Generalized Surficial Geologic Map of the Denver 1 x 2 degree Quadrangle, Colorado

Metadata also available as

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: David W. Moore
Originator: Arthur W. Straub
Originator: Margaret E. Berry
Originator: Michael L. Baker
Originator: Theodore R. Brandt
Publication_Date: 2001

Title:
Generalized Surficial Geologic Map of the Denver 1 x 2 degree Quadrangle, Colorado
Edition: 1.0
Series_Information:
Series_Name: Miscellaneous Field Studies
Issue_Identification: MF-2347
Publication_Information:
Publication_Place: Denver, Colorado
Publisher: U.S. Geological Survey

Online_Linkage: <http://greenwood.cr.usgs.gov/pub/mf-maps/mf-2347/>

Description:
Abstract:
Thirty-nine types of surficial geologic deposits and residual materials of Quaternary age are described and mapped in the greater Denver area, in part of the Front Range, and in the piedmont and plains east of Denver, Boulder, and Castle Rock. Descriptions appear in the pamphlet that accompanies the map. Landslide deposits, colluvium, residuum, alluvium, and other deposits or materials are described in terms of predominant grain size, mineral or rock composition (e.g., gypsiferous, calcareous, granitic, andesitic), thickness of deposits, and other physical characteristics. Origins and ages of the deposits and geologic hazards related to them are noted. Many lines between geologic units on our map were placed by generalizing contacts on published maps. However, in 1997-1999 we mapped new boundaries, as well. The map was projected to the UTM projection. This large map area extends from the Continental Divide near Winter Park and Fairplay (on the west edge), eastward about 107 mi (172 km); and extends from Boulder on the north edge to Woodland Park at the south edge (68 mi; 109 km).

Purpose:
The map and descriptions offer information that may be used for: land-use planning (e.g. selecting land fill sites, greenbelts, avoiding geologic hazards), for finding aggregate resources (crushed rock, sand, and gravel), for study of geomorphology and Quaternary geology. Geologic hazards (e.g., landslides, swelling soils, heaving bedrock, and flooding) known to be located in, or characteristic of some mapped units, were identified.

Surficial deposits in the quadrangle partially record depositional events of the Quaternary Period (the most recent 1.8 million years). Some events such as floods are familiar to persons living in the area, while other recorded events are pre-historical. The latter include glaciation, probable large earthquakes, protracted drought, and widespread deposition of sand and silt by wind. At least twice in the past 200,000 years (most recently about 30,000 to 12,000 years ago) global cooling caused glaciers to form along the Continental Divide. The glaciers advanced down valleys in the Front Range, deeply eroded the bedrock, and deposited moraines (map units tbg, tbj) and outwash (ggq, gge). On the plains (east part of map), eolian sand (es), stabilized dune sand (ed), and loess (elb) are present and in places contain buried paleosols. These deposits indicate that periods of sand dune deposition alternated with periods of stabilized dunes and soil formation.

Supplemental_Information:
Compilation scale: 1:250,000. Map is available in digital and print-on-demand paper formats. Deposits are described in terms of predominant grain size, mineralogic and lithologic composition, general thickness, and geologic hazards, if any, relevant geologic historical information and paleosoil information, if any. Thirty-nine map units of deposits include 5 alluvium types, 15 colluvia, 6 residua, 3 types of eolian deposits, 2 periglacial/disintegrated deposits, 3 tills, 2 landslide units, 2 glaciofluvial units, and 1 diamicton. An additional map unit depicts large areas of mostly bare bedrock.

The physical properties of the surficial materials were compiled from published soil and geologic maps and reports, our field observations, and from earth science journal articles. Selected deposits in the field were checked for conformity to descriptions of map units by the Quaternary geologist who compiled the surficial geologic map units.

FILES INCLUDED IN THIS DATA SET:

denvpoly: polygon coverage containing geologic unit contacts and labels.
denvline: arc coverage containing faults.
geol_sfo.lin:  This lineset file defines geologic line types in the
               geologically themed coverages.
geoscamp2.mrk:  This markerset file defines the geologic markers in the
                geologically themed coverages.
color524.shd:  This shadeset file defines the cmyk values of colors
               assigned to polygons in the geologically themed coverages.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 2001
Currentness_Reference: publication date

Status:
Progress: Complete
Maintenance_and_Update_Frequency: Irregular. No major update is anticipated.

Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -106.0
East_Bounding_Coordinate: -104.0
North_Bounding_Coordinate: 40.0
South_Bounding_Coordinate: 39.0

Keywords:
Theme:
Theme_Keyword_Thesaurus: Glossary of Geology, American Geological Institute
Theme_Keyword: surficial deposits
Theme_Keyword: slumping
Theme_Keyword: flooding
Theme_Keyword: gravel
Theme_Keyword: sand
Theme_Keyword: glacial deposits
Theme_Keyword: till
Theme_Keyword: terrace gravel
Theme_Keyword: pediment gravel
Theme_Keyword: periglacial
Theme_Keyword: bedrock
Theme_Keyword: placer gold
Theme_Keyword: landslide deposit
Theme_Keyword: debris-flow deposit
Theme_Keyword: Quaternary deposits
Theme_Keyword: Holocene
Theme_Keyword: eolian sand
Theme_Keyword: loess
Theme_Keyword: alluvium
Theme_Keyword: colluvium
Theme_Keyword: Pleistocene
Theme_Keyword: land-use planning
Theme_Keyword: surficial geology
Theme_Keyword: swelling clay
Theme_Keyword: expansive clay
Theme_Keyword: heaving bedrock
Theme_Keyword: erosion
Theme_Keyword: soil

Place:
Place_Keyword_Thesaurus:
U.S. Board on Geographic Names (BGN) Geographic Names Information System (GNIS)
Place_Keyword: United States of America
Place_Keyword: Colorado
Place_Keyword: Adams County
Place_Keyword: Arapahoe County
Place_Keyword: Boulder County
Place_Keyword: Clear Creek County
Place_Keyword: Denver County
Place_Keyword: Douglas County
Place_Keyword: Elbert County
Place_Keyword: El Paso County
Place_Keyword: Grand County
Place_Keyword: Jefferson County
Place_Keyword: Park County
Place_Keyword: Summit County
Place_Keyword: Teller County
Place_Keyword: Golden
Place_Keyword: Denver
Place_Keyword: Castle Rock
Place_Keyword: Brighton
Place_Keyword: Littleton
Place_Keyword: Lakewood
Place_Keyword: Watkins
Place_Keyword: Monument
Place_Keyword: Parker
Place_Keyword: Front Range
Place_Keyword: Southern Rocky Mountains
Place_Keyword: Colorado Piedmont
Place_Keyword: Great Plains

Access_Constraints: none

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

Browse_Graphic:
Browse_Graphic_File_Name:
<http://greenwood.cr.usgs.gov/pub/mf-maps/mf-2347/mf-2347po.pdf>
Browse_Graphic_File_Description:
The browse graphic file depicts a layout, featuring geologic map and supporting information. The geologic map image is colored, labeled polygons of surficial geologic units and is shown with a scanned image of roads, rivers, political boundaries, place names, and other base map features, all registered to the geologic map. These features are the standard USGS 1:250,000 base map data, including longitude and latitude, numbered UTM (meters), and the Colorado State Coordinate System (feet) grid ticks (21 internal grid tics at 15-minute intervals of longitude and latitude are visible). Supporting information includes a correlation chart of geologic map units, a list of map unit symbols and names, and a small location map that shows the quadrangle location relative to rivers, state boundaries, and locations of 26 published USGS geologic maps (1:250,000 scale) in the Colorado Plateau and western Great Plains. This PDF file is optimized for highest print quality. An accompanying pamphlet includes a complete description of map units, selected references, and a description of terminology used.
Browse_Graphic_File_Type: PDF

Browse_Graphic:
Browse_Graphic_File_Name:
<http://greenwood.cr.usgs.gov/pub/mf-maps/mf-2347/mf-2347so.pdf>
Browse_Graphic_File_Description:
Same as above, except this PDF file is optimized for on-screen viewing.
Browse_Graphic_File_Type: PDF

Data_Set_Credit:
In 1978, Lucille A. Piety hand drafted a map of surficial geologic units for the Denver quadrangle. She accomplished this by generalizing linework from the published Geologic Map of the Denver 1x2-degree quadrangle, north-central Colorado (Bruce Bryant, L.W. McGrew, and R.A. Wobus, 1981, USGS Miscellaneous Investigations Series Map I-1163). This linework was intended to be reduced as partial input for a more extensive 1:1,000,000-scale map. We digitized these lines initially, edited them to obtain more detail and accuracy, and added data appropriate for a 1:250,000-scale published map. Piety also classified the surficial units. However, because this system was designed for a 1:1,000,000-scale map (less detailed map), we had to make a more detailed classification to replace it.

Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David W. Moore
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: PO Box 25046, MS 913, Denver federal Center
City: Denver
State_or_Province: CO
Postal_Code: 80225-0046
Country: USA
Contact_Voice_Telephone: (303) 236-1271
Contact_Electronic_Mail_Address: dwmoore@usgs.gov

Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
We checked attributes for accuracy by preparing a check plot in which map element colors, patterns, and decorations are determined by the attribute values. The plot was then visually checked against the geologists' original compilations. Polygon closure, compilation, and attribution errors were corrected.

Logical_Consistency_Report:
Map elements were visually checked for overshoots, undershoots, duplicate features, polygon closures, and other errors. Automated (ArcInfo AML) routines were also used to check the databases for polygon label errors, line or point attribution errors, sliver polygons, dangling arcs, intersection errors, and projection information. The map was reviewed by two geologists, including another Quaternary specialist for consistency with geologic principles and general conformity to USGS mapping standards.

Completeness_Report:
Data are complete: no features that could be accurately represented at the compilation scale of 1:250,000 were eliminated. Map units have been generalized from larger or same-scale source maps. Unit properties are described in the accompanying pamphlet. The smallest area expressed in this data set is approximately 62,500 square meters (0.0625 sq. km. or, a square area 250 m on a side).

Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Map lines that depict contacts between geologic units were placed by generalizing contacts obtained from published geologic maps, viewing orthophotoquads in USDA county published soil reports, and the authors' field observations. Lines were digitized by using a digitizer tablet having a resolution of 0.001 in. No elevation data exist in the database. No systematic analysis of accuracy was attempted. The best accuracy is that of map lines around boundaries of young channel alluvial deposits, unit asa. They are within 2 mm of their correct map location (within 500 m of actual ground limits) relative to map symbols that depict topography and streams. Perhaps half are within 1 mm of correct map location (250 m of actual ground location). Other map boundaries that represent colluvial, residual, and eolian deposits are less accurately placed because ground limits of these deposits are indefinite, i.e., they grade into one another. Thus, many boundaries on the map (vectorized polygons) are approximate. Another source of inaccuracy is that a material may contain inclusions of surficial materials other than the material depicted by any given map unit.

Lineage:
Process_Step:
Process_Description:
The Denver surficial geologic database was digitized from pen-and-ink compilations on scale-stable base material using the GSMCAD public domain program (USGS Open-File Report 96-007).
Process_Date: 1999

Process_Step:
Process_Description:
The digitized linework was edited and revised several times for improved accuracy.
Process_Date: 1999

Process_Step:
Process_Description:
The database was exported to ArcInfo using the GSMCAD export function to create ARC-generated ASCII files and the gsmarc.aml program in ARC to convert the ASCII files to ARC coverages and build polygons.
Process_Date: 1999

Process_Step:
Process_Description:
Coverages were edited and revised in ArcInfo 7.2.1 to reflect editorial changes and to further attribute polygons with descriptions and all features with source information.
Process_Date: 2000

Process_Step:
Process_Description:
External attribute lookup tables for labels and symbols were incorporated into the coverages using the joinitem command.
Process_Date: 2000

Process_Step:
Process_Description:
Final revisions to the digital database were made and a map layout (browse graphic) prepared in Adobe Illustrator.
Process_Date: 2000

Process_Step:
Process_Description:
The digital database was quality checked by the data manager, USGS Central Region Earth Surface Processes team.
Process_Date: 2001


Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector


Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 13
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: .9996
Longitude_of_Central_Meridian: -105.0
Latitude_of_Projection_Origin: 0.0
False_Easting: 0.0
False_Northing: 0.0
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 200
Ordinate_Resolution: 200
Planar_Distance_Units: METERS

Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1927
Ellipsoid_Name: Clarke 1866
Semi-major_Axis: 6378206.4
Denominator_of_Flattening_Ratio: 294.98


Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:

DATABASE STRUCTURE -- ArcInfo and ArcView ==========

There are two coverages (root name = denv) and three additional info files.

