Jingxing Fm
Type Locality and Naming
It was named by the No. 1 Regional Survey Party under the Geological Bureau of Yunnan Province as the “Jingxing Group” in 1965. The naming section is located at Laoniuyakou 4 km northwest of Jingxing of the Mojiang County of western Yunnan.
Synonym: （景星组）
Lithology and Thickness
The lower part of its Lower member is composed mainly of yellow-grey, grey-green and grey-white thick-bedded and massive fine-grained sandstones, intercalated with purple mudstone and pebble-bearing sandstone, with its basal part composed of a layer of calcareous conglomerate being in a disconformable contact with the underlying Bazhulu Formation; the upper part of the lower member, largely of purple mudstone, intercalated with grey, grey-green and purple fine-grained sandstone, siltstone and 11.2 m-thick mudstone, with a thickness of 908 m. Upper member represents purple thick-bedded mudstone and siltstone, intercalated with fine-grained sandstone, with a thickness of 101 m. Total is 1009 m thick.
Relationships and Distribution
Lower contact
The base of the formation is disconformity marked by the occurrence of conglomerate is distinguished from the Bazhulu Fm (late Jurassic) consisting of purple red mudstone and siltstone
Upper contact
The top is bounded by the conformable appearance of gray thick-bedded medium and fine-grained sandstone with siltstone and gravel-bearing sandstone at the base of the Mangang Fm (coeval or synonym with Nanxin Fm).
Regional extent
The formation occurs in the Lanping-Simao area of west Yunnan. It is a consistent lithology in various regions, yet with a greater change in its thickness. In the northern part of the Jinggu area, the upper part of the formation increases in the number of gray beds and in grain size. In Lanlun and Linlun on the west side the lower member of the formation has become coarser and is locally intercalated with coal streaks. It is 800-2100 m in thickness.
GeoJSON
Fossils
It yields Bivalves Koreanaia yunnanensis, Cyotrigonioides puerensis, Nippononaia diana, Plicatounio rostratus, Nakamuranaia mojiangensis, N. hamiaoensis, Peregrinoconcha manliensis, P. lanpingensis, P. dolabrata, P. cardiniformis, P. alta, Sinonaia jindongensis, S. yunlongensis, Yunnanoconcha pupengensis; Ostracods Monosulcocypris reticulata, Cypridea angusticaudata, Rhinocypris tuberculata, Candona yunnanensis, Limnocypridea tumulosa; Estherias (conchostracans) Orthestheria quadrata, Orthestheriopsiis dajingensis; and Reptilia Lanpingosuchus magnus and Tyrannosaurus lanpingensis.
Age
Depositional setting
The formation belongs to freshwater-brackish fluvial-lacustrine deposition.
Additional Information