Carbon dioxide in the Paleozoic atmosphere: Evidence from carbon-isotope compositions of pedogenic carbonate Available to Purchase

Stable carbon-isotope compositions of pedogenic carbonate occurring in three clay-rich vertic paleosols within Paleozoic red-bed successions in central Pennsylvania provide a record of past pedogenic environments and can be used to estimate CO₂ pressure (P_CO2) of the Paleozoic atmosphere. The δ¹³C values of carbonate nodules from paleosols in the deltaic lower Bloomsburg Formation (Upper Silurian) reflect the contribution of carbon from marine groundwater or fossils, coupled with low biological activity. The δ¹³C values of carbonate rhizocretions from stratigraphically high paleosols in the Bloomsburg Formation, and in the alluvial Catskill (Upper Devonian) and Mauch Chunk (Upper Mississippian) Formations, suggest an extensive C₃ flora and significant contribution of atmospheric CO₂. Paleozoic atmospheric CO₂ levels inferred from δ¹³C of pedogenic carbonate are significantly higher than present levels.