Yanziping Fm
Type Locality and Naming
The name was proposed by Jin Chuntai et al (1989). The type section is located at the roadside from Longdanxi to Maliuqiao in eastern part of the Erlangshan Mts. area in west Sichuan Province.
Synonym: (岩子坪组)
Lithology and Thickness
It is characterized by purplish red mudstone and dark gray dolomite. Lowermost part, 91 m thick, consists of purple, purplish red mudstone intercalated with yellow green mudstone and siltstone; no fossils are observed. The middle-Lower part, 30 m in thickness, is composed of dark gray thick-bedded micritic dolomite, occasionally with purple and green mudstone beds intercalated. The middle-Upper part, 118 m thick, consists of gray green thin-bedded massive mudstone and dolomitic mudstone and bears bivalve and brachiopod fossils. Uppermost part, 41 m thick, is represented by dark gray thick-bedded sandy bioclastic crystalline dolomite and dark purple, gray green thick-bedded ferriferous sandy crystalline dolomite yet with no fossil record.
Relationships and Distribution
Lower contact
The boundary of the formation with the underlying Baohuoyan Fm is a parallel unconformity. (Wenlock through middle Ludlow is absent).
Upper contact
The boundary of the formation with the overlying Sashuiyan Fm has not been ascertained.
Regional extent
The formation is exposed only in the Erlangshan Mts. area in west Sichuan Province.
GeoJSON
Fossils
It bears bivalve Modiolopsis?, Modiomorpha? sp., Cosmogoniophora sp. and brachiopod Lingula in the middle-upper part of the formation.
Age
Depositional setting
The lithofacies and the biofacies of the formation indicate a near-shore extremely shallow-water, (probably) lagoon facies.
Additional Information