The integration of gravity and magnetic data is used to aid the determination of the structural configuration along a regional profile in the Idaho-Wyoming thrust belt. The magnetic data can be used for depth estimations of the crystalline basement. At the eastern limit of the thrust belt, the crystalline basement is conformable with the overlying autochthonous sediments. In this area, the magnetic data suggest that basement structures are present beneath the leading thrust sheet and thereby provide an attractive potential for hydrocarbon accumulation. Toward the west, the leading thrust cuts down to the basement so that structures indicated by the magnetic data are essentially of the basal decollement. Seismic data indicate that the allochthonous sediments above the deco lement are essentially concordant with the basement; therefore, structures determined by

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magnetics in this area can also be considered prospective.

A preliminary geologic cross section is constructed using an integration of surface geology, well control, and seismic and magnetic data. Two-dimensional gravity profiles of the geologic cross section are computed and compared with the observed gravity. The interpreted subsurface geology is then modified to improve the match between the calculated gravity and the observed gravity while retaining the constraints imposed by the seismic and magnetic data.

The results of this study illustrate that potential field data can be a useful tool when integrated with available information. Use of these data provides an improved determination of the structural geology in the Idaho-Wyoming thrust belt, and provides attractive leads which ordinarily would be followed by seismic surveys. However, in this particular modeling study, the gravity data do not directly yield prospects, although they do yield an improved interpretation of the structural geology which is compatible with all other available data.

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