A spatial database of bedding attitudes to accompany Geologic map of the greater Denver area, Front Range urban corridor, Colorado, by Donald E. Trimble and Michael N. Machette

This digital map shows bedding attitude symbols display over
the geographic extent of surficial deposits and rock
stratigraphic units (formations) as compiled by Trimble and
Machette 1973-1977 and published in 1979 (U.S. Geological
Survey Map I-856-H) under the Front Range Urban Corridor
Geology Program. Trimble and Machette compiled their geologic
map from published geologic maps and unpublished geologic
mapping having varied map unit schemes. A convenient feature of
the compiled map is its uniform classification of geologic
units that mostly matches those of companion maps to the
north (USGS I-855-G) and to the south (USGS I-857-F).
Published as a color paper map, the Trimble and Machette map
was intended for land-use planning in the Front Range Urban
Corridor. This map recently (1997-1999), was digitized under
the USGS Front Range Infrastructure Resources Project (see
cross-reference).
In general, the mountainous areas in the west part of the map
exhibit various igneous and metamorphic bedrock units of
Precambrian age, major faults, and fault brecciation zones at
the east margin (5-20 km wide) of the Front Range. The eastern
and central parts of the map (Colorado Piedmont) depict a
mantle of unconsolidated deposits of Quaternary age and
interspersed outcroppings of Cretaceous or Tertiary-Cretaceous
sedimentary bedrock. The Quaternary mantle is comprised of
eolian deposits (quartz sand and silt), alluvium (gravel, sand,
and silt of variable composition), colluvium, and few
landslides. At the mountain front, north-trending, dipping
Paleozoic and Mesozoic sandstone, shale, and limestone bedrock
formations form hogbacks and intervening valleys.