Montana Bureau of Mines and Geology Montana Ground-Water Assessment Atlas No. 2, Part B, Map 7 A Department of Montana Tech of The University of Montana December 2004 Altitude of and Depth to the Bedrock Surface: 24 W 23 W 22 W 21 W 20 W 19 W 114o o Flathead Lake Area, Flathead and Lake Counties, 3 48 30 20 2700 3100
0 3 0 3300 0 0
8 3 2 0
2 00 0 29 3 0 32 N 0 0 0 2900 0 350 3600 0 Montana 2 7 ? 0 0 0 0 3 3500 3200 3 0 3 7 0
0 3 2
0 3 2 5
80 0 0 0 by 2 0 8 00 3 0 3 4 3 0
0 3
0 6
1
3000 3 0 0
5 0 0 0
0 3 3 6 3
2900 0 Larry N. Smith
0 0 0 3000 2 3400 7 0 0 3200
31 N ? 1 Authors Note: This map is part of the Montana Bureau of Mines commonly greater than the nearby topographic relief (Fields and 3000 0 0 400 2800 ? 0 0 2 3100 3 90 3 200 and Geology (MBMG) Ground-Water Assessment Atlas for the others, 1985). 0 Flathead Lake Area ground-water characterization. It is intended to Fault boundaries between basins and uplifted mountain ranges ? 3200 300 0 2 2900 400 0 50 stand alone and describe a single hydrogeologic aspect of the study have not been mapped in detail on published surficial geologic maps, 9 00 0 2 5 2 2 00 2800 1000 0 2700 Whitefish 15 3000 area, although many of the areas hydrogeologic features are except for part of the Mission Fault on the southeastern side of the 00 3000 ? 3 1500 interrelated. For an integrated view of the hydrogeology of the Mission valley (Ostenaa and others, 1990, 1995). Inferred locations 1 0 0 200 3100 Flathead Lake Area the reader is referred to Part A (descriptive of basin-bounding faults in the area (fig. 6) were drawn based on 3100 2
32 2 2 9 overview) and Part B (maps) of the Montana Ground-Water Assessment trends in the structure contours on the bedrock surface and, in part,
2 1 0 3 0 7 8 0 0 8
0 5 0 0 0 3100 2 0 0 0 0 90 0 0 0 0 1 3200 Atlas No. 2. on published maps of Mudge and others (1982) and Harrison and
3 2800 0
1 0
0 0 3 3300
1
0 Columbia Falls 0 others (1986, 1992). The bedrock surface shows N-S- and NW-SE- 3000 3 0 00 0 0 0 4 3 INTRODUCTION trending, structurally controlled basins in the Swan, Flathead, Mission, 0 4 2000 0
3 3 0
1 Hungry Horse
0 0
0 3
2 2
2 0 0 7
2 Jocko, and Little Bitterroot valleys and the Irving Flats and Camas 6 0 0 0
0 0 0 0 2 0 0 9 0 5 2 The main map (fig. 1) shows the altitude above sea level of Prairie Basin areas (fig. 4). 0 0 0 0
0 0 3 the Belt Supergroup bedrock surface beneath unconsolidated surficial
3 1000 1 3100 0 0 sediments (sand, gravel, silt, and clay) and partly consolidated Tertiary 0 0 2600 1 30 N 3 sedimentary rocks. The contours on the bedrock surface show the
3 2 2 8 position of the unconformity on the Belt rocks (the geologic structure) 0 3 0 0 1 0
0 2 0 7 2 2 8 0 and, in places, the erosional shape of the valleys at depth (the 3 0 0 0 0 0 0 2900 0 0 paleogeography). These features offer clues to help unravel the geologic history. The smaller maps of the Kalispell and Mission
2 7 0 3 valley areas (figs. 2 and 3) show the estimated depth below the ground 0 2 0 1 0 5
0
0 surface one would have to drill to encounter the same bedrock surface 3 0 0 2
2 5
3 5
0 0 6 00 2
5 0
37 0 00 0 2 beneath these valleys. The depth to the bedrock surface outside of
0 3
9 1
0 0 0
0 0 0 0 1 0 0 3 0 0 areas in figures 2 and 3 can be calculated by subtracting a value Explanation 3 9 2600 2
3 2600 1 2 0 3 0 0 derived from the map from the land-surface altitude. 0 0 0 0 Fault, dashed where 3 2 2 1500 Development of ground-water resources in fractured bedrock 0 0 6 0 0 inferred; ball and bar on 00 0 30 aquifers has increased during the 1990's as land around the perimeters downthrown side 200
