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Depositional environments of the Carboniferous-Permian Taiyuan Formation (southern North China Block) as deduced from trace elements and from carbon and oxygen isotopes

Lv Dawei, Hu Guangqing, Van Loon Antonius Johannes, Wu Dun

Geological Quarterly

2021

Vol. 65, No. 1

art. no. 1

Limestone layers are extensively developed in the continental/ocean transitional Taiyuan Formation. This formation accumulated on the southern North China Block. The precise environmental conditions of the Taiyuan Formation are still controversial. More information about these topics is presented here on the basis of the analysis of trace elements (Mo, V, Cd, Cr, U, Th), which can be used to determine characteristics of the depositional environment, and of carbon and oxygen isotopes (δ13C and δ18O) in limestone samples from the Huainan Coal Basin. Samples were taken for the purpose from cores of all 13 limestone levels, obtained from a coal-exploration borehole (code P2) in the Huainan Coal Basin. It was found that the δ18O values show a decreasing trend, suggesting a gradual rise of the sea level in a warm climate. Three negative shifts of δ13C appear in a lower, a middle and an upper limestone layer, accompanied by relative enrichment of the redox-sensitive elements (Cd, Cr, Mo and V). These three layers are thus deduced to have been deposited in a warm climate with a high sea level and with more terrigenous input than during deposition of the other limestone layers. The redox elements and elemental ratios (V/Cr, Th/U) in the limestones suggest deposition in an oxygen-rich sea with high salinity.

Sedimentary facies, ichnofossils and storm deposits in the Lower Permian Taiyuan Formation, Jiaozuo city, Henan Province, central China

Hu B., Song H., Liu S., Zhang L.

Acta Geologica Polonica

2010

Vol. 60, no. 1

45-52

Five sedimentary facies - neritic carbonate platform, lagoon, tidal flat, swamp and barrier island facies - are recorded in the Lower Permian Taiyuan Formation along with abundant ichnofossils. Common ichnofossils in this formation include Zoophycos villae, Zoophycos brianteus, Nereites cf. missouriensis, Chondrites isp., Gordia marina, Taenidium isp., Thalassinoides isp., Palaeophycus isp., Planolites isp. and a kind of bifurcation trail. From observations of the morphology of Zoophycos spreiten in approximately vertical sections, at least three kinds of spreite laminae are distinguished: ligular, crescentic and rectangular forms. Four types of storm deposits (coded as A, B, C, D) are recognised in the carbonates of the Taiyuan Formation and can be explained forming in shallow marine environments, which are distributed in order from near storm wave base to near fair weather wave base respectively.