Palaeomagnetic Study of Dated Pre-Cambrian Rocks of the Front Range, Colorado-Wyoming

The mean direction of remanent magnetization, after partial a. c. demagnetization, of Pre-Cambrian rocks from the Front Range of Colorado and Wyoming gives a palaeomagnetic pole position at 8°N, 29°E. Rock types sampled include andesite dykes, diorite inclusions in granite, and a highly oxidized red granite, all with a radiogenic age of 1·41 G. Y. This preliminary study suggests there are at least two and probably as many as four field reversals recorded in these rocks, and that remanent directions from andesite dykes may be useful in determining tectonic rotation of the Front Range.