LATE JURASSIC TO EARLY CRETACEOUS COVER SEQUENCES IN THE KLAMATH MOUNTAINS PROVIDE CLUES FOR SEDIMENT PATHWAYS AND CORRELATION WITH THE NORTHERN SIERRA NEVADA

There are debated tectonic models for Mesozoic subduction in North America. The number, direction, and timing of the subduction zones remain unclear. The Klamath Mountains straddle the California-Oregon border and are made of multiple accreted terranes. To address this problem of conflicting models, we investigated the late Paleozoic to early Mesozoic Eastern Hayfork terrane, a mélange subduction complex. We present U-Pb zircon analyses from sedimentary and volcanic samples. Two samples yielded ages younger than the plutons cross-cutting the Eastern Hayfork terrane: 158 Ma in the central Klamaths and 141 Ma in the south. These are definitively not part of the Eastern Hayfork terrane. Both samples have single age peaks. The central Klamath sample could be sourced from neighboring early Late Jurassic plutonic rocks. The Galice formation to the west has similar ages but includes significant pre-Mesozoic ages, potentially indicating sedimentary transport from east to west. In contrast, there are no known ~140 Ma sources in the Klamath Mountains for the southern sample. However, Early Cretaceous plutonic rocks intrude the northernmost Sierra Nevada Mountains, providing further evidence of their correlation with the Klamath Mountains before offset at 135 to 130 Ma. Pre-Late Cretaceous post-amalgamation cover sequences provide insight into sediment pathways and exhumation during this time period.