Friday 22 April, 11 AM CET
DR.YADONG SUN
ABSTRACT: The Triassic (~252-201 Ma) was a time of prominent changes in Earth history. In the ocean, the rise of calcareous nanoplankton, molluscs, scleractinia corals, and marine reptiles marginalised the Palaeozoic ways of life, shaping the marine ecosystem to more complex and better buffered modern ecosystem. On land, warm and arid climates in vast lands of Pangea favoured amniotes over amphibians. The rise of dinosaurs, the diversification of insects, and the origin of early mammals represent new trends of evolution.
The Triassic also saw a series of extinctions and lesser calamities, all of which coincided with major climate changes. However, reconstruction of sea surface temperatures of Triassic seas is challenging due to the paucity of well-preserved fossil materials. The current solution is to measure δ18O from conodonts using either secondary ion mass spectrometry (SIMS) or gas source isotopic ratio mass spectrometry (GS-IRMS). Although both methods have inherited issues, both show an 8-10 °C SST rise across the Permian-Triassic boundary with equatorial SSTs reaching 35-41°C in the Early Triassic. SSTs show a decrease trend through the Middle Triassic, followed by a two-pulsed warming in the Carnian. The Carnian Crisis (~230 Myr) witnessed the reverse of the Pangean climate—the prevailing arid/semi-arid climate was briefly replaced by a humid episode. The Carnian-Norian transition saw a ~7 °C cooling, coincident with a major changeover in reef composition. Although the Norian saw the extensive development of evaporites, the Norian SSTs were mostly in modern day range. The middle to late Norian represent another intra-Triassic hothouse interval with low latitude SSTs >33 °C. The global reef number and diversity plunged at this time. The Rhaetian SSTs are poorly constrained, because of the paucity of conodonts in rocks. Due to the final annihilation of conodont and the selective extinction of calcifiers during the Triassic-Jurassic mass extinction, reconstruction of SSTs for this interval is very challenging and has become the Holy Grail for deep time palaeoclimatologists.