Montana Bureau of Mines and Geology Ground-Water Assessment Atlas No. 2, Part B, Map 6 A Department of Montana Tech of The University of Montana December 2004

114o

R19W 48o30’ R20W R21W Qal Qal T32N R22W Qgta Ybe Qgt 114o 37’ 30” R23W Qao Qgo R24W Qgt Qao o Ybe Qgt 48 30’ Qgo Qgt Ybe Qgo Qgt T32N Ybe Tk Qgt Qgt Qls Ybe Qaf Qgo Qao Qaf Qgta Ybe Qgo Qgt Ybe Key to Symbols Qal Ybe Qal Qao Qal Qgt Qaf Qgt Contact, dashed where approximate Qgo Ybe Qgt Ybe Qls Qgo Qlk Ybe Qls Stream 71 Ybe Qgt 82 Qgt W Qls Qgoo h Qls Road Ybe Tk 70 it Qgo Qaf e Qgta Qgo 81 Township boundary, section boundary Ybe f Qgta Qgo i 21a s 83 28 Tk h Tk 21 T31N Population center Qgl L 23 22 Qls Qgt 69 a 27 Marsh Ybe Qgt Ybe k Qgta 24 e Qgo 26 25 Qgo Qgt Qgt Qgoo Lake or reservoir Ybe Qls Qlk 84 Qgo T31N Qal Qgt Tk Qgt Qgt 5 Location where geologic notes were recorded, photographs taken, and/or a vertical Qlk Qal Qaf section was described. Qgt Ybe Qal Qgo Qlk Ybe Qgt Qgt Ybe Ybe Qgo GLACIOFLUVIAL CHANNEL - Channelized depressions recognized from aerial Qgo Qgo Qgt Qal photographs and topographic expression; associated with deposits of glacial outwash Ybe in some areas; multiple types of channels are represented: ice-marginal channels: Ybe Qgt Qgt Qgi Qaf Qgo Qgta Qgo Qgo Qgi irregular linear erosional channels formed by channelized flow next to, or partially Qgo Ybe 73 Qgo Qgl Tk beneath the lateral margins of glaciers; commonly form notches, meander loops, and Qlk 74 Qgt Qgt Ybe Qgt Qgo some integrated drainage networks in bedrock or till that then may have become modern streams; some contain series of internally drained depressions (pools formed Qgt 66 Qgo Qgl Qgt Qgi Qal Qaf Qgo by scour). Abandoned alluvial channels: channel traces in unconsolidated deposits Qal T Qaf Qe Qe Qgo that show the positions of abandoned distributary channels across outwash. Paleoflood a Qgo Qgi l Ybe Qgo Whitefish Qgt channels: channels formed predominantly in bedrock or till formed by catastrophic l Qgt Qgo 75 Ybe y Qgl 78 Qao 32 80 releases of water. Qgt 68 Qal 72 QTs Qgl Qgta Qgo Qal Qgt L 76 Qgo Qgt 33 Qgo Ybe a Qgo Qgi Ybe Qgta Qao 34 Qgi Qgls Qgoo CREST OF DEPOSITIONAL LANDFORM - Ridgetops of landforms formed on k Qgi Qgi Ybe Pleistocene or Holocene sediment; multiple types of landforms are represented: e Qlk QglQgo Ybe Drumlins and moraines: mostly oriented parallel to glacier-flow directions, in till Qgt Qgl Qgo Qgo Hungry Horse deposits; Kames: conical and elongate ridges, in ice-contact deposits; Disintegration Qgl Qgt Qgo Qgi Columbia Falls Qgl ridges: elongate, sinuous and intersecting ridges, in ablation till (Gravenor and Qaf Qgt Qao Qgo Qgt Qal Qgl Qgl Kupsch, 1959; Flint, 1971; Goldthwait, 1975); Eolian dunes: crests of stabilized Ybe Ybe Qgl Qgo dunes, in eolian sand; Debris-flow levees: ridges formed parallel to margins of debris Qaf Qgt Qgo Qaf Qgo Qgt Qao flows, rare in ablation till and ice-contact deposits in areas of high relief. Qge Ybe Qgt Qe Qgt Qlk 77 79 35 Ybe Qaf Qaf Qgt 31 SCALE 1:70,000 Qgta Qgl Qlk Qgo Qao Qaf Universal Transverse Mercator Projection Qgt Qgo Qgl T30N 67 Qao Zone 11 Qgt Qgo 30 Datum NAD27 Qgo S Ybe t Qgta 29 Qgta il Qgo Qao Ybe Qgo l Ybe 39 40 41 w Qgta 45 Qgt Qgt Qaf Hungry T30N a 46 Qgi 44 Qgo Qgo t Qao Qao Horse Qgt e 19 43 Qgl 36 20 42 Reservoir r 18a Qgt Qgo Ybe Qe Qe 18 Qls Correlation of Units Qgt R i Alluvium Eolian Alluvial Fan Landslide Lacustrine Till and Ice Contact v Qgt and Outwash Deposits Deposits Deposits Deposits Deposits Qgo e Qgo Qgta Qgl r Qaf Qgt Qgl Qgo Qal Ybe Qe Qaf Qls Qlk Qgl Qao Qaf Holocene Qgo Qgta Qao Qgo Qgls Qgo Qao Qgi Qgl Qgt Qgt Qgta Qgo Qgi Qgi Qge Qgt Qgo Qao 85 Qgta Qgt Qgta Qe Qao Qgt 86 Qgl Pleistocene Qgi 86a Ybe L Qao Qgo Qgt Qao Qgoo o Qe 86b Qgo st 86c Qaf QTs ? QgoC Qge 87 88 unconformity r Qgt Qgt Kishenehn Formation eek Ybe Qgt Eocene - Ybe Qgt Qgl 17 Qal Qe Qgo Qgt 15 Qgo Tk Miocene Qaf Qgt Qgo Qgt Qe unconformity Ybe Qge Qgl 16 Qgt Qgt Qgi Belt Supergroup Middle Qe Qgt

Qgt r Ybe Proterozoic

Qe e Qgo Qgt Qaf Qe v

T29N i Qgi Qgt

