Hypothesis on the hydrogeological context of wetland areas and springs related to evaporitic karst aquifers (Malaga, Cordoba and Jaen provinces, Southern Spain)

Abstract

The northern sector of the External Zone of the Betic Cordillera (S Spain) is formed by an olistostrome unit known as the Chaotic Subbetic Complexes (CSC). This megabreccia is basically made of clays and evaporite rocks (gypsum and salt) of Upper Triassic (Keuper) age as well as other lithologies (dolostones, limestones, marls and calcareous sandstones) belonging to different ages (Jurassic, Cretaceous and Tertiary). Despite of low permeability has been traditionally assumed for these materials, water flow and storage through them is possible due to the aquitard behavior of clays and sandstones and the presence of conduits generated by dissolution/karstification processes within the evaporite rocks. The lithological complexity of the CSCdetermines its hydrogeological heterogeneity, with groundwater flows of different length and various scales from recharge areas to discharge zones. Thus, wetlands and springs placed at lower altitudes are associated with large (regional) groundwater flows, of greater residence time within the aquifer, and they normally drain high salinity waters mostly connected with ascending flow. This work provides an overview of the main geological and hydrogeological aspects related to groundwater flow within the CSC on the basis of several case-studies. Conceptual models are proposed for these cases, since they are the base to carry out a genetic-functional classification of wetlands potentially useful for their management.