GEOMORPHOLOGY AND BIOSEDIMENTOLOGICAL CHARACTERIZATION OF A LAGOON SYSTEM IN A MICROTIDAL WESTERN MEDITERRANEAN EMBAYMENT (ALBUFERETA-DE-POLLENCA, BALAERIC ISLANDS)

The Albufereta de Pollenca is one of the typical western Mediterranean lagoons located on Miocene-age depressions of the Balearic Islands. I c is characterized by a brackish salt marsh with ponds and channels se parated from the sea by a bioclastic beach-dune system. This is crosse d by an outlet that connects the marsh with the sea forming a microdel ta. Tides are negligible and most of the morphology and dynamic proces ses are related to wave activity and the oscillation of barometric pre ssure. Alluvial processes are very irregular and limited depending on the typical Mediterranean climatic regime. Eight different sedimentary facies are described which may be grouped as lagoonal (dark brown sil ts with bioclastic remains, nodular green lime mud, grey laminated sil ts, terrigenous red silts and dark brown silts with Posidonia) and lit toral (fine to medium laminated bioclastic sands, lithoclastic gravels and fine sands with Posidonia) deposits. These facies describe the sy stem the horizontal and vertical distribution of which are related to the latest Quaternary transgression.