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Digital database of the previously published geologic map of the Boulder-Fort Collins-Greeley area, Colorado
This digital map shows the geographic extent of rock stratigraphic
units (formations) as compiled by Colton in 1976 under the Front
Range Urban Corridor Geology Program. Colton used his own geologic
mapping and previously published geologic maps to compile one map
having a single classification of geologic units. The resulting
published color paper map (USGS Map I-855-G, Colton, 1978) was
intended for land-use planning and to depict the regional geology.
In 1997-1999, another USGS project designed to address urban growth
issues was undertaken. This project, the USGS Front Range
Infrastructure Resources Project, undertook to digitize Colton's
map at 1:100,000 scale, making it useable in Geographical
Information Systems (GIS). That product is described here.
In general, the digitized map depicts in its western part
Precambrian igneous and metamorphic rocks, Pennsylvanian and
younger sedimentary rock units, major faults, and brecciated zones
along an eastern strip (5-20 km wide) of the Front Range. The
central and eastern parts of the map (Colorado Piedmont) show a
mantle of Quaternary unconsolidated deposits and interspersed
outcrops of sedimentary rock of Cretaceous or Tertiary age. A
surficial mantle of unconsolidated deposits of Quaternary age is
differentiated and depicted as eolium (wind-blown sand and silt),
alluvium (river gravel, sand, and silt of variable composition),
colluvium, and a few landslide deposits. At the mountain front,
north-trending, Paleozoic and Mesozoic formations of sandstone,
shale, and minor limestone dip mostly eastward and form folds,
fault blocks, hogbacks and intervening valleys. Local dikes and
sills of Tertiary rhyodacite and basalt intrude rocks near the
range front, mostly in the Boulder area.
Complete Metadata
| @id | http://datainventory.doi.gov/id/dataset/f49a3a508e863c45cde885355d2bc4e2 |
|---|---|
| bureauCode |
[ "010:12" ] |
| identifier | USGS:635a935cd34ebe4425047121 |
| spatial | -105.375,40.0,-104.625,40.625 |
| theme |
[ "geospatial" ] |
