Maobaguan Fm
Type Locality and Naming
No type section was assigned when the formation was erected. An auxiliary section, the Banbianjie-Dabacun section, was proposed by Ma (1998) as representative section of the formation. The section is located on the west bank of Renhe River in the Maoba Township, Ziyang County (108°13’25”E, 32°19’00”N). The section lies about 37 km southwest of the seat of Ziyang County, and was measured by the No. 185 Shaanxi Coal Field Geological Team in 1978. In this section, the Maobaguan Formation is 862.3.0 m thick. The Maobaguan Formation was named by Shaanxi Regional Geological Survey Team (1966b). The name is derived from Maobaguan in Maoba Township on the west bank of Renhe River in southern Ziyang County, Ankang City, southern Shaanxi Province.
Synonym: （毛坝关组）
Lithology and Thickness
The Maobaguan Formation is mainly a carbonate and clastic sequence bearing beds of bone coal. In the Banbianjie-Dabacun section, the formation is divided into five lithologic beds, from bottom up: 1, greyish black carbonaceous slate with interbeds of bone coal (48.1 m thick); 2, dark grey, thin- to thick-bedded limestone (145.1 m); 3, grey, thin-bedded limestone with interbeds of slate, which increase up-section (145.1 m); 4, grey to dark grey, medium-bedded marlstone with three interbeds of bone coal (102 m); 5, grey, thin-bedded limestone with interbeds of calcareous slate in the lower part and grey calcareous slate with interbeds of thin-bedded limestone in the upper part (422 m).
Relationships and Distribution
Lower contact
The Maobaguan Fm rests conformably on the underlying carbonate Jianzhuba Fm
Upper contact
It is conformably overlain by carbonate Baguamiao Fm.
Regional extent
The Maobaguan Formation is exposed in the Jiangbei Slope Area of South China Region, showing west-east band-like distribution in southeastern Shaanxi Province (i.e. from Shuanghe and Tianba of Zhenba County in the west, to Yuhuangding of Wanyuan County, to Dabatang, and Zhuanjiaolou of Ziyang County, to Xihe—Jinjihe of Langao County, to Baxianjie‒Jiangxijie of Pingli County, and to Shizaihe and Shangzhu of Zhenping County in the east). Extending eastward from Maobaguan, the clastic rock in the formation increases progressively, whereas the thickness decreases gradually, varying from 881 m to 220 m. The Maobaguan Formation represents carbonate sedimentary facies on the outer continental shelf.
GeoJSON
Fossils
No fossil was reported from the Maobaguana Formation. Previously, trilobites Pianaspis sp. and Anomocarella chinensis, Peronopsis sp. and Linguagnostus sp. were reported from the formation at Jiuchang in Langao County, southeastern Shaanxi Province and at Yuhuangding of Wanyuan County, northeastern Sichuan Province respectively (Shaanxi Regional Geological Survey Team, 1966b). However, these fossils were confirmed from the overlying Baguamiao Fm rather than from the Maobaguan Formation by Yang et al (1991).
Age
Depositional setting
Additional Information