Atmospheric pCO2 Reconstruction of Early Cretaceous Terrestrial Deposits in Texas and Oklahoma Using Pedogenic Carbonate and Occluded Organic Matter

Geosciences

Timothy Myers¹  Neil Tabor²  Dale Winkler²  Kate Andrzejewski³ 

[1] Department of Earth and Environmental Science, Temple University, Philadelphia, PA 19122, USA;Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX 75205, USA;Kansas Geological Survey, University of Kansas, Lawrence, KS 66047, USA;

关键词: paleosol;    pedogenic carbonate;    organic matter;    δ¹³C values;    δ¹⁸O values;    Albian;   

DOI  :  10.3390/geosciences12040148

来源: DOAJ

【 摘 要 】

Pedogenic carbonate samples collected from three Lower Cretaceous (Aptian–Albian) fossil localities in Texas and Oklahoma were analyzed to develop paleoatmospheric pCO₂ estimates by measuring the stable carbon isotopes of pedogenic calcite and their co-existing occluded organic matter. Calcite δ¹³C values ranged from −10.9‰ to −4.4‰ while occluded organic matter δ¹³C values ranged from −27.3‰ to −21.1‰. These stable carbon isotope measurements combined with temperature (30 °C) and soil-respired CO₂ concentration (839–6047 ppmV) values provided atmospheric pCO₂ estimates ranging from 67 ppmV to over 1100 ppmV. These estimates show a significant increase in atmospheric pCO₂ during the late Aptian followed by a decrease in atmospheric pCO₂ during the late Aptian to early Albian transition period, roughly correlating with the OEA1b event. Given the lack of chronostratigraphic constraints of the Lower Cretaceous geologic units in the study area, these data provide further evidence for the approximate age of the units as well as pertinent paleoclimate insights into greenhouse climate conditions.

【 授权许可】

Unknown