Abstract

The volcanoclastic deposit that crops out in the western sector of La Gomera at the base of the Upper aquifer has been mapped and described. It is possible to differentiate it into seven units in the basis of their compositional and depositional features. In addition, geological cross-section and a 3D reconstruction have been carried out. The geometry of the deposit shows a coherent continuous surface dipping southward. It adapts to a pre-existing relief with its highest depth between Barranco de Arure and Barranco de Valle Gran Rey and a minor paleorelief in the headwaters of Valle Gran Rey. The importance of this deposit from a hydrogeological point of view is that it is located at the base of the Upper aquifer and seems to be continuous. Four main groundwater flow paths can be distinguish in this sector: 1) water springing out due to a shallower paleorelief; 2) a flow path along the main pre-existing relief; 3) groundwater flowing towards the western springs; and 4) groundwater recharging the Basal aquifer by leakage from the Upper one in the eastern sector of the studied area.