Jiaguan Fm
Type Locality and Naming
Sichuan Basin - west. The Daduhe Geological Team under the Sichuan Bureau of Geology and Mineral Resources erected the Jiaguan bed in 1955. The section for the designation is in Guanyinya of the Jiaguan Town 25 km southwest of the Qionglai County, Sichuan (unpublished).
Lithology and Thickness
The Jiaguan Formation is mainly represented by purple red and brown red thick-bedded massive lithic sandstone, feldspar-quartz sandstone and sub-feldspathic sandstone, with siltstone and mudstone. It is 364.2 m thick. Notably, the Leshan Giant Buddha, which is famous worldwide, was carved from this sandstone.
Relationships and Distribution
Lower contact
Its base marked by purple red thick-bedded conglomerate is distinguished from the purple red mudstone of the underlying Upper Jurassic Penglaizhen Fm. Throughout most of the area the Jiaguan Formation lies disconformably on the underlying Cretaceous Tianmashan Fm or the Upper Jurassic Penglaizhen Fm and in the Guanhua area of Yaan it shows a slightly angular discordance with the latter.
Upper contact
Its top is bounded by the conformably appearance of brown red granule conglomerate at the base of the Guankou Fm.
Regional extent
The formation is widespread in the northwest part of the Sichuan basin and is relatively developed in Qionglai and Lushan. It varies considerably both in lithology and thickness and is coarse in the north and fine in the south and thick in the west and thin in the east. In Guanxian and Chongqing, conglomerate is several hundred meters thick and the formation is 500 m thick; in Qionglai conglomerate is 13 m thick and the formation is 870 m thick; in Yaan conglomerate is 6 m thick and the formation is 715 m thick; and in Chengdu and Leshan conglomerate is less then 10 m thick and the formation is about 200 m thick.
GeoJSON
Fossils
To the south of the Xinjin County, the Jiaguan Formation yields Lepidotus xinjinensis; and in Gaodianzi of the Renshou County, its lower part contains ostracods Zisiphocypris acuta, Cypridea setina acerata, C. setina bellatula, etc.
Age
Depositional setting
It is of fluvial deposition.
Additional Information
Notably, the Leshan Giant Buddha, which is famous worldwide, was carved from this sandstone.