Yingou Gr
Type Locality and Naming
The type section is at Yingou in Yumen City, Gansu. The Yingou Gr is derived from the Yingou Series proposed by Yin Zanxun et al. in 1957. In 1962, Zhang Wentang divided the Yingou Gr into three parts corresponding to the Llanvirn, Arenig and Tremadoc respectively. Qilianshan Party of Geology, Chinese Academy of Sciences, renamed the Yingou Gr the Yingou Fm.
Synonym: (阴沟群）
Lithology and Thickness
The group is divided into two parts. The lower part is composed of volcanic breccia and green basic volcanic rock, felsite, and the upper part is dominated by limestone and shale intercalated with breccia. In the type area, the Yingou Gr recorded an incomplete thickness of 592 m.
Relationships and Distribution
Lower contact
Upper contact
The Yingou Gr is probably conformably overlain by the volcanic breccia at the base of the Zhongpu Gr.
Regional extent
The Yingou Gr has a large distribution area and variable considerably lithology. At Dahebakou to Erdaochuan, 10 km southwest of Yingou in Yumen, it is composed of about 2000 m of chert intercalated with sandy slate, and yields trilobites Onyehopyge, Apatokephaius, being Tremadocian in age. At area southeast from there, the Yingou Gr recorded an incomplete thickness of 500 m, and is represented by green tuffaceous sandstone, slate and limestone yielding the trilobites and graptolites found in the upper part. On the western slope of Daban Hill in Jingyuan, Gansu and Langshidanggou in Huzhu County, Qinghai, the upper part changes into dominantly siliceous slate, and yields graptolites Didymograptus hirundo, D. cf. abnormis, with an incomplete thickness of 450 m. In Qinghai, the Yingou Gr is exposed in northern Qilian Mountain, and is composed dominantly of slate, sandstone phyllite and basic volcanic rock, with less limestone and a maximum thickness of 4000 m. At Daliang in Menyuan, Qinghai, the Yingou Gr is 989 m thick.
GeoJSON
Fossils
This stratigraphic unit yields trilobites Ceratopyge transversa, C. elongata, Symphysurus subrectangulatus, Harpides troedssoni, Yinaspis granulatus, Szechuanella rectangula, Apatokephalus yini, A. kansuensis, Geragnostus crassus and graptolites Dictyonema sp., Isograptus sp., Didymograptus sp., Climacograptus sp.
Age
Depositional setting
Additional Information