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Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana

Water-Resources Investigations Report 80-89
Prepared in cooperation with the Montana Bureau of Mines and Geology
By:  and 
https://doi.org/10.3133/wri8089

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Abstract

Temperature-depth profiles of six cased test holes in the Missoula and Bitterroot Valleys, west-central Montana, consist of linear segments, the intersections of which commonly correspond with lithologic boundaries. Geothermal gradients commonly decreased with depth, probably as a result of compaction and higher quartz content of the deeper sedimentary deposits. There is no evidence for hydrothermal discharge. A maximum temperature of 31.7 degrees Celsius was measured at a depth of 869 meters. Estimated temperatures at a depth of 1 kilometer at the drill sites ranged from about 34 to 63 degrees Celsius. Temperatures exceeding 90 degrees Celsius probably would not occur at depths less than 1,500 meters. Values of thermal conductivity needed to maintain an assumed regional heat flow of about 2.1 heat flow units along the measured geothermal gradients generally exceeded published values for the rock and soil penetrated by the wells. Laboratory determinations of the thermal conductivity of cores and cuttings would be useful to refine the estimates and to test the conclusion that the measured temperatures are not hotter than normal. (USGS)

Suggested Citation

Leonard, R., Wood, W.A., 1980, Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana: U.S. Geological Survey Water-Resources Investigations Report 80-89, iv, 15 p., https://doi.org/10.3133/wri8089.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana
Series title Water-Resources Investigations Report
Series number 80-89
DOI 10.3133/wri8089
Year Published 1980
Language English
Publisher U.S. Geological Survey
Description iv, 15 p.
Country United States
State Montana
Additional publication details