The 5th International Conference of Geobiology

The largest extinction in Earth history, in the latest Permian, was followed by the Early Triassic Hothouse, characterised by a prolonged period of ecologic recovery. During this time there was a single supercontinent Pangea and the global Panthalassa Ocean. As in the modern, the Coriolis effect would have driven primary productivity preferentially by Ekman upwelling in areas of eastern boundary currents – or along the western margin of Pangea. Here records show reductions in organic matter deposition despite strongly developed anoxia. N isotope records show evidence for a progressive decline in N availability throughout the Griesbachian and Dienerian, leading to severe nutrient limitations throughout the remainder of the Early Triassic, consistent with the paucity of organic rich shales globally. The Middle Triassic was characterised by cooling from hothouse conditions. During this time western Pangea is characterised by deposition of organic rich phosphorites that form major petroleum source rocks. Nitrogen isotope records indicate a return to more normal upwelling of nutrient rich waters and bioproductivity at this time. Results suggest that high ocean temperatures of the Early Triassic depressed the marine nutricline, creating a nutrient trap that limited marine primary productivity. Highly productive continental margins returned to western Pangea only in response to final global cooling.

global warming; primary productivity, permian extinction, early Triassic