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Geologic Map of the Silt Quadrangle, Garfield County, Colorado
Entry ID: USGS_Map_MF-2331

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Summary

Abstract: To update and reinterpret earlier geologic mapping, and to provide sufficient
geologic information for land-use decisions.

New 1:24,000-scale geologic mapping in the Silt 7.5' quadrangle, in support of
the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project,
provides new interpretations of the stratigraphy, structure, and geologic
hazards in the area of the southwest flank of the White River uplift, the Grand
Hogback, and the eastern Piceance Basin.

The Wasatch Formation was subdivided into three formal members, the Shire,
Molina, and Atwell Gulch Members. Also a sandstone unit within the Shire
Member was broken out. The Mesaverde Group consists of the upper Williams Fork
Formation and the lower Iles Formation. Members for the Iles Formation consist
of the Rollins Sandstone, the Cozzette Sandstone, and the Corcoran Sandstone
Members. The Cozzette and Corcoran Sandstone Members were mapped as a combined
unit. Only the upper part of the Upper Member of the Mancos Shale is exposed
in the quadrangle.

From the southwestern corner of the map area toward the northwest, the
unfaulted early Eocene to Paleocene Wasatch Formation and underlying Mesaverde
Group gradually increase in dip to form the Grand Hogback monocline that
reaches 45-75 degree dips to the southwest (section A-A'). The shallow west-
northwest-trending Rifle syncline separates the northern part of the quadrangle
from the southern part along the Colorado River.

Geologic hazards in the map area include erosion, expansive soils, and
flooding. Erosion includes mass wasting, gullying, and piping. Mass wasting
involves any rock or surficial material that moves downslope under the
influence of gravity, such as landslides, debris flows, or rock falls, and is
generally more prevalent on steeper slopes. Locally, where the Grand Hogback
is dipping greater than 60 degrees and the Wasatch Formation has been eroded,
leaving sandstone slabs of the Mesa Verde Group unsupported over vertical
distances as great as 500 m, the upper part of the unit has collapsed in
landslides, probably by a process of beam-buckle failure. In the source area
of these landslides strata are overturned and dip shallowly to the northeast.
Landslide deposits now armor Pleistocene pediment surfaces and extend at least
1 km into Cactus Valley. Gullying and piping generally occur on more gentle
slopes. Expansive soils and expansive bedrock are those unconsolidated
materials or rocks that swell when wet and shrink when dry. Most floods are
restricted to low-lying areas.

Several gas-producing wells extract methane from coals from the upper part of
the Iles Formation.

Map political location: Garfield County, Colorado
Compilation scale: 1:24,000
Geology mapped in 1992 to 1996.
Compilation completed March 1997.

Related URL

Link: View Related Information
Description: USGS Open-File Report, Preliminary Geologic Map of the SILT
Quadrangle, Garfield County, Colorado by Ralph R. Shroba, George
M. Farier, and Morris W. Green, publishied in 1994.

Link: GET DATA
Description: Map in PDF (2.8 megabytes)

Link: GET DATA
Description: GZIPPED TAR archive of ArcInfo files, metadata, etc. (3 MB)

Link: GET DATA
Description: ZIPPED archive of ArcInfo files, metadata, etc. (3 MB)

Link: GET DATA
Description: ZIPPED archive of georeferenced image files of base map (4 MB)

Link: VIEW EXTENDED METADATA
Description: Metadata in TEXT format (30 KB)

Link: VIEW EXTENDED METADATA
Description: Metadata in HTML format (39 KB)

Link: VIEW PROJECT HOME PAGE

Geographic Coverage

N: 39.625 S: 39.5 E: -107.625 W: -107.75

Data Set Citation

Dataset Originator/Creator: Ralph R. Shroba; Robert B. Scott
Dataset Title: Geologic Map of the Silt Quadrangle, Garfield County, Colorado
Dataset Release Date: 2001
Dataset Release Place: Denver, Colorado, USA
Dataset Publisher: U.S. Geological Survey
Version: 1.0
Issue Identification: U.S. Geological Survey Miscellaneous Field Studies Map
Data Presentation Form: map
Online Resource: http://pubs.usgs.gov/mf/2001/mf-2331/

Location Keywords

CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > COLORADO > GARFIELD COUNTY

ISO Topic Category

ELEVATION
GEOSCIENTIFIC INFORMATION
INLAND WATERS

Platform

MAPS [Information]

Access Constraints

None

Use Constraints

None. Acknowledgment of the U.S. Geological Survey would be appreciated in
products derived from these data.

Keywords

Geologic Cross Section

Geology

Geologic maps

Cretaceous to Tertiary sedimentary rocks

Quaternary to Tertiary surficial deposits

Laramide compressional deformation

Geologic hazards

Wasatch Formation

Mesaverde Group

Williams Fork Formation

Iles Formation

Mancos Shale

Colorado

Garfield County

Silt Quadrangle

Silt Quad

Data Set Progress

COMPLETE

Originating Center

USGS

Data Center

Central Region, Publications, Geology Division, U.S. Geological Survey, U.S. Department of the Interior [Information]
Data Center URL: http://cpg.cr.usgs.gov/pub/publications.html
Dataset ID: USGS Miscellaneous Field Studies Map MF-2331

Data Center Personnel

Name: U.S. GEOLOGICAL SURVEY CENTRAL PUBLICATIONS GROUP
Phone: (303) 236-5486
Contact Address:
Denver Federal Center
MS-902
Box 25046
City: Denver
Province or State: CO
Postal Code: 80225-0046
Country: USA

Distribution

Distribution_Media: Online (HTTP>
Distribution_Size: 3 megabytes
Distribution_Format: Arc/Info export files and ArcView shapefiles
Fees: None

Personnel

RALPH R. SHROBA
Role: DIF AUTHOR
Phone: 303-236-1292
Fax: 303-236-0214
Email: rshroba at usgs.gov
Contact Address:
U.S. Geological Survey
Box 25046, MS 913
Denver Federal Center
City: Denver
Province or State: CO
Postal Code: 80225-0046
Country: USA

Creation and Review Dates

DIF Creation Date: 2004-09-10

Last DIF Revision Date: 2004-09-10

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