Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

QTf QTf

QTf

QTf

QTf

Tt

Tt

Kda

Ke

Ku

Ku

Kul

Kul

Kul

Jdu

Jdu

Jdu

Ps

hMu

Ps

hMu

hMu

hMu

Mm

Mm

Mm

Mm

Mm

Mm

Mm

MDt

MDt

MDt

MDt

MDt

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Ad

Ad

Ad

Ad Ad

mi

Ad

Ad

Ad

Ad

At

At

Ad

Jdu Ps

hMu

Mm

Mm

Mm

hMu

Kul

Qs

Am

MDt

Mm Jdu

Mm

Jdu

Qr

Qs

QTf

hMu

PMu

Ps

Ps

Au

Au

Au

Au

Au

Au

Au

Au

Au

Au

QTf

Au

Ps

Qs

Ps

Qs

Qs

Tv

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Ke

Ke

Ke

Ke

Ke

Ku Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

Ku

QTf

QTf

QTf

QTf

QTf

QTf

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Tv

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul

Kul Kul

Kul

Kul

Kul

Kul

Jdu

Jdu Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Jdu

Ps

Ps

hMu

Ps

hMu

hMu

hMu

PMu

hMu

PMu

hMu

PMu

PMu

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

Mm

MDt

MDt

MDt

MDt

MDt

MDt

MDt

MDt

MDt

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Oeu

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Am

Qs

Qs

Qs

Am

Tv

Ti

Qs

Ti

Am

Am

Ti

Ti

MDt

Oeu

Tv

Mm

Ti

Qs

Am

Ps

Ti

Ku

PMu

PMu

Qs

Jdu

Jdu

PMu

Ku

Jdu

Jdu

Jdu

Oeu

Jdu

Kul

Ku

Qs

Ps

Ps hMu

Oeu

hMu

Jdu

Kda

Ps

Klv

Qs

Qs

Qs

Ti

Ti

Tv

Ti

Ti

Ku

Kul

Jdu

Ps

Mm

hMu

Ti

Am

Am

Qs

Klv

Jdu

Ps

Ps

QTf

Ps

Ps Jdu

Jdu

QTf

MDt

Ps

Ps

Kul

Qs

MDt

MDt

Kda

Kda

Kda

Kda

Kul

Ku

Tv

MDt

Mm

Ti

cgu

Ti

Ti

Qs

Ti

Qs

Ps

MDt

Am

Oeu

Ti

Ti

Ti

QTf

Am

Am

Mm

Tc

PMu

Jdu

PMu

Ti

Oeu

Ps

Kda

Qs

Jdu

Qs

Ke

Ti

Am

Qs

Qs

Klv

Qs

Qs

Kul

Ku

MDt

Mm

hMu

Ps

Qs

Tv

Mm

MDt

Qs

MDt

PMu

Ke

Kul

Ke

QTf Ti

Oeu

Jdu

Am

Au

mi

Jdu

mi

mi

Jdu Ps hMu

Jdu

Jdu

Kul Ti

Ti

Ti

Ke

Qs

QTf

Qr

Tt Tv Ti

Tc Ti

mi Am Ad At

cgu

Kda

Klv

Ke

Ku

Kul

Jdu

PMu

Ps

hMu

Mm

MDt

Oeu

Holocene

Pleistocene

Pliocene

Eocene

Upper

Cretaceous

Lower

Cretaceous

Upper and 

Middle Jurassic

Upper

Mississippian

Lower

Mississippian

Upper Devonian

Upper and

Middle Cambrian

QUATERNARY

TERTIARY

CRETACEOUS

JURASSIC

TRIASSIC

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

ORDOVICIAN

CAMBRIAN

PROTEROZOIC

ARCHEAN

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

CORRELATION OF MAP UNITS

Surficial deposits, undivided (Quaternary)—Alluvium, colluvium, talus, 

landslide deposits, rock glaciers, glacial and glaciofluvial deposits, and 

boulder fields. Only selected major areas, generally exposed for at least 1 

mi in a single direction, are shown

Rhyolite (Pleistocene)—Rhyolite flows of Madison Plateau, in extreme 

southern part of map area. Upper part (about 100 ft) is agglomerate 

consisting of blocks of black obsidian (ranging from granules to large 

blocks) in a matrix of unconsolidated glass shards. Much of the obsidian is 

crumbly and spherulitic (1–3 cm in diameter and varicolored). Middle part 

(several hundred feet) is flow-banded rhyolite. Lower part (30 ft) is perlitic 

and spherulitic obsidian agglomerate (Hamilton, 1964)

Felsic volcanic rocks (Pleistocene and Pliocene)—Includes Plateau Rhyolite 

[Central Plateau Member (Pleistocene: Christiansen and Blank, 1972)] 

and Yellowstone Group [including Lava Creek Tuff (Pleistocene: 

Christiansen and Blank, 1972) and Huckleberry Ridge Tuff (Pliocene: 

Love, 1989)]. Plateau Rhyolite is light-gray, dense, lithoidal, fine-grained 

to aphanitic ash-flow tuff. Phenocrysts (1.5 mm in diameter) of quartz, 

sanidine, pyroxene, fayalite, and sphene form 25 percent of rock 

(Witkind, 1972). Yellowstone Group is light-brown to gray, thick-bedded, 

mostly rhyolitic, porphyritic welded tuff and minor flows. Matrix is chiefly 

devitrified glass shards; phenocrysts of sanidine, quartz, and sparse 

plagioclase (Tysdal and Simons, 1985; Tysdal, 1990)

Trachyte, trachybasalt, and basalt (Eocene)—Basalt porphyry, trachybasalt 

porphyry, and trachyte porphyry in volcanic flows and breccias; probably 

correlates with Absaroka Volcanic Supergroup. Mapped south of Hebgen 

Lake (Christiansen and Blank, 1975)

Volcanic rocks of the Absaroka Volcanic Supergroup, undivided 

(Eocene)—Includes Hyalite Peak and Golmeyer Creek Volcanics 

(Chadwick, 1982). Volcanic flows and breccia, andesite and basalt flows, 

pyroxene trachyte porphyry, breccia, tuff, conglomerate, sandstone, 

channel-fill deposits, and minor carbonaceous siltstone. Lava flows 

mostly gray, fine-grained to sparsely porphyritic andesite and basalt; 

plagioclase and pyroxene phenocrysts; aphanitic groundmass; some lava 

more (Simons and others, 1985; Tysdal and Simons, 1985) or less 

(McMannis and Chadwick, 1964) silicic. Volcanic breccia interlayered 

with the flows. Some volcanic units contain abundant fossil wood

Intrusive rocks, undivided (Eocene)—Dacitic, andesitic, and basaltic dikes, 

sills, and small stocks. Dacitic rocks show distinct flow structures and are 

conspicuously porphyritic; contain phenocrysts of plagioclase, 

hornblende, and biotite; matrix of feldspar microlites and devitrified glass. 

