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Penrose Conference Announcement

Extensional Reactivation of Thrust Faults, Coseismic Surface Rupture,
and Crustal Evolution in the Eastern Basin and Range Transition Zone

22–27 June 2015 · Evanston, Wyoming, USA
Application deadline: 13 March · Registration deadline: 17 April

CONVENERS (10) applications of geodesy, LiDAR, and INSAR to crustal
deformation and comparison to paleoseismological methods;
Co-Chair Michael W. West, Michael W. West & Associates, Inc., and (11) relation of hydrocarbon occurrence to active, extensional
mwest@m-west-assoc.com tectonism.

Co-Chair Stephen A. Sonnenberg, Colorado School of Mines, The conference area provides an important, largely untapped
ssonnenb@mines.edu field laboratory in which to study the interaction of contemporary
extensional tectonic processes with older structures, reflected in
Paul M. Santi, Colorado School of Mines, psanti@mines.edu modern topography and geomorphology. We suggest that this
part of the eastern Basin and Range transition zone may be a
Tarka Wilcox, Pacific Lutheran University, wilcoxtt@plu.edu “Rosetta” terrane, highlighting tectonic interactions in a complex
geologic setting. Late-onset extension illuminates subsurface
Rare geologic terranes exist in intraplate areas of the North structural relations, reflected in surface deformation, which
American continent that illuminate nascent crustal-scale tectonic would likely not be recognized either in unextended terranes or,
processes, fault nucleation/evolution, interaction of geologic conversely, in highly extended terranes where initial structural
structures in changing stress fields, tectonic effects on topography relations may become indecipherable. Moreover, the juxtaposition
and fluvial systems, and issues in seismic hazard/risk assessment. of active extension against the relatively stable geomorphology of
These terranes, if recognized, are ideally suited to multidisci- the Green River basin provides an opportunity to assess the
plinary research, leading to greater understanding of crustal timing and effects of late-onset extension on landscape develop-
evolution from the crust-mantle interface to surface geomor- ment. We expect that the conference will yield new insights
phology. Conference participants will have the opportunity to related to the region’s crustal evolution with applications transfer-
examine and assess active crustal deformation in an area encom- able to other terranes affected by changing stress fields.
passing the Laramide Uinta Mountains uplift; the Absaroka and Conference participants will be tasked with determining if the
Darby/Hogsback thrust plates of the Sevier orogenic belt project area should be designated as a prototype “national field
(Wyoming and Utah); the late Holocene Bear River fault zone laboratory” to encourage focused research on crustal-scale
(BRFZ); and the transition between the contemporary margin of tectonic processes. A proposal to NSF to support the conference
the Basin and Range province and the adjacent Laramide Green under the EarthScope program is pending.
River Basin. The BRFZ exhibits the largest reported paleo-
GSA TODAY | MARCH/APRIL 2015 displacements in the Basin and Range province, indicating that
the terrane encompassing the BRFZ and extensionally reactivated
thrust faults is among the most tectonically active in the transi-
tion zone.

Specific conference topics include (1) crust/mantle interaction
in the eastern Basin and Range transition zone, 100+ km east of
the Wasatch Front; (2) stress, strain, and rheology at the intersec-
tion of the Uinta Mountains, Sevier thrust belt, Green River Basin,
and active Basin and Range extension; (3) kinematics and evolu-
tion of crustal-scale structures from compression through
contemporary extension; (4) relation of late Holocene co-seismic
fault ruptures to preexisting Sevier and Laramide thrust faults;
(5) refinement of seismogenic fault histories and surface-rupture
parameters; (6) seismogenesis and hazards related to surface
rupture along low-angle faults; (7) tectonic effects on glacial and
fluvial geomorphic systems; (8) glacial loading/unloading effects
on fault surface-rupture; (9) geophysical imaging of structures
from the near subsurface to the crust/mantle interface;

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