Rotation of the southernmost Sierra Nevada, California

Abstract

Structural, paleogeographic, and magmatic trends of the Sierra Nevada batholith swing from a characteristic NNW trend in the northern and central parts of the batholith to a nearly E‐W trend in the Tehachapi and San Emigdio mountains. Paleomagnetic results from eight sites in the upper Cretaceous (80–86 m.y.) Bear Valley Springs pluton in the Tehachapi Mountains yield a mean direction D = 022°, I = 56° (k = 97, α95 = 5.6°). This mean direction is significantly different from the expected late Cretaceous field direction for this locality and suggests that the pluton has undergone a clockwise rotation of 45° ± 14°, in accord with the change in structural trend in that area. Lower to middle Miocene volcanic and sedimentary rocks of the Kinnick Formation overlie the plutonic rocks and yield a mean direction D = 354°, I = 64°. A paleomagnetic pole derived from this mean direction is not significantly different from the expected Miocene pole for North America. This constrains the time of rotation of the pluton to be between about 80 and 20 m.y., probably predating establishment of the present San Andreas transform in this area. We suggest that the observed rotation is part of a large oroclinal bend affecting to different degrees the entire southern Sierra Nevada. The driving mechanism for such a bending may be right‐lateral shear along a proto‐San Andreas transform, for which there is now a significant body of evidence.

Temporal and spatial trends of Late Cretaceous-early Tertiary underplating Pelona and related schist beneath southern California and southwestern Arizona

“…Balancing the complex gaps and overlaps that would result from removing the slip on these faults is beyond the scope of this study. For similar reasons, we did not correct for inferred rotations in the eastern Transverse Ranges or southern Sierra Nevada and Mojave Desert (Kanter and McWilliams, 1982;Luyendyk et al, 1985;Dokka and Ross, 1995). Nor did we take into account middle to late Tertiary extension, which affected the region from Death Valley southeastward to the corridor of the lower Colorado River (e.g., Davis and Coney, 1979), despite the fact that extension has greatly altered the surface geology compared to Late Cretaceous-early Tertiary time.…”

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“…The biggest challenge in "seeing through" post-Cretaceous deformation in the southern Sierra Nevada batholith and vicinity, after restoring slip along Neogene faults, is accounting for apparent clockwise vertical axis rotations of up to 90° in the region (Kanter and McWilliams, 1982;McWilliams and Li, 1983;Dokka and Ross, 1995;Wood and Saleeby, 1997;Nadin and Saleeby, 2008;Hopson et al, 2008). In short, a signifi cant fraction of observed clockwise rotation in the southern Sierra Nevada batholith is thought to have taken place during Late Cretaceous extension (Malin et al, 1995;Saleeby, 2003;Chapman et al, 2010) and post-Cretaceous vertical axis rotation probably did not result in signifi cant additional dispersion of upper crustal fragments in the southern Sierra Nevada batholith, with the exception of the San Emigdio Mountains, which accommodated ~7 km of north-south shortening since late Pliocene time (Davis, 1983).…”

Structural Evolution of the East Sierra Valley System (Owens Valley and Vicinity), California: A Geologic and Geophysical Synthesis

“…A hypothetical linear connection between the T-pOVF and the San Andreas Fault can be envisioned along the east side of the Sierra Nevada by restoring clockwise rotation of the southern Sierran tail ( Figure 12). Some early San Andreas movement could have been accommodated on such a fault prior to 20 Ma, when rotation of the Sierran tail had been completed [111]. The apparent structural alignment of similar Paleozoic rocks in the southern Sierra Nevada and the El Paso Mountains [112], however, which would be on opposite sides of such a fault, argues against this hypothesis.…”