Surface uplift of the central Cascade Range, northwestern USA, via Oligocene to early Miocene crustal thickening

Abstract

Paleoelevation data from continental arcs provide a record of tectonic processes and reveal feedbacks between surface uplift and paleoclimate. Here we reconstruct the Oligocene–Miocene paleoelevation of the central Cascade arc (northwestern USA) using δD values of paleoprecipitation preserved within hydrated volcanic glass. From the early Oligocene to early Miocene (ca. 33–17 Ma), we observe a 30‰ decrease in δD values of samples collected east of the range. Interpreted using a Rayleigh distillation model, these data indicate arc elevations increased by 1.1 ± 0.4 km during this interval, coeval with geochemical evidence for a 12 km increase in Moho depth. In the context of existing geochemical, thermochronologic, and structural data, Oligocene to early Miocene surface uplift was predominantly driven by magmatic additions to the crust during a period of high magmatic production rates. Surface uplift was synchronous with leeward drying, suggesting that an orographic rain shadow was established by the early Miocene. These results highlight the role of crustal thickness and paleoelevation changes in controlling regional climate in magmatic arcs.