U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004–3050

May 2004 Printed on recycled paper

The 57,725-acre Gunnison Gorge National Conservation 

Area (hereafter referred to as the NCA) was created by Congress 

in 1999 and is administered by the U.S. Bureau of Land Management (BLM). The NCA is the downstream continuation of Black 

Canyon of the Gunnison National Park. Unlike the almost inaccessible depths of the Gunnison River canyon within the National 

Park, several good hiking trails provide access to the canyon 

within the NCA. It is one of the most beautiful and accessible 

wild areas to be found in the United States. Every year the gorge 

attracts over 10,000 visitors, who explore its depths and the surrounding hills by foot, horseback, mountain bike, kayak, and raft. 

Towering cliffs, quiet riverside glens, cascading rapids, winding 

trails with spectacular canyon views—these are just a few of the 

features enjoyed by visitors to the NCA.

Much of the attraction of the NCA is due to the spectacular geologic formations, which document a geological history that

extends to more than a third of the age of the Earth itself.

This fact sheet shows not only some of these geological

 features, but highlights some of the more

 interesting ecological and 

 human-interest aspects of 

 the Gunnison River

 gorge.

The fascinating geologic story of the Gunnison River gorge is

too complicated to describe in detail in this fact sheet. However, this 

story is told in a separate, companion book, “The Geologic Story of 

Gunnison Gorge National Conservation Area, Colorado” (Kellogg, 

in press). For the purposes of this fact sheet, the geology is briefly 

described here.

The oldest rocks in the gorge are the ancient basement rocks that 

make up the mostly steep, dark-colored walls beneath horizontal layers of 

sedimentary rock. These basement rocks were formed by igneous and metamorphic processes deep in the Earth’s crust during the Proterozoic Eon, 

approximately 1.7–1.4 billion years ago. Examples of metamorphic rocks 

in the gorge are quartzitic gneiss, mica schist, amphibolite, and migmatite. 

Within the NCA, coarse-grained Pitts Meadow Granodiorite intruded these 

ancient metamorphic rocks. In addition, many light-colored dikes and 

irregular masses of coarse-grained pegmatite form a conspicuous network 

of igneous intrusions throughout the canyon. 

A tremendous period of time—over 1.5 billion years—transpired 

between the formation of the basement rocks and the deposition of the 

oldest sedimentary rocks that rest on them. We know that several periods 

of uplift and erosion took place during this long intervening period. A 

relatively good geologic record exists for the period of uplift that resulted 

in the ancestral Uncompahgre uplift, one of several mountainous areas in 

the Rocky Mountain region that rose about 300 million years ago. Erosion 

that followed the uplift denuded the region of the 550–300-million-year-old 

rocks that had been deposited before uplift. The oldest sedimentary rocks 

that remain on the ancient eroded basement surface are 190 million years 

old. A younger period of uplift and major mountain building, called the 

Laramide orogeny, occurred about 70–50 million years ago and formed the 

pattern of ranges of the present Rocky Mountains. 

Geologyof Gunnison Gorge National Conservation Area,

of Gunnison Gorge National Conservation Area,of Gunnison Gorge National Conservation Area,of Gunnison Gorge National Conservation Area,of Gunnison Gorge National Conservation Area,

Geologyof Gunnison Gorge National Conservation Area,Geology

Delta and Montrose Counties, Colorado

Prepared in cooperation with

The U.S. Bureau of Land Management

of Gunnison Gorge National Conservation Area,of Gunnison Gorge National Conservation Area,of

(RIGHT) The Boulder Garden, a class III–IV 

rapids, contains large blocks of dark Pitts 

Meadow Granodiorite (Xpmd).

Two lizards sunning themselves on an outcrop of migmatitic biotite 

gneiss (Xmg) in the canyon of Smith Fork. The distance between the 

lizards is about one foot (30 cm).

T

Introduction

The fascinating geologic story of the Gunnison River gorge is

Geology
fault

Ute 

Indian

Je

Jms

Jmb

Jmt

Grand Mesa

Jw

Kb

Jmb

Jms

Jmt

Je Jw

fault

Ute 

Indian

Je

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Grand Mesa

Jw

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The oldest sedimentary rocks in the NCA form the Middle Jurassic Entrada Sandstone, which is composed of pink to yellowish-orange, 

cross-bedded sandstone that accumulated as ancient sand dunes. Overlying the Entrada are mudstone, sandstone, and gypsum of the Middle 

Jurassic Wanakah Formation, which were deposited in a closed, shallow 

inland sea. With time, the land was slowly uplifted and the sea retreated. 

