T137 Past and Present Global Biotic Crises: From Microbes to Megafauna

Monday, 26 September 2016
1:30 PM - 5:30 PM
Mile High Ballroom 3C

END PERMIAN SALINITY AND OXYGENATION CHANGES IN A SHALLOW MARINE BASIN IN EAST GREENLAND

Paper number: T137-6
Program: Technical Sessions
Time: 2:35 PM – 2:50 PM

Authors

Abstract

The end Permian sequence at Jameson Land (East Greenland) is one of the most extended and complete records of the Permian- Triassic transitions in the world. The site shows a simultaneous collapse of the terrestrial and marine ecosystem. High resolution sampling over a 2.5 m interval (approximately 50-150 kyr) across the extinction event allows for a detailed study of marine environmental and depositional changes. Palynofacies show alternating anoxic and oxic depositional conditions during the biotic crisis. Anoxic deposits are characterized by high amounts of pollen fragments which suggest increased soil erosion, high amounts of amorphous organic matter of both terrestrial and marine origin, and a relatively larger fraction of coastal and freshwater aquatic palynomorphs. This suggests that anoxia is caused by increased runoff and soil erosion leading to water column stratification and anoxic bottom waters. For the first time at this location, changes in groups of aquatic palynomorphs were studied together with changes in the morphology of the acritarch Micrhystridium. Different groups or acritarchs are thought to have different environmental preferences: Micrhystridium prefers coastal or nearshore conditions, Veryhachium is a shelf to open marine group, while Leiosphearidia, Cymatiosphaera and Tasmanites are prasinophytes that are associated with freshwater influx. A shift from a Micrhystridium-Veryhachium assemblage to Micrhystridium-prasinophyte assemblage during the extinction event indicates an increasing freshwater influence at the site. Interestingly, the first anoxic period only starts when the terrestrial and marine biotic crisis are already ongoing, showing that anoxia may have contributed, but did not cause the marine extinction event at this location.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-282875

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