Hailongjing Fm
Type Locality and Naming
Basins offshore NE Zhejiang. The type section is in the 3096-2130 m interval of Longjing No. 1 well located at the Longjing tectonic belt in the continental shelf of East China Sea. Geographical coordinates of the type section: 30°10′10″N, E126°05′07″E (GPS). It was named and surveyed by Shanghai Comprehensive Marine Geological Party, Ministry of Geology and Mineral Resources in 1981.
Synonym: It is also called ‘Longjing Fm’ (或称龙井组) on some occasions, which is improper because Longjing Fm is already used to describe a Mesozoic formation in Jilin Province.
Lithology and Thickness
Lower part of the formation is characterized by the interbedded strata of grey mudstones, silty mudstones, and greyish-white muddy siltstones, fine sandstones, intercalated with greyish-black shales and brown coals. Upper part of the formation is characterized by greyish-green mudstones and silty mudstones, light grey siltstones and fine sandstones, intercalated with greyish-black shales and brown coals. The bottom of the formation is characterized by greyish-white massive fine sandstones. The thickness changes greatly laterally.
It is the principal gas-bearing horizon in the East China Sea continental basin.
Relationships and Distribution
Lower contact
The Hailongjing Fm is in faulted contact with the underlying Huagang Fm or in unconformable contact with the underlying Eocene Oujiang Fm (?, the Oujiang Fm is in basin North of Taiwan)
Upper contact
The Hailongjing Fm is in conformable or partly unconformable contact with the overlying YuquanNeogene Fm.
Regional extent
The Hailongjing Fm is distributed in the eastern Zhejiang hollow of the East China Sea continental basin. In the Longjing area alternating sandstone and mudstone dominated by fluvio-lacustrine deposits are up to 900–1000 m thick; in the Pinghu and Gushan areas the formation consisting of coarse clastic rocks dominated by fluvio-lacustrine deposits with mudstone and minor coal is not thick, being 300–500 m in thickness; in the Yuquan and Tianwaitian areas the lithology is relatively thin, probably belonging to lakeshore-shallow-lake deposits, and the thickness is highly varied, being 330–880 m thick.
GeoJSON
Fossils
Sporopollen assemblage: Sporotrapoidites minor -Pinu spollenites- Abietineae pollenites. Stoneworts: Sphaerochara inconspicua and Krassavinella lagenalis. Foraminifera: Spirosigmoilinella compressa. Ostracodes: Amplocypris daxiansis.
Age
Depositional setting
Fluvio-lacustrine deposits.
Additional Information