A process of salinization due to marine intrusion has been detected in the detrital coastal aquifer Martil-Alila, especially in the northern of Martil city. This intrusion has been caused by local overpumping. Geochemical studies reveals that the chemical characteristics of the analysed waters have their origin in the mixing of three different water components: intruding seawater, freshwater from the rainfall infiltration, and water, coming from border aquifers and with bicarbonate-calcium type. The chemical characteristics of all waters reveal the influence of salinization process caused by intruding sea water