CONFIGURATION OF MIOCENE BASINS ALONG THE SANTA CRUZ-CATALINA RIDGE, CALIFORNIA CONTINENTAL BORDERLAND

Miocene basins associated with the oblique rifting of the Inner Continental Borderland offshore Southern California are preserved along the flanks of the transpressional Santa Cruz-Catalina Ridge. Using 184 lines of two-dimensional seismic data including high resolution records from Oregon State University and deep penetration data from Western Geco archived in USGS/NAMSS, we were able to map the configuration of the Miocene basin for 80 kilometers along the northeast flank of the Santa Cruz-Catalina Ridge core complex. Our mapping area is about 1,280 square kilometers. There are distinct middle and late Miocene basins along the flanks of the ridge, which we are using to try to define the initial configuration of the Inner Borderland Rift. Along the hinge, between the uplifted ridge and the sub-horizontal basement in the Santa Monica Basin, and adjacent to the Transverse Ranges lies the thickest parts of the late Miocene sequence, ranging from 750 to 950 meters thick. The middle Miocene basin has distinct sub-basins, with maximum thicknesses of 1400 to 1800 meters, between acoustic basement highs. Pliocene to Recent sediments lap on to the tilted and uplifted Miocene basin sequences and constrain timing of uplift when transpression commenced. Segmentation and other distinctive character of the Miocene basins along the ridge flank may be correlated with similar features in the Miocene basin on the conjugate margin of the rift. Our working model for oblique rifting in the Borderland resembles the Gulf of California, where right-stepping echelon transform faults link left-stepping extensional basins. The objective of our project is to reconstruct the configuration of the middle Miocene rift and to further our quest to understand the rifting process and tectonic evolution of the Pacific-North American plate boundary.