WHAT I STUDY: A STATEMENT OF RESEARCH INTERESTS

Donald M. Thieme, Ph.D

My research centers on Quaternary stratigraphy and its explanation in terms of fundamental Earth processes. Since completing my Ph.D in 2003, I have undertaken several small projects which involve students while continuing to present and publish the results of my dissertation. In my dissertation, I developed an allostratigraphic framework for postglacial alluvium of the Susquehanna River in northeastern Pennsylvania, relying primarily upon stratified archaeological sites (Thieme, 2003a). Geoarchaeology is thus another major research interest, and my research includes studies of the raw materials from which artifacts were made (e.g. Thieme et al., 2000) as well as studies of the strata in which artifacts were found.

In addition to publications in both books and peer-reviewed journals, I have written over 50 reports on the stratigraphy of archaeological sites, examples of which I have posted in a geoarchaeology section of my webpage at Georgia Perimeter College. These studies all relate the layers that contained the artifacts to soil development, to landscape changes, and to the bedrock and sediment "packages" of the region surrounding each archaeological site. I presented a paper summarizing my dissertation results at the most recent annual meeting of the Geological Society of America (Thieme, 2006a), and that will be published along with other select papers from that session in a GSA Special Publication.

Quaternary geology and geoarchaeology make use of many specialized research methods in geology and other natural sciences. My dissertation made use of geochronology, geomorphology, soil mineralogy, environmental magnetism, and low-temperature geochemistry. The geochronological part of my dissertation research was to apply the most recent calibration for the radiocarbon time scale to a population of 129 dates. I found that calibration stretched out the close of the Pleistocene epoch, when the Laurentide ice sheet retreated through the reaches studied. Several abrupt cooling events during the Holocene epoch also influenced the abundance of ¹⁴C in the atmosphere. Climatic forcing of the carbon cycle therefore continued into the period when Native Americans inhabited this river valley.

I studied the mineralogy of buried soils that formed in Susquehanna Valley alluvium, particularly the vermiculite and illite soil clays (Thieme, 2003b). This part of my research combined soil micromorphology, the petrographic examination of soils in thin section, with x-ray diffraction and bulk chemical analysis on an ICP system. I concluded that the mineral represented by a 14 angstrom d-spacing in the x-ray diffraction pattern was hydroxy-interlayered vermiculite that formed as the sediment weathered to form the buried soils. I have continued to apply all of these same mineralogical methods to more strongly developed paleosols formed during interglacial intervals of the Quaternary period.

I became interested in environmental magnetism both through studying buried soils and paleosols in my dissertation research and through using magnetometers to identify cultural features on archaeological sites. During my dissertation research, I used the susceptibility bridge at the University of Georgia to measure 57 samples from northeastern Pennsylvania. I then pursued several research questions about these initial results by measuring anhysteric remanent susceptibility (ARM), hysteresis loop parameters, low-temperature transitions, and frequency dependent susceptibility at the Institute for Rock Magnetism of the University of Minnesota (Thieme, 2004). I focused these measurements upon two profiles with multiple buried soils for which I have radiocarbon age control as well as mineralogical information from micromorphology, x-ray diffraction, and bulk chemistry.

I used the morphology as well as the mineralogy of the buried soils to establish my stratigraphic framework, an "allostratigraphic" approach which I share with many other Quaternary stratigraphers and geomorphologists. Valley-wide episodes of deposition were punctuated by intervals of non-deposition and soil formation. The timing of these episodes corresponds to regional environmental change for which there is independent evidence from pollen, lake levels, and other proxy records. The North Branch of the Susquehanna River valley also shows a prominent imprint from slightly more than four centuries of Euroamerican settlement.

In both my dissertation and in several publications (Thieme, 2001, 2003c; Thieme and Schuldenrein, 1998), I have taken advantage of my previous training and education as an archaeologist to relate fluvial, coastal, and upland interior environmental change to direct and indirect human impacts. At the scale of the individual archaeological site, I have been able to identify chemical residues of specific human activities in cultural features and cultural sediments. My specific knowledge of soil chemistry as well as my long-term perspective on human environmental impact has been very helpful for teaching my environmental science class as well as continuing work as a consultant to archaeologists. I am now working with Dennis Blanton, an archaeologist at the Fernbank Museum in Atlanta, in his investigation of sites he thinks may be associated with the 17^th century Spanish mission Santa Isabel de Utinahica along the Ocmulgee River in south central Georgia. I have been part of a multidisciplinary team which is describing the stratigraphy, soils, and coring wetland bogs. We recently obtained a basal radiocarbon age of 38,700 +/- 420 years B.P. for an alluvial section at Coffee Bluff (Thieme et al., 2007), next to one of our possible candidates for a Spanish presence in south central Georgia.

