INDEX TO 1:250,000 TOPOGRAPHIC QUADRANGLES

Showing location of the Wolf Point 1° × 2° quadrangle in red

al agu Holocene

late

Pleistocene

wla

?

tlx

(s)

tlx

(e) tlx

lca lss hs

lb

ed

?

?

early

Pleistocene

eu

eux

cad

middle

Pleistocene

?

?

Pliocene

tks ggi QUATERNARY

TERTIARY

xsh

ckq

gg

Pleistocene

ke kg

GLACIAL

DEPOSITS

ICE-CONTACT

DEPOSITS

 GLACIOFLUVIAL

DEPOSITS

ALLUVIAL

DEPOSITS

LACUSTRINE

DEPOSITS

EOLIAN

DEPOSITS

COLLUVIAL

DEPOSITS

PALUDAL

DEPOSITS

 RESIDUUM

BEDROCK

 ILLINOIAN

 PRE-ILLINOIAN

CORRELATION OF MAP UNITS

R

llg

DESCRIPTION OF MAP UNITS

 [Map unit thickness is typical range; in some areas the map units may be thicker or 

thinner than the given range]

HOLOCENE AND LATE WISCONSIN

Flood-plain and channel alluvium—Yellowish-brown, olive-brown,

 grayish-brown, brown, olive, yellowish-gray, brownish-gray, olive-gray, gray, 

black, or mottled clay, silt, sand, and gravel. Calcareous or noncalcareous; partly 

or completely oxidized. Clasts are angular to well rounded. Clast composition 

reflects that of other surficial materials and bedrock in the drainage basin. 

Fossiliferous (gastropod, pelecypod, and vertebrate remains; wood fragments and 

plant detritus) in some places. Included in other map units in many areas. 

Includes some sheetwash alluvium, alluvial-fan deposits, alluvium beneath low 

terraces, outwash and ice-contact sand and gravel, lake deposits, and bedrock 

outcrops. Alluvium in some areas is dominantly redeposited outwash, ice-contact 

deposits, and lake deposits. Thickness 1–6 m, locally >20 m 

 Flood-plain alluvium—Chiefly poorly-sorted to well-sorted clay, silty clay, silty 

clay loam, clayey silt, and silt with scattered granules and pebbles; locally, loam, 

sandy clay loam, sandy loam, or fine sand. Moderately to well stratified. 

Commonly has either obscure bedding or pronounced horizontal bedding; weakly 

laminated in some places. Clay, silt, sand, or gravel lenses or small channel fills of 

sand and gravel are common. Dense and compact in most places. Clayey 

alluvium is moderately plastic, soft, and sticky where moist and hard where dry. 

Textures may vary abruptly, laterally and vertically. Local thin buried soils (humic 

horizons). Concentrations of detrital lignite (bedrock) fragments as large as 1 cm 

are common in crossbedded sand. Where flood-plain alluvium directly overlies 

lake clay, silt, and sand or sheetwash alluvium, in some places it is difficult to 

distinguish the deposits 

 Channel alluvium—Chiefly loose, stratified, poorly-sorted to well-sorted, pebbly, 

fine to medium sand and (or) coarse sand and gravel; locally very poorly sorted 

sandy shale-fragment gravel. Cobbles and boulders are common to abundant in 

some areas. Generally crossbedded or has crude horizontal bedding or lenticular 

bedding; local festoon bedding. Locally fossiliferous (chiefly vertebrate remains) 

Flood-plain and channel alluvium—Deposits in the northwest part of the 

quadrangle, similar to map unit al, preserved as terrace remnants higher than the 

postglacial alluvium. The deposits were derived from erosion of Tertiary bedrock 

and erosion and redeposition of Tertiary and Quaternary sand and gravel (see map 

unit xsh). Clasts are chiefly quartzite, argillite, chert, chert conglomerate, and 

sandstone. Rare redeposited clasts of erratic igneous and metamorphic rocks from 

the Canadian Shield are present in terrain possibly glaciated during the early 

Pleistocene or late Pliocene (see symbol “Limit Of Residual Erratic Glacial 

Boulders On Dissected Bedrock Surfaces”) or where they were ice rafted in one or 

more Pleistocene glacial lakes. Thickness 1–2 m 

 Lake clay and silt—Pale-yellow, grayish-yellow, bluish-green, yellowish-brown, 

olive-brown, grayish-brown, brown, olive, yellowish-gray, brownish-gray, 

olive-gray, bluish-gray, gray, olive-black, bluish-black, black, or mottled, 

calcareous clay and silt. Generally stratified; well sorted; massive or weakly 

bedded. Commonly laminated, locally varved, clay and silt. Generally clay in 

lower part and massive or horizontally-bedded silty clay and silt in upper part. 

Upper part generally is clast free; in some places, iceberg-rafted granules, pebbles, 

cobbles, and boulders are common in lower part. Clasts generally are absent on 

the surface. Contains local thin, discontinuous beds, lenses, or stringers of sand or 

fine gravel; pockets or pods of iceberg-rafted granules and pebbles, or isolated 

rafted erratic cobbles or boulders. Interbedded with sand, fine gravel, till, or 

flowtill in some places; some rare ice-rafted clasts of till are 1–2 m in diameter. 

Graded beds, silt blebs and nodules, or rip-up clasts of till or lake silt and clay are 

present locally. Strongly contorted in the northwest part of the quadrangle; slump 

structures, load structures, and folds in some places. Generally not faulted. 

Dessication cracks are common in some places. Commonly oxidized in upper 1-2 

m; local iron oxide stains. Soft to very firm; locally cohesive and compact. Very 

plastic and sticky when moist; hard when dry. Locally gritty. Dry clay and silt 

commonly breaks into chips or blocks. Clay minerals are dominantly 

montmorillonite. Selenite (gypsum) crystals <6 mm in length are present locally in 

fractures and are abundant in saline lake sediment. Secondary calcium carbonate 

concretions locally are present in upper part. Gullies are common in some places. 

Deposit is susceptible to landslide processes (chiefly slump) in exposures. Most 

deposits are offshore deposits of former lakes. Present beneath flat plains and in 

small basins formerly occupied by glacial and postglacial lakes and ponds. Flat to 

rolling or hummocky surface topography. Thin and discontinuous in some areas. 

Overlapped by flood-plain alluvium adjacent to some streams; overlapped by 

sheetwash alluvium adjacent to some bedrock outcrops. Includes lake silt and sand 

where lake clay, silt, and sand have not been distinguished. Includes some till with 

a thin veneer of silt and clay. Includes some ice-contact and outwash sand and 

gravel, small lake delta deposits, and bedrock outcrops. In some places, lake clay 

and silt are overlain by eolian silt and sand, alluvial-fan deposits, or flood-plain 

alluvium. Thickness 1–5 m, locally >15 m 

Lake sand and silt—Grayish-yellow, yellowish-brown, grayish-brown, brown, 

yellowish-gray, olive-gray, brownish-gray, gray, or mottled, calcareous silt and 

sand mixed with minor clay and gravel. Generally well stratified and well sorted. 

Typically horizontally-bedded or massive, fine or medium sand containing 

scattered granules or small pebbles. Commonly interbedded or intercalated with 

massive, bedded or laminated, silt containing dropstones; in some areas, chiefly 

laminated silt and fine sand. Commonly slumped and contorted on hillslopes. 

Detrital fragments of lignite (bedrock) are abundant in many areas, concentrated in 

sand crossbeds. Clasts are chiefly subrounded and rounded erratic limestone, 

dolomite, and igneous and metamorphic rocks and local sandstone and shale that 

were ice rafted or reworked from till. Present beneath lake plains and in small 

basins formerly occupied by glacial and postglacial lakes. Surface relief 1–4 m. 

Includes some lake clay and silt, flood-plain and channel alluvium, and till. In 

many places, overlies lake clay and silt. Thickness 1–8 m, locally >10 m 

Swamp deposits—Brown, bluish-gray, olive-gray, gray, or black muck, mucky peat, 

and organic residues mixed with fine-grained mineral sediment. Soft to dense and 

tough; commonly plastic where moist. Obscure horizontal bedding. Mapped only 

in one area where extensive, northeast of Medicine Lake. Elsewhere included in 

other map units. Thickness 1–3 m 

Dune sand—Yellow, yellowish-brown, olive-brown, grayish-brown, brown, 

brownish-gray, gray, or mottled windblown sand in dunes. Generally calcareous. 

Typically loosely compacted, stratified, well-sorted fine to coarse sand. Faint 

parallel or irregular bedding or pronounced crossbeds; local foreset beds. Chiefly 

subrounded to well-rounded quartz grains; grains are frosted or clear. Typically 

oxidized to depths >1 m; locally stained by iron oxides. In some places, contains 

thin, weakly developed, buried soils (humic horizons). Some dunes are irregular 

hummocks; most are parabolic dunes or elongate blowout dunes. Surface relief 

generally is 2.5–5 m; maximum relief is >10 m. Dunes are mostly stable, with 

grass cover; local blowouts. Includes some eolian sheet sand and flood-plain and 

channel alluvium. Thickness 1–10 m 

Eolian silt and sand—Yellowish-brown, olive-brown, grayish-brown, brownish-gray, 

gray, or mottled windblown silt and sand. Calcareous. Well stratified; well sorted. 

Faint beds or cross-beds. Very friable; slightly hard; subangular blocky structure. 

Not sticky or plastic when moist. Chiefly well-rounded quartz grains; less 

abundant feldspar grains. Quartz grains are frosted or clear. Undulating surface 

topography. Typically oxidized to depths >1.5m. Thickness 1–3 m; 

 maximum >4 m 

Colluvium,2 sheetwash alluvium,1 and glaciofluvial-fill deposits—Complex map 

unit in meltwater channels and lake sluiceways. Channel sides are sharply defined 

to indistinct. Valley sides are chiefly colluvium, sheetwash alluvium, till, and 

bedrock outcrops. Large boulders or lag deposits of cobbles and boulders are 

present on valley sides in some places. Gullies are common locally on valley 

sides. Basal part of fill is generally glaciofluvial sand and gravel (map unit gg) or 

reworked glaciofluvial deposits. Flood-plain and channel alluvium (map unit al) is 

inset into some fill deposits. Flood-plain deposits overlap the fill deposits in some 

places. Sheetwash alluvium (map unit wla) commonly overlaps the fill deposits on 

foot slopes on valley sides; in some places, it mantles most of the fill on the valley 

floor. Mapped in the east central part of the quadrangle. Combined thickness of 

fill and overlapped alluvium is 1–10 m

Colluvium—Yellowish-brown, olive-brown, brown, olive, yellowish-gray, 

brownish-gray, gray, or mottled debris transported and deposited by 

mass-movement processes. Calcareous or noncalcareous. Loose to compact. 

Nonsorted or poorly sorted; nonstratified or faintly stratified. Commonly massive. 

