Late Pleistocene Faunal and Temperature Patterns of the Colombia Basin, Caribbean Sea
Warren L. Prell, James D. Hays, 1976. "Late Pleistocene Faunal and Temperature Patterns of the Colombia Basin, Caribbean Sea", Investigation of Late Quaternary Paleoceanography and Paleoclimatology, R. M. Cune, J. D. Hays
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High-salinity, low-productivity Sargasso Sea type water developed in situ within the Colombia Basin during glacial extremes. Evidence for “ice-age aridity” in northern South America supports this hypothesis. Q-mode factor analysis of total planktonic foraminiferal faunas from three Colombia Basin sediment cores defines equatorial-tropical and southern Sargasso faunal assemblages, which correspond to interglacial and glacial conditions in the Colombia Basin. The oceanographic conditions represented by these assemblages were deduced from the present faunal distributions in the North Atlantic Ocean. The interglacial assemblage has maximum abundances in the equatorial zone, which is characterized by moderate salinities, strong currents, and high nutrients and productivity. The glacial assemblage occurs today in the distinctive southern Sargasso Sea water of high salinity, low nutrients, and low productivity. The alternation between interglacial-equatorial and glacial-Sargasso Sea assemblages in the Colombia Basin suggests that during glacial periods, Sargasso type water was formed in situ within the Colombia Basin.
Paleotemperature estimates derived by the Imbrie and Kipp technique (1971) reveal only 2° to 3°C average temperature changes between interglacial and glacial stages. During glacial stages, however, seasonal contrast (Ts−Tw) was increased; the winters had much larger variations (4° to 5°C) than did the summers (1° to 2°C). Because the evaporation/precipitation ratio (E/P) is greatest today during the Caribbean winter, increased seasonal contrast during glacial stages may have increased the E/P, resulting in high salinities similar to present Sargasso water. The increased E/P suggests that the Intertropical Convergence Zone was on the average located over South America more during the glacial stages than at present.