This report presents the findings of a Phase I archaeological Investigation for the proposed Alice’s Road/105th Street Improvement Study, Dallas County, Iowa (Project No. Stp-u-9877[603]-70-35)

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This report presents the findings of a Phase I Archaeological Investigation for the proposed Alice’s Road/105th Street Improvement Study, Dallas County, Iowa (Project No. STP-U-9877[603]--70-35) (Figures 1 and 2). A Review and Compliance number of 00125047 was previously assigned to the original Phase I investigation for this project reported in Straka and Stanley 2000. Since the 2000 study, the Area of Potential Effect (APE) for the interchange project was expanded resulting in the need for additional Phase I investigation in the added area. The additional survey was conducted by Tallgrass Historians L.C. of Iowa City for CH2M Hill, Des Moines, Iowa, and the Iowa Department of Transportation. The architectural properties within the additional APE were also evaluated by Tallgrass Historians L.C., with the results of that study reported in Rogers 2006.

The purpose of a Phase I Archaeological Investigation is to locate, identify, and evaluate all archaeological resources within the APE for the proposed project in order to provide federal and state reviewing agencies with documentation of the project’s potential impact on historic properties. Historic properties are those resources that have been determined to have some potential eligibility for inclusion in the National Register of Historic Places.

The project area is located in parts of the E1/2 and the S1/2 of Section 9; part of the NW1/4 and the NW1/4, SW1/4 of Section 10; part of the NE1/4 of Section 16; part of the SE1/4, SE1/4 of Section 8; and part of the SE1/4, SW1/4 and the SW1/4, SE1/4 of Section 4, T78N-R26W, Boone Township, Dallas County, Iowa (Figure 3). The project’s expanded APE boundary is shown in Figure 3 in relation to the original and previously surveyed area for the proposed interchange project. The entire project area encompasses areas along, north, and south of existing Interstate 80, which was built through this area in the late 1960s. An existing rest area, on both sides of the interstate is situated near in the eastern half of the project area. The additional project area extends from Ashworth Road on the north to 335th Street/ Mills Civic Parkway on the south and includes within its boundary portions of existing 105th Street, Wendover Road, and Vermillion Court. The project area is in-between the existing interchange of I-80 and County Road R22 on the west and the Ashworth Road overpass on the east but does not extend all the way to either crossing (see Figure 2). The total area surveyed for archaeological resources by the current investigation (minus the previously surveyed area reported in Straka and Stanley 2000) measures approximately 240 ac (96 ha) in size.



The geological record of south-central Iowa dates to the Late Mississippian times, ca. 330-355 million years B.P., from the great, shallow, carbonate-producing seas from the region (Prior 1991:16-17). The newly formed rocks were subject to warping, uplift, and erosion. The Pennsylvanian rocks of south-central Iowa are a part of the Forest City Basin, and encompass approximately 20,000 square miles of Iowa. During the Pennsylvanian period, 300-320 million years B.P., central Iowa experienced many sea and shoreline shifts resulting in marine and non-marine environments. The non-marine environments included: numerous stream channels, floodplains, deltaic coastal plains, lush swamps, and wetlands (Anderson 1998:227-230).

The swampy, tropical conditions provided a particular ecozone, where freshwater wetlands eventually became peat bogs with a highly acidic environment associated with a depletion of oxygen, and a wide variety of flora. Seed ferns, rushes, and other vegetation dominated the coastal floodplains and swamps. The primary coal-forming plants include scaly lycopod trees (ancestors of modern club mosses) and tree ferns. Peat was eventually produced from the burial and alteration of this floral material at a rate that the floor of the swamp sinks at exactly the same rate as floral material is added to it. Coal was eventually produced trough the continuous cycle of rapid plant growth and accumulation of plant debris, floral burial under sediments, alteration, and compaction (Anderson 1998:245-248; Morehouse 1970:49; Stolp and DeLuca 1976:13). The primary factor limiting the thickness of coal seams was the differential compaction and shrinkage of the peat into coal (Morehouse 1970:44).

The project area is situated near an oval-shaped area known as the Madrid Coal Field. The Madrid Coal Field encompasses approximately 23 square miles at the intersection of Boone, Polk, and Dallas Counties (Reese 1975:1; Webber 1926:6). This oval-shaped area contains coal beds which are part of the lowermost unit of Pennsylvanian aged rocks, called the Cherokee group (rocks between the overlying Fort Scott Formation of the Marmaton Group and the erosional surface formed on Mississippian-aged rocks, within the Des Moines Series and are located at an elevation between 650-700 feet above mean sea level (Mason 1980:30; Reese 1975:1; Webber 1926:12).


The project area is located in a transitional zone between the Des Moines Lobe and the Southern Iowa Drift Plain (Gier 1978:5; Huerter and Billeck 1986:3; Straka and Stanley 2000:2) (Figure 4). The Des Moines Lobe is a reentrant feature associated with the terminal episode of the Wisconsinan glaciation. The Wisconsin glacier occupied an area of approximately 15,867 square kilometers (12,300 square miles) of central and northern Iowa and was part of the last glacial activity in Iowa during the Pleistocene epoch (Ruhe 1969:54). The Des Moines Lobe reached its maximum extent 13,800 years B.P., with the advance halting as what is now the city of Des Moines and marked by the Bemis end moraine. The Des Moines Lobe region is characterized by a relatively flat, loess-free, featureless landscape resulting from the advance of the glacier as it penetrated south into Iowa (Anderson 1998:320; Prior 1991:36-47). Any surficial features within this landform region are the result of glacial activity. Such features include moraines, kettle holes, and numerous depressions containing prairie lakes and potholes typical of this landform region. As the glacier advanced, it deposited an extensive amount of till over the entire region. The till is typically between 15-20 m (45-60 ft) thick and is known geologically as the Dows Formation.

