7. LATE PLIOCENE AND QUATERNARY PALEOCEANOGRAPHY OF THE CANARY ISLAND REGION INFERRED FROM PLANKTONIC FORAMINIFER ASSEMBLAGES OF SITE 953 1Charlotte A. Brunner 2 and R. Maniscalco 3 |
ABSTRACTOceanic climatic conditions in the Canary Islands were strongly related to conditions in the high-latitude North Atlantic Ocean throughout the last 3.6 m.y. We examined relative frequencies of planktonic foraminifers sampled from pelagic and hemipelagic units of the late Pliocene and Quaternary intervals of Site 953. Assemblages were defined using cluster analysis. Assemblages alternated between cool and warmer subtropical types during the Gauss Chron, with one cool event centered at ~3.3 Ma. Assemblages shifted abruptly to transitional types in the Matuyama and Brunhes Chrons. The shift, which began at 2.73 Ma, was marked by several apparent fluctuations between warmer and cooler assemblages culminating in a very rapid shift to a cool transitional assemblage at 2.5 Ma. Assemblages throughout the upper sequence alternated between cooler and warmer transitional types with a distinct change at 1.1 Ma to assemblages that were either slightly less well preserved or slightly cooler than those of the early Quaternary. The changes in assemblages coincided not only with assemblage changes at a higher latitude in the North Atlantic Ocean, but also with increasing aridity in the North Sahara region. Both events were connected to increased intensity of the northeast trade winds. The excellent stratigraphic record recovered at Leg 157 sites in the volcanic apron of Gran Canaria clearly ties various phases of island evolution to regional paleoclimatic history. |
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