Andesitic and basaltic rocks contain a few small phenocrysts of 

plagioclase in pilotaxitic groundmass of andesine(?) microlites and 

interstitial pyroxene and opaque minerals (Simons and others, 1985)

Conglomerate (Eocene)—Poorly indurated conglomerate of cobbles and 

boulders of Precambrian gneiss, amphibolite, vein quartz, Paleozoic 

carbonate strata, and volcanic rocks. Contacts not exposed; presumed to 

be basal unit of Tertiary sequence. Mapped only near Garnet Mountain in 

northern part of Gallatin Range (McMannis and Chadwick, 1964)

Dacitic and andesitic intrusive rocks (Upper Cretaceous)—Gray porphyritic 

dacite and, locally, andesite sills and dikes; hornblende and plagioclase 

phenocrysts; fine-grained to aphanitic plagioclase, potassium feldspar, and 

quartz matrix. Includes dacite porphyry laccolith, more than 1,500 ft 

thick, along Gallatin River (Witkind, 1969); sills as much as 400 ft thick 

and dikes 3–50 ft thick (Tysdal and Simons, 1985; Tysdal, 1990). K-Ar 

and 40Ar/39Ar dates on hornblende 68–69 Ma (Tysdal and others, 1986; 

Tysdal, 1990)

Livingston Formation (Upper Cretaceous)—Upper member is volcaniclastic 

sandstone, mudflow breccia, volcanic conglomerate, and mudstone; 

middle member is dacite to basalt, autoclastic breccia, tuff breccia, welded 

tuff, dacite flows, and volcaniclastic sandstone; lower member is 

intertonguing volcaniclastic sandstone, olivine basalt, mudflow breccia, 

volcanic conglomerate, and mudstone. Well exposed. Total thickness 

1,500–2,500 ft (Roberts, 1972; Tysdal and Simons, 1985; Tysdal, 1990)

Eagle Sandstone, Virgelle Sandstone, and Everts Formation, undivided 

(Upper Cretaceous)—In extreme northeastern part of map area, near 

Cokedale, Eagle Sandstone is divided into an unnamed upper member 

and a lower member, the Virgelle Sandstone. Upper part of upper 

member includes an upper zone of coal beds, carbonaceous siltstone, and 

sandstone that is underlain by well-bedded to massive, medium- to wellsorted, light-olive-gray quartzose sandstone and siltstone; lower part of 

upper member contains two units of coal, carbonaceous siltstone, and 

fine-grained sandstone. Coal zones contain commercial-grade, highvolatile bituminous coal beds, some of coking quality (Roberts, 1972); 

some beds were extensively mined until the early 1900’s. Underlying 

Virgelle Sandstone is very light gray, well-cemented, massive to 

crossbedded, fine-grained arkosic sandstone (Roberts, 1972). Total 

thickness of Eagle Sandstone is 645 ft, including the 110-ft-thick Virgelle 

Sandstone (Roberts, 1966).

In Madison Range only the Virgelle Sandstone is mapped and 

overlying strata are assigned to the Everts Formation rather than the 

Eagle Sandstone (Tysdal and Simons, 1985; Tysdal, 1990). Upper 

1,000–1,200 ft of Everts Formation is gray, fine- to medium-grained 

quartz-rich sandstone and interbedded siltstone; contains mudstone, 

porcellanite, and finely crystalline limestone beds; lower 200–300 ft is 

thin interbeds of mudstone, siltstone, shale, coal, and minor sandstone, 

and a few beds of several-feet-thick, light-gray, fine- to medium-grained, 

crossbedded sandstone. Virgelle Sandstone is thin- to thick-bedded, 

medium- to coarse-grained, crossbedded quartz sandstone that forms 

prominent white-weathering ledges; thickness 75–165 ft (Tysdal, 1990)

Upper Cretaceous sedimentary rocks, undivided—In descending order, 

includes Eagle Sandstone, Telegraph Creek Formation, Cody Shale, 

Frontier Formation, and Mowry Shale. Includes Eagle Sandstone (Ke) 

along northwest corner of Yellowstone National Park; see description of 

unit Ke. Telegraph Creek Formation is predominantly siltstone and thinbedded, moderately well sorted sandstone cemented with calcite and 

containing calcareous concretions; weathers distinctive yellowish gray 

(Roberts, 1972). In Madison Range, upper part of Telegraph Creek 

Formation is light-brown-weathering mudstone and siltstone, with minor 

sandstone and glauconite in some beds; middle part has white-weathering 

tuffaceous siltstone marker; lower part is siltstone and mudstone overlying 

ledge-forming, gray, “salt-and-pepper” sandstone (Tysdal and Simons, 

1985). About 675 ft thick in Madison Range (Tysdal and Simons, 1985). 

Cody Shale is mudstone and thin interbeds of gray-green siltstone and 

minor fine-grained sandstone; about 1,000 ft thick (Tysdal and Simons, 

1985). Frontier Formation is gray sandstone interlayered with darker 

gray siltstone and mudstone in northern part of map area; gray-green 

glauconitic sandstone, siltstone, and mudstone with zones of coaly shale, 

pale-green tuff, and porcellanite in southern part; total thickness about 

400 ft (Tysdal and Simons, 1985). Mowry Shale is included only along 

Gallatin River in central part of map area; elsewhere, Mowry Shale is 

included with undivided Upper and Lower Cretaceous sedimentary rocks 

(Kul). Upper part of Mowry Shale is slope-forming, gray mudstone; lower 

part is pastel-colored mudstone, porcellanite, welded tuff, siltstone, and 

sandstone; total thickness about 700–900 ft (Tysdal and Simons, 1985)

Upper and Lower Cretaceous sedimentary rocks, undivided—In descending 

order, includes Mowry Shale (Upper Cretaceous) and Muddy Sandstone, 

Thermopolis Shale, and Kootenai Formation (Lower Cretaceous). 

Includes Mowry Shale except along Gallatin River in central part of map 

area where Mowry is included with undivided Upper Cretaceous 

sedimentary rocks unit (Ku); see unit Ku for description of Mowry Shale. 

Upper part of Muddy Sandstone is gray to tan sandstone and arkosic 

sandstone; middle part is dark-gray siltstone, fine-grained sandstone, and 

shale; lower part is poorly sorted, ledge-forming, crossbedded sandstone; 

total thickness about 125–350 ft (Tysdal and Simons, 1985). Upper part 

of Thermopolis Shale is dark-gray, locally carbonaceous, fissile shale; 

lower part is brown, rusty-weathering sandstone with crossbeds and ripple 

marks; total thickness 200–250 ft (Tysdal and Simons, 1985). Upper 

part of Kootenai Formation is nonmarine gastropod limestone; middle 

part is variegated red-yellow-gray mudstone, siltstone, and minor 

sandstone and limestone; lower part is ledge-forming, cherty, quartzose 

sandstone and conglomeratic sandstone; total thickness about 350–500 ft 

(Tysdal and Simons, 1985)

Jurassic and Triassic sedimentary rocks, undivided—In descending order, 

includes Morrison Formation (Upper Jurassic); Ellis Group (Upper and 

Middle Jurassic); Chugwater Formation (Triassic); and Thaynes(?) 

Formation, Woodside Siltstone, and Dinwoody Formation (Lower 

Triassic). Morrison Formation is varicolored nonmarine claystone and 

mudstone; about 225–400 ft thick (Simons and others, 1985; Tysdal and 

Simons, 1985). Ellis Group comprises Swift, Rierdon, and Sawtooth 

Formations. Swift Formation is cream-colored to brown to gray, oolitic, 

shelly, cherty, calcareous and glauconitic sandstone, sandy limestone, and 

chert-pebble conglomerate; Rierdon Formation is gray-brown oolitic 

limestone, fossiliferous gray shale, and argillaceous limestone; Sawtooth 

Formation (lithic equivalent to Piper Formation of central Montana) is 

gray, fine-grained, fossiliferous limestone, argillaceous limestone, shale, 

and varicolored siltstone. Ellis Group is about 80–300 ft thick (Simons 

and others, 1985; Tysdal, 1985). Chugwater Formation is poorly 

exposed red siltstone, shale, and fine-grained sandstone; few thin gypsum 

beds; about 500 ft thick (Simons and others, 1985). Thaynes(?) 

