Cretaceous sedimentary blanketing and tectonic rejuvenation in the Western Klamath mountains: Insights from thermochronology

Abstract

We present new thermochronometric analyses of 4 samples from the Western Klamath mountains in California and Oregon, together with a re-evaluation of available geological constraint from a thermo-tectonic perspective. Early Cretaceous cooling of basement samples is seen to reflect significant exhumation by normal faulting, linked to the Separation Episode during which the Klamath region was rifted away from the formerly contiguous Sierra Nevada block. Syn-faulting sedimentation and subsequent Early Cretaceous re-heating of samples establishes the former continuity of scattered Hornbrook Formation remnants as a significant sedimentary basin spanning the Klamath region, with local maximum thickness of at least 5 km. This basin experienced significant inversion during early Cordilleran development around 110-120 Ma, with further unroofing and almost complete eversion in the Late Cretaceous, associated with Laramide uplift of the region. © Versita Warsaw.