Ganhegou Fm
Type Locality and Naming
Liupanshan-Helanshan region. The type section, Shuidaogou–Ganhegou section, the same as the type section of Zhangenbao Formation, is located at the Holiugou, 8 km northest of the Baima Township, Zhongning County, Zhongwei City. It is located 35 km northeast of the Zhongning County, 35 km southwest of the Wuzhong City. Geographical coordinates: 37°41′59.9”N, 105°58′43.61″E (GPS). It was named by the Third Regional Survey Party, Ningxia Bureau of Geology in 1975.
[Figure: Geological map around the Shuidaogou-Ganhegou section.]
Lithology and Thickness
The lithology and thickness of the formation change greatly. At Ganhegou at the west foot of Niushou Mountain, the Lower part is alternating beds of grayish conglomerate and grayish white sandstone and earth-red clay; the Upper part is gray conglomerate and grayish white sandstone with minor red clay. The total thickness is 147–800 m. At Wuzhong and other places at the east foot of Niushou Mountain, the formation consists of yellowish brown sandy conglomerate and brick-red mudstone, with a visible thickness of ~30 m. In the vicinity of Sikouzi, Guyuan, it is composed of orange-yellow and yellowish brown marly siltstone with sandstone, pebbly sandstone, conglomerate and minor gypsum, being 170–634 m thick. At Huangjiashui, Tongxin, the formation is made up of brownish red and orange-red mudstone and sandstone with their grayish green equivalents, being ~27 m thick.
[Figure: Photos of the Stratigraphical features of the Ganhegou Formation. A, the angular discomformity between the Ganhegou and the underlying Zhangenbao Fm; B, the small-scaled cross-bedding with gravels and fossil fragments in the strata.
[Figure: Stratigraphic section of the Shuidaogou-Ganhegou Section]
Relationships and Distribution
Lower contact
This formation overlies the Miocene Zhangenbao Fm by an angular disconformity of a ~1-2 Ma hiatus.
Upper contact
It unconformably underlies the lower Pleistocene gray conglomerate. However, T. Deng et al. (2019; Neogene chapter of China Integrated Stratigraphy and Timescale) show a disconformably overlying Messinian-Pliocene age Leijiahe Fm (not in Lexicon entries; not found in web search), followed by the Wucheng Loess (Quaternary).
Regional extent
Distributed along the east and west foothills of the Niushoushan Mountains in the Wuzhong and Zhongwei Cities. It is also reported from the Liupanshan foothills in the Guyuan City, south of the Ningxia.
GeoJSON
Fossils
Perissodactyla: Hipparion weihoense, Ningxiatherium longirhinus, Acerorhinus cf. tsaidamense; Artiodactyla: Qurliqnoria cheni, Olunbulukia tsaidamensis; Charophytes: Tectochrar meriani, Tectochrar meriani; Proboscidea: Tetralophodon cf. Euryrostris, Ostracods: Paracandona sp.
Age
Depositional setting
Alluvial fans deposits and fluvio-lacustrine deposits.
Additional Information