The Cariaco Basin is an east-west trending pull-apart basin located on the continental shelf off the eastern coast of Venezuela. It is a deep depressioncomposed of two sub-basins, the eastern basin and the western basin, each of about depth, separated by a saddle of approximately waterdepth. To the south, the basin confines with the wide Unare Platform. It is connected to the open Caribbean Sea through two shallow channels, to the north the and to the west the. Water circulation inside the basin is restricted, which, combined with the high annual primary productivity of the region, causes the basin to be permanently anoxic, below ~250 m. This naturally occurringanoxic basin allows for sediments to be deposited without bioturbation, forming varves of alternating light and dark color, which correspond to the dry or rainy season. Its unique geography and undisturbed sediment record provides an excellent history of tropical climate change and is particularly sensitive to shifts in the Intertropical Convergence Zone and has been the subject of extensive paleoclimatological research, amongst other sedimentological studies, geochemical studies, with alkenones, Mg/Ca, and micropaleontological, with foraminifera, pollen and spores, dinocysts and coccoliths.
Anoxic basin
Because of its anoxia, the Cariaco Basin has also a unique chemistry. Bacteria inhabit both the oxic and anoxic portions of the water column, with a maximum around the interface where oxygen disappears. This 'interface' oscillates between 200 and 300 meters. As such unique location, the Cariaco Basin has been the site of a variety of studies since the mid-1950s. Since 1995, an international program has expanded the research in the basin. The CARIACO program consists of a time series station in the eastern deep of the basin which is visited on a monthly basis to collect hydrographic, nutrient and primary productivity measurements. A suite of other measurements, including a sediment trap mooring, microbiological studies and current measurements are also conducted at this site. The work that has resulted from the CARIACO ocean time series program has demonstrated that this anoxic basin is quite dynamic and has helped understand the paleoclimatic record stored in the basin's sediments. The waters are home to varieties of marine lives including whales, dolphins and orcas.
