Yancheng Fm
Type Locality and Naming
BGMRJ(Jiangsu)P (1997) assigned a lectostratotype to this formation and redefined its lithology. Its lectostratotype is located at the Deep No. 4 bore of Lingyan (E120°13′, N33°25′), Nanyang’an town, Yancheng City, Jiangsu Province. It was firstly used by East China Petroleum Exploration Bureau in 1958 in its unpublished manuscript. BGMRJ(Jiangsu)P (1984) formally published this formation.
Lithology and Thickness
The Yancheng Fm is divided into two members. Lower member is formed by greyish-green and light-brown sandy and calcareous mudstones, sandstones, and gravels. Upper member is characterized by greyish-yellow clays interbedded with silts and gravels. It contains fossil plant debris, ostracods, charophytes, and sporopollens. Its thickness is in range of 70 to 1538.5 m.
Relationships and Distribution
Lower contact
In the type section, the Yancheng Fm unconformably contacts with the underlying mid-Eocene Sanduo Fm.
Upper contact
In the type section, the Yancheng Fm conformably contacts with the overlying Douchong Fm.
Regional extent
This formation is widely distributed to Huaiyin-Xiangshuikou area, Jiangsu Province. The thickness of this formation varies in space. Its thickness is more than 1.5 km in Sancang of Dongtai County, but is thin as 100 m in Jintan of Changzhou City, Jiangsu Province.
GeoJSON
Fossils
Ostracoda: Ilyocypri radiate, Cyprinotus (Heterocypris) chiuhsiensis.
Charophyta: Croftiella, Ecochara, Maedlerisphaera.
Sporopollens: Ceratoteris, Trapa, Juglans, Pinaceae, Ceratopteris, Polygonum, Compositae.
Age
Depositional setting
It is interpreted as a river or a flood plain depositional environment.
Additional Information