--> Abstract: 3D Tectonostratigraphic Development of the Los Angeles Basin as Viewed Through the Beta 3D Seismic Survey, by K. D. Kelsch and T. L. Heidrick; #90935 (1998).
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Abstract: 3D Tectonostratigraphic Development of the Los Angeles Basin as Viewed Through the Previous HitBetaNext Hit 3D Seismic Survey

KELSCH, K. D., T. L. HEIDRICK, PT Caltex Pacific, Indonesia; and E. G. FROST, San Diego State University, San Diego, CA

Previous HitBetaNext Hit 3D marine reflection seismic survey was interpreted from the structurally complex SW extension of the Los Angeles basin. The survey covers 244 km2, extends south of the Palos Verdes uplift and borders the THUMS-Huntington Beach fault. Previous HitBetaTop field data including dipmeter, checkshot surveys and wireline logs were used to decipher the tectonostratigraphic evolution.

Four distinct deformational phases were identified. The oldest phase (S[0]) involves only pre-Miocene basement. So is dominated by uplift related to pre-Miocene oblique subduction. Transtensional deformation (S[1]) prevails from 24-12 Ma. S[1] deformation is characterized by arrays of domino-style planar normal faults linked at depth to detachment at 5.0 km. S1, transtension appears coeval with regional crustal extension in the American Southwest and is genetically related to it. S1 synorogenic sediments represent early to mid-Miocene San Onofre Breccia. The end of S1, is contemporaneous with the termination of mid-Miocene calc-alkaline volcanism and clockwise rotation of micro-plates. S[2] deformation is partitioned into two subphases (S[2]E and S[2]L). Right-lateral strike-slip faulting dominates S[2]. S[2]E is characterized by activation of NNW-trending leftstepping Palos Verdes fault and cogenetic NNE-trending transtensional normal faults. S2L appear coeval with the initiation of the southern San Andreas transform and the opening of the Gulf of California. Pliocene Repetto sands document the end of S[2]L tectonism. Channels up to 2 km across formed during S[2L] and are truncated by the NNW-striking en echelon Palos Verdes fault. NW-trending antiforms occur internally to the Palos Verdes fault zone and are localized at restraining bends indicative of S[2L] right-lateral movement. S[3] involves compressional deformation and is tectogenetically related to the modern-day San Andreas Transverse Ranges restraining bend geometry. S[3] overprints S[2] offsets along the Palos Verdes fault and is reflected by the regional Plio-Pleistocene unconformity.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California