Koujiacun Fm
Type Locality and Naming
The type section is located at the “Damiao Gully section” (E109°07′, N34°15′) of the Koujia village, Maoxi town, about 19 km southeast of Xi’an City, Shaanxi Province (BGMRS(Shaanxi)P, 1998). It was named by Liu et al. (1960).
Lithology and Thickness
It is characterized by a series of brownish-red and orange mudstones, sandy mudstones, and greyish-white and brownish-yellow sandstones. In the bore cores, this formation consists of brown clayey rocks interbedded with greyish-yellow siltstones, greyish-green fine sandstones, and gravels; its top contains the interlayers of black carbonaceous shales or coal streaks. It contains fossil fishes, mammals, mollusks, and sporoplloens. Its thickness is in range of 5 to 142 m.
Relationships and Distribution
Lower contact
In the type section, the Koujiacun Fm unconformably contacts with the underlying Oligocene (or middle Eocene?) Bailuyuan Fm. But regionally, may be underlain by the Lengshuigou Fm (see Additional Information)
Upper contact
In the type section, the Koujiacun Fm is unconformably overlain by the Upper Miocene Bahe Fm..
Regional extent
This formation is mainly distributed to Lantian-Weinan area, Shaanxi Province. The thickness of this formation is about 102 m in Youhe of Weinan, in range of 28 to 79 m in Bahe of Lantian, and in range of 103 to 142 m in the bore cores in Lintong, respectively.
GeoJSON
Fossils
Mammals: Sciuridae indet., Platybelodon granger, Listriodon latianensis, L. intermedius, L. gigas, Lagomeryx complicidens, Gazella sp. (Zhang et al., 1978).
Age
Depositional setting
It is interpreted as river-lake environment.
Additional Information
Upper contact:
In the type section, the Koujiacun Fm is unconformably overlain by the Upper Miocene Bahe Fm..
Regional extent:
This formation is mainly distributed to Lantian-Weinan area, Shaanxi Province. The thickness of this formation is about 102 m in Youhe of Weinan, in range of 28 to 79 m in Bahe of Lantian, and in range of 103 to 142 m in the bore cores in Lintong, respectively.
GeoJSON:
Fossils:
Mammals: Sciuridae indet., Platybelodon granger, Listriodon latianensis, L. intermedius, L. gigas, Lagomeryx complicidens, Gazella sp. (Zhang et al., 1978).
Age:
Tao Deng et al. (2019; Neogene integrated stratigraphy and timescale of China) show it as spanning the Serravallian
Age Span:
Beginning stage: Serravallian
Fraction up in beginning stage: 0.0
Beginning date (Ma):
Ending stage: Serravallian
Fraction up in ending stage: 1.0
Ending date (Ma):
Depositional setting:
It is interpreted as river-lake environment.
Depositional-pattern:
Additional information
The Koujiacun Fm was considered above the Lengshuigou Fm in stratigraphy (Jia et al., 1966; Zhang et al., 1978; Li et al., 1984). However, Qiu and Qiu (1995) considered that the Lengshuigou Fauna from the Lengshuigou Fm is distinctly younger than the Koujiacun Fauna from the Koujiacun Fm, and they suggested placing the Koujiacun Fm under the Lengshuigou Fm. Future work need to be conducted to confirm the stratigraphic correlation between these two formations.