Qgo Qgo 13 14 T29N R Qgl Qgt Ybe Qe Qe 12 Qgta Qgi

h Qe Qaf Qgo Qe Qgt Qe s Qgi Qgt i Qal

Qe f Qe Qe Qgi Qgo Qgt Qgi Qgl e Qgi Qgt t Qgl i Qgta h Qlk Qgo Qgi Qgt Qgi Ybe W r Lake Blaine Qgt Qe e Qgl Qgt Qal v Qgl Qgi Qgi i Qgt Qgt R Qaf Qao Qgi Qgo Qgt Qao 65 Qao Qaf R23W Qal Qe Qgt R24W Qgl d Qgi Qgt Qgo Qgt Qgt a Qao Qgt e 10 Qgi h Ybe Qgta Qgi t Qgl Ybe Qgta a Qaf Qao l Qgt F Qgi Qgo Qgi Qgo 11 Qe Qgi Ybe Ybe Qgt Qgls Qal Qgta Qgi Qgl Qgl Qaf Qgt Qgta Ybe Ybe Qgi 90 Qgt QgoQgls Qgi Qgi Qgo Qgls 8 Qgi Qgo Qgl Qgls Qgta Qgo Qgl 8a Qao Qaf Ybe Qao Qgi 7 Ybe Qao Qgl Ybe 9 Qgi Qgo Qgi Qgt Kalispell Qgls Ybe 89 Qgt Qgl Qgi Qaf Qe Qgo T28N Qgo Qgi Qge Qgt Qgo Qgo Ybe Qgi Qgo Qgi Qgi Qgo Qgi Qgl T28N Ybe Qge Qgi Qgi Qgo 6 Qgt Qgi Qgo Qgo Qgo Qgta Qal Ybe Foy Lake Ybe Qgi Qge Qge Qgta Qao Qgi Qgt Ybe Ybe Qgta Ybe Qao Qgo Ybe Qao Qgo Qgta Ybe Qgo Qgo Qgo Qal Qgo Ybe Qal Ybe Ybe 5 Qgt Ybe Qal Echo Lake Qlk Ybe T27N Qgta Qal Ybe Qgo Qgi Ybe Qgta Ybe Ybe o Qgo Qgo 48 07’30” R22W R23W Qgi 114o30’ Qal Description of Map Units Qgt Qlk Qgo Qal ALLUVIUM OF MODERN CHANNELS AND FLOODPLAINS (Holocene) - Light to medium brown and grayish brown sand and silt, Ybe Qgt Qao and lesser amounts of pebbles, cobbles, and clay along active stream valleys and areas of sheetwash; contains minor amount of colluvium Qgt Qe Qgls T27N Qao 2 4 along the bases of steep slopes; thicknesses average 30 feet, but reach 90 feet in paleochannels south and southeast of Kalispell; ground 61 Qge Qgi Qge water commonly near land surface; produces significant quantities of water. Ybe Qgi 3 1 Ybe Ybe Ybe Qao Qaf ALLUVIAL FAN DEPOSIT (Holocene) - Grayish brown and light to dark yellowish brown sand, silt, pebbles, cobbles, and boulders Ybe Qgt deposited in fan-shaped landforms downslope from canyon mouths; thicknesses range from 1 to 60 feet; ground water commonly near T27N Qlk Ybe Ybe Qgo land surface; locally produces water. Qaf Qgt Qgl Qao Ybe Qe EOLIAN DEPOSIT (Holocene) - Dark to light yellowish brown fine and very fine-grained well sorted sand deposited as eolian dunes and Ybe Ybe Ybe sand sheets; grains mostly of quartz with common argillic or calcareous rock fragments; pebble-sized clasts of argillite, quartzite, and 62 weakly consolidated siltstone occur as rare particles in deposits and locally as layers on or near the ground surface; a distinctive bed of 60 Qgi white to very pale orange volcanic ash (Glacier Peak ash, dated at 11,200 14C yr; Carrara, 1995) occurs within or near the base; bedding Qgi Qgt Qgt Qgl is massive where the unit is thin, but wind-ripple cross-laminations and large-scale sandflow cross stratification are common in thicker Qal Ybe Ybe deposits; the deposit is truncated near stream courses by alluvium; soils occur at the surface and buried within the deposit; dune forms Qlk are poorly preserved due to modification during stabilization and post-depositional erosion; thickness ranges from 1 to 40 feet; water table Qgls is typically below the unit, but the unit may be saturated seasonally; not known to produce significant quantities of water. Bigfork Qao Qao Qlk LAKE DEPOSIT (Holocene) - Mostly calcareous silt, clay, and organic debris deposited in perennial and ephemeral lakes; includes minor amounts of sand and gravel; distribution of unit inferred beneath lakes and marshes; thickness unknown, but likely 1-30 feet; ground water Ybe Qgo Ybe Ybe S commonly near land surface; not known to produce water. Ybe Qgl w a Qgta Qls LANDSLIDE DEPOSIT (Holocene and upper Pleistocene) - Boulders, cobbles, and pebbles in a light to dark brown matrix of sand and QTs Qls n Ybe Qgo

silt; clasts are mostly angular and subangular; deposited by gravity sliding to an area near the base of a hill or mountain slope; surface of 59 Qgt R

unit is typically hummocky and lobate in form; thickness ranges from 1 to 80 feet; ground water commonly near land surface; locally Ybe i Ybe v

