Chinghsutung Fm
Type Locality and Naming
The type locality of the Chinghsutung Formation, lying about 2 km southeast of the old seat of Meitan County. No type section was assigned by Yin et al. (1945), who, however, described a composite section based on outcrops exposed at several localities around Qingxudong (at Gaoshan, Yangcun and Xinglongchang of Meitan County). An auxiliary section, the Meiziwang section, was proposed by Yin in Dong (1997) as representative section of the formation. The section is located at Meiziwang Village in Maoping Township, lying about 32 km south of the new seat of Meitan County, Guizhou Province (107°53’E, 27°23’N). It was measured by No. 3 Brigade of Guizhou Regional Geological Survey Team in 1973. In this section, the Chinghsutung Formation is 208.3 m thick. The Chinghsutung Formation was named by Yin et al., (1945). The name is derived from Chinghsutung (spelled Qingxudong in Hanyu Pinyin) Cave, Meitan County, Zhunyi City, north-central Guizhou Province. Originally it was called Chinghsutung Limestone by Yin et al., (1945) and afterward renamed Chinghsutung Formation by Lu (1962), which has been widely used by subsequent authors.
Synonym: （清虚洞组）
Lithology and Thickness
The Chinghsutung Formation is a carbonate sequence. In the type section the Lower part consists of dark grey, thin - to medium-bedded oolitic limestone and grey, dark grey, thick-bedded limestone with rich trilobites (38 m thick); Middle part is grey thick-bedded, striped dolomitic limestone, and calcareous dolomite intercalated with striped limestone (112 m); and Upper part of grey thin- to thick-bedded dolomite, pelitic dolomite intercalated with lamellar dolomite, and calcareous, pelitic mica-bearing siltstone (58 m).
Relationships and Distribution
Lower contact
The Chinghsutung Fm is conformably rests conformably on underlying Chintingshan Fm. The lower boundary of the formation is defined by appearance of thick-bedded oolitic limestone at its base or disappearance of sandy shale at the top of the underlying Chintingshan Fm
Upper contact
The Chinghsutung Fm is conformably overlain by Kaotai Fm. The upper boundary is defined by the disappearance of thick bedded oolitic dolomite at its top and the appearance of thin-bedded sandy dolomite at the base of the overlying Kaotai Fm
Regional extent
The Chinghsutung Formation is exposed in both the Yangtze and the Jiangnan Slope areas of South China Region, distributed widely in northeastern Yunnan, northern Guizhou, northeastern Sichuan, and northwestern Hunan provinces and eastern Chongqing Municipality. Lithological variations of the formation are notable. In western Guizhou, the formation comprises more dolomite bearing gypsum, indicating a supralittoral salted lagoon sedimentation, while it increases calcareous and pelitic contents eastward in central Guizhou, reflecting a normal neritic environment. In the eastern Guizhou (east of Fenggang and Wong’an counties) more shale interbeds are increased in the formation.
GeoJSON
Fossils
In the representative section, the lower part of Chinghsutung Formation yields trilobites Redlichia murakamii and Hoffetella sp., the middle part yields trilobites Redlichia cf. guizhouensis and Eoptychoparia sp. No fossils were known from the upper part of the formation in the type section but Redlichia guizhouensis, R. nobilis and Antagmus were reported from the upper part in some other sections.
Age
Depositional setting
The formation represents neritic deposits.
Additional Information