A gravity and magnetic survey of the Uinta Mountains

Abstract

The results of a gravity and magnetic survey of the Uinta Mountains and surrounding area are presented and discussed. A relatively high Bouguer anomaly over the core of the range and low anomalies over the flanking basins are caused by low-density sedimentary rock in the basins. A density map and an isopach map of a ‘Tertiary’ section have been constructed from the gravity data, which are in general agreement with known geology. The mean free-air anomaly of +8 mgal shows that the area, including the basins, is in approximate iso-static equilibrium. The mean Bouguer anomaly of −225 mgal corresponds to a mantle depth of 50 km. A large negative magnetic anomaly is associated with the main structure of the range and has been interpreted as having been caused by a batholithic intrusion of low-susceptibility rock, by upwarping of the Curie isotherm requiring a minimum thermal gradient of 27°C km−1, or by a susceptibility decrease caused by tectonic stresses. A positive magnetic anomaly is associated with a fault zone at the east end of the range; it corresponds to high-density rock that is shown by gravity data.