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Geologic sourcing of chipped stone artifacts and lithic debitage is a routine part of archaeological analysis and report writing. In order to do this task, a comparative collection is obviously necessary, one with solid geologic associations and an expansive geographic selection. Iowa’s bedrock contains a large variety of quality, knappable, lithic raw materials from both primary and secondary sources. Identification of archaeological specimens with a specific raw material is primarily accomplished by macroscopic analysis techniques geared toward achieving a “best fit” results.
Excel Data Tables This section represents the current data on the lithic samples that compose the collection. These catalogs were created using Excel. The first file in this section represents the physical contents of the sample drawers housed in the laboratory at OSA. The normal type labels represents samples present in the assemblage while the shadow type labels represent those presently missing. An image window will open for any sample by clicking on the text box. We are working at acquiring those missing samples, processing them, and returning them to their proper drawer. The next three files in this section present three different ways to search for lithic raw material information. The first is a listing of lithic types by geologic system association. The second is an alphabetical listing of lithic types by county. The third is an alphabetical listing of lithic types by their type name. These three data table are available in an Excel format document by clicking the link at the bottom of each page. You will get the complete data table for all lithic samples by choosing to view or download on any of the data pages. The exposure type noted in the data tables and in the map keys are abbreviated. The following key identified the exposure type abbreviations.
Digitized Lithic Source Locations All known lithic sources located on individual county maps have been digitized so this information can be coupled with the Excel lithic inventory for a GIS format. With the creation of a GIS for the Lithic Raw Material Assemblage, data can be use with a variety of base maps including state department of transportation maps, 1:100,000 scale and 1:24,000 scale topographic maps. This has yielded a better picture of where our known lithic sources are. The Landform Regions of Iowa map will also be integrated into the GIS format for additional analytic potential. The current assemblage is the result of opportunistic sampling, leaving areas of the state possibly under represented or not represented at all. Additional samples are constantly being acquired and incorporated into the assemblage.
VBS Lithics Program (Under Construction)
Summary The OSA’s Lithic Raw Material Assemblage is focused on four main methods for future research: microscopic analysis, geologic thin sectioning, and use of the University of Iowa’s Scanning Electron Microscope (UI-SEM). Microscopic viewing, using a dissecting microscope, has been applied in order to take a close-in look at surficial characteristics. Magnification levels of x7-30 powers provide clear views for sample comparison however, these scopes cannot capture images for further analysis, report preparation, or future comparisons. We recently acquired a handheld digital microscope that connects to a computer via USB cable. The scope provides two magnification powers of x20 and x400 and allows the user the ability to capture images and save them as JPEG files. This type of scope is readily available and affordable from various manufacturers. We are in the process of acquiring a test set of images for the Pennsylvanian System and anticipate web posting in the coming months. Additionally, thin sections for six Pennsylvanian System samples are currently being processed for use in our assemblage as a result of collaborative research. Thin sections will provide the opportunity to study crystalline and optical characteristics. The University of Iowa’s Central Microscopy Research Facility (CMRF) provides Scanning Electron Microscope instrumentation and technical assistance. Using a Hitachi S 3400N we will be engaging in research to assess the viability of SEM application to the Lithic Raw Material Assemblage during the next year. Results will be posted to this web page. Macroscopic lithic analysis is a given in archaeological research and a collection of physical samples, geologically organized and geographically well documented, is a must. It is our belief that this assemblage will provide that resource. Since prehistoric artifact assemblages are so often dominated by lithic materials, a well-developed comparative assemblage could afford researchers the opportunity to address a myriad of issues including but not limited to trade, the movement of people, and social interactions. The physical, geological, and geographical revision/reorganization of this assemblage are complete and housed at the OSA lab. The web-based manifestation makes the OSA Lithic Raw Material Assemblage accessible from any place, throughout the Midwest, or even worldwide.
If you have any additional questions or comments about this page, or would like to discuss lithics with the authors, please feel free to contact either mark-l-anderson@uiowa.edu; or daniel-horgen@uiowa.edu. We would appreciate hearing from you.
