Atmospheric CO2 estimates based on Gondwanan (Indian) pedogenic carbonates reveal positive linkage with Mesozoic temperature variations

Abstract

CO 2 is an important greenhouse gas that is known to drive global climatic changes. Multiple studies tracking p CO 2 changes throughout the Phanerozoic have highlighted the linkage between CO 2 levels and the corresponding icehouse-greenhouse conditions. However, deviations from the above relationship due to inconsistencies in p CO 2 estimation, as well as large time-steps in existing geochemical models and gaps in proxy data suggest that the paleo- p CO 2 record is not always well-constrained. Here, we attempt to reconstruct atmospheric CO 2 concentration for parts of the late Early and Middle Triassic and Early Cretaceous from several carbonate-forming paleosols of the Indian Gondwana. We measured the carbon isotopic composition of pedogenic carbonates (δ 13 C carb ) and organic matter occluded within soil carbonates (δ 13 C org ) from Pachmarhi, Denwa, and Bagra Formation of the Satpura Basin ( n = 60) to estimate CO 2 using a pedogenic carbonate-based paleo-barometer. The late Early Triassic (Olenekian) shows low CO 2 concentrations (562 ± 426 ppmV), which is followed by an increase (822 ± 523 ppmV) in the Middle Triassic (Anisian). The Early Cretaceous is found to have the highest average concentration (1517 ± 594 ppmV). Our p CO 2 estimates are well correlated with the existing proxy record and geochemical models and suggest fluctuations in CO 2 levels that are consistent with temperature variations previously estimated for the periods. • Atmospheric CO 2 is reconstructed from Gondwana paleosols for parts of the Mesozoic. • Our pCO 2 data correlate well with geochemical models and other proxies. • Atmospheric CO 2 estimates also show excellent correlation with temperature. • Early parts of Triassic show large variations in atmospheric CO 2 concentration. • A new dynamic soil-respired CO 2 -proxy is formulated from modern soil data.