Estratigrafía del Messiniense y Plioceno en el margen norte de la Cuenca del Bajo Segura (Cordillera Bética oriental). Cambios paleogeográficos asociados a la crisis de salinidad del Mediterráneo

Abstract

Four allostratigraphic units have boon recognized in the Messinian-Pliocene stratigraphic record of the Bajo Segura Basin: MI, MII, MIII, and P. The MI Unit is composed of coastal and shallow marine sediments. After a first sea-level fall that caused the intra-Messinian discontinuity, the subsequent transgression deposited the MII Unit, which included lagoonal and fluvial deposits. Another sea-level fall, that caused the Messinian-Pliocene discontinuity, carved incised valleys locally infilled by fluvial deposits (MIII Unit). The subsequent sea-level rise in the base of the Pliocene set up the marine conditions in the entire basin leading to the deposition of the P Unit. In the first transgressive stage, the P Unit filled up the incised valleys of the Messinian-Pliocene discontinuity with shallow pelagic deposits. During the second regressive stage, the continental depositional systems prograded onto the coastal and shallow marine systems. In relation to the salinity crisis, it is interpreted that the MII Unit should be lateral equivalent to the evaporites in the Mediterranean marginal basin and the MIII Unit should corresponded to the evaporites of the centre of the Mediterranean.