Analysis Of Naturally Occurring False Alarms At A Uxo Test Site On Jefferson Proving Ground

The detection and discrimination of UXO can be limited by small scale geologic anomalies that exhibit similar responses, both in spatial extent and amplitude, to real ordnance. These anomalies are referred to as naturally occurring false alarms (NOFA). During the Jefferson Proving Ground 4 (JPG4) demonstrations in 1996, a number of NOFA were identified in total field magnetic data with one being quite large. To explain the causes of these NOFA, in-situ magnetic susceptibility measurements were made over the anomalies as well as the collection of soil samples up to a meter deep. The soil samples have been analyzed for mineralogy and the magnetic susceptibility, as well as frequency dependence of susceptibility, have been measured in the laboratory. A number of the NOFA also exhibited reversed polarity which would mean that they probably quite shallow anomalies. A number of these NOFA have been modeled to determine their remnance. The results of all of these analyses lead to the conclusion that the large magnetic anomaly is due to mineral transport and deposition along two converging ephemeral streams.