Paper No. 5
Presentation Time: 9:05 AM
CATASTROPHIC CLIMATE WARMING IN THE LATEST PERMIAN TO EARLY TRIASSIC: EVIDENCE FROM OXYGEN ISOTOPES
Oxygen isotope analyses were performed on Late Permian and Earliest Triassic conodonts from Chinese and Armenian sections to document climate changes across the Permian-Triassic boundary (PTB). Late Permian Clarkina
conodont elements from the Meishan GSSP section (South China) have comparable oxygen isotope ratios indicating that both taxa were thriving in comparable and shallow water depths. At the extinction horizon, oxygen isotope ratios of both taxa, Clarkina
, start to decrease by 1.5 and 2‰, respectively. Lowest oxygen isotope ratios are measured in the earliest Triassic. The decrease in the oxygen isotope ratios is confirmed by oxygen isotope analyses on conodonts from the Shangsi section (South China) and translates into significant warming of low latitudinal surface waters by 6 to 8° C. Oxygen isotopes measured on conodonts from two Armenian PTB sections decrease as well by 1.5 to 2‰ in the latest Permian. Calculated absolute temperatures are slightly higher in comparison to South China which is attributed to the equatorial position of Armenia, whereas South China was located in slightly higher subtropical latitudes. Most important, global warming of up to 8° C is indicated by the temperature rise reconstructed in both areas.
The negative shifts in the oxygen isotope ratios coincide with the PTB negative carbon isotope excursion suggesting that major changes in the global carbon cycle probably induced by Siberian trap volcanism and related thermal metamorphism of organic carbon rich sediments resulted in higher greenhouse gas levels and catastrophic global warming. Since reconstructed temperatures start to increase at the extinction horizon, climate warming was probably not a major cause of the latest Permian extinction pulse. However, increasing temperatures may have favored the widespread occurrence of cyanobacterial microbialites as well as oceanic anoxia. Most important, climate warming and very warm temperatures in the Early Triassic are suggested to have played an important role for the Early Triassic extinction as well as timing and pattern of the slow recovery of marine and terrestrial ecosystems in the aftermath of the PT crisis.