CENOZOIC GEOLOGIC EVOLUTION OF THE SOUTHERN TUMACO FOREARC BASIN (SW COLOMBIAN PACIFIC)
Sandstones are mainly litharenires and feldspatic litharenites, texturally immature, and composed of cherts, basic to intermediate volcanic fragments, and crystals such as feldspars (Na and K), pyroxene, amphibole and biotite, which can be associated with basic-intermediate volcanic, plutonic and sedimentary rocks of the current basement of Western Cordillera. Sediment provenance analysis (detrital zircon and heavy minerals) suggests continuous volcanism from Late Oligocene to Pleistocene times, the activity of which increased since the Middle Miocene. The presence of low percentages of pre-Cenozoic zircons and metamorphic rock fragments in the Miocene units, would be related to reworking of ancient sedimentary units or to a partial connection with the Central Cordillera basement. The study of Miocene-Pliocene outcrops and well cores allowed to interpret a shallowing of the basin during the Messinian-Zanclean times. Volcanoclastic fans, as well as fluvial and coastal sediments, associated to the current Patía and Mira rivers are partially covering the Miocene-Pliocene deposits.