Paleozoic carbon cycle dynamics: Insights from stable carbon isotopes in marine carbonates and C3 land plants

C-3 land plants dominated the Paleozoic landscape since the Devonian and played an essential role in enhancing continental chemical weathering. Vast amount of organic carbon isotope data exist from Paleozoic-aged sediments deposited in fluvial, lacustrine, and floodplain environments. These carbon isotope data are measured from well-preserved plant fossils, paleosols, coals, charcoals, and bulk organic matter within the sediments. They are often used for age correlations with contemporaneous marine sections as a stratigraphic correlation tool, and are interpreted as indicators of the global carbon cycle. Here, we review the stable carbon isotope records of C-3 land plants (delta C-13(plant)) in various forms in Paleozoic sediments (mostly Devonian, Carboniferous, and Permian), as well as marine carbonate carbon isotopes (delta C-13(carb)), and interpret them in the context of global carbon cycle. The increasing trend of delta C-13 in both marine carbonates and terrestrial organic matter suggests an increase in organic carbon burial in the form of coal or petroleum, which is controlled by sea level, nutrient availability, and innovation of life. This compilation allows for the reconstruction of a new high-resolution atmospheric pCO(2) from 423 to 252 Ma. We noted that the pCO(2) was similar to 2000 ppmv in the Devonian, then lowered to similar to 850 ppmv in the Carboniferous, and peaked at similar to 7600 ppmv during the Late Permian. This trend is broadly consistent with pCO(2) reconstructed from other proxies, including pedogenic carbonate proxy, stomatal proxy, and phytane proxy, with the exception of the Late Devonian when our reconstructed pCO(2) is significantly higher than the other proxy records. Proxy-based paleotemperature records suggest higher pCO(2) in the Late Devonian is more consistent with the elevated paleotemperatures.