produces water. Ybe Flathead e Qlk r Ybe Ybe Qao ALLUVIUM, OLDER (Holocene) - Light to dark brown and grayish brown sand, pebbles, cobbles, and minor silt and clay; upper surface Ybe T26N forms terraces near major stream valleys; topographic position intermediate between active stream valleys and areas of outwash deposition; Lake Ybe thickness ranges from 1 to 40 feet; ground water commonly near land surface; produces significant quantities of water. Ybe Ybe Qgo GLACIAL OUTWASH DEPOSIT (upper Pleistocene) - Light brownish gray and light to dark brown stratified gravel, sand, and silt; clasts Ybe of calcareous siltite, quartzite, intrusive igneous rocks, sandstone, and siltstone; well stratified, channelized, and cross stratified with Qgta lenticular beds of imbricated cobbles and pebbles; rare boulders and larger clasts indicate ice-rafting; upper surface is broad and even with Ybe Qgta Ybe Qgi local closed depressions and abandoned glacio-fluvial channels; thicknesses average 50 feet and are locally more than 140 feet; ground Qal Swan Lake water commonly near land surface; produces significant quantities of water. 64 64a Ybe Qgt 48o Qgl GLACIAL LAKE DEPOSIT (upper Pleistocene) - Light yellowish brown, pale brown, and light brownish gray, calcareous fine sandy Ybe Qao Qgta R18W o silt, clayey silt, and minor clay; thin to medium laminations rhythmically alternate between darker-colored clay-rich laminae and lighter- Qal R19W 113 52’30” colored and thicker silty and sandy laminae; deposit has broad, even surfaces except for few closed depressions; deposited from suspension T26N Ybe Ybe Ybe in pro-glacial lakes formed behind glacial moraines; thicknesses average 100 feet and are locally greater than 270 feet; typically water- R20W saturated, but produces little water to wells. R21W Qgls GLACIAL LAKE DEPOSIT, SANDY (upper Pleistocene) - Light yellowish brown fine to medium-grained sand, conglomerate, sandy silt, silt, and minor clay; similar to Qgl, but consists predominantly of sand with lesser amounts of rhythmically laminated clay and silty Surficial Geologic Map of the upper Flathead River valley (Kalispell valley) Area, Flathead County, Northwestern Montana and sandy laminae; lenticular granule, pebble, and cobble conglomerate locally overlies beds displaying soft-sediment deformation; deposited in nearshore environments in pro-glacial lakes; deposits have broad, flat surfaces and few closed depressions; thicknesses average by 50 feet but locally are more than 150 feet; typically water-saturated, but only locally productive to water wells. Larry N. Smith Qgt GLACIAL TILL (upper Pleistocene) - Predominately granules, pebbles, cobbles, and boulders supported by a matrix of light gray, light brownish gray, pale yellowish brown, grayish orange, and pale brown, compact sandy or silty loam (diamicton) deposited by active glacial INTRODUCTION properties will be combined with subsurface data derived from water some intrusive igneous rocks in areas contiguous to the map area also 22 W.), (2) along the Whitefish River valley west of Columbia Falls ACKNOWLEDGMENTS ice; minor amounts of stratified sand and gravel (stratified drift) deposited by flowing water; clast lithologies include light and medium wells and their logs to produce additional maps showing the depth to provided some of the sediment for the valley. These bedrock units were (secs. 19-21, T. 30 N., R. 21 W.), (3) in the town of Whitefish (secs. bluish gray metacarbonate, white weathered metacarbonate, fine-grained quartzite, argillite, diorite, and distinctive cobbles of dark gray The upper Flathead River valley (Kalispell valley) is an and thickness of aquifers and confining units. faulted and folded during early Cenozoic eastward thrusting (~60 million 25, 26, 35, 36, T. 31 N., R. 22 W.), and (4) along the Stillwater River This map was prepared in conjunction with the Flathead Lake to black basalt with amygdules filled with white quartz that contains many fluid inclusions, apparently derived from the Purcell Lava of intermontane valley north of Flathead Lake that is bordered on the east Previous mapping of surficial deposits by Konizeski