Date of Award
8-1986
Degree Name
Master of Science
Department
Geological and Environmental Sciences
Department
Geosciences
First Advisor
Dr. Christopher J. Schmidt
Second Advisor
Dr. Ronald B. Chase
Third Advisor
Dr. W. Thomas Straw
Access Setting
Masters Thesis-Open Access
Abstract
The Madison Range is the eastern limb of the Laramide Rocky Mountain foreland Madison-Gravelly Arch. The main segment of the Madison thrust system in the map area is the basement-involved Scarface thrust which dips westward, trends north-northwest, and places Archean rocks onto an overturned footwall of Cambrian through Cretaceous rocks. Foliation of Archean rocks in the footwall is folded with overlying sedimentary rocks.
The Shedhorn Mountain thrust splays from the Scarface thrust. It is exposed north and south of the Shedhorn Mountain anticline, but is blind beneath it. The Taylor fault, an east-dipping back thrust, is inferred to be associated with an upward change in dip of the Shedhorn Mountain thrust from steep (>45 ° ) to gentle (<30°).
The Taylor fault block rotated upward deforming the Scarface footwall and truncating the Scarface thrust.
The presence of the syntectonic Sphinx Mountain conglomerate to the north constrains the timing of most of the thrusting to Upper Maastrichtian (67-70 Ma).
Recommended Citation
Brown, Jeffrey Scott, "A Structural Investigation of a Basement-Involved Thrust System in Southern Sphinx Mountain Quadrangle (Madison Range) Southwestern Montana" (1986). Masters Theses. 4444.
https://scholarworks.wmich.edu/masters_theses/4444
BrownPlateIIAB.tif (232433 kB)
BrownPlateIICD.tif (232160 kB)
BrownPlateIIEF.tif (232879 kB)
Comments
Additional Files are attached.
Geological Map of the (Plate I) West-Central Madison Range Southwestern Montana
Geological Cross Section West-Central Madison Range Plate II, A & B
Geological Cross Section West-Central Madison Range Plate II, C & D
Geological Cross Section West-Central Madison Range Plate II, E & F