Carbon isotopic subsets of soil carbonate—A particle size comparison of limestone and igneous parent materials

Carbon Stable Isotope Composition of Modern Calcareous Soil Profiles in California: Implications for CO2 Reconstructions from Calcareous Paleosols

“…Soil CO 2 may be characterized by mixing of one, two, or three components that originate from different circumstances and which can result in significantly different d 13 C values of soil CO 2 and pedogenic calcite (Cerling 1984;Hsieh and Yapp 1999;Yapp 2001Yapp , 2002Yapp 2005a, 2005c;Feng and Yapp 2009;Sheldon and Tabor 2009). The three CO 2 components are derived from (1) oxidation of in situ organic matter, (2) tropospheric CO 2 , and (3) dissolution and/or incorporation of preexisting carbon-bearing minerals such as calcite in the soil (Rabenhorst et al 1984, West et al 1988, Hseih and Yapp 1999, Kraimer and Monger 2009, Sheldon and Tabor 2009. The following discussion considers these different CO 2 mixing scenarios and their applicability to calcite from the modern soil profiles studied herein.…”

“…Another possible scenario by which a third component may affect the measured d 13 C values of soil calcite is physical entrainment of detrital or parent-material carbonate grains within pedogenically formed calcite (e.g., Rabenhorst et al 1984, West et al 1988, Kraimer and Monger 2009. Marine limestone has relatively high calcite d 13 C values, ranging from approximately À2 to 6ø (Veizer et al 1999), which are substantially greater than the calcite d 13 C values encountered in most soils characterized by mixing of two soil CO 2 components (e.g., Salomons et al 1978;Schlessinger 1982Schlessinger , 1985Cerling 1984;Rabenhorst et al 1984;Amundson et al 1989Amundson et al , 1998Quade et al 1989;Cerling and Quade 1993;Wang et al 1996;Monger et al 1998;Nordt et al 1998;Kraimer and Monger 2009). In this respect, incorporation of a third carbon component, whether it be as CO 2 or physical entrainment of preexisting carbonate, is expected to result in generally more positive d 13 C values in soil calcite.…”

“…Reflected light microscopic inspections of these samples provide no obvious indications (e.g., invertebrate fossils) of an entrained population of detrital carbonate grains. Petrographic microscopy is a superior means by which to evaluate the presence of detrital grains (West et al 1988, Kraimer andMonger 2009), but none of these samples have been inspected petrographically as a result of concerns related to exhausting the small amount of sample available for geochemical analysis. Because we are not able absolutely to rule it out at this time, we consider samples from profile 10 (Beveridge) to incorporate a detrital source of carbonate, and we assume as well that measured calcite d 13 C values from this profile may be more positive than those from a purely pedogenic calcite.…”

Assessing the origin of carbonates in a complex soil with a suite of analytical methods

“…A δ 13 C around −4‰ (P1) is often reported for carbonates influenced by a mix of C 3 and C 4 vegetation during their formation (e.g. Kraimer and Monger, 2009). This kind of environment is consistent with the Pleistocene (Huang et al, 2001).…”

Human induced calcretisation in anthropogenic soils and sediments: Field observations and micromorphology in a Mediterranean climatic zone, Israel

“…Other terms to describe this material include pedogenic carbonate, caliche, tosca, croûte calcaire, kankar, secondary carbonate, authigenic carbonate, and, depending on its origin, geogenic, lithogenic, primary, and inherited carbonate (Monger et al, 2015a). When physically associated, the influence of soil materials on calcrete is most pronounced (Watts, 1980;Chafetz et al, 1985;Wright et al, 1993;Kraimer and Monger, 2009) rightfully allowing 'pedogenic calcrete' to be defined as a classifiable calcrete type. Pedogenic calcretisation (namely the formation of pedogenic calcrete) is controlled by the interactions between host regolith, climate, aeolian dust, Ca 2+ in precipitation, biogenic activity, topography, tectonic stability, and time of formation (Gile et al, 1966;Wright and Tucker, 1991;Alonso-Zarza and Wright, 2010;Monger et al, 2015a;Verrecchia, in this issue).…”