Year of Award

2007

Document Type

Thesis

Degree Type

Master of Science (MS)

Other Degree Name/Area of Focus

Geology

Department or School/College

Department of Geosciences

Committee Chair

James Sears

Commitee Members

Marc Hendrix, Paul Wilson

Keywords

Horsethief Formation, Montana Thrust Belt, Rocky Mountain Thrust Belt, Sun River Canyon, Triangle Zone, Two Medicine Formation

Abstract

Detailed geologic mapping east of Sun River Canyon in northwest Montana reveals the presence of a triangle zone: a folded, imbricate duplex-structure that forms a wedge at the leading edge of mountain thrust-belts. Triangle zone geometry is well documented in a series of structures that stretch approximately 900 kilometers, from northeast British Columbia into southwest Alberta, Canada. Triangle zones provide the structural traps that contain hydrocarbon (oil and gas) reservoirs in southwest Alberta, but little research has been conducted south of the Canadian-United States border along structural trend into Montana. Relating the structural geometries and stratigraphy of the Sun River Canyon triangle zone to those found in southwest Alberta may lead to new discoveries of hydrocarbon reserves in northwest Montana. Globally, the increased demand for hydrocarbons requires the development of geologically complex sources such as those found in triangle zones. Documenting surface related triangle zone features contributes to understanding the geometry and kinematics of triangle zones and fault propagation in mountain thrust-belts worldwide. The triangle zone east of Sun River Canyon was located through detailed stratigraphic measurements and surface geologic mapping during eight weeks of field research in the summer of 2006. Rock packages of the Upper Cretaceous Montana Group were divided and measured for thickness based on rock type and environment of deposition. Portions of the Split Rock Lake, Split Rock Junction, and Barr Creek United States Geological Survey, 1:24,000 scale quadrangle topographic maps provided a base in which to map the divided rock units. Integrating structural data collected in the field as well as information from historic exploration wells drilled in the area allow for the projection of the surface geology into the subsurface. The cross-section created in this study illustrates the possible location of unexploited structural traps which may contain hydrocarbons.

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© Copyright 2007 Michael David Bradway