Abstract: Rates of Ice Gouging and Sediment Reworking, Beaufort Sea, Alaska

Peter Barnes, Erk Reimnitz, John Melchior, Lawrence Toimil

Repetitive side-scan sonar and precision bathymetric surveys over a 4-year period, in the Beaufort Sea at 6 to 12-m depth, have demonstrated changes in microrelief due to ice gouging. Surveys were made in 1973, 1975, and 1976. Gouges postdating the 1973 and 1975 surveys could be distinguished by the superposition of gouges and by the crispness of the gouge flanks. From the cross-sectional relief of a gouge as measured on fathograms, it is conservatively estimated that 0.65 km of a 10-km segment of trackline was gouged between 1973 and 1975 (33 m/km/yr). Preliminary measurements on the 1976 records indicate a similar rate of ice gouging (45 m/km/yr). Assuming that no area is gouged more than once, the bottom in the entire area of the survey would be reworked by ice in 20 t 30 years. The estimated gouging rates are conservative because they include neither the very small gouges nor the gouge flanks, and because the actual area of the bottom disturbed by a blunt ice keel is probably much greater than the measured width of the gouge. With an average gouge incision of 3 m and inner-shelf sedimentation rates of less than 1 m/1,000 years, surficial sediments will be reworked several times before being buried deep enough to escape the action of ice. Seaward of the study area in the stamukha zone, where ice activity is most intense, rates and intensities of ice gouging are expected to be greater. This study has important implications for the study of ancient high-latitude geologic environments as well as for the planning and design of offshore installations.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC