Chaumitien Fm
Type Locality and Naming
The type section of Kushan Formation is the Tangwangzai (Baoquan Hill)-Fanzhuan section, lying about 2.5 km north of Kushan Town, Changqing County, Jinan City, Shandong Province. It was remeasured, in two sections, by Zhang Zengqi et al. from Shandong Institute and Laboratory of Geological Sciences in 1992. The lower part of the formation was measured along the south slope of the Tangwangzai (116°51’35” E, 36°30’55” N) and the upper part on the east slope of Fanzhuan (116°51’10” E, 36°31’20” N). In the type composite section, the formation is 169.40 m thick. The Chaumitien Formation was named by Blackwelder (1907). The name is derived from Chaumitien (spelled Chaomidian in Hanyu Pinyin) Village in Changqing County, now Changqing District of Jinan City, northwestern Shandong Province. Blackwelder originally called the formation Chaumitien limestone, referring it to the third lithologic unit of his Kiulung group. Subsequently, Sun (1924) divided the formation into two units, based on fossil content, with the lower unit called the informal Chaumitien limestone (for Shandong Province) or Changshan series (for Hebei Province) and the upper unit the Fengshan limestone (for Hebei Province). Lu and Dong (1952), also by fossil content, renamed the two units as Changshanian Series and Fengshanian Series with moving the base of Changshanian Series (the base of Chaumitien limestone) down to the base of the trilobite Chuangia Zone of the Kushan Fm. Lu and Dong’s subdivision had been accepted widely with lowering the series in rank as formal formation by subsequent authors until Zhang and Liu (1996) returned the Chaumitien Formation back to its original concept given by Blackwelder (1907), which is accepted herewith.
Synonym: （炒米店组）
Lithology and Thickness
The Chaumitien Formation is a carbonate sequence that is dominated by grey, medium- to thick-bedded algal limestone, yellowish grey, thin-bedded laminated micritic limestone, purplish grey, thin-bedded edgewise conglomerate, and greyish white, thick-bedded stromatolitic algal-reef limestone, with interbeds of bluish grey, thin-platy limestone, thin-bedded bioclastic limestone, light grey sandy algal limestone, and occasionally with dolomite in the upper part. In the type section, there are five layers of algal-reef limestone.
Relationships and Distribution
Lower contact
The Chaumitien Fm rested conformably on the underlying Kushan Fm. Its lower boundary is defined by the disappearance of shale of Kushan Fm
Upper contact
It is overlain by the overlying Sanshantzu Fm in the type area. The upper boundary by the appearance of large amount of dolomite at the base of Sanshantzu Fm (Sanshanzi Fm)
Regional extent
The Chaumitien Formation is exposed in the Shanxi-Henan-Shaanxi, Xuzhou-Huaibei, Western Shandong, Northern Hebei-Western Liaoning and Liaoning-Jilin areas of North China, distributed, distributed widely in the North China platform, including Liaoning, Hebei, Shandong, southern Jilin, central and southern Shanxi, central Henan, northern Anhui, northern Jiangsu provinces and Inner Mongolia Autonomous Region.
The Chaumitien Formation is of remarkably diachronous, with different ages from place to place. In the Hunjiang River basin in Jilin, the formation consists of thin-bedded to medium-bedded limestone intercalated with shale, 47‒358 m in thickness. In Liaoning, the formation is thicker in the east and thinner in the west, 80‒400 m in thickness. In Hebei, the formation is dominated by striped argillaceous limestone intercalated with a few of breccia and argillaceous siltstone, and is in conformable contact relationship with both the underlying Kushan Fm and the overlying Yehli Fm. Thickest strata in Hebei are about 100‒140 m, known in Yixian, Laiyuan, and Fuping counties and, Tangshan City, but in other places of the province it is only 30‒90 m thick. In Shandong, the formation is characterized by frequent appearance of algal-reef limestone in addition to the crystalline limestone and edgewise conglomerate, with the thickness increasing, from the east to the west, from 50 m to 220 m. In Shanxi, it records the similar lithology and keeps conformable contact relationship with both the Kushan Fm and the Yehli Fm but its thickness is only about 30 m. In the northern Anhui and northern Jiangsu, the formation commonly consists of grey, greyish yellow oolitic dolomitic limestone, striped argillaceous limestone and edgewise conglomerate, but in Xiaoxian County of northern Anhui the unique giant-vortex limestone is present.
GeoJSON
Fossils
Chaumitien Formation yields diverse polymerid trilobites and a few of agnostoid trilobites. The common polymerid trilobites include Changshania, Irvingella, Shirakiella, Dikelocephalites, Maladioides, and Kaolishania from the lower part of the formation, and Asaphellus, Calvinella, Changia, Mictosaukia, Leistegium, Prosaukia, Pseudokoldinioidia, Ptychaspis, Saukia, Tellerina, Tsinania, and Yosimuraspis from the upper part. The common agnostoid trilobites include Homagnostus and Rhaptagnostus. In some localities of western Shandong, Hebei, and Jilin provinces the formation yields graptolites such as Callograptus, Dendrograptus, Dictyonema and Siberiograptus, conodonts such as Cambrooistodus Cordylodus, Eoconodontus and Proconodontus, and nautiloids such as Acaraceras, Eoclarkoceras, Huaiheceras, and Protatinoceras.
Age
Depositional setting
Additional Information