Plio‐Pleistocene Ash Falls, Sedimentation, and Range‐Front Faulting Along the White‐Inyo Mountains Front, California

40Ar/39Ar dating of rhyolitic ashes from the western range front of the White/Inyo Mountains provides some of the first high‐precision age controls for the late Pliocene to Pleistocene depositional and tectonic history of the region. Three categories of late Tertiary to recent sedimentary units crop out along the range front: (1) fine‐grained basin fill, (2) uplifted and incised fanglomerates, and (3) recent alluvial‐fan deposits. Seven ash samples collected from six canyons along the range front and from the basal Bishop Tuff in the Owens Valley fall into three age clusters: 0.757 ± 0.004 Ma, 2.08 ± 0.01 Ma, and 2.82 ± 0.02 Ma. The 0.757 Ma sample correlates with the Bishop Tuff and supports other recent Ar/Ar results that date the tuff at ∼0.76 Ma. The 2.82 Ma sample comes from a well‐known ash horizon within the fanglomerate deposits of Black Canyon, which previous workers had correlated with the Bishop Tuff. Because the fanglomerates overlie lacustrine deposits of the Waucoba embayment, the age of the Waucoba lake beds must be at least 2.82 Ma. Using this new age control, we develop a model of Plio‐Pleistocene tectonic events at the western margin of the Basin and Range province. The abrupt change from lacustrine to fanglomerate deposition at ∼3 Ma appears to record the birth of the White Mountains fault. The onset of range‐front faulting was part of a regional tectonic reorientation, approximately coincident with a shift in tilt polarity, from westward to eastward block tilting, of the White/Inyo Mountains and Owens Valley.