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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 40 (1956)

Issue: 4. (April)

First Page: 791

Last Page: 791

Title: Thrust Belt of Northern Utah, Southwestern Idaho and Western Wyoming: ABSTRACT

Author(s): Armand J. Eardley

Article Type: Meeting abstract


The thrust belt of western Wyoming and adjacent parts of Idaho and Utah is arcuate eastward with the major thrust sheets having been overthrust toward the east. The northern end is crowded against the Teton--Gros Ventre--Wind River tectonic unit and the southern end against the Uinta Mountains mass. The distance between the buttressing elements is 180 miles. One thrust, the Absaroka has been traced the entire length of the belt; others are fairly long, and most have branch faults. The thrust sheets of the forward or eastern part of the belt are stacked in shingle fashion on each other, and for the most part dip fairly steeply at outcrop, although it is evident from stratigraphic displacements that horizontal movement has been considerable in a number of places. The imbric te thrusts of the eastern part of the belt involve mostly Mesozoic strata at the surface. In the back part of the belt is a master thrust called the Bannock, and it involves both Paleozoic and Mesozoic strata. The original view has recently been questioned that it is a great horizontal shallow thrust sheet that was later folded and eroded through in one place. Instead of one master sheet it may be a complex of several imbricate thrusts.

Sharp anticlines and synclines either in front of, or within, the Bannock thrust sheet have attracted the attention of petroleum geologists, and have been drilled without success. A disturbed belt in front of the thrusts involving Cretaceous and early Tertiary strata has been proved productive of oil and gas in several places. Considerable attention is now being given this belt. South of the La Barge oil field the thrust sheets are extensively covered by the lower Eocene Knight formation, and this renders exploration difficult.

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