Formation is gray-orange, thin-bedded, calcareous siltstone and graygreen clay shale; local ledge former; only 0–10 ft thick (Tysdal and 

Simons, 1985). Woodside Siltstone is red, thin-bedded siltstone and 

mudstone interbedded with gypsum and thin gray limestone beds; 

thickness varies from 0 to 725 ft (Tysdal and Simons, 1985). Dinwoody 

Formation is brown to yellow-gray, chocolate-brown-weathering, thinbedded limestone, silty limestone, and calcareous siltstone; about 70–265 

ft thick (Simons and others, 1985; Tysdal and Simons, 1985)

Permian, Pennsylvanian, and Mississippian sedimentary rocks, 

undivided—In descending order, includes Shedhorn Sandstone (Permian), 

Quadrant Sandstone (Pennsylvanian), and Amsden Formation (Lower 

Pennsylvanian and Upper Mississippian). Sandstone, siltstone, mudstone, 

shale, chert, limestone, and dolomite. Refer to units Ps and hMu for 

descriptions of formations

Shedhorn Sandstone (Permian)—Lateral equivalent to the Phosphoria 

Formation to the west and south (McKelvey and others, 1959). Mostly 

brown to gray, locally conglomeratic sandstone containing abundant 

grains, nodules, and layers of chert and pellets of phosphorite (Simons 

and others, 1985). From top to bottom: interlayered chert beds and 

common vertical cylindrical burrows; dark-colored, gray to brown, thinbedded chert with siltstone partings over phosphatic mudstone and 

limestone; brown to dark-gray, well-cemented sandstone with interbeds of 

chert and limestone; and yellow-gray dolomite with abundant chert 

fragments and a few interbeds of dark-brown sandstone. Thickness 

115–225 ft (Tysdal and Simons, 1985; Tysdal, 1990)

Quadrant Sandstone (Pennsylvanian) and Amsden Formation (Lower 

Pennsylvanian and Upper Mississippian), undivided—Quadrant 

Sandstone is white to tan, bedded, clean, well-sorted quartz sandstone 

with silica or calcite cement. Interbeds of yellow-brown dolomite and gray 

limestone in lower part. Thickness about 200–315 ft (Tysdal, 1990). 

Underlying Amsden Formation is red to pink, calcareous siltstone to 

shale. Upper part of formation contains calcareous sandstone cemented 

with iron oxides; middle and lower parts contain limestone, limestonepebble conglomerate, and dolomite. Thickness 40–160 ft (Tysdal, 1990)

Madison Group (Mississippian)—Includes Mission Canyon Limestone and 

underlying Lodgepole Limestone. Mission Canyon Limestone is buff to 

brown, gray-weathering, bedded, finely crystalline limestone and minor 

dolomite with some oolitic, bioclastic, and crossbedded layers. Orange 

solution breccia in upper part. Persistent cliff former. Lodgepole 

Limestone is more fossiliferous and contains partings of calcareous silty 

limestone; chert nodules and stringers in lower beds. Total thickness 

about 1,300–1,450 ft (Tydsal, 1990; Tysdal and Simons, 1985; Simons 

and others, 1985)

Three Forks Formation (Lower Mississippian and Upper Devonian) and 

Jefferson and Maywood Formations (Upper Devonian), 

undivided—At top of unit, Three Forks Formation includes, in 

descending order, Sappington, Trident, and Logan Gulch Members. 

Sappington Member is gray to yellow, calcareous siltstone, siltstone, and 

sandstone; only uppermost part is Lower Mississippian in age. Trident 

Member is gray to yellow dolomite, dolomitic shale, and some limestone. 

Logan Gulch Member is red, orange, or yellow carbonate-shale breccia. 

Total thickness 100–250 ft (Simons and others, 1985; Tysdal, 1990; 

Tysdal and Simons, 1985). Jefferson Formation includes Birdbear 

Member and underlying Lower Member. Birdbear Member is brown, 

coarse-grained, ledge-forming dolomite. Lower Member is brown-gray, 

fine-grained (sucrosic) dolomitic limestone and limestone; dolomite is fetid 

and has petroliferous odor. Total thickness about 300–450 ft (Simons 

and others, 1985; Tysdal, 1990; Tysdal and Simons, 1985). Locally in 

northern part of map area, Maywood Formation is at base of unit; palebrown-gray, silty, sandy, and pebbly dolomite overlying yellow, dolomitic, 

sandy, and conglomeratic siltstone on a regolith (or breccia) base; about 

34 ft thick (McMannis and Chadwick, 1964; Roberts, 1964f)

Ordovician and Cambrian sedimentary rocks, undivided—In descending 

order, includes Bighorn(?) Dolomite (Ordovician); Snowy Range 

Formation (and laterally equivalent Red Lion Formation) and Pilgrim 

Limestone (Upper Cambrian); and Park Shale, Meagher Limestone, 

Wolsey Shale, and Flathead Sandstone (Middle Cambrian). Bighorn(?) 

Dolomite is light-gray, dense cryptocrystalline dolomite; about 35 ft thick 

(Tysdal, 1990). Snowy Range Formation, which includes Grove Creek 

Limestone, Sage Limestone, and Dry Creek Shale Members, is tan, thinbedded limestone with irregular-shaped red mottles and interbedded red 

silty mudstone underlain by green, thin-bedded dolomite and dolomitic 

mudstone with green clay-shale partings in the upper part and red 

calcareous siltstone and green sandy clay shale in the lower part; 

thickness about 300 ft (Tydsal, 1990). Pilgrim Limestone is brown, 

nodular limestone and dolomitic limestone with partings of dolomitic 

siltstone and silty dolomite. Limestone is glauconitic and mottled. Mudpebble conglomerate and oolite beds are common. About 200 ft thick 

(Tydsal, 1990). Park Shale is gray-green, chippy shale and a few 

interbeds of limestone, limestone pebble conglomerate, and oolitic 

limestone. Fossil fragments, burrows, and trace fossils (“worm trails”) are 

common. Thickness about 100 ft (Tydsal, 1990). Meagher Limestone 

(pronounced “mar”) is finely crystalline limestone with irregular-shaped, 

yellow-orange siltstone mottles. Upper part contains thin partings of 

calcareous siltstone or green clay shale; lower part contains mottled gray 

oolitic limestone and gray, finely crystalline limestone. About 500 ft thick 

(Tydsal, 1990). Wolsey Shale is gray-green, fissile, micaceous clay shale; 

65–200 ft thick (Tysdal, 1990). Flathead Sandstone is white, tan, and 

red-brown, hematitic quartz sandstone; locally glauconitic. Crossbeds, 

ripple marks, and worm trails are common. Thickness 10–100 ft (Tysdal, 

1990)

Mesozoic and Paleozoic sedimentary rocks, undivided—Limestone, 

dolomite, chert, shale, siltstone, and sandstone. Mapped only at east 

edge of northern part of map area (Chadwick, 1982)

