STRUCTURAL STYLES AND DEFORMATION THAT CHARACTERIZE TRANSITION ZONES BETWEEN DIFFERENTIALLY ROTATED CRUSTAL BLOCKS. EXAMPLES FROM SOUTHERN CALIFORNIA

New structural, stratigraphic, and paleomagnetic data were collected along the northern edge of the rotated Western Transverse Ranges (WTR), southern California which have been rotated clockwise more than 90 degrees along the North American- Pacific Plate boundary during Late-Cenozoic time. These data were used to develop the first detailed description of the structural style and deformation present at the margins of rotated crustal blocks. The data suggests that the transition zone between the rotated WTR block and the nonrotated Coast Ranges to the north is characterized by 1 to 20 km wide westward-opening zone of northwest-trending folds and west- and northwest-striking reverse faults. Deformation was distributed throughout the zone but primarily accommodated by the larger faults at the edges of this zone, which increase in dip-separation to the west. Stratigraphic and paleomagnetic data show large contrasts across the Big Pine and Pine Mountain faults, suggesting that a large amount of displacement and approximately 70 degrees of rotation have been accommodated by these faults, and that these faults constitute the northern boundary of the WTR. The results and interpretations refine the kinematics of vertical-axis block rotation and lead to a field-based structural model for transition zones between differentially rotated domains.