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 inves tigated over the last 140 ka by comparing material from two sediment cores: one from the highly productive equatorial divergence of the eastern Atlant ic Ocean and the other from the low productivity western tropical Atlantic Ocean. Pronounced differences in palaeoproductivity between the two sedimen t cores are indicated by high and variable organic carbon accumulation rate s in the east, in contrast to relatively constant and low values in the wes t. Calcareous dinoflagellates show just the opposite pattern: high accumula tion rates in the west and lower in the east. At the equatorial divergence, temporal variations of calcareous dinoflagellate and organic carbon accumu lation rates show, for the most part, an inverse relationship. High calcare ous dinoflagellate content coincides with low organic carbon accumulation r ates and vice verse. In the investigated region and time interval, enhanced production of calcareous dinoflagellates can be correlated to periods of r educed palaeoproductivity probably related to relatively stratified conditi ons of the upper water column. (C) 1999 Elsevier Science B.V. All rights re served.