Palaeoenvironmental information gained from calcareous dinoflagellates:: the late Quaternary eastern and western tropical Atlantic Ocean in comparison

The environmental preferences of calcareous dinoflagellates have been investigated over the last 140 ka by comparing material from two sediment cores: one from the highly productive equatorial divergence of the eastern Atlantic Ocean and the other from the low productivity western tropical Atlantic Ocean. Pronounced differences in palaeoproductivity between the two sediment cores are indicated by high and variable organic carbon accumulation rates in the east, in contrast to relatively constant and low values in the west. Calcareous dinoflagellates show just the opposite pattern: high accumulation rates in the west and lower in the east. At the equatorial divergence, temporal variations of calcareous dinoflagellate and organic carbon accumulation rates show, for the most part, an inverse relationship. High calcareous dinoflagellate content coincides with low organic carbon accumulation rates and vice verse. In the investigated region and time interval, enhanced production of calcareous dinoflagellates can be correlated to periods of reduced palaeoproductivity probably related to relatively stratified conditions of the upper water column. (C) 1999 Elsevier Science B.V. All rights reserved.