Geologic map of the Storm King Mountain quadrangle, Garfield County, Colorado

New 1:24,000-scale geologic mapping in the Storm King Mountain
7.5' quadrangle, in support of the USGS Western Colorado I-70
Corridor Cooperative Geologic Mapping Project, provides new data
on the structure on the south margin of the White River uplift
and the Grand Hogback and on the nature, history, and
distribution of surficial geologic units.
Rocks ranging from Holocene to Proterozoic in age are shown on
the map. The Canyon Creek Conglomerate, a unit presently known
to only occur in this quadrangle, is interpreted to have been
deposited in a very steep sided local basin formed by
dissolution of Pennsylvanian evaporite late in Tertiary time.
At the top of the Late Cretaceous Williams Fork Formation is a
unit of sandstone, siltstone, and claystone from which Late
Cretaceous palynomorphs were obtained in one locality. This
interval has been mapped previously as Ohio Creek Conglomerate,
but it does not fit the current interpretation of the origin of
the Ohio Creek. Rocks previously mapped as Frontier Sandstone
and Mowry Shale are here mapped as the lower member of the
Mancos Shale and contain beds equivalent to the Juana Lopez
Member of the Mancos Shale in northwestern New Mexico. The
Pennsylvanian Eagle Valley Formation in this quadrangle grades
into Eagle Valley Evaporite as mapped by Kirkham and others
(1997) in the Glenwood Springs area.
The Storm King Mountain quadrangle spans the south margin of the
White River uplift and crosses the Grand Hogback monocline into
the Piceance basin. Nearly flat lying Mississippian through
Cambrian sedimentary rocks capping the White River uplift are
bent into gentle south dips and broken by faults at the edge of
the uplift. South of these faults the beds dip moderately to
steeply to the south and are locally overturned. These dips are
interrupted by a structural terrace on which are superposed
numerous gentle minor folds and faults. This terrace has an
east-west extent similar to that of the Canyon Creek
Conglomerate to the north. We interpret that the terrace formed
by movement of Eagle Evaporite from below in response to
dissolution and diapirism in the area underlain by the
conglomerate. A low-angle normal fault dipping gently north
near the north margin of the quadrangle may have formed also in
response to diapirism and dissolution in the area of the Canyon
Creek Conglomerate. Along the east edge of the quadrangle
Miocene basalt flows are offset by faults along bedding planes
in underlying south-dipping Cretaceous rocks, probably because
of diapiric movement of evaporite into the Cattle Creek
anticline (Kirkham and Widmann, 1997).
Steep topography and weak rocks combine to produce a variety of
geologic hazards in the quadrangle.