Carbon and oxygen isotopic characteristics of the Ediacaran Doushantuo Formation in Fanjingshan area, northeastern Guizhou Province, China

Abstract

New data of carbon and oxygen isotopes of the Ediacaran Doushantuo Formation from two measured sections in Fanjingshan area, northeastern Guizhou Province are presented in this paper. Carbon isotopes from Tongluo section and Nongjing section intervene between −3.2 and −5.4 ‰, an average value −4.3 ‰ and between −3.6 and +0.5 ‰, an average value −1.5 ‰, respectively; oxygen isotopes range from −7.0 to −11.0 ‰, an average value −9.3 ‰; and from −10.2 to −2.9 ‰, an average value −7.6 ‰, individually. Carbon and oxygen isotopes both display a negative-excursion trend. Carbon isotopes reduce dramatically in the middle of these sections. Average carbon isotope is the most negative from Yongyi section, moderate negative from Tongluo section and less negative from Nongjing section, which is characteristic of a large surface-to-deep ocean δ13C gradient/carbon isotopic stratification during Doushantuo period. The spatio-temporal variations of carbon isotope perhaps should be related to sedimentary facies and the relief of palaeo-ocean floor. Moreover, carbon isotope profiles from three sections in Fanjingshan area, northeastern Guizhou Province could compare to South China elsewhere and make interbasin high-resolution chemostratigraphic correlation possible in South China. The such large-scale carbon negative excursion worldwide must be the interactional result of multi-factors such as overturn of a redox-stratified ocean, extreme chemical weathering, massive oxidation of destabilized methane hydrates, and sudden formation and gradual dissipation of a global meltwater plume caused by sea-level rise during deglaciation.