T169 Mass Extinctions: Volcanism, Impacts, and Catastrophic Environmental Change I

Monday, 20 October 2014
1:00 PM - 5:00 PM
223/224

ABRUPT SURFACE WATER REDUCTION DURING THE END-PERMIAN MASS EXTINCTION AND COMBUSTION OF OIL BY THE END-CRETACEOUS ASTEROID IMPACT

Paper number: T169-7
Program: Technical Sessions
Time: 2:20 PM – 2:35 PM

Authors

Abstract

Ocean redox structure throughout the water column in the low-latitude ocean before, during, and after the largest mass extinction in the Earth’s history at the end of the Permian was estimated based on surface sediment redox indicators of sedimentary organic molecules and/or euxinia-sensitive rare earth elements from sections representing shallow surface, deep surface, intermediate, and deep waters. The new and published data show gradual reductions in deep water in the low-latitude Panthalassic Ocean from the late Changhsingian to the Griesbachian and abrupt reductions in surface water in the low-latitude Panthalassic Ocean and Paleotethys Sea during the mass extinction. The deep water redox environment worsened even more after the end-Permian mass extinction, but surface water redox conditions were worst during the mass extinction. These findings suggest that the deterioration of the deep water environment was due to a temperature increase spanning the mass extinction, which was not a cause of the mass extinction, and that the abrupt reductions in the surface water was a cause of the mass extinction.

We also show that the asteroid impact at the end-Cretaceous resulted in the ejection of combusted and non-combusted fossil organic matter such as oil, most of which fell into the ocean and was transported by the impact-induced tsunami. The remaining combusted and non-combusted fossil organic matter remained in the stratosphere, along with atomic elements sourced from the asteroid, for a period of a year, during which devastation of land vegetation occurred. Combusted organic molecules (coronene) are now condensed in the tsunami deposits and the superjacent layer containing condensed iron and iridium sourced from the asteroid at Beloc, Haiti. The percentage of coronene in total combusted organic molecules is exceptionally high in the tsunami deposits and iridium layer, suggesting that the combusted organic molecules remained in the stratosphere for a year. Low carbon preference index (CPI) values of n-alkanes in the tsunami deposits and iridium layer relative to other strata, suggesting that the n-alkanes in the tsunami deposits and the iridium layer were sourced mainly from oil. Combusted oil molecules such as coronene suspended in the stratosphere may have contributed to the darkness.