from five 1:24,000 topographic quadrangles. The
original Mylar maps were provided to CRREL by
H.R. Schmoll and L.A. Yehle, U.S. Geological Sur-
vey. A contracted company scanned these maps
and converted raster data to vector data. Poly-
gons were developed and labeled at CRREL to
create an ArcInfo coverage of the surficial geol-
ogy for the USARAK's GIS database of Fort Rich-
ardson. The map coverage has been reviewed by
Schmoll and Yehle for accuracy and their detailed
explanations of the map symbols are included as
Appendix A. Our synthesis of the surficial geol-
ogy is presented in the following sections.
Surficial deposits
The most common and spatially extensive
surficial deposits on Fort Richardson are: 1) end
moraine, 2) lateral moraine, 3) ground moraine,
4) glacioalluvial, alluvial, and alluvial fan, 5)
estuarine, and 6) lacustrine (lake) (Fig. 4 and 5;
Tables 1 and 2). Less abundant deposits are those
of wind, colluvium, and rock glaciers. Wind depos-
its in the form of loess (wind blown silt) occur as a
thin blanket of variable thickness throughout the
area, but they have not been assigned a separate
map unit. Colluvium, a poorly sorted, uncom-
pacted, and unstable deposit of silt, sand, and
gravel, is found along mountain slopes (solifluc-
tion and landslide deposits) and as a veneer on
coastal and stream bluffs. Rock glaciers occur
only in high mountain valleys. They consist of
rock fragments with an ice matrix that allows
them to flow.
Figure 4. Major landforms in the Anchorage Lowland.
End-moraine deposits
stratigraphy (e.g., Fig. 3). This complexity is espe-
These are ice-marginal sediments deposited
cially true under the Fort Richardson cantonment
along the termini of glaciers. End moraines
area, where sedimentary deposits along the south
develop where the glacier remains relatively sta-
margin of the Elmendorf Moraine likely inter-
ble for an extended time. Deposition is polygen-
finger with alluvial fan sands and gravels. These
etic, resulting from combined fluvial (proglacial
stream), glacial (lodgement, meltout, glacial-
gravels are incised into or truncate ground-
moraine deposits, while all of these deposits
tectonic), and gravitational slope processes that
overlie older glacial and glacial marine deposits.
produce gently arcing ridge complexes at the ice
margin (Fig. 5). End moraines are composed of
juxtaposed sequences of coarse gravel, fine well-
Surficial geologic map
We developed the conceptual stratigraphic
sorted sand, dense silt and clay, and diamictons
model and interpreted the glacial history of the
(App. A).
area largely on the basis of recent surficial geologic
The Elmendorf Moraine is an end moraine
mapping by Yehle and Schmoll (1987a,b, 1989),
that forms a major morphological feature across
Fort Richardson just north of the cantonment
Yehle et al. (1990, 1992), and Schmoll et al. (1996).
area. It continues along the north edge of Elmen-
These studies provide specific information on
dorf Air Force Base and in the Susitna Lowland
surface morphology and detail how the various
across the Knik Arm (Fig. 1 and 4). Recent studies
sediments are distributed across Fort Richardson.
A geological map of Fort Richardson (Plate 1) was
have shown that the Elmendorf Moraine corre-
produced by incorporating the geological data
lates with ice advances in Turnagain Arm and
5
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