COMPARISON OF QUATERNARY COASTAL UPWELLING PROXIES OFF CENTRAL PERU

Three APC (advanced hydraulic piston core) holes of ODP Leg 112 from the shelf (Sites 681 and 680) and upper slope (Site 686) off the central Peruvian coast contain a productivity and coastal upwelling record of the last 400,000 yrs. Marine planktonic diatom sediment assemblages are used as primary productivity proxies; their downcore record is compared to variations in other proxies: weight percent organic-carbon, percent large diatoms in the coarse fraction, delta C-13 of the endobenthic foraminifer Bolivina seminuda and the geochemical parameter Uk37 (unsaturation index of C37 alkenonones). Low values of calculated primary paleo-productivity are matched by low values of organic-carbon, but the percentages of diatoms in the coarse fraction do not follow this trend. Levels of delta C-13 correspond to neither the diatom productivity proxy nor the organic-carbon proxy. The geochemical index Uk37 seems to indicate high surface water temperatures whereas the calculated primary productivity indicates increased upwelling and thus lower temperatures.