The sea-floor sediments were then buried by sand and mud deposited in 

coastal lakes and rivers, and those sediments now form the multicolored 

sandstone and shale beds of the Upper Jurassic Morrison Formation. 

The basal part of the Morrison Formation is called the Tidwell Member, 

which contains some gypsum beds, indicating that shallow, enclosed seas 

periodically covered the land during deposition of the Tidwell.

Overlying the Tidwell Member is the Salt Wash Member of the 

Morrison Formation, which contains cross-bedded, red-stained (from 

the overlying reddish shale), fluvial (deposited in rivers) sandstone beds 

and interbedded shale. Overlying the Salt Wash Member are colorful 

red, green, and gray shales and thin sandstone beds of the upper Brushy 

Basin Member of the Morrison, which are host to some world-famous 

dinosaur-bone localities outside the NCA.

A gap exists in the geologic record following the deposition of the Morrison Formation. This gap was a time when there was either no deposition 

of sedimentary or volcanic rocks, or possibly such rocks were deposited, 

but they were eroded away. Such a gap in the geologic record is called an 

unconformity. The rocks above the unconformity are fluvial deposits of the 

Lower Cretaceous Burro Canyon Formation, which form thick beds of cliffforming, light-brown, quartz sandstone with interbedded shale and chertpebble conglomerate. Above the Burro Canyon Formation, thin beds of 

quartz sandstone, shale, and coal in the Lower to Upper Cretaceous Dakota 

Formation record a time when rivers and swamps deposited sand, mud, and 

decaying plant material along a tropical marine shoreline. 

Once again, the sea gradually covered the land, and earlier deposits 

of sand of the Dakota Formation were buried by thick deposits of marine 

mud of the Upper Cretaceous Mancos Shale, which now form a gray 

badlands landscape of weathered shale and mudstone in the southwestern 

and western parts of the NCA. The Mancos Shale is the youngest consolidated bedrock formation exposed in the NCA. Much younger, mostly 

uncemented Quaternary surface deposits, such as alluvium, terrace gravels, landslide deposits, and talus, cover large areas of the NCA.

Ute Indian fault: a Spectacular Laramide Feature

The Gunnison River gorge contains one of the most spectacularly 

exposed faults in Colorado—the Ute Indian fault. It is magnificently 

displayed along part of the gorge. The Ute Indian fault formed during a 

period of great mountain building called the Laramide orogeny, which 

began near the end of the Cretaceous Period (about 70 million years 

ago) and lasted about 20 million years into early Tertiary time. During 

the Laramide orogeny, the present Rocky Mountains formed, although 

the mountains have subsequently been greatly modified by erosion, 

volcanic activity, faulting, and additional uplift. The Gunnison River 

cuts through the middle of the Gunnison uplift, one of a number of 

highlands that rose during the Laramide orogeny. 

The Ute Indian fault is a north-trending thrust fault that dips (is 

inclined) about 40o to the west. During the Laramide orogeny, Proterozoic basement rocks were shoved up and to the east along the Ute 

Indian fault by as much as 1,150 feet (350 meters) vertically above 

Jurassic sedimentary rocks. 

The fault is clearly exposed in Chukar Canyon and generally follows 

the gorge northward, crossing the Gunnison River at several places. At 

both its south and north ends, displacement on the fault dies out.

Why does the Gunnison River cut through the center 

of the Gunnison uplift and not around it? Two interesting 

geologic relationships have been proposed to explain 

this paradox. First, the Gunnison uplift was mostly 

buried by enormous outpourings of ash-flow tuff and 

volcanic breccia during huge Tertiary volcanic eruptions 

that originated from two nearby volcanic centers in the 

San Juan and West Elk Mountains. These eruptions, as 

well as a broad, late Tertiary downwarped area (Hansen, 

1987), confined the Gunnison River to a course across 

the buried Gunnison uplift.

Second, rapid lowering of base level (the lowest level 

to which a river can erode) during Tertiary and continuing into Holocene time (refer to Kellogg, in press, for 

how this occurred) caused the Gunnison River to cut 

rapidly into the thick accumulation of volcanic rocks 

(as well as the soft Mancos Shale), exhuming the buried 

Gunnison uplift. The Gunnison River was confined to 

the established channel within the volcanic rocks, so 

it continued to erode downward where it was—right 

into the hard rocks of the Gunnison uplift. This process, 

whereby a river crossing one type of rock erodes over 

time into an entirely different, much harder rock, is 

called stream superimposition (that is, the stream is 

superimposed on the underlying harder rocks).