and others yr [60 Ma] ). valley between Whitefish and Talley Lake (sec. 31, T. 31 N., R. 22 W. Study of the Ground-Water Characterization Program. Reviews of the the Belt Supergroup, which is present in Glacier National Park and the Whitefish Range to about 10 miles north of Columbia Falls (Johns, by the Swan and Mission Ranges, on the north by the Whitefish Range, (1968) was done for part of the study area at a scale of about 1:70,000. The upper Flathead River valley is part of the southern end of and sec. 36, T. 31 N., R. 23 W.). Wasting, stagnant glacial ice deposited manuscript and map by Lex Blood, Tom Patton, Wayne Van Voast, 1970; McGimsey, 1985); clasts typically rounded and subrounded; more resistant clasts are commonly striated; crests of glacial landforms and on the west by the Salish Mountains. The northern part of the Swan Their depiction of the distribution of till, outwash, glacial lake sediments, the Rocky Mountain Trench, an asymmetric, fault bounded half-graben ablation till deposits (Qgta) which has characteristic hummocky and Ed Deal improved their quality. GIS analysis and processing was include drumlins and moraines; occurs as a veneer over Belt Supergroup rocks in most mountainous areas; glaciofluvial channels cut across River valley is included in this discussion (fig. 1). The valley is drained and alluvium is similar to that of this map, although different in detail. in which bedrock strikes northwest and dips northeast. The trench and topography, such as the intersecting crests of landforms between Echo done by Bill Myers and Ken Sandau. Computer cartography was done the unit and some of the drumlins and moraines; thicknesses average 90 feet and are locally more than 250 feet; typically water-saturated, by the Flathead River and its major tributaries, the Stillwater and Contacts shown between till and bedrock in the mountainous areas other northwest-trending valleys were defined during a regional Lake and Lake Blaine in the east half of T. 28 N., R. 20 W. Generally by Don Mason. but produces little water to wells except from bodies of stratified drift. Whitefish Rivers in the northwest, the Swan River in the southeast, and surrounding the valleys were almost entirely compiled from previous southwest-directed extensional event that followed early Cenozoic level surfaces with internally drained depressions south of Lake Blaine Ashley Creek on the west. Elevations range between 7,528 feet on the mapping (fig. 2) and should be considered approximate. eastward thrusting (Constenius, 1996). The sedimentary rocks of the (secs 34 and 35, T. 29 N., R.20 W. and secs. 4-5, T . 28 N., R. 20 W.) REFERENCES crest of the Swan Range to 2,892 feet, the summer pool elevation of Kishenehn Formation accumulated from 48–21 Ma in the valley of and northwest of Kalispell (T. 29 N., R. 22 W.) wre produced by outwash Qgta GLACIAL TILL, ABLATION DEPOSIT (upper Pleistocene) - Granule, pebble, and cobble conglomerate, and lesser amounts of light (1) gray, light brownish gray, pale yellowish brown, grayish orange, and pale brown, compact beds of diamicton and stratified beds of sand; Flathead Lake. The area’s geomorphology consists of a low-relief South Fork of the Flathead River, in the northeastern part of the map depostion near ice blocks. As the ice blocks melted the land surface Carrara, P. E., 1990, Surficial geologic map of Glacier National Park, interstratified complex of massive till, poorly bedded ice-contact deposits, and well-stratified drift; formed during disintegration of glacial floodplain along the Flathead River, that broadens markedly south of area, and outside the map area in the valleys of the Middle and North locally collapsed, forming depressions. A major landslide (Qls) fell Montana: U.S. Geological Survey Miscellaneous Investigations ice; characterized by knob and kettle topography with some elongated crests of glacial landforms representing crevasse-fills, eskers, and Kalispell; flights of terraces along the main river valleys; and rolling Forks of the