EARLY PLIOCENE DEEP-WATER CIRCULATION IN THE WESTERN EQUATORIAL ATLANTIC - IMPLICATIONS FOR HIGH-LATITUDE CLIMATE-CHANGE

High-resolution (similar to 3-4 kyr) stable isotope stratigraphies fro m sites drilled along a depth transect on Ceara Rise (Ocean Drilling P rogram Leg 154, Sites 925 and 929) are used to reconstruct the deep wa ter circulation response to the long-and short-term climate changes of the early Pliocene (3.2-4.7 Ma). Over the long term, benthic foramini feral carbon isotope records show that the vertical delta(13)C gradien t in this region was similar to that of the late Holocene, implying a steady flux of Northern Component Deep Water (NCDW) into the deep Atla ntic during most of the early Pliocene. The vertical benthic foraminif eral oxygen isotope gradient is reversed with respect to that of the l ate Holocene. On the basis of density constraints imposed by seawater stability along this depth transect we attribute the reversed gradient to warmer and more saline NCDW (5 degrees C and 35.1). On orbital tim escales we find that the phase relationship between delta(18)O and del ta(13)C values at the deeper Site 929 differs from the late Pliocene/P leistocene, while that at the shallower Site 925 was essentially the s ame.