Structure of a complex carbonate aquifer by magnetic, gravity and TDEM prospecting: Los Chotos-Sazadilla-Los Nacimientos (Jaén, Southern Spain)

Knowledge of aquifer geometry is essential for efficient and sustainable groundwater management, particularly in carbonate aquifers due to uncertainties inherent to karstic systems. The geological structure and hydraulic connection of the Los Chotos-Sazadilla-Los Nacimientos and the La Serreta-Gante-Cabeza Montosa carbonate aquifers (S of Jaén; Spain) have been established through structural measurements, geophysical prospecting ―magnetic, gravity and TDEM― and the study of piezometric levels. Yet the scarce hydrogeological data, the complexity of the tectonic structure and the presence of Plio-Quaternary rocks covering the highly permeable carbonate rocks make it difficult to establish a robust conceptual hydrogeological model of the aquifer. This study focuses on an area where hydraulic disconnection between the two aquifers was traditionally assumed, given the diapiric emplacement of low-permeable rocks between them. The new geophysical data demonstrate connection between aquifers that implies greater groundwater reserves than previously supposed. This field example supports the suitability of the combined use of electromagnetic methods with gravity and magnetic research that have been poorly combined up to recent for hydrogeological studies.