PALEOENVIRONMENTAL INTERPRETATION OF HOLOCENE COASTAL SEQUENCES IN THE SOUTHERN BAY OF BISCAY

The main sedimentary features of the northern coast of the Iberian Pen insula during the Holocene transgression are characterized by the form ation of estuaries, the deposition of sand bars and sand beaches, and the accumulation of aeolian dunes. These coastal deposits are very fav ourable for identifying Quaternary sea-level changes as they contain g reat volumes of well preserved sediments including marine, brackish an d freshwater beds. The micropalaeontological analysis (benthic foramin ifera) of diverse littoral sequences has allowed different microfaunal assemblages to be recognised and their corresponding depositional env ironments determined. Two recurrent phases of sediment build-up as the sea level rose have been distinguished. They have been interpreted as the consequence of two different marine advances in this region: one dated at around 8 000 years BP and the second around 2 500 years BP.