Aqia Gr
Type Locality and Naming
The type section is in a shaft located in the area of the Hetian River, Xinjiang, and serves as a reference section. Since the Aqia Gr. is commonly exposed in the form of a fault block, it has so far been lacking a complete reference section. It was named by the Compiling Group for the Regional Stratigraphic Chart of the Xinjiang Uygur Autonomous Region in 1981.
Lithology and Thickness
Clastics. It is characterized by a predominance of purplish-red and dark-red siltstones, siltstones and sandstones, intercalated with a great amount of basalt. It is subdivided into three rock associations: (1) Lower clastic rock (Xia Suixie Yan) association representing purplish-red siltstone and sandstone intercalated with marl and nodules, with a thickness of over 266 m; (2) Middle volcanic rock (Hue Shan Yan) association of purplish-red vesicular basalt intercalated with siltstone and fine-grained sandstone, with a thickness of 412 m; and (3) Upper clastic rock (Shang Suixie Yan) association of interbeds of grey and black shales and brown-red siltstone, intercalated with thin-bedded limestone, with a thickness of about 300 m.
Relationships and Distribution
Lower contact
Disconformable contact on the underlying late Carboniferous limestone; or regionally is conformable on limestone of the lower Permian Nanzha Fm
Upper contact
Unconformable contact with the overlying Neogene.
Regional extent
The Aqia Gr is distributed in the southeastern part of the Bachu area and the Great Desert, most of which is covered by the Quaternary System, with only scattered exposures of it having been found on the eastern side of the Xiaohaizi in the vicinity of the Bachu area, the Mazatag area, as well as on the northern margin of the Karaheyi area in the central part of the Great Desert.
GeoJSON
Fossils
Lower clastic-rock association yields the Potonieisporites-Vestigisporites spore-pollen assemblage, with its age being assigned to the early stage of the Yangsingian Series. Upper clastic-rock association yields the Darwinula jatskovae-Darwinuloides puris assemblage of Ostracoda and the Palaeanodonta subcastor-Palaeomutela-verneuili assemblage of bivalves, with its age belonging to the Lengwu’an Stage of the Yangsingian Series until the Lopingian Series (Fang Zhongjie et al., 1996).
Age
Depositional setting
Additional Information