Different stratigraphic schemes have been proposed by various authors for the Neogene marine sedimentary deposits cropping out along the central Chilean coast between Valparaíso (~33°00'S) and Punta Topocalma (~34°30'S), without any consensus having been reached. Neither does any agreement exist with respect to the correlation between the deposits cropping out in the northern part of this area, between San Antonio (~33°30'S) and Valparaíso, and those of the southern part, between San Antonio and Punta Topocalma. Based on new stratigraphic, sedimentologic and paleontologic studies we propose a formal, new stratigraphic classification for this area. According to this scheme we define the Navidad Formation (Upper Miocene-Lower Pliocene) and the Licancheu, Rapel and La Cueva formations (Pliocene). We propose that the rank of the three first cited units (Navidad, Licancheu and Rapel), generally considered to be members in previous classifications, be elevated to formations, because they are separated by regional unconformities (paraconformities). In this paper we define these units, revise the previous classifications, and explain the basis for the new classification.
Fossil freshwater centric diatom Mesodictyon japonicum Yanagisawa & H.Tanaka from the upper Miocene marine deposits distributed in the Ninohe-Sannohe area, near the boundary between Iwate and Aomori prefectures, Northeast Japan
