Sanshantzu Fm
Type Locality and Naming
No type section was assigned when Xie (1932) erected the lithologic unit. An auxiliary section, the Zhaishan section, was proposed as representative section of the formation by Xu (1997) (117°25’ E, 34°27’N). The section is located at Zhaishan Village, 2 km northwest of Jiawang, or 4 km northwest of the seat of Daquan Township, Tongshan County, northwestern Jiangsu Province. It was measured by No. 5 Geological Team of Jiangsu Province in 1974. In this section the Sanshantzu Formation is 199.59 m thick. The Sanshantzu Formation was named by Xie (1932). The name is derived from Sanshantzu (spelled Sanshanzi in Hanyu Pinyin) Hill, about 3 Km southeast of Daquan residential area, Jiawang District, Xuzhou City, northern Jiangsu Province. Originally the formation was called Sanshantzu limestone, and was subsequently renamed as Sanshantzu Formation by Compiling Committee for Geology of China and the Institute of Geology of Chinese Academy of Geological Sciences (1956).
Synonym: （三山子组）; Sanshanzi Fm
Lithology and Thickness
The Sanshantzu Formation is a carbonate sequence comprising mainly dolomite. In the type area, the formation is divided roughly into two parts. Lower part, 10 to 100 m thick, consists of yellowish grey, greyish yellow, thin-bedded powder- to fine-crystalline dolomite, alternated with light brown, thin-bedded, fine-crystalline argillaceous dolomite with a number interbeds of fine-crystalline edgewise dolomite conglomerate; Upper part, 2 to 33 m thick, consists of light grey, medium- to thick-bedded, fine-crystalline dolomite with cherty nodules.
Relationships and Distribution
Lower contact
The Sanshantzu Fm rests conformably on the limestone of Chaumitien Fm.
Upper contact
It is overlain disconformably by either the Majiagou Fm or the Chiawang Fm, both of which have grey yellow, thin-bedded conglomerate at base, which evidently defines the upper boundary of the Sanshantzu Fm.
Regional extent
The Sanshantzu Formation is exposed in the Western Margin, Shanxi-Henan-Shaanxi, and Western Shandong areas North China Region, distributed widely in northern Jiangsu, northern Anhui, central Henan, western Shandong provinces and northern Ningxia Hui Autonomous Region. It is characterized by having stable lithology and by having the lower boundary notably diachronous from place to place. In general, the lower boundary of the formation rises gradually in horizon from south to north on-North China platform.
GeoJSON
Fossils
In the auxiliary Zhaishan section, the Sanshantzu Formation yields polymerid trilobites Mictosaukia, Saukia, and Tellerina; conodonts Acodus, Cordylodus, Drepanodus, Hirsutodontus, Oneotodus and Proconodontus, and brachiopod Eoiorthis. In addition, the formation in Zichuan County of Shandong Province yields cephalopod Barnesoceras. The abovementioned assembles are Furongian in age. Damesellid trilobite Blackwelderia has been found from the formation in Dengfeng, central Henan Province, and in Longxian, Qishan and Hancheng counties of Shaanxi Province, indicating the formation also embraces strata of latest Guzhangian age.
Age
Depositional setting
The formation represents sediments of enclosed platform facies and tidal flat‒lagoon facies.
Additional Information