General Features of Pre-Cambrian Structure along the Big Thompson River in Colorado

Abstract

This paper discusses the relations between the pre-Cambrian schists (sedimentary) and the granites and pegmatites with the accessory dike rocks exposed along the eastern flank of the Front Range in the Big Thompson River valley. The Longs Peak granite makes up great stocks and bathyliths intruded into the upwarped and dislocated beds of the Big Thompson schist. The Mpunt Olympus granite intruded the Big Thompson schists and the Longs Peak granite in similar stocks and bathyliths. A wealth of pegmatite dikes transect all of the series. Faults are rare, although of several types. Near the foothills the faults are related to the en échelon folding of the foothill sediments. In the granites they are mostly normal from tension. Around Longs Peak they appear to be low angle overthrusts.