The possible geological history of the quaternary events in the coastal plain of the Southern São Paulo State, in the area known as Iguape-Cananéia lagoonal region, is here presented. Field observations and sedimentological analysis made by the A., geophysical data and examination of the samples from two stratigraphical wells drilled by I.G.G. and the informations from shallow research holes made by Geobrás S/A, Engineering and Foundations, made possible the accomplishment of this work. Grain size characteristics of the sediments from the present environments were also compared with the grain size characteristics of the sediments from the ancient environments, allowing the recognition of the depositional mechanisms of the ancient sediments. The regressive deposits, "blanket sands" or "sheet sands" type (KRUMBEIN and SLOSS, 1963, p. 550), already recognized as old beach sands by previous authors, never was clearly characterized. Here they are described, in detail, due to their great importance in the coastal plain regional geology, not only because of their great persistence, but also, as a consequence, because they were the most important source of detrital materials to the present sub-environments. To this lithological unity is proposed the denomination Cananéia Formation. The recognition of the transgressive and regressive sequences was possible only through the studies of the I.G.G. stratigraphical wells.