Flathead River. A period of east-west directed extension westward into the upper Flathead River valley from sec. 26, T. 30 N., Series Map I-1508-D, scale 1:100,000. uplands above the terraces that contain drumlinoid glacial landforms. Map beginning in the Miocene (17 Ma) is responsible for north-south trending R. 20 W., near the north end of the Swan Range while ice remained in Carrara, P. E., 1995, A 12,000 year radiocarbon date of deglaciation kames; thicknesses range from 1 to 150 feet; although lateral and vertical variations in lithology affect potential for ground-water development, Area typically produces water to wells in most locations. The transition to the Swan Range is abrupt along the east side of the faulting, which defines the western flanks of the Swan and Mission what are now neighboring kettle lakes. from the continental divide of northwestern Montana: Canadian valley, whereas, alluvial fan and glaciated surfaces form more gradual Ranges (Constenius, 1996). Most of the displacement along these faults Till (Qgt) in many areas is directly overlain by laminated glacial Journal of Earth Sciences, v. 32, p. 1303-1307. Qge GLACIAL ESKER DEPOSIT (upper Pleistocene) - Pebbles, cobbles, boulders, and some light to medium brown sand; most clasts are footslopes along the Whitefish and Salish mountains to the north and took place on the east-northeast side of the upper Flathead River valley. lake deposits (Qgl) deposited in a lake dammed behind the Polson Constenius, K. N., 1988, Structural configuration of the Kishenehn well rounded cobbles; some exposures display horizontal bedding; clasts of grayish black to medium dark gray metacarbonate, argillite, west. Outside of suburban areas, the valley is vegetated by various (2) Geophysical profiling suggests there is more than 3,000 feet of Tertiary moraine (fig. 1). Rotated blocks of glacial-lake sediments (sec. 36, T. Basin delineated by geophysical methods, northwestern Montana light gray and medium gray bedded quartzite, weathered calcareous mudstone, and distinctive cobbles of dark gray to black basalt (Purcell crops, introduced and native grasses, and deciduous forests in low-lying and Quaternary sediment in the valley (Konizeski and others, 1968). 31 N., R. 22 W., and sec. 21, T. 30 N., R. 21 W.) indicate melting and and southeastern British Columbia: Mountain Geologist, v. 25, Lava); forms narrow, sinuous ridges; thicknesses range from 1 to 60 feet; ground-water levels typically below the unit, but the unit may areas and conifer forests in hilly and mountainous areas. Siltstone, sandstone, and carbonaceous claystone encountered in boreholes collapse of, or push by, glacial ice in the lakes. Maximum elevation of n. 1, p. 13-28. be saturated seasonally; the unit is not known to produce significant quantities of water. in the south half of T. 31 N., R. 21 W. and in the Swan River valley, the lake dammed by the Polson moraine was 3,200 feet, about 300 feet Constenius, K. N., 1996, Late Paleogene extensional collapse of the Canada just southeast of the map area, may be Tertiary basin-fill deposits that higher than the current Flathead Lake. As the glacial sediment dams Cordilleran foreland fold and thrust belt: Geological Society of have not yet been recognized in outcrop. were downcut, lake levels receded, streams incised valleys, and outwash— America Bulletin, v. 108, p. 20-39. Qgi GLACIAL ICE-CONTACT DEPOSIT (upper Pleistocene) - Light to dark brown and brownish gray pebble and cobble conglomerate with F Montana Whitefish Rge.la derived from glaciers that had retreated to mountainous areas— was Flint, R. F., 1971, Glacial and Quaternary geology: New York, Wiley, lesser amounts of laminated silt and clay, bedded sand, diamicton, and boulder conglomerate; clast lithologies dominated by rounded and th e a (3) (4) GLACIAL AND POST-GLACIAL HISTORY deposited. 