The CO2 consumption potential during gray shale weathering: Insights from the evolution of carbon isotopes in the Susquehanna Shale Hills critical zone observatory

A mass balance calculation shows that silicate and ankerite dissolution of the Rose Hill shale at Shale Hills consumes CO2 at a rate of ∼44 and ∼42-48 mol m−2 ky−1 respectively, while degradation of ancient organic matter releases CO2 at a rate of ∼1.3 mol m−2 ky−1. Silicate dissolution at the shallow soils is facilitated by low pH and high soil pCO2. As ankerite dissolution and organic matter oxidation are shown to occur early during shale alteration, CO2 consumption by shale weathering is thus limited by initiation of rock disintegration (e.g., fractures) and exposure of fresh surface area to infiltrating CO2- and O2-rich water.