30 2 0 7 0 8 0 of valleys has been subdivided. These maps are intended to help
0 0
2 200
0 0 7 3000
0 estimate the altitude of, or depth to, bedrock in areas where wells Troughs in bedrock; 0 3300 3 400 dashed where 5 00 3 1500 have not yet been drilled and aid in planning new subdivisions or 3 1 discontinuous; arrow 0 0 other developments relying on ground water. 32 29 N 0 0 indicates inferred flow 0 900 90 2 These maps are useful for estimating drilling depths and at what direction
0 3200 0
5 1 levels to complete water wells. In areas where bedrock is present at 2 5 0 0 0 0 0 shallow depths there likely will be a lack of sand and gravel aquifer Outcrop of pre-Tertiary 3 2 7 0 2 rocks, predominantly 0 9 materials and wells must be completed in fractured bedrock. Because 3100 0 0 Proterozoic Belt 2 3600 3300 8 wells typically produce less water from fractured bedrock, than from 700 0 3 3500 0 8 0 Supergroup units
3600 0 alluvium, development of large-capacity wells is typically precluded
3 3 2 7 3 0 8 0
0 9 4
0 0
0 0 1
0
0 0 where bedrock is at shallow depths. The depth of the bedrock surface 0
3 3700 5 beneath confining units, such as till or silt and clay, is important to Mission Fault 0 3400 0 260 know in areas where new wells are being installed because in some 3600 0
2 3 5 6 3 places bedrock is the only available aquifer. 0 0 0 3 0 0 00 0 3 1 39 4 Bedrock units exposed around and presumably present beneath 2300 1 0 0 5 5 1000 0 2400 0 0 370 0 0 0 0 2500 Kalispell0 the valleys belong to the Belt Supergroup (Johns, 1970; Harrison and 3900 1500 2700 others, 1986, 1992). Ground water in Belt Supergroup rocks is 800 3 2
3 3 3
9 3 3600 10 0 0 generally produced from fractures; unfractured rock typically is not 0 0
7 0 0 0 3000 0 2 400 0 34 3 0 0 2 2 very permeable to water. Tertiary sedimentary rocks are not represented 6 0 0 0 0 0 0 0 28 N 0 3 1 0 1 2 3 1500 on these maps, but overlie Belt Supergroup bedrock and are apparently 0
3 0 0 2900
3 3000
8 3 0 3 0
0 7 8 50 0
0 3 0 3 locally extensive in the subsurface. They are exposed at the surface 0 6 8 3100 0 0 2 0 0 1500
32 0 0 0 0 0 5 3 8 0 0 2500 1000 1 north of Hungry Horse; west-northwest of Whitefish, in the upper
3 3 3300 5 1 3 0
3900 0 2 0 1000 3300 2 5
3 0 0
3 3500 9 0
3 50 32 5 0 ends of valleys within the Salish Mountains, south of Big Draw; and
7 3
0 0 0 0
3 4 0 0 0 0 2000 0 0
6 0 0 0 900
3 0 2000
0 3 3 3600 700 in the Jocko Valley (fig. 4; Smith, 2002; Smith and others, 2000).
8
0 0 9 0 0
0 0 0 0 4 9 200 3 3 2 27 Marginal quantities of ground water are produced from local, thin,
9 2 0 0
0 3 3 00 9 0 800 0 8 0
00 7 2 3500 2 0 600 0 3 4 2 0 0 60 sandy and gravelly beds in the Tertiary rocks.
0 0 0
0 3 400
3 6
6 3 7 00 0 50 0 30 2300 2 2 Figure 6. Location of known (Ostenaa and others, 1990, 1995) and 0 0 0 500
0 6 0 0 3 0 2 0 8 2200 2500 1 inferred basin-marginal faults (black), and approximate traces of 00 5 3200 2 0 300 Whitefish Range
0 3200 70 0 3 0 Whitefish Lake Teakettle 0 0 0 trough-shaped scours in bedrock (blue). 7 0 2 0 3 9 0 5 2
3 0 Mountain
0 0 7 2 2 3900 5 2100 0 0 2
3 3 0 8
3900 3600 0 3 0 3 0
8 00 2 0 0 0 0 3 0 34 3100 2 2 Badrock Canyon 0 0 0 3800 3400 0 2900 6 5 3300 0 3 0 2 0 0 9 0 Whitefish Columbia 0 0 Stillwater River valley