Where derived from glacial deposits, material is typically boulders, cobbles, 

pebbles, and granules of erratic quartzite, limestone, dolomite, and igneous and 

metamorphic rocks and local bedrock in a clayey to sandy matrix. Lignite 

(bedrock) fragments are ubiquitous in most of the colluvium. Thickness 1–5 m

Sheetwash alluvium—Similar to map unit wla. Thickness 1–4 m

Glaciofluvial-fill deposits—See map unit gg. Thickness 0.5–1m 

 HOLOCENE, LATE PLEISTOCENE, AND MIDDLE PLEISTOCENE

Loamy and clayey sheetwash alluvium1

—Pale-yellow, yellowish-brown, 

olive-brown, brown, olive, yellowish-gray, olive-gray, brownish-gray, gray, or 

mottled alluvium transported and deposited by unconfined overland flow and rill 

wash. Typically (1) clay, silty clay, silty clay loam, and clay loam, (2) clay loam, 

silt, silt loam, and sandy loam, or (3) loamy sand and sandy loam. Nonstratified to 

moderately well stratified; poorly to moderately well sorted. Massive, thinly 

laminated, or with weak horizontal bedding. Disseminated organic matter is 

abundant in some areas; local buried soils (humic horizons). Fossiliferous 

(gastropod shells) locally. Fragments of lignite (bedrock) are common. Generally 

calcareous and alkaline; saline in some areas. Clast free, or with scattered granules 

and small pebbles, or with thin beds, pods, and lenses of granule or pebble gravel. 

Commonly interbedded with well-sorted, pebbly, coarse silt and very fine sand. 

Mixed, intercalated, or interbedded with eolian silt and sand (map unit eu) or 

floodplain and channel alluvium (map unit al) in some places. Clayey alluvium is 

soft, sticky, and plastic where moist and tough, hard, and blocky where dry. Clay 

minerals in most areas are dominantly montmorillonite. Granules and pebbles are 

chiefly local clastic sedimentary rocks and, locally, clinker and ironstone; minor 

erratic quartzite, limestone, dolomite, and igneous and metamorphic rocks in 

glaciated areas or areas covered by glacial lakes. Cobbles and boulders are 

generally absent. Sheetwash alluvium is in fans and aprons on foot slopes, in 

glacial diversion channels and sluiceways, in swales and sloughs, and in 

depressions and other poorly drained areas. Included in other map units in many 

areas. Includes some alluvial-fan deposits and inset floodplain and channel 

alluvium (map unit al) deposited by streams. Also includes some colluvium, till, 

and bedrock outcrops. Where sheetwash alluvium directly overlies flood-plain and 

channel alluvium (map unit al) or lake deposits (map units lca, lss), commonly it 

is difficult to distinguish the deposits. Distinction between map units wla and cad

is arbitrary in some areas. Thickness 1–4 m, locally >10 m

QUATERNARY

Loamy colluvium,2 clinker,3 till, and sheetwash alluvium1—Complex map unit in 

the southeastern part of the quadrangle. Yellowish-brown, olive-brown,

Colluvium—Where derived from local bedrock, dominantly angular and sub 

angular fragments of micaceous and bentonitic shale, siltstone, and sandstone in a 

clayey matrix. Where derived from eroded till, pebbles and cobbles are erratic 

quartzite, limestone, dolomite, and igneous and metamorphic rocks. Colluvium

al

agu

lca

lss

hs

ed

eu

cad

wla

 derived from clinker generally is rubble of blocks, boulders, cobbles, pebbles, and 

granules of clinker in a sandy to clayey matrix. Clinker blocks and boulders on the 

surface commonly are nearly covered by lichens. Colluvium derived from 

unaltered bedrock and from other surficial deposits is similar to colluvium in map 

unit cad. Thickness 0.3-1 m

Clinker—Pale-red to dark-red, pink, orange, yellow, green, reddish-brown, gray, 

white, or black sandstone, siltstone, and claystone bedrock that was baked and 

fused during Quaternary time as a result of natural burning of lignite bedrock. 

Intensity of alteration diminishes upward. Lower part is commonly massive and 

contains flow structures; bedding and sedimentary structures of original bedrock 

were destroyed. Contains local slag-like masses with ropy surfaces, or low-density 

rock with fissures, pores, and pockets, resembling scoria. Where the original 

bedrock was clayey, clinker commonly is massive and hard; it breaks into plates or 

brittle chips having conchoidal fracture. Upper part typically retains bedding and 

sedimentary structures of original bedrock; commonly brecciated by collapse 

caused by removal of underlying lignite; flow structures are absent except in 

chimneys that project upward. Polygonal columnar jointing is common in some 

places; breaks in short, columnar fragments or blocks. Clinker is resistant to 

erosion; it forms ledges and rims on slopes or cap rock on hilltops. Burning of 

lignite occurred at different times in different places. Thickness 2–10 m. (See 

“Chronologic Controls”)

Till—The surface till in most places is late Wisconsin in age (map unit tlx). Locally, 

exhumed till of Illinoian and (or) pre-Illinoian age is exposed. In some places till 

was baked and fused with the bedrock when lignite burned, to form "clinkertill" 

(Dove, 1922), or clinkered till. Thickness 0.5–1.5 m. (See “Chronologic 

Controls”)

Sheetwash alluvium—Similar to map unit wla. Thickness 1–4 m

 

QUATERNARY AND TERTIARY

Eolian silt and sand—Blanketlike mantle of wind-blown sediment on Tertiary sand 

and gravel and on residuum overlying the sand and gravel (see map unit xsh) in 

the "driftless area" in the southwest quarter of the quadrangle. Pale-orange, 

pale-yellow, yellowish-brown, olive-brown, grayish-brown, brown, gray, or 

mottled, wind-blown silt (loess) and sand. Typically calcareous; local white or 

pale-gray filaments, powdery interstitial fillings, or nodules of secondary calcium 

carbonate. Generally oxidized throughout. Moderately alkaline. Typically 

consists of (1) loose, nonstratified, well-sorted, homogeneous, massive silt and 

very fine to medium sand or (2) silty fine sand containing laminae or thin lenses of 

silt. Local faint horizontal bedding and crossbedding; vague horizontal color 

banding is common. Friable; blocky structure is common. Nonsticky and 

nonplastic. Chiefly subrounded to well-rounded quartz grains; quartz grains are 

frosted or clear. In some places, includes small fragments of shale and lignite. 

Locally is stained yellowish brown, reddish brown, or brown by iron oxides. In 

some places, contains weakly developed buried soils (humic horizons). Modified 

by bioturbation, cryoturbation, solifluction, and creep. Mostly stable and covered 

by grass. Included in map unit xsh in many places. Thickness 1–3 m 

 Sandy and loamy disintegration residuum4

—Grayish-orange, pale- yellow, 

reddish-brown, yellowish-brown, olive-brown, grayish-brown, brown, 

yellowish-gray, brownish-gray, gray, or mottled loamy sand, sandy clay loam, 

sandy clay, loam, and clay loam. Parent material in most places is weathered 

wind-blown silt and sand residuum that overlies fluvial sand and gravel of Tertiary 

(Miocene and Pliocene?) age. Residuum generally is calcareous; white masses or 

nodules of secondary calcium carbonate are common; cemented by calcium 

carbonate in some places; locally contains carbonate-coated root casts. Generally 

is strongly alkaline. Poorly stratified or nonstratified; poorly sorted or nonsorted. 

Commonly massive; sedimentary structures in parent materials are not preserved. 

Generally compact and moderately indurated. Moderately fissile. Angular or 

subangular blocky structure; minor clay films on ped surfaces. Granular, loose, 

and friable where very sandy. Silty or clayey residuum is slightly sticky to sticky 

and slightly plastic to very plastic when moist; hard when dry. Residuum typically 

is very sandy near base; grades downward to sand and gravel. Scattered, isolated 

granules and pebbles in upper part of residuum, chiefly well-rounded or rounded 

quartzite, argillite, chert, and chert conglomerate, are incorporated into residuum 

by bioturbation. In some places, the long axes of pebbles and small cobbles in 

gravel are aligned vertically, a product of cryoturbation. In some places a buried 

soil is present between the fluvial deposits and the overlying residuum. Multiple 

buried soils are locally present in the residuum; in some places a pedogenic 

composite soil more than 1 m thick is developed in the residuum. Modified by 

bioturbation, cryoturbation, solifluction, and creep. Gullies are common in 

residuum and the underlying sand and gravel in some areas. Map unit includes 

some colluvium; colluvium commonly is exposed along eroded margins of fluvial 

gravel deposits. Thickness of residuum generally 1–3 m

 The underlying sand and gravel on most of the Peerless Plateau is the 

Flaxville formation of Collier and Thom (1918), Whitaker (1980), and Patton 

(1987) and the Wiota gravel of Jensen (1951, 1952), Jensen and Varnes (1964), and 

Colton and others (1989a, b). Those two stratigraphic units are distinguished 

solely on the basis of altitude, not on the basis of lithology or composition. 

Consequently they are informal allostratigraphic units

LATE WISCONSIN

Loamy till—Sediment deposited directly by glacial ice. The informal Crazy Horse 

till of Fullerton and Colton (1986), Fullerton and others (2004a, b; 2007). 

Pale-yellow, grayish-yellow, yellowish-brown, olive-brown, grayish-brown, 

brown, brownish-olive, olive, yellowish-gray, brownish-gray, olive-gray, 

bluish-gray, gray, or mottled calcareous clay loam and loam matrix; in some areas, 

clay, silty clay, silty clay loam, silt loam, sandy clay, or sandy loam. Locally very 

gravelly; where till directly overlies shale bedrock, matrix in some places is >90 

percent shale fragments. In some places, interbedded with, intercalated with, or 

contains lenses, pods, and thin beds of clay, silt, sand, or gravel. Generally 

nonstratified; nonsorted or very poorly sorted. Locally has weak horizontal layers 

where ice margin fluctuated in a lake. Commonly massive; cohesive and friable. 

In some areas, gritty or mealy; crude fissility. Loosely compact or compact, but 

not hard. Sandy till is loose to firm; silty till firm. Clayey till is soft, slightly 

sticky to sticky, and slightly plastic to plastic when moist; hard and blocky when 

dry. Dry till in some places breaks into small angular flakes and plates that have 

sharp edges. Parting is typically irregular or prismatic. Clay minerals are 

dominantly montmorillonite in many areas, dominantly illite or kaolinite locally. 

Widely spaced, weakly developed joints are common; in some places, joint 

surfaces are coated by powdery calcium carbonate or gypsum, or both. Locally 

weakly stained by iron or manganese oxides. Selenite (gypsum) crystals 1–3 mm 

long are present on some joint surfaces. Fragments of lignite (bedrock) are 

ubiquitous in till. Nearly pebble free to very pebbly; cobbles and boulders are rare 

to abundant. Boulders typically are more abundant in till of late Wisconsin age 

than in older subsurface or exhumed tills; also, average diameter of boulders is 

larger than that in older tills. Pebbles are chiefly subangular to rounded erratic 

limestone and dolomite; less abundant quartzite and erratic igneous and 

metamorphic rocks from the Canadian Shield. Where thin and derived from local 

bedrock, pebbles are chiefly angular to subrounded shale, siltstone, and soft 

sandstone; where derived from Tertiary and Quaternary gravel, pebbles are 

dominantly quartzite, argillite, chert, and chert conglomerate. Cobbles and 

boulders are dominantly subangular to well-rounded quartzite and erratic granite, 

pegmatite, gneiss, schist, diorite, and other igneous and metamorphic rocks from 

the Canadian Shield; less abundant erratic limestone and dolomite from Canada. 

