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Park

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32 68

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28

40

28

25

EEL–1

27.3±

0.1 Ma

VASQUEZ PASS FAULT

SAINT

LOUIS

CREEK

FAULT

WRP 03–2

1,718.9± 8.5 Ma

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U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Base from U.S. Geological Survey, Fraser, 1957, 1:24,000. The base 

was modified by removing the obsolete name Hideaway Park, and 

replacing it with Winter Park. The name Winter Park Ski Area was 

added just to the west of West Portal

Polyconic projection. 1927 North American Datum

10,000-foot grid based on Colorado Coordinate System, north zone

1000-meter Universal Transverse Mercator grid ticks, zone 13

SCALE 1:24 000

1 1/ 2 0 1 MILE

1 .5 0 1 KILOMETER

CONTOUR INTERVAL 40 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929 

Geology mapped by P.K. Theobald in 1959–1963, Bruce Bryant 

in 1974 and 2005–2006, and R.R. Shroba in 2003 and 2005–2008

T.R. Brandt prepared the digital compilation of the geologic 

map and the GIS database.

Manuscript approved for publication June 9, 2010

COLORADO

QUADRANGLE LOCATION

TRUE NORTH

MAGNETIC NORTH

9°

APPROXIMATE MEAN

DECLINATION, 2008

SCIENTIFIC INVESTIGATIONS MAP 3130

Version 1.0

Pamphlet accompanies map

Publishing support provided by: 

Denver Publishing Service Center

For more information concerning this publication, contact:

Center Director

USGS Geology and Environmental Change Science Center

Box 25046, Mail Stop 980

Denver, CO 80225

(303)236-5344

Or visit the USGS Geology and Environmental Change Science Center 

site at: http://esp.cr.usgs.gov/ 

Suggested Citation:

Shroba, R.R., Bryant, Bruce, Kellogg, K.S., Theobald, P.K., and Brandt, 

T.R., 2010, Geologic map of the Fraser 7.5-minute quadrangle, Grand 

County, Colorado: U.S. Geological Survey Scientific Investigations 

Map 3103, 1 sheet, 26 p. pamphlet, scale 1:24.000. [Available at URL 

http://pubs.usgs.gov/sim/3130/ ].

This and other USGS information products are available at:

http://store.usgs.gov/

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit

http://www.usgs.gov/ 

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Any use of trade, product, or firm 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 for other than personal use

must be secured from the copyright owner. 

GEOLOGIC MAP OF THE FRASER 7.5-MINUTE QUADRANGLE, GRAND COUNTY, COLORADO

By

Ralph R. Shroba, Bruce Bryant, Karl S. Kellogg, Paul K. Theobald, and Theodore R. Brandt

2010

Holocene

Artificial fill

deposits

Alluvial

deposits

Alluvial and

mass-movement

deposits Mass-movement deposits

SURFICIAL DEPOSITS

BEDROCK UNITS

CORRELATION OF MAP UNITS

Pre-Laramide

sedimentary rocks

Unconformity

Unconformity

Unconformity

Proterozoic rocks

Glacial

deposits

Post-Laramide

sedimentary and

volcanic rocks

Pleistocene

Miocene

Oligocene

Pliocene

Lower Cretaceous

Upper Jurassic

Neogene

Paleogene

TERTIARY

CRETACEOUS

JURASSIC

MESOPROTEROZOIC

PALEOPROTEROZOIC

QUATERNARY

af Qva

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Qg2

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Qg7

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Qp2

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Qtb

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$t

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Jm

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Yp Ym

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? ? ? ?

? ? Qac ?

CONTINENTAL

DIVIDE

0

0 5

5 10 KILOMETERS

STRAWBERRY

LAKE

GRANBY

MONARCH LAKE

BOTTLE PASS

FRASER

EAST PORTAL

BYERS PEAK

BERTHOUD

PASS

EMPIRE

Granby

River

Fraser

Tabernash

Fraser

Winter

Park

Arapaho

Pass

Williams Fork

40°7’30’’

40°00’

106°00’ 105°52’30” 105°45’ 105°37’30”

39°45’

39°52’30”

)(

COLORADO RIVER

Berthoud

Pass

)(

Index. U.S. Geological Survey 7.5-minute maps adjacent to 

the Fraser quadrangle. Map names in brown. Fraser 

quadrangle in yellow.

Shroba 2003,

2005–2008

Theobald (mapping

modified by Bryant)

Bryant 1974,

2005–2006

Theobald,

1959–1963

105°52’30”

40°00’

105°45’

39°52’30”

Sources of mapping for Fraser 7.5-minute 

quadrangle. Mapping by Bryant in green, 

Shroba in yellow, Theobald (modified by 

Bryant) in purple, and Theobald in blue.

