Resumen de Desarrollo de calcretas en sistemas semiáridos coluviales de la provincia de Jaén

Rosario Jiménez Espinosa, Juan Jiménez Millán

• Quaternary colluvial deposits from the Prebetlc of External Zones of Betic Cordillera in Jaén (SE Spain) contain several levels of calcretes separating two colluvial units. We could distinguish profiles with three different horizons: (i) cemented gravels horizons; (ii) massive-laminar horizons;

  and (Hi) chalky horizons. Different textural components, such as, calcified filaments, rounded peloids, coated grains and an alveolar septal matrix are widely found in these horizons. In this area, calcrete formation was controlled by the microbial activity related with plant roots. The cemented gravels and chalky horizons were developed where colluvial inputs provided enough space for the growing of plants. The massive-laminar horizon was formed by intense carbonate precipitation episodes under high water availability conditions. These special conditions were provided by the reduction of permeability produced by the underlying cemented gravels horizon.

  Preservation of this profile could be caused by a new colluvial deposit that covered the previously formed horizons.