Jiulongshan Fm
Type Locality and Naming
It was named by Ye Liangpu as the “Jiulognshan System” in 1920. The naming locality is situated at the Jiulong Hills of Mentougou District, Beijing City, without designating the section for creation of the formation, with its reference section being located at the Dataipan Gully of Mentougou District, Beijing City.
Synonym: （九龙山组）
Lithology and Thickness
Composed mainly of continental clastic rocks, intercalated with volcaniclastic rocks, with its basal part being composed largely of conglomerate; Lower part, mainly of grey-white, grey-green and black-grey tuffaceous sandstones, intercalated with siltstone and conglomerate; Middle part, mainly of purple and grey-green tuffaceous fine-grained sandstone and siltstone, intercalated with many layers of conglomerates, pebble-bearing gritstones and shales; and the Upper part, of purple tuffaceous sandstone and siltstone, intercalated with pebble-bearing volcaniclastic sandstone. It is 300-m to 1520-m thick.
Relationships and Distribution
Lower contact
It is in a conformable contact with the underlying Longmen Fm. However, Huang (2019) states "the Longmen Formation (the so-called Jiulongshan Formation in northern Hebei Province)", therefore this equivalence (?) would also imply a disconformable contact with the underlying Yaopo Fm.
Upper contact
It is in an unconformable or disconformable contact with the overlying Tiaojishan Fm (Lanqi Fm)
Regional extent
The formation is distributed on the Tiaoji Mt of West Hills of Beijing and in the areas to the west of the former such as Miaofeng Mt, Jiulong Mt, Xiangyudaliang, Mao’er Mt, as well as Xiahuayuan of Xuanhua City, Pingquan of Chengde City, Luanping, Chicheng and Funing Counties of northern Hebei. Both its lithology and thickness are changeable in various places. At the southern foot of the Tiaoji Mt and in the area of Datai the formation is exposed Compiler
Jingeng Sha (coordinator), with a thickness of 1000-1520 m, containing a big amount of tuffaceous materials; northerly till the areas of Sangyu and Niuzhan its thickness being of only 300 m; and in the area of the Jiulong Mt its thickness being of only 400 m remaining due to its denudation.
GeoJSON
Fossils
In the areas of Zhouyingzi and Wangyingzi within the Luanping Basin, as well as of Xiaofang-Zhangzi, Liugou District, Chengde City the formation yields insect fossils as represented by Mesobaetis sibirica, Mesoneta antiqua, Samarura gigantean, and Yenliaocorixa chinensis; bivalves fossils: Ferganoconcha sibirica, F. curta, F. subcentralis; plant fossils: Coniopteris hymenophylloides, Sphenobaiera angustifolia, Podozamites lanceolatus; Ostracod fossils: Darwinula sarytirmenensis, D. impudica, Timiriasevia catenularia, T. armeniacumiformis; conchostracan fossils: Triglypta pingquanensis and etc.
Age
Depositional setting
Additional Information
Beginning date (Ma):
Ending stage: Oxfordian
Fraction up in ending stage: 0.5
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information
Compiler
Jingeng Sha (coordinator)