Abstract Title: Geothermal Activity: Another Clue for Unraveling Recent Great 
Basin Tectonics

Abstract Author(s): Coolbaugh, Mark F. (University of Nevada, Reno) Ð Faulds, 
James E. (University of Nevada, Reno) Ð Blewitt, Geoffrey (University of 
Nevada, Reno) Ð Henry, Christopher D. (University of Nevada, Reno)  

Abstract: Regional northwest-trending zones of high geothermal fluid 
temperatures, sub-parallel to the Walker Lane, cut a north-northeast-striking 
fabric of Quaternary faults that otherwise control geothermal fluid flow in 
much of the Great Basin. This apparent dichotomy, most prominently displayed in 
west-central Nevada marginal to the Walker Lane, can be explained if dextral 
slip along the Walker Lane is partitioned into north-northeast-striking normal 
faults in the Great Basin interior. The distribution of geothermal fields 
suggests this partitioning occurs over a strike length of hundreds of 
kilometers (both along the Walker Lane and Humboldt Structural Zone). Thus, 
tectonic activity related to San Andreas plate boundary motion may extend far 
into the Great Basin interior. In portions of the Great Basin, including Dixie 
Valley, geothermal faults roughly parallel range-front margins, suggesting a 
relatively uniform extension direction over space and time. In contrast, south 
of Winnemucca, northeast-striking geothermal structures intersect 
north-northwest-striking range-front faults at distinct angles, suggesting 
either an evolution to more northwesterly-directed extension with time, or a 
re-partitioning of some extensional strain into northwest-striking dextral 
faults. An en echelon pattern of N20-30W and N30-40E-striking faults controls 
geothermal activity in the northwestern Great Basin, including the Black Rock 
and Alvord desert areas. This bimodal pattern defines a possible shear couple 
with nearly east-west extension and north-south compression, as would be 
expected in a zone of northwest-trending dextral shear.