Lower to middle pleistocene coastal dune fields formation in the western mediterranean (Western Eivissa, Balearic archipelago): Chronology and landscape evolution

摘要

Colluvial and aeolian successions in coastal environments are useful indicators of geomorphological changes that occurred during the Quaternary. Pleistocene aeolian deposits interbedded with colluvial deposits and palaeosols in areas of Cap Negret, Punta de sa Pedrera, Cala Bassa and Cala Compte, western coast of the island of Eivissa (western Mediterranean) are studied here. These deposits span almost continuously along 14 km of the coast, covering an area of approximately 22 km(2). We present a sedimentological and stratigraphical description of these Pleistocene outcrops. Five major sedimentary facies involving the succession of aeolian, colluvial and edaphic environments are described. Carbonate sandstones, breccias, conglomerates and fine-grained deposits are the main components of these sequences. Optically stimulated luminescence (OSL) dating of aeolian levels indicates that deposition took place from the Lower to Middle Pleistocene. The sedimentological and chronological analysis of these deposits allows reconstructing of the coastal Pleistocene environmental history from Marine Isotopic Stage (MIS) 22 to MIS 6. Results show that the main controls on Lower to Middle Pleistocene coastal landscape evolution on Western Eivissa are changes in the average wind direction over time, modulated by the interaction with coastal relief orientation. The main episodes of aeolian activity identified and dune formation in the Western Mediterranean can be linked to periods of low sea level.