This study involves two original investigational methods, at least in this case: statistical analysis and exoscopy. The statistical analysis is a both descriptive and qualitative technique. Two complementary statistical analysis methods were used at the same time: a major component analysis and a classification into stable groups. Both techniques were applied on the one hand to dredge data (whole sediment) and on the other hand, to the sand fraction data. Exoscopy is a primarily qualitative method. The numerous quartz grains observed with a scanning electron microscope were taken from about thirty samples selected according to the results of the statistical an alysis. The results obtained through this method show, on the site scale, that sedimentation in Cretaceous time very much depended on two major processes of regional extent: tectonic events and hydrodynamic regime