(ABOVE) View to the north showing the Ute Indian fault. Je, Entrada Sandstone; Jw, Wanakah 

Formation; Jmt, Tidwell Member of the Morrison Formation; Jms, Salt Wash Member of the 

Morrison Formation; Jmb, Brushy Basin Member of the Morrison Formation; Kb, Burro Canyon 

Formation. Note how the down-to-the-east displacement across the fault dies out to the north, 

such that the beds of unit Jmt are folded but not broken by the fault. Where formation and 

member contact lines are dashed, and where the Ute Indian fault is dashed, indicates that 

these features are approximately located or concealed.

On the geologic map in this fact sheet, the Wanakah Formation and the Tidwell Member of the 

Morrison Formation are combined as one map unit (labeled Jmtw), the Salt Wash and Brushy 

Basin Members of the Morrison Formation are combined as one unit (labeled Jmu), and the 

Burro Canyon Formation and Dakota Formation are combined as one unit (labeled Kdb). They 

are combined, because at the scale (size) of the geologic map, these units would be too thin to 

show separately.

(BELOW) Panoramic view downriver toward Ute Park.

The Gunnison River 

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Geologic map of Gunnison Gorge National Conservation Area 

and vicinity. Geology compiled and modified by Karl Kellogg from 

Hansen (1968, 1971) and Ellis and others (1987). Shaded-relief base 

created by D. Paco VanSistine in 2003. See Kellogg and others (in 

press) for a large, detailed version of this map.
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The earliest known inhabitants or visitors to the canyon were 

prehistoric Native Americans who camped and hunted in the area. 

Petroglyphs and rock structures that were constructed without mortar 

are scattered throughout the canyon. Clovis and Folsom spear points 

have been found in the Uncompahgre River valley, indicating that 

the region has been inhabited for at least 10,000–11,000 years. More 

recently, until historic times, mountain-dwelling Utes traversed the 

canyon’s depths. 

The Gunnison River is named after John William Gunnison, who 

led an expedition through the region in 1854 to survey a railroad route 

from the Mississippi River to the Pacific Ocean. The Black Canyon of 

the Gunnison understandably caused the 

expedition to make a large detour and 

led Gunnison to conclude that a railroad 

could be constructed through the region 

only “at an enormous expense.”

Few people have lived permanently 

in the canyon. During the Depression 

years, John Howell from Olathe built 

several cabins and eked out a living 

prospecting for gold and mining mica 

from pegmatite deposits in the Ute Park 

area. The Duncan brothers also prospected in the canyon at about the same 

time; the ruins of their stone cabin and 

a prospect tunnel are at the base of the 

Duncan Trail. 

Index map showing location of the Gunnison Gorge National Conservation Area and Black 

Canyon of the Gunnison National Park. Major roads are shown in brown.

“Howell Village,” the remains of John Howell’s cabins 

built during the 1930s just north of Ute Park. Howell 

was a prospector who lived in the canyon during the 

Great Depression.

List of Geologic Map Units

Name of geologic map unit and geologic age of unit

are shown

The earliest known inhabitants or visitors to the canyon were 

Humans an umans and the Canyon
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Farther back from the river is a semi-arid environment containing juniper, scrub oak, mountain mahogany, grasses, 

Mormon tea, occasional cactus, and other plants. Pinon-juniper forests and open sagebrush parks mark the higher regions 

of the NCA. The western and southern regions of the NCA are underlain by nutrient-poor Mancos Shale, which forms a 

barren landscape with sparse vegetation. Some of the plants found here, such as a clay-loving species of buckwheat, 

are endangered and are found only in Mancos Shale soils.

The NCA is the home of a wide variety of wildlife, including mule deer, elk, Rocky Mountain bighorn sheep 

(reintroduced in 1986), mountain lions, bobcats, black bears, coyotes, foxes (both red fox and the diminutive kit fox), 

river otters (also reintroduced in 1986), and a variety of snakes and lizards. Birds of prey include peregrine 

and prairie falcons, kestrels, golden eagles, ospreys, 

red-tailed hawks, and occasional bald eagles. A small 

population of turkey vultures also inhabits the area. 

