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.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science
- Atmospheric carbon dioxide
- CO chemical weathering
- Large Igneous Province