Chongzhuang Fm
Type Locality and Naming
The type section of the formation is the Chongzhuang section, which is located at railway side, 1 km south of abandoned Chongzhuang railway station (103°43’E, 23°09’N), or about 19 km northeast of the seat of Pingbian County. The section was measured by No. 6 Brigade of Yunnan Second Regional Geological Survey Team in 1972. In this section, the Chongzhuang Formation is about 168.9 m thick. The upper boundary of the type section does not clearly outcropped. The Chongzhuang Formation was named by No. 6 Brigade of Yunnan Second Regional Geological Survey Team (1972). The name is derived from Chongzhuang Station of the Kunming‒Hekou Railway in Wantang Township, Pingbian Miao Autonomous County, Honghe Hani-Yi Autonomous Prefecture, southern Yunnan Province. The railway station has been abandoned.
Synonym: （冲庄组）
Lithology and Thickness
The Chongzhuang Formation is a clastic sequence. The formation mainly consists of yellowish brown, grey to greyish green, medium- to thick-bedded, fine-grained quartzose sandstone, arkose-quartzose sandstone, and siltstone, interbedded with sericitic slate and silty slate. In the low-middle part of the formation, there is a marker bed, 1.2 m thick, of brownish ferriferous coarse-grained sandstone, and at the base there is a layer of greyish white, thick-bedded quartzose siltstone, which is 6.5 m in thickness.
Relationships and Distribution
Lower contact
The Chongzhuang Fm is in conformable contact with the underlying Langmuqiao Fm. The lower boundary of the formation is defined by appearance of greyish white, thick-bedded quartzose siltstone of the formation and by the disappearance of green silty sericitic slate of underlying Langmuqiao Fm
Upper contact
The Chongzhuang Fm is in conformable contact with the overlying Dazhai Fm. The upper boundary is defined by disappearance of light-colored, dominated sandstone of the Dazhai formation.
Regional extent
The Chongzhuang Formation is exposed in the southwestern Yangtze Area of South China Region, restricted merely in Pingbian County belonging to the Honghe Hani-Yi Autonomous Prefecture in the mid-southern Yunnan. Southward the formation increases thickness and darkness but decreases particle size with the thickness ranging from 95.5 to 446.3 m.
GeoJSON
Fossils
In the type section, the Chongzhuang Formation yields trilobite Ichangia sp. from the ferriferous coarse-grained sandstone in the low-middle part and Palaeolenus sp. and Redlichia sp. in the upper part.
Age
Depositional setting
The formation bears flyschoid rhythmite and represents deposits in rather deeper-water shelf environment.
Additional Information