Oligocene onset of uplift and inversion of the Cascadia forearc basin, southern Oregon Coast Range, USA

An extensive detrital zircon U-Pb data set (n = 6324 dates) from Eocene to Miocene sandstones and modern river sands establishes the onset of arc magmatism forearc uplift along Cascadia convergent margin in southwestern Oregon (United States). Middle late marine strata Coos Bay area were primarily sourced Klamath Mountains coeval Clarno-Challis volcanoes central and/or Idaho. Ancestral Cascades initiated at 40 Ma supplied sediment a broad basin western during time. Major reduction (40–12 Ma) (52–40 Tunnel Point Sandstone (ca. 33–30 records isolation due Oligocene uplift, inversion, emergence southern Coast Range. The Tarheel formation 18–15 is characterized by disappearance substantial increase recycled underlying strata. ~15–20 m.y. delay between subduction initiation 49–46 supports insights thermomechanical models that identify tectonic underplating thermally activated lower-crustal flow as major drivers deformation active regions.