Anjiacha Fm
Type Locality and Naming
The type section is located at Anjiacha, 15 km to north of Liuxiang Township, Xihe County, Gansu Province. It was named by Gansu Metallurgical Geological Exploration Company in 1981 and quoted formally by Zhu Weiyuan in 1988.
Lithology and Thickness
Phyllite, slate. The Lower part of the Anjiacha Fm is characterized by phyllite and silty phyllite intercalated with marl and nodular bioclastic limestone; the Middle part is composed of thin-bedded metamorphic siltstone intercalated with nodular micrite, phyllitized slate; and the Upper part consists of thin- to medium-bedded micritic bioclastic limestone. It is 447 m in thickness.
At the Jiaogou section (so-called Anxigou Fm), silty slate, phyllite intercalated with thin- to medium-bedded silty crystalline limestone and bioclastic limestone constitute its lower part, and its upper part is dominated by thin- to thick-bedded fine-grained crystalline limestone and marble intercalated with silty slate; it is 310 m in thickness.
Relationships and Distribution
Lower contact
Conformably rests on the Qingshuigou Fm.
Upper contact
Conformably underlies the Honglingshan Fm.
Regional extent
The formation can be found in the north limb of Wujiashan anticline, but its stratigraphic sequence and structure are doubtful.
GeoJSON
Fossils
The formation contains coral Favosites, Squameo favosites, Sociophyllum, Pachyfavosites, Neospongophyllum and brachiopoda Atrypa, Indospirifer.
Age
Depositional setting
Additional Information
The Huangjiagou Fm (Du Yuansheng et al., 1988) in the Dongshan area of Xihe County is roughly equivalent to the middle and upper parts of this formation. The Yuchiba Fm and the middle and upper parts of Leijiaba Fm in Xihanshui area of Lixian County in the west correspond to this formation, but with more clastic composition.