0 0 3900 3 Extent of Tertiary Rocks 34 2400 7 Stillwater River valley 3 00 6 2 Falls 3900 2 Hungry Horse 6 1500 00 0 0 0 3 0 0 3000 5 0 2700 0 0 3200 3400 3 0 2300 0 3 00 80 2600 0 35 0 0 Salish Mountains Swan 3 32 0 15 0 00 3 00 3 7 0 1 8 0 3 0 3 3 0 60 Basin-filling sedimentary rocks above Belt Supergroup rocks 8 0 2 2 0 0 2 0 0 8 3 0 0 7 3100 7 0 0 0 27 N 3900 3 2 include a section of clay-rich lower-to-middle Tertiary rocks and 0 3800 7 Kalispell valley 3 3100 0 300 0 3500 0 0 (upper Flathead 350 3 3 more poorly understood middle-to-upper Tertiary sedimentary rocks 0 3 0 0
3 330 2000
8 3400 0 3 0 0 River valley)
0 0 4 3400 0 0 0 0 3 that accumulated in various tectonic basins. The lower-to-middle 3900 0 0 5 3 3700 Bigfork 3600 2900 1 Range 0 3800 0 2 5 0 3600 2800 7 0 Tertiary Kishenehn Formation crops out north and southeast of the 6 3900 0 0 3 3 5 0 0 Kalispell 800 3 2
3900 50 2 0 2 30 town of Hungry Horse and along the incised Flathead River valley
2 8 0 0 6 0 0 0 0 6
0 1 0 0 2 3 3 0 5 3 Figure 2. Contour map of the depth to bedrock in the Kalispell valley. The depth-to- (Constenius, 1981, 1988). Partially consolidated siltstone, carbonaceous 3 2 0 1 0 0 0 3 6 0 0 1 0 0 7 0 8 3 0 0 21 /2 W 2000 bedrock map reflects the altitude of the bedrock surface map north of Flathead Lake shale, sandstone, and conglomerate also occur in the subsurface 00 0 3700 2800 Swan River
9 3400 2 3400
0 Smith 3 8
0 0
0
0 9 3700 2 between Teakettle Mountain and Whitefish Lake and near Swan
0 0 because of the low surficial relief in the valley. Bigfork 3 9 0 3 Valley
8 3 2 0 valley 3 3
8 0 9 0
0 Lake, and are likely equivalent to the rocks of the Kishenehn Formation. 0 0 3000 0 0 0 38 0 3400 5 These rocks are only noted in water-well logs and in the Stoltz Lumber 3 Flathead Lake 2 3200 Salish Mountains Swan Lake 7
0 3900 0 2600 3 50 2 0 2 0 #1 exploratory well and are not known to be exposed at land surface. 7 0 5 2 0 0 6 0 5 3 0 0 0 2 0 3300 5 3100 6 0 2 3800 2 0 Tertiary rocks generally produce less than 5 gpm of water to wells.
2 3 0
3700 5 00 0 8 0 0 3 3100 0 Rocks of suspected or known early-to-middle Tertiary age occur 00 Mission Range 200 27 2 3900 3600 3 3 40 Sullivan Flats 3 2900 0 2300 3800 0 3000 at the surface and at depth in the southern half of the map area (Smith 0 2 6 o 0 2 2900 0 3 48 0 and others, 2000), but were mostly included with Quaternary surficial 2400 0
0 0 deposits on published maps (Harrison and others, 1986; Ostenaa and 26 N 7 Big Draw 3 2400 2 Big Arm 2 2 2200 8 600 4
00 0 others, 1990). For example, in Irving Flats and Camas Prairie Basin, 0
o 3
1 48 0 Little
26 0 consolidated siltstone, clayey sandstone, and clayey conglomerate 2500 00 Explanation Irvine Flats are found below unconsolidated sediment but above fractured Belt 2 2 1 0 0 5 0 0 0 Supergroup rock, and are similar to Tertiary rocks described in the 5 0 0
2 2
0 Bitterroot River Polson 0 3
5
0 0
7 2
9 0 0 2 2 2 0 0 northern Little Bitterroot River valley (Harrison and others, 1986; 5 0 2 0 0 0 Lange and Zehner, 1992). Wells completed in Tertiary rocks, like 2
2
0 2 8 Water-well location 0 2 0 Mission those in Irving Flats and Camas Prairie Basin, are typically reported 7 0 0 0 2 valley 6 valley to produce less than 5 gpm but a few yields are reported to be as
0
0
3
3 Ronan 2 Oil and gas well location
6 0 much as 20-75 gpm. Due to incomplete geologic mapping of Tertiary
0 0 0
2 rocks, few well penetrations to bedrock, and reliance on geophysical 2 1 6 2 0 3000 5 0 00 2 Contour (feet) 0 7
0 0 Camas data, the top of Belt Supergroup bedrock was mapped with dashed 0 Prairie (approximate) contours throughout the southern half of the map area.