Largest erratic boulders are >2 m in diameter. Clasts of older till and clasts of 

lignite (bedrock) as large as 2 m in diameter are locally present in till. 

Glaciotectonic blocks or rafts of shale tens or hundreds of meters in length are 

locally present in till. Generally unstable; moves by creep on hillslopes; slumps in 

exposures. Thin and discontinuous in some areas; includes exhumed till of 

Illinoian and (or) pre-Illinoian age that is exposed at the surface. Includes some 

unmapped glaciotectonic deposits (symbol IT), flowtill, and landslide deposits. 

Includes areas of till modified by waves and currents in glacial lakes, mantled by a 

thin surface litter of cobbles and boulders or a discontinuous cover of lake clay, 

silt, sand, and gravel (map units lca, lss). Includes some lake delta deposits, lake 

density-current underflow-fan deposits, outwash and ice-contact sand and gravel 

(map units gg, kg), flood-plain and channel alluvium (map unit al), and bedrock 

outcrops. Locally overlain by sheetwash alluvium (map unit wla), lake clay, silt 

and sand (map units lca, lss), eolian sand and silt (map units ed, eu), or swamp 

deposits (map unit hs)

Ground-moraine deposits—Integrated drainage; flat, rolling, or undulating surface 

topography. Includes collapsed supraglacial sediment (stagnation moraine 

deposits) having <3 m of relief. Includes till in minor moraines. Maximum slope 

angles are generally less than 4°. Thickness 0.5–2 m; maximum thickness >10 m

End-moraine deposits—Broad, long belts of hummocky or undulating ridges or 

belts of narrow, discontinuous, sharply defined ridges oriented parallel to vanished 

ice margins. Closed depressions and lag cobbles and boulders are common on 

some surfaces. Relief in some places is >20 m. Till end moraine deposits locally 

grade laterally into kame-moraine deposits (map unit ke) that are included in the 

unit. In some areas, boundaries between end-moraine deposits and 

stagnation-moraine or ground-moraine deposits are transitional, and contacts are 

arbitrary. Thickness 6–20 m, locally >30 m 

Stagnation-moraine deposits—Broad areas of hummocky or knob-and-kettle 

collapsed topography lacking distinct, continuous ridges that are oriented parallel 

to vanished ice margins. Nonintegrated or poorly integrated drainage; ephemeral 

ponds and depressions are common. Ice-block depressions (kettles) are common 

in many areas. Relief is >3 m; locally >40 m. Slope angles are generally less than 

4°. Includes collapsed glacial sediment (till and flowtill), ice-walled and collapsed 

supraglacial lake clay, silt, sand, and gravel map units (lca, lss), and collapsed 

outwash and ice-contact sand and gravel (map units gg, kg). Glacial, 

glaciolacustrine, glaciofluvial, and alluvial sediments were redeposited by mass 

movement (flow and sliding) as a result of melting of buried ice for several 

thousand years after initial deglaciation. In some areas, boundaries between 

stagnation-moraine deposits and ground-moraine or end-moraine deposits are 

transitional, and contacts are arbitrary. Thickness 6–20 m 

Kame-moraine deposits—Ice-contact gravel, sand, and minor silt similar to map 

unit kg (description of kg applies). Broad, gently sloping ridges or aligned 

hummocks and hills (kames) of sand and gravel separated by other deposits. Local 

relief is generally 5–10 m, locally 30 m. Sand and gravel in some places grades 

laterally into till (map unit tlx) that is included in the map unit. In some places, 

deposits were modified by waves and currents in glacial lakes; ice-block 

depressions (kettles) are common where deposits were not modified. Locally 

includes outwash sand and gravel (map unit gg). Thickness 2–15 m, 

 locally >30 m

Ice-contact sand and gravel—Sediment deposited on or against glacial ice; sediment 

collapsed when ice subsequently melted. Pale-yellow, brownish-yellow, 

grayish-yellow, reddish-brown, yellowish-brown, olive-brown, grayish-brown, 

brown, olive, yellowish-gray, olive-gray, brownish-gray, gray, or mottled, 

calcareous sand and gravel and minor silt. Textures vary abruptly, laterally and 

vertically. Locally, unit is dominantly boulder or cobble gravel; in some places, it 

is pebbly silt and fine sand. Sand and gravel commonly is interbedded with or 

contains lenses, inclusions, or clasts of clay, silt, till, or flowtill. Poorly to well 

sorted; poorly to well stratified; irregularly bedded to well bedded; beds are 

discontinuous laterally. Faults, folds, and slump and collapse tructures are 

common. Gravel is locally cemented by iron oxides or secondary calcium 

carbonate in zones; intense iron-oxide stains on some clasts. Clasts are angular to 

well rounded; composition is similar to that of clasts in associated till. Typically, 

shale clasts are much less abundant than in associated till; resistant erratic clasts 

are more abundant. Fragments of lignite (bedrock) are common in many areas. 

Topography is typically hummocky to knobby, or forms isolated mounds or hills; 

in some places, hills are irregular in shape. The ground surface is locally flat.

ckq

eux

xsh

tlx

tlx(e)

tlx(s)

ke

 Commonly pitted with ice-block depressions (kettles). Boulder litters locally are 

present on surface. Local surface relief is generally 3–15 m, locally >20 m. In 

some places, deposits were modified by waves and currents in lakes; ice-contact 

deposits are overlain by discontinuous lake clay, silt, sand, and gravel (map units 

lca, lss). Distinguished from kame-moraine deposits (map unit ke) arbitrarily in 

some areas. Included in outwash sand and gravel (map unit gg) in some places. 

Includes some kame-moraine deposits (map unit ke), kame-delta deposits, and 

lake-delta deposits . Also includes some outwash sand and gravel (map unit gg), 

lake clay, silt, sand, and gravel (map units lca, lss), inset flood-plain and channel 

alluvium (map unit al), till (map unit tlx), glaciotectonic deposits (symbol IT), and 

bedrock outcrops. Locally overlain by till or flowtill as thick as 5 m. Thickness 

1–10 m, locally >30 m

Outwash sand and gravel—Sediment deposited by meltwater streams. Pale-yellow, 

brownish-yellow, grayish-yellow, reddish-brown, yellowish-brown, olive-brown, 

grayish-brown, brown, olive, yellowish-gray, brownish-gray, olive-gray, gray, or 

mottled, calcareous sand, pebbly sand, and gravel; locally the deposit is pebbly 

sand and silt. Poorly to well sorted; poorly to well stratified. Stratification 

typically is (1) horizontal beds of well-sorted sand, (2) pebbly sand with 

ripple-drift, cut-and-fill, planar, or trough crossbeds, or (3) interbedded pebbly 

sand and pebble, cobble, or boulder gravel. Local lenses or beds of silt and clay; 

local boulder beds; local clasts or blocks of till or flowtill. Textures generally 

coarsen in downstream direction in valley train deposits. Clasts are subangular to 

very well rounded; size of largest clasts generally decreases in downstream 

direction in valley train deposits. Clast composition is generally similar to that of 

local till; locally dominantly shale or dominantly redeposited quartzite, argillite, 

chert, and chert conglomerate derived from Tertiary gravel and early and middle 

Pleistocene gravel. Boulders and large cobbles are dominantly subangular to 

subrounded, reworked glacial erratics (limestone, dolomite, granite, pegmatite, 

gneiss, schist, diorite, and other igneous and metamorphic rocks). Fragments of 

lignite (bedrock) are abundant in many areas. Clasts in some places are intensely 

stained by iron oxides or manganese oxides; gravel is locally cemented by 

secondary calcium carbonate. Present beneath outwash plains, as valley trains, in 

fans and aprons, beneath terrace remnants, as delta topset beds, and as melt-water 

channel fills. Ground surfaces are smooth, undulating, or gently rolling; locally 

pitted with ice-block depressions (kettles). Some surfaces are marked by braided 

or anastomosing channel scars. In some places, includes some till (map unit tlx), 

ice-contact sand and gravel (map unit kg), lake-delta deposits, inset flood-plain 

and channel alluvium (map unit al), or bedrock outcrops. In some areas, deposits 

were modified by waves and currents in lakes, and the outwash sand and gravel is 

overlain by lake clay, silt, sand, and gravel (map units lca, lss). Locally overlain 

by eolian silt and sand (map units ed, eu), or swamp deposits (map unit hs). 

Thickness 1–6 m, locally >15 m

 Some of the sand and gravel mapped as outwash possibly is early 

postglacial alluvium. Precipitation and runoff were greater than at present for 

several thousand years after initial deglaciation, and glacial, ice-contact, 

glaciofluvial, and glaciolacustrine sediments were eroded and redeposited as 

alluvial fills. The surface morphology, lithology, and sedimentary structures of the 

deglacial outwash and early postglacial alluvium are similar, and the deposits have 

not been distinguished on published maps

Beach deposits—Pale-yellow, yellowish-brown, yellowish-gray, brownish-gray, or 

mottled sand and pebbly sand beach deposits of glacial Lake Four Buttes west of 

Scobey in northwest part of quadrangle. Stratified or non-stratified; poorly to 

moderately well sorted. Occasional cobbles or small boulders. Pebbles and 

granules are dominantly quartzite, chert, and chert conglomerate that was 

reworked from Tertiary gravel (see map unit xsh); some ice-rafted erratic 

limestone, dolomite, and igneous and metamorphic rocks and local sandstone. 

Cobbles and boulders are erratic quartzite, igneous and metamorphic rocks, and 

limestone and dolomite. Clasts generally are rounded or well rounded. Calcareous 

or non-calcareous. Generally loose; local secondary calcium carbonate 

cementation. Thickness 0.5–2 m

ILLINOIAN

Loamy or sandy loamy till—Sediment deposited directly by glacial ice. Markles 

Point till and Kisler Butte till of Fullerton and Colton (1986) and Fullerton and 

others (2004a, b; 2007) Pale-yellow, grayish-yellow, yellowish-brown, olivebrown, grayish-brown, brown, brownish-olive, olive, yellowish-gray, 

brownish-gray, olive-gray, gray, or mottled clay loam, loam, or sandy loam matrix; 

in some areas, silty clay loam, sandy clay, or sandy clay loam. Generally 

nonstratified; nonsorted or very poorly sorted. In some places, interbedded with, 

or contains lenses, pods, and stringers of, clay, silt, sand, or gravel. Weak 

horizontal layers are present locally where an ice margin fluctuated in a lake. 

Commonly massive; cohesive and friable. Crudely fissile. Generally compact or 

very compact; resists penetration by pick or shovel when dry. Clayey till is 

slightly sticky to very sticky and slightly plastic to plastic when moist, hard and 

blocky when dry. Dry till in some places breaks into small, irregular pieces; 

commonly it breaks through granules and small pebbles. Parting is typically 

crudely irregular or prismatic. Platy structure is present locally. Clay minerals are 

dominantly montmorillonite in many areas, dominantly illite or kaolinite locally. 

