7 GEOGACETA, 48, 2010 Copyright ' 2010 Sociedad Geolgica de Espaæa / www.geogaceta.com Introduction Under the current climatic scenario of global warming, it is expected an increase in storminess along the coastal areas of the North Atlantic Ocean. To this factor, we have to add rising sea- levels, with global estimates of + 0.6 (IPCC, 2007) to > 1 m (e.g. Rahmstorf, 2007, Parry, 2000) by the end of the 21 st century in worst-case scenarios. This is expected to have a large impact in coastal barriers. As a result, there is a growing interest in erosion and deposition processes along these areas. In fact, recent storm events inducing barrier breaching and retrogradation have demonstrated the economic impacts of these events and the need to better understand the driving processes (Hippensteel and Martin, 1999). Storms are major agents in coastal evolution and this is even more critical in barrier coasts (Andrade et al. , 2004). If storminess increases over time, one possible result in coastal areas is triggering or enhancement of roll-over, added by multiple barrier breaching and this, in a rising sea level scenario, could have a dramatic impact in those areas. Geological studies of these deposits could help to improve our understanding of the long-term variability of the storm frequency and magnitude that apparently has been changing over the last 150 years (Hippensteel and Martin, 1999; Andrade et al., 2004). In this study, we analyze the sedimentological and micropaleontological signatures of the Oualidia washover (Moroccan Atlantic coast) and sediments beneath, in order to provide insights into the back-barrier depositional processes, including storm-generated overwash, aiming to improve our present-day ability to identify signatures of such events in the sedimentary geological record. Study area Oualidia lagoon is located on the North Atlantic Ocean (32”4042N- 32”4707N and 8”5230W- 9”0250W; Fig. 1). The lagoon is 7 km long and 0.5 km wide and its elongation follow the general southwest-northeast trend of the coastline. One major inlet (150 m wide and 2 m deep) allows water exchanges with the ocean and tides are conveyed by one meandering main channel (2 m mean depth) that further di- vides into small creeks feeding lagoonal marshes. The general morphology is controlled by a Plio- Quaternary abandoned cliff running along the eastern margin of the lagoon and at the seaward Multiproxy approach to characterize an overwash deposit: Oualidia lagoon (Moroccan Atlantic coast) Caracterizacin multidisciplinar de un depsito de overwash: laguna costera de Oualidia (costa AtlÆntica marroqu) Eduardo Leorri (1) , M. Conceiªo Freitas (2) , Bendahhou Zourarah (3) , CØsar Andrade (2) , Samira Mellas (3) , Anabela Cruces (2) , Roger Griboulard (4) and Vera Lopes (2) (1) Department of Geological Sciences, East Carolina University, Graham Building, Room 101, Greenville, NC, 27858. USA. leorrie@ecu.edu (2) Universidade de Lisboa, Faculdade de Ciencias, Centro e Departamento de Geologia, Campo Grande, 1749-016, Lisboa, Portugal. cfreitas@fc.ul.pt; candrade@fc.ul.pt; acruces@fc.ul.pt; verapaiolopes@gmail.com (3) Department of Geology, Faculty of Sciences, El Jadida, Morocco. zourarah@gmail.com; mell.2006@hotmail.fr (4) UniversitØ de Bordeaux 1, Avenue des FacultØs, 33405 Talence, France. r.griboulard@epoc.u-bordeaux1.fr RESUMEN Se han analizado muestras sedimentologicas y micropaleontologicas de un sondeo realizado en el extremo sur oeste de la laguna costera de Oualidia (Marruecos). Los resultados obtenidos muestran una secuencia de relleno que presenta una evolucin desde materiales submareales con influencia marina hasta que la zona se colmata y aparece un medio marismeæo. La zona intermedia de la secuencia presenta materiales arenosos con influencia marina que se hacen mas restringidos, como indica el predominio de materiales fangosos y foraminferos tpicos de ambientes salobres. Esta secuencia estÆ truncada en el techo por la presencia de un deposito de overwash. Mientras que este depsito pueda diferenciarse netamente de los materiales infrayacentes, es imposible concluir que esta combinacin de tØcnicas pueda utilizarse para identificar depsitos de tormenta en el registro fsil. Los resultados obtenidos, sugieren, sin embargo, que este tipo de depsitos podran diferenciarse en secuencias continuas de depsitos marismeæos y por tanto podran proporcionar informacin relevante de la frecuencia e intensidad de tormentas ocurridas en el pasado. Esos estudios han de tener en cuenta, sin embargo, otros aspectos sindeposicionales, como son la bioturbacin o la preservacin de las capas sedimentarias. Key words: Overwash deposits, Oualidia lagoon, sedimentology, foraminifera, Atlantic coast. Geogaceta, 48 (2010), 7-10 Fecha de recepcin: 15 de febrero de 2010 ISSN: 0213-683X Fecha de revisin: 21 de abril de 2010 Fecha de aceptacin: 28 de mayo de 2010