Changjianggou Fm
Type Locality and Naming
The type section is the Changjianggou-Nianziba section, located at Modaoya, north of Changjianggou, Shangsi Township, Jiange County, Guangyuan City, Sichuan Province (105°26’23” E, 32°24’00” N). It lies about 11 km northwest of the Shangsi Town or 15 km northwest of Jiange County, and is the same type section with the Modaoya Formation. The section was measured by the Sichuan Second Regional Geological Survey Team in 1964. The Changjianggou Formation was named by Sichuan Second Regional Geological Survey Team (1966). The name is derived from Changjianggou Village in Shangsi Township, Jiange County, Guangyuan City, northeastern Sichuan Province.
Synonym: （长江沟组）
Lithology and Thickness
The Changjianggou Formation is a fine-grained clastic sequence, consisting mainly of greyish green silty shale and calcareous or argillaceous siltstone in the lower part, and calcareous silty shale, sandy shale, and quartzose sandstone in the upper part. In the type section, the formation is over 1287.7 m thick.
Relationships and Distribution
Lower contact
The basal boundary of the Changjianggou Fm is unknown as no lower part of the formation is exposed.
Upper contact
It is conformably overlain by the Modaoya Fm
Regional extent
The Changjianggou Formation is exposed in the Yangtze Area of South China Region, distributed in northern and middle sections of the Longmenshan Mountain, a mountain in north-south direction west of Guangyuan City in northeastern Sichuan Province. It deceases thickness southward significantly from 1200 m in the northern section of Longmenshan Mountain to merely 150 m thick in the middle section of Longmenshan Mountain, there is no exposure of the formation observed in the southern section of the Longmenshan Mountain.
GeoJSON
Fossils
The lower part of the formation yields bradoriids Kunmingella, Hanchungella, and Shensiella and the upper part yields trilobites Wutingaspis, Eoredlichia, Guangyuania, and Eomalungia.
Age
Depositional setting
It represents basinal subtidal flat setting.
Additional Information