32 Mesozoic-Cenozoic Orogenesis Along the Pacific Northwest Cordilleran Margin (Posters)

Friday, 4 April 2025
8:00 AM - 4:00 PM
Sierra Ballroom

ACTIVE FAULTING WITHIN THE KLAMATH MOUNTAINS PROVINCE REVEALED BY LiDAR DATA

Paper number: 32-4
Program: Theme Sessions
Time: 8:00 AM – 4:00 PM

Authors

Abstract

The Klamath Mountains province (KMP) in Northern California is undergoing active deformation in response to tectonic forces that act on its boundaries. This region lies onshore of the Mendocino Triple Junction, which continuously replaces the Cascadia Subduction Zone with the San Andreas Fault as it migrates north. This migration in turn drives NNW translation of the rigid Sierra Nevada-Great Valley (SNGV) block which impinges upon the southern margin of the KMP. North of the KMP, the rigid Oregon Coast Block rotates clockwise to accommodate SNGV block motion as well as Basin and Range extension. Analysis of GPS velocity vectors indicates differential motion between the rapidly translating SNGV block and the slower rotating Oregon Coast Block. Given the rigid motion of surrounding blocks, observed differential motion should produce observable deformation within the KMP. Despite this, mapped active faults are conspicuously absent within the KMP, which has therefore been treated as either a separate rigid block or as part of the Oregon Coast Block. Yet the KMP should not behave rigidly; it is a collage of accreted terranes that should be rheologically weak compared to the strong, mafic crust bounding it to the north and south. Here we show that the KMP is not a rigid block after all, but rather transected by active faults that deform the region in response to the complex boundary conditions on its margins. These active faults have gone unnoticed until now because the region is elevated, eroding, and densely forested. Preliminary analysis of recently released lidar data reveals the presence of three new active fault strands within the KMP. Further study of these faults will constrain the rate and style of active deformation within the KMP as well as seismic hazards within the region.

Geological Society of America Abstracts with Programs. Vol. 57, No. 4

doi: 10.1130/abs/2025CD-410135

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