1. Imaging Furniture, Graves, and Stone Rings at Depth: Recent Magnetic and Radar Results from the Northern Rockies Steve Sheriff Professor of Geophysics, University of Montana Collaborators include: Doug MacDonald, Department of Anthropology, University of Montana Elaine Hale, Yellowstone National Park Robert & Virginia O’Boyle, Integrity Resources Archaeology, Potomac, MT Garry Carlson, Gradient Geophysics, Missoula, MT

2. Total Field Magnetics measure Earth’s magnetic field at 1:500,000 process data interpret the maps best cost-benefit tool follow up with radar Subtle changes in subsurface magnetic properties create subtle changes in Earth’s magnetic field

3. Yellowstone Lake – Total Magnetic Intensity ¼ hectare broad signature is geologic; best to remove it Buried cable? Interesting zone

4. Map Algebra: TMI – Regional = Residual Total Magnetic Intensity (TMI) Regional (relatively deep sources) NE corner looks even more interesting clip out the northeast corner for further analysis Residual (for analysis)

5. Strong, classic dipolar, central anomaly Radial distribution of surrounding highs Each anomaly has a source: geological, archaeological, or historic Northeast Corner with regional removed

6. Central anomaly = furniture rock, base ~ 1 meter Radial distribution of surrounding anomalies & sources suggest long term camping around that piece of furniture 3D model and excavation results

7. Ground Penetrating Radar – echoes off reflectors Transmit & receive radar waves (200–1000 MHz) Waves reflect off subsurface layers & objects Make profiles and maps of the reflectors

8. In search of a Historic Grave - Yellowstone Ground Penetrating Radar

9. In search of a Historic Grave - Yellowstone GPR – across current pavement 61 transects 0.5 meter line spacing 250 MHz antenna.05 meter trace spacing

10. 5 transects and one time slice Dashed line shows disrupted reflectors marking trench Next: interpolate horizontal slices In search of a Historic Grave - Yellowstone Ground Penetrating Radar

11. In search of a Historic Grave – Time Slices (map view) Horizontal slice of radar volume at 0.6 meters depth Lower edge of image follows current road edge Magenta lines mark probable edge of an older road flanked by trenches

12. In search of a Historic Grave – map view of radar 1.5 meters deep white box shows the most likely location of the historic grave

13. Stone Rings: Kevin Rim, MT & Kelly Forks, ID Processed magnetic data Robert O’Boyle photo and data

14. How deep could we bury the stone ring and still detect it? Current anomaly Mapped stones – a real mix of magnetizations Recalculate to 1 meter deep – easily detectable ‘BURIED’ 1 m

15. Easternmost grid Buried stone rings at depth - Clearwater River, Idaho

16. High energy fluvial deposits 1930’s CCC camp Recent construction

17. Left 1/3 is impacted by recent construction nice camp area at least 2 stages of road construction central anomalies are probable 1930’s CCC camp Buried stone rings at depth - Clearwater River, Idaho

18. Zooming in: expect archaeological anomalies of 1’s – 10’s of nT Extremely high amplitude anomalies from bits of metal, tent stakes, survey pins, etc. Pre-filtering, nothing is very apparent

19. Processed TMI: we expect anomalies of 1’s – 10’s of nanoteslas Circular features

20. Compare a radar time slice ~ 1 meter deep Roughly the same area GPR confirms the character of the magnetic anomalies

21. GPR Time Slices Probable stone circles at about 1 meter deep Probable 1930’s road to CCC camp

22. Combined Magnetics and GPR Yellowstone National Park

23. Raw and Residual Magnetics Raw data Regional removed

24. Overlapping Ground Penetrating Radar Despite rough ground conditions (fallen logs, bunchgrass, and sagebrush) we acquired GPR data over part of the magnetic grid. GPR data collected over 10 meters of the magnetic grid. 500 MHz antenna 0.5 meter profile spacing trace separation of 0.05 meters

25. Fluvial silts and sands below 0.90 meters, confirmed by auguring Time slice at ~1 meter Arcuate features result from horizontal sections through the fluvial structures. 3D: GPR Features from Fluvial Structures

26. Results from Test Units #1 - hearth (1,720 +/-40 B.P.) & evidence of obsidian tool manufacturing #2, 3, and 4 yielded only boulders. Each individual anomaly has the character of a boulder yet their concentration and alignment was promising #5 - hearth at about 0.8 meters (2,920 +/- 40 B.P.) #6 - likely hearth dated at 3,090 +/- 40 B.P.)

27. Total Field Magnetics Ground Penetrating Radar Noninvasive methods, substantial results