2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 9
Presentation Time: 10:15 AM

Mantle Plumes and Phanerozoic Biological Crises: Application to the Permian – Triassic Boundary Mass Extinction

HEYDARI, Ezat, Department of Physics, Atmospheric Sciences, and Geoscience, Jackson State University, P.O. Box 17660, 1400 Lynch Street, Jackson, MS 39217, ARZANI, Nasser, Department of Geology, University of Payame-Nour, Kohandej Street, Esfahan, Iran and HASSANZADEH, Jamshid, Dept. of Geology, Univ. of Tehran, Tehran, Iran, ezat.heydari@jsums.edu

We present characteristics of three Permian – Triassic boundary (PTB) sections from Shahreza (Iran), Julfa (Iran), and Chaotian (China) and propose that the biological crisis, observed sedimentological-mineralogical-geochemical changes, and the eruption of Siberian Traps flood basalt were the consequence of a complex perturbation caused by a mantle plume.

The injection of igneous dike swarms into the continental margin facilitated the release of CH4 from the dissociation of marine gas hydrates, the maturation of organic-rich sediments, and the fracturing of hydrocarbon reservoirs. Aerobic oxidation of methane in the water column created major changes in seawater including low pH, high concentrations of CO2 - Ca2+ - HCO3-, and low CO32- values. Combined with a hot seawater temperature, these changes made calcification of marine organisms difficult and produced major physiological crisis including reduced metabolic rates, high sensitivity to environmental stress, and hampered growth and reproduction.

Feeder dikes from the mantle plume formed the Siberian Traps flood basalt releasing CO2 and SO2. Comtemporaneously, gas-charged oceans released large volumes of CO2 and CH4 into the atmosphere. These created the end-Permian inferno facilitating the terrestrial mass extinction due to environmental stress and loss of habitat.

Cessation of the plume activity during Early Triassic stopped the release of CH4 and terminated continental flood basalt eruption ending the environment of death on land and in sea. Carbonate saturation of seawater increased instantly resulting in extensive seafloor cementation. It also resulted in the deposition of marine carbonates by microbial activities in the hostile post-extinction environment.

From the trigger to the recovery, the PTB perturbation that also included the mass extinction could have lasted for at least 2 Myr. With some modifications the model can also be applied to other mass extinctions of the Phanerozoic which are associated with flood basalt eruptions.