Paleomagnetism of Some Neogene Sedimentary Rocks on Oga Peninsula, Japan

Abstract

The Oga Peninsula Neogene section in Japan was sampled for paleomagnetic studies. The results show that the upper Wakimoto formation is normally magnetized and the lower Wakimoto, Kitaura and uppermost Funakawa formations are reversely magnetized. The remainder of the Funakawa and the Onnagawa formation are interpreted as being remagnetized and unreliable for magnetic stratigraphy.
The saturation IRM intensity was found to be an effective method of normalizing the effects of magnetic mineral content variation on the NRM intensity. Variations in the NRM intensity in these samples were paralleled by variations in SIRM intensity indicating that they are mineralogically rather than field controlled. The secondary component of magnetization in these rocks is believed to be a VRM acquired over the Brunhes normal epoch. Intensities and stabilities of the secondary component are compatible with the results from the VRM experiments conducted in the laboratory.
Due to the fact that only one reliable reversal was found in the section, age interpretations based on the magnetic stratigraphy were difficult to make. Tentative age assignments were postulated based on the interpretations of the diatom evidence by BURCKLE (1971).