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SAN JUAN CALDERA

TOPOGRAPHIC MARGIN

Maggie

Gulch

Gulch

Minnie

Animas

River

Gulch

Edith

Eureka

Howardsville

Silverton

SILVERTON CALDERA

STRUCTURAL MARGIN

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Gulch

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Gulch

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Mountain

Niagara

Gulch

Hancock Gulch

Browns

Gulch

Topeka

Gulch

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Gulch

Mineral

Creek

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Creek Chattanooga

Minnesota

Gulch

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Gulch

Cascade

Gulch

Grassy

Gulch

Illinois

Gulch

Storm

Peak

Boulder

Gulch

Tower

Mountain

Macomber

Peak

Cataract

Gulch

Hematite

Gulch

Gulch

Porphyry

Big

Horn

Gulch

Mineral

Creek

Red Mtn

No. 2

Red Mtn

No. 3

Red

Mtn

Red Mtn

No. 1

Georgia

Gulch

McMillan

Peak

Tiger

Gulch

Prospect Gulch

Dry

Gulch

Cement

Creek

South

North

Fork

Cement

Creek

Fork

Middle

Fork

Minnehaha Creek

South Fork

Animas River

Eureka

Gulch

Emery

Peak

Bonita

Peak

Parson

Gulch

Eureka

Mtn

Hurricane

Peak

California

Mtn Treasure

Mtn

Picayune

Gulch

Burns

Gulch

California

Gulch

Placer

Gulch

Grouse

Gulch

Cinnamon

Mtn

Animas Forks

Animas

River

Cinnamon

Creek

Houghton

Mtn

ROSS

BASIN

FAULT

SUNNYSIDE

FAULT

TOLTEC

FAULT

BONITA

FAULT

Abrams

Mountain

Ohio

Peak

Kendall

Peak

Hazelton

Mtn

Ohio Gul

ch

Approximate 

area of figure 1

NEW MEXICO

UTAH

COLORADO

109° 106° 39°

37°

Montrose

Durango

Ouray

Creede

Gunnison

Silverton

COLORADO

0 100 KILOMETERS0 62 MILES

COLORADO

Area of

index map

b

co

g sl

c

ba

sm

p

u ll

un

lc

sr

s

sj b

Quaternary-Tertiary sedimentsTertiary intrusionsTertiary volcanic rocksMesozoic and Paleozoic sedimentary rocksPrecambrian rocksCalderas of San Juan volcanic field

—b, Bonanza;

ba, Bachelor; c, Creede; co, Cochetopa; g, La Garita;lc, Lake City; ll, Lost Lake; p, Platoro; s, Silverton; 

sj, San Juan; sl, San Luis; sm, Summitville;

sr, South River; u, Ute Creek; un, Uncompahgre

EXPLANATION

Modified from Casadevall and Ohmoto (1977)

REGIONAL INDEX MAP

Silverton

Cement Ck

Mineral Ck

Animas R

?

?

107°50' 107°45' 107°40' 107°35' 107°30'

38°00'37°55'37°50'37°45'

EXPLANATION

Late Tertiary intrusive rocksTertiary volcanic rocksTertiary and Late Cretaceous intrusive rocksMesozoic and Paleozoic sedimentary rocksPrecambrian rocksContactFaults and vein structures—Dashed where 

approximately located

Silverton caldera structural margin—Dotted 

where concealed

San Juan caldera topographic margin— 

Approximately located; queried where extent uncertain

Figure 1. Generalized regional geologic map of part of the Animas River watershed and surrounding regions. Major tributaries to the Animas 

River are shown in addition to the major Tertiary volcano-tectonic structures related to the Silverton and San Juan calderas. Figure is modified from Casadevall and Ohmoto (1977).

0 6 MILES0 9 KILOMETERS

107°52'30"107°52'30" 107°45'00"

37°52'30"37°45'00"

107°37'30" 

107°45'00" 107°37'30" 

38°00'00" 

COLORADO

MAP LOCATION

5 KILOMETERS 1 .5 0 1 2 3 4

SCALE 1: 48 000

CONTOUR INTERVAL 40 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

4 MILES 1 0 1 2 3 1/ 2

GENERALIZED GEOLOGIC MAP OF PART OF THE ANIMAS RIVER WATERSHED AND VICINITY, SILVERTON, COLORADO

Compiled by

Douglas B. Yager and Dana J. Bove

2007

U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

Base from U.S. Geological Survey, 1:24,000, Handies Peak, Howardsville, Ironton,Ophir, Silverton (1955). Projection: Universal Transverse Mercator, zone 13.10,000-foot grid based on Coloradocoordinate system, south zone.1927 North American datum

Geo

See index map at right