RESULTS OF DEEP RESISTIVITY MEASUREMENTS IN SIX PRECAMBRIAN AREAS OF THE WESTERN U. S.

Surface resistivity surveys over extensive outcrops of precambrian igneous and metamorphic rocks were conducted in Oklahoma, Colorado, Wyoming, Montana, and North Dokota. In all areas the resistivities encountered were less than 100,000 ohm-meters, with the possible exception of North Dakota, where the igneous basement may have been masked by 2,000 feet of highly conductive sediments. Except in North Dakota, all the areas were found to be complicated at moderate depth by inhomogeneities or structural features which gave rise to low values of apparent resistivity. In general the surveys reflected lateral variations in geology. Author