A PRELIMINARY GEOLOGICAL/GEOPHYSICAL INVESTIGATION OF THE COOK CANYON MAGNETIC HIGH, NW UNCOMPAHGRE UPLIFT, COLORADO

In 1979, geometrics performed an aerial magnetic survey in the Moab 1x2 degree Quad (geometrics, 1979). Johnson (1983) found and identified a positive magnetic anomaly, one of the strongest anomalies on the Uncompahgre Plateau, as an intrusion in the Coates Creek-Cook Canyon area west of Glade Park in Western Colorado. The study’s objective is to determine the precise location of that anomaly on the ground using a proton precision magnetometer and GPS units. The study shows the positive magnetic anomaly to have approximately 3300 nT relief. Calculation using Peter’s half slope method indicates the magnetic source is approximately 5,400’ below the surface. Computer calculation using a cylindrical shape with high susceptibility contrast at .04 and a depth of 5,400’ shows the observed and calculated magnetic anomalies are related. This suggests a mafic-type igneous pluton of possible cylindrical shape and with gabbroic composition may be present below the Precambrian surface.