Archaeo-Physics LLC was contracted by GCM Services, Inc. to perform geophysical survey as part of archaeological investigations at the 30-30 Winchester Site (48CA3030), a prehistoric campsite in Campbell County, Wyoming. Magnetic field gradient survey was successful in detecting several anomalies that were thought to be caused by prehistoric hearths (later verified by excavation). In general, the site had very little magnetic "clutter" due to modern metal or geologic variance. The standard deviation of magnetic data after processing was 0.4nT. Anomalies thought to be caused by hearths have amplitudes up to several nanoTeslas and contrast starkly with the very uniform background.
A cluster of several roughly circular magnetic highs appear in the southeastern part of the survey area, which is adjacent to the bank of the nearby creek. These anomalies were though to be caused by hearths associated with the prehistoric occupation of the site. This was later confirmed by excavation.
The high-amplitude bipolar anomaly near the center of the magnetic map was excavated as well, but no apparent source was dicovered. Laboratory testing of soil samples and the geometry of the anomaly has shown it to be an example of lightning-induced remanent magnetization (Verrier et al.).