North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: Kaplan-Hoover, CO (5LR3953) ;
Reference: Kenneth L. Kvamme (2000). Geophysical Explorations at the Kaplan-Hoover Site (5LR3953), Larimer County, Colorado. Report prepared for Department of Anthropology, Colorado State University, Fort Collins, Colorado.
The Kaplan-Hoover site (5LR3953) is an Archaic period bison kill site that made use of an arroyo trap. The site occurs within a new housing development in ground disturbed by major earth moving activities (which led to the discovery of the site). The location of this work was guided by Dr. Jeffrey L. Eighmy of the Department of Anthropology, Colorado State University, who assisted with the survey, together with Dr. Kenneth J. Berry of the Department of Sociology. The surveys were conducted within a small 20 x 20 m block immediately to the south of the CSU excavation units, central bone bed, and a hut erected over the excavations. It was surmised at the time of the survey that the arroyo, and associated bone bed, might split into two forks immediately south of the excavation and extend for some distance to the southwest and southeast into the large terrace on which the site occurs. This terrace slope at the site is largely artificial, created by earth-moving machines, a factor that affected the nature of the survey results. The purpose of the survey was to employ geophysical techniques to hopefully obtain indications of the arroyo or bone bed in order that it could be mapped and possibly guide future excavation directions.
Two geophysical techniques were employed for the surveys that were best-suited for the study plot and problem. Because of the large slope and possible diving deposits in the study grid the need for deep prospecting was considered, and deep resistivity and ground penetrating radar methods were therefore selected. The size of the archaeological features to be discovered, namely an arroyo and/or bone bed, allowed relatively coarse sampling to be employed by the surveys. The resistivity data were sampled every 0.5 x 1.0 m and the GPR survey was run in 10 parallel, east-west transects of 20 m length, each separated by 2 m.
A tremendous gradient occurs in the resistivity data, undoubtedly due to the steep artificial slope in the study area that probably cross-cut natural deposits and their associated moisture content. Two zones of low resistance can be seen in the northwest and northeast corners of the study block. This is exactly the kind of response one would expect from buried arroyo deposits because such buried features can posses a higher ground moisture regime. This occurs because the ancient channel and contact can concentrate a greater level of ground moisture. This phenomenon is illustrated by the half-meter wide drainage channel excavated by the archaeologists across the study block, the only other significant feature in the data. Its low indicated resistivity probably stems from higher ground moisture resulting from recent rainfall. The findings of the ground penetrating radar survey were very unclear, however. While numerous GPR anomalies are indicated in the data they lack strong indication of a coherent pattern or agreement with the resistivity findings. Most of the anomalies probably arise from plant roots or other natural factors like soil cracks, rodent burrows, rocks, or surface variations. Several are derived from the shallow drainage ditch that bisect the survey grid. A very weak correspondence between GPR transects does occur along the east edge of the study block that roughly correlates with the northeastern anomaly seen in the resistivity data.