Wangyu Fm

No type section was assigned when the unit was erected. Subsequently, Compiling Group for Shaanxi Regional Stratigraphic Scale described briefly a route section of “Lower Cambrian” with 5 lithological beds at Wangyu, the type locality. The section lies about 9 km north of the seat of Yaoshi Township, A section, Lugou section, was measured by Yang et al. (1991), who described the lithology of the formation in more details, although Yang et al. assigned the strata of Wangyu Formation as two new formations, the Caizidi Fm and Lugou Fm. This section may be regard as representative section for the formation. The Lugou section lies at Lugou Gully in Baoluo Township, about 3.5 km north of the junction of Lugou stream and Luohe River, or about 7 km north of Luonan County, Shangluo City, Shaanxi Province (110°46’02”E, 34°08’26”N). It is the upper portion of the same section shared with underlying Shangloucun and Xialoucun formations. In this section, the Wangyu Formation is 560.9 m thick. The Wangyu Formation was named by Regional Geological Survey Team of Geological Bureau of Northwest China (1965). The name is derived from Wangyu Village in Yaoshi Township, Shangzhou District, Shangluo City, southeastern Shaanxi Province.

Synonym: （辋峪组）; By measuring the Lugou section in Luonan County, Yang et al. (1991) erected Caizidi Fm and Lugou Fm to replace the Wangyu Formation. Both the formations are synonymous with Wangyu Formation. Ma (1998, p. 57) regarded the Wangyu Fm to be synonymous with Sanshantzu Fm. Since the Wangyu Formation is an epi-metamorphic sequence, such viewpoint is not followed here.

The Wangyu Formation is a carbonate or an epi-metamorphic carbonate sequence. At Wangyu in Yaoshi Township, the type locality, the formation is dominated by thick-bedded dolomite intercalated with syngenetic calcareous conglomerate, and there is a layer of multi-colored argillaceous dolomite, more than 50 m thick, near the top. In the Lugou section, the Lower part of the formation consists of thick- to mega thick-bedded dolomitic marble and the Upper part consists of thick-bedded siliceous banded dolomitic marble. Extending westward from the type locality to Dajing, Shangzhou District of Shangluo City, the formation there contains interbeds of thin-bedded and lenticular oolitic limestone in middle and upper parts; extending further northwestward to Tielucha, Shangzhou District, the formation consists of dolomitic limestone with minor interbeds of slate in the upper part. The thickness of the formation ranges from 410 to 657 m.

No fossil is known from the formation.