The Cariaco Basin is located on the northern continental shelf of Venezuela in a region characterized by intense upwelling due to the seasonal migration of the Inter-Tropical Convergence Zone (ITCZ) and associated variations in trade wind intensity. Hydrographic observations indicate that coastal upwelling occurs during the late winter-early spring at which time sea surface temperatures are lowest (~22oC) and primary productivity and planktonic foraminiferal fluxes are high (4000-8000 shells m^-2 day^-1). A three-year sediment trap experiment was conducted in the Cariaco Basin (January 1997-December 1999) to study variations in flux assemblage composition and shell chemistry for comparison with the climatology and hydrography of the region on seasonal and interannual timescales. Nine species of planktonic foraminifera constitute >85% of the assemblage: Orbulina universa, Globigerinoides ruber (pink and white varieties), Globigerina bulloides, Globigerina quinqueloba, Neogloboquadrina dutertrei, Globorotalia crassaformis, Globorotalia menardii, and Globigerinita glutinata. Globigerina bulloides is dominant during spring upwelling, however, the peak annual flux of all nine species occurs during this period. The stable isotopic composition was used to evaluate the application of each species in paleoceanographic reconstructions. Temperature estimates based on species-specific paleotemperature equations and analysis of the annual flux-weighted d18O signal indicate that the d18O record of G. ruber (pink) is most suitable for estimating mean annual SSTs while G. bulloides provides information regarding conditions during spring upwelling.

Oxygen isotope records of G. ruber (pink), G. bulloides, and N. dutertrei from gravity core CAR7-1 were used to construct a high-resolution climate record for the Caribbean region for the last 6,000 years. Our results indicate major decreases in SST and/or increases in salinity in the basin at least four times in the last 4,000 years (~3,800-3,200, 2,800-2,500,2,200-2,000, and after 650 cal yrs. B.P.). These events are coincident with high stands of Lake Titicaca, Bolivia/Peru suggesting a similar forcing mechanism. The onset of arid conditions in the circum-Caribbean region between ~3,600-3,200 cal yrs. B.P. corresponds to a 1per mil increase in the d18O of G. ruber (pink), decreases in the Dd18O, and the migration of the subthermocline dwelling planktonic foraminifer Globorotalia crassaformis into the basin. Taken together these data indicate colder SSTs and a shallow thermocline, possibly due to increased upwelling. Dry conditions in the circum-Caribbean tropics and wetter conditions in the Altiplano of Bolivia/Peru and the Amazon basin during the mid to late Holocene are consistent with the southward displacement of the ITCZ which would have resulted in decreased precipitation and increased trade wind intensity in the Cariaco Basin.