Resumen
In south central Chile the Middle Archaic is well represented by ChanChan 18, a complex coastal settlement located at the coast of Valdivia (39°30'S/73°15'W). In this archaeological site two separated phases of occupation are recognized, the first dated between 5,730 and 6,130, and the second between 6,250 and 6,420 cal. yr BP. Grained size and stratigraphical analyses interpreted by means of multivariate analyses, which include present samples of beaches and dunes, have allowed the recognition that the oldest occupation of the site was located near the berm of a paleo-beach. Such feature corresponds to the record of the maximum Holocene transgression, with an elevation of 8 m a.s.l. The transgression is synchronous with others of north and central Chile, but it confirms the generalized Quaternary rise of the southcentral coast of Chile, as it has been suggested by other observations and studies. This rise happens in spite of the coseismic subsidence described in this region.