A gravity interpretation of the northern Overthrust belt of eastern Idaho and western Wyoming was made to determine the structural configuration of the Precambrian basement and overlying sedimentary veneer. Two east-west gravity models of geologic cross sections were constructed along lat. 42°30^primeN and 43°N and one north-south section was constructed along long. 110°30^primeW. Two-dimensional analysis of the models reveals the presence of two basement highs--one beneath the leading edge of the Prospect fault and one beneath the Absaroka plate. Limited data also suggest another basement uplift may be present beneath the Meade thrust.

The location of the easternmost basement high suggests that it may have formed prior to the completion of thrusting and acted as a buttress to movement along the Prospect, causing the thrust to climb toward the surface. The uplift beneath the Absaroka was probably formed after thrusting, and lifted the overlying Absaroka plate toward the surface, as is evidenced by the exposure of Cambrian, Ordovician, and Devonian sole rocks within the Salt River Range. The uplifts appear to have influenced the subsurface structural geometries of the overlying sedimentary rocks, but not the depositional thicknesses of the Triassic, Jurassic, and Lower Cretaceous units. It may therefore be concluded that the uplifts of the Precambrian basement were formed after the deposition of the overlying sediment ry rocks.

Gravity modeling has also indicated the presence of high-density masses within the Precambrian basement, both beneath the Green River basin at lat. 43°N, and along lat. 42°45^primeN.

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