A Ground Penetrating Radar (GPR) survey was carried out on the Pas-de-Calais coast in arder la quantify the evolution of sand dunes during the holocene period. 15 km of GPR profiles were recorded with 100 and 500 MHz antennae. Some boreholes were drilled to control the GPR results. Correlation between GPR and boreholes is better than 35 cm. At last, 7 peat layers have been found wilh a north-east dip. It reveals the existence of changes in hydrogeological conditions (variations of water table) during the last 900 years (mast ancient peat in dunes peat layers). Moreover, some ancient dunes features have been outlined between flat peat layers. GPR is a robust tool for sedimentological interpretation in sandy context.