Mapping Limestone Aquifer by Electrical and Seismic Methods in the Zmajevac Area (Croatia)

Exploratory area is located in the Pannonian basin, 95 km east of Zagreb, with a geological model atypical for basin conditions. The aquifer is a “package“ of limestones, clayey limestones and marls (for geological and petroleum exploration purposes named “Croatica layers”), characterized by secondary porosity and very slight increase in relation to the impermeable “package“ of the Sarmatian deposits, which are similar to turbid sediments. Due to a complex geological model, electrical and seizmic methods were applied, with 2-D electrical tomography being the main exploration method. The Croatica layers were successfully isolated and mapped, located at depths ranging from several to approximately 40 metres, as well as the fault zones with increased rock fragmentation. The forecasting model was confirmed by the exploratory borehole, set in one of the identified fault zones in the Croatica layers, and satisfactory quantities of ground water (about 5 l/s) were obtained by exploratory pumping.