Rapid emplacement of the Central Atlantic Magmatic Province as a net sink for CO ₂

TY - JOUR

T1 - Rapid emplacement of the Central Atlantic Magmatic Province as a net sink for CO 2

AU - Schaller, Morgan F.

AU - Wright, James D.

AU - Kent, Dennis V.

AU - Olsen, Paul E.

N1 - Funding Information: We are particularly grateful to Jay Quade for his helpful discussion, Linda Godfrey for her technical lab assistance, Randy Steinen and Margaret Thomas for access to the Park River drainage project geotechnical cores, Noam Bergman for providing COPSE code, Roy Schlische for reviewing an early draft of this manuscript, and the two anonymous reviewers for their helpful critique. This research was supported by 2009 GSA and SEPM Graduate Research Awards (MFS), and an NSF grant EAR 0958867 (JDW and DVK). Lamont-Doherty Earth Observatory Contribution #0000.

PY - 2012/3/15

Y1 - 2012/3/15

N2 - Recent evidence from the ~201.5Ma Central Atlantic Magmatic Province (CAMP) in the Newark rift basin demonstrates that this Large Igneous Province produced a transient doubling of atmospheric pCO 2, followed by a falloff to pre-eruptive concentrations over ~300kyr. This paper confirms the short-term findings from the Newark basin, and tests the million-year effects of the CAMP volcanism on Early Jurassic pCO 2 from strata in the corollary Hartford basin of Eastern North America (ENA) also using the pedogenic carbonate paleobarometer. We find pCO 2 levels for pre-CAMP background of 2000±700ppm (at S(z)=3000±1000ppm), increasing to ~5000±1700ppm immediately above the first lava flow unit, consistent with observations from the Newark. The longer post-extrusive Portland Formation of the Hartford basin records a fourth pulse of pCO 2 to ~4500±1200ppm, about 240kyr after the last lava recorded in the ENA section. We interpret this fourth increase as due to a major episode of volcanism, and revise the main CAMP duration to 840±60kyr. The Portland also records a post-eruptive decrease in pCO 2 reaching pre-eruptive background concentrations of ~2000ppm in only ~300kyr, and continuing to levels below pre-CAMP background over the subsequent 1.5Myr following the final episode of eruptions. Geochemical modeling (using modified COPSE code) demonstrates that the rapidity of the pCO 2 decreases, and fall to concentrations below background can be accounted for by a 1.5-fold amplification of the continental silicate weathering response due to the presence of the CAMP basalts themselves. These results demonstrate that a continental flood basalt capable of producing a short-term perturbation of the carbon system may actually have an overall net-cooling effect on global climates due to a long-term net-decrease in pCO 2 to below pre-eruptive levels, as previous models have suggested followed the emplacement of the Deccan Traps.

AB - Recent evidence from the ~201.5Ma Central Atlantic Magmatic Province (CAMP) in the Newark rift basin demonstrates that this Large Igneous Province produced a transient doubling of atmospheric pCO 2, followed by a falloff to pre-eruptive concentrations over ~300kyr. This paper confirms the short-term findings from the Newark basin, and tests the million-year effects of the CAMP volcanism on Early Jurassic pCO 2 from strata in the corollary Hartford basin of Eastern North America (ENA) also using the pedogenic carbonate paleobarometer. We find pCO 2 levels for pre-CAMP background of 2000±700ppm (at S(z)=3000±1000ppm), increasing to ~5000±1700ppm immediately above the first lava flow unit, consistent with observations from the Newark. The longer post-extrusive Portland Formation of the Hartford basin records a fourth pulse of pCO 2 to ~4500±1200ppm, about 240kyr after the last lava recorded in the ENA section. We interpret this fourth increase as due to a major episode of volcanism, and revise the main CAMP duration to 840±60kyr. The Portland also records a post-eruptive decrease in pCO 2 reaching pre-eruptive background concentrations of ~2000ppm in only ~300kyr, and continuing to levels below pre-CAMP background over the subsequent 1.5Myr following the final episode of eruptions. Geochemical modeling (using modified COPSE code) demonstrates that the rapidity of the pCO 2 decreases, and fall to concentrations below background can be accounted for by a 1.5-fold amplification of the continental silicate weathering response due to the presence of the CAMP basalts themselves. These results demonstrate that a continental flood basalt capable of producing a short-term perturbation of the carbon system may actually have an overall net-cooling effect on global climates due to a long-term net-decrease in pCO 2 to below pre-eruptive levels, as previous models have suggested followed the emplacement of the Deccan Traps.

KW - Atmospheric carbon dioxide

KW - CO chemical weathering

KW - Large Igneous Province

KW - Triassic-Jurassic

UR - https://www.scopus.com/pages/publications/84856992907

UR - https://www.scopus.com/pages/publications/84856992907#tab=citedBy

U2 - 10.1016/j.epsl.2011.12.028

DO - 10.1016/j.epsl.2011.12.028

M3 - Article

SN - 0012-821X

VL - 323-324

SP - 27

EP - 39

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

ER -