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Book Chapter

Cenozoic Stratigraphy of the Transverse Ranges and Adjacent Areas, Southern California

By
Michael O. Woodburne
Michael O. Woodburne
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Published:
January 01, 1975

Sedimentary basins within the Transverse Ranges and adjacent areas of Southern California are truncated by several branches of the San Andreas fault system. Comparison of basement and sedimentary successions of the Lockwood Valley-Cuyama Valley area with those of the Soledad Basin and western San Gabriel Mountains indicates that these districts have been separated by right-lateral slip on the San Gabriel and Sierra Madre faults. Right-lateral slip on the San Gabriel fault system may have been accomplished in two phases: (1) an interval of relatively rapid slip to account for 20 to 30 km of offset beginning in late Barstovian or early Clarendonian time and (2) a second interval to account for 18 to 28 km of offset after Clarendonian time. For the second interval, it is not possible to determine whether most of the offset occurred gradually throughout Hemphillian time or took place during some part of it. There may have been as much as 9 km of post-Hemphillian slip on the San Gabriel fault system. This post-Hemphillian interval, about the last 4 to 5 m.y., corresponds to the opening of the Gulf of California, so that it appears that most of the 48 km of right-lateral slip on the San Gabriel fault system had been accomplished prior to then. Post-Hemphillian slip on the San Gabriel and Sierra Madre faults appears to have been distinctly less than for other elements of the San Andreas fault system.

None of the branches of the San Andreas fault zone east of the San Gabriel fault appears to have undergone more than about 20 to 30 km of right-lateral slip during or after Hemphillian time, or during the past 10 m.y. or less. Even including 24 km of right-lateral slip on the San Jacinto fault zone, the aggregate slip on the San Andreas fault system during this time appears to be on the order of only 60 km, substantially less than required to compensate for the 250 km involved in the opening of the Gulf of California during the past 5 m.y.

If the Pinto Mountain fault is the eastern equivalent of the Malibu Coast–Cucamonga fault zone, essentially no right-lateral slip occurred on the San Gabriel fault from the Saucesian through the Luisian interval; east of the San Gabriel fault, essentially no slip occurred on the San Andreas fault from Saucesian through Mohnian time. This reconstruction is compatible with the range of slip on the San Andreas system proposed by Baird and others (1974). It also suggests that about 20 km of post-Eocene(?) slip occurred on the Punchbowl-Nadeau fault prior to Zemorrian time.

If the Pinto Mountain fault is not the eastern equivalent of the Malibu Coast–Cucamonga fault zone, and if the only slightly offset pre-Tertiary basement structures cited by Baird and others (1974) are merely fortuitous, there may have been more extensive pre-Hemphillian slip on the San Andreas system, as envisioned by Ehlig and Ehlert (1972) and Crowell and Walker (1962). This slip would be comparable in magnitude but not in timing with the 250-km slip associated with the opening of the Gulf of California.

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GSA Special Papers

Cenozoic Stratigraphy of the Transverse Ranges and Adjacent Areas, Southern California

Michael O. Woodburne
Michael O. Woodburne
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Geological Society of America
Volume
162
ISBN print:
9780813721620
Publication date:
January 01, 1975

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