Widely spaced polygonal joints in some areas. In some places, joint surfaces are 

coated by seams of secondary calcium carbonate, or by powdery calcium 

carbonate or gypsum. Selenite (gypsum) crystals 1–4 mm long, or clusters or 

crusts of crystals are present on some joint surfaces. Stains, flecks, or scales of 

iron and manganese oxides are common on joint and parting surfaces. Fragments 

of lignite (bedrock) are common. Generally oxidized throughout where thin. 

Nearly pebble free to very pebbly; cobbles and boulders are rare to abundant. 

Clasts in many areas are dominantly granules and pebbles. Boulders in general are 

less abundant in till of Illinoian age (map unit tks) than in till of late Wisconsin age 

(map unit tlx). Pebbles are dominantly subangular to rounded quartzite and erratic 

limestone and dolomite; igneous and metamorphic rocks from the Canadian Shield 

are less abundant. Where till is thin and derived primarily from local bedrock, 

pebbles are chiefly subangular to subrounded shale, siltstone, and soft sandstone; 

where derived from Tertiary or Quaternary gravel, pebbles are dominantly 

quartzite, argillite, chert, and chert conglomerate. Cobbles and boulders are 

dominantly subangular to well-rounded quartzite and erratic granite, pegmatite, 

gneiss, schist, diorite, and other igneous and metamorphic rocks from the Canadian 

Shield; erratic limestone and dolomite cobbles and boulders are less abundant. 

Largest erratic limestone and dolomite cobbles and boulders are less abundant. 

Largest erratic boulders are >2 m in diameter. Clasts of till of pre-Illinoian age and 

clasts of lignite (bedrock) are locally included in the till. Integrated drainage; flat, 

rolling, or undulating surface topography. Maximum slope angles are <4°. 

Includes minor moraines or washboard moraines that are conspicuous only when 

viewed from the air (shown by a symbol on the map). Generally stable on 

hillslopes; till in natural exposures (such as stream cuts) and artificial excavations 

does not slump readily. Thin and discontinuous in some areas; generally is a thin 

veneer over older deposits and bedrock. Gullies are common on hillslopes. 

Surface is intensely deflated in some places. Discontinuous lag deposits of 

granules and pebbles are common on till surfaces; lag cobbles and boulders are 

widely scattered on till surfaces and on bedrock surfaces. Map unit includes some 

exhumed till of pre-Illinoian age that is exposed at the surface. Includes some 

outwash sand and gravel (map unit ggi), flood-plain and channel alluvium (map 

unit al ), Tertiary and Quaternary nonglacial sand and gravel (see map unit xsh), 

and bedrock outcrops. Locally overlain by sheetwash alluvium (map unit wla), 

eolian silt and sand (map unit eux), or unmapped lake deposits of Illinoian age and 

(or) late Wisconsin age. Thickness 0.3–3 m; maximum thickness >10 m 

Outwash sand and gravel—Sediment deposited in meltwater streams. Pale-yellow, 

brownish-yellow, reddish-brown, yellowish-brown, olive-brown, grayish-brown, 

brown, olive, or mottled, calcareous or noncalcareous, coarse sand, pebbly sand, 

and gravel. Poorly to well sorted; poorly to well stratified. Typically is 

interbedded pebbly sand and pebble, cobble, or boulder gravel. Lenses of silt and 

clay are present locally; local boulder beds. Clasts are subangular to very well 

rounded. Clast composition generally is similar to that of till in the same area; 

locally, dominantly redeposited quartzite, argillite, chert, and chert conglomerate 

derived from gravel of Tertiary to early Pleistocene age (see map unit xsh). 

Boulders and large cobbles are dominantly subangular to well rounded, reworked 

glacial erratics (quartzite; limestone and dolomite; granite, pegmatite, gneiss, 

schist, diorite, and other igneous and metamorphic rocks). Clasts in some places 

are stained by iron and manganese oxides. Mapped deposits are fills in melt-water 

channels. Distinction between outwash sand and gravel (map unit ggi) and 

colluvium, sheetwash alluvium, and glaciofluvial-fill deposits (map unit cad ) is 

arbitrary in some areas because exposures on the channel floors are lacking. 

Ground surfaces are smooth or undulating. Includes some till (map unit tks) , inset 

flood-plain and channel alluvium (map unit al), colluvium, and bedrock outcrops. 

Commonly overlain by sheetwash alluvium (map unit wla) or eolian silt and sand 

(map unit eux). Thickness 1–4 m, locally >6 m

PRE-ILLINOIAN MIDDLE PLEISTOCENE

Lake silt and sand—Sprole Silt of Colton (1963a, f), exposed locally between Poplar 

and Brockton. Pale-yellow, yellowish-brown, grayish-brown, yellowish-gray, 

brownish-gray, gray, or mottled, generally calcareous silt, sand, and clay. 

Generally well sorted; moderately well stratified to well stratified. Lignite 

(bedrock) fragments are common. Lower part is dominantly thin-bedded or 

laminated silt and clay containing scattered granules and pebbles; in some places it 

is silt and sand interbedded or intercalated with bedded or laminated silt and fine 

sand. Upper part is typically weakly bedded or massive silt and fine or medium 

sand containing scattered dropstone granules, pebbles, and small cobbles. Locally 

deformed into folds by overriding ice. Clasts are dominantly redeposited quartzite, 

argillite, chert, and and chert conglomerate from gravel of Tertiary to middle 

Pleistocene age (see map unit xsh); includes rare rafted erratic igneous and 

metamorphic rocks from the Canadian Shield or erratic limestone or dolomite. 

Poorly exposed. Lake sediment overlies bedrock or Wiota gravel (early and 

middle Pleistocene?) and is overlain by Archer till of middle Pleistocene age. 

Thickness 10–20 m, locally 30 m 

 The sediment was deposited in the (now buried) bedrock valley of the 

ancestral Missouri River (shown by a symbol on the map). It was deposited in a 

lake that was dammed in the paleovalley during the earliest middle Pleistocene 

glaciation in the Poplar-Brockton area, when the ice sheet blocked the ancestral 

valleys of the Missouri and Yellowstone Rivers (Fullerton and others, 2004a, b). 

At its maximum extent, the lake possibly was 95 km long and 17 km wide. 

Damming of the lake caused the initial diversion of the Missouri and Yellowstone 

Rivers eastward through the Charbonneau Sag in North Dakota (in the Watford 

City 1° × 2° quadrangle southeast of this quadrangle). A lake in the Yellowstone 

River valley was contemporaneous (and, at least briefly, confluent) with the lake in 

the Missouri River valley. The basal lake sediments in the Yellowstone Valley and 

the overlying pre-Illinoian Archer till (Fullerton and Colton, 1986), Fullerton and 

others (2004a, b; 2007) in the Glendive quadrangle have normal remanant 

geomagnetic polarity, indicating that they are younger than 778 ka, the age of the 

Matuyama-Brunhes geomagnetic reversal (Fullerton and others, 2004a, b)

PRE-QUATERNARY

Bedrock

1

Sheetwash alluvium, for purposes of this map, is material that was transported and deposited 

by unconfined flowing water, chiefly sheet flow and rill wash. 2

Colluvium, for purposes of this map, is material that was transported and deposited by slow 

mass-movement processes, chiefly creep. 3

Clinker is bedrock that was baked and fused in Quaternary time as a result of natural burning 

of lignite beds (see map unit ckq). The term here is not applied to surficial 

deposits and materials that were baked and fused as a result of natural burning of 

lignite beds. Glacial till that was altered here is referred to as clinkered till (see 

“CHRONOLOGIC CONTROLS”). 4

Disintegration residuum, for purposes of this map, is material that was derived primarily from 

in-place mechanical disaggregation of clastic bedrock or other materials, with no 

appreciable lateral transport. Where the residuum is thin, pedogenic soils may 

extend through the residuum to bedrock 

gg

lb

tks

ggi

lle

R

SOURCES OF INFORMATION

MONTANA

Alden, W.C., 1924, Physiographic development of the northern Great Plains: Geological 

Society of America Bulletin, v. 35, p. 385–423.

Alden, W.C., 1932, Physiography and glacial geology of eastern Montana and adjacent areas: 

U.S. Geological Survey Professional Paper 174, 133 p.

Bauer, C.M., 1915, A sketch of the late Tertiary history of the upper Missouri River: Journal of 

Geology, v. 23, p. 52–58.

Bergantino, R.N., 1984, Topographic map of the bedrock surface, northeastern Montana, 

northwestern North Dakota, and southeastern Saskatchewan: Montana Bureau of 

Mines and Geology Open-File Report MBMG 151, scale 1:250,000.

Bretz, J H., 1943, Keewatin end moraines in Alberta, Canada: Geological Society of America 

Bulletin, v. 54, p. 31–52.

Christiansen, E.A., 1979, The Wisconsinan deglaciation of southern Saskatchewan and adjacent 

areas: Canadian Journal of Earth Sciences, v. 16, p. 913–938.

Clayton, Lee, and Moran, S.R., 1982, Chronology of late Wisconsinan glaciation in middle 

North America: Quaternary Science Reviews, v. 1, p. 55–82.

Coates, D.A., and Heffern, E.L., 2000, Origin and geomorphology of clinker in the Powder 

River Basin, Wyoming and Montana, in Miller, R., ed., Coal bed methane and Tertiary 

geology of the Powder River Basin: Wyoming Geological Association, Guidebook, 

50th annual field conference, p. 211–229.

Collier, A.J., 1919, Geology of northeastern Montana: U.S. Geological Survey Professional 

Paper 120–B, p. 17–39.

Collier, A.J., and Thom, W.T., Jr., 1918, The Flaxville gravel and its relation to other terrace 

gravels of the northern Great Plains: U.S. Geological Survey Professional Paper 108–J, 

p. 179–184.

Colton, R.B., 1951, Geology of the Oswego quadrangle, Montana: U.S. Geological Survey 

Open-File Report 101, 45 p.

Colton, R.B., 1951, Geology of the Otter Creek quadrangle, Montana: U.S. Geological Survey 

Open-File Report, 32 p.

Colton, R.B., 1955, Geology of the Wolf Point quadrangle, Montana: U.S. Geological Survey 

Geologic Quadrangle Map GQ–67, scale 1:62,500.

Colton, R.B., 1958, Ice-crack moraines in northwestern North Dakota and northeastern 

Montana, in Guidebook, Ninth Annual Field Conference, Mid-Western Friends of the 

Pleistocene: North Dakota Geological Survey Miscellaneous Series 10, p. 99–107.

Colton, R.B., 1962, Geology of the Otter Creek quadrangle, Montana: U.S. Geological Survey 

Bulletin 1111–G, p. 237–288.

Colton, R.B., 1963a, Geologic map of the Brockton quadrangle, Roosevelt and Richland 

Counties, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations 

Map I–362, scale 1:62,500.

Colton, R.B., 1963b, Geologic map of the Chelsea quadrangle, Roosevelt and McCone 

Counties, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations 

Map I–363, scale 1:62,500. 

Colton, R.B., 1963c, Geologic map of the Cuskers quadrangle, Roosevelt County, Montana: 

U.S. Geological Survey Miscellaneous Geologic Investigations Map I–364, scale 

1:62,500.

