Dynamic process of turbidity current‐induced benthic‐marine oxygenation evidenced by sequential ichnocoenoses: An example from a Late Permian oxygen‐deficient basin

Abstract

Turbidites and associated trace fossil assemblages have been extensively studied in modern and ancient sedimentary basins. However, benthic redox fluctuations induced by turbidity currents and relevant trace fossil suites (oxygen‐related ichnocoenoses) have rarely been demonstrated in geological records. Here, we present an example with a well‐preserved ichnocoenosis succession recording the detailed dynamic process of benthic marine oxygenation generated by turbidity currents in a Permian oxygen‐deficient basin. Millimetre‐ to centimetre‐scale sedimentological and ichnological analyses demonstrated that benthic‐marine oxygenation induced by distal turbidity currents recorded in fine‐grained calciturbidites from the anoxic basin began with a rapid, short‐lived oxygenation event marked by the Thalassinoides/?Scolicia ichnocoenosis, followed by a relative long‐term lower oxygen‐level stage indicated by the ichnocoenoses of Planolites‐Zoophycos and Zoophycos in turn, and ended with returning to the background anoxic benthic conditions represented by the laminated black shale. The sequential ichnocoenoses associated with turbidity current‐induced oxygenation events in the Permian oxygen‐deficient marine basin suggest that turbidity currents can prominently oxygenate anoxic/dysoxic bottom waters and have significant impacts on benthic communities in oxygen‐deficient basins.