892 p. subrounded argillite, metacarbonate, and quartzite with minor siltstone, sandstone, fossiliferous limestone, and distinctive cobbles of dark Map Area d R Flathead Lake Ice-marginal channels and prominent valleys with underfit Goldthwait, R. P., ed., 1975, Glacial deposits: Stroudsburg, Dowden, i gray to black basalt (Purcell Lava); beds of different lithologies are superimposed and cross cutting, forming complex sequences; soft- v e Characterization and frozen-sediment rotational and collapse features are common; conglomerates display large- and very large-scale tabular and trough r The upper Flathead River valley and nearly all of its neighboring streams between Talley Lake and the Lost Creek area north of Kalispell Hutchinson, and Ross, Inc., 464 p. Study Area mountain areas were covered by glacial ice during latest Pleistocene are evidence for one or more catastrophic releases of meltwater into the Gravenor, C. P., and Kupsch, W. O., 1959, Ice-disintegration features cross-stratification, crude horizontal stratification in a matrix of granules and coarse-grained sand, and clast imbrication; laminated silt Libby and clay sequences are mostly less than a few feet thick and discontinuous in outcrop; sand occurs in cross-stratified, upward-fining beds, time (~15,000-25,000 yr); ice thicknesses in the valleys reached about upper Flathead River valley. The pattern of channels cut in bedrock and in western Canada: Journal of Geology, v. 67, p. 48-64. and as apparently massive, well-sorted beds with intercalated silt and clay laminae that show collapse structures; diamictons are typically 4,000 feet. Erosion and burial of sediments during the most recent till suggest that when the glacier terminated between Talley Lake and Harrison, J. E., Cressman, E. R., and Whipple, J. W., 1992, Geologic Figure 2. Index to previous maps from which some contacts were glacial period has hindered documentation of older glacial sequences. Whitefish, water was impounded behind an ice dam in the northern and structure maps of the Kalispell 1 x 2-degree quadrangle, less than a few feet thick and occur as sheet-like bodies and dipping beds apparently deposited by debris flows; forms individual conical Salish Mtns. and stream-lined hills (kames), flat-topped ridges (kame terraces), and linear deposits (crevasse-fills), and hummocky topography (Gravenor Kalispell Swan Rge. compiled: (1) Carrara (1990), (2) Harrison and others (1992), (3) Two small exposures of oxidized diamicton, an unsorted deposit in Salish Mountains. Release of water caused extensive scouring of bedrock Montana, and Alberta and British Columbia: U.S. Geological and Kupsch, 1959; Flint, 1971; Goldthwait, 1975); changing proportion of lithologies causes unit to grade into areas mapped as till, ablation Witkind (1978a), (4) Witkind (1978b). which pebble to boulder-sized clasts are supported in a matrix of sand and till, entrenchment of distributary channels, and deposition of the Survey Miscellaneous Investigations Series Map I-2267, scale and silt or clay (Qts) in sec. 6, T. 26 N., R. 20 W. and sec. 33, T. 31 N. “Lost Creek outwash fan” northwest of Kalispell (northwestern corner 1:250,000. deposits, and glacial esker deposits; thicknesses range from 1 to 150 feet; lateral and vertical variations in lithology affect potential for Mission Rge. ground-water development in the unit; typically productive to water wells in most locations. Swan River METHODS AND DATA SOURCES R. 22 W., may be either older till (Stoffel, 1980) or Tertiary debris flows of T. 29 N., R 22 W.) . Harrison, J. E., Whipple, J. W., and Lidke, D. J., 1998, Geologic map (P. C. Ryan, written comm., 1999). As the ancestral Flathead Lake receded within the valley, exposed of the western part of the Cut Bank 1 x 2-degree quadrangle, Idaho Qgoo GLACIAL OUTWASH DEPOSIT, OLDER (Pleistocene) - Light and medium brown, yellowish brown, and brownish gray granule, pebble, Mapping was carried out by interpretation of 1954-vintage Quaternary surficial deposits that cover the valleys are almost lake, outwash, and till deposits were partially eroded by wind and northwestern Montana: U.S. Geological Survey Geologic and boulder conglomerate