Date of Award


Degree Name

Master of Science


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


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.

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Geology Commons