Plains Anthropological Conference
Rapid City, South Dakota
Visitors since 4 October, 2007
Lubow, Amanda (Colorado State University)
Session 19. Don't tread on me: Effects of Cattle Trampling on Burned Archeological Sites of the Upper Greybull River, Wyoming
An improved understanding of the impacts of domestic animal grazing on archeological sites needs to be developed for both land managers and archeologists to fully address the range of modifications that fire can have on the archeological record. The Greybull River Sustainable Landscape Ecology (GRSLE) project investigates a range of biological, physical and cultural impacts to archeological sites along the Greybull River drainage, which is located in the Shoshone National Forest of northwestern Wyoming. The 2006 Little Venus Fire opened a narrow window of opportunity for archeologists to investigate the effects of forest fires on archeology. Data collection for this project was conducted during the 2007 summer field season. Three hundred and twenty-eight square meters were surveyed for cattle footprints. Those footprints were then recorded in terms of location, maximum length, width and depth. A block sampling design covering 168 m2 of burned mountain grassland was recorded and coupled with an adjacent plot covering 100 m2 of unburned grassland. Neither block sample contained previously recorded archeological material. A linear transect sampling design was applied on two known sites. On one site, a 25-m2 section was recorded and on the other, a 35-m2 section was recorded. Approximately 25% of each transect was outside of the burned area. This research provides a basis for evaluating management strategies and working towards a more integrated approach for understanding the effects of cattle grazing and other post-fire impacts on recently burned archeological sites.
Understanding the characteristics of unintended thermal alteration to chipped stone is fundamental to evaluating many aspects of archaeological sites. Developing a set of criteria to help identify unintended heat alteration to chipped stone can aid in intra- and inter-site comparisons. The better our ability to recognize unintentional heat alteration characteristics, the more accurately we can segregate intentional human involvement in the use of heating in the manufacturing of stone tools prehistorically from other forms of heat alteration. Heat altered chipped stone was examined in the Upper Greybull area of northwestern Wyoming's Shoshone National Forest. The Little Venus Fire of 2006 fueled large-scale surface burning of grassland and patches of timber which improved the surface visibility of archaeological materials, allowing for intensive observations to be made of lithic debitage on archaeological sites. The juxtaposition and dimensions of over thirty heat altered fragments of chipped stone were documented paying special attention to the intensity of heat alteration, the effect of heat altering that had taken place, the material of the chipped stone, and the area of displacement caused by the materials' reaction to heating and the exerting of energy. The spalled and thermally fractured artifact sample included a range of fracture types (i.e., potlids, crazing, spalling), fracture intensity, distances between fractured pieces (with a maximum potlid distance of >4 m recorded), and frequency of thermally altered artifacts across the region.
Landslides occur in great frequency in northwestern Wyoming. More than half of the archaeological sites in the Upper Greybull River region of the Central Absaroka Range are associated with a mass-wasting feature. This study includes a detailed examination of one site impacted by depositional sequences associated with a slump/debris flow feature. The landscape activity at site 48PA2811 is currently destroying parts of the site, but past activity has helped in preserving an environmental history of the site over the last 2500 years. Results from soil analyses, geomorphic mapping, and radiocarbon dating show a cyclic change of landscape disturbance and recovery through time. The results of this investigation are compared to regional data to offer insight into landscape change and archaeological patterning in northwestern Wyoming.
One obvious impact of forest fires is the production of thousands of sharp-edged heat spalls that in some places blanket the ground with a scatter of fragments up to several meters away from their source rock. Developing a better understanding of these spalls adds to our understanding of archaeological site formation and regional geoarchaeology. These topics were addressed in 2007 through field research in the Shoshone National Forest, north western Wyoming, in the area of the Greybull River drainage where a year earlier the Little Venus fire cleared out much of the forested area. There seem to be three main factors: 1) the thermal environment of the rock; 2) the composition of the rock; and 3) the water content of the rock. A thermal spall results from an explosive fracture of the rock's surface. A sample of 30 spalled rocks was selected for documentation and analysis. Specimens within this sample differed in three ways: the size of the rock, how much of its outer shell had been spalled, and the distance that the fragment was displaced. For each spall in the sample maximum length, width, and thickness was measured. Sample plots consisted of four 200x50 cm transects that spanned the four cardinal directions (north, east, south, and west). This research complements other approaches for understanding regional prehistoric site formation patterns and fire histories studies.
During the summer of 2007, archaeological surveys were conducted in the Absaroka Mountain range, northwestern Wyoming. Wildland fires from 2006 had altered the landscape, leaving behind traces that, in some cases, emulated those left by humans. Instead of ubiquitous burning across the surface of the landscape, naturally occurring fires created discrete patches of oxidized sediments using the fuel provided by root systems of shrubs and trees while thermally altering the soil, rock, and cultural material within the burn areas. Further, lithic artifacts and naturally occurring stones exposed to high levels of heat during these fires went through the same physical changes of thermal alteration by fracturing and spalling that would be expected to occur in humanly produce hearths. The data collected from these are used to test the hypothesis that individual burnt remains within archeological sites could be naturally produced. Before human controlled use of fire on archaeological sites can be ascertained it is crucial to measure the taphonomic processes associated with naturally occurring fires. Understanding these processes aids in analyzing how fire affects the formation and alteration of archaeological sites and ultimately in refining our ability to identify hearths in a wide variety of settings.