Pace of landscape evolution in the Sierra Nevada, California, revealed by cosmogenic dating of cave sediments

We report (super 26) Al/ (super 10) Be based ages of Sierra Nevada caves that constrain detailed late Pliocene and Quaternary river incision histories for five river canyons. Rapid incision of approximately 0.2 mm/yr from 2.7 to ca. 1.5 Ma slowed markedly to approximately 0.03 mm/yr thereafter, likely reflecting the combined effects of a transient erosional response to Pliocene rock uplift and periodic mantling of riverbeds with glacially derived sediment in the late Quaternary. While approximately 400 m of incision has occurred in the past 2.7 m.y., outpacing interfluve erosion and thereby increasing the local relief, canyons as deep as 1.6 km existed prior to that time. These new erosion rates strengthen the case for tectonically driven late Cenozoic uplift.