气候变化领域集成服务门户

High-resolution isotopic analyses were conducted on core samples from the Ediacaran Doushantuo Formation at the Wangjiapeng section, western Hubei Province in South China, whereby two laterally traceable, negative delta C-13(carb) excursions (EN1 and EN3) were recognized. The magnitude and duration of these excursions permit intra-basinal and inter-basinal correlation, which indicates that they probably represent a global change in seawater composition. The occurrence of decoupled delta C-13(carb)-delta C-13(org) with almost invariable delta C-13(org) values at Wangjiapeng, Zhongling, Yangjiaping sections is consistent with remineralization of a dissolved organic carbon (DOC) pool by means of sulfate reduction, as recorded in EN3. The synchronous presence of EN3, a shift to higher Sr-87/Sr-86 and decrease of Mn and Fe contents and delta N-15 values together points to a glacial influence whereby oxygenation and remineralization of reduced carbon produced C-13-depleted DIC. Glaciations cause a drop in sea level, which itself leads to increased continental shelf area to be exposed to surface weathering, and ultimately to enhanced delivery of radiogenic Sr-87. The increase of Sr-87/Sr-86 ratios, sulfate and phosphate are consequences of surface runoff into oceanic environments and such perturbations induce biogeochemical changes.