Abstract
The paleogene stratigraphic sequence exposed in the southwestern San Rafael Mountains at the southern terminus of the Coast Ranges, consists of up to 850 m (2,800 ft) of the marine limestone, sandstone, and mudstone that lies with a unique depositional contact upon Franciscan Complex rocks. Lithofacies identified represent four sedimentary environments: (1) foreslope talus deposits of a neritic algal bank (Sierra Blanca limestone), (2) bathyal basin plain and outer submarine fan deposits (Juncal/Anita Formation and Cozy Dell Shale), (3) suprafan lobe deposits of a bathyal submarine fan (lower Mitilija Sandstone), and (4) sublittoral shelf deposits (upper Matilija Sandstone). Similarities between paleogene rocks in the southwest San Rafael mountains and the western Santa Ynez Mountains of the Transverse Ranges, approximately 60 km (40 mi) to the west, suggest deposition in a similar paleogeographic setting. Paleomagnetic data suggests post-Paleogene clockwise rotations of the western Transverse Ranges of 90{degree}+. Counterclockwise rotation of the western Transverse Ranges by this amount aligns the similar depositional sequences of the western Transverse Ranges with the northwest-trending Paleogene forearc basin of the southern Coast Ranges and eliminates the necessity for an east-west-oriented Paleogene basin at the site of the present western Transverse Ranges.
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