GEOPHYSICAL INVESTIGATION OF A TIMBUCTO ARCHAEOLOGICAL SITE, NORTH ELBA, NEW YORK

Timbucto is a 19th century settlement of African-American farmers in North Elba in the Adirondacks, New York. A wealthy abolitionist provided land to free African-American New Yorkers to get them out of the cities and onto their own farms. The purpose of our geophysical investigation was to locate building foundations and dumping sites associated with one Timbucto farm.

Four geophysical methods were used to study the Timbucto site, electromagnetics, electrical resistivity, magnetics, and ground penetrating radar.

The magnetic survey of the site indicated the presence of a series of magnetic anomalies probably due to PreCambrian crystalline rocks lying beneath glacial deposits. The problem with the interpretation of the magnetic anomalies is distinguishing those anomalies due to basement from those of an archaeological origin. However, the magnetic map shows high magnetic measurements in the same area where the building foundation was suspected.

Two vertical electrical sounding surveys were conducted to a depth of 10 and 13 meters. The near surface material to a depth of about six meters had high resistivity (>1,000 ohmmeters). This high resistivity material is attributed to a silty sand of glacial origin. The resistivity decreases to less than 1,000 ohmmeters at a depth of six meters due to a ground water or a higher clay content in the sediments. A resistivity map of the area was constructed that shows the resistivity of the material to a depth of two meters. The resistivity map also shows a series of resistivity highs extending in the middle of the area that correlates with magnetic highs.

Three ground penetrating radar profiles were conducted across the area. Interpretation of the profiles indicates that possibly foundation walls occur between 1.0 and 1.5 meters depth. The origin of the profiles would also be geologic structures.