0 2 0 3000 8 Contour, approximate (feet) Basin 2 0 1 3 The accumulation of greater than 3,000 ft of sediments and 0 9
0 2300 0 3000 sedimentary rocks beneath the Kalispell valley and Swan River valley 2 2000
3 7 2
0 0
2 Contour, estimated from geophysical 0
0 0
0 6
0 suggests that at least part of the basins sedimentary fill was deposited
0 1 2
3 3000
25 N 0 8 2
1 0 2
6 data (feet) 0 0 9
0 0 0 during late Tertiary uplift of mountain ranges and subsidence of 2
0 3 0 1 1 0 0 0 0 basins (Constenius, 1996). Relatively thin fill above Belt Supergroup 3 0 0 0 3 0 Contour, very approximate, in areas
0 1 1 0 30 bedrock in the Mission valley and other valleys in the southern half 0 0 3 2 3000 0 0 0 2 3 0 2 8 between other studies (feet) Jocko Valley 0 of the map area, suggests that Tertiary sediments either were not 0 0 0 2
0 0 4 0
2 9 0 0
9 2
0 0 3 0 3 deposited to thicknesses much greater than about 1,000 ft or were 0 0 1 25 9 Outcrop area of pre-Tertiary rocks, Arlee 3200 0 0 eroded at later times.
1
7
0 2200 predominantly Proterozoic Belt 0
2 2 5 Supergroup units 9 2700 00 0 Localized Erosional Features on the Bedrock Surface 0
2
6 0 2 0 6
0 5 2 0 0
0 2
0 8 2 2 3300 Quaternary and some Tertiary units 8
0 0 7
2
0
0 Scoop-shaped trough features are locally mappable on the bedrock 9 0
2 0
3
0
0 0 0 0 2 surface and have either continuous or discontinuous longitudinal 9 2 2 0 3
0 0 0 10 Principal streams and water bodies 0
9 2 500 0
0
2 profiles (fig. 6). Continuous troughs, like that beneath Smith Valley 0
27 8 2 0 4 0
0 2
0 00
2 0
3 2800 2600 3200 3100 4 Figure 4. Location map of geographical features and its tributaries, are minor valley systems that have integrated, 2 3000 1800 2 Township boundary 600 2900 2800 2900 concave-up longitudinal profiles. Discontinuous troughs, like those 00 22 5 00 00 2 27 2800 beneath the Stillwater River valley, Sullivan Flats, and Flathead Lake, 2700 1900 24 N 2900 29 2800 2 00 00 2300 City 00 5 27 26 DATA SOURCES are minor valley systems that have non-integrated, concave-up and 0 0 2600 2800 2600 27 00 concave-down longitudinal profiles. 700 00 2800 2 24 2 3100 2900 0 0 29 70 2800 0 2900 0 2 3 00 3300 0 00 0 2 Of the nearly 15,000 water wells in the area, about 9,700 had The continuous troughs beneath the Smith Valley are associated 3000 0 30 1 3 2600 5 0 3 0 2600 2 0 0 100 3400 00 700 3 0 2800 interpretable drillers logs; 2,950 of them indicated that the wells with terminal moraines, striated bedrock surfaces, and glacial deposits 2800 00 2500 2 32 9 2 3 0
0 8 3
0 0
0 0 drilled into bedrock, their locations are shown on the map. In areas (Alden, 1953). These glacial features indicate a pre-existing alluvial
0 2 2 0
0 7 2 0 0 3 0 5 2 1
1 0 8 0 0 0 2800 0 0
0 0 2800 0 where well logs were scarce or not present, geophysical data were valley system was glacially scoured to produce the trough-shaped 0 2
2 2
8 9 6 8 2
0 0 0
0 0 0 0 0 0 2 0 used to interpret depth to bedrock. Logs from wells that did not bedrock valleys. The Big Draw valley east of Sullivan Flats to the 0 9 3
0 2 6
2 penetrate bedrock also provided minimum values for depth to bedrock Big Arm of Flathead Lake may also be a continuous trough, but
3
2 0
3 9
0 0 0 0
0 0 5 0
9 0
0 7 2
0 2 2 2 0 in areas where contouring was based primarily on geophysical data. subsurface data are insufficient to accurately map the valleys
0 2 3 0
3 0 4
3 0 5 0 0
2
3200 3400
3 Land-surface altitudes were used to calculate the altitudes of the longitudinal profile. 2 3
70 4 0 3 32 0 00 0 0 bedrock surface from the depth-to data. Discontinuous troughs are mostly 0.5-2 mi wide, 4-16 mi long, 0
2800 2 3400
0
3
5 0 2700
0 1
7 2400 0 0 Logs of drill cuttings from one well drilled for oil and gas sinuous in plan, and undulatory in longitudinal profile. The troughs
2 0
2 2900 3 2600
0 0 exploration in the northern part of the map area (Stoltz Lumber #1, along the Stillwater River valley are apparent from well-log data and
0 0
6
2 2 00 T. 31 N. R. 21 W., sec. 26) were used to determine the lithology and are similar in size to troughs cut in glacial till and the deep alluvium 1 4 0 3
0 3 3
2800 3
2 3 3400 0
2700 0
0 3300 0
3 depth of both the Tertiary sedimentary units and Belt Supergroup unit south of Columbia Falls (cf. Konizeski and others, 1968). The
0
0 0 3 2 0 0 0
9 3200 9 0 0 0 0
2 0 260 0 7 0 28 1 0 0 2 3000 0 23 N 2 bedrock. Estimates of the thicknesses of unconsolidated or weakly discontinuous troughs in bedrock beneath Flathead Lake are coincident 2200 0 2 3100 290 Figure 3. Contour map of the depth to bedrock south of Flathead Lake in the Mission 7 0 9 0 240 0 2 00
29 00 and Jocko valley areas. The greatest depths in the area occur just south of Flathead consolidated strata above bedrock were made along cross sections with infilled troughs cut in unconsolidated sediment above the bedrock
3 4
0 3400 from gravity surveys by Konizeski and others (1968), LaPoint (1971), and with bathymetric lows in the lake bed (Kogan, 1980; Wold, 0
0 2 2 3 0 3 Lake at a structural depression southeast of the city of Polson.
