Middle to Late Paleozoic Atmospheric CO2 Levels from Soil Carbonate and Organic Matter

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Science  23 Feb 1996:
Vol. 271, Issue 5252, pp. 1105-1107
DOI: 10.1126/science.271.5252.1105


The stable carbon isotope compositions of ancient soil carbonate and coexisting soil organic matter indicate that atmospheric CO2 levels decreased by a factor of 10 during the middle to late Paleozoic era. Proxy measurements of CO2 were made by application of a soil carbonate CO2 paleobarometer to a suite of paleosols that share key physical and chemical characteristics. The estimates agree with theoretical models that imply that a decrease in Paleozoic atmospheric CO2 levels was associated with afforestation of the land surface by terrestrial plants and with global climate change leading to the extensive Permo-Carboniferous glaciation.

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