Isotopic and mass constraints on crustal and sedimentary organic carbon

Abstract

Organic carbon burial plays a fundamental role in the Earth's long term carbon cycle, control of atmospheric CO2, and the oxygenation of the Earth's surface environment. Organic carbon undergoes substantial transformation from biosynthesis to geological cycling that changes its chemistry and isotopic composition. Inventory methods have estimated that 13–14 Tmol (1012) C year−1 are currently added to sediments, but isotopic mass balance estimates have been much lower. A new evaluation of the isotopic mass balance reconciles these differences. Consideration of carbonate and organic carbon weathering and methane oxidation imply lower mean δ13C of inputs than given by volcanic degassing alone which in turn impacts the isotopic mass balance for carbon burial.