossils
Abundant tentaculites of the Nowakia acuaria Zone and corals Spongophyllum pseudofritch, S. cyathophylloideS, Gurjevshkiella cylindrical, Lyrielasma chagmani, a Embolophyllum sp. Squameofavosites sp., Pachyfavosites sp. are found.
Age
Depositional setting
It is interpreted as platform margin and slope environments.
Additional Information