• journal_title：Geology
• Contributor：Kazuto Kodama ; Tohru Takeuchi ; Tomowo Ozawa
• Publisher：Geological Society of America
• Date：1993-
• Format：text/html
• Language：en
• Identifier：10.1130/0091-7613(1993)021<0431:CTROTS>2.3.CO;2
• journal_abbrev：Geology
• issn：0091-7613
• volume：21
• issue：5
• firstpage：431

Paleomagnetic data from Tertiary sedimentary strata in the Yubari and Haboro areas of central Hokkaido indicate consistently clockwise-deflected magnetic declinations. The mean declination of middle middle Miocene rocks deviates 21° ±5° from the Eurasian reference direction, and that of the Oligocene to lower middle Miocene rocks deviates 30° ±21°. This suggests that these sedimentary basins have rotated 10°-30° clockwise about a vertical axis since the middle Miocene. These clockwise rotations can be explained by a right-lateral displacement of a shear zone in central Hokkaido. This study demonstrates that central Hokkaido is not simply a single tectonic unit of northeast Japan characterized by counterclockwise rotations from early to middle Miocene time.