Nanxiangshan Fm
Type Locality and Naming
It was named by Ju Kuixiang in 1985, and was first cited publicly by Wu Qiqie and others in 1986. The naming section is located at Nanxiang Mt in the vicinity of the Qixia Mt in the eastern suburbs of Nanjing City, Jiangsu Province, with its reference section being situated in the West Mt of Cangbomen, Nanjiang City.
Synonym: （南象山组）; Zhongshan Fm (used by Huang, 2019, as equivalent).
Lithology and Thickness
Lower part is composed of medium-, and coarse-grained feldspar-quartz sandstones, pebble-bearing sandstones, sandy shales, quartzitic sandstones, carbonaceous shales and coal seams or coal beds, with its basal part being possessed of a layer quartzitic conglomerates or sandy conglomerates, with a thickness of about 527 m. Upper part is composed of grey-white and grey-yellow medium-, and fine-grained arkose quartz-sandstones, quartz-sandstones, lithic sandstones and siltstones, intercalated with shales, carbonaceous shales, coal beds and clay layers, with a thickness of about 527 m.
Relationships and Distribution
Lower contact
Its basal part is in a disconformable contact with the underlying upper Triassic Fengjiatang Fm. Huang (2019) implies that the early-Early Jurassic is absent at this hiatus.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Beixiangshan Fm
Regional extent
The formation is distributed mainly in the areas of Nanjing City and Jiangning Town, with its scattered exposures being found to the east of the Longtan Deep Pool and to the south of Zhenjiang City. As in the areas of Changzhou City, Jiangdu and Funing the formation can only be seen in some drilling wells. Based on the observations carried out in various regions one can see that lithologically the formation is characterized by coarser grains of the clastics and poor coal-bearing capacity in its lower part, and finer grains of its clastics, better coal-bearing capacity and greater lateral variations in its upper part. The maximum thickness of the formation is found to be of 680 m in the Nanjing City and Jiangning area, commonly being of 300 m-400 m. In the Yuntai Mt its thickness is of over 458 m, with its thickness getting smaller easterly, as in the area of the Shifo Nunnery being of about 170 m, while to the east of Longtan region being of only tens of meters.
GeoJSON
Fossils
It yields bivalve fossils as represented by the Tutuella-Sibireconcha-Pseudocadinia assemblage and plant fossils as represented by the Todites princeps-Ptilophyllum assemblage of the Dictyophyllun-Clathropteris flora.
Age
Depositional setting
The formation belongs to fluvial, lacustrine and swamp-facies deposits.
Additional Information