ABSTRACT: Barrier Network Model for Basin and Range Faulting
BARTLEY, JOHN M., University of Utah, Salt Lake City, UT, and WANDA J. TAYLOR, University of Nevada at Las Vegas, Las Vegas, NV
Cross-strike faults in rifts usually are interpreted to be strike-slip faults that accommodate lateral changes in extension geometry and magnitude, but data concerning their development are sparse. It also is unclear if such fault zones typically form during extension or are inherited from earlier events. New mapping along two such zones in the eastern Great basin, the west-striking Blue Ribbon (BRL) and Tempiute (TL) lineaments, shows that faults along the lineaments accommodated mainly normal rather than strike slip faults. BRL faults formed during approximately 31-25 Ma volcanism at vents along the BRL, which thus is a volcanic rift. Brackets on relative ages of TL faults and volcanism are looser, but permit a similar conclusion. Previous work in areas of "normal"north-striking bas n-range structure in southeastern Nevada found normal faulting before and after, but not during, local volcanism. The lineaments, therefore, formed in a tectonic regime differing in both age and kinematics from later basin-range faulting. Postvolcanic basin-range faults terminate, splay, and/or step laterally where they intersect the BRL and TL, suggesting that the lineaments were barriers to later fault propagation. The BRL and TL are preexisting fault zones that interfered with later fault growth and caused, rather than passively accommodated, lateral changes in structural geometry.
In the Tempiute-Mt. Irish area, the TL overprinted at least two Mesozoic thrusts. At least part of the Mt. Irish thrust acted as a propagation barrier to west-striking normal faults of the TL. This relation suggests a general model in which each system of new normal faults interacted with and modified an evolving network of barriers that exerted a major control on rift-zone geometry.
AAPG Search and Discovery Article #91016©1992 AAPG-SEPM-SEG-EMD Pacific Section Meeting, Sacramento, California, April 27-May 1, 1992 (2009)