Chingchi Fm
Type Locality and Naming
No type section was assigned originally when Li and Qiu (1932) proposed the Chingchi 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 Geological Survey Team in 1964. The Chingchi Formation was named by Li and Qiu (1932). The name is derived from Chingchi (spelled Qingxi in Hanyu Pinyin) Village, about 11 km south of the Chengbu Town in Chengbu Miao Autonomous County, Shaoyang City, Southwestern Hunan Province. Originally this unit was called Chingchi Series by Li and Qiu (1932), and was subsequently renamed Chingchi Shale by Zhao and Zhang (1959) and Chingchi Formation by Guangxi Regional Geological Survey Team (1966).
Synonym: （清溪组）
Lithology and Thickness
The Chingchi Formation is mainly a fine-grained clastic sequence deposited by turbidity currents. Lower part consists of black shale, light grey and greyish green sandstone with interbeds of sericitic shale (192 m thick); Middle part consists of dark grey, sandy shale, interbedded with black shale (423 m), Upper part mainly comprises black shale with grey to dark grey dolomitic shale of 10 m thick at the base (99 m). In the reference section, the formation is 750 m thick. Boundaries of the formation are defined by lithologic change by disappearance of underlying black chert of Liuchapo Fm, and appearance of overlying sandstone of Pienchi Fm.
Relationships and Distribution
Lower contact
The Chingchi Fm is in conformable contact with the underlying Liuchapo Fm (=Laobao Fm). The lower boundary of the formation is defined by lithologic change by disappearance of underlying black chert of Liuchapo Fm
Upper contact
The Chingchi Fm is in conformable contact with the overlying Pienchi Fm. The upper boundary of the formation is defined by lithologic change by appearance of overlying sandstone of Pienchi Fm
Regional extent
The Chingchi Formation is exposed in the Jiangnan Basin Area of South China Region, distributed mainly in northeastern Guangxi Zhuang Autonomous Region (Luocheng County of Hechi City, Rong’an and Rongshui counties of Liuzhou City, Quanzhou, Lingchuan and Guangyang counties of Guiling City, and Fuchuang Yao Autonomous County of Hezhou City), characterized by minor vertical variation in lithology but greater lateral lithologic change. In the area north to the line of Rongshui-Luocheng-Yongfu counties, and in Quanzhou County as well, the formation is dominated by carbonaceous shale, black shale and carbonaceous siliceous shale, intercalated with carbonaceous siliceous rock in the lower part, with sandstone and siltstone in the middle part, and with thin-bedded lenticular limestone in the upper part. Southward, at Shouchen of Yongfu County and at Haiyangshan of Lingchuan County, the formation is characterized by coarsening granularity with green sandstone and hetero-granular sandstone, intercalated siliceous rock and carbonaceous shale in the lower part and sandstone intercalated shale and limestone in the middle and upper parts.
GeoJSON
Fossils
The Chingchi Formation contains sponge-spicule Protospongia sp. universally. In addition, micro-paleoplant fossils Trachysphaeridium planum, Pseudozonosphaera verrucosa, Micrhystridium sp., and Chitinozoans Amphorachitina sp., Desmochitina sp. and Lagenochitina sp. have been found from the formation in the Sanjiang Dong Autonomous County, northwestern Liuzhou City, Guangxi Zhuang Autonomous Region.
Age
Depositional setting
The formation probably belongs to turbidity current deposits.
Additional Information