Date of Award
8-1985
Degree Name
Master of Science
Department
Geological and Environmental Sciences
First Advisor
Dr. Christopher J. Schmidt
Second Advisor
Dr. Gerry Clarkson
Third Advisor
Dr. W. Thomas Straw
Access Setting
Masters Thesis-Open Access
Abstract
Gravity modeling of west-dipping, Laramide mountain flank thrusts which involve Archean metamorphic rocks in the western Tobacco Root and northern Madison Ranges supports the idea that these thrusts are gently dipping.
The thrusts provided a favorable location for normal faulting during Neogene extension. The Neogene faults on the eastern portions of the Madison and Jefferson Basins are interpreted to be listric, and merge with the Laramide thrusts. Basin development occurred along a series of such faults, which dropped hanging wall blocks of the thrust sheets to progressively greater depths. The maximum depth of the Madison basin, near Ennis, was found to be about sea-level.
The depth of the Jefferson Basin is found to change from sea-level near Dry Boulder Canyon, to -3000 feet near Hellroaring Canyon. This change is interpreted to be the result of a northwest-trending fault (northeast side downthrown) crossing the basin.
Recommended Citation
Wigger, Stephen Thomas, "A Gravity Investigation of Mountain Flank Thrusting and Normal Faulting, Madison and Tobacco Root Ranges, Montana" (1985). Masters Theses. 1462.
https://scholarworks.wmich.edu/masters_theses/1462