Stable isotopic composition of paleosols in the Lower Viséan of eastern Belgium: evidence of evaporation and soil-gas CO 2

Abstract

Numerous paleosols occur in the Lower Viséan peritidal limestones of eastern Belgium. At the top of the peritidal unit, a widespread paleosol horizon occurs which has been analysed for its carbon and oxygen isotopic composition. In spite of the Paleozoic age of the pedogenic carbonates, the influence of evaporation and soil-gas CO 2 on the stable isotopic composition of the paleosol is very pronounced. This has been assinged to the long exposure time in a semi-arid seasonal climate. Evaporation caused an enrichment in 18O in the paleosol compared with the over- and underlying limestones, which were cemented and mineralogically stabilized in meteoric pore waters. The influence of soil-gas CO 2 in the soil formation is clearly indicated by the depletion in 13C of the pedogenic carbonates ( σ 13C = −5% PDB) compared with the carbon isotopic composition of Lower Viséan marine limestones ( σ 13C = +4% PDB). The possible effect of carbon derived from atmospheric CO 2 on the σ 13C-values of the paleosols is discussed.