T104 Combining Geology and Geophysics (Posters)

Monday, 10 October 2011
9:00 AM - 6:00 PM
Hall C

REFINING FLOODPLAIN STRATIGRAPHY AT THE PINE LAKE ENVIRONMENTAL CAMPUS ARCHAEOLOGICAL SITE USING GPR, EMI, AND GPS

Paper number: T104-4
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

The Pine Lake Environmental Campus (PLEC) of Hartwick College provides an excellent research locale to investigate floodplain stratigraphy. The Campus rests on a glacial moraine and Holocene floodplain next to Charlotte Creek in central upstate New York. Archaeological excavations on the floodplain have unearthed artifacts dating from the 20th Century to nearly 10,000 years BP. Further, archaeological test pits provide excellent ground truth for geophysical surveys. Previous ground penetrating radar (GPR) surveys of this floodplain revealed numerous channel and bar like features in the radar stratigraphy. Our work builds on that study, correcting problems with geolocation of profiles, increasing the data density, adding an electromagnetic induction (EMI) profile survey and characterizing surface topography with differential GPS.

For our surveys, we partitioned the floodplain into seven rectangular grids to take advantage of visualization software for three dimensional data. Each grid had 0.5 m spacing between each survey line. For each line we shot GPR at 1 cm spaced intervals, and followed the same path with EMI, collected at roughly 1 m spacing between shots. Grids varied widely in shape and size. For each day’s survey, static GPS receivers provided georeference control, and roving GPS attached to the GPR captured local topography.

We find that rectangular grids greatly simplified correlation between lines, and facilitated both processing and visualization of GPR and EMI data. GPR stratigraphy portrays buried bars, channels and sandy units. These features are clearly recognizable and easily traceable between profiles. EMI was particularly successful in identifying a buried historic dump, which is marked by anomalously high conductivity. We will compare EMI and GPR signals to better understand the physical response of GPR to regions of high conductivity, and test the utility of EMI for archaeological investigation in floodplain settings.