LIST OF MAP UNITS

SURFICIAL DEPOSITS

Artificial fill deposits

Artificial fill (latest Holocene)

Alluvial deposits

Valley-floor alluvium (Holocene and late Pleistocene?)

Sheetwash deposits and valley-floor alluvium, undivided (Holocene and late 

Pleistocene?)

Sheetwash deposits (Holocene and late Pleistocene)

Gravelly stream-terrace alluvium (late to early? Pleistocene)

Unit 1 (late Pleistocene)

Unit 2 (late and middle Pleistocene)

Unit 3 (middle Pleistocene)

Unit 4 (middle Pleistocene)

Unit 5 (middle Pleistocene)

Unit 6 (middle Pleistocene)

Unit 7 (middle or early Pleistocene)

Unit 8 (middle or early Pleistocene)

Old gravelly stream alluvium (early Pleistocene or Pliocene)

Alluvial and mass-movement deposits

Alluvium and colluvium, undivided (Holocene and late Pleistocene)

Fan deposits (Holocene and late Pleistocene)

Lower pediment deposits (late Pleistocene)

Higher pediment deposits (late and middle Pleistocene)

Gravelly stream alluvium and diamicton, undivided (middle Pleistocene)

Mass-movement deposits

Clayey-silt matrix colluvium (Holocene to middle? Pleistocene)

Sandy matrix colluvium (Holocene to middle? Pleistocene)

Landslide deposits (Holocene to middle? Pleistocene)

Talus deposits (Holocene to middle? Pleistocene)

Glacial deposits

Till of Pinedale age (late Pleistocene)

Till of Bull Lake age (late and middle Pleistocene)

Till of Pinedale age and till of Bull Lake age, undivided (late and middle 

Pleistocene)

BEDROCK UNITS

Post-Laramide sedimentary and volcanic rocks

Troublesome Formation (upper Miocene to upper Oligocene)

Rhyolite tuff (Oligocene)

Pre-Laramide sedimentary rocks

Dakota Group (Lower Cretaceous)

Morrison Formation (Upper Jurassic)

Proterozoic rocks

Pegmatite of the Berthoud Plutonic Suite (Mesoproterozoic)

Monzogranite and granite of the Berthoud Plutonic Suite (Mesoproterozoic)

Pegmatite (Mesoproterozoic or Paleoproterozoic)

Granodiorite and monzogranite (Mesoproterozoic or Paleoproterozoic)

Foliated granodiorite, tonalite, and diorite of the Routt Plutonic Suite 

(Paleoproterozoic)

Migmatitic biotite schist and gneiss (Paleoproterozoic)

Hornblende gneiss and calc-silicate gneiss (Paleoproterozoic)

Interlayered gneiss (Paleoproterozoic)

af

Qva

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Qg2

Qg3

Qg4

Qg5

Qg6

Qg7

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EXPLANATION

Contact

Fault, type unspecified—Dotted where concealed beneath surficial deposits. The 

Saint Louis Creek fault and Vasquez Pass fault are inferred beneath and near the 

floors of relatively straight valleys. The nearest exposures of these faults are 

about 9 km southwest and south, respectively, of the Fraser quadrangle (Kellogg 

and others, 2008)

Normal fault—Dashed where approximately located; dotted where concealed 

beneath surficial deposits; bar-and-ball symbol on apparent downthrown side. 

Tick shows dip value and direction 

Inclined bedding—Showing strike and dip

Inclined foliation—Showing strike and dip

Vertical or near vertical foliation—Showing strike

Lineation

Mineral lineation—Showing bearing and plunge, depicted with an arrowhead 

Crenulation lineation—Showing bearing and plunge, depicted with a diamond

Horizontal mineral lineation—Showing bearing 

Cataclastic rock—Northeast-trending zone composed of thoroughly brecciated rock 

and (or) abundant fault gouge near the southeast corner of the map area. Locally 

may include blocks of ductilely deformed rock. Probably derived from the 

adjacent migmatitic biotite schist and gneiss (Xmg) and pegmatite of the 

Berthoud Plutonic Suite (Yp). Formed later than the 1.42-Ga mylonites in the 

main part of the Saint Louis Lake shear zone in the Byers Peak quadrangle 

(McCoy and others, 2005). Age uncertain; cataclasis may be have occurred 

during the Neoproterozoic, later during Laramide compression, and possibly 

during mid-Tertiary deformation 

Ductile deformation fabric in Proterozoic rocks (mylonite and related fabrics)

Location and age of dated rock—With sample number and 40Ar/39Ar age

Crest of moraine

Fluvial terrace scarp—Hachures are on or near riser between lower and higher 

terrace treads

Gravel pit—Approximate boundary

5

70

70

EEL–1

27.3±

0.1 Ma

24

49

19

49