North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: Angel Site, IN;
Reference: Johnston, R. B. (1961). Archaeological Application of the Proton Magnetometer in Indiana (U.S.A.). Archaeometry 4:71-72 (used with permission).
Since the summer of 1961 the Indiana Historical Society has stepped up its project, under the direction of Glenn A. Black, designed to evaluate the archaeological applications of the proton magnetometer in this part of the New World. The fieldwork to date has been concentrated on Angel Site in south-western Indiana in a region of sedimentary geology offering no probable sources of magnetic anomalies. The site is a large (not less than 100 acres) village of Late Prehistoric age (Middle Mississippi culturally) consisting for the most part of house patterns and habitation refuse with several large earth mounds including the typical truncate pyramidal type. The 3800 foot long southern edge of the village is bounded by the Ohio River while the east, north and west sides are enclosed, front bank to bank of tile river, by a bastioned palisade which at its maximum extends for slightly more than a mile in a protective arc around the settlement. It is the latter structure that provides seemingly ideal experimental conditions for magnetometer trials. The palisade was constructed by setting large poles vertically at intervals in a trench, intertwining smaller branches horizontally and covering the exterior and interior with a mixture of mud and straw. Today, of course, none of the superstructure remains but upon excavation the trench is clearly discernible and, in fact, has been uncovered and plotted at various sections for a total distance of about 1700 feet. Lacking excavation, however, it is still possible to trace the location of this defensive wall over most of its course around the village. In part, it is indicated by an elongate ridge having a height, in places, of as much as three feet although it is lower on the average. In areas where cultivation has obliterated any relief over the palisade line, as is the case over most of its length, soil differences and attendant characteristics exhibited in aerial photographs mark the position. Relatedly, a careful study of the botanic population upon and immediately adjacent to the old structure has revealed significant if usually subtle percentile differences which serve also, nonetheless, to record the path of the wall. Here, then, was an opportunity to search magnetically for a feature—under both cultivated and undisturbed overburden of various depth, in wooded and open areas, in the absence of obvious interference—the exact location of which could, over a large part of its extent, be demonstrated by several lines of evidence. Readings were taken in systematic north-south survey sections, 10 ft. wide by 100 ft. long, at fifty foot intervals across the old palisade line. The pattern of magnetic anomalies (lows) appears to coincide well with the palisade and shows at one point, as indicated also by the other evidences, that a single wall splits into two walls.
Also during the summer of 1961, a house structure was excavated in an area that had been surveyed at one foot intervals with the proton magnetometer. Houses are rectilinear, built over a pit about two feet deep with walls of the same type, but not so heavy, as described for the palisade. The magnetic lows occurred generally down the centre of the house pit while readings elsewhere in the pit area (i.e., on either side of the lows in each traverse) were as a whole significantly lower than those on the exterior of what proved on excavation to be the walls of the house. Three low clay-lined fireplaces in the centre of the house, beneath about two feet of fill before excavation did not register magnetically.