4 7
0 0
6 0 0 0
0 2 2 0 0 2
8 Stickney (1980), and Boettcher (1982); seismic refraction profiles 1982). The discontinuous troughs beneath Flathead Lake have been 5
8 0 2 0 0 0 0
0 2900 3 26 26 2 21 W20 W 19 W by Briar (1987) and Slagle (1988); and a seismic reflection survey interpreted to be possible fault-line scarps (Kogan, 1980; Wold, 1982), 00 0
2 0 2600 0 8 0
2 0 of Flathead Lake by Wold (1982) (fig. 5). Geophysical surveys were although no evidence for offset of seismic reflectors could be found
0 2
3 6 9 3 2 2 2 0
0 0 7 0 5
0 0 0 0
3 0 0
0 0
0 1 unable to image bedrock at the north and south ends of Flathead along the features (Kogan, 1980). Aquifer materials in the bottoms
0 0 0 0
Polson 2 Polson
7 9 0 0
9
2 0 5 2
0 3 Lake, so contours in those areas are only inferred. Because of the of separate, aligned troughs in the Sullivan Flats area were shown to 3 7 00 2 0 4 1 0 2 3 5 0 0 0 0 2300 2 0 0 2 0 8 2 2900 2 0 7
2700 0 0
8 6 0
2500 0 scant well-log data and the lack of geophysical data in the areas not be in hydrologic communication (Briar, 1987). Briar (1987) 0 0 0 2200 0 0 0
3000 0 6 2400 0 8 0 0 0 1
0 0 5 2 0 2 0 0 0 upriver from Badrock Canyon and between Columbia Falls and suggested the depressions may have formed during multiple advances
4 9 0
0 2 3 2 2 0 2900
0 1
0 2 7 0 2800 9 0 2 000 2800 300
0 0 3 2900 0 0 Whitefish, the altitude of the bedrock surface in these areas is mostly of a glacier that extended beyond the furthest recognized terminal
0 0 2 2300
0 1 0 0 2
0 0
3 0 7 0
0 2 3 0 3 2800 2 26 2 0 3 unknown. moraine in the Big Draw valley. 0 9 0
2 0 0 0 0 0 2400 8 0 8
2 0 2500 2 0 2600 1 Water-well driller logs and well locations are stored in the Ground- An alternate interpretation of the origin of the discontinuous 7 0 2
2800 2 0
2 2
2 2400 0 3
3 2500 9
0
2 1 Water Information Center database at Montana Bureau of Mines and troughs in the area is that they are subglacial tunnel-valleys (e.g. Ó
0 0 9 0 1 0
0 9 0 0 0 7 2 0 0 2 0 0 300 2400 22 N 2 2500 0 Geology. Logs and interpreted tops from the Stoltz Lumber #1 well Cofaigh, 1996; Benn and Evans, 1998, p. 332). The sinuous planform, 0 8 0 0 2 3 0 0 9 00 2600 2 3 0 5 0 2 2 2 0 are in the files of the Montana Board of Oil and Gas Conservation undulatory longitudinal profiles, thin accumulations of sand and
22 N 0 8
2 2 2500 0 0 0
0 9
0 2 0 0 2 9 0 0 0
0 0 9 2700 0 2 0 700 0 0 2 0 7 in Billings, Montana. Ground-surface topographic data are from the gravel at the trough bases, heterolithic sediment fills, and lack of 3000 0 3
26 2800 0 0 2 0
2200 3 6 6
0 2 0 0 0
0 1:24,000-scale U.S. Geological Survey Digital Elevation Models evidence for tectonic offset of the infilling material suggest that the 0 2 6 0 00 4 2 2 25 0 0 4 6 0 0 0
0 0
4 2400 0 (DEMs) for western Montana. The outcrop areas of the Belt Supergroup troughs are erosional scours. The fact that longitudinal profiles of
0 3 2 9 2 1 0 1 8 1
2 0 1 0
00 0 0 0
0 0 8 0
2 0 were modified from digital versions of geologic maps (Mudge and the discontinuous troughs are undulatory suggests that erosion took
2700 0
0 2 3
2 6 3
2 0 0 0 2 others, 1982; Harrison and others, 1986, 1992; Smith, 2002). place by vigorous channelized meltwater flow that was hydrostatically 3000 2200 20 0 0 0 00 0 8 0 1 2 3 pressurized beneath the Flathead Lobe of the Cordilleran ice sheet.
