LATE QUATERNARY VARIATIONS OF SEA-SURFACE SALINITY AND TEMPERATURE INTHE WESTERN TROPICAL ATLANTIC - EVIDENCE FROM DELTA-O-18 OF GLOBIGERINOIDES SACCULIFER

In order to reconstruct hydrographic changes during glacial-interglaci al cycles for a transequatorial transect we analyzed oxygen isotopes o f Globigerinoides sacculifer (without sac-like chamber) and abundances of Globorotalia truncatulinoides (dextral) from FS Meteor cores GeoB 2204-2 (Brazilian continental slope)and GeoB 1523-1 (Ceara Rise). Delt a delta(18)O values of G sacculifer between the two cores were calcula ted. Modern Delta delta(18)O (G. sacculifer) is similar to 0.2 parts p er thousand between the two core positions, reflecting differences in sea surface salinity (SSS). Higher SSS at GeoB 1523-1 (Ceara Rise) is the result of increased precipitation in the region of the Intertropic al Convergence Zone. During glacials the delta(18)O records from the t wo cores converge to the same absolute value, resulting in Delta delta (18)O values of around 0 parts per thousand. Maximum abundances of G. truncatulinoides (dex) correlate with minimum Delta delta(18)O, sugges ting a possible increase of SSS at GeoB 1523-1 during stages 2, 3, 4, and 6, which is related to a glacial weakening of the tropical Hadley Cell [Gates, 1976]. Variations in tropical sea surface temperatures ar e assumed to be low [Climate: Long-Range Investigation, Mapping, and P rediction (CLIMAP), 1981].