Abstract

The major structural elements are of three kinds—folded and belts, broad uplifts, and fairly resistant buttresses. The Colorado plateau and Wyoming basin are the largest resistant elements. Along the western margin of the Wyoming basin lies the Idaho-Wyoming arc of folded and thrust strata. Along the western margin of the Colorado plateau is another north—south-trending group of folds and thrusts. The Colorado plateau and the Wyoming basin are separated by the broad east—west-trending Uinta uplift. A small buttress of recurring positive character in northern Utah lies directly in the path of the southwesterly-trending Idaho-Wyoming arc folds which are deflected around it. The northward-trending folds south of the Uinta uplift veer westward, unite with the Idaho-Wyoming arc folds, and continue in the southwest trend of the arc past the Sheeprock uplift. The Cottonwood uplift crowds the strata into folds and small thrusts against the west end of the Unita uplift and the southeast side of the northern Utah highland.

The evident lack of alignment of the Laramide folds and thrusts with the Basin and Range faults is most striking, and apparently a Laramide control is only local. The foliation of the pre-Cambrian rocks, inherited from pre-Cambrian time, seems to have exerted little influence on the course of the Laramide folds or the Basin and Range faults, although the northern Utah highland as a mass conspicuously deflected the Laramide folds around its margins. The highland did not affect the Basin and Range faults in any discernible way.

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