FLUVIO-LAGOONAL SEDIMENTARY SEQUENCES IN LEYRE DELTA AND ARCACHON BAY, AND HOLOCENE SEA-LEVEL VARIATIONS, ALONG THE AQUITAINE COAST (FRANCE)

Along the Aquitaine coast (Bay of Biscay, France), scarcity of Recent coastal deposits corresponding to post-Holocene sea level variations, is a direct consequence of the strong erosional processes observed in this coastal zone. The general transgressive trend may be due to various geodynamic events such as contemporary sea level rise or regional subsidence related to tectonic or isostatic post-glacial adjustments of this southern part of the european plate. This paper is a discussion of new data about sedimentary sequences described in recent deposits infilling the mesotidal Arcachon bay and its inner fluvial delta (of the Leyre River), enlighted by geophysical and geomorphological information on the geodynamic evolution of the central part of the Aquitaine basin. The conclusion is that the transgressive trend of this coast is related to both subsidence and sea level elevation.