GEOLOGIC MAPPING OBSERVATIONS OF THE IONE VALLEY, RAVENSWOOD, REESE RIVER VALLEY, AND WESTERN TOIYABE RANGE FAULTS, BASIN AND RANGE PROVINCE, CENTRAL NEVADA

The Quaternary active Ione Valley, Reese River Valley, Western Toiyabe Range, and Ravenswood faults (IVF, RRVF, WTRF, RWF) comprise a belt of north-northeast striking, range-bounding, dip-slip faults in the Basin and Range province in west-central Nevada. The southern extent of this belt intersects the central Walker Lane in the vicinity of the the Mina Deflection. To the northwest, a parallel belt of historical earthquakes in the Central Nevada Seismic Belt (CNSB) were associated with both normal and dextral displacements indicating that part of the ~8 mm/yr of Pacific/North America relative shear is transferred to the western Basin and Range. Although historical earthquakes have not occurred southeast of or adjacent to the CNSB, tectonic geomorphic features along most ranges indicate active Quaternary deformation. Here we present Quaternary geologic mapping along four major ranges southeast of the CNSB based on evaluation of Google Earth satellite imagery, SRTM 1/3 arc-second imagery, aerial photography, and field reconnaissance. The distribution of old, intermediate, and young alluvial fans as well as the location and relative height of fault scarps are used to assess the pattern of late Quaternary deformation. Preliminary results indicate that the lateral extent of zones of active faulting diminish to the north and south of each range and overlap with adjacent ranges potentially constraining the length of paleo ruptures. Zones of north-east and range parallel fault splays that branch from the range front occur in the southern IVF, central WTRF, and central RWF. The RRVF and WTRF are connected by a zone of fault splays that displace young and intermediate aged alluvial fans and form a structural linkage between adjacent ranges across Reese River Valley. These zones of fault splays may suggest a shift in active deformation trending from north-northeast to north-east. Ongoing efforts at selected sites along each range include assessing slip rates based on (1) quantifying vertical separation across fault scarps and (2) dating of faulted surfaces based on optically stimulated luminescence and soil development. The results have implications towards estimating maximum earthquake rupture lengths and magnitudes and contribute towards a better understanding of strain partitioning in the western Basin and Range.