Table 1. Results of pollen analysis between groundstone surface and sediments overlying Figure 2. 5LA11455 site overview (left) and bedrock grinding feature overlaid by packrat midden (right). Figure 1. Chacuaco Groundstone Project Area in Southeastern Colorado. Figure 4. Laura Holthus extracting midden sample LITERATURE REVIEW Woodrats, also known by the generic term Dzpack ratdz, are a species well documented for their ability to collect and protect evidence of localized environments and changes to those environments (Armstrong 1972; Betancourt 1990; Dial and Czaplewski 1990; Fitzgerald et al. 1994; Jackson et al. 2005; Van Devender et al. 1990). There are over twenty species of woodrats (genus Neotoma) in North America some of whom are extremely well adapted for specific environments others are more generalized in their foraging behavior (Finley 1990; Smith and Betancourt 2006; Smith et al. 1995; Vaughan 1990). Three species of Neotoma in Las Animas County, Colorado share this canyon habitat: N. albigula, N. mexicana, and N. micropus (Armstrong 1972; Fitzgerald et al. 1994; Lechleitner 1969). When territories overlap, each species falls back on specific trophic strategies which make it possible to determine the resident species without live-trapping individuals. Knowledge about species behavior helps in the interpretation and analysis of residence construction and land use which in turn helps in interpretation of human activity on the site. This information is useful to understand how FS14 (a ground stone tool found during the removal of the indurated pack rat midden) ended up as part of a pack rat midden. It is likely that the most recent woodrat species to inhabit this rockshelter is a type of N. albigula. While the shape and location of the residence will depend on the presence or absence of other woodrat species and the available resources, Dzin rocky country, houses are typically constructed under overhanging rock or in piles of fallen rocksdz ȋArmstrong 97:5Ȍ. Their residence is constructed from a wide range of available local materials including juniper, sticks, bones, grasses and covered with cactus thorns (Armstrong 1972). These materials and a host of other local materials were found within the larger midden investigated during this study. RESEARCH PROBLEM Prehistoric peoples created milling surfaces on exposed bedrock outcrops in the canyon landscape of southeastern Colorado (Figure 1). The bedrock grinding cultural phenomena of southeastern Colorado, as evidenced by the archaeological remains, is wide spread from south of the Arkansas River to the Cimarron river in Northeastern New Mexico (Bender 1990; Campbell 1969; Gunnerson 1989; Hartley and Vawser 2003; Loendorf 2008; Loendorf et al. 1996; Owens 2000; Renaud 1941). Though the length and breadth of this regional cultural expression is poorly understood at this time, the ubiquitous use of stationary grinding implements in the bordering southwest suggests that these features may have been used in a similar manner - perhaps for grinding corn grown in the Chacuaco floodplain or dry farmed along the upper rims of the canyons. However bedrock surfaces have been used throughout California, Arizona, Nevada, Texas and areas of the southeastern United States to process a variety of wild foods (e.g. acorn and locally harvested nuts) (Meighan et al. 1953; True 1993; Webb and Funkhouser 1929). With little direct evidence as to the time of use or the foods being processed there is little to suggest whether wild foods or domesticated foods were processed. Evidence, gathered from the localized woodrat middens at 5LA11455, makes it possible for the first time to test our assumptions about the use and environment of ground bedrock surfaces in the Chacuaco drainage (Figures 2). Southern Plains Grinding Landscapes: Can a local wood rat midden inform us about prehistoric human grinding work spaces and behavior at a Colorado Rockshelter? Elizabeth M. Lynch 1 , Laura Holthus 2 , and Kimberly Sanchez 3 1,2,3 University of Wyoming, Department of Anthropology DISCUSSION AND CONCLUSION The results of project clearly help to build a picture of the local environment at 5LA11455 and raised additional challenges to our understanding of prehistoric grinding landscapes. Removing a sample of the more recent midden and uncovering other ground bedrock surfaces – especially the highly eroded surfaces – raises the question of whether or not this site may have had multiple uses. It also raises concerns that the processes caused during one occupational time period might have been erased or partially overwritten by latter processes (natural and human) on