Zuoqu Fm
Type Locality and Naming
The type section is at Zuoqu about 20 km southwest of Neixiang City, Henan. The Zuoqu Fm was named by Beijing College of Geology in 1960-1965, and was published by Pei Fang et al. (1989). Pei et al. (1989) divided the Zuoqu Fm into the Liang'ao Fm in the lower part and the Zuoqu Fm including the sandstone and shale at the base of Shiyanhe Fm of Yan et al. (1983), on the basis of the conodont Serratognathus diversus found from the lower part of the previously defined Zuoqu Fm at Liang'ao in Xichuan Henan.
Synonym: (岞𪨰组）
Lithology and Thickness
The formation is dominated by grayish green basaltic porphyrite, purple tuff, tuffaceous sandy conglomerate and volcanic breccia intercalated with thin- to medium-bedded limestone. In the type area, the Zuoqu Fm is 340 m thick. Generally, the Zuoqu Fm is dominated by basic eruptive rock, and varies considerably in lithology and thickness along the length of its outcrop.
Relationships and Distribution
Lower contact
Its lower and upper boundaries are marked by the first appearance and final disappearance of the volcanic rock (Liu Yinhuan et al., 1991). The Zuoqu Fm is in disconformable contact with the underlying strata of the Bailongmiao Fm.
Upper contact
Regional extent
In the type area, the Zuoqu Fm varies considerably in lithology and thickness along the length of its outcrop. At Shiyanhe in the western part, the Zuoqu Fm is 25 m thick, and is composed of tuffaceous sandy conglomerate, volcanic breccia intercalated with thin-bedded limestone. Eastward to Wangguangou, it is represented by 110 m thick altered tuff and tuffaceous breccia intercalated with limestone. And at Zuoqu in Neixiang, the Zuoqu Fm is dominated by basaltic porphyrite, with a thickness of 340 m.
GeoJSON
Fossils
The limestone intercalations yield conodonts Serratognathus diversus and Oistogus sp.
Age
Depositional setting
Additional Information