0
2600 0 3100 2800 2 8
2800 2 2600
2 2 2900
3 2300 0 0 2300 1 3
0 0 0 0 ACKNOWLEDGEMENTS
0 2900 3 7 0 2 0 0 0 0 5 2 2700
0 2 24 2 9 0 00 6 This work was supported by the Ground-Water Characterization 0 2
0 2 2 8 0 3200 4 0 4 3 0 2 0 2300 0 0 3 2600 0 0 28 0 Program at the Montana Bureau of Mines and Geology. Don Mason 00 2800 0 (1) 0 29 2700 0 00 27 2600 and Cam Carstarphan assisted in the interpretation of drillers logs. 2800 0 2500 0 1 290 3 0 2 2 The map and text was improved due to reviews by Thomas Patton, 2800 9 5
0 0 2700 0 0 2900 21 N 2 Wayne Van Voast, and Edmond Deal. 2200 2
0
0 0 0
0 0
0 0
9 4 0 2
2 800 2 0 21 N 2 8 2 (2) 2 REFERENCES 5 0 0
0 0 2 5 0
2400 2 9 2 0 6 0 0 8 0 2 0
0 0 2900 2 0 Alden, W. C., 1953, Physiography and glacial geology of western 7 7 00 0 2 1 0 0 0 0 0 0 2 Montana and adjacent areas: U.S. Geological Survey 7 6 0 2 2400 0 2 2 0 2 8 290 0 30 0 0 290 00 Professional Paper 231, 200 p. 0 2900 0 7 Ronan Ronan
2 Benn, D. I., and Evans, D. J. A., 1998, Glaciers and glaciation:
2
3 0 7 (6)
0 0 0 London, England, Arnold, 734 p. 0 0 28 0 0 0 2600 1 2900 3 00 3 0 9 2 2 2 0 Boettcher, A. J., 1982, Groundwater resources in the central part of 6 0 0 3 0
0 0 2
0 0 7 (5) the Flathead Indian Reservation: Montana Bureau of Mines 2 0 0 0 2 3 0 0 90 2500 2 0 o 0 and Geology (in cooperation with the U.S. Geological Survey) 0 3 2 8 0 4 1 47 30 2 2 2 0 4 0 0
2900 6 0 0 0 7 0 80 0 0 Memoir 48, 28 p. 2 270 2 3 2 0 0 6 0 (4) 2 2 0 0 0 2800 0 0 0 2700 3 2 1 2 0 Briar, D. W., 1987, Water resource analysis of the Sullivan Flats area 2 6
3 3
2 2 0 5 8 00 2300 0 2 0 9 0
0 6 0 0 4 0
0 0 0 o 0 0 near Niarada, Flathead Indian Reservation, Montana [M.S. 0 47 30 2700 0 0
8 2
2 0 2 8
2 9 0
4 0 20 N 5 0 thesis]: Missoula, Montana, University of Montana, 184 p. 2 0
2500 2300 0 0 0 00 200 0 5 2600 3 0 2 0 2800 3 2 Constenius, K. N., 1981, Stratigraphy, sedimentation, and tectonic
0 0 2 2700 0
6 0 8 0 20 N 2400 2 4 0 0 0 0 2 0 0 0 history of the Kishenehn basin, northwestern Montana: [unpubl. 0 5 (3) 6 7 2 2 2 2 0 M. S. thesis], Laramie, University of Wyoming, 116 p. 4 30 2500 0 2 0
0 3 0
2
2 3 2200 0 Constenius, K. N., 1988, Structural configuration of the Kishenehn 3100 2 2300 0 0 0 0 2500 0 24 Basin delineated by geophysical methods, northwestern 0 2
