Characterizing strain between rigid crustal blocks in the southern Cascadia forearc: Quaternary faults and folds of the northern Sacramento Valley, California

Abstract

Topographic profiles across late Quaternary surfaces in the northern Sacramento Valley (California, USA) show offset and progressive folding on series of active east- and northeast—trending faults and folds. Optically stimulated luminescence ages on deposits draping a warped late Pleistocene river terrace yielded differential incision rates along the Sacramento River and indicate tectonic uplift equal to 0.2 ± 0.1 and 0.6 ± 0.2 mm/yr above the anticline of the Inks Creek fold system and Red Bluff fault, respectively. Uplift rates correspond to a total of 1.3 ± 0.4 mm/yr of north-directed crustal shortening, accounting for all of the geodetically observed contractional strain in the northern Sacramento Valley, but only part of the far-field contraction between the Sierra Nevada–Great Valley and Oregon Coast blocks. These structures define the southern limit of the transpressional transition between the two blocks.

Robust Imaging of Fault Slip Rates in the Walker Lane and Western Great Basin From GPS Data Using a Multi‐Block Model Approach

“…North of Lake Tahoe the NWL shear strain rates are lower (∼40 × 10 −9 /yr) than to the south (>80 × 10 −9 /yr) and confined to a narrow zone between the Pyramid Lake and Mohawk Valley Faults, narrowing even further north to lie between the Eagle Lake and Almanor Faults. Further north still a pocket of medium‐high strain rates (∼50 × 10 −9 /yr) lies at the Inks Creek, Battle Creek, and Bear Creek faults, a place that may represent the locus of active convergence between the SNGV and crustal blocks in the southern Cascadia forearc (Angster et al., 2020; Unruh & Humphrey, 2017).…”

Robust Imaging of Fault Slip Rates in the Walker Lane and Western Great Basin from GPS Data Using a Multi-Block Model Approach

“…Just north of the SWL, the shear steps left and concentrates, passing through the Long Valley Caldera near the SNGV (shown in detail in Hamond et al, 2019) and then widens again northward. Here the higher shear strain rates occupy all the area between the SNGV and northwest striking dextral fault systems east of Walker Lake such as Petrified Spring, Benton Spring, and Gumdrop Hills faults (Wesnousky, 2005;Angster et al, 2020). However, shear rates are highest at the east and west margins of the CWL, near the SNGV and east of the Wassuk Fault.…”

“…North of Lake Tahoe the NWL shear strain rates are lower (~40 x 10 -9 /yr) than to the south (>80 x 10 -9 /yr) and confined to a narrow zone between the Pyramid Lake and Mohawk Valley Faults, narrowing even further north to lie between the Eagle Lake and Almanor Faults. Further north still a pocket of mediumhigh strain rates (~50 x 10 -9 /yr) lies at the Inks Creek, Battle Creek, and Bear Creek faults, a place that may represent the locus of active convergence between the SNGV and crustal blocks in the southern Cascadia forearc (Unruh et al 2017;Angster et al, 2020).…”

Mid-Miocene to Present Upper-Plate Deformation of the Southern Cascadia Forearc: Effects of the Superposition of Subduction and Transform Tectonics

“…The two terranes are currently adjacent, suggesting the material in this gap has either shortened and led to crustal thickening or underthrust the KMP. Seismicity and several east and northeast-oriented faults and folds in the northernmost region of the Great Valley and surrounding regions are indicative of north-south/northwest-southeast shortening between the Great Valley block and KMP (Unruh et al, 2003;Unruh and Humphrey, 2017;Angster et al, 2020), suggesting that at least some of this gap-closure is accommodated by upper-plate shortening.…”