Combined magnetic and chemical surveys of Forts Kaskaskia and de Chartres Number I, Illinois

Abstract

Fort Kaskaskia and Fort de Chartres I were two in a series of forts built by the French along the Mississippi River in the first half of the 18th century. The sites of these forts are now Illinois State property, the first being a State Park. In order to assess the archaeological resources inside the known boundaries of Kaskaskia and to locate the boundaries of de Chartres I, first seen as a dark area on an aerial photo, both sites were subjected to combined magnetic and chemical surveys. The magnetic surveys were conducted in the difference mode (using two magnetometers) on a one meter grid unit. The chemical surveys were sampled at 10 m intervals along two transects at Kaskaskia and at 2 m intervals along two transects at de Chartres. The samples were tested for phosphate, pH, and several elements. At both sites there were positive correlations between some magnetic anomalies and phosphate, pH, and some elements. At Fort Kaskaskia the survey results indicate that the west side contains activity areas while the central parade ground has little or none. At Fort de Chartres I it is believed that the fort boundaries and a possible interior building area have been identified by the magnetic record and the chemical results.