Laocun Fm
Type Locality and Naming
Western Zhejiang. The Laocun Formation was erected by the Zhejiang Regional Geological Survey Team in 1965. The section for the designation is to the south of the Laocun Village of Jiande County of Zhejiang. Lower formation in Jiangde Gr.
Lithology and Thickness
The Laocun Formation is mainly represented by dark purple red clayey siltstone with unstable rhyolitic tuff and small amounts of conglomerate, and yellow green sandstone and siltstone. It varies considerably in thickness, for example, 998 m in Dalingjiao of Pujiang, 200-500 m in the Pailing-Zheshan area, and only 25 m in some parts of the Tianmushan area. In general, it is 1236 m thick. From the Laocu Village to the south of the Chayuan Village, it is in unconformable contact with the Xiuning Formation. In Meicheng of Jiande and in Xizhang of Lanxi, it is in unconformable contact with the Yujianshan Fm.
Relationships and Distribution
Lower contact
Its base marked by gray green sandy and clayey shale is distinguished from the underlying Sinian Xiuning Fm. It contacts with the underlying Xiuning Fm by fault. Regionally, it also disconformably overlies the Yushanjian Fm.
Upper contact
Its top is bounded by the appearance of gray purple massive rhyolite porphyry at the conformable contact to the overlying Huanjian Fm.
Regional extent
The formation occurs in the Shouchang-Linpu and Chunan-Linan areas of northwest Zhejiang. To the west of the line linking Meicheng and Shoufengshan of Jiande, it is dominated by red sedimentary strata, and to the east by volcanic rocks with sedimentary partings. In the Xiaoshan-Linpu area it is almost totally built up by volcanic rocks.
GeoJSON
Fossils
In the Laocun-Genglou area of the Jiande County, it yields bivalves Nakamuranaia chingshanensis; gastropods Probaicalia gerassimovi, Amplovalvata aff. suturalia, A. suturalia anjipingensis; estherias Yanjiestheria sinensis; ostracods Cypridea shouchangensis, Monosulcocypris yunnanensis, M. subovata, Rhinocypris jurassica ; insects Humirysus liucus, Lycoriomima mictis, Linicorixa odota, Orusa barba, Tinactum solusum, Viduata otiosa; floras Otoxamites linguifolius, Coniopteris sp.
Age
Depositional setting
It is of piedmont-fluvial- lacustrine and intermittent volcanic eruptive deposition.
Additional Information