Colton, R.B., 1963d, Geologic map of the Hay Creek quadrangle, Roosevelt County, Montana: 

U.S. Geological Survey Miscellaneous Geologic Investigations Map I–365, scale 

1:62,500.

Colton, R.B., 1963e, Geologic map of the Oswego quadrangle, Valley, Roosevelt, and McCone 

Counties, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations 

Map I–366, scale 1:62,500.

Colton, R.B., 1963f, Geologic map of the Poplar quadrangle, Roosevelt, Richland, and 

McCone Counties, Montana: U.S. Geological Survey Miscellaneous Geologic 

Investigations Map I–367, scale 1:62,500.

Colton, R.B., 1963g, Geologic map of the Porcupine Valley quadrangle, Valley County, 

Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map I–368, 

scale 1:62,500.

Colton, R.B., 1963h, Geologic map of the Spring Creek quadrangle, Valley County, Montana: 

U.S. Geological Survey Miscellaneous Geologic Investigations Map I–369, scale 

1:62,500.

Colton, R.B., 1963i, Geologic map of the Todd Lakes quadrangle, Valley and Roosevelt 

Counties, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations 

Map I–370, scale 1:62,500.

Colton, R.B., 1963j, Geologic map of the Tule Valley quadrangle, Roosevelt County, Montana: 

U.S. Geological Survey Miscellaneous Geologic Investigations Map I–371, scale 

1:62,500.

Colton, R.B., 1964, Geologic map of the south half of the Baylor, Larslan, West Fork, Police 

Creek, Kahle, and Lundville quadrangles, Valley, Roosevelt, and Daniels Counties, 

Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map I–361, 

scale 1:62,500.

Colton, R.B., 1979a, Geologic map of the Bainville SW quadrangle, Roosevelt and Richland 

Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map 

MF–1110, scale 1:24,000.

Colton, R.B., 1979b, Geologic map of the Three Buttes quadrangle, Richland and Roosevelt 

Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map 

MF–1111 scale 1:24,000.

Colton, R.B., 1979c, Geologic map of the Bainville SE quadrangle, Roosevelt and Richland 

Counties, Montana, and Williams County, North Dakota: U.S. Geological Survey 

Miscellaneous Field Studies Map MF–1112, scale 1:24,000.

Colton, R.B., 1979d, Geologic map of the Dugout Creek quadrangle, Richland and Roosevelt 

Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map 

MF–1113, scale 1:24,000.

Colton, R.B., 1982a, Geologic map of the Twomile Creek quadrangle, Richland and Roosevelt 

Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map 

MF–1413, scale 1:24,000.

Colton, R.B., 1982b, Geologic map of the Cedar Coulee quadrangle, Roosevelt and Richland 

Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map 

MF–1414, scale 1:24,000.

Colton, R.B., and Bateman, A.F., Jr., 1956a, The Brockton-Froid fault zone in northeastern 

Montana [abs.]: Geological Society of America Bulletin, v. 67, no. 12, pt. 2, p. 1792.

Colton, R.B., and Bateman. A.F., Jr., 1956b, Geologic and structure contour map of the Fort 

Peck Indian Reservation and vicinity, Montana: U.S. Geological Survey Miscellaneous 

Geological Investigations Map I–225, scale 1:125,000.

Colton, R.B., Fullerton, D.S., and Ehler, W.C., 2006, Geologic map of the Culbertson 30' × 60' 

quadrangle (surficial emphasis), Roosevelt, McCone, and Richland Counties, Montana, 

and Divide and Williams Counties, North Dakota: Montana Bureau of Mines and 

Geology Open-File Report 539, 44 p., scale 1:100,000.

Colton, R.B., Fullerton, D.S., Ehler, W.C., Whitaker, S.T., and Ellis, M.S., 2006, Geologic map 

of the Plentywood 30' × 60' quadrangle (surficial emphasis), Sheridan, Roosevelt, and 

Daniels Counties, Montana, and Divide and Williams Counties, North Dakota: 

Montana Bureau of Mines and Geology Open-File Report 540, 32 p., scale 1:100,000.

Colton, R.B., Fullerton, D.S., Ehler, W.C., Whitaker, S.T., and Ellis, M.S., 2006, Geologic map 

of the Scobey 30' × 60' quadrangle (surficial emphasis), Daniels, Roosevelt, McCone 

and Valley Counties, Montana: Montana Bureau of Mines and Geology Open-File 

Report 541, 40 p., scale 1:100,000.

Colton, R.B., Fullerton, D.S., Jarvis, B., Ehler, W.C. and Ellis, M.S., 2006, Geologic map of the 

Wolf Point 30' × 60' quadrangle (surficial emphasis), Roosevelt, McCone, Valley, and 

Richland Counties, Montana: Montana Bureau of Mines and Geology Open-File 

Report 542, 49 p., scale 1:100,000.

Colton, R.B., and Jensen, F.S., 1953, Crevasse fillings on the glaciated plains, northeastern 

Montana [abs.]: Geological Society of America Bulletin, v. 64, no. 12, pt. 2, p. 

1542–1543.

Colton, R.B., Lemke, R.W., and Lindvall, R. M., 1961, Glacial map of Montana east of the 

Rocky Mountains: U.S. Geological Survey Geologic Investigations Map I–327, scale 

1:500,000.

Colton, R.B., Naeser, N.D., and Naeser, C.W., 1986, Drainage changes in eastern Montana and 

western North Dakota during late Cenozoic time: Geological Society of America 

Abstracts with Programs, v. 18, no. 5, p. 347.

Colton, R.B., Whitaker, S.T., Ehler, W.C., and Fuller, H.K., 1978, Preliminary photogeologic 

map of the Four Buttes, Scobey, and Flaxville quadrangles, Daniels County, Montana: 

U.S. Geological Survey Open-File Report 78–898, scale 1:50,000

Colton, R.B., Whitaker, S.T., and Ehler, W.C., 1989a, Geologic map of the Glasgow 1° × 30' 

quadrangle, Valley and McCone Counties, Montana: U.S. Geological Survey 

Open-File Report 89–17l, 13 p

Colton, R.B., Whitaker, S.T., and Ehler, W.C., 1989b, Geologic map of the Opheim 1° × 30' 

quadrangle, Valley and Daniels Counties, Montana: U.S. Geological Survey Open-File 

Report 89–319, 10 p.

Crone, A.J., and Wheeler, R.L., 2000, Data for Quaternary faults, liquifaction features, and 

possible tectonic features in the Central and Eastern United States, east of the Rocky 

Mountains: U.S. Geological Survey Open-File Report 00–260, 332 p. (available at 

http://greenwood.cr.usgs.gov/pub/open-file-reports/ofr-00-0260/).

DeYoung, William, Youngs, F.O., and Glassey, T.W., 1932, Soil survey of the Milk River area, 

Montana: U.S. Department of Agriculture, Bureau of Chemistry and Soils, Series 1928, 

no. 22, 35 p.

Donovan, J.J., 1989, Groundwater and geologic data for northeastern Montana in the Wolf 

Point 1° × 2° quadrangle: Montana Bureau of Mines and Geology Open-File Report 

208, 638 p. 

Donovan, J.J., and Bergantino, R.N., 1987, Groundwater resources of the Fort Peck Indian 

Reservation, with emphasis on aquifers of the preglacial Missouri River valley: 

Montana Bureau of Mines and Geology Open-File Report MBMG 178, 41 p.

Edwards, G.J., 1951, A preliminary report on the electrical resistivity survey at Medicine Lake, 

Montana: U.S. Geological Survey Circular 97, 16 p.

Feltis, R.D., 1979, Water resources of shallow aquifers in the upper Poplar River basin, 

northeastern Montana: U.S. Geological Survey Water-Resources Investigations 

WRI–79–5l, 23 p.

Fullerton, D.S., Christiansen, E.A., Schreiner, B.T., Colton, R.B., and Clayton, Lee, 2007, 

Quaternary geologic map of the Regina 4° × 6° quadrangle, United States and Canada: 

U.S. Geological Survey Miscellaneous Investigations Series Map I–1420 (NM–13), 37 

p., scale 1:1,000,000.

Fullerton, D.S., and Colton, R.B., 1986, Stratigraphy and correlation of the glacial deposits on 

the Montana Plains, in Richmond, G.M., and Fullerton, D.S., eds., Quaternary 

glaciations in the United States of America: Quaternary Science Reviews, v. 5, p. 

69–82.

Fullerton, D.S., Colton, R.B., and Bush, C.A., 2004a, Limits of mountain and continental 

glaciations east of the Continental Divide in northern Montana and northwestern North 

Dakota, U.S.A., in Ehlers, Jurgen, and Gibbard, P.L., eds., Major Quaternary 

glaciations—Extent, timing, and global synchroneity, v. 2, North America: Amsterdam, 

Elsevier, p. 123–143.

Fullerton, D.S., Colton, R.B., Bush, C.A., and Straub, A.W., 2004b, Map showing spatial and 

temporal relations of mountain and continental glaciations on the Northern Plains in 

northern Montana and northwestern North Dakota: U.S. Geological Survey 

Miscellaneous Investigations Series Map SIM–2843, 36 p., scale 1:1,000,000.

Fullerton, D.S., Colton, R.B., and Bush, C.A., 2012a, Quaternary geologic map of the Havre 1° 

× 2° quadrangle, Montana: U.S. Geological Survey Open-File Report 2012–1028, scale 

1:250,000.

Fullerton, D.S., Colton, R.B., and Bush, C.A., 2012b, Quaternary geologic map of the Shelby 

1° × 2° quadrangle, Montana: U.S. Geological Survey Open-File Report 2012–1170, 

scale 1:250,000.

Fullerton, D.S., Colton, R.B., and Bush, C.A., 2012c, Quaternary geologic map of the Glasgow 

1° × 2° quadrangle, Montana: U.S. Geological Survey Open-File Report 2012–1217, 

scale 1:250,000.

Giesecker, L.F., Morris, E.R., Strahorn, A.T., and Manifold, C.B., 1933, Soil survey 

(reconnaissance) of the Northern Plains of Montana: U.S. Department of Agriculture, 

Bureau of Chemistry and Soils, Series 1929, no. 21, 74 p.

Gott, G.B., Witkind, I.J., Hansen, W.R., Lindvall, R.M., Prouty, C.E., Smith, J.H., Basile, R.E., 

and Kaye, C.A., 1959, Geologic map of the Smoke Creek-Medicine Lake-Grenora area, 

Montana and North Dakota, in Witkind, I.J., Quaternary geology of the Smoke 

Creek-Medicine Lake-Grenora area, Montana and North Dakota: U.S. Geological 

Survey Bulletin 1073, 2 sheets, scale 1:62,500.

Heffern, E.L., and Coates, D.A., 2004, Geologic history of natural coal-bed fires, Powder River 

Basin, USA, in Stracher, G.B., ed., Coal fires burning around the world—A global 

catastrophe: International Journal of Coal Geology, v. 59, p. 25–47.

Heffern, E.L., Reiners, P.W., Naeser, C.W., and Coates, D.A., 2007, Geochronology of clinker 

and implications for evolution of the Powder River Basin landscape, Wyoming and 

Montana, in Stracher, G.B., ed., Geology of coal fires-Case studies from around the 

world: Geological Society of America Reviews in Engineering Geology, v. XVIII, p. 

155–175.

Hill, C.L., 2006, Stratigraphic and geologic contexts of mammoth (Pleistocene fauna, upper 

Missouri River Basin (northern Great Plains and Rocky Mountains), U.S.A.: 

Quaternary International, v. 142–143, p. 87–106.

Hopkins, W.B., and Tilstra, J.R., 1966, Availability of ground water from the alluvium along 

the Missouri River in northeastern Montana: U.S. Geological Survey Hydrologic 

Investigations Atlas HA–224, 13 p.

Howard, A.D., 1956, Till-pebble isopleth maps of parts of Montana and North Dakota: 

Geological Society of America Bulletin, v. 67, p. 1191–1206.

Howard, A.D., 1958, Drainage evolution in northeastern Montana and northwestern North 

Dakota: Geological Society of America Bulletin, v. 69, p. 575–588.

Howard, A.D., 1960, Cenozoic history of northeastern Montana and northwestern North 

Dakota, with emphasis on the Pleistocene: U.S. Geological Survey Professional Paper 

326, 107 p.

Izett, G.A., and Wilcox, R.E., 1982, Map showing localities and inferred distributions of the 

Huckleberry Ridge, Mesa Falls, and Lava Creek ash beds (Pearlette family ash beds) of 

Pliocene and Pleistocene age in the western United States and southern Canada: U.S. 

Geological Survey Miscellaneous Investigations Series Map I–1325, scale 1:4,000,000.

Jensen, F.S., 1951, Preliminary report on the geology of the Frazer quadrangle, Montana: U.S. 

Geological Survey Open-File Report 51–37, 29 p.

Jensen, F.S., 1952, Preliminary Report on the geology of the Nashua quadrangle, Montana: 

U.S. Geological Survey Open-File Report 52–82, 37 p.

Jensen, F.S., and Varnes, H.D., 1964, Geology of the Fort Peck area, Garfield, McCone, and 

Valley Counties, Montana: U.S. Geological Survey Professional Paper 414–F, p. 

F1–F49.

Lanphere, M.A., Champion, D.E., Christiansen, R.L., Izett, G.A., and Obradovich, J.D., 2002, 

Revised ages for tuffs of the Yellowstone Plateau volcanic field—Assignment of the 

Huckleberry Ridge Tuff to a new geomagnetic polarity event: Geological Society of 

America Bulletin, v. 114, p. 559–568.

Lemke, R.W., Laird, W.M., Tipton, M.J., and Lindvall, R.M., 1965, Quaternary geology of the 

northern Great Plains, in Wright, H.E., Jr., and Frey, D.G., eds., The Quaternary of the 

United States: Princeton, N.J., Princeton University Press, p. 15–27.

Levings, G.W., 1986, Preliminary appraisal of ground water in and near the ancestral Missouri 

River valley, northeastern Montana: U.S. Geological Survey Water-Resources 

Investigations Report 86–4138, 41 p.

Mickelson, D.M., Clayton, Lee, Fullerton, D.S., and Borns, H.W., Jr., 1983, The late Wisconsin 

glacial record of the Laurentide ice sheet in the United States, in Porter, S.C., ed., 

Late-Quaternary environments of the United States, v. 1, the late Pleistocene: 

Minneapolis, University of Minnesota Press, p. 3–37.

Montagne, Clifford, Munn, L.C., Nielsen, G.A., Rogers, J.W., and Hunter, H.E., 1982, Soils of 

Montana: Montana Agricultural Experiment Station Bulletin 744, 95 p.

Moran, S.R., and Clayton, Lee, 1984, Chronology of late Wisconsinan glaciation in middle 

North America—Reply to the comments of R.W. Klassen: Quaternary Science 

Reviews, v. 3, no. 2/3, p. i–vi.

Patton, T.W., 1987, Quaternary and Tertiary geology of the Turner-Hogeland Plateau, 

north-central Montana: Bozeman, Montana College of Mineral Science and 

Technology, M.S. thesis, 175 p.

Prichard, G.E., and Landis, E.R., 1955, Geology of the northern part of the Girard coal field, 

Richland County, Montana: U.S. Geological Survey Coal Investigations Map C–24, 

map scale 1:48,000.

Prichard, G.E., and Landis, E.R., 1975, Coal resources and Cenozoic geology of the Girard 

coal field, Richland County, Montana: U.S. Geological Survey Bulletin 1310. 

 

Rogers, G.S., 1917, Baked shale and slag formed by the burning of coal beds: U.S. Geological 

Survey Professional Paper 108–A, p. 1–10.

Simonson, G.H., Rogers, J.W., Brownfield, S.H., Richardson, R.E., and Nielsen, G.A., 1978, 

General soil map of Montana: Montana Agricultural Experiment Station Miscellaneous 

Publication 16, scale 1:1,000,000.

Soller, D.R., 1993, Preliminary map showing the thickness and character of Quaternary 

sediments in the United States east of the Rocky Mountains: U.S. Geological Survey 

Open-File Report 93–543, scale 1:3,500,000.

Soller, D.R., 1994, Map showing the thickness and character of Quaternary sediments in the 

glaciated United States east of the Rocky Mountains-Northern Plains states (west of 

102° West Longitude): U.S. Geological Survey Miscellaneous Investigations Series 

Map I–1970–D, scale 1:1,000,000.

Swenson, F.A., 1955, Geology and ground-water resources of the Missouri River valley in 

northeastern Montana: U.S. Geological Survey Water-Supply Paper 1263, 128 p.

Thamke, J.N., and Craigg, S.D., 1997, Saline-water contamination of Quaternary deposits and 

the Poplar River, East Poplar oil field, northeastern Montana: U.S. Geological Survey 

Water-Resources Investigations Report 97–4000, 37 p.

Thomas, G.E., 1974, Lineament-block tectonics—Williston-Blood Creek Basin: American 

Association of Petroleum Geologists Bulletin, v. 58, p. 1182–1191.

U.S. Department of Agriculture, published soils maps of individual counties

Veseth, Roger, and Montagne, Clifford, 1980, Geologic parent materials of Montana soils: 

Montana Agricultural Experiment Station Bulletin 721, 117 p.

Vorhis, R.C., 1949, Progress report on the ground-water hydrology of the Medicine 

Lake-Grenora area, Missouri-Souris Irrigation Project, Montana and North Dakota: 

U.S. Geological Survey Open-File Report, 88 p.

Whitaker, S.T., 1980, The Flaxville Formation in the Scobey-Opheim area, northeastern 

Montana: Boulder, University of Colorado, M.S. thesis, 164 p.

Witkind, I.J., 1959, Quaternary geology of the Smoke Creek-Medicine Lake-Grenora area, 

Montana and North Dakota: U.S. Geological Survey Bulletin 1073, 80 p.

NORTH DAKOTA

Clayton, Lee, Moran, S.R., Bluemle, J.P., and Carlson, C.G., 1980, Geologic map of North 

Dakota: U.S. Geological Survey, scale 1:500,000.

Colton, R.B., Lemke, R.W., and Lindvall, R.M., 1963, Preliminary glacial map of North 

Dakota: U.S. Geological Survey Miscellaneous Geologic Investigations Map I–331, 

scale 1:500,000.

Dove, L.P., 1922, Clinkertill, a new metamorphic rock: Science, v. 56, p. 338.

Freers, T.F., 1970, Geology and ground water resources, Williams County, North Dakota—Part 

I, Geology: North Dakota Geological Survey Bulletin 48, pt. 1, 55 p.

Fullerton, D.S., Christiansen, E.A., Schreiner, B.T., Colton, R.B., and Clayton, Lee, 2007, 

Quaternary geologic map of the Regina 4° × 6° quadrangle, United States and Canada: 

U.S. Geological Survey Miscellaneous Investigations Series Map I–1420 (NM–13), 37 

p., map scale 1:1,000.000.

Fullerton, D.S., and Colton, R.B., 1986, Stratigraphy and correlation of the glacial deposits on 

the Montana Plains, in Richmond, G.M., and Fullerton, D.S., eds., Quaternary 

glaciations in the United States of America: Quaternary Science Reviews, v. 5, p. 

69–82.

Fullerton, D.S., Colton, R.B., and Bush, C.A., 2004a, Limits of mountain and continental 

glaciations east of the Continental Divide in northern Montana and northwestern North 

Dakota, U.S.A., in Ehlers, Jurgen, and Gibbard, P.L., eds., Major Quaternary 

glaciations—Extent, timing, and global synchroneity, Vol. 2, North America: 

Amsterdam, Elsevier, p. 123–143.

Fullerton, D.S., Colton, R.B., Bush, C.A., and Straub, A.W., 2004b, Map showing spatial and 

temporal relations of mountain and continental glaciations on the Northern Plains in 

northern Montana and northwestern North Dakota: U.S. Geological Survey 

Miscellaneous Investigations Series SIM–2843, 36 p., scale 1:1,000,000.

Hansen, D.E., 1967, Geology and ground water resources of Divide County, North Dakota— 

Part I, Geology: North Dakota Geological Survey Bulletin 45, 100 p.

Lemke, R.W., Laird, W.M., Tipton, M.J., and Lindvall, R.M., 1965, Quaternary geology of the 

northern Great Plains, United States: Princeton, N.J., Princeton University Press, p. 

15–27.

Moran, S.R., Clayton, Lee, Hooke, R.L., Fenton, M.M., and Andriashek, L.D., 1980, 

Glacier-bed landforms of the prairie region of North America: Journal of Glaciology, v. 

25, no. 93, p. 457–476.

Sigsby, R.J., 1966, "Scoria" of North Dakota: Grand Forks, University of North Dakota, Ph.D. 

dissertation, 218 p.

Vorhis, R.C., 1949, Progress report on the ground-water hydrology of the Medicine 

Lake-Grenora area, Missouri-Souris Irrigation Project, Montana and North Dakota: 

U.S. Geological Survey Open-File Report, 88 p.

Witkind, I.J., 1959, Geology of the Smoke Creek-Medicine Lake-Grenora area, Montana and 

North Dakota: U.S. Geological Survey Bulletin 1073, 80 p. 

49°00' 49°00'

48°00'

48°30'

 LIST OF MAP UNITS

Minor moraines—Mainly till. Most of the ridges delineate the configurations of former ice

 margins. Local relief of moraines of late Wisconsin age typically is 1–4 m. Moraines

 of Illinoian age, mapped northwest of Wolf Point, are very subdued and are conspicuous

 only when viewed from the air. Includes "ice-crack moraines," "crevasse fillings,"

 "small moraines," "washboard moraines," and "annual moraines" 

Limit of residual erratic glacial boulders on dissected bedrock surfaces—

 Symbol is in northwest corner of quadrangle. Locally boulders are on or pressed into

 gravel deposits of Tertiary age (map unit xsh). Boulders are chiefly igneous and

 metamorphic rocks from the Canadian Shield or quartzite. Till has not been identified.

