ABSTRACT
The western thrust belt is a narrow (35–125 mi wide) belt of complex thrust faults and folds that stretches from the Canadian border at the north, to Mexico at the south. It forms the middle part of the greater Cordilleran thrust complex which is generally considered to be a single, but geologically variable, tectonic element that extends for nearly 5,000 miles from Alaska to Central America. Exploration for oil and gas in frontier regions such as the thrust belt ordinarily involves mapping the structure, determining thickness and extent of rock outcrops on the surface, and analyzing rock samples for reservoir or source-rock quality, and then comparing these factors to analogous, productive provinces in the region. In 1892, oil seeps of paraffin-base crude were found on the north shore of Kintla Lake in the western Montana salient of the thrust belt in what is Glacier National Park, about 2 miles south of the Canada-United States border.
