STRATIGRAPHY AND PALEOECOLOGY OF NEOGENE DEPOSITS OF THE COCINETAS BASIN, COLOMBIA

The Cocinetas Basin in northern Colombia provides an excellent record of the geological and ecological history of northern South America during the Cenozoic. We conducted extensive fieldwork in stratigraphy and paleontology to document the transition from the fully marine environment of the Jimol Formation (~19-17.3 Ma) to the shalllow marine to fluvio-deltaic environment of the Castilletes (~17.3-14.5 Ma) and Ware Formations (~3.5-2.8 Ma). The Jimol Formation reveals the Cocinetas Basin as a shallow marine environment from 19 Ma up to 17.3 Ma. Diverse shallow marine invertebrate communities and oyster banks flourished in a carbonate shelf during high sea level periods, while coarse calcareous and lithic sandstones were deposited in shoreface environments during low sea level stages. Mudstones of shoreface and backshore environments record the lowest sea level episodes. In the Castilletes Formation, storm events, oyster banks, and shore-face deposits vary laterally to estuarine, fluvio-deltaic plains and deltaic channel deposits, revealing the transition to fluvial dominated environments from 17.3 Ma up to 14.5 Ma. The vertebrate fossil assemblage contained in the terrestrial intervals of the Castilletes and Ware Formation provide new insights into the paleoecological history of Guajira Peninsula. Semi-aquatic organisms as crocodiles, turtles, and astrapotheres suggest the presence year around freshwater bodies. Furthermore, grazing and browsing herbivores as astrapotheres and proterotheres, respectively, suggest grasslands and forests dominating the landscape of the Guajira peninsula up to 2.8 Ma ago.