6 9 00
2 0
0 0 2 0 Montana and southeastern British Columbia: Mountain 2 3
1 9 0 2
3 2700 8
0 0 2
3 0
0 7
1
2 0 2600
0 Geologist, v. 25, n. 1, p. 13-28.
9
0 0
0 2 0
0 8 00
2 Constenius, K. N., 1996, Late Paleogene extensional collapse of the
1
6 2
0 0
0 0 0
2 0 Cordilleran foreland fold and thrust belt: Geological Society 2 90 9 0 3000 2400 0 0 2 of America Bulletin, v. 108, p. 20-39. 3 6 0 0 0 0 0 0 0 4 0 0 2 3 2500 Fields, R. W., Rasmussen, D. L. Tabrum, A. R., and Nichols, R., 0 2 2 8 2 7 2 0 3100 0 0 9 0 0 0 0 0 3 2
0 0 3 1985, Cenozoic rocks of the intermontane basins of western
6 4 2 0 5
2 0 0
2800 0 Montana and eastern Idaho: A summary, in Flores, R. M., and
0 2 0 6
2500 0
5
2 2 2 0 Kaplan, S. S., eds., Cenozoic paleogeography of west-central 3 6 2 0 2 0 7 0 0 4 0 0 0 0 19 N United States: Denver, Rocky Mountain Section Society of 27 00 Economic Paleontologists and Mineralogists, p. 936. 2 200 4 0 19 N 0 0 3 Harrison, J. E., Cressman, E. R., and Whipple, J. W., 1992, Geologic 0 2 3 0 0 0 Figure 5. Index to previous studies involving acquisition of geophysical and structure maps of the Kalispell 1 x 2-degree quadrangle, 300 data: (1) Konizeski and others (1968), (2) Stickney (1980), (3) Montana, and Alberta and British Columbia: U.S. Geological Boettcher (1982) and Slagle (1988), (4) LaPoint (1971), (5) Briar Survey Miscellaneous Investigations Series Map I-2267, scale 300 2 9 (1987), and (6) Wold (1982). 1:250,000. 0
2600 0 0 0
2300 5 2 2 Harrison, J. E., Griggs, A. B., and Wells, J. D., 1986, Geologic and 5 2700 00 0 24 0 MAP CONSTRUCTION structure maps of the Wallace 1 x 2-degree quadrangle,
0
0 2700 4 2 Montana and Idaho: U.S. Geological Survey Miscellaneous 8 2
0
0 2 2800 The altitude of the bedrock surface (fig. 1) was made first by Investigations Series Map I-1509, scale 1:250,000. 3 0 9 0 0 00 0 0 5 3200 2 2600 4 standard subsurface-mapping procedures. Because of the imprecise Johns, W. M., 1970, Geology and mineral deposits of Lincoln and 0
2 0
7
0 0 nature of drillers log data, contours were drawn only where multiple Flathead Counties, Montana: Montana Bureau of Mines and
2900 0 0
2 3 data points supported the contour location. The locations of a few Geology Bulletin 79, 182 p. 3
3600 0 hundred wells were changed by comparison of anomalous geologic Kogan, J., 1980, A seismic sub-bottom profiling study of recent
2
0 3
3 3
0 3 0 4
0 0 0
0 descriptions with street addresses of the well location; some well sedimentation in Flathead Lake, Montana [M.S. thesis]:
0 18 N 3 1
2900 0 locations were confirmed by talking to the well owners. Depth-to- Missoula, Montana, University of Montana, 98 p. 0 100 18 N 2800 bedrock estimates derived from well-log and geophysical data were Konizeski, R. L., Brietkrietz, A., and McMurtrey, R. G., 1968, Geology 2 3100 40 converted to altitudes above sea level by subtracting the depth values and ground water resources of the Kalispell valley, 0 3100 from land-surface altitudes. Altitudes along previously published northwestern Montana: Montana Bureau of Mines and 3200 2500 cross sections were obtained from topographic maps. Land-surface Geology, Bulletin 68, 42 p. 260 0 2700 3500 altitudes at well locations were obtained from the DEMs using Lange, I. M., and Zehner, R. E., 1992, Geologic map of the Hog ArcInfo computer software. Comparison of well-location altitudes Heaven volcanic field, northwestern Montana: Montana determined in the field from topographic maps with those derived Bureau of Mines and Geology Geologic Map 53, scale from the DEMs showed that most calculated values were within 20 1:50,000. feet of the field-determined values. Boreholes drilled to bedrock LaPoint, D. J., 1971, Geology and geophysics of the southwestern along the cross sections of one geophysical survey showed that the Flathead Lake region, Montana [M.S. thesis]: Missoula, 24 W error in that seismic refraction data was less than 20% (Briar, 1987). Montana, University of Montana, 110 p. 0
0 0 0