and coarse-grained sand; local calcium carbonate cement; clasts of quartzite and meta-carbonate; trough cross- Polson Moraine 1:20,000-scale black and white stereo aerial photographs. Contacts were everywhere vegetated, but are locally exposed in natural and artificial deposited as eolian dunes and sand sheets, mostly in the central and Investigation Series I-2593, scale 1:250,000. stratified and channelized beds; clasts are imbricated; crops out beneath till in steep exposures in the northeastern part of the map area; Polson hand plotting on 7½-minute topographic maps. Field checking and cuts along stream banks, roads, and in excavations for sand and gravel. eastern parts of the valley (T. 29 N., R..21 and 22 W. and T. 29 and 30 Johns, W. M., 1970, Geology and mineral deposits of Lincoln and revision was then done. Descriptions of outcrops and vertical profiles, The deepest cuts, and most complete exposures occur in the northeastern N., R. 20 W.). A 1-inch-thick bed of volcanic ash within the dunes (Field Flathead Counties, Montana: Montana Bureau of Mines and exposed thicknesses are about 100 feet (sec 7 DDB, T. 31 N., R. 19 W.); based on its location below till the unit correlates to upper part Fla the er photographs, and additional field notes made at numbered field locations part of the map area, along the Flathead River between Hungry Horse location 87, sec. 9, T. 29 N., R. 20 W.) and locally at the base of eolian Geology Bulletin 79, 182 p. of the deep aquifer north of Flathead Lake. ad Riv on the map are available from the author. The geologic data was and Glacier National Park, outside of the upper Flathead River valley. deposits (Konizeski and others, 1968) was derived from an eruption of Konizeski, R. L., Brietkrietz, A., and McMurtrey, R. G., 1968, Geology transferred to mylar, scanned, and digitized in ArcInfoTM. Alluvium beneath till, which may represent outwash of an advancing Glacier Peak in Washington state (A. Sarna-Wojcicki, USGS, written and groundwater resources of the Kalispell valley, northwestern QTs QUATERNARY OR TERTIARY SEDIMENT (Pleistocene or Tertiary) - Pale yellowish orange to grayish orange (dry), moderate to dark 14 yellowish orange (moist) stony clay loam (diamicton); clasts include weathered meta-carbonate and argillite; unit infills wide fractures in The topographic base data are from digital elevation models glacier (Qgoo), is exposed in secs. 7, 8, and 17, T. 31 N., R. 19 W. comm., 1999). The volcanic ash was deposited at about 11,200 C yr Montana: Montana Bureau of Mines and Geology Bulletin 68, Location (DEMs) available from the Montana Natural Resource Information along the Flathead River upstream of Hungry Horse. Compact till (Carrara, 1995) and dates the time of major eolian deposition. Buried 42 p., scale 1:63,360. Belt Supergroup bedrock and occurs beneath light brown unweathered till in limited areas; diamicton may be either an older till (Stoffel, Key Sask. Missoula BC Alberta System (NRIS). Vertical and horizontal linear artifacts in some of the deposited at the base of the Flathead Lobe of the Cordilleran ice sheet and surficial soils of various stages of development suggest multiple McGimsey, R. G., 1985, The Purcell Lava, Glacier National Park, 1980) or Tertiary debris flow deposits (P. C. Ryan, written comm., 1999); exposed thickness about 30 feet; subsurface distribution and Streams Study Area ND data cause apparent striping and irregularities in the shading. Digital is well represented along the Flathead River in T. 31 N., R. 19 W. and periods of eolian activity. Montana: U.S. Geological Survey Open-File Report 85-543, aquifer potential of the unit is poorly known, however its clayey texture suggests the unit is not an aquifer. WA Southern Montana base data of roads are from NRIS; streams and lakes are from the U.S. in the drumlin field between Whitefish and Kalispell (T. 30 N., Rs. 21- Topography on the base of glacial lake deposits (e.g. Field 191 p. Extent of SD Pleistocene Forest Service, Flathead National