Structures that accommodated differential vertical axis rotation of the western Transverse Ranges, California

Abstract

New paleomagnetic and structural data from the northwestern Transverse Ranges of California define the location, geometry, and kinematics of structures that facilitated differential vertical axis rotation. Paleomagnetic declinations in the southern Coast Ranges indicate negligible amounts of vertical axis rotation, which contrasts sharply with data from rocks of the same age in the western Transverse Ranges that record approximately 90° of clockwise rotation since early Miocene time. This change in paleomagnetic declinations occurs across an east-west trending zone of reverse faults and folds that includes the western Big Pine-Pine Mountain fault, the Santa Ynez fault, and the structures in between. The structures in this zone exhibit increased amounts of shortening to the west such that the zone closed in a fan-like fashion, resulting in rotation of the southern edge with respect to the northern edge. The new data and interpretations refine previous models of vertical axis rotation in southern California by describing the deformation present at rotation boundaries that allowed distinct areas to rotate relative to the surrounding crust. Copyright 2005 by the American Geophysical Union.