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TitleEarly Triassic Productivity Crises Delayed Recovery from World's Worst Mass Extinction
AuthorGrasby, S E; Beauchamp, B; Knies, J
SourceGeology vol. 44, no. 9, 2016 p. 779-782, https://doi.org/10.1130/G38141.1
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20160080
PublisherGeological Society of America
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut; Northwest Territories
NTS120; 29; 340; 39; 49; 540; 59; 69; 79; 89
AreaArctic
Lat/Long WENS-120.0000 -56.0000 84.0000 76.0000
Subjectsmarine geology; paleontology; nitrogen; stable isotope studies; organic carbon; shales; organic materials; marine ecology; permian extinction; anoxic conditions; euxinic conditions; hothouse; photic zones; nutrient upwelling
Illustrationslocation maps; geological sketch maps; graphs; cross-sections, stratigraphic
ProgramWestern Arctic, High Arctic LIP, GEM2: Geo-mapping for Energy and Minerals
AbstractThe recovery of life after the Latest Permian Extinction was protracted over Early Triassic time. Detailed geochemistry of marine sections along NW Pangea indicates 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 hot house both reduced marine productivity as well as 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 NW Pangea, marking the final return of global marine productivity.
Summary(Plain Language Summary, not published)
This study examined petroleum source rocks in Arctic Canada and noted a significant depletion of organic matter in shales for 4-9 million years following the Latest Permian Extinction Event. Other data suggests that extreme global warming at that time inhibited upwelling of nutrient rich waters which in turn limited marine primary productivity. Effectively the oceans were starved of food and may be why higher life took an extraordinary long time to recovery after the extinction. World oceans finally cooled and upwelling restarted in the Middle Triassic. This delivery of deep nutrient rich waters to the shallow ocean created a burst of marine production and led to formation of significant petroleum source rocks throughout the Arctic (Alaska, Canada, Barents Sea.
GEOSCAN ID298842