Mafic intrusive rocks, undivided (Proterozoic and Archean?)—Diabase and 

amphibolite dikes and sills. Diabase sills form cliffs. Northwest-trending 

diabase dikes in Spanish Peaks area are Proterozoic (K.S. Kellogg, USGS, 

written commun., June 21, 1996). Plagioclase phenocrysts in a matrix of 

augite, smaller plagioclase laths, and magnetite. Secondary alteration 

around associated calcite-quartz veins that commonly contain malachite 

(Becraft and others, 1966; Erslev, 1981, 1983)

Ultramafic rocks (Archean)—Serpentinized ultramafic rocks exposed as pods 

and lenses; generally surrounded by reaction zones (Erslev, 1983)

Metamorphic rocks (Archean)—Gneiss, schist (biotite, chlorite-hornblende), 

quartzite, pegmatite, amphibolite, mafic intrusive (diabase and gabbro) 

rocks, and minor ultramafic rocks. Includes granitic rocks in Mulherin 

(also known as Mol Heron) Creek area, east-central part of map area

Dolomitic marble (Archean)—Coarsely crystalline dolomite with crenulated 

quartz veins. Locally contains tremolite (Witkind, 1969, 1972)

Tremolite marble (Archean)—Marble composed almost entirely of bladed 

tremolite crystals. Light gray to gray; extremely resistant; forms 

topographic ridges. Technically a calc-silicate; tremolite marble 

terminology from Witkind (1969). Mapped only in southeastern part of 

map area

Contact—Dashed where approximately located

Normal fault—Dashed where approximately located; dotted where concealed. 

Ball and bar on downthrown side where direction of movement is known. 

Opposed arrows indicate sense of lateral displacement where known

Thrust fault—Dotted where concealed. Sawteeth on upper plate

Overturned thrust fault—Sawteeth in direction of dip; base of sawteeth on 

side of tectonically higher plate. Shown in extreme northeastern part of 

map area

Madison mylonite zone—Dotted where concealed

Folds—Dashed where approximately located; dotted where concealed. 

Showing trace of axial plane, direction of dip of limbs, and direction of 

plunge of axis

Anticline

Overturned anticline

Syncline

Overturned syncline

Monocline—Arrow points in direction of dip of beds. Only shown once in unit 

Mm in north-central part of map area

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGIC INVESTIGATIONS SERIES

I–2584 (SHEET 1 OF 2)

INTRODUCTION

The geology of Gallatin National Forest (GNF) was mapped as part of an 

evaluation of its mineral resource potential by the U.S. Geological Survey 

(USGS). Map A, the western part of GNF, south of Interstate Highway 90 (I90) and west of the Yellowstone River, includes the Gallatin and Madison 

Ranges and the West Yellowstone area. Map B, the northern part of GNF, 

north of I-90, includes the Bridger Range and Crazy Mountains. The eastern 

part of GNF, south of I-90 and east of the Yellowstone River, was examined 

previously by the USGS as part of the mineral resource potential study of the 

Absaroka-Beartooth study area and is published separately (Hammarstrom and 

others, 1993).

The colored maps of this report supersede a black-and-white version 

(Wilson and Elliott, 1995). Both maps were digitized, compiled, and produced 

using the USGS software program GSMAP (Selner and Taylor, 1993) and 

unreleased proprietary updates to it. All original source maps were digitized at 

their original scales and map projections, then merged into the final digital 

map formats. After editing, the digital maps were filtered to remove all points 

not necessary for improving resolution at a scale of 1:126,720 (2 mi per in., 

the scale used in this report and by the U.S. Forest Service).

Rocks range in age from Archean to Holocene. For purposes of 

resource assessment (Elliott and others, 1995), many rock units have been 

combined on these maps. Only brief descriptions of rock units are presented 

here; the reader is referred to original sources for detailed rock unit 

descriptions.

Base from U.S. Geological Survey, 1:100,000,

Ashton, Ennis, 1989; Bozeman, Gardiner, Livingston, 1992;

Hebgen Lake, 1993.

1927 North American Datum. Projection:

Universal Transverse Mercator, zone 12.

Geology compiled by Anna B. Wilson and James E. Elliott. 

See “Index to Sources of Geologic Mapping.”

Digital geology by Anna B. Wilson

Editing and digital cartography by Alessandro J. Donatich

Color design by Patricia L. Wilber and Anna B. Wilson

Manuscript approved for publication October 8, 1996

GEOLOGIC MAPS OF WESTERN AND NORTHERN PARTS OF 

GALLATIN NATIONAL FOREST, SOUTH-CENTRAL MONTANA

Compiled by

Anna B. Wilson and James E. Elliott

1997

MAP A. WESTERN PART OF GALLATIN NATIONAL FOREST

(GALLATIN AND MADISON RANGES AND WEST YELLOWSTONE AREA)

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

This map is also available as a PDF at http://greenwood.cr.usgs.gov

APPROXIMATE BOUNDARY OF

GALLATIN NATIONAL FOREST

CONTOUR INTERVAL 50 METERS

(Except Ashton quadrangle, contour interval 20 meters)

SUPPLEMENTARY CONTOUR INTERVAL 25 METERS IN HEBGEN LAKE QUADRANGLE

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Qs

Qr

QTf

Tt

Tv

Tc

Kda

Klv

Ku

Kul

Jdu

Pmu

Ps

hMu

Mm

MDt

Oeu

cgu

Au

Am

Ad

At

mi

Ti

Au



i15

i15

i90

i90 i90

i94

Gardiner

Billings

Big Timber

Livingston

Bozeman

Butte

Missoula

Great Falls

Yellowstone

National Park

West 

Yellowstone

GALLATIN AND MADISON RANGES 

AND WEST YELLOWSTONE AREA 

CRAZY

MOUNTAINS 

BRIDGER

RANGE

MONTANA

INDEX MAP

4

4

6

10

11

12

13

15 16

17 18 19 20

23

26

30

32

33

33

5

1

West

 Yellowstone

Bozeman Livingston

Gardiner

32

31

31

31

31

31

21

21

22

22

24 22

24

24

25

2

27

25

3

21

9

9

9

5

5

29

24

24

24

8

8

5

7

9

24

8

28

28

28

26

14

14

7

21

24 25

25

28

28

28

27

44°30'

45°

45°30'

111°30' 111° 110°30'

AREA OF MAP A

INDEX TO SOURCES OF GEOLOGIC MAPPING

SOURCES OF GEOLOGIC MAPPING

[The following sources were also consulted, but are not shown on the “Index to Sources of Geologic Mapping”: Fix (1940), Fraser and others (1969), 

Freeman and others (1950), Hamilton (1964), Pierce and others (1991), Richards (1957), Roberts (1972), Spencer and Kozak (1975), Swanson (1970), 

Tilley (1976), Todd (1969), and Tysdal and others (1986)]

 1 Adams, K.D., and Pierce, K.L., USGS, 1989?, unpublished map 17 Roberts (1964c)

compilation, scale 1:62,500. 18 Roberts (1964d)

 2 Becraft and others (1966) 19 Roberts (1964e)

 3 Bolm (1969) 20 Roberts (1964f)

 4 Chadwick (1982) 21 Simons and others (1985)

 5 Chadwick, R.A., Montana State University, year unknown, 22 Spencer and Kozak [1973 (1980)] 

unpublished mapping, approximate scale 1:48,000. 23 Sumner (1988)

 6 Christiansen, R.L., and Blank, H.R., Jr., USGS, 1975, unpublished 24 Tysdal and Simons (1985) 

mapping of West Yellowstone quadrangle, scale 1:62,500. 25 Tysdal (1990)

 7 Elliott, J.E., USGS, 1994, unpublished mapping of part of Tom 26 Tysdal (1966)

Miner basin area and Yankee Jim Canyon area, scale 1:24,000. 27 Tysdal, R.G., USGS, 1980–83, unpublished mapping of Big 

 8 Erslev (1981, 1983) Sky–Lone Mountain area, scale 1:62,500.

 9 Hall (1961) 27 Wilson, A.B., Hammarstrom, J.M., Van Gosen, B.S., and 

10 Kellogg (1995) Elliott, J.E., USGS, 1993, unpublished mapping of Big 

11 Kellogg, Karl, USGS, 1994, unpublished mapping of Willow Swamp Sky–Lone Mountain area, scale 1:24,000. 

quadrangle, scale 1:24,000. 28 U.S. Geological Survey (1964).

