Left-Shear and N-S Contraction In Monterey Formation, Northwestern Santa Barbara Channel, California: Structural Evidence In Support of Neogene Vertical Axis Rotation
An extensive (12 x 40 km) 3D seismic data set located in the northwestern Santa Barbara Channel provides excellent detail on the deformation of the Miocene Monterey Formation. These data reveal early deformation that supports the clockwise rotation and late deformation that supports the N-S contraction. The top Monterey stratigraphic horizon describes an east-trending, north-vergent anticline. Early deformation is best shown by a corridor of several discrete east-trending, relay overlapping faults that extends as a semi-continuous structural zone along the northern margin of the anticline. Late deformation is best shown by a (contractional) growth syncline. North of the fault corridor, the top Monterey dips steeply (35-55o) northward. South of the fault corridor, the Monterey dips gently (5-10o) south-southeastward across a region of distributed small faults and discrete, northwest-trending folds. On the basis of throw, faults can be divided into: 1) northeast-striking normal-separation faults, 2) northwest-striking reverse-separation faults, and 3) east-striking mixed-separation faults. Fault offsets die out up-section in the Mio-Pliocene Sisquoc. This pattern indicates distributed Miocene to Early Pliocene left-shear.