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Legg M, Goldfinger C, Kamerling MJ, Chaytor JD, Einstein DE. Morphology, structure and evolution of California Continental Borderland restraining bends. ACTA ACUST UNITED AC 2007. [DOI: 10.1144/sp290.3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractExceptional examples of restraining and releasing bend structures along major strike-slip fault zones are found in the California continental Borderland. Erosion in the deep sea is diminished, thereby preserving the morphology of active oblique fault deformation. Long-lived deposition of turbidites and other marine sediments preserve a high-resolution geological record of fault zone deformation and regional tectonic evolution. Two large restraining bends with varied structural styles are compared to derive a typical morphology of Borderland restraining bends. A 60-km-long, 15° left bend in the dextral San Clemente Fault creates two primary deformation zones. The southeastern uplift involves ‘soft’ turbidite sediments and is expressed as a broad asymmetrical ridge with right-stepping en echelon anticlines and local pull-apart basins at minor releasing stepovers along the fault. The northwest uplift involves more rigid sedimentary and possibly igneous or metamorphic basement rocks creating a steep-sided, narrow and more symmetrical pop-up. The restraining bend terminates in a releasing stepover basin at the NW end, but curves gently into a transtensional releasing bend to the SE. Seismic stratigraphy indicates that the uplift and transpression along this bend occurred within Quaternary times. The 80-km-long, 30–40° left bend in the San Diego Trough–Catalina fault zone creates a large pop-up structure that emerges to form Santa Catalina Island. This ridge of igneous and metamorphic basement rocks has steep flanks and a classic ‘rhomboid’ shape. For both major restraining bends, and most others in the Borderland, the uplift is asymmetrical, with the principal displacement zone lying along one flank of the pop-up. Faults within the pop-up structure are very steep dipping and subvertical for the principal displacement zone. In most cases, a Miocene basin has been structurally inverted by the transpression. Development of major restraining bends offshore of southern California appears to result from reactivation of major transform faults associated with Mid-Miocene oblique rifting during the evolution of the Pacific–North America plate boundary. Seismicity offshore of southern California demonstrates that deformation along these major strike-slip fault systems continues today.
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Affiliation(s)
- M.R. Legg
- Legg Geophysical, Huntington Beach, CA 92647, USA (e-mail: )
| | - C. Goldfinger
- College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | | | - J. D. Chaytor
- College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - D. E. Einstein
- Southern California Earthquake Center, Los Angeles, CA 90089, USA
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Sorlien CC, Kamerling MJ, Seeber L, Broderick KG. Restraining segments and reactivation of the Santa Monica-Dume-Malibu Coast fault system, offshore Los Angeles, California. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jb003632] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Marc J. Kamerling
- Institute for Crustal Studies; University of California; Santa Barbara California USA
| | - Leonardo Seeber
- Lamont-Doherty Earth Observatory; Columbia University; Palisades New York USA
| | - Kris G. Broderick
- Institute for Crustal Studies; University of California; Santa Barbara California USA
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