Chintingshan Fm
Type Locality and Naming
The type locality of the Chintingshan Formation is located about 17 km northwest of the seat of Zunyi City. No type section was assigned by Liu (1942) when he proposed the unit. An auxiliary section, the Yankong section, was proposed by Yin in Dong (1997) as representative section of the formation. The section lies near Yankong Town in Yankong Township, about 11 km northeast of the seat of Jinsha County, Bijie City, western Guizhou Province (106°15’E, 27°35’N), and was measured by Zhang Zhenghua, Zhou Zhiyi, and others from the Institute of Geology, Guizhou Headquarter of Petroleum Exploration and the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences in 1970. The Chintingshan Formation was named by Liu (1942). The name is derived from Chintingshan (spelled Jindingshan in Hanyu Pinyin) Mountain, Honghuagang District, Zunyi City, north-central Guizhou Province. Originally it was called Chintingshan Bed by Liu (1942) and was renamed Chintingshan Formation by Lu (1962), which has been widely used by subsequent authors.
Synonym: (金顶山组)
Lithology and Thickness
The Chintingshan Formation is basically a clastic sequence. Lower part consists of silty shale, shale and sandstone, with gravel-bearing, medium- to coarse-grained quartzose sandstone at the base, Middle and Upper parts are silty shale and silty mudstone, intercalated with oolitic or pisolitic limestone and archaeocyathid limestone. In the reference section, the Chintingshan Formation is 166.6 m thick.
Relationships and Distribution
Lower contact
The Chintingshan Fm is in conformable contact with the underlying Mingsinssu Fm. The lower boundary of the formation is defined by appearance of the gravel-bearing, medium- to coarse-grained quartzose sandstone at its base or by disappearance of green mudstone of the underlying Mingsinssu Fm. Yet has no consensus been reached on the placement of the lower boundary of the Chintingshan Fm. The debate has been focused on whether the gravel-bearing, medium- to coarse-grained quartzose sandstone yielding Paokannia-Szechuanolenus trilobite assemblage should be placed down to the top of the Mingsinssu Fm, or to the base of the Chintingshan Fm. The latter opinion is accepted for the present Lexicon as the appearance of the gravel-bearing medium- to coarse-grained quartzose sandstone represents not only the beginning of a new sedimentation circle, but also the base boundary of the sequence in view of sequence stratigraphy.
Upper contact
The Chintingshan Fm is in conformable contact with the overlying Chinghsutung Fm. The upper boundary is defined by the disappearance of green mudstone at its top or the appearance of oolitic limestone at the base of the overlying Chinghsutung Fm.
Regional extent
The Chintingshan Formation is exposed in the Yangtze Area of South China Region, distributed in western and middle parts of northern Guizhou Province, northeastern Sichuan Province, and eastern Chongqing Municipality. The thickness of the formation varies from 107 m to 210 m in northern Guizhou, including a 177 m thickness in a drilling well at Jingsha County. The formation becomes thicker northeastward as reaching 283 m at Bohai of Youyang County, and 368 m at Gaotian of Xiushan County, both counties are in eastern Chongqing Municipality, where the formation bears no archaeocyathids but yields oryctocephalid trilobites, such as Arthricocephalus and Cheiruroides, etc. Those trilobites are known usually from the Balang Fm of eastern Guizhou and western and northwestern Hunan.
GeoJSON
Fossils
In the type section, the basal part of the Chintingshan Formation yields trilobites Paokannia sp. and Szechuanolenus nanjiangensis; the lower part yields rich trilobites, including Palaeolenus lantenoisi, P. deprati, Kootenia sp., Redlichia ichangensis, and R. kaiyanensis; and the upper part yields trilobites Palaeolenus fengyangensis, Pseudoichangia, Redlichia hupeiensis, R. murakamii and archaeocyathid Retecyathus.
Age
Depositional setting
Additional Information