Many other bird species are either

residents of the canyon or are seasonal

visitors. The Gunnison River is

considered a “gold-medal” trout

stream and contains introduced

eastern brook, German brown, and rainbow

trout, as well as northern pike. Certain native warmwater species, such as the humpback chubb, and 

pikeminnow, no longer inhabit the canyon. Native 

fish have had to compete with the non-native fish 

for food and habitat, and they have had to exist 

in water that is considerably colder than it was 

before the early 1960s, when three upstream dams 

(Crystal, Morrow Point, and Blue Mesa) were 

built. Water from these dams is released from the 

deepest and coldest parts of these reservoirs and 

provides ideal habitat for the canyon’s excellent trout fishery, but has proved deadly for most 

native warm-water species.

The canyon has a variety of ecological environments. Riparian 

habitats along the river corridor are host to cottonwoods, box elder, 

willows, patches of poison ivy, and other water-loving plants. In 

addition to these native plants, tamarisk (salt cedar), an introduced 

water-loving species, is making inroads along the riverbank. The BLM 

has launched an aggressive tamarisk-control program to rid the NCA of 

this threat to native plant communities.

Rocky Mountain bighorn sheep.

The canyon has a variety of ecological environments. Riparian 

Ecology of the Canyon
Thanks to Bruce “Rooster” Barnhart, who ably guided the first author hanks to Bruce “Rooster” Barnhart, who ably guided the first author

through the canyon and provided valuable canyon lore. C.A. Finn and 

J.A. Karson offered sound geologic feedback in the field, and D.W. 

Moore, R.B. Scott, R.I. Grauch, and W.C. Day improved the geologic 

map and fact sheet greatly with thorough reviews. R.G. Waltermire provided the preliminary geologic base from maps digitized by the U.S. Park 

Service. Julie Coleman commented on the human history of the canyon.

Ellis, M.S., Gaskill, D.L., and Dunrud, C.R., 1987, Geologic map of the Paonia 

and Gunnison area, Delta and Gunnison Counties, Colorado: U.S. Geological 

Survey Coal Investigations Map C–109, scale 1:100,000.

Hansen, W.R., 1968, Geologic map of the Black Ridge quadrangle, Delta and 

Montrose Counties, Colorado: U.S. Geological Survey Geologic Quadrangle 

Map GQ–747, scale: 1:24,000.

Hansen, W.R., 1971, Geologic map of the Black Canyon of the Gunnison River 

and vicinity, western Colorado: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–584, scale 1:31,680.

Hansen, W.R., 1987, The Black Canyon of the Gunnison—in depth: Tucson, 

Arizona, Southwest Parks and Monuments Association, 58 p.

Kellogg, K.S., in press, The geologic story of Gunnison Gorge National Conservation Area, Colorado: U.S. Geological Survey Professional Paper 1699.

Kellogg, K.S., Hansen, W.R., Tucker, K.S., and VanSistine, D. Paco, in press, 

Geologic map of Gunnison Gorge National Conservation Area, Delta and 

Montrose Counties, Colorado: U.S. Geological Survey Scientific Investigations Map 2825, scale 1:45,000.

O’Sullivan, R.B., 1992, The Jurassic Wanakah and Morrison Formations in the 

Telluride-Ouray-western Black Canyon area of southwestern Colorado: U.S. 

Geological Survey Bulletin 1927, 24 p. 

By

Karl S. Kellogg,1 Wallace R. Hansen,1 Karen S. 

Tucker,2 and D. Paco VanSistine1

1U.S. Geological Survey

2U.S. Bureau of Land Management

Contacts

Karl S. Kellogg

U.S. Geological Survey MS 980

P.O. Box 25046

Denver, CO 80225

kkellogg@usgs.gov

Karen S. Tucker

U.S. Bureau of Land Management

Gunnison Gorge National Conservation Area

2465 South Townsend Avenue

Montrose, CO 81401

karen_tucker@co.blm.gov

This fact sheet is available online at

http://pubs.usgs.gov

Edited by F. Craig Brunstein

Publication design, digital layout,

and original drawings by

Carol Quesenberry

Map cartography and map color

design by Bill Sowers

Photographs by U.S. Geological Survey

and U.S. Bureau of Land Management 

Running the river, just below the Chukar 

Canyon launch site. The light-colored rocks 

are dikes of coarse-grained pegmatite (YXp)

cutting layered quartzitic gneiss (Xlq). View is 

toward the northwest.

Prickly pear cactus 

(Opuntia phaeacantha).

Thanks to Bruce “Rooster” Barnhart, who ably guided the first author

Acknowledgments

Ellis, M.S., Gaskill, D.L., and Dunrud, C.R., 1987, Geologic map of the Paonia 

References and

Further Reading