the same boulder. Before the SIS project we had no evidence to suggest this shelter was inhabited before 1,000 years ago. Rock art seriation suggests the site was occupied between 900 – 500 BP (Loendorf 2008). However, the results of the pollen analysis, which show a significant change in vegetation between the occupation ground surface and the post occupation sedimentation, combined with the eroded condition of some of the grinding surfaces, hint at an earlier use of the site or highly erosional post-occupation environments. The sampling of the two pack rat middens at 5LA11455 has expanded our understanding of the local environment in which the ground bedrock surfaces were created and preserved. The evidence strongly suggests a change in vegetation from the last time the surfaces were used but does not provide conclusive evidence as to what was type of food was being processed on the bedrock surfaces. Our understanding of the function and meaning of this grinding space is still in formative stages. The results of the pollen analysis suggest this site represents occupations over a longer period of time than previously thought however it does not provide definitive evidence for resources ground. It is only through continued investigation of these bedrock grinding sites that we will be able to build a complete picture of how prehistoric peoples inhabited these work landscapes. Figure 5. Groundstone basin sediment and pollen wash sampling. Acknowledgements This poster is part of a Summer Independent Study Project funded by the College of Arts and Sciences at the University of Wyoming. We would like to thank Mr. Jerry Wenger for permission to work on his property and to the ranch personnel for their assistance. The CRAA provided field support and technical support which contributed greatly to the success of this work. Additional funding was been provided by The American Association of Photogrammetry and Remote Sensing and The Frison Institute (Rhoda Lewis Award). We would like to express our appreciation to Drs. Larry Loendorf, Mary Lou Larson, Tom Minckley and Todd Surovell for inspiration, assistance in fundraising and for help with the final report. RESULTS The midden materials are composed of a mixture of local plant life including oak (leaves, sticks and acorns), pinon pine (sticks and cones), various grasses, cholla (fresh and desiccated fruit pods), vines from an wild grape, and other cactus, mountain mahogany, juniper (leaves, sticks, and berries). In addition there were several large mammal bones – some gnawed beyond recognition – and the cranium of a small adult snake, species unknown, as well as small reptilian vertebrae. The sediments consist of a sandy loam – very fine sediment, probably windblown – and interspersed with small grasses, herbs and other fine materials. Though beyond the scope of this project, these samples may yet add to our understanding of the manner in which sediments collect and are dispersed within the woodrat matrix and how pollen is distributed in this rockshelter. Table 1 presents the raw counts of the pollen samples collected from the sediments the basin of the bedrock ground surface (representing the post-occupation sedimentation) and the pollen collected from the washes of the basin surface (representing the occupation level) were used to test the hypothesis that there was no change in the local environment between the time of occupation and that of post occupation period. We assumed that the sedimentation process was constant and that minimal erosion had occurred because of the protected nature of the rockshelter and the protective case created by the woodrats over the sediments. The pollen from the basin sediments differs significantly from that of the pollen wash in both ground surfaces sampled indicating a difference between the local vegetation at the time of occupation and after the ground bedrock surfaces stopped being used (report in progress). Additionally no pollen for zea maize (corn) was found in either ground surfaces sampled. This does not negate the Cummings and Varney (2009) findings, which indicated corn pollen on one of the same ground stone surfaces tested in the current study, but it does raise the question of why there is a different in the presence of corn on the same ground bedrock surface. Family Name FS20 FS24 FS44 FS45 Abies 0 0 1 0 Cupressaceae 94 197 81 196 Picea 0 1 1 0 Pinus undiff 109 23 72.5 24 Pinus Di 4 2 9 3 Pinus Ha 0 1 0 0 Quercus 12 6 13 11 Amelanchier 3 1 0 0 Artemisia 22 20 35 10 Ambrosia 5 1 3 1 Ceanothus 0 1 1 1 Celtis 1 0 0 0 Rosaceae 1 5 5 1 Amaranthaceae 27 19 28 35 Apiaceae 1 1 1 0 Asteraceae 16 19 26 23 Brassicaceae 0 0 1 0 Fabaceae 1 1 0 0 Poaceae 15 10 24 14 Polygonaceae 0 1 1 0 Selaginella 2 0 2 1 Populus 0 1 0 5 Typha latifolia 1 0 0 0 Typha_Sparganium 1 0 0 0 Tracer 12 4 4 6 METHODS Field work was conducted on private property along the Chacuaco Creek with the permission of Mr. Jerry Wenger, the owner (Figure 3). 5LA11455 had been reported by the CRAA 2007 survey of the ranch; that recording had focused on the rock art panel on the south wall of the rockshelter. The 2011 fieldwork focused on developing a scale map of the pack rat midden, the rockshelter, and the boulder surfaces (Figure 6). The woodrat residence was constructed into the deep crevice created by the gradual separation of the ceiling and the floor and was probably created sometime after the site was abandoned most likely within the last 100 -150 years based on the loose connectivity of the midden and the presence of greenish juniper (Steve Jackson personal communication 2011). Removal of the midden samples took place in two stages: the first included the sampling of the larger, more recent midden (Figure 4) while the second included the extraction of a smaller indurated midden adjacent to the groundstone surfaces. The sampling unit was set up over the ground stone surfaces that were covered by the midden and subsequent windblown sediments. Materials were double bagged for transport to UW. The final stage of the field work for the project was to extract the compacted sediments that had been deposited on the ground surfaces and to collect a wash from the surface. We hoped that pollen collected in the groundstone basin had been protected from erosion by overlaid sediments and the pack rat midden and could be used to determine the difference between occupation (surface pollen wash) and post-occupation (sediments immediately overlaying the surface) (Figure 5). We removed the compacted sediments in quasi-controlled levels. The upper most sediment consisted of compacted sandy loam sediments mixed with woodrat fecal pellets. At some point in the past the sediments had been loosened, mixed with fresh or dried pellets deposited by wind or the current residents of the den, then moistened and packed into the observed fill. We collected this fill. We then extracted the layer of sediment that directly overlay the ground surface, generally less than half a centimeter in depth. After completely extracting the sediments, we then used distilled water with less than one percent diluted muriatic acid to wash the basin of the ground surface. We collected the resulting mixture using plastic pipettes. This was gradually piped into sterilized plastic containers, labeled with the site number, date, unit (ground surface identifier) number and field specimen number. We continued this process until the water ran clear of mud and debris. The surface was again sprayed with water then agitated using a sonic toothbrush in order to loosen the sediment and any pollen found within the porous structure of the sandstone. We collected five samples of the pollen wash including a final purifying rinse of the tooth brush bristles. Upon completion of the site recording and sample extraction we re-buried the excavated surfaces with standard yard sand . The samples collected from the main midden (PRM1) were screened through one-half inch, one-quarter inch and one- sixteen inch hardware mesh to separate the thorny matrix from the other construction materials. I catalogued and processed the pollen washes and sediments then turned them over to Dr. Tom Minckley in the Botany Department for analysis (report in prep). Other midden samples were sorted by Kimberly Sanchez (Figure 7) . REFERENCES CITED 1. Armstrong, David Michael 1972 Distribution of Mammals in Colorado. University of Kansas. Museum of Natural History. Monograph, No. 3. University of Kansas Printing Service, Lawrence, Kansas. 2. Bender, Marilyn 1990 Chapter X: Groundstone Analysis. In An Introduction to the Archaeology of Pinon Canyon, Southeastern Colorado edited by William Andrefsky, pp: 1-43. Larson-Tibesar Associates and Centennial Archaeology. National Park Service Rocky Mountain Regional Office Interagency Archaeological Services, Denver. 3. Betancourt, Julio L.1990 Late Quaternary Biogeography of the Colorado Plateau. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 259-293. The University of Arizona Press, Tucson. 4. Betancourt, Julio L., Thomas R. van Devender and Martin Rose 1986 Comparison of Plant Macrofossils in Woodrat (Neotoma Sp.) and Porcupine (Erethizon Dorsatum) Middens from the Western United States. Journal of Mammalogy 67(2):266-273. 