Abstract Title: Deformation history along the Sierra Nevada -- Basin and Range 
transition zone near Reno, Nevada: the record in Neogene basin deposits

Abstract Author(s):  P.H. Cashman, J.H. Trexler, Jr., T. Muntean, K. Mass, H. 
Park, J. Faulds, J. Louie, G. Oppliger, and A. Ten Brink (University of Nevada, 
Reno)

Abstract: Neogene sedimentary basins record the deformation history along the
Sierra Nevada -- Basin and Range transition zone since mid-Miocene
time, bridging an important gap between contemporary kinematics and the older
geologic record.  We have examined the depositional history and
post-depositional deformation of a series of basins both along and
across the transition zone, near Reno, Nevada. Differences in style and
timing of deformation between the Neogene basins allow us to
distinguish between the tectonic factors that have been active in the
transition zone (e.g., extensional "Basin and Range" faulting
west of the Walker Lane, translation of the Sierra Nevada microplate or
northward propagation of the Walker Lane). Neogene sedimentary rocks
are preserved in west-tilted half-grabens immediately east of the
Sierra Nevada frontal fault system both north and south of Reno; these
record syn- and post-depositional normal faulting.  The best age
control comes from the Gardnerville basin, south of Carson City, where
intra-basin normal faulting occurred >7 Ma, 5 Ma, and approx. 2 Ma, and
the Sierran frontal fault system has been active from >7 Ma to the
present.  In contrast, Neogene basins astride or west of the Sierran
front west of Reno exhibit distributed deformation along NW-striking
dextral, NE-striking sinistral and N-striking oblique-slip faults.
Similar fault sets also occur in the Neogene sedimentary rocks of the
Honey Lake basin, in the Walker Lane north of Reno. Although the Verdi
basin records intra-basin faulting early in the basin history (10.5 or
11 Ma), this  was followed by tectonic quiescence until the basin
deposits were incised, tilted and faulted.  The exhumation event
post-dated fluvial deposits containing horse teeth of Blancan V age,
interpreted by some workers as < 2.6 Ma, and by others as <1.9 Ma (T.
Kelley, pers. comm., 2002).  This kind of kinematic and timing
information from upper crustal structures is an important supplement to
geophysical data when applied to lithosphere-scale tectonic problems.