3 0 Well-log data from wells near cross sections in other geophysical Mudge, M. R., Earhart R. L., Whipple, J. W., and Harrison, J. E., 1 30 3 0 0 o o 33 surveys (Konizeski and others, 1968; LaPoint, 1971; Stickney, 1980; 1982, Geologic and structure maps of the Choteau 1 x 2 00 2 3200 Boettcher, 1982; Slagle, 1988) suggests that, in general, the depths quadrangle, western Montana: Montana Bureau of Mines and 80 17 N 0 200 29 3100 17 N 0 2 to bedrock were overestimated by the gravity and seismic refraction Geology Miscellaneous Investigations Map I-1300, scale 0 70 23 W 0 2900 interpretations. Where possible, the contours on bedrock that were 1:250,000. 3000 derived from geophysical data were shifted to honor the drill-hole Ó Cofaigh, C., 1996, Tunnel valley genesis: Progress in Physical 3100 2700 values, but their shapes were retained. On the map of bedrock altitude, Geography, v. 20, p. 1-19. solid or long-dashed contours honor data picked from well logs and Ostenaa, D. A., Levish, D. R., and Klinger, R. E., 1995, Mission fault 3400 the altitudes of bedrock outcrops; dotted contours were form-fitted study: Denver, Bureau of Reclamation Unpublished Report, 3 3300 0 2800 0 0 29 to the geophysical data interpretations. All contours were drawn by Seismotectonic Report 94-8, 111 p. 00 3100 hand and then digitized. Ostenaa, D., Manley, W., Gilbert, J., LaForge, R., Wood, C., and 22 W 3000 3 Arlee 00 The depth-to-bedrock maps were created by subtracting gridded Weisenberg, C. W., 1990, Flathead Reservation regional 40 values of the bedrock surface altitude from the DEM land-surface seismotectonic study: An evaluation for dam safety: Denver, 2 3100 3400 0 3 8 1 0 50 0 0 0 0 3 1 topography using ArcInfo. The resulting depth to the bedrock Bureau of Reclamation Unpublished Report, Seismotectonic 0 0 0 2 0 0 9 0 5 0 36 0 00 surface grid was smoothed and contoured using ArcInfo. The Report 90-8, 161 p.
0 contours were edited by hand, especially near bedrock outcrops, and Slagle, S. E., 1988, Geohydrology of the Flathead Indian Reservation,
0
0 9 2 further smoothed to reduce jagged traces that resulted from the Northwestern Montana: U.S. Geological Survey Water 16 N 3300 16 N gridding techniques. Resources Investigations Report 88-4142, 152 p.
0 0 20 W Smith, L. N., 2002, Surficial geologic map of the upper Flathead 0 0 0
0 7 0 3 3 16 N 5 DISCUSSION River valley (Kalispell valley) area, Flathead County, Montana: Scale Montana Bureau of Mines and Geology Ground-Water 32 00 00 31 0612 0 Regional Configuration of the Bedrock Surface Assessment Atlas 2, part B, map 6, 1:70,000. 20 W 0 2 33 Smith, L. N., Blood, L., and LaFave, J. I., 2000, Quaternary geology, 21 W 00
340 0 Structural movement and erosion causes irregularities in the geomorphology, and hydrogeology of the upper Flathead miles 35 Figure 1. Contour map of the altitude of the bedrock 00 bedrock surfaces altitude. The bedrock surface beneath the Kalispell valley area, Flathead County, Montana, in, Roberts, S., and surface in the Flathead Lake area. 3600 valley (upper Flathead River valley) rises from near sea level, west Winston, D., eds., Geologic field trips, western Montana and 0 1:150,000 0 9 3 of the northernmost Swan Range, to about 2,100 feet above sea level adjacent areas: Rocky Mountain Section of the Geological 3800 15 N near the northern end of Flathead Lake. Between the north end of Society of America, University of Montana, p. 4163. Universal Transverse Mercator 19 W Flathead Lake and the central Mission valley, bedrock generally rises Stickney, M. C., 1980, Seismicity and gravity studies of faulting in Zone 11 an additional 500 feet in the deepest part of the valley along the the Kalispell valley, northwestern Montana [M.S. thesis]: Datum NAD 1927 Mission Range. The variation in altitudes shows that the amounts of Missoula, Montana, University of Montana, 82 p. vertical datum is mean sea level subsidence differed between the intermontane basins north and south Wold, R. J., 1982, Seismic reflection study of Flathead Lake, Montana: 15 N 4000 of Flathead Lake. In that the sedimentary fills in the basins in the U.S. Geological Survey Miscellaneous Field Studies Map 0 0 9
3 southern half of the map area are less than the topographic relief of MF-1433, scale 1:115,000.
4 0
0
0 adjacent mountain ranges, the structure of these basins is unlike many 114o other intermontane basins in Montana, where basin depths are 19 W