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.
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.
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
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