Abstract Title: Space-Time Evolution Extension in the Northern Basin and Range 
Province: Progress and Problems

Abstract Author(s): Miller, Elizabeth L.(Stanford University)-Dumitru, Trevor. 
A. (Stanford University)  

Abstract: Geologic mapping of Tertiary sequences, palinspastic restoration of 
structural cross-sections and apatite fission track dating suggest that the 
modern range-bounding normal faults in the northern Basin and Range province 
accomplished most of their slip (from 3 to >8km) over relatively short time 
periods (several m.y. or less), followed by inactivity, reduced slip rates 
and/or a younger, lesser magnitude episode of slip. Available data suggest the 
ages of main slip events vary systematically across the province. A large 
portion of the central part of the province has faults that experienced a main 
episode of slip 15-17 m.y. ago. The northern and western parts of the N. Basin 
and Range province have faults that slipped between 14-10 Ma, and the edges of 
the province experienced slip on faults at times younger than 10 Ma. As apatite 
fission track dating (blocking T 80-110¡C) is unable to date the youngest 1-2 
km of slip on faults, tehre could be a more recent period of fault slip that is 
coeval across much of the province, generating the seemingly similar geomorphic 
characteristics of basins and ranges acros the province today. This question is 
fundamental to our understanding of the underlying mechanisms and necessary 
conditions for extension of continental crust. For instance, episodic, 
spatially focused faulting may be related to localized heating and rapid strain 
accomodation, while distributed, slow, but coeval strain would argue for a more 
homogeneous heat distribution, crustal thickness and rheology as the province 
evolved. (U-Th)/He dating of apatite is a method with the potential for dating 
the more recent slip on normal fault systems across the province, that can 
perhaps adress this first order question.