Abstract Title: Extent, style and age of extension east of Pyramid Lake

Abstract Author(s): Caroline Whitehill- Joseph Colgan- Trevor Dumitru- 
Elizabeth Miller (Stanford) 

Abstract: We've begun investigations along a ~150km transect to address strain 
accommodation and the magnitude of extension across the Walker Lane Belt-Basin 
and Range-Central Nevada Seismic Belt. At the western end of the transect are a 
series of north-south trending extensional fault blocks (the Lake, Shawave, 
Nightingale, and Selenite Ranges) of Mesozoic granitic rocks unconformably 
overlain by Tertiary volcanic and sedimentary strata. Stratigraphic, 
structural, geochronological and thermochronological investigations of Tertiary 
volcanic and sedimentary sequences provide preliminary constraints on the 
style, timing and amount of extension across these four ranges. Tertiary 
volcanic rocks of the Lake Range are tilted 20¡ to the east and are bound by a 
normal fault. Between the northern Nightingale and southern Selenite Ranges is 
a thick (>1km) section of interbedded pyroclastic ash fall, vesicular basalt, 
flow breccia, and andesite units dipping 33¡ to the southeast, cut by a 
rhyolite dome that probably correlate with the ~13.8-15.0 Ma Pyramid Sequence 
in the Virginia Mtns and Lake Range. They are unconformably overlain by a 
section of gently dipping (8¡) Miocene diatomite, ash fall sediments, and 
debris flows capped by a basaltic layer. West-dipping Tertiary sediments on the 
east side of the Shawave Mtns are tilted ~21¡ by slip on the Granite Springs 
fault, the east dipping range bounding normal fault. Balanced cross sections 
indicate < 25% extension across these four ranges. Preliminary apatite fission 
track dates suggest faulting must be younger than 12 Ma.