Gravity measurements in Wyoming and central Colorado



Gravity surveys made by personnel from the University of Wyoming include the Laramie Mountains, the Medicine Bow Mountains, the Hanna Basin, and the South Pass area in Wyoming and the mountainous area west of Aspen in Colorado. These surveys are made with a Worden Master model gravimeter and are tied into gravity base stations established by the U.S. Air Force; almost all the stations are established on surveyed elevations. The purpose of these surveys is largely to study relationships in crystalline rocks.

Detailed gravity surveys on spacing as close as ½ to 1 km have been conducted in the Precambrian core of the Laramie Mountains between 41°00′ to 42°00′N and 105°00′ to 105°4O′W. Rock types covered include Sherman granite, Laramie anorthosite, and related rocks and gneisses. Bouguer anomalies within Precambrian rocks range from −110 mgal over mafic gneisses in the north to −185 mgal over Sherman granite in the south [Hodge, 1966; Woodfill and Smithson, 1968]. Interpretation of these anomalies is being used to study petrogenesis of the anorthosite and structure of the geneisses. Gravity measurements extend out from the Laramie Mountains across a flanking fault into the Denver-Julesberg Basin on the east and west into the Laramie Basin.