INSOLATION CYCLES AS A MAJOR CONTROL EQUATORIAL INDIAN-OCEAN PRIMARY PRODUCTION

Analysis of a continuous sedimentary record taken in the Maldives indi cates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the equatorial Indi an Ocean during the past 910,000 years. The record of primary producti on is coherent and in phase with the February equatorial insolation, w hereas it shows diverse phase behavior with delta(18)O, depending on t he orbital frequency (eccentricity, obliquity, or precession) examined . These observations imply a direct control of productivity in the equ atorial oceanic system by insolation. In the equatorial Indian Ocean, productivity is driven by the wind intensity of westerlies, which is r elated to the Southern Oscillation; therefore, it is suggested that a precession forcing on the Southern Oscillation is responsible for the observed paleoproductivity dynamics.