Qiujiahe Fm
Type Locality and Naming
The type section of the Qiujiahe Formation is the Chenjiaba section, located about 2.5 km south of Chenjiaba Village in Chaotian Township, Chaotian District, or about 6 km northwest of Chaotian Town, the seat of Chaotian District, Guangyuan City (105°50’48”E, 32°41’00”N). It is the lower portion of the same section shared by the overlying Youfang Formation. The type section was measured by the Sichuan Second Regional Geological Survey Team in 1963, and in the section the formation is 211.85 m thick. The Qiujiahe Formation was named by Sichuan Second Regional Geological Survey Team (1966). The name is derived from Qiujiahe Village in the Chenjia (or Chenjiaba), the seat of already revoked Chenjia Township that was incorporated into Chaotian Township in 2019, Chaotian District, Guangyuan City, northeastern Sichuan Province.
Synonym: （邱家河组）
Lithology and Thickness
The Qiujiahe Formation is a sequence of siliceous rocks in the lower and middle parts and epi-metamorphic manganiferous rocks in the upper part. In the type section, the formation is divided into 4 lithologic beds, from bottom up: 1, black, medium-bedded to massive siliceous rock, intercalated with lenticular dolomite (28.60 m thick); 2, black, thin-bedded siliceous rock, intercalated with light grey, thin-+- to medium-bedded silicified limestone with a layer of breccia, 5 m thick, at the base (100. 60 m); 3, black, thin-bedded siliceous rock with phosphate nodules and interbeds of dolomite (38.15 m); 4, black carbonaceous phyllite with 3 layers of dialogite in the lower part. (44.50 m).
Relationships and Distribution
Lower contact
The Qiujiahe Fm is in conformable contact with the underlying Töngying Fm (Tongying Fm; Dengying Fm). The lower boundary of the formation is marked by lithological change from dolomite of Tongying Fm to the siliceous rock at its base
Upper contact
The Qiujiahe Fm is in conformable contact with the overlying Youfang Fm. The upper boundary is marked by lithological change from the phyllite at its top to the siliceous band-bearing sandstone of the Youfang Fm.
Regional extent
The Qiujiahe Formation is exposed in northern Qangtang-Simao Region, distributed in a narrow northeast- and southwest-trending area in north and northeastern Sichuan (Anxian, Chaotian, Beichuan, Maoxian, Pingwu, and Qingchuan counties or districts). The thickness of the formation is relatively stable, varying from 141 to 163 m.
GeoJSON
Fossils
No fossil has been found in the formation yet.
Age
Depositional setting
Additional Information