Liangjiashan Fm
Type Locality and Naming
The type section is in Liujiang Basin in Qinhuang dao. The reference section at Zhaogezhuang in Tangshan, Hebei (An et al., 1983). The Liangjiashan Fm is derived from the Liangjiashan Limestone proposed by Ye Liangfu (Yih L.F.) and Liu Jichen in 1919.
The Liangjiashan Limestone is exposed incompletely. Sun Yunzhu (Y.C. Sun) (1935) and Zhang Wentang (1962) renamed it the Liangjiashan Fm. An et al. (1983) reported the Zhaogezhuang section in Tangshan, Hebei, and considered it as a reference section. Sun et al. (1922) defined the strata, equivalent to the Liangjiashan Fm, in Tangshan the coral limestone which was renamed the Archaeo-sponge limestone. Shimizu et al. named the equivalent strata in eastern Hebei the Beijiadian Bed. These terms were not maintained because of their nonstandard naming.
Synonym: (亮甲山组）
Lithology and Thickness
The formation is dominated by thick-bedded limestone, dolomitic limestone and dolomite, with abundant chert bands and concretions, and was deposited in shallow platform setting. In the type area, the Liangjiashan Fm is 161 m thick.
Relationships and Distribution
Lower contact
It rests disconformably on the argillaceous limestone at the top of the Yeli Fm (Yehli Fm) (An et al., 1983).
Upper contact
It is disconformably overlain by the pebbly dolomite at the base of the Xiamajiagou Fm (present Baiyanzhuang Fm) (An et al., 1983), which is a synonym for the lower part of the Majiagou Fm. At Changzhangzi in Pingquan, Hebei, conodont Jumudontus ganada-Scolopodus sunanensis zone has been established at the top of the Liangjiashan Fm, indicating a top boundary higher than that in the type area (An et al., 1983).
Regional extent
The Liangjiashan Fm, with a persistent lithology, varies considerably in thickness along the length of its outcrop. In northern Hebei, it recorded a thickness of 40-250 m; in Hengshan and Wutai Mountain, northeastern Shanxi, it is 197 m thick; 311 m thick in southern Jilin; 95-161 m thick in Taizihe, 124-250 m thick in Fuzhou and 110-174 m thick in western Liaoning.
GeoJSON
Fossils
In Tangshan, the Liangjiashan Fm includes conodonts Scalpellodus tersus zone, Serratognathus bilobatus zone, Serratognathus extensus zone and Paraserratognathus paltodiformis zone, in ascending order; cephalopods Coreanoceras zone and Manchunoceras zone; trilobite Illaenus “Hystricur” zone, and is equivalent to the Adelograptus-Clonograptus zone to Tetragraptus fruticosus zone.
Age
Depositional setting
Additional Information