The few rivers which drain the Des Moines Lobe have excavated deep valleys and exhibit extensive sand and gravel terraces. The largest of these rivers is the Des Moines River, which flows generally down the axis of this region. This steep-sided, narrow river valley was formed through rapid excavation by swift, glacial meltwater (Prior 1991:36-47). In Dallas County, the Raccoon River was established by the termination of the Des Moines Lobe and was formed by glacial outwash. The Raccoon River is approximately 2.5 miles south of the current project area. Sugar Creek which flows through the current project area enters the Raccoon River approximately 2.5 miles to the southeast of the project area.

The Southern Iowa Drift Plain has been described as the most representative Iowan landscape because it is the largest of Iowa’s landforms. It is characterized by steep rolling hills, stepped erosion surfaces, well-developed drainages and relatively flat uplands. As this landscape developed, Wisconsin-age loess was deposited on the uplands, resulting in a loess mantle that is generally between 1.5-9.1 m (5-30 ft) thick. The thickest loess deposits are found near major sources of windblown silt. The thick deposits of loess are located on broad, un-eroded uplands. The bulk of this silt mantle is Peoria loess. Pre-Illinoian glacial drift and the underlying sedimentary bedrock are often exposed in deeper stream valleys (Prior 1991:61-64).

The Southern Iowa Drift Plain is made up of four landscape surfaces known as the Yarmouth-Sangamon, the Late Sangamon, the Wisconsin (Iowan Surface), and the Holocene (post-glacial) from highest to lowest and oldest to youngest. The Yarmouth-Sangamon surface contains a distinct loess-mantled paleosol and can be found on nearly flat, un-eroded uplands, and un-dissected uplands. The Late Sangamon surface is typically seen as a gentle shelving or flattening of the gradient along hillslopes. The Wisconsin erosion surface was cut into the landscape as loess was being deposited between 16,500 and 21,000 years B.P. during the last Iowan glaciation. The Holocene erosion surface is marked by postglacial alluvial deposits in floodplains (Prior 1991:61-64; Bettis and Littke 1987:7-13).

The project area encompasses upland features, hillslopes, and alluvial plains. The upland features include a nearly level divide in-between Fox and Sugar creeks as well as a number of dissected interfluves on both sides of the divide. The upland interfluves are more dissected on the west and south sides of the divide, with the interfluves to the east, broader and more gently sloping. Hillslopes encountered within the project area include shoulder, back, foot and toe slopes, with drainage to the southwest, south, and east into the Sugar and Fox creek valleys. The upland landforms within the project area were found to be moderately to severely eroded by intensive cultivation during the historic and modern eras. Further impacts from interstate construction and secondary road relocations have further impacted large portions of the project area.

The extreme south end and west end of the project area extends across the alluvial plain of Sugar Creek, with the valley at the west end narrower in width than that at the south end. The course of Sugar Creek at the Interstate 80 crossing was artificially straightened when the interstate was built in the late 1960s resulting in a heavily altered channel and low terrace within the project area. The alluvial plain at the south end of the corridor has been altered only by cultivation, erosion, and sedimentation through the years but has meandered across the valley within the project corridor (see Figure 3).

The sediment assemblages of the small tributary valleys, such as Sugar Creek within the present project area, can be compared to the Holocene landscape valley evolution model presented by Bettis and Littke (1987). The model identifies the DeForest Formation which consists of four lithostratigraphic units: the Gunder, Roberts Creek, and Camp Creek, which are found as terrace or floodplain surfaces; and one alluvial fan member, the Corrington. Generally, the chronology of these units shows that the Gunder and Corrington members range from late Woodfordian/early Holocene to early/late Holocene in age. The Roberts Creek member relates to the late Holocene, and the Camp Creek (a.k.a. post-settlement alluvium or PSA) is historical in age. Correlating these units further with identified cultural phases in Iowa indicates that the Gunder and Corrington members may contain Paleo-Indian through Woodland components; the Roberts Creek member could contain Late Archaic through early historic components; and the Camp Creek member may contain buried and surface historic components as well as burying older surfaces.

The west section of the Sugar Creek valley within the project corridor was seriously impacted by the interstate construction disrupting a small fan deposit overlying Roberts Creek Member deposits. A glacial outwash knoll or knob is present just north, and outside, of the current project corridor and is visible as a small circle on the topographic map of this area (see Figure 3). The current property owner of this parcel noted that he had removed several feet off the top of this knoll further noting its composition of dense glacial gravels. The south section of the creek valley within the project corridor crosses low and intermediate terrace formations exhibiting alluvial Camp Creek and Roberts Creek member deposits, with a small colluvial fan deposit along the foot/toe slope positions at the base of the north slope. The west and south valley walls consist of steep bluffs, at the base of which Sugar Creek has often meandered.

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