QUATERNARY MAP, ACTIVE FAULTING, TECTONIC GEOMORPHOLOGY, AND UPLIFT RATE OF THE HUMBOLDT RANGE AT THE MARGIN OF THE BASIN AND RANGE AND WALKER LANE PROVINCES

Fault-truncated, uplifted, and abandoned alluvial fans are frequent along the western flank of the active normal fault bounded Humboldt Range. Terrestrial Cosmogenic Nuclide (TCN) surface exposure dating of faulted terrace at Rocky Canyon indicates uplift of the range has averaged about 0.12 mm/yr during the last ~160 ka. A similar uplift rate of less than about .07 mm/yr over the last 35 ka or more years is estimated from offset of a younger terrace at the same site. Values of extension rate across the range are 0.04 - 0.07 mm/yr if it is assumed the rangebounding fault dips at 60°, in general accord with very low values of contemporary geodetic strain reported for the area. Geomorphology at Rocky Canyon records a period leading up to about 160 ka ago that erosion and aggradation of sediment along the rangefront was dominant over fault generated uplift, at which time faulting again became dominant leading to uplift, incision, and preservation of ~160 ka old alluvial terraces here and elsewhere along the rangefront.