This GIS database includes related look-up tables, which store detailed attribute information. Arc/Info relates for each coverage are saved in a file named <covername>.rel. Use the RELATE command with the restore argument at the arc prompt to make the relates active. Alternatively, in Arctools, use the Relate environment: open dialog in the Manage - Relates flyout menu under the Arctools menu to make the relates active.

denvpoly coverage: contains all contact lines and labelpoints for each geologic polygon. In the denvpoly.pat INFO file the LABEL item indicates the rock unit label (abbreviation) used to label the unit on the map. The DESC item contains the formal or informal unit name. The SOURCE item contains the numeric code used to identify the data source for the rock unit. The SYMBOL item contains the shadeset symbol number used by ArcInfo to plot a filled/shaded polygon. The symbol numbers in this coverage refer to the color524.shd shadeset.

In the coverage's denvpoly.aat INFO file the NAME item contains the name given to the structural feature. The SOURCE item contains the numeric code used to identify the data source for the structural feature. The SYMBOL item contains the lineset symbol number used by ArcInfo to plot a line. The symbol numbers in this coverage refer to the geol_sfo.lin lineset.

In the the coverages's denvpoly.ref INFO file the SOURCE item lists the numeric code used to identify the data source. The scale item list the scale of the source map. (This value is the denominator of the proportional fraction that identifies the scale of the map that was digitized or scanned to produce the digital map.) The AUTHORS item lists the author(s) or compiler(s) of source map entered as last name, first name or initial, and middle initial. The YEAR item lists the source (map) publication date. The REFERENCE item lists the remainder of the reference in USGS reference format.

The INFO structure of these files is listed below:

DENVPOLY.PAT:

COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  ALTERNATE NAME
    1  AREA                   8    18     F      5
    9  PERIMETER              8    18     F      5
   17  DENVPOLY#              4     5     B      -
   21  DENVPOLY-ID            4     5     B      -
   25  SOURCE                 4     4     I      -
   29  LABEL                 10    10     C      -
   39  DESC                 123   123     C      -
  162  SYMBOL                 3     3     I      -
DENVPOLY.AAT:

COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE  N.DEC  ALTERNATE NAME
    1  FNODE#                 4     5     B      -
    5  TNODE#                 4     5     B      -
    9  LPOLY#                 4     5     B      -
   13  RPOLY#                 4     5     B      -
   17  LENGTH                 8    18     F      5
   25  DENVPOLY#              4     5     B      -
   29  DENVPOLY-ID            4     5     B      -
   33  NAME                  30    30     C      -
   63  SOURCE                 4     4     I      -
   67  SYMBOL                 3     3     I      -
DENVPOLY.REF:

COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  ALTERNATE NAME
    1  SOURCE                 4     4     I      -
    5  SCALE                  8     8     I      -
   13  AUTHORS              200   200     C      -
  213  YEAR                   4     4     I      -
  217  REFERENCE            250   250     C      -

  Unique values of NAME in DENVPOLY.AAT: contact, neat, water
denvline coverage: contains faults. In the denvline.aat INFO file the NAME item indicates the name given to the structural feature.

In the the coverages's denvline.ref INFO file the SOURCE item lists the numeric code used to identify the data source. The scale item list the scale of the source map. (This value is the denominator of the proportional fraction that identifies the scale of the map that was digitized or scanned to produce the digital map.) The AUTHORS item lists the author(s) or compiler(s) of source map entered as last name, first name or initial, and middle initial. The YEAR item lists the source (map) publication date. The REFERENCE item lists the remainder of the reference in USGS reference format.

The INFO structure of these files is listed below:

DENVLINE.AAT:

COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  ALTERNATE NAME
    1  FNODE#                 4     5     B      -
    5  TNODE#                 4     5     B      -
    9  LPOLY#                 4     5     B      -
   13  RPOLY#                 4     5     B      -
   17  LENGTH                 8    18     F      5
   25  DENVLINE#              4     5     B      -
   29  DENVLINE-ID            4     5     B      -
   33  NAME                  30    30     C      -
   63  SOURCE                 4     4     I      -
   67  SYMBOL                 3     3     I      -
DENVLINE.REF:

COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  ALTERNATE NAME
    1  SOURCE                 4     4     I      -
    5  SCALE                  8     8     I      -
   13  AUTHORS              200   200     C      -
  213  YEAR                   4     4     I      -
  217  REFERENCE            250   250     C      -

  Unique values of NAME in DENVLINE.AAT: High-angle reverse fault
Entity_and_Attribute_Detail_Citation:

