HIGH-RESOLUTION PLIOCENE PLEISTOCENE RADIOLARIAN STRATIGRAPHY OF THE TROPICAL INDIAN-OCEAN

We refined the positions of 31 Plio-Pleistocene radiolarian datum leve ls by examining 3 paleomagnetically dated cores and comparing results with 4 previously studied cores from the Central Indian Basin. When no t affected by hiatuses or drastic changes in rates of sedimentation, a bsolute ages of radiolarian events in multiple cores from this restric ted geographic area are precise to within 0.05 million years. Some eve nts are complicated by minor morphotypic changes at the beginning or e nd of ranges or within evolutionary lineages; species definitions have to be restricted accordingly. Further study of these variations withi n an accurate chronostratigraphic framework should permit determinatio n of the rates of these evolutionary changes.