A paleomagnetic study has been carried out on a sequence of Oligocene and early Miocene marine glacial sediments recovered from DSDP Site 270 in the Ross Sea, Antarctica. The reversal stratigraphy for 30 to 240 meters below bottom compares closely with the early Miocene part of the sea-floor anomaly scale of Heirtzler et al. (1968). The linear relationship not only requires a constant sedimentation rate of 41 m/m.y., but at the same time confirms the regularity of polarity change for this part of the Heirtzler et al. scale. The interval from 240 to 370 meters below bottom is entirely normally magnetized, possibly because of a change in the magnetic character of the sediments due to the formation of magnetically unstable authigenic minerals. The sedimentation rate probably remained almost constant, because the same sedimentary facies occur throughout the glacial marine sequence, and because the three reversals from 370 to 384 meters, the base of the glacial sequence, indicate a sedimentation rate similar to that for the upper part. Comparison with the Heirtzler et al. scale and extrapolation of the sedimentation rate into the long "normal" interval places the Oligocene-Miocene boundary (22.5 m.y.) at 260 meters below bottom, compared with about 300 meters below bottom for the boundary based on benthonic foraminifera. The base of the glacial sequence is believed to be 25 m.y.