Forest, Kalispell; public land surveys 22 W.). Location 36, sec. 22, T. 30 N., R. 21 W.) indicates that downcutting Stoffel, K. L., 1980, Glacial geology of the southern Flathead Valley, Tk KISHENEHN FORMATION (upper Eocene-Miocene) - Yellowish brown to orange medium and coarse-grained pebbly sandstone with OR ID WY pieces of carbonized wood fragments, pebble and cobble conglomerate, beds of carbonaceous shale, and light olive gray, dusky moderate Glaciers were digitized at Montana Bureau of Mines and Geology from 7½- Most of the surficial geologic units were deposited during and along major stream valleys began before lacustrine sedimentation and Montana: Missoula, University of Montana, M.S. thesis, 149 p. yellow, and grayish orange mudstone; conglomerate with silty, sandy matrix, well and moderately rounded clasts of argillite, quartzite, minute quadrangles. after retreat of the last glacier from the valley. Ice-marginal streams cut has continued to the present. Lateral planation by the Flathead River Winston, D., 1986, Belt Supergroup stratigraphic correlation sections, and orange siltstone; horizontal bedding and imbricated fabric; sandstone and conglomerate beds have channelized, erosional bases; Figure 1. Index map showing the location, principle roads and cities, channels and conspicuous meander loops into west-southwest-facing across its floodplain and the formation of stream terraces has dominated western Montana and adjacent areas: Montana Bureau of Mines mudstones have common scoop-shaped, concave-up fractures; moderately indurated with calcium carbonate cement; calcium carbonate drainages, and maximum extent of the last glacial advance. GEOLOGIC OVERVIEW flanks of the Whitefish and Swan Ranges and the Salish Mountains. Holocene erosion in the upper Flathead River valley. Deposition of and Geology Geologic Map 40, no scale. occurs locally as 0.04-0.2" thick rinds on clasts; steeply dipping, cemented fractures in sandstones; about 120 feet of section crops out in The channels record temporary positions of meltwater channels during sand, gravel, and mud in the modern floodplain of the Flathead River Witkind, I. J., 1978a, Preliminary map showing surficial deposits in the steep exposures (Constenius, 1988); water wells completed in sandstone and conglomerate yield adequate supplies of water for household This map shows the distribution of unconsolidated surficial The mountain ranges consist mostly of slightly metamorphosed the sequential lowering of ice levels in these areas. As the Flathead have accompanied a southward progradation of a modern delta into Big Fork quadrangle, Lake and Flathead counties, Montana: use in a few parts of the northeastern part of the map area and in the valley of the North Fork of the Flathead River. geologic units within the relatively densely populated upper Flathead sedimentary rocks, and a few igneous rocks, of the Proterozoic Belt Lobe retreated northward, till and ice-contact deposits recorded terminal Flathead Lake. U.S. Geological Survey Open-file Report 78-174, scale 1:24,000. River valley portion of the Flathead Lake Ground-Water Characterization Supergroup which have been the sources for most of the sedimentary positions where the receding ice remained stable or readvanced briefly. Witkind, I .J., 1978b, Preliminary map showing surficial deposits in the Ybe BELT SUPERGROUP ROCKS , UNDIVIDED (Precambrian Y) - Numerous stratigraphic units composed mostly of siltite, metacarbonate, Study area. Contacts between units with different hydrogeological fill in the upper Flathead River valley. Younger sedimentary rocks and These areas are (1) south and southwest of Kalispell (T. 28 N., R. 21- west half of the Crater Lake quadrangle, Lake and Flathead and quartzite (Johns, 1970; Winston, 1986; Harrison and others, 1992, 1998) and minor amount of igneous rocks (McGimsey, 1985); water counties, Montana: U.S. Geological Survey Open-file Report wells completed in fractured zones yield adequate supplies for household use. 78-173, scale 1:24,000