Global patterns of radiocarbon depletion in subsoil linked to rock-derived organic carbon
K.E. Grant, R.G. Hilton, V.V. Galy
Abstract
<p>Organic matter stored in sedimentary rocks is one of the largest stocks of carbon at Earth’s surface. The fate of this rock organic carbon (OC<sub>petro</sub>) during weathering in soils influences the geological carbon cycle, and impacts soil radiocarbon content that is used to quantify soil carbon turnover. Here, we assess the potential contribution of OC<sub>petro</sub> to soils, using a mixing model generated by a global dataset of soil radiocarbon measurements (<sup>14</sup>C). Soils developed on sedimentary rocks (rather than on igneous substrate) have a paired OC content and <sup>14</sup>C values consistent with OC<sub>petro</sub> input, giving rise to apparent increase in soil residence time. We call for renewed assessment of OC<sub>petro</sub> input to soils, in terms of its impact on soil radiocarbon inventories, and its potential to release carbon dioxide.</p>