Organic carbon isotope values from the Late Permian Seis/Siusi succession (Dolomites, Italy): Implications for palaeoenvironmental changes

Abstract. The Permian-Triassic boundary is marked by a globally prominent negative carbon isotope excursion traceable in marine carbonates and organic matter. In the shallow marine carbonate succession at Seis/Siusi (Dolomites, Italy), the δ¹³C_carb and δ¹³C_org signatures follow the general Permian-Triassic boundary carbon isotope trend, but the δ¹³C_org values are slightly less depleted in ¹³C in two episodes representing restricted lagoonal environments and in the period around the Tesero Oolite Horizon. This isotopically less depleted organic matter in the lagoons is interpreted to be most likely caused by poor oxygen ventilation and/or slightly modified salinity which may have led to restricted bioproductivity and increased hence the relative amounts of continental-sourced organic matter. In addition, elevated riverine influx and supply of terrestrial organic matter, perhaps triggered by a wet period, might be the cause for the relatively less depleted ¹³C in the organic matter around the Tesero Oolite Horizon and in overlying sediments.

doi:10.1002/mmng.201100008