 Glacial, ice-contact, and glaciofluvial deposits were removed by erosion. Many boulders

 apparently were transported to the region by ice during early Pleistocene or late Pliocene

 contintental glaciation 

Concealed (buried) glaciotectonic "raft" or "megablock"—Glaciotectonic

 deposits as described above. The buried features, in the axis of the buried ancestral

 bedrock valley of the Missouri River north of Brockton and south of Medicine Lake, lack

 diagnostic surface expression. See IMPORTANT STRATIGRAPHIC SECTIONS No. 6,

 No. 7 and No. 8 

Limit of illinoian glaciation—Dashed where inferred; ticks are on the side covered by ice 

Buried pre-Illinoian end moraine—Margins defined approximately

Direction of ice movement indicated by striations—The southeast-trending striations

 south of the Missouri River south of Culbertson were produced during Illinoian glaciation.

 Exposures of striated bedrock are very uncommon in the Wolf Point quadrangle.

 Southwest trending striations north of Culbertson were produced during late Wisconsin

 glaciation

Paleowind direction indicated by dune orientations—Mapped east of Medicine Lake

Buried bedrock river valley of the ancestral Missouri River—Margins defined

 approximately, primarily on basis of well records and drill-hole records in Vorhis (1949),

 Swenson (1955), Levings (1986), Donovan and Bergantino (1987), and Donovan (1989)

Location of important stratigraphic section—See IMPORTANT STRATIGRAPHIC

 SECTIONS

Location of city or town

Brockton-froid fault zone (Colton and Bateman, 1956a; Colton, 1963a;

 Thomas, 1974, Crone and Wheeler, 2000)—Till has not been observed directly

 overlying bedrock in auger holes in the axis of the fault zone; apparently, the bedrock there is

 directly overlain by stratified ice-contact, glaciofluvial, and lacustrine sediments. The fault

 zone is the "linear channel" of Witkind (1959) 

Ice-molded or ice-scoured landform—Drumlin, rock drumlin, flute, or groove. Long

 axis of symbol is parallel to direction of ice movement

Inferred limit of a glacial readvance marked by the distal margin of

 glaciotectonic deposits or glaciotectonic structures—Decoration is on the

 side of the advance. See symbol IT

Marginal end moraine—Single till ridge formed along the margin of an ice lobe. Ridge is

 too narrow to map as a map unit at this scale

EXPLANATION OF MAP SYMBOLS

Flood-plain and channel alluvium

Flood-plain and channel alluvium

Lake clay and silt

Lake silt and sand

Dune sand

Swamp deposits

Eolian silt and sand

Colluvium, sheetwash alluvium, and glaciofluvial-fill deposits

Loamy and clayey sheetwash alluvium

Eolian silt and sand

Ground-moraine deposits

End-moraine deposits

Stagnation-moraine deposits

Kame-moraine deposits

Ice-contact sand and gravel

Outwash sand and gravel

Beach deposits

Bedrock

Known or suspected glaciotectonic deposits or glaciotectonic terrain—Bedrock

 and surficial deposits that were thrust, stacked, and deformed by glacial ice. Chiefly (1)

 steeply tilted bedrock blocks overlying till and stratified sediments; (2) stacked or

 imbricated slices of bedrock, till, and stratified sediments forming parallel or concentric

 ridges; (3) deformed masses of bedrock and surficial deposits characterized by overturned

 folds; or (4) isolated blocks, isolated irregular masses, or isolated, relatively smooth,

 nearly equidimensional hills downglacier from source depressions. Some glaciotectonically

 transported or displaced materials are covered by till that was deposited by overriding ice.

 Thickness of transported or displaced materials 10 to >100 meters 

Contact

Limit of late Wisconsin glaciation—Dashed where inferred; ticks are on the side

 covered by ice. At and south of the International Boundary, the limit of late Wisconsin

 glaciation is the limit of a glacial readvance that overrode the earlier glacial limit

Limit of a late Wisconsin glacial readvance, or position of

 a significant stillstand of an ice margin—Ticks are on the

 side of the advance

Esker—Subglacial or englacial stream deposit

PRE-QUATERNARY

QUATERNARY AND TERTIARY

HOLOCENE, LATE PLEISTOCENE, AND MIDDLE PLEISTOCENE

HOLOCENE AND LATE WISCONSIN

Loamy till

LATE WISCONSIN

al

agu

lca

lss

hs

ed

eu

cad

wla

eux

xsh Sandy and loamy disintegration residuum

Loamy or sandy loamy till

ILLINOIAN

tks

ggi Outwash sand and gravel

Loamy colluvium, clinker, till, and sheetwash alluvium

QUATERNARY

ckq

tlx

tlx(e)

tlx(s)

ke

kg

gg

lb

R

IT

Shoreline

NOTE :

 This map was prepared to serve as a database for compilation of a Quaternary geologic map of the Regina 4 ̊ x 6 ̊ quadrangle,

United States and Canada, scale 1:1,000,000 (Fullerton and others, 2007). Letter symbols for the map units are those used for the

same units in the Quaternary Geologic Atlas of the United States map series. This map is a compilation of data from many sources,

listed in SOURCES OF INFORMATION, at several different map scales. Some of the map data are simplified and generalized. Many

surficial deposits that can be shown accurately at 1:250,000 scale are omitted here because they are too small to be mapped at

1:1,000,000 scale. 

 Map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example,

ground moraine deposits, end moraine deposits, and stagnation moraine deposits, all composed of till), are distinguished for purposes

of reconstruction of glacial history. Deposits and materials are distinguished on the basis of genesis, lithology or composition, texture

or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology

or agronomy. Rather, it is a generalized map of soils as recognized in engineering geology, or of substrata or parent materials in which

pedologic or agronomic soils are formed 

CHRONOLOGIC CONTROLS

Zircon Fission-track (ZFT) and Zircon Uranium-thorium/helium [(U-Th)/He] Ages

[See description of map unit ckq] 

Clinkered bedrock samples and clinkered till samples were collected in 1979 by D.A. Coates, R.B. Colton, and D.S.

Fullerton. When the samples were collected in the field, the sample numbers, locations of sample sites, sample

designations, and other data were plotted on a map at 1:48,000 scale showing coal beds and clinker (Map C24, sheet 1,

in Prichard and Landis, 1955). That map here is referred to as field map 1979.

Sample 79M 11 (field map 1979; D.A. Coates, written commun. 1986) is incorrectly identified as sample 79M 7 and

the location of the site is incorrect in Heffern and others (2007). A ZFT age, <0.06 Ma, was determined for zircon in the

clinker by C. W. Naeser (D.A. Coates, written commun., 1986; Heffern and others, 2007). The sample was clinkered

bedrock, underlain and overlain by unaltered Fort Union Formation bedrock. The overlying bedrock was overlain by 2.8

m of unaltered Illinoian-age Kisler Butte till. The clinker outcrop was north of the Missouri River, east of the north end

of the Montana Highway 16 bridge south of Culbertson, Montana, on the north wall of the postglacial diversion course

of the Missouri River, in sec. 3, T. 27 N., R. 56 E. The F/T age indicates only that postglacial incision of the Missouri

River in that vicinity, exposing the lignite, occurred less than 60,000 years ago. It does not provide any specific

information about the ages of any of the glacial deposits in the region.

Sample 79M 7 (field map 1979) is incorrectly identified as sample 79M 11 and the location of the site is incorrect in

Heffern and others (2007). A U-Th/He age, <0.2 Ma, was determined for zircon in clinkered till (Heffern and others,

2007). The sample was zircon from a cobble (clast) of older clinkered till in unaltered Crazy Horse till. The site is in

SE1/4 sec. 8, T. 27 N, R. 56 E. The U-Th/He age is a maximum age for the late Wisconsin-age Crazy Horse till;

however, it does not clarify the age of the Crazy Horse till. The identity of the till that was clinkered is not known; the

age indicates that the clinkered till was formed after deposition of the Archer till. Possibly it was clinkered after

deposition of the Illinoian-age Kisler Butte till. Clinkered pre-Illinoian-age Archer till and clinkered Illinoian-age Kisler

Butte till both are exposed nearby.

Sample 638-2zA, U-Th/He age 0.138±0.015 Ma, and sample 638-2zB, U-Th/He age 0.198±0.48 Ma, were zircon from

clinkered till in a pit east of Montana Highway 16, north of Culbertson, Montana (Heffern and others, 2007). A weighted

mean age of 0.144+0.014 Ma was reported by Heffern and others (1007). The pit was in SW sec.16, T. 28 N., R. 56 E.

The identity of the till that was baked is not known. Pre-Illinoian-age Archer till is exposed in the vicinity of the pit and

the ages apparently are minimum ages for Archer till. 

Lava Creek B tephra

Northwest of Intake, Montana, in the adjacent Glendive quadrangle south of this quadrangle, the Lava Creek B distal

airfall tephra (Izett and Wilcox, 1982) was deposited in an alluvial-fan-dammed lake in an abandoned meltwater channel

that had been formed earlier, during deposition of the upper till member of the Archer till (Fullerton and others, 2004b).

The40Ar/39Ar age of member B of the Lava Creek Tuff is 639+2 ka (Lanphere and others, 2002). Abundant snail tests

in the lake sediment beneath the volcanic ash indicate that tephra deposition did not closely follow late Archer

deglaciation at that site. Clasts of the volcanic ash were incorporated in Illinoian-age Kisler Butte till. The 40Ar/39Ar

age is a minimum age for both members of the Archer till and a maximum age for the Kisler Butte till in northeastern

Montana. 

Radiocarbon Ages

Organic material at the Burns Creek archeologic site (24RL295), beneath a terrace in the Yellowstone River valley in the

Glendive quadrangle south of this quadrangle, yielded two accelerator mass spectrometry (AMS) ages: 46,550±1030 14C

yr (Beta-235538) and 46,950+1080 14C yr (QA-1944) (W.C. Aber, written commun., 2007). The Beta Analytical

laboratory report in 2007 indicated that the material was "striated wood charcoal" and there was "no evidence of coal or

any other geologic material." The radiocarbon ages here are interpreted to be minimum ages for the pre-Illinoian Archer

till and the Illinoian Kisler Butte till and maximum ages for the late Wisconsin Crazy Horse till (Fullerton and others,

2004a, b).

Collogen from a mammoth tooth in gravel beneath sediment from glacial Lake Glendive near Glendive, Montana, also in

the Glendive quadrangle, yielded an age of 24,370±104 14C yr (Beta-155642) (Hill, 2006). The age is a maximum age

for the late Wisconsin Crazy Horse till.

Two radiocarbon ages from deposits farther west and southwest of the Wolf Point 1° x 2° quadrangle, 30,052±641 14C yr

(SR-6023) and 38,672±347 14C yr (Beta-155639) , reported by Hill (2006), apparently are maximum ages of glacial lakes

that were dammed by ice during maximum late Wisconsin glaciation. 

IMPORTANT STRATIGRAPHIC SECTIONS

[Stratigraphic units are listed from youngest to oldest. Rank terms of informal units are not capitalized. A given unit thickness in an

exposure is the maximum thickness] 

Stratigraphic nomenclature of Fullerton and Colton (1986) is retained here on an informal basis, with revision of the temporal

framework of the glacial deposits. The named (informal) tills are allostratigraphic units, not lithostratigraphic units. The complex

subsurface stratigraphy in the buried valley of the ancestral Missouri River in extreme northeastern Montana has not been resolved. 