12 Kellogg (1993) 29 Van Gosen, B.S., USGS, 1993, unpublished mapping of part 

13 Kellogg, Karl, USGS, 1994, unpublished mapping of part of Beacon of Tom Miner basin area, scale 1:24,000.

Point quadrangle, scale 1:24,000. 30 Weber (1965)

14 McMannis and Chadwick (1964) 31 Wilson and Elliott (1995)

15 Roberts (1964a) 32 Witkind (1969)

16 Roberts (1964b) 33 Witkind (1972)

i90

2 1 0 2 4 6 8 10 12 14 KILOMETERS

SCALE 1:126 720

2 1 0 468 2 10 MILES

DESCRIPTION OF MAP UNITS

GALLATIN AND MADISON RANGES AND WEST YELLOWSTONE AREA

45°30'

45°15'

45°

44°45'

44°30' 44°30'

44°45'

45°

45°15'

45°30'

111°30' 111°15' 111° 110°45'

111°30'

111°15'

111° 110°45'

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey
Ta

Ta

Ta

Ti

Ti

Ta

Ti

Ti

TKf

TKf

TKf

TKf

TKf

TKf

Qs

Qs

Qs

Qs

Qs

Qs

Qs

Tdg

Tdg

Tcl

Tqm

TKf

Klv

TKf

Qs

TKf

TKf

Ta

Ti

Ti

Ti

Ti

Ti

Ta

Big Timber 

Tdg stock

DESCRIPTION OF MAP UNITS

BRIDGER RANGE

Surficial deposits, undivided (Quaternary)—Alluvium, colluvium, talus, 

landslide deposits, rock glaciers, and glacial and glaciofluvial deposits. Only selected major areas, generally exposed for at least 1 mi in a single direction, are shown

Fort Logan Formation (lower Miocene)—Sandy and conglomeratic tuffaceous 

siltstone with interbedded volcanic ash, freshwater gastropod limestone, and fossiliferous lenses of conglomerate and gravel. Coarse fractions mostly derived from Proterozoic Belt Supergroup and Paleozoic limestone. Shown only in extreme northeast corner of Bridger Range. Exposures more than 100 ft thick; actual thickness not measured (McGrew, 1977)

Intrusive rocks, undivided (Eocene)—Dacite, diorite, diabase, and basalt dikes 

and sills. Diorite dike in northern part of Bridger Range is olive-gray, coarsely crystalline, pyroxene phenocrysts (Skipp and Peterson, 1965); composite dike in southern part of range may be similar in composition (McMannis, 1955). Sills differentiated into upper syenite layer and lower layer of biotite-augite diorite. Thickness 80–200 ft (McMannis, 1955)

Fort Union Formation (Paleocene and Upper Cretaceous)—Cliff-forming, 

massive, nonmarine conglomerate, sandstone, and siltstone; conglomerate clasts derived from pre-Cretaceous rocks. Contains fossil spores, plants, wood, freshwater mollusks, and vertebrates. About 6,600 ft thick (Roberts, 1964b, c; 1972)

Livingston Group (Upper Cretaceous)—In descending order, includes 

Hoppers, Billman Creek, and Sedan Formations. Sedan Formation correlates with Miner Creek and Cokedale Formations, which are exposed in southernmost part of Bridger Range and in a narrow band extending to the east past Cokeville and Livingston (Skipp and McGrew, 1977). Livingston Group is volcaniclastic conglomerate, sandstone, and mudstone; and volcanic flows, sills, tuff, and breccia (Roberts, 1972). Hoppers Formation is purple-gray to gray-green, epiclastic volcanic sandstone, siltstone, mudstone, and conglomerate; 2,400 ft thick (Skipp, 1977). Billman Creek Formation is grayish-red, grayish-green, and gray volcanic mudstone and siltstone interbedded with minor volcanic sandstone, conglomerate, and vitric tuff. Includes freshwater gastropods and dinosaur bones (Skipp, 1977); 2,500–3,000 ft thick (Roberts, 1972; Skipp, 1977). Sedan Formation is primarily greenish-gray, epiclastic volcanic sandstone, mudstone, and conglomerate interbedded with mudflow conglomerate, welded tuff, devitrified silicified vitric tuff, bentonite, and lignitic coal (Skipp and McGrew, 1977). Freshwater mollusks, wood, and dinosaur bones present in upper part of Sedan Formation. Lower part contains ironstone nodules, magnetite-rich beds, volcanic granule-and-pebble conglomerate, and carbonaceous plant material. Lignite coal locally present at base. Sedan Formation about 3,000–4,500 ft thick (Skipp and McGrew, 1977)

Eagle Sandstone (Upper Cretaceous)—Upper part is gray, thin- to thickbedded, very fine grained to conglomeratic, largely calcareous, 

crossbedded sandstone; calcareous concretions and intercalated coal and shale. Lower part is massive, indurated, ledge-forming, crossbedded sandstone and greenish-gray and grayish-orange volcanic sandstone and conglomerate; intercalated coal, siltstone, and shale. Thickness 150–300 ft (Roberts, 1964a; Skipp, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965)

Upper Cretaceous sedimentary rocks, undivided—In descending order, 

includes Telegraph Creek Formation, Cody Shale, and Frontier Formation. Telegraph Creek Formation is predominantly gray, biotitic, silty shale that contains thin interbeds of fine-grained sandstone, limestone, and altered crystal vitric tuff. Upper part contains large calcareous cannonball concretions; lower part contains pelecypods and ammonites. About 285–400 ft thick (Roberts, 1964a; Skipp, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965). Cody Shale is darkgray shale and mudstone that contain thin interbeds of gray-green, glauconitic, calcareous to argillaceous, crosslaminated and rippled, fossiliferous (ammonites) sandstone and siltstone; ironstone nodules and cone-in-cone structures occur locally. About 600–1,100 ft thick (McGrew, 1977; Skipp, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965). Frontier Formation is mostly gray, green, or brown, thin- to medium-bedded, fine- to coarse-grained, calcareous to argillaceous, locally crosslaminated, ridge-forming sandstone; light-gray quartz, feldspar, and rock fragments contrast with dark-gray chert grains and give the sandstone a characteristic “salt-and-pepper” appearance. Contains interbeds of mudstone, siltstone, shale, quartzite, chert-pebble conglomerate, siliceous limestone, and fossil oyster banks; mudstone and siltstone intervals form valleys. About 500–700 ft thick (McGrew, 1977; Skipp, 1977; Skipp and Peterson, 1965)

Upper and Lower Cretaceous sedimentary rocks, undivided—In descending 

order, includes Mowry Shale (Upper Cretaceous) and Thermopolis Shale and Kootenai Formation (Lower Cretaceous). Mowry and Thermopolis Shales are dark-gray shaly mudstone and porcellanite interbedded with greenish-gray, medium-grained to very coarse grained, feldspathic, calcareous and argillaceous, thin-bedded sandstone; basal grayish-orange, ledge-forming quartzitic sandstone. Shales total about 600 ft thick (McGrew, 1977; Roberts, 1964a; Skipp, 1977; Skipp and Hepp, 1968). Kootenai Formation is red, gray, and purple hematitic mudstone interbedded with yellowish-gray and grayish-purple, quartzose, mediumto coarse-grained sandstone. Gray, nodular, gastropod-bearing, freshwater limestone common in upper part (about 100 ft below top) and just above basal ledge- and talus-forming, salt-and-pepper sandstone. Lenses of granule- to pebble-size chert conglomerate in basal sandstone. About 200–400 ft thick (McGrew, 1977; Skipp, 1977)

Jurassic sedimentary rocks, undivided—Includes Morrison Formation (Upper 

Jurassic) and underlying Ellis Group (Upper and Middle Jurassic). Ellis Group comprises Swift, Rierdon, and Sawtooth Formations; near Livingston the Sawtooth’s lithic equivalent is the Piper Formation. Morrison Formation is red, gray, and purple mudstone and hackly shale intercalated with light-gray, yellowish-brown, and yellowish-orange siltstone and sandstone, some conglomeratic; calcareous, quartzose, commonly crossbedded. Black shale near top; gray freshwater limestone in beds and nodules; thick red mudstone at base. About 200–400 ft thick (McGrew, 1977; Roberts, 1964a; Skipp and Hepp, 1968; Skipp and Peterson, 1965). Ellis Group is light-gray to light-brown, quartzose, calcareous, commonly iron stained sandstone and siltstone, interbedded with gray, fossiliferous, ledge-forming oolitic or sandy limestone and chert-pebble conglomerate. Basal bed grades from chert breccia or chertpebble conglomerate on the west to thin gray mudstone to fossiliferous limestone on the east. Thickness ranges from 2 to 213 ft (McGrew, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965)

Permian, Pennsylvanian, and Mississippian sedimentary rocks, 

undivided—In descending order, includes Phosphoria (Permian), 

Quadrant (Pennsylvanian), and Amsden (Lower Pennsylvanian and Upper Mississippian) Formations. Phosphoria Formation (McKelvey and others, 1959) (probably better correlated with Shedhorn Sandstone in this area) consists of a thin (no thicknesses given—presumably not more than several feet thick) section of phosphorite, phosphatic mudstone, carbonaceous mudstone, and chert (McKelvey and others, 1959); mapped with Quadrant Formation by Roberts (1964a, 1972). Quadrant Formation is well-sorted calcareous quartzite to quartzose sandstone; lightgray dolomite in lower part; lower part forms ledges. Thickness 0–150 ft 

(McGrew, 1977; Roberts, 1964a; Skipp and Hepp, 1968). Amdsen Formation is light-gray, weathering to white, thin- to thick-bedded dolomite. Interbeds of pale-grayish-orange sandstone and siltstone in upper part. Massive red sandstone, gray sandstone, siltstone, and mudstone, and red claystone interbedded with gray argillaceous limestone in lower part; dolomite-limestone breccia at base. About 250–600 ft thick (McGrew, 1977; Skipp and Hepp, 1968)

Madison Group (Mississippian)—Includes Mission Canyon Limestone and 

underlying Lodgepole Limestone. Mission Canyon Limestone is gray, aphanitic to medium-crystalline, cherty, massive, cliff-forming limestone and dolomite. Red-siltstone-filled cavernous zones, limestone breccia beds, and gray dolomite locally in upper part. About 700–1,200 ft thick (McGrew, 1977; Roberts, 1964a; Skipp, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965). Lodgepole Limestone is gray, thin- to medium-bedded, fossiliferous, locally cherty limestone and dolomite; weathers into platy blocks. Red and yellow silty limestone interbeds; thin dark-gray shale at base. Forms step-like ledges. About 500–750 ft thick (McGrew, 1977; Roberts, 1964a; Skipp, 1977; Skipp and Hepp, 1968; Skipp and Peterson, 1965)

Three Forks Formation (Lower Mississippian and Upper Devonian) and 

Jefferson Formation (Upper Devonian), undivided—Three Forks 

Formation is yellow calcareous siltstone, impure gray fossiliferous limestone, and dark-gray and green mudstone and shale. Thin beds of dolomite in upper part; olive-gray and reddish-brown, calcareous, fossiliferous shale in lower part. Thickness 150–200 ft (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965). Underlying Jefferson Formation is brownish- to olive-gray, thick-bedded to massive, sparsely fossiliferous, fetid dolomite and interbedded gray limestone; local stromatolites. About 400–600 ft thick (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965)

Cambrian sedimentary rocks, undivided—In descending order, includes 

Snowy Range Formation (and laterally equivalent Red Lion Formation) and Pilgrim Limestone (Upper Cambrian); and Park Shale, Meagher Limestone, Wolsey Shale, and Flathead Sandstone (Middle Cambrian). Locally may include Devonian Maywood Formation (McGrew, 1977), a red and yellow calcareous siltstone and gray dolomitic limestone (Skipp and Peterson, 1965). Snowy Range Formation is mainly limestone and shale distinguished by rounded limestone pebbles in the Grove Creek Limestone Member; underlain by thick red, gray, and green shale, gray limestone, and siltstone-pebble conglomerate of undivided lower members; bed of columnar limestone locally in lower part of formation (Roberts, 1964a; Skipp and Peterson, 1965). Combined thickness of Maywood and Snowy Range Formations 100–200 ft (Skipp and Peterson, 1965). Pilgrim Limestone is gray, thin-bedded to massive limestone and dolomite; forms cliffs. Oolites, grayish-orange and yellow mottling, and flat-pebble conglomerates are common. Interbeds of greenish-gray shale in lower part; glauconitic and fossiliferous at base. Thickness 350–500 ft (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965). Park Shale is grayish-green to multicolored clay shale; thin beds of argillaceous limestone, siltstone, and sandstone; sparse fossiliferous limestone and limestone-pebble conglomerate in upper part. Nonresistant; forms valleys. Thickness 100–200 ft (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965). Meagher (pronounced “mar”) Limestone is thin- to medium-bedded, mottled grayish-orange and medium-gray, fine-grained limestone and yellowish-gray dolomite; locally oolitic; crumpled bedding. Thickness 300–600 ft (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965). Wolsey Shale is olive- to brownish-gray micaceous clay shale; contains gray impure limestone in upper part and fine-grained, thin-bedded, glauconitic sandstone in lower part. Abundant trace fossils (“worm cast” markings). Forms valleys. Thickness 100–500 ft (Roberts, 1964a; Skipp and Peterson, 1965). Flathead Sandstone is yellowish-gray to reddish-gray, fine- to coarsegrained, thin- to thick-bedded, locally crossbedded quartzite and quartz sandstone. Locally conglomeratic in lower part. Very resistant; forms ridges. Thickness 0–300 ft (McGrew, 1977; Roberts, 1964a; Skipp and Peterson, 1965)

