Abstract
Paleomagnetic and geologic studies were made in the Uetsu area, NE Japan, to clarify the Miocene intra-arc deformation associated with the Japan Sea opening. We obtained paleomagnetic directions from the Early to Middle Miocene pyroclastic rocks and lavas in the area. The average paleomagnetic direction is D = 28.0°, I = 48.7° andα95 = 9.6°. It suggests that the clockwise rotation occurred in this area, which is opposite to the counter-clockwise rotation of NE Japan. A fault was discovered which could be the boundary of this rotating domain. The dextral movement is recognized for this fault, concordant with the clockwise rotation in the area. These paleomagnetic and structural data suggest that the clockwise block rotations occurred in the Uetsu area, accompanied by the dextral deformation.
