Friday, August 12, 2016

Recovery From the Permian Extinction Delayed by Productivity Crises During Early Triassic

Early Triassic productivity crises delayed recovery from world's worst mass extinction


Grasby et al


The recovery of life after the latest Permian extinction was protracted over Early Triassic time. Detailed geochemistry of marine sections along northwest Pangea indicates that upwelling ceased at the extinction event. Nitrogen stable isotope data suggest that this was associated with progressive increase in nutrient stress throughout the Early Triassic, coincident with a significant decrease in organic carbon content despite pervasive anoxic to euxinic conditions. We argue that the Early Triassic hothouse both reduced marine productivity and deepened the nutricline, reducing the overall rate of nutrient delivery to the photic zone, creating an Early Triassic nutrient gap. When oceans finally cooled by Middle Triassic time, renewed nutrient upwelling and onset of organic-rich shale deposition occurred across northwest Pangea, marking the final return of global marine productivity.

No comments: