NATURAL FORMATION PROCESSES OPERATING ON SURFACE LITHIC SCATTERS IN THE MOUNTAINS: AN EXPERIMENTAL STUDY

In the spring of 2001, two hundred aluminum tags were scattered on the surface of the Mountaineer site (5GN2477) near Gunnison, Colorado. The initial tag locations were recorded using an EDM total station. Tags were rediscovered and point-located eight times over four years since their initial placement. In the first few weeks after their initial distribution, many tags were displaced several centimeters. In the following months and years the tags continued their wandering to show a final mode of about 15 cm from their initial point. With time, the total distance increased but the rate of change decreased probably from a “settling in” of the tags. Through time increasing numbers of tags became buried and disappeared from sight.

Several tags were moved great distances up to 130m. Causes for greater movement include foot traffic, automobile traffic, and movement and collection of the tags by visitors to the site. These same processes affect the distributions of archaeological materials, just as wind, rain, and freeze-thaw processes do.

Implications of this study are that populations of artifact distributions reflect prehistoric depositional locations at some scales but probably not on a millimeter scale. A week-old scatter of tags is not in the same places it was at its creation. In fact, a camp occupied for several weeks may see artifact locations altered by natural and cultural processes during occupation. Therefore highly detailed mapping (at the sub-millimeter level) of individual artifacts might be an over-zealous pursuit of accuracy. On the other hand this study does indicate surface lithic scatters may retain spatial integrity after considerable time spans.

Patterns of tag movement in this short-term study give insight into long-term site-formation processes, interpretation of artifact provenience, and appropriate excavation methods at the Mountaineer Folsom site.