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

Susann Siegert,Sonja H Kraus,Ulrich Struck,Christoph Korte,Wolfgang Mette

doi:10.1002/mmng.201100008

Abstract

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 δ13Ccarb and δ13Corg signatures follow the general Permian-Triassic boundary carbon isotope trend, but the δ13Corg 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:<a href="http://dx.doi.org/10.1002/mmng.201100008" target="_blank">10.1002/mmng.201100008</a>

Highlights

The Palaeozoic-Mesozoic transition is marked by the severest mass extinction in Earth history which took place in the latest Permian and affected both marine and continental biota (e.g., Schindewolf 1953; Sepkoski 1989; Raup 1991; Kozur 1998a, 1998b; Jin et al, 2000; Benton & Twitchett 2003; Erwin 2006; Peng & Shi 2009). This event was accompanied by major perturbations in the global carbon cycle marked by a prominent negative d13C excursion across the Permian-Triassic boundary (PTB) (e.g., Chen et al 1984; Holser & Magaritz 1987; Holser et al 1989; Krull et al 2000; Twitchett et al 2001; Korte et al 2004, 2010; Retallack et al 2005; Algeo et al 2007; Yin et al 2007; Heydari et al 2008), followed by distinct positive and negative fluctuations in the Early Triassic (e.g., Atudorei 1999; Tong et al 2002, 2007; Payne et al 2004; Korte et al 2005; Galfetti et al 2007; Horacek et al 2007)
For the PTB, parallel trends in carbonate and organic matter d13C are reported for bulk organic matter and carbonate samples from some sections in the Alps and in Kashmir (e.g., Magaritz et al 1992; Sephton et al 2002; Algeo et al 2007), but in other successions in Iran, Slovenia and China, deviating trends have been traced (e.g., Korte et al 2004; Schwab & Spangenberg 2004; Zhang et al 2006; Riccardi et al 2007; Yin et al 2007)
It is further clear that the organic matter carbon isotopes, in comparison to the carbonate carbon isotopes, are less depleted in 13C in the three parts of the section between samples 22 and 29, between samples 34 and 44, and around the Tesero Oolite Horizon (TOH) (Figs 3, 4)

Summary

Introduction

The Palaeozoic-Mesozoic transition is marked by the severest mass extinction in Earth history which took place in the latest Permian and affected both marine and continental biota (e.g., Schindewolf 1953; Sepkoski 1989; Raup 1991; Kozur 1998a, 1998b; Jin et al, 2000; Benton & Twitchett 2003; Erwin 2006; Peng & Shi 2009) This event was accompanied by major perturbations in the global carbon cycle marked by a prominent negative d13C excursion across the Permian-Triassic boundary (PTB) (e.g., Chen et al 1984; Holser & Magaritz 1987; Holser et al 1989; Krull et al 2000; Twitchett et al 2001; Korte et al 2004, 2010; Retallack et al 2005; Algeo et al 2007; Yin et al 2007; Heydari et al 2008), followed by distinct positive and negative fluctuations in the Early Triassic (e.g., Atudorei 1999; Tong et al 2002, 2007; Payne et al 2004; Korte et al 2005; Galfetti et al 2007; Horacek et al 2007).

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Discussion

Conclusion