Marine Geology of Benthic Biohabitats in Glacier Bay, Alaska

This research involves the characterization of seafloor habitats in lower Glacier Bay, including geomorphic, sedimentologic, and stratigraphic descriptions, based on acoustic imaging and profiling of the fjord floor. The goal has been to determine the bottom character of several field study sites to help explain distributions of Dungeness Crabs and Halibut. Studies of crab density have been conducted in the study area. O'Clair et al (1995) reported density of crabs at the study sites to range from 78 to 2012 crabs/ha over three sampling periods from April, 1992 through April 1993. Glacier Bay Field Station's halibut research efforts have been directed at such basic ecological questions as diet, home range, site fidelity, habitat selection, distribution patterns, and the relationships between halibut and other species.

The geological data presented here are used to map the wide variety of marine environments that are under study in this recently deglaciated bay complex. The environment types include:

1. moraines with varying sizes of boulders and cobbles;
2. moraines where the coarser larger cobbles and boulders appear to be covered with finer sediment (sands and in some places muds);
3. relatively featureless muddy-bottom bays;
4. a submarine sandy delta front off the Bartlett River, with well-defined bedforms encroaching on the basin floor mud of Bartlett Cove;
5. rocky insular slopes;
6. shallow basins with thin recent sediment cover;
7. deeper basins (>20m) with soft sediment cover of variable thicknesses; and
8. some sediment accumulations that apparently contain free gas, probably methane.

Text and illustrations from two publications by Carlson et al., 1998.

For additional information contact Guy R. Cochrane.