| 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) |
| Genre: | USGS Numbered Series |
| ProdID: | 28322 |
| Citation Author: | Leonard, Robert B.; Wood, Wayne A. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | iv, 15 p. :ill., 1 map ;26 cm. |
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| Citation Publisher: | U.S. Geological Survey, |
| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 80-89 |
| Citation Search Results Text: | Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana; 1980; WRI; 80-89; Leonard, Robert B.; Wood, Wayne A. |
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| Citation Year: | 1980 |
| Type: | citation/reference |
| Text: | Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana; 1980; WRI; 80-89; Leonard, Robert B.; Wood, Wayne A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Geological Survey, |
