Pingjing Fm
Type Locality and Naming
The type section of the Pingjing Formation is the Pingjing section near Bajiaoping at Bajiao, Ganxi, Yanhe, Guizhou Province, lying 0.5 km west of Ganxi, or 22 km of southwest of the seat of Yanhe County (108°25’E, 28°23’N). The type section was measured by the No. 3 Brigade of Guizhou Regional Geological Survey Team in 1960. In the type section, the Pingjing Formation is 444.0 m thick. The Pingjing Formation was first published by No. 3 Brigade of Guizhou Regional Geological Survey Team (1970). The name is derived from Pingjing Village (actually called Bajiao Village) in Ganxi Township, Yanhe Tujia Autonomous County, Tongren City, northeastern Guizhou Province. The name was originally appeared in a 1966 manuscript by the No. 3 Brigade of Guizhou Regional Geological Survey Team.（Bi, 1998).
Synonym: （平井组）
Lithology and Thickness
The Pingjing Formation is a carbonate sequence. In the type section the formation is divided into two parts: Lower part consists of grey, thin-bedded dolomite, alternated with medium-bedded dolomite with interbeds of brecciated dolomite, and with a 6 m-thick layer of medium- to coarse-grained dolomitic quartzose sandstone at the base. Upper part consists of grey to dark grey, thick-bedded dolomite in lower half, and dark grey, thick-bedded striped limestone, dolomitic limestone, and dolomite in upper half.
The quartzose sandstone at the base of the formation is very stable and widespread. In northeastern Guizhou, this layer is 0.5‒9 m thick and increases in thickness to 6.6‒14.3 m northeastward. In southeastern Chongqing Municipality the granularity of quartzose sandstone decreases down to fine-grained dolomitic quartzose sandstone, intercalated locally with thin-bedded dolomite. In addition, at Shashuping in Youyang Tujia-Mioa Autonomous County, Chongqing, this sandstone layer contains halite pseudo-crystals.
Relationships and Distribution
Lower contact
The Pingjing Fm rests conformably on the Shilengshui Fm. The lower boundary of the formation is marked by the appearance of medium-bedded coarse-grained quartzose sandstone at its base, which overlies on the brecciated dolomite of underlying Shilengshui Fm.
Upper contact
It is overlain conformably by the Loushankuan Fm. The upper boundary is defined by the appearance of thick-bedded dolomite at the base of overlying Loushankuan Fm.
Regional extent
The Pingjing Formation is limitedly exposed in eastern Yangtze Area, South China Region, distributed in Yanhe, Dejiang, Yinjing, and Jiangkou counties, eastern Tongren City, northeastern corner of the Guizhou Province and in the Shizhu, Youyang and Xiushan counties at southeastern corner of Chongqing Municipality. The Formation is 225‒515 m thick at Yanhe and Yinjiang and is 450‒505 m thick at Youyang and Xiushan.
GeoJSON
Fossils
In the type section, the upper half of Pingjing Formation yields trilobite Paranomocarella sp. In other localities, the formation yields also trilobite Lishania.
Age
Depositional setting
In general, the Pingjing Formation was deposited in tidal flat environment.
Additional Information