Geophysical and geological contribution to determining the neritic limestone aquifer structure of Hammam Bradaa – El Fedjoudj (Seybouse medium), Northeastern Algeria

Purpose. The neritic aquifer that extends between Hammam Bradaa and El Fedjoudj, despite its faulted and in places karstified structure, due toits capacity and lateral extension represent a strategic resource for the region. Its waters are used for drinking water supply in the neighboring towns: Heliopolis, Guelaat Bousbaa, Nechmaya and El Fedjoudj, as well as in part of the Annaba wilaya. These neritic limestones outcrop at Djebel Debagh and Bouzitoune. Methods. In order to better study the potential of this aquifer, it is essential to identify its geometry and structure by analyzing the geological data, mechanical drilling data and geophysical data analysis through an electrical survey campaign. Findings. The main results indicate that the study area has identified two important aquifer formations: a formation in the Mio-Plio-Quaternary alluvium consisting of clays, marls, gravel and sand; the second is a deep carbonate aquifer composed of fissured and karstified neritic limestone of the Cretaceous age of variable depth ranging within 50 and 350 m. Originality. The originality of the study is in the fact that the studied area is characterized by the presence of thick, fractured and karstified carbonate formations, which are intensively tectonized and have significant aquifer potential. Practical implications. The correlation of geological data with geophysical data made it possible to conclude that the stu-died area is a sedimentary basin bounded by faults predominantly oriented to the south-west and north-east, forming a highly fractured unit consisting of horsts and grabens. The significant water potential reservoir is formed essentially by carbonate geological formations, highly fractured with the presence of karst forms represented by resistant horizons.