浅海堆積物の磁化強度が示す経時変動リズム

十二町層中部 (後期鮮新世) 堆積サイクルとの関係を中心に

抄録

As exemplified by the middle part (late Pliocene) of the Junicho Formation from Central Honshu (Japan), rock magnetic variability of the outer shelf deposits reveals a so close correlation between the sedimentary cyclicities both in lithologies and molluscan assemblages and the magnetic susceptibility as well as intensity, that a causal relationship between the rock magnetic characteristics and sea level oscillation is advocated. The rock magnetic variability is primarily attributed to the relative abundance of detrital ferromagnetic minerals which is controlled by shifting of proximity of the shoreline as the function of rise and fall of sea level with a short frequency such as few tens kys by glacio-eustacy.
Since a similar, if not identical, conclusion is attained from the both onboard (Davies et al., 1991) and onshore studies (Konishi and Ikehara, 1992) of the Hole 821 A of ODP Leg 133 on the upper shelf slope of the central Great Barrier Reef, it is anticipated that rock magnetic measurement of marine shallow-water sediments can be a viable and efficient means for an analyzing record of sea level change.