Application of Near-Surface Geophysical
Techniques
for Geologic and Hydrologic Investigations in the Arctic
By
A.J. Delaney (U.S. Army Cold Regions Research and
Engineering Laboratory), P.R. Peapples (Alaska Division of Geological &
Geophysical
Surveys), and S.A. Arcone (U.S. Army Cold Regions Research and
Engineering Laboratory)
Application of
geophysical
techniques for shallow sub-surface (0.5 to 30 meters) investigations
in arctic Alaska is often challenging. The thin, saturated, active layer can
greatly limit signal penetration; coarse-grained alluvium can scatter
high-frequency pulses and perennially frozen sediments often demonstrate little
contrast in electrical properties or density. Despite these challenges there are
several situations, in the terrestrial Arctic, where ground penetrating radar (GPR)
and electrical resistivity (DC) methods can be used effectively. Here we show
results from several successful investigations that demonstrate the ability of
geophysical
tools to resolve and profile sediments layers, define taliks and
thaw zones, and characterize bedrock structure. On an Itkillik River point bar
deposit we used GPR to reveal sediment layering and depositional patterns. In a
late winter study on the Sagavanirktok River, also using GPR, we detected the
presence of thaw bulbs and frost taliks and confirmed our interpretation by
drilling. During the winter we operated GPR, from low- flying helicopters, to
locate sources of fresh water beneath continuous ice cover on rivers and streams
east of Prudhoe Bay. Additionally in sub-arctic Alaska we have successfully used
DC methods to identify bedrock fracture zones beneath sediment deposits. Our
results demonstrate effective application of GPR and DC methods as tools to aid
both geologic mapping and exploration.
AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.