Volcanic gaps and subaerial records ofpalaeo-sea-levels on Flores Island (Azores): tectonic andmorphological implications

Abstract

The morphological evolution of Flores Island, as commonly observed for volcanicislands, suggests (1) the balance between constructive processes (effusive and moderatelyexplosive volcanic activities and tectonic uplifting movements) and destructive processes (marine abrasion, stream erosion, crater-forming volcanic explosions, caldera collapses andtectonic subsidence) and (2) the recurrent fluctuations of the sea-level. Records of (a)gaps in the volcanic activity and (b) erosional and depositional marine activity are shown as: — epiclastic deposits of marine origin — erosional morphologies, such asabrasion platforms, terraces, cliffs and caves — intensive palagonitization of thevolcanic rocks — vertical changes of the structures in the hydroclastic submarineformations. Taking into account (1) the vertical crustal movements (uplift andsubsidence) which may occur in volcanic domains and (2) the sequence ofregressive–transgressive trends in the relative sea-level as expressed by indicators ofpale-sea-levels, it is assumed that the morphological evolution of Flores Island comprehendsthree main stages. The existence of important differences between the present-dayaltitudes of correlated marine records noted in Flores, in Santa Marie Island (AzoresArchipelago) and Porto Santo Island (Madeira Archipelago) is related with their crustalbehaviour and different volcanic and tectonic evolution. © 1999 Elsevier Science Ltd. All rightsreserved.