Short period geomagnetic polarity events in deep-sea sedimentary cores

Abstract

It is suggested that inconsistencies in detailed results from paleomagnetic studies of marine sedimentary cores are to be expected in segments close to polarity boundaries, because of the creation of a zone or redeposition up to 50 cm deep by benthonic faunal activity. Even with constant sedimentation, geomagnetic polarity events may not remain recorded in such cores. Reliable delineation of the fine structure of the geomagnetic polarity history by paleomagnetic studies of deep-sea sedimentary cores is therefore unlikely unless cores of sufficient length are collected from areas of unusually high sedimentation rate and/or very low biological activity. With these reservations, the paleomagnetism of a series of selected cores from the Southern Ocean are presented. It is shown that the possibility of short normal polarity events at t = 0.82 and 1.07 million years is supported by the data. Verification by independent means is essential, however, before these suggested polarity changes can be accepted as real.