5. Campbell, Robert Gordon 1969 Prehistoric Panhandle Culture on the Chaquaqua Plateau, Southeast Colorado. Ph.D. dissertation, University of Colorado, Department of Anthropology, Boulder. 6. Cummings, Linda S and R A Varney 2009 Pollen, Starch and Organic Residue (Ftir) Analysis of Bedrock Mortars from 5la11455, Colorado. Paleo Research Institute. 7. Dial, Kenneth P. and Nicholas J. Czaplewski 1990 Do Woodrat Middens Accurately Represent the Animals' Environments and Diets? The Woodhouse Mesa Study. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 43-58. The University of Arizona Press, Tucson. 8. Finley, Jr., Robert B. 1990 Woodrat Ecology and Behavior and the Interpretation of Paleomiddens. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 28-42. The University of Arizona Press, Tucson. 9. Fitzgerald, James P., Meaney Carron A. and David Michael Armstrong 1994 Mammals of Colorado. Denver Museum of Natural History and University Press of Colorado, Denver. 10. Gunnerson, James H. 1989 Apishapa Canyon Archaeology Excavations at the Cramer, Snake Blakeslee, and Nearby Sites Reprints in Anthropology 41. J & L Reprint Company, Lincoln. 11. Hartley, Ralph J. and Anne M. Wolley Vawser 2003 Rockshelters, Rock Art, and Grinding Activity: A Preliminary Assessment of Relationships in Picket Wire Canyonlands, Comanche National Grasslands. Midwest Archaeological Center National Park Service. 12. Jackson, Stephen T., Julio L. Betancourt, Mark E. Lyford, Stephen T. Gray and Kate Aasen Rylander 2005 A 40,000-Year Woodrat-Midden Record of Vegetational and Biogeographical Dynamics in North-Eastern Utah, USA. Journal of Biogeography 32(6):1085-1106. 13. Lechleitner, R. R. 1969 Wild Mammals of Colorado: Their Appearance, Habits, Distribution, and Abundance. Colo., Pruett Pub. Co., Boulder. 14. Loendorf, Lawrence 2008 Hunting, Grinding, and Dancing: Petroglyph Sites on the J.E. Canyon Ranch, Southeastern Colorado. Colorado Rock Art Association, Colorado Historical Society. 15. Loendorf, Lawrence , Borchert Jeani L., Klinner Duane G. and Ahler Stanley A. 1996 Archeological Investigations at Ceramic Stage Sites in the Pinon Canyon Maneuver Site, Colorado. Contribution Dept. Of Anthropology, University of North Dakota, Grand Forks. 16. Lynch, Elizabeth M., Matthews Neffra and Lawrence Loendorf 2007 Imagery and the Landscape of Workspace: Exploring Techniques to Define the Relationship between Rock Art and Groundstone. Presented at the Plains Conference, Laramie Wyoming. 17. Meighan, Clement Woodward, D. Fredrickson and Albert Mohr 1953 Ground Stone of the Napa Region, Excluding Site Nap-1. Heizer, Robert F : Archaeology of the Napa region p. 18. Owens, Mark 2000 Archaeological Sites Inventory in the Black Hills of the Pinon Canyon Maneuver Site, Las Animas County Colorado. Fort Carson Cultural Resource Management Series. Directorate of Environmental Management and Compliance, Dept. of the Army, Fort Carson, Colo. 19. Renaud, E. B. 1941 Classification and Description of Indian Stone Artifacts. The Colorado Archaeological Society, Gunnison. 20. Smith, Felisa A. and Julio L. Betancourt 2006 Special Issue: Predicting Woodrat (Neotoma) Responses to Anthropogenic Warming from Studies of the Palaeomidden Record. Journal of Biogeography 33(12):2061-2076. 21. Smith, Felisa A., Julio L. Betancourt and James H. Brown 1995 Evolution of Body Size in the Woodrat over the Past 25,000 Years of Climate Change. Science 270(5244):2012-2014. 22. Spaulding, W. Geoffrey, Julio L. Betancourt, Lisa K. Croft and Kenneth l Cole 1990 Packrat Middens: Their Composition and Methods of Analysis. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 59-84. The University of Arizona Press, Tucson. 23. True, D. L. 1993 Bedrock Milling Elements as Indicators of Subsistence and Settlement Patterns in Northern San Diego County, California. Pacific Coast Archaeological Society Quarterly 29(2):1-26. 24. Van Devender, Thomas R., Laurence J. Toolin and Tony L. Burgess 1990 The Ecology and Paleoecology of Grasses in Selected Sonoran Desert Plant Communities. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 326-349. The University of Arizona Press, Tucson. 25. Vaughan, Terry A. 1990 Ecology of Living Packrats. In Packrat Middens: The Last 40,000 Years of Biotic Change, edited by Julio L. Betancourt, Thomas R. Van Devender and Paul S. Martin, pp. 14-27. The University of Arizona Press, Tucson. 26. Webb, W. S. and W. D. Funkhouser 1929 The So-Called "Hominy Holes" Of Kentucky. American Anthropologist, New Series 31(4):701-709. Figure 6. Field map of groundstone surfaces and midden sample. Figure 7. Pic of Kimberly. Figure 3. Location of fieldwork; Black arrow points to 5LA11455.