Remote Sensing Survey Preliminary Report Dillard Archaeological Site, Crow Canyon, CO
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Remote Sensing Survey Preliminary Report Dillard Archaeological Site, Crow Canyon, CO Figure 1 Dillard archaeological site and geophysical survey interpretations, June 2012. Submitted by: Meg Watters, PhD Co-PI, Remote Sensing & Visualization Coordinator Oregon Public Broadcasting Table of Contents Overview .......................................................................................................................................................5 Introduction ..................................................................................................................................................7 Site Control Survey........................................................................................................................................7 Geophysical Methods, Principles, and Equipment .......................................................................................9 Magentometry ..............................................................................................................................................9 Conductivity / Magnetic Susceptibility .......................................................................................................11 Resistance ...................................................................................................................................................13 Geophysical Data Interpretations...............................................................................................................16 Magentometry ............................................................................................................................................18 Resistance ...................................................................................................................................................28 Conductivity / Magnetic Susceptibility .......................................................................................................33 Conductivity ........................................................................................................................................33 Magnetic Susceptibility.......................................................................................................................38 Discussion of geophysical survey results ....................................................................................................43 Airborne LiDAR Principles and Results........................................................................................................51 Conclusions and Recommendations...........................................................................................................52 Acknowledgements and Credits .................................................................................................................53 Time Team America ....................................................................................................................................53 References ..................................................................................................................................................54 Table of Figures Figure 1 Dillard archaeological site and geophysical survey interpretations, June 2012.............................1 Figure 2 New site features identified through geophysical surveys.............................................................6 Figure 3 Geophysical survey areas covered during Time Team America project. .......................................8 Figure 4 The magnetic anomaly produced by a kiln is aligned to the dip and direction of the Earth’s magnetic field (From Clark 1996)..................................................................................................................9 Figure 5 Duncan McKinnon with the Bartington 601 dual array fluxgate gradiometer. ............................11 Figure 6 Electromagnetic induction diagram.............................................................................................11 Figure 7 Bryan Haley with the EM38 conductivity meter...........................................................................13 Figure 8 The flow of current from a single current source and resulting potential distribution...............14 Figure 9 A general four electrode array......................................................................................................14 Figure 10 The Twin-electrode array commonly used in archaeology........................................................15 Figure 11 Duncan McKinnon with the RM 15 resistivity meter and electrode array. ...............................16 Figure 12 Geophysical survey areas at Dillard site. ....................................................................................17 Figure 13 Magnetic gradient survey results...............................................................................................19 Figure 14 Magnetic anomalies caused by iron stakes and/or nails are seen as mono-poles (A) or di-poles (B) with an orientation to magnetic north..................................................................................................20 Figure 15 Magnetic survey results with site surface features. ..................................................................22 Figure 16 Interpreted magnetic survey results (the red arc identifies part of the Great Kiva berm)........23 Figure 17 Interpreted magnetic survey results with site surface features................................................24 Figure 18 Auger positions for ground-truthing geophysical survey anomalies.........................................26 Figure 19 New site features mapped through geophysical surveys and ground truthed. Pit house and pit house like features are purple polygons and blue points identify pits associated with a potential fence.27 Figure 20 Resistance survey, Dillard. .........................................................................................................29 Figure 21 Interpreted resistance survey. ...................................................................................................30 Figure 22 Interpreted resistance survey with overlain site features.........................................................31 Figure 23 Interpreted resistance survey with overlain ground-truthed archaeological features identified during geophysical surveys.........................................................................................................................32 Figure 24 Conductivity survey results........................................................................................................34 Figure 25 Interpreted conductivity survey results.....................................................................................35 Figure 26 Interpreted conductivity survey results with site features........................................................36 Figure 27 Interpreted conductivity survey with ground-truthed archaeological features........................37 Figure 28 Magnetic susceptibility survey results........................................................................................39 Figure 29 Interpreted magnetic susceptibility survey results....................................................................40 Figure 30 Interpreted magnetic susceptibility survey results with site features. .....................................41 Figure 31 Interpreted magnetic susceptibility survey results with overlain ground-truthed archaeological features.......................................................................................................................................................42 Figure 32 Comparison of magnetic gradient (A & C) and resistance (B &D) big pit house (red) and possible ritual pit house (yellow) anomalies. .............................................................................................43 Figure 33 Contrasting soils (red and dark brown) can be seen that define the edge of the big pit house feature. (Image courtesy of Crow Canyon Archaeological Center.) ..........................................................44 Figure 34 The floor of a section of the possible ritual pit house feature with a sipapu, ritual fire circle, and ash pit. (Image courtesy of Crow Canyon Archaeological Center.)....................................................45 Figure 35 Interpretations of all the geophysical survey methods at Dillard..............................................46 Figure 36 Core samples over geophysical anomalies help identify cultural (red points) and non-cultural (yellow points) site features. ......................................................................................................................47 Figure 37 Ground-truthed archaeological features (purple are pit houses or pit house like structures and navy blue are individual pits) overlain on site interpretations and surface features.................................48 Figure 38 Mapped site features overlain on interpretations of geophysical surveys. ..............................49 Figure 39 Pit house anomaly comparison. The pit house features as ground-truthed are positioned in the center of each sample above. ..............................................................................................................51 Figure 40 LiDAR DTM and the broader landscape with BM III site distribution in reference to the Dillard site (red)......................................................................................................................................................52