Abstract

Gravity and magnetic data were collected in the Mosida Hills, Utah County, Utah, at over 1,100 stations covering an area of approximately 110 square miles to help define the subsurface geology. Standard processing techniques were applied to these data to remove known variations unrelated to the geology of the area. The residual data were used to generate gravity- and magnetic-contour maps, isometric projections, profiles, and subsurface models. Ambiguities in the geological models were reduced by (1) incorporating data from previous geophysical surveys, surface mapping, and acromagnetic data; (2) integrating the gravity and magnetic data from this study, and (3) correlating the modeled cross sections. Gravity highs and coincident magnetic highs delineate mafic lava flows, gravity lows and magnetic highs reflect tuffs, and gravity highs and magnetic lows spatially correlate with carbonates. These correlations help identify the subsurface geology and lead to new insights about the formation of the associated valleys. At least eight new faults (or fault segments) were identified from the gravity data, whereas the magnetic data indicate the existence of at least three concealed and/or poorly-exposed igneous bodies, as well as a large ash-flow tuff. The presence of low-angle faults indicates that folding of downwarping, in addition to faulting, played a role in the formation of the valleys in the Mosida Hills area.