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Reconnaissance of the hydrology of sandstone and limestone aquifers along the northwest flank of the Little Rocky Mountains, Fort Belknap Indian Reservation, north-central Montana

Water-Resources Investigations Report 93-4193
By:  and 
https://doi.org/10.3133/wri934193

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Abstract

The geohydrology of aquifers was studied the south- western part of the Fort Belknap Indian Reservation in north-central Montana. The geologic units of interest are the Lodgepole Limestone, principally composed of thin-bedded limestone; the Mission Canyon Limestone, a massive limestone containing numerous solution cavities; the lower part of the Kootenai Formation, composed of sandstone; a sands- stone unit at the base of the Colorado Group; and the Virgelle Sandstone Member at the base of the Eagle Sandstone. These units were formed during Early Mississippian through Late Cretaceous time and have been subjected to uplift, folding, and the intrusion of the igneous core of Little Rocky Mountains. Dips of these units range from nearly vertical to about 10 degrees. Thirty-one test holes were drilled and 25 of the holes were completed as monitoring wells. Water-level fluctuations in most aquifers followed a seasonal pattern with the lowest levels occurring in the fall and winter and highest levels in the spring and summer. Seasonal fluctuations ranged from about 0.6 to 21 feet. Specific capacity of wells tested ranged from 0.02 gallon per minute per foot for a well completed in the Eagle Sandstone to 4.6 gallons per minute per foot for a well completed in the Mission Canyon Limestone. Eight aquifer tests indicated transmissivity values of 15 to 1,000 feet squared per day. Dissolved-solids concentration in water collected from 22 wells ranged from 263 to 1,930 milligrams per liter. The least mineralized water was obtained from the Mission Canyon Limestone and the most mineralized from the Eagle Sandstone.

Suggested Citation

Slagle, S., Christensen, P., 1993, Reconnaissance of the hydrology of sandstone and limestone aquifers along the northwest flank of the Little Rocky Mountains, Fort Belknap Indian Reservation, north-central Montana: U.S. Geological Survey Water-Resources Investigations Report 93-4193, iv, 66 p. :ill., maps ;28 cm., https://doi.org/10.3133/wri934193.

Publication type Report
Publication Subtype USGS Numbered Series
Title Reconnaissance of the hydrology of sandstone and limestone aquifers along the northwest flank of the Little Rocky Mountains, Fort Belknap Indian Reservation, north-central Montana
Series title Water-Resources Investigations Report
Series number 93-4193
DOI 10.3133/wri934193
Year Published 1993
Language ENGLISH
Publisher U.S. Geological Survey ; U.S.G.S. Earth Science Information Center, Open-File Reports Section [distributor],
Description iv, 66 p. :ill., maps ;28 cm.
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