Coupled carbon and oxygen isotope model for pedogenic carbonates

Carbon and oxygen isotope values of ancient pedogenic carbonates reflect the paleoenvironmental conditions under which formed. are commonly used to reconstruct pCO2, C3 vs. C4 plant types, carbon cycle dynamics. Oxygen same have been past temperatures elevations. In geologic record, changes in these can be difficult interpret because they affected by a suite multiple local (e.g. precipitation temperature) global variables pCO2 that separate. this study, we develop semi-mechanistic model factors affect carbonate. The links common environmental using theoretical empirical relationships. We test optimize modern data compilation carbonate measurements. This comparison indicates best reproduces observed when assumed form where (1) evaporation affects source waters at shallow soil depths only, (2) mix from prior during period formation, (3) CO2 respiration rates anomalously low. Global predictions optimized suggest strong spatial variation both highlight areas future measurements samples might provide tests model. also demonstrates coherent patterns coupled ?13Ccarbonate ?18Ocarbonate value associated with different types forcing, offers new framework for interpreting paired constrain change.