The Laramie Basin - Mountains and Plains: The Ecology of Wyoming Landscapes - page 286

Fig. 17.3. Surface geology for the Wyoming portion of the
Laramie Basin. Recent alluvium and alluvial fans, shown in
yellow and buff colors, cover about 50 percent of the basin
floor. Green and blue colors show terraces and benches, which
originated as alluvium and occur on about 24 percent of the
floor. the Airport and Harmony benches are conspicuous (see

also fig. 17.5). Much of the surface has remnants of the Qua-
ternary alluvium and older deposits that once filled the basin.
Some surface types listed in the legend are not easily distin-
guished at the scale of this map, including eolian deposits.
cartography by Ramesh Sivanpillai, University of Wyoming.
Adapted from case et al. (1998).

Prominent on the east side of the Laramie Basin are
the hard rocks of the casper Formation, strata deposited
during the Paleozoic era and now easily visible in the
canyon east of Laramie, through which interstate 80
passes. it is the oldest sedimentary formation in much of
the basin, lying directly on top of Precambrian igneous
and metamorphic rocks (see fig. 17.2). it includes strata
that contain the aquifer on which most people in the
basin depend. Wells can be drilled to access this water,
but artesian flows reach the surface in numerous places
as springs, such as on the east side of Laramie. 13 the

aquifer is recharged by rain and snow on the west slope
of the range, from its upslope edge near Lincoln Monu-
ment down to the Laramie city limits. Protecting water
quality in this aquifer is viewed as very important. 14
the erosion of Quaternary alluvium and underlying
strata has been most rapid in the southern half of the
Laramie Basin, where the elevation is about 1,000 feet
higher than on the north end. this erosion has gone on
sufficiently long that some of the basin's oldest sedimen-
tary strata are now exposed, often creating landforms
that are aesthetically, economically, and ecologically