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RESEARCH PRODUCT

Dissolution and precipitation of gypsum and carbonate minerals in soils on evaporite deposits, central Sicily: isotope geochemistry and microfabric analysis

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Abstract Soil profiles developed from carbonate- and sulphate-rich deposits of the Gessoso-Solfifera Formation (Miocene) were sampled in central Sicily (544 mm annual precipitation and a strongly seasonal rainfall regime). Carbon and oxygen isotope data supported by mineralogical and thin section investigations indicate that meteoric waters and groundwaters dissolve and repricipitate carbonates and gypsum in the soil profiles. The boundary between the C horizon and the overlying one is the formation site of 18O depleted carbonates (calcite and/or dolomite) presumably precipitated from percolating waters during wet periods. Greater δ18O values of carbonates in the shallower horizons suggest that their precipitation is driven by evaporation and CO2 losses from the soil solution during periods of reduced rainfall. Root respiration and decomposition of isotopically light plant material largely influenced the carbon isotopic composition of the analysed carbonates. Anomalous 18O and 13C enrichment compared to the parent material reflects strong evaporation and exchanges with atmospheric CO2 in a sparsely vegetated thin soil.