Short geomagnetic episodes in the Matuyama epoch

Abstract

Two short geomagnetic episodes in the middle Matuyama epoch have been identified within thin (4.3-mm) sections of two deep-sea calcareous sediment cores taken in the western equatorial Pacific. Both cores are correlated by magnetostratigraphic and micropaleontological methods. Magnetic stability and paleomagnetic reliability are tested by alternating field demagnetization of natural remanent magnetization as well as by the ratios of intensities of anhysteretic remanent magnetization to those of saturation isothermal remanent magnetization. One episode is dated to be 1.06 m.y. BP. The other is identified to be about 1.94 m.y. BP, which is presumably in agreement with the Reunion event. Both episodes seem to be accompanied by conspicuous drops in field intensity. Possible correlation of field intensity with biological productivity in the ocean is also postulated from the present paleomagnetic results.