THE MARINE d34S TREND FROM THE UPPERMOST PERMIAN AND PTB INTO THE LOWER TRIASSIC: HUGE, ALMOST INSTANT OSCILLATIONS SUPERIMPOSED ON A PROFOUND RISE AS EVIDENCE OF A CRISIS?

The Permian - Triassic boundary marks the severest mass extinction in earth history. More than 90% of all skeleton building species became extinct in this event. Despite numerous investigations the responsible mechanisms still are not unequivocally identified. Among the more popular hypotheses are bolide impact, global warming, global cooling, global ocean water poisoning, marine anoxia and volcanism. To identify relevant processes during this unusual period geochemical proxies are investigated.

Sulphur isotope data of evaporites from the uppermost Permian to the Lower Triassic from the Mazzon drill core in the Dolomites (Northern Italy) and other localities are investigated and compared. The curve shows low values in the uppermost Permian and the basal Lower Triassic and increases steeply to significantly enriched values in the vicinity of the Dienerian-Smithian Boundary. The sulphur isotope values remain elevated for the Smithian and most of the Spathian substages of the Lower Triassic.

The evaporite isotope data does not fit with results from the literature of carbonate associated trace-sulphate (CAS) and pyrite sulphur isotope data indicating huge and repeated oscillations from depleted to enriched values in the investigated interval. The available data make it appear plausible that CAS and (diagenetical) pyrite isotope data not always represent primary marine signals.

Changes in ocean circulation are the most plausible causes for the presented isotope curve. A more detailed curve needs to be established to exactly pinpoint the changes, however, the currently available curve does not show concomitant changes with the variations of the carbon isotope curve, indicating that different processes were influencing the respective isotope curve shapes.