Database root name: denv
LABEL AND DESCRIPTION FOR GEOLOGIC UNITS MAPPED
LABEL              DESC
afa      Alluvial-fan deposit
cac      Arkosic loamy colluvium and sheetwash alluvium
cacb     Bouldery phase of arkosic loamy colluvium
xch      Clayey, calcareous disintegration residuum
dba      Crystalline-clast deposits
dbd      Mixed-lithology-clast deposits
asa      Alluvial sand, silt, clay, and gravel (post-Piney
         Creek alluvium, Piney Creek Alluvium,and pre-Piney Creek alluvium
ed       Stabilized dune sand
es       Eolian sand
jea      Slump-block, earthflow, and mudflow landslide deposits
ccd      Calcareous clayey colluvium
ccm      Andesitic clayey colluvium
caa      Andesitic loamy colluvium
clx      Clay loam colluvium
csk      Grus, crystalline-clast colluvium, rock outcrop, and alluvium
csm      Tuffaceous colluvium
cgc      Gneiss- and granite-clast gravelly colluvium
cgh      Arkose-clast loamy colluvium
cbh      Blocky sedimentary-rock colluvium
cbm      Carbonate-clast loamy colluvium
cbs      Rhyolite- and andesite-clast colluvium
cbu      Mixed-lithology blocky colluvium
xlu      Feldspathic loamy disintegration residuum
xlv      Loamy disintegration residuum, eolian sand, and sheetwash
         alluvium
xsa      Feldspathic quartz-sand disintegration residuum
xgb      Latite-clast disintegration residuum
jbc      Bouldery crystalline-rock landslide deposit
xsg      Feldspathic quartz-sand disintegration residuum
elb      Loess (Peoria Formation)
tbg      Crystalline-clast bouldery till
tbj      Mixed-lithology-clast bouldery till
ggq      Outwash sand and gravel (outwash of Bull Lake, Pinedale,
         and post-Pinedale ages)
ags      Alluvial sand, silt, clay and gravel (Louviers and Slocum
         Alluviums, undivided; late middle Pleistocene)
tbk      Bouldery till (till of pre-Bull Lake glaciations)
gge      Outwash sand and gravel (outwash of pre-Bull Lake glaciations)
agm      Alluvium gravel and sand (Verdos and Rocky Flats Alluviums,
         undivided; early middle Pleistocene and early Pleistocene)
pga      Pediment gravel
cra      Hogback and rangefront colluvium, alluvium, and rock
         outcrop complex
QTdd     Diamicton
R        Bedrock
w        Open water

Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: MS 902, Box 25046, Denver Federal Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225-0046
Contact_Voice_Telephone: (303) 236-5486
Contact_Electronic_Mail_Address: webmaster@greenwood.cr.usgs.gov

Resource_Description: MF-2347

Distribution_Liability:
Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this digital spatial data has been subjected to rigorous review and is substantially complete, it is released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.

Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ARCE,SHP
Format_Version_Number: ArcInfo 7.2.1
File_Decompression_Technique:
GZIP TAR archive: In UNIX use the command "gunzip -c <filename> | tar xvf -" In Windows, use WinZip (<http://www.winzip.com/>) or other programs to extract the file.
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <http://greenwood.cr.usgs.gov/pub/mf-maps/mf-2347/>
Fees: No cost for the digital files


Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: USGS Information Services, Box 25286, Denver Federal Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225
Contact_Voice_Telephone: 1-888-ASK-USGS

Resource_Description: MF-2347 (Map-on-demand)

Distribution_Liability:
Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this digital spatial data has been subjected to rigorous review and is substantially complete, it is released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.

Standard_Order_Process:
Non-digital_Form:
Available as one sheet printed on a plotter; plus one pamphlet. Order from USGS at the address listed above or see <http://rmmcweb.cr.usgs.gov/mod/> for more information about ordering.

Fees:
Call 1-888-ASK-USGS or see <http://rmmcweb.cr.usgs.gov/mod/order.html> for current pricing information.


Metadata_Reference_Information:
Metadata_Date: 20010117
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: David W. Moore
Contact_Address:
Address_Type: mailing address
Address: U.S. Geological Survey
Address: MS 913, Box 25046 Denver Federal Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225-0046
Contact_Voice_Telephone: (303) 236-1271; (303) 236-1232
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998


Generated by mp version 2.7.3 on Wed Jan 17 23:07:24 2001