Poplar section, sec. 1, T. 27 N., R. 50 E., Mont.-Reference section for Crazy Horse till, Markles Point till, and Archer till.

Holocene and (or) late Wisconsin, 0.6 m pebbly sand and silt; late Wisconsin, 1.2 m oxidized and unoxidized Crazy Horse

till; Illinoian, 2.1 m oxidized Markles Point till; middle Pleistocene, >3.1 m oxidized upper unit of Archer till 

MBMG drill hole 85-18 (Donovan and Bergantino, 1987), sec. 6, T. 28 N., R. 52 E., Mont.-Late Wisconsin, 0.6 m gravel,

2.5 m unoxidized Crazy Horse till; Pleistocene, 0.3 m gravel; middle Pleistocene, 5.8 m oxidized Archer till, 1.8 m

oxidized and unoxidized clay and silt, 1.5 m oxidized Archer till, 6.l m oxidized and unoxidized Sprole Silt, 8.2 m Wiota

gravel. The two units of Archer till likely represent two glaciations 

MBMG drill hole 85-21-A (Donovan and Bergantino, 1987), sec. 30, T. 28 N., R. 52 E., Mont.-Holocene, 3.l m oxidized

sheetwash alluvium(?); Pleistocene, 0.6 m sand and gravel; Illinoian, 2.5 m oxidized Markles Point till; Pleistocene, 0.6 m

oxidized and unoxidized silt and sand; middle Pleistocene, 4.9 m oxidized Archer till, 12.2 m oxidized sand, silt, and clay,

1.8 m oxidized and unoxidized Archer till, 6.l m unoxidized clay, 1.5 m interbedded unoxidized Archer till, clay, silt, and

sand, 15.9 m unoxidized Sprole Silt, 2.7 m Wiota Gravel. The two units of Archer till likely represent two glaciations 

MBMG drill hole 84-28A (Donovan and Bergantino, 1987), sec. 35, T. 29 N., R. 52 E., Mont.-Late Wisconsin, 4.9 m

oxidized and unoxidized Crazy Horse till; Pleistocene, 0.6 m oxidized and unoxidized clay; Illinoian, 1.8 m oxidized

Markles Point till; middle Pleistocene, 5.2 m oxidized and unoxidized clay, 5.5 m unoxidized Archer till, 0.6 m unoxidized

clay and silt, 2.6 m unoxidized Archer till, 1.5 m Wiota gravel 

MBMG drill hole 84-30A (Donovan and Bergantino, 1987), sec. 6, T. 28 N., R. 53 E., Mont.-Holocene and (or) late

Wisconsin, 2.5 m sand; late Wisconsin, 5.3 m oxidized and unoxidized Crazy Horse till; Pleistocene, 1.5 m sand and

gravel, 0.3 m peat; Illinoian, 6.4 m unoxidized Markles Point till; middle Pleistocene, 0.9 m peat, clay, and sand; 4.3 m

unoxidized Archer till, 1.1 m unoxidized clay, 2.0 m unoxidized Archer till, 3.1 m sand, 1.7 m Wiota gravel 

MBMG drill hole 83-1 (Donovan and Bergantino, 1987), sec. 1, T. 29 N., R. 53 E., Mont.-Section in a buried

glaciotectonic structure. Pleistocene, 2.4 m oxidized till, 3.7 m oxidized till (different till), 6.7 m unoxidized till, 7.0 m

unoxidized sand, 0.6 m Wiota gravel, 4.l m bedrock, 3.2 m unoxidized till, 2.1 m unoxidized clay, 1.2 m bedrock or sand,

12.8 m bedrock, 12.8 m unoxidized till 

MBMG drill hole 83-4A (Donovan and Bergantino, 1987), sec. 16, T. 30 N., R. 55 E., Mont.-Section in a buried

glaciotectonic structure. Pleistocene, 5.5 m sand, 0.3 m "coal" (bedrock?), 3.4 m sand, 3.1 m gravel and sand, 4.6 m

oxidized sand. 3.7 m oxidized till, 0.9 m "coal" (bedrock?), 2.l m sand, 1.5 m gravel and sand, 2.4 m sand, 4.3 m bedrock,

8.8 m sand and gravel, 5.6 m bedrock, 3.8 m gravel 

USGS Medicine Lake test hole (Swenson, 1955), sec. 28, T. 31 N., R. 56 E., Mont.-Section in a buried glaciotectonic

structure. Pleistocene, 1.5 m gravel, 15.8 m oxidized and unoxidized till, 3.7 m sand and clay, 2.7m unoxidized till, 3.3 m

bedrock, 1.5 m oxidized till, 24.1 m unoxidized clay, 4.3 m unoxidized till, 0.9 m boulder gravel, 18.0 m unoxidized till,

2.4 m boulder gravel, 5.8 m interbedded unoxidized till and gravel, 20.7 m bedrock, 4.0 m oxidized and unoxidized till 

Kisler Butte section, sec. 15, T. 34 N, R. 54 E., Mont.-Reference section for Crazy Horse till, Kisler Butte till, and Archer

till. Holocene and (or) late Wisconsin, 0.3 m eolian sand and silt; late Wisconsin, 1.8 m oxidized and unoxidized Crazy

Horse till; Illinoian, 0.9 m oxidized Kisler Butte till, pavement of cobbles and boulders, 1.4 m oxidized and unoxidized

Kisler Butte till; middle Pleistocene, cobble and boulder pavement; 0.8 m oxidized lacustrine sand and silt, 1.8 m gravel,

3.7 m oxidized Archer till, 1.8 m gravel 

1

2

3

4

5

6

7

8

9

T

64

N

T

63

N

T

62

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T

61

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60

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59

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58

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57

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56

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T

56

N

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52

N

T

52

N

T

53

N

T

54

N

T

55

N

T

54

N

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53

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26

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T

27

N

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28

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30

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62

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64

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63

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36

N

T

35

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34

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33

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T

32

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31

N

R 104 E

R 58 E R 59 E R 104 E R 45 E R 46 E R 47 E R 48 E R 49 E R 50 E R 51 E R 52 E R 53 E R 54 E R 55 E R 56 E R 57 E R 44 E

R 103 E

R 56 E R 57 E R 58 E R 45 E R 46 E R 47 E R 48 E R 49 E R 50 E R 51 E R 52 E R 53 E R 54 E R 55 E R 44 E

T

37

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28

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27

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26

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R

6 0 0

6 0 0

6 0 0

6 0 0

6 0 0

6 0 0

7 0 0

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700

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7 0 0

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9 0 0

xsh

wla

R

tlx(e)

tlx

tlx R tlx(s)

xsh

gg

lca

tlx(e)

tlx xsh tlx(e)

tlx(s)

tlx

gg

xsh

xsh

lss

tlx

tlx(s)

tlx

xsh lca

tlx(e) xsh tlx lca lca

xsh

tlx

lss

wla

xsh

lca

wla tlx(s) kg

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Peerless

Scobey

Flaxville

Outlook

Plentywood

Westby

Medicine Lake

Froid

Culbertson Bainville

Brockton

Poplar

Wolf Point

105 ̊ 30' 105 ̊ 00' 104 ̊ 30'

48 ̊ 00'

105 ̊ 00'

PLATEAU

PEERLESS

FLAXVILLE

 PLAIN

M

O

N

TA

N

A

N

O

RT

H

D

A

K

O

TA

UNITED STATES

CANADA

104°00'

106°00'

48°30'

104°00'

105°30' 104°30'

106°00'

Mountain Valley And Piedmont Glaciation

Laurentide Continental Glaciation

Pinedale till

Laurentide Continental Glaciation

Illinoian till

Location of city or town

Scattered glacial erratic boulders, no till

Not glaciated

Late Wisconsin till

LW 

EXPLANATION

Glacier

National

Park

Highwood

Mountains

Bearpaw

Mountains

Little Rocky Mts

Cypress

Figure 1. Regional ice flow during maximum late Wisconsin glaciation.

Killdeer

Mountains

Boundary

Plateau

50°

49°

48° Williston

47°

Shelby

Glasgow

Cut Bank

Choteau

Two Medicine

 lobe

Lewistown

Late Wisconsin phase of

glacial Lake Musselshell

(792 m; 2,600 ft) confluent

with glacial Lake Jordan

Jordan

Late Wisconsin

phase of glacial

Lake Jordan

(792 m; 2,600 ft)

Watford City

Lethbridge

Cypress Lake

Wolf Point

CANADA

C2

Havre

UNITED STATES

Wood Mountain

 Upland

Flaxville 

 Plain

25 25 50 75 100 KILOMETERS 0

25 25 50 75 100 MILES 0

Lake Sakakawea 

Porcupine Hills

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement

by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also contains copyrighted

materials as noted in the text. Permission to reproduce copyrighted items must be secured from the

copyright owner.

This database, identified as OFR 2016–1142, has been approved for release and publication by the U.S.

Geological Survey (USGS). Although this database has been subjected to rigorous review and is

substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and

review. Furthermore, it is released on condition that neither the USGS nor the U.S. Government may be

held liable for any damages resulting from its authorized or unauthorized use.

Publishing support provided by: 

Denver Publishing Service Center

Manuscript approved for publication August 23, 2016

For more information concerning this publication, contact:

Center Director, USGS Geosciences and Environmental Change Science Center

Box 25046, Mail Stop 980

Denver, CO 80225

(303)236-5344

Or visit the Geosciences and Environmental Change Science Center Web site at:

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For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225,

1–888–ASK–USGS

Digital files available at http://dx.doi.org/10.3133/ofr20161142

Suggested Citation: Fullerton, D.S., Colton, R.B., and Bush, C.A., 2016, Quaternary geologic map of the

Wolf Point 1 ̊ × 2 ̊ quadrangle, Montana and North Dakota: U.S. Geological Survey Open-File Report

2016–1142, scale 1:250,000, http://dx.doi.org/10.3133/ofr20161142. 

Base hydrology from U.S. Geological Survey, 1954. Revised 1975

Base topography from National Elevation Dataset (NED), U.S. Geological Survey 1974 (http://seamless.usgs.gov)

Base cities, roads, and railroads from Montana State Library 2011 (http://nris.mt.gov)

Transverse Mercator projection

1927 North American Datum

Geology compiled in 1976–1986, 1990–2002, 2004–2008

Digital layout by Jeffery R. Hartley

Geology digitized by Charles A. Bush

Digital cartography by Charles A. Bush

Published by U.S.Geological Survey Science Publishing Network Denver

Manuscript approved for publication August 23, 2016

CONTOUR INTERVAL 100 METERS

1975 MAGNETIC DECLINATION FROM TRUE NORTH VARIES FROM 151⁄2° EASTERLY FOR 

THE CENTER OF THE WEST EDGE TO 14° EASTERLY FOR THE CENTER OF THE EAST EDGE. 

5 0 5 10 15 20 MILES

Open-File Report 2016–1142

Quaternary Geologic Map of the Wolf Point 1° × 2° Quadrangle, Montana and North Dakota

By

David S. Fullerton, Roger B. Colton, and Charles A. Bush

2016

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

Montana Bureau of Mines and Geology