Differences between the upper and lower kellwasser events and productivity variations during the Late Devonian Frasnian-Famennian transition in Yangdi of Guilin, south China

Extremely low productivity together with differences between the Lower and Upper Kellwasser events were found during the Late Devonian Frasnian-Famennian transition in the Yangdi section, Guilin, South China, which was paleogeographically situated at platform margin. Analysis of carbonate δ13C, biogenetic Ba, Al, Si and redox sensitive elements show oxic to dysoxic condition in the Lower Kellwasser event period with the small increase of both the primary productivity and the ecosystem ultimate productivity. The slight δ13C positive excursion of the Lower Kellwasser event was caused by the increased productivity. However during the Upper Kellwasser event period the primary productivity increased but the ultimate productivity sharply decreased, which means the great loss of biomass in the ecosystem. The remarkably δ13C positive excursion was controlled by the accumulation of buried organic carbon in the anoxic circumstances with the simultaneous sea-level rise and reduced terrestrial input. ©, 2015, China University of Geosciences. All right reserved.