Pienchi Fm
Type Locality and Naming
No type section was assigned originally for Pienchi Formation the when Li and Qiu (1932) proposed the Pienchi Series. An auxiliary section, the Tingjiang-Dongling section, was proposed as representative section of the formation by Pan and Yin in Yin (1997). The section is located between Tingjiang and Dongling villages in Jiuwu Township, Lingchuan County, Guangxi Zhuang Autonomous Region (110°13’E, 25°42’ N), and was measured by Guangxi Regional Survey Team in 1964. The Pienchi Formation was named by Li and Qiu (1932). The name is derived from Hsiaopienchi (spelled Xiaobianxi in Hanyu Pinyin) Village, about 15 km southwest of the Chengbu Town, Chenbu Miao Autonomous County, Shaoyang City, Southwestern Hunan Province. Originally Li and Zhu (1932) called this unit Pienchi Series. The unit was renamed Pienchi Sandstone by Zhao and Zhang (1959) and Pienchi Formation by Guangxi Regional Geological Survey Team (1966).
Synonym: （边溪组）, Bianxi Fm (spelling)
Lithology and Thickness
The Pienchi Formation is mainly a clastic sequence. It is dominated by greyish green, thick-bedded hetero-granular sandstone, arkose-quartzite sandstone, intercalated with minor greyish black, greyish green shale and sericitic shale, and, in part, minor lenses-bearing limestone as well. In the reference section, the formation is 874 m thick.
Relationships and Distribution
Lower contact
The Pienchi Fm rests conformably on the Chingchi Fm. It is defined by disappearance of carbonaceous shale of underlying Chingchi Fm.
Upper contact
It is conformably overlain by the Baidong Fm (Ordovician). It is defined by appearance of limestone of overlying Baidong Fm.
Regional extent
The Pienchi Formation is exposed in the Jiangnan Basin Area of South China Region, distributed mainly in northeastern Guangxi Zhuang Autonomous Region (Rongshui Miao Autonomous County of Liuzhou City and Quanzhou County of Guiling City) and sporadically exposed in Guangyang and Gongcheng counties of Guiling City and Fuchuan Yao Autonomous County of Hezhou City. The Formation keeps less change in lithology everywhere, consisting of a suite of sandstone as the dominant rocks, interbedded with shale and occasionally intercalated with limestone. Thickness of the formation varies between 654 and 874 m.
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Age
Depositional setting
Additional Information