Stable Isotopic Evidence of the pCO2 Response to the Central Atlantic Magmatic Province

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Stable isotopic evidence of the pCO2 and temperature response to the Central Atlantic Magmatic ProvinceJames Wright and Dennis Kent, Rutgers UniversityEAR-0958867ABSTRACTOur planet is habitable because the carbon cycle maintains a balance between the supply and the consumption of atmospheric pCO2. Plate tectonics influence the long-term (105 yr.) cycling of carbon, controlling both the rate of volcanic CO2 outgassing and the removal of CO2 through the exhumation of weatherable rocks. Earth has undergone several periods of large-scale volcanic eruptions termed Large Igneous Provinces (LIPs). Three of the largest and most recent LIPs are the Deccan Traps at 65 Myr, Central Atlantic Magmatic Province (CAMP) at ~200 Myr, and Siberian Traps at ~250 Myr. Various researchers have postulated that volcanic outgassing associated with the emplacement of each LIP led to large-scale environmental/climatic changes, which are closely linked to mass extinctions and subsequent evolutionary recovery. However, a major tenet of these hypotheses, that large-scale outgassing is associated with LIPs, has yet to be demonstrated. Here, PIs will reconstruct atmospheric CO2 levels using stable isotope measurements from sediments deposited before, during, and after the emplacement of the CAMP. They make use of a ?paleo-barometry? method that is based on stable carbon isotope values in both the inorganic and organic phases of paleosols (e.g., Cerling et al. 1999). Variations in the carbon isotope values respond directly to the levels of CO2 in the atmosphere. In the Newark and Hartford Basins, numerous paleosol horizons are found interbedded with igneous rocks of the CAMP; such superposition combined with cycle stratigraphy allows very little age uncertainty. These paleosol isotope reconstructions will test the hypothesis that atmospheric pCO2 increases with LIP emplacements. An under appreciated consequence of LIP emplacement is that well after the initial injection of CO2, long-term weathering of the CAMP rocks may lower atmospheric CO2 below pre-event levels. PIs sampling strategy will collect data to test whether chemical weathering of CAMP volcanic rocks resulted in a long-term decrease in pCO2.