The Iowa Geological Survey at the University of Iowa, a division of the Iowa Department of Natural Resources, provides the following resources. They have been integral in assisting our research efforts. The following selections have individual web page addresses at the end of each section. The Iowa Geological Survey’s home page is: The following is a brief summary of the bedrock history and development of the present surface. At the close of the Cretaceous Period the area which is now Iowa was a land surface. The soft Cretaceous deposits and older rocks were subjected to erosion. During the long Tertiary Period all the land was eroded to a surface with gentle slopes and a relief of about 200 feet. Before the end of the Tertiary time, change in the relative elevations of land and sea caused the streams to be rejuvenated and they developed new valleys. At the new grade, the streams widened their valley floor and weathering reduced the wall slopes to form a more rugged topography than before but still one with moderate slopes and with flat-topped divides at the level of the older surface. The new level is about 200 feet lower; this relief, added to that on the older surface, gives a total relief of about 400 feet. Over such a surface came the first ice sheet of the Pleistocene. The melting of the ice and dropping of the glacial debris left a new surface – a drift surface – superimposed over the bedrock surface. New drainage was inaugurated. This was modified by succeeding ice sheet invasions that buried the new valleys and more deeply covered the preglacial surface. Today, Iowa is a prairie state having a generally moderate relief and gentle slopes. In some places there are broad uplands, in other places the valley floodplain is conspicuous. In general, the state is well drained by tributaries of the Mississippi and Missouri Rivers at its borders. Some parts of the state show extensive erosion, whereas other parts show little erosion and have distinctive constructional features. It is difficult to say which is the more important in development of the topography – erosion or deposition. However, the origin of the present surface is related very closely to the glacial history of Iowa. Several kinds of topography can be differentiated. The Mankato and Cary drift in northcentral Iowa are depositional terrain. So are the alluvial bottoms of the Mississippi and Missouri Rivers and the loess deposit bordering the Missouri River flatland. The Mankato and Cary surfaces have some of the characteristics of extreme youth of the erosion cycle of glaciated area with valleys just being formed and relatively poor drainage. The surface of the Kansan drift area is much more rolling and approaches the stage of maturity. The Iowan and Tazewell surfaces are intermediate in development but probably more erosional than depositional. In the “driftless area” of northeast Iowa the surface is even more mature. http://www.igsb.uiowa.edu/gsbpubs/pdf/EM-02.pdf Iowa’s Stratigraphic Column http://www.igsb.uiowa.edu/gsbpubs/Stratigraphy/iastratcolumn4.asp Stratigraphic Column of Iowa, 2004 http://www.igsb.uiowa.edu/gsbpubs/pdf/EM-40.pdf Bedrock Geology map of Iowa, 1998 http://www.igsb.uiowa.edu/gsbpubs/pdf/EM-19.pdf
http://www.uiowa.edu/~osa/geo/geo.htm
Bedrock geology of northwest Iowa, Digital geologic map of Iowa, Phase 1: Northwest Iowa, B. J. Witzke, G. A. Ludvigson, R. R. Anderson, B. J. Bunker, M. K. Slaughter, J. D. Giglierano, J. P. Pope, T. M. Whitsett, and M. J. Bounk, 1997, scale 1:250,000; contract completion report to U.S. Geological Survey for Assistance Award No. 1434-HQ-96-AG-01486, August 1997.
Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-1997-1.pdf Bedrock geology of northeast Iowa, Digital geologic map of Iowa, Phase 2: Northeast Iowa, B.J. Witzke, G. A. Ludvigson, R. M. McKay, R. R. Anderson, B. J. Bunker, J. D. Giglierano, J. P. Pope, A. E. Goettemoeller, and M. K. Slaughter, 1998, scale 1:250,000; contract completion report to U.S. Geological Survey for Assistance Award No. 1434-HQ-97-AG-01719, August 1998.
Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-1998-7.pdf Bedrock geology of north-central Iowa, Digital geologic map of Iowa, Phase 3: North-Central Iowa, B. J. Witzke, R. R. Anderson, B. J. Bunker, G. A. Ludvigson, and S. Greeney, 2001, scale 1:250,000, supported by Cooperative Agreement 00-HQAG-0075, May 2001.
Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-2001-3.pdf Bedrock geology of south-central Iowa, Digital geologic map of Iowa, Phase 4: South-Central Iowa, J. P. Pope, B. J. Witzke, R. R. Anderson, G. A. Ludvigson, B. J. Bunker, and S. Greeney, 2001, scale 1:250,000, supported by Cooperative Agreement 010-HQAG-0091, July 2002.
Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-2002-1.pdf Bedrock geology of southwest Iowa, Digital geologic map of Iowa, Phase 5: Southwest Iowa, B. J. Witzke, R. R. Anderson, B. J. Bunker, and G. A. Ludvigson, 2003, scale 1:250,000, supported by Cooperative Agreement 02-HQAG-0034, September 2003.
Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-2003-1.pdf Bedrock geology of east-central Iowa, Digital geologic map of Iowa, Phase 6: East-Central Iowa, B. J. Witzke, R. R. Anderson, B. J. Bunker, and G. A. Ludvigson, 2003, scale 1:250,000, supported by Cooperative Agreement 02-HQAG-0034, September 2003. Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/OFM-2003-2.pdf Bedrock geology of southeast Iowa, Digital geologic map of Iowa, Phase 7: Southeast Iowa, B. J. Witzke, R. Anderson, and B. J. Bunker, 2004, scale 1:250,000, supported by Cooperative Agreement 03-HQAG-0087, September 2004. Map: http://www.igsb.uiowa.edu/gsbpubs/pdf/ofm-2004-1.pdf
Mary De La Garza, Web Master June 2009
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