MAGNETO-BIOSTRATIGRAPHY OF UPPER CRETACEOUS SYSTEM IN JAPAN

对北海道中部的上白垩统野三群进行了一系列的磁地层研究。在德潮-中川地区沿阿贝士奈河及其支流分布的奥苏士奈组上部，可识别出4个正极性或反极性磁带。此外，在Haboro地区Haborogawa组最上部还可识别出一对正极性和反极性磁带。将这些磁带与地磁极性时间尺度进行比较，可以得到磁极性解释，即四个磁带可以从上到下与晚白垩世磁极性时间C32r相关。1 r, C32r。1 n, C32r。2r和C33n。在宏观化石地层学上，Sphenoceramus schmidti带与C32r极性时相对应。1r，东蝶带至C32r。1n， polytychoceras pseudogaultinum带的上部至C32r.2r。对九州地区上白垩统古地磁组进行了古地磁研究，包括Goshoura群、miifune群、Ohnogawa群、Konmon上群等。这些地层均为正极性，与白垩纪长正极性年表C34n相对应。

A line of magnetostratigraphic studies were done focusing on the upper Cretaceous Yezo Group in central Hokkaido. Four magnetozones of normal or reversed polarity were recognized from the upper part of the Osoushinai Formation distributed along the Abeshinai River and its tributaries in Teshio-Nakagawa area. In addition, a pair of normal and reversed polarity magnetozones were recognizable from the uppermost Haborogawa Formation in Haboro area. Comparison of these magnetozones with a geomagnetic polarity time scale led to a possible magnetic polarity interpretation that the four magnetozones could be correlated from top to bottom to the late Cretaceous magnetic polarity chrons C32r.1r, C32r.1n, C32r.2r, and C33n. In terms of macro-fossil stratigraphy, the Sphenoceramus schmidti zone is correlated to polarity chron C32r.1r, the Sphenoceramus orientalis zone to C32r.1n, and the upper part of the Polyptychoceras pseudogaultinum zone to C32r.2r.Paleomagnetic studies were also conducted for the upper Cretaceous strata in Kyushu including the Goshoura Group, the Mifune Group, the Ohnogawa Group, and the upper Konmon Group. All these strata are of normal polarity correlatable to the Cretaceous long normal polarity chron, C34n.