Tectonic rotations of the Santa Monica Mountains region, western Transverse Ranges, California, suggested by paleomagnetic vectors

Restraining segments and reactivation of the Santa Monica–Dume–Malibu Coast fault system, offshore Los Angeles, California

“…The Santa Monica Mountains block has undergone at least 75° of clockwise rotation since eruption of the 17.4–16.3 Ma ConejoVolcanics there, so long‐term average rotation exceeds 4.4°/m.y. [ Kamerling and Luyendyk , 1979; McCulloh et al , 2002; P. Gans, written communication, 19 October 2004]. The present rate of rotation of the Santa Monica Mountains is 7° ± 1°/m.y., as modeled from GPS data, a little faster than the postvolcanic rate [ Donnellan et al , 1993].…”

“…Subduction ceased during early Miocene time, leading to extension as the Pacific plate obliquely diverged from the North American Plate [ Lonsdale , 1991]. This motion and capture of part of the subducted slab by the Pacific Plate resulted in over 90° of Neogene clockwise rotation of the western Transverse Ranges (wTR) province [ Kamerling and Luyendyk , 1979; Nicholson et al ., 2004]. Removal of the wTR from its prerotation position alongside the Peninsular Ranges is related to large‐scale Miocene extension and tectonic denudation of the Inner California Continental Borderland (“Inner Borderland”; Figure 1) as subduction‐related thrusts were reactivated as (oblique) normal faults [ Yeats , 1976; Crouch and Suppe , 1993].…”

Tutorial on Rotations in the Theories of Finite Deformation and Micropolar (Cosserat) Elasticity

“…One of the tectonically important extant problems is the rotation about vertical axes of crustal blocks in continental areas of diffuse deformation. For example, the Western Transverse Ranges (WTR) in southern California have undergone a clockwise rotation of about 90°since the Miocene (Kamerling and Luyendyk, 1979). The WTR is a large block (about 150 × 80 km) and the areas to the north and south of it appear unrotated.…”

Mid-Tertiary isopach and lithofacies maps for the Los Angeles region, California: Templates for palinspastic reconstruction to 17.4 Ma

“…The block presumably became mostly detached from its deep crustal foundation, was accreted to the northwestwardly moving Pacific Plate, and then constrained to rift and rotate away from the North American Plate attachment, driven by Pacific Plate divergent motion through basal shear (Nicholson and others, 1994;Dickinson, 1996;Atwater and Stock, 1998;Bohannon and Geist, 1998). The central and western parts of the northwest sector participated substantially in the transrotational migrations (Kamerling and Luyendyk, 1979;Hornafius and others, 1986;Liddicoat, 1988Liddicoat, , 2001. It is unclear that the eastern extension of the northwest sector, east of longitude 118° 18' W and closer to the rotational hub, participated equally.…”

“…Conceptual understanding of the origin and evolution of the Los Angeles Basin and its surroundings-shown with selected geographic features, faults, and structural elements in figure 1-began a notable shift following publication of the first paleomagnetic evidence implying regional detachment, translation, and large ("about 70˚") clockwise steep-axis rotation of the western Santa Monica Mountains since early Miocene time (Kamerling and Luyendyk, 1979). Subsequent studies enlarged the paleomagnetic data base geographically and stratigraphically, made clear that the entire western Transverse Ranges Province (and some contiguous areas including the Channel Islands; see Kamerling and Luyendyk, 1985) have rotated more or less together as a block (Liddicoat, 1990), established that some younger formations record smaller rotations than some older formations (Hornafius and others, 1986), and suggest that declination has changed linearly since about 17 Ma at a rate of about "5.79 degrees/m.y."…”