The block rotation in the Uetsu area, Northern Part of Niigata Prefecture,Japan

Paleomagnetic and geologic studies were made in the Uetsu area, NE Japan, t o clarify the Miocene intra-arc deformation associated with the Japan Sea o pening. We obtained paleomagnetic directions from the Early to Middle Mioce ne pyroclastic rocks and lavas in the area. The average paleomagnetic direc tion is D = 28.0 degrees, I = 48.7 degrees and alpha (95) = 9.6 degrees. It suggests that the clockwise rotation occurred in this area, which is oppos ite to the counter-clockwise rotation of NE Japan. A fault was discovered w hich could be the boundary of this rotating domain. The dextral movement is recognized for this fault, concordant with the clockwise rotation in the a rea. These paleomagnetic and structural data suggest that the clockwise blo ck rotations occurred in the Uetsu area, accompanied by the dextral deforma tion.