Middle Proterozoic metasedimentary rocks, undifferentiated—Includes the 

Spokane and underlying LaHood (formerly North Boulder Group) Formations of the Belt Supergroup. Spokane Formation is light-grayishgreen argillite, gray to yellowish-gray quartzite and sandstone, and minor thin-bedded grayish-red limestone; rippled beds are common. Thickness 2,200–3,200 ft (McGrew, 1977). LaHood Formation is dark-greenishgray, medium-grained to very coarse grained to conglomeratic, micaceous, feldspathic sandstone that contains interbedded dark-gray limestone and impure aphanitic laminated calcareous argillite; sandstone forms about 30 percent of sequence and is most common in upper part; limestone, with cone-in-cone structures, and argillite dominate lower part. More than 2,500 ft thick (Skipp and Peterson, 1965)

Metamorphic rocks (Archean)—Primarily gneiss. Includes schist, granite, 

quartzite, pegmatite, amphibolite, and mafic intrusive rocks (Roberts, 1964a)

CRAZY MOUNTAINS

Surficial deposits, undivided (Quaternary)—Alluvium, talus, rock glaciers, and 

glacial deposits. Only selected major areas, generally exposed for at least 1 mi in a single direction, are shown

Alkalic intrusive rocks (Eocene)—Mafic alkalic rocks (including malignite, 

nepheline syenite, analcite syenite, and theralite), trachyte porphyry, and related intrusive rocks. Typically these rocks are sodium rich, silica undersaturated, and strongly alkaline (Harlan, 1986). No plagioclase feldspar and calcic amphibole (Dudas, 1990). Includes dikes, sills, laccoliths, and small stocks

Intrusive rocks, undivided (Eocene)—Diorite, diabase, and fine-grained rocks 

ranging from basalt to rhyolite; includes dikes and sills. Commonly porphyritic; phenocryst composition ranges from 5 to 50 percent. Transitional between alkaline and calc-alkaline compositions. Probably genetically related to quartz monzodiorite phase of Big Timber stock (Tqm) (du Bray and others, 1993). Probably includes alkalic bodies (Ta) 

on west flank of Crazy Mountains and north of Shields River

Big Timber stock (Eocene)

Quartz monzodiorite phase—Quartz monzonite to granodiorite. Locally 

contains inclusions of diorite and gabbro (Tdg) along contact. Forms an 

irregular-shaped mass at center of Big Timber stock (du Bray and others, 1993). 40Ar/39Ar ages on biotite: 49.23

±0.1 and 49.33

±0.12 Ma 

(S.S. Harlan, USGS, unpub. data, 1996)

Diorite and gabbro phase—Granular diorite and gabbro form main part of 

Big Timber stock. Locally contains stoped blocks of pyroxene-rich gabbro. Coarser grained and darker in color than quartz monzodiorite phase (Tqm) (du Bray and others, 1993). 40Ar/39Ar ages on biotite: 

49.2

±0.07 and 49.33

±0.11 Ma (S.S. Harlan, USGS, unpub. data, 

1996)

Porphyry of Campfire Lake (Eocene)—Quartz monzodiorite porphyry, 

compositionally similar to quartz monzodiorite phase of Big Timber stock (Tqm). Separated from main body of Big Timber stock by sedimentary 

rocks of Fort Union Formation (TKf). At southern end of area of 

outcrop, unit has a quenched appearance with plagioclase phenocrysts (2- to 5-mm long) in an aphanitic to glassy groundmass (du Bray and others, 1993)

Fort Union Formation (Paleocene and Upper Cretaceous)—Siltstone, 

mudstone, sandstone, and pebble conglomerate. Unit is mainly hornfels in a several-mile-wide aureole of contact metamorphism adjacent to Big Timber stock (du Bray and others, 1993). Near Livingston, 6,615 ft thick (Roberts, 1972)

Livingston Group (Upper Cretaceous)—Volcaniclastic conglomerate, 

sandstone, and mudstone; tuff and volcanic breccia. Contains flows and sills (Roberts, 1972). Thickness 6,455 ft (Roberts, 1972)

Contact—Dashed where approximately located; dotted where concealed

Normal fault—Dashed where approximately located; dotted where concealed. 

Ball and bar on downthrown side where direction of movement is known. Opposed arrows indicate sense of lateral displacement where known

Thrust fault—Dashed where approximately located; dotted where concealed. 

Sawteeth on upper plate. Opposed arrows show sense of lateral displacement

Décollement—Paleocene plane of sliding. Shown only at north end of Bridger 

Range

Folds—Dashed where approximately located; dotted where concealed. 

Showing trace of axial plane, direction of dip of limbs, and direction of plunge of axis

AnticlineOverturned anticlineSynclineOverturned syncline

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Geological Survey Miscellaneous Geologic Investigations Map I–397, scale 1:24,000.

———1964b, Geologic map of the Bozeman Pass quadrangle, Montana: U.S. Geological 

Survey Miscellaneous Geologic Investigations Map I–399, scale 1:24,000.

———1964c, Geologic map of the Mystic Lake [Mount Ellis] quadrangle, Montana: U.S. 

Geological Survey Miscellaneous Geologic Investigations Map I–398, scale 1:24,000.

———1964d, Geologic map of the Maxey Ridge quadrangle, Montana: U.S. Geological 

Survey Miscellaneous Geologic Investigations Map I–396, scale 1:24,000.

———1964e, Geology of the Chimney Rock quadrangle, Montana: U.S. Geological Survey 

Geologic Quadrangle Map GQ–257, scale 1:24,000.

———1964f, Geology of the Brisbin quadrangle, Montana: U.S. Geological Survey 

Geologic Quadrangle Map GQ–256, scale 1:24,000.

———1964g, Geology of the Hoppers quadrangle, Montana: U.S. Geological Survey 

Geologic Quadrangle Map GQ–258, scale 1:24,000.

———1966, Geology and coal resources of the Livingston Coal Field, Gallatin and Park 

Counties, Montana: U.S. Geological Survey Professional Paper 526–A, 56 p.

———1972, Cretaceous and early Tertiary depositional and tectonic history of the 

Livingston area, southwestern Montana: U.S. Geological Survey Professional Paper 526–C, 120 p.

Selner, G.I., and Taylor, R.B., 1993, System 9, GSMAP, and other programs for the IBM 

PC and compatible microcomputers, to assist workers in the earth sciences: U.S. Geological Survey Open-File Report 93–511, 363 p., 2 diskettes.

Simms, F.E., Jr., 1966, The igneous petrology, geochemistry and structural geology of part 

of the northern Crazy Mountains, Montana: Cincinnati, Ohio, University of Cincinnati Ph.D. dissertation, 339 p.

Simons, F.S., Van Loenen, R.E., and Moore, S.L., 1985, Geologic map of the Gallatin 

Divide Roadless Area, Gallatin and Park Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF–1569–B, scale 1:62,500, 1 sheet.

Skipp, Betty, 1977, Geologic map and cross section of the Wallrock quadrangle, Gallatin 

and Park Counties, Montana: U.S. Geological Survey Geologic Quadrangle Map GQ–1402, scale 1:24,000, 1 sheet.

Skipp, Betty, and Hepp, Mary-Margaret, 1968, Geologic map of the Hatfield Mountain 

quadrangle, Gallatin County, Montana: U.S. Geological Survey Geologic Quadrangle Map GQ–729, scale 1:24,000, 1 sheet.

Skipp, Betty, and McGrew, L.W., 1977, The Maudlow and Sedan Formations of the Upper 

Cretaceous Livingston Group on the west edge of the Crazy Mountains basin, Montana: U.S. Geological Survey Bulletin 1422–B, 68 p.

