Skip to Main Content
Book Chapter

Exploring the western Idaho shear zone using the StraboSpot data system

By
B. Tikoff
B. Tikoff
Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
Search for other works by this author on:
M.J. Kahn
M.J. Kahn
Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
Search for other works by this author on:
R.M. Gaschnig
R.M. Gaschnig
Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell, Lowell, Massachusetts 01852, USA
Search for other works by this author on:
Z.D. Michaels
Z.D. Michaels
Department of Earth Sciences, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, USA
Search for other works by this author on:
K. Davenport
K. Davenport
College of Earth, Ocean, and Atmospheric Sciences, Geology and Geophysics, Oregon State University, Corvallis, Oregon 97331-5503, USA
Search for other works by this author on:
J.A. Hole
J.A. Hole
Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA
Search for other works by this author on:
A.C. Stanciu
A.C. Stanciu
Department of Earth Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA
Search for other works by this author on:
A.K. Fayon
A.K. Fayon
Department of Earth Sciences, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, USA
Search for other works by this author on:
S.C. Kruckenberg
S.C. Kruckenberg
Department of Earth & Environmental Sciences, Boston College, Newton, Massachusetts 02467, USA
Search for other works by this author on:
Published:
January 01, 2017
Publication history
05 August 2017

ABSTRACT

The Salmon River suture zone is the boundary between the accreted (Blue Mountain) terranes and cratonic North America in western Idaho. This region was the focus of study by the EarthScope IDOR (IDaho-ORegon) project that integrated structural geology, geochemistry, geochronology, and seismology. This field trip traverses from western Idaho to eastern Oregon, covering the Atlanta lobe of the Idaho batholith, Blue Mountains terranes, and the middle Cretaceous western Idaho shear zone that separates these two domains. The main component of the Atlanta lobe is the Atlanta peraluminous suite, and it intruded from 83 to 65 Ma, was derived from crustal melting, and lacks a regionally consistent fabric. The crust below the Idaho batholith is relatively thick and seismic velocities are consistent with the entire crust being relatively felsic. The western Idaho shear zone overprints the Salmon River suture zone and obscures most evidence for the suturing. It is the present boundary between Blue Mountains terranes and cratonic North America. From studies along this transect, we have determined that the western Idaho shear zone exhibits dextral transpressional deformation, was active from ca. 103 to 90 Ma, and magmatism occurred during deformation; presently exposed levels on this transect record deformation conditions of 730 °C and 4.3 kbars. There is an ~7 km vertical step in the Moho at or slightly (<20 km) east of the current exposure of the western Idaho shear zone, separating thicker crust to the east from thinner crust to the west. Blue Mountains terranes immediately outboard of the western Idaho shear zone likely were located farther south during the middle Cretaceous and underwent strike-slip displacement during western Idaho shear zone deformation. The Olds Ferry terrane—the accreted terrane located immediately west of the western Idaho shear zone—was underplated by mafic magmatism, likely in the Miocene during eruption of the Columbia River basalt group. The field trip will utilize StraboSpot, a recently developed digital data system for structural geology and tectonics, so participants can investigate the relevant data associated with the IDOR EarthScope project.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

GSA Field Guides

From the Puget Lowland to East of the Cascade Range: Geologic Excursions in the Pacific Northwest

Ralph A. Haugerud
Ralph A. Haugerud
U.S. Geological Survey c/o Department of Earth and Space Sciences University of Washington, Box 351310 Seattle, Washington 98195, USA
Search for other works by this author on:
Harvey M. Kelsey
Harvey M. Kelsey
Geology Department Humboldt State University 1 Harpst Street Arcata, California 95521, USA
Search for other works by this author on:
Geological Society of America
Volume
49
ISBN electronic:
9780813756493
Publication date:
January 01, 2017

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal