GEOPHYSICAL ANALYSIS OF LACUSTRINE ENVIRONMENTS FOR DETERMINING ARCTIC WARMTH

Geophysical imaging of lake sediments is a well-established approach used to: (1) investigate lake-level changes, (2) map sediment distribution and catchment erosion rates, and (3) evaluate stratigraphic integrity and aid in selecting core sites for paleoclimate studies. Geophysical imaging aids in site selection by allowing investigators to map the presence of "target" stratigraphic units and to evaluate stratigraphic continuity. We present an example of utilizing geophysical techniques to "prospect" for long sediment records.

The focus of the research is Lake CF8--a small lake in the Canadian Arctic (Baffin Island) overrun by a non-erosive of the Laurentide Ice Sheet--that contains intact lake sediments from at least three complete interglacial periods. Ground penetrating radar (GPR) was utilized in 2005 and 2007 while CF8 was still covered in ice, making collection of data advantageous. Imaging with the GPR was predominantly obtained using 100 MHz GPR antennas integrated with a real-time differential GPS unit. The depth of investigation was nominally 6 meters with good resolution of the subsurface, allowing interpretation of the geometry of alternating layers of low reflectivity gyttja units and high reflectivity sand units. Profile spacing was variable but collected in a grid pattern. Profiles are fenced, creating a pseudo-3D image, and the time-variant morphology of CF8 is determined. The addition of geophysics illuminates the geometric changes in the gyttja and sand units as the profiles extend away from the shoreline of the lake.