In both gravity and magnetic exploration we combine geologic observations with the potential fields data. Those data are then typically subjected to filtering, edge detection, multiple inversion techniques for depth estimates, and finally 3D rendering.
We specialize in a combination of noninvasive total field magnetometry, ground penetrating radar (GPR), and electrical resistivity to yield 2D and 3D images of the shallow subsurface. Typically, processing, modeling and inversion of magnetic data for 3D subsurface sources focuses further efforts in GPR and resistivity modeling. Those results help guide the placement of test units and/or establish the layout and boundaries for historic to ancient sites. Often standard archaeological pedestrian surveys followed by total field magnetometry and GPR is the most economical and productive approach to explore for or confirm the presence or absence of subsurface features before construction or drilling projects.
Our experience includes establishing the layout of long gone historic townsites, learning the perimeter of overgrown cemeteries and burial grounds, confirming shallow graves, reconnaissance for mitigation during construction projects, and discovery of buried hearths and living surfaces while discovering previously unknown archaeological resources. We prefer to work closely and interactively with the relevant archaeologists on any particular project for optimal and cost effective results.
The image is a mix of raw and processed magnetic data with final GPR results collected in an area of tall grass, sagebrush, and scattered aspen trees. The fluvial features evident in the GPR removed some magnetic anomalies from consideration. Six subsequent test units (1x1 m) yielded three hearths at 0.6 to 1.0 meters dated from 1,720 to 3,090 years old, some boulder concentrations, and subtle traces of a 1930’s dirt road. As is typical in archaeological investigations following geophysical results, there were no ‘dry holes’.
A combination of radar and total field magnetics led to excavation of three fire hearths, the oldest at 3,090 B.P.
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