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

The report 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), and for study of geomorphology and Quaternary
geology. The report identifies geologic hazards (e.g., landslides, swelling
soils, heaving bedrock, and flooding) if they are known to be located in, or
characteristic of, mapped units. Surficial deposits in the quadrangle are
evidence of 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 others preceded human occupation. 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 from about 30,000 to 12,000 years ago) global cooling caused
glaciers to form on Pikes Peak and in the high parts of the Sangre de Cristo
Mountains. Some glaciers advanced down valleys, deeply eroded the bedrock, and
deposited moraines (map units tbk, tbg, tbj, tbi) and deposited outwash (ggq,
gge), in the Wet Mountain Valley. On the plains (east part of map area), eolian
sand (es), stabilized dune sand (ed), and loess (elb) are present and in places
contain buried paleosols, which indicate sand dune deposition alternating with
periods of stabilized landscape during which soils developed.

Fifty-three types of surficial geologic deposits and residual materials of
Quaternary age are described in a pamphlet and located on a map of the greater
Pueblo area, in part of the Front Range, in the Wet and Sangre de Cristo
Mountains, and on the plains east of Colorado Springs and Pueblo. Deposits
formed by landslides, wind, and glaciers, as well as colluvium, residuum,
alluvium, and others are described in terms of predominant grain size, mineral
or rock composition (e.g., gypsiferous, calcareous, granitic, andesitic),
thickness, and other physical characteristics. Origins and ages of the deposits
and geologic hazards related to them are noted. Many lines drawn between 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 near Salida (on the west edge),
eastward about 107 mi (172 km), and from Antero Reservoir and Woodland Park on
the north edge to near Colorado City at the south edge (68 mi; 109 km).

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, and relevant geologic historical information and paleosoil
information, if any. Fifty-three map units of deposits include alluvium,
colluvium, residuum, eolian deposits, periglacial/disintegrated deposits,
tills, landslide units, glaciofluvial units, and a diamicton. A bedrock map
unit depicts large areas of mostly bare bedrock.

The physical properties of 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.

>puebpoly: polygon coverage containing geologic unit contacts and labels.
>puebline: arc coverage containing faults.
>puebpnt: point coverage containing point locations of decorative
> bar-and-ball symbols for 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.