Early to Middle Miocene planktonic foraminiferal datum levels of the equatorial and subtropical Pacific ( DSDP).

Quantitative planktonic foraminiferal analysis of the equatorial and subtropical Pacific DSDP Sites 77B, 319 and 296 revealed more than 35 datum levels for the Early and Middle Miocene. Relative ages for these datum levels were derived from the estimated sediment accumulation rate of Site 77B, as calibrated by certain foraminiferal and radiolarian datum levels previously tied to the paleomagnetic record. Results agree with ages of Middle Miocene foraminiferal datum levels previously tied to the paleomagnetic record. But age differences are apparent in the Early Miocene datum levels. Several intervals marked by severe calcium carbonate dissolution are identified in the Early Miocene sequences. These intervals occur at about the same stratigraphic intervals in many deep-sea sections in the Pacific and form an important marker horizon; they appear to have been caused by sea level changes accompanied by major paleoclimatic fluctuations.-from Author