The residual Bouguer anomaly map of the central and northwestern Missoula Valley demonstrates that the configuration of the bedrock in this region is complex. Dense gravity measurements in conjunction with inverse modeling resources allowed for the resolution of subsurface bedrock features less than 300 m². GPS provided sub-meter elevation control making the field data highly accurate.

To isolate the residual Bouguer field from the total field measurements, I evaluated the regional field using gravity anomaly measurements on bedrock extending well beyond the valley edges. I determined the density contrast between the bedrock and valley fill using measurements on representative samples and calculations on the Bouguer density values that minimize correlation between the gravity anomaly and topograph