Near-surface geophysical techniques, including ground-penetrating radar, magnetometry,
electrical resistivity, and electromagnetic conductivity, have become primary tools in the
detection of unmarked human interments. The main advantages of these techniques are
that, unlike archaeological excavation, they are relatively rapid and do not involve grave
disturbance. Disadvantages are that most surveys do not offer foolproof detection of all or
even most graves, and the absolute identification of these anomalies as interments is
rarely positive and often requires additional invasive archeological fieldwork. Stripping,
excavation, or other invasive tests, however, are not acceptable to many Native American
tribes and other groups.
This project has explored techniques of down-hole magnetic susceptibility and soil
magnetism as a means of improving the detection of unmarked graves. These relatively
non-destructive techniques were tested at two historic Native American family cemeteries
located in Kansas and Nebraska and at an Anglo-American cemetery in Kentucky that
was being excavated in advance of development. Down-hole tests explored geophysical
anomalies and grave shafts at each of these cemeteries, comparing these to tests of
undisturbed ground in the search for distinctive magnetic characteristics of grave shafts
that could be used in the evaluation of geophysical anomalies. At select locations, soil
samples were collected when making the hole for the down-hole sensor and these
samples were analyzed in the laboratory using a number of magnetic techniques in order
to understand the origin of observed magnetic contrasts. Magnetic characteristics of the
burials themselves, which might be useful for grave identification in certain contexts,
were investigated only at the cemetery that was being excavated.
Results indicated distinctive magnetic characteristics of both shafts and interments related
to the burial process and transformation of the interment over time. Grave shafts, per unit
volume, tended to be less magnetic, apparently as a result of soils that are less-compact
than surrounding undisturbed ground. Compaction information provided by penetrometer
studies did not consistently identify grave shafts, although this failure is probably related
to the insufficient depth sampled by the pentrometer. Soil magnetic studies showed a
patterned magnetic enhancement of interments useful for burial identification during
excavation when grave goods and skeletal remains are lacking. The magnetic signatures
documented were not invariable, but by combining near-surface geophysical, down-hole
magnetic susceptibility, and soil magnetic techniques, there is a potential for improved
capabilities in the identification, evaluation, and thus the preservation of unmarked
human burials.