ABSTRACT

Simple area-balanced models of a portion of the northeastern Brooks Range illustrate five regional constraints on the gross geometry of a foreland fold and-thrust belt. These factors include (1) the structural topography of the upper surface of the orogenic wedge, (2) the depth to the basal detachment surface at the pin line, (3) the dip of the basal detachment surface, (4) the presence of major ramps in the basal detachment surface, and (5) the depth at which the basal detachment horizon flattens (if it does). Area-balanced models incorporating variations in these factors can be quickly constructed and illustrate a range in the possible regional geometry and tectonic shortening for the fold-and-thrust belt. This method provides a rapid means of evaluating a variety of different geometries of the orogenic wedge before developing a more detailed balanced cross section. In the northeastern Brooks Range, the models alone suggest that the absolute range in possible shortening is from 24 to 69%, corresponding to a total tectonic shortening for the region of 40 to 280 km (24-171 mi).

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