At both Ossabaw Island on the Georgia coast (Thieme, 2005) and Governors Island in New York Harbor (Thieme et al., 2004), I continue to investigate relationships between historic and prehistoric human activity and coastal environmental change. In addition to archaeological contexts and radiocarbon dates, we have begun to use luminescence and other cutting-edge Quaternary dating methods for the study of Quaternary shorelines in the eastern United States (Thieme, 2006b). On Governors Island, I found shoreface sands inland of the present shoreline that I plan to date with luminescence at the conclusion of a brief field season this coming summer. In both of these projects as well as in my work with Dennis Blanton along the Ocmulgee River, I used ArcGIS to overlay historic maps and aerial photographs on topographic contours, soils, and physiographic features.

Several locations which I have used for student field trips continue to hold my interest and may be used for future research with students. I currently lead trips to Stone Mountain every semester, and I am particularly interested in the soils that have formed on different rock types in the park as well the different exposure ages of landforms in the Georgia Piedmont. I recently completed some research on stratigraphy and paleontology of Eocene limestone at the CEMEX quarry in middle Georgia (Thieme, 2007). Some of my students at both Georgia Southern University and Georgia Perimeter College participated in my fieldwork there.

REFERENCES CITED

Thieme, Donald M., 2001, Historic and possible prehistoric impacts on floodplain sedimentation, North Branch of the Susquehanna, Pennsylvania, U.S.A. In D. Maddy, M. G. Macklin, and J. C. Woodward (Eds.), River Basin Sediment Systems, p. 375-403: Rotterdam: Balkema.

Thieme, Donald M., 2003a, A Stratigraphic and Chronometric Investigation of the Alluvial Deposits of the North Branch of the Susquehanna River. Ph.D. dissertation, University of Georgia, Athens.

Thieme, Donald M., 2003b, Detrital and pedogenic mineral phases in a buried soil formed in Susquehanna River alluvium of mid-Holocene age. In Classic Clays and Minerals. Program and Abstracts of the Clay Minerals Society 40th Annual Meeting, p. 151. Athens, Georgia.

Thieme, Donald M., 2003c, Archaeological site formation in glaciated settings, New Jersey and southern New York. In D. L. Cremeens and J. Hart (Eds.), Geoarchaeology of Landscapes in the Glaciated Northeast, p. 163-179. New York State Museum, Albany.

Thieme, Donald M., 2004, Environmental magnetism of Susquehanna Valley alluvium. The IRM Quarterly, v. 13, no. 4, p. 4-5.

Thieme, Donald M., 2005, Soils and Geomorphology of the Tabby Site (9Ch1062), Ossabaw Island. Appendix to Final Report published by the Lamar Institute, Athens, Georgia.

Thieme, Donald M., 2006a, Bounding discontinuities in Susquehanna Valley alluvium - Using stratigraphy to reconstruct prehistoric landscapes and archaeological site formation. Annual Meeting, Geological Society of America, Philadelphia, Pennsylvania, GSA Abstracts, v. 38, no. 7, p. 453.

Thieme, Donald M., 2006b, Talbot shoreline at Mount Pleasant. In T. M. Chowns (Ed.), Quaternary Stratigraphy and Depositional Environments - Jekyll Island and the Golden Isles Parkway, p. 80-83. Georgia Geological Society, Atlanta, Georgia.

Thieme, Donald M., 2007, Jacksonian cheilostomatous bryozoa from the Tivola ("Ocala") limestone in the CEMEX quarry, Houston County, Georgia Journal of Science, in press.

Thieme, Donald M., and Schuldenrein, Joseph, 1998, Wyoming Valley Landscape Evolution and the Emergence of the Wyoming Valley Culture. Pennsylvania Archaeologist, v. 68, no. 2, p. 1-17.

Thieme, Donald M., Thieme, Mary S., Neff, Hector, and Elam, J. Michael, 2000, Geochemical, mineralogical, and petrographic analysis of ceramic raw materials derived from feldspathic rocks in the vicinity of Monte Albàn, Oaxaca, Mexico. 32^nd International Symposium on Archeometry, Mexico City, Mexico, Abstracts, p. 117-118.

Thieme, Donald M., Schuldenrein, Joseph, Herbster, Holly, and Schabel, Mary Jo, 2003, As You Were - Finding the Island and the People in Governors Island. GSA. Annual Meeting, Geological Society of America, Seattle, Washington, GSA Abstracts, v. 35, no. 6, p. 227.

Thieme, Donald M., Blanton, Dennis, and Snow, Frankie, 2007, A late Pleistocene to Holocene alluvial section at Coffee Bluff on the Ocmulgee River. 56^th Annual Meeting, Southeastern Section, Geological Society of America, Savannah, Georgia.