A Geoarchaeological Overview of South Dakota and Preliminary

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integrity of deposits that are encountered. Eigenberger et al. (2009) provide a useful approach to
evaluating buried site potential. Their categories are quoted here, and discussed extensively in a
subsequent section, Concepts and Considerations, below.
“High Potential: depositional processes are…conducive to preserving buried archaeological deposits
in primary context and have the potential for separation of archaeological components.
“Moderate Potential: depositional processes … are conducive to preserving buried archaeological
deposits but with possible physical modifications to the primary context [i.e., eroded or otherwise
disturbed].
“Low Potential: deposits... are too old or too thin to contain buried archaeological deposits in primary
contexts or… accumulated in high-energy depositional environments (fluvial channels, for example)
where archaeological deposits would not survive in primary context” (Eigenberger et al. 2009:3-3).
These definitions have the advantage of being based primarily on geological processes as they relate
to habitability and post-occupational preservation of landforms. The same general concepts are used by
geoarchaeologists throughout the United States. Indeed, Eigenberger et al. (2009) state that their criteria
are based on those of Hudak and Hajic (2008), working in Minnesota, Hajic (2008) working in South
Dakota, and Mayer and McFaul (2008), working in Wyoming.
In addition to developing buried site potential criteria, Eigenberger et al. (2009) compiled a useful list
of Quaternary sedimentary landscapes and landforms found along the “New Build” section of the
proposed DM&E railroad in the South Fork Cheyenne Region (OSA-0004 in Figure 2). For each
landform, the dominant depositional processes were identified, along with the landform’s buried site
potential. Table 4, adapted from Eigenberger et al. (2009: Table 1), expands their approach to include
the rest of South Dakota.
As used here, a landscape is a mosaic of landforms. In Table 4, landscapes are grouped into Upland
and Stream Valley categories. Landforms in river, creek, and canyon landscapes are primarily late
Wisconsinan and Holocene in age, and thus their alluvial, eolian, and colluvial landforms all have some
degree of buried site potential. In upland landscapes, landforms vary considerably in the presence,
thickness of landforms of Holocene-age landforms and deposits that must be considered in evaluating
buried site potential.
Many landforms are present in more than one landscape. Table 5 lists the unique landforms identified
in Table 4. Each is briefly defined and discussed below. Detailed information on landforms and
geological processes can be found in numerous sources, but that by Waters (1992) is both
comprehensive and explicitly geoarchaeological in its perspective.
Eolian Environments
Dunes are comprised of windblown sand that builds to heights of several meters. In the Sand Hills
region, dunes can be up to 90 m thick (Martin et al. 2004). The low lying areas between dune crests are
called interdunes. Some interdunal areas are deflationary, that is, cleared of dune sand by wind, leaving
behind a lag of coarse sand and gravel, often on a bare bedrock surface. Depositional interdunes contain
eolian sands deposited by wind, or avalanched down dune slopes. In the Sand Hills, wetlands sometimes
form in the interdunal areas, fed by groundwater that percolates down, then laterally, through the dune
field. Dunes may advance over these wetlands, burying them. Eigenberger et al. (2009) classified the
archaeological potential of dunes as high, probably because of their thickness and Holocene age.
However, when active, the windward side of the dunes is subject to deflation, with the sand blowing up
and over the crest onto the advancing face of the dune. Thus sites within dunes are sometimes deflated
(Waters 1992:195-200). To the author’s knowledge, dunes have not been the subject of
geoarchaeological investigation in South Dakota.
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