Fushan Fm
Type Locality and Naming
Lu-Zong (Lujiang-Zhongyang) volcanic basin. Fushan Geopark is a caldera composed of trachytic volcanic rock that is located in Zongyang County, Anhui Province. The name of the Fushan Formation was given by the No 317 Geological Team (1969) in Fushan of the Congyang County, Anhui. The type locality is in Guanqiao of the Congyang County, represented by the Longchengshan section (30º51', 117º16').
Synonym: Fushan Gr
Lithology and Thickness
The Fushan Formation is composed of purple red, brownish grey trachyte, trachytic tuff, trachytic tuffaceous breccias, and andesite, intercalated with tuffaceous siltstone. It is 242 to 450 m thick.
Relationships and Distribution
Lower contact
This formation disconformably contacts with the underlying Shuangmiao Fm.
Upper contact
This formation unconformably contacts with the overlying Pukou Fm or younger strata.
Regional extent
Lu-Zong (Lujiang-Zhongyang) volcanic basin. It occurs in the Lujiang, Fanchang, Congyang and Tongling areas. "The Lu-Zong (Lujiang-Zongyang) basin is one of the most important volcanic basins in the middle and lower reaches of the Yangtze River area, China. It comprises four shoshonitic volcanic units, which are, in an ascending order, the Longmenyuan, Zhuanqiao, Shuangmiao and Fushan Groups. The LA-ICP MS U-Pb zircon ages [as of 2008] of the four units are: 134.8±1.8 Ma for the Longmenyuan Gr, 134.1±1.6 Ma for the Zhuanqiao Gr, 130.5±0.8 Ma for the Shuangmiao Gr, and 127.1±1.2 Ma for the Fushan Gr. The results indicate that all volcanic rocks in the Lu-Zong basin were formed in the Early Cretaceous from about 135 Ma to 127 Ma, lasting 8–10 Myr. There were no Jurassic volcanic activities in all the volcanic basins including the Lu-Zong basin in the middle and lower reaches of the Yangtze River area." (Zhou, T., Fan, Y., Yuan, F. et al. Geochronology of the volcanic rocks in the Lu-Zong basin and its significance. Sci. China Ser. D-Earth Sci. 51, 1470–1482 (2008). https://doi.org/10.1007/s11430-008-0111-7)
GeoJSON
Fossils
The formation yields Spore and pollen Tumoripollenites minor, Annulispors jiangsiensis，Classopollis, C. parvus, Klukisporites, Elytranthite, Pinuspollenites labacus, Subtriporiporllenites granulatus, Polypodiaceoisporites.
Age
Depositional setting
This is a caldera.
Additional Information
It is a typical rock of the late eruption of the volcanic zone in the middle section of the Yangtze River. The erupted rocks in the Fushan eroded caldera have a circular distribution. A bell-shaped mound is located in the centre, which is a product of volcanic activity after subsidence of the caldera. Therefore, the Fushan caldera is a reactivated caldera. Because of the geological and petrological characteristics of this caldera, features such as overlapping peaks, cliffs, stone corridors, unique rocks, unique caves and natural bridges have formed. They have geological significance and aesthetic value, and they blend with the scenery of the adjacent valleys, streams and lakes. Fushan is one of the five famous mountains in Anhui Province and is also a national geopark.