PALEOMAGNETIC AND GEOCHRONOLOGIC CALIBRATION OF LATEST OLIGOCENE TO PLIOCENE RADIOLARIAN EVENTS, EQUATORIAL PACIFIC

Eight chronologically overlapping piston cores from the central Equatorial Pacific, which range in age from latest Oligocene to Pleistocene and for which the magnetostratigraphy was known, served as a basis for a paleomagnetic and geochronological calibration of 75 radiolarian first appearances and extinctions. The species studied are commonly accepted as useful stratigraphic indices. Comparison with results of detailed studies of tropical Pacific DSDP drill-sites reveals excellent agreement in the sequence and timing of first appearances, as well as concurrence of many extinctions. The density of radiolarian events is highest in the Early Miocene, where an average of 0.24 my elapsed between each event. In the Late Miocene the density of events is lowest: not only is each datum level separated by an average of 0.52 my in this time unit, but it also contains the longest eventless interval (2.5 my) of the last 27 my. © 1978.