Paleomagnetism and radiochemical age estimates for Late Brunhes polarity episodes

Several reversed polarity magnetozones occur within deep-sea sediment core CH57-8 from the Greater Antilles Outer Ridge, within sediment of latest Pleistocene/Late Brunhes age. The uppermost reversed interval spanning 31 data points coincides with the X faunal zone of the Last Interglacial Period. Radiochemical dating of cores CH57-8 and KN25-4 has shown that all the reversed polarity magnetozones are significantly younger than the Brunhes/Matuyama boundary at 0.7 m.y. B.P. A variation of the excess²³⁰Th method was used, in which²¹⁰Po and²³⁸U were the actual radionuclides measured. In a third core from the Mid-Atlantic Ridge, our²¹⁰Po results were similar to those which others obtained earlier by direct²³⁰Th measurements.