Skipp, Betty, and McMannis, W.J., 1971, Geologic map of the Sedan quadrangle, Gallatin 

and Park Counties, Montana: U.S. Geological Survey Open-File Report 71–264, 2 sheets, scale 1:48,000.

Skipp, Betty, and Peterson, A.D., 1965, Geologic map of the Maudlow quadrangle, 

southwestern Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map I–452, scale 1:24,000, 2 sheets.

Spencer, E.W., and Kozak, S.J., 1973 (1980), Geology of the Spanish Peaks area of the 

Madison Mountains, Montana: Montana Bureau of Mines and Geology Open File Report 55, 99 p., 20 figs., 3 tables, 1 sheet, scale approx. 1:62,500.

———1975, Precambrian evolution of the Spanish Peaks area, Montana: Geological 

Society of America Bulletin, v. 86, p. 785–792.

Starmer, R.J., 1972, The distribution and geochemistry of the Big Timber dike swarm, 

Crazy Mountains, Montana: Cincinnati, Ohio, University of Cincinnati Ph.D. dissertation, 90 p.

Sumner, W.R., 1988, Structural geology and tectonic setting of the Cherry Creek 

metamorphic suite, southern Madison Range: Fort Collins, Colo., Colorado State University M.S. thesis, 128 p.

Swanson, R.W., 1970, Mineral resources in Permian rocks of southwest Montana: U.S. 

Geological Survey Professional Paper 313–E, p. 661–777.

Tappe, John, 1966, The chemistry, petrology, and structure of the Big Timber igneous 

complex, Crazy Mountains, Montana: Cincinnati, Ohio, University of Cincinnati Ph.D. thesis, 134 p.

Tilley, C.W., 1976, Geology of the Spanish Creek basin area, Madison and Gallatin 

Counties, Montana: Bozeman, Mont., Montana State University M.S. thesis, 111 p.

Todd, S.G., 1969, Bedrock geology of the southern part of Tom Miner basin, Park and 

Gallatin Counties, Montana: Bozeman, Mont., Montana State University M.S. thesis, 63 p.

Tysdal, R.G., 1966, Geology of a part of the north end of the Gallatin Range, Gallatin 

County, Montana: Bozeman, Mont., Montana State University M.S. thesis, 187 p., 1 plate, scale 1:24,000.

———1990, Geologic map of the Sphinx Mountain quadrangle and adjacent parts of the 

Cameron, Cliff Lake, and Hebgen Dam quadrangles, Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I–1815, scale 1:62,500, 1 sheet.

Tysdal, R.G., Marvin, R.F., and DeWitt, Ed, 1986, Late Cretaceous stratigraphy, 

deformation, and intrusion in the Madison Range, southwestern Montana: Geological Society of America Bulletin v. 97, p. 859–868.

Tysdal, R.G., and Simons, F.S., 1985, Geologic map of the Madison Roadless Area, 

Gallatin and Madison Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF–1605–B, scale 1:96,000.

U.S. Geological Survey, 1964, The Hebgen Lake, Montana, earthquake of August 17, 

1959: U.S. Geological Survey Professional Paper 435, 242 p., plate 5, scale 1:62,500.

Weber, W.M., 1965, General geology and geomorphology of the Middle Creek area, 

Gallatin County, Montana: Bozeman, Mont., Montana State University M.S. thesis, 86 p.

Weed, W.H., 1899, Description of the Little Belt Mountains quadrangle, Montana: U.S. 

Geological Survey Geologic Atlas, Folio 56, scale 1:250,000.

Wilson, A.B., and Elliott, J.E., 1995, Digital geologic maps of the northern and western 

Gallatin National Forest, Montana—Digital and hard copy formats: U.S. Geological Survey Open-File Report 95–11 A and B, 2 p., 1 diskette, scale 1:126,720.

Witkind, I.J., 1969, Geology of the Teepee Creek quadrangle, Montana-Wyoming: U.S. 

Geological Survey Professional Paper 609, 101 p., scale 1:62,500.

———1972, Geologic map of the Henrys Lake quadrangle, Idaho and Montana: U.S. 

Geological Survey Miscellaneous Investigations Series Map I–781–A, scale 1:62,500.

Qs Qs

Tfl

Ti

Ti

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Tqm

Tdg

Ta

TKf TKf

Klv Klv

Ke

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PMu

Mm

MDt

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QUATERNARY

TERTIARY

lower

Miocene

EocenePaleocene

Upper

Cretaceous

Lower Cretaceous

Upper and 

Middle Jurassic

Upper

Mississippian

Lower

Mississippian

Upper Devonian

Upper and

Middle Cambrian

Middle

Proterozoic

CRETACEOUSJURASSICPERMIANPENNSYLVANIANMISSISSIPPIANDEVONIANCAMBRIANPROTEROZOICARCHEAN

UnconformityUnconformityUnconformityUnconformityUnconformityUnconformityUnconformityUnconformityUnconformityUnconformity

CORRELATION OF MAP UNITS

BRIDGER RANGE CRAZY MOUNTAINS

GEOLOGIC INVESTIGATIONS SERIES

I–2584 (SHEET 2 OF 2)

Any use of trade names in this publication is fordescriptive purposes only and does not imply endorsement by the U.S. Geological SurveyFor sale by U.S. Geological Survey Information ServicesBox 25286, Federal Center, Denver, CO 80225This map is also available as a PDF at http://greenwood.cr.usgs.gov

 NATIONAL FOREST, SOUTH-CENTRAL MONTANA

iott

TIONAL FOREST

NTAINS)

12 14 KILOMETERS

8 

10 MILES

Geology compiled by Anna B. Wilson and James E. Elliott. See “Index to Sources of Geologic Mapping.”Digital geology by Anna B. WilsonEditing and digital cartography by Alessandro J. DonatichColor design by Patricia L. Wilber and Anna B. Wilson

PROXIMATE BOUNDARY OF

ALLATIN NATIONAL FOREST

Livingston

2

2 2

6 7

8

10

12

1414

15

16

8

16

17

17

1

1

9

1

110°30' 110°

REA OF MAP B

TO SOURCES OF GEOLOGIC MAPPING

SOURCES OF GEOLOGIC MAPPING

[The following sources were also consulted, but are not shown on the “Index to Sources of Geologic Mapping”: Dudas (1990, 1991), Harlan (1986), Lageson and Skipp (1994), Merewether (1960), and Skipp and McGrew (1977)]

1 du Bray and others (1993) 9 Simms (1966)2 Iddings and Weed (1894) 10 Skipp (1977)3 McGrew (1977) 11 Skipp and Hepp (1968)4 McKelvey and others (1959) 12 Skipp and McMannis (1971)4 McMannis (1955) 13 Skipp and Peterson (1965)5 Roberts (1964a) 14 Starmer (1972)6 Roberts (1964b) 15 Tappe (1966)7 Roberts (1964g) 16 Weed (1899)8 Roberts (1972) 17 Wilson and Elliott (1995)

i90

90

90 90

94

Gardiner

Billings

Big Timber

Livingston

Bozeman

Butte

Missoula

Great Falls

Yellowstone

National Park

West Yellowstone

GALLATIN AND MADISON RANGES AND WEST YELLOWSTONE AREA 

CRAZYMOUNTAINS 

BRIDGERRANGE

MONTANA

INDEX MAP

i

i15

i15

i

i

i

Qs

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TKfKlv

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MmMDt

eu

Ym

AmQs

Ta

Tqm

Tdg

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Ti

Tcl

Tcl

110°30' 110°15'

46°15'46°

110°30' 110°15'