Calcrete development in mediterranean colluvial carbonate systems from SE Spain

Holocene colluvial deposits from the Prebetic Zone (Betic Cordillera, S Spain) contain calcretes separating two colluvial units. Calcrete profiles contain three horizons: cemented gravels, chalky and massive-laminar. Scanning electron microscopy study revealed the presence of calcified filaments, rounded peloids and coated grains which indicates that calcrete formation was controlled by the microbial activity related with plant roots. X-ray powder diffraction data showed the presence of smectite and hematite and the absence of sepiolite–palygorskite, suggesting a semi-arid climate. The main factors controlling the features of the different calcrete horizons are topography (lateral continuity), inputs of colluvial deposits (cemented gravels and chalky calcrete) and water availability (massive-laminar calcrete