Modern Soil Analogs of Carbonate Chemistry and Genesis in Paleosols.

In the geological record, especially with highly oxidized sediments such as these soil systems, organic matter is commonly not preserved for carbon isotope analysis. Carbonate isotope geochemistry is commonly the only indication of C3/C4 photosynthesis when working with paleosol systems. Therefore, the fact that soil carbonates from two different profiles, on the same landscape position, dominated by C3 photosynthesizers in one profile, and C4 photosynthesizers in another profile, suggests temporal reconstructions of Neogene evolution of C4 photosynthesizers may often be overly simplistic. This reinforces the suggestion that sampling lateral transects in conjunction with stratigraphic studies of paleosol carbonate delta C13 values may be necessary to adequately address landscape heterogeneity.