Harrison Bay, a gently sloping, shallow embayment on the continental shelf of northern Alaska near the Colville delta, is ice covered 9 months of the year. The 3 to 5-m Holocene marine sediment blanketing the shelf commonly is gouged into jagged relief forms by ice, and periodically winnowed or shaped into 1-m high sand waves by waves and currents. Yearly fathometer and sidescan sonar surveys, many diving observations, and numerous cores collected along a 14-km long test line show a complex sedimentation pattern, apparently typical for much of the shallow circum-Arctic shelves.

Ice-plowed sediments piled 20 to 80 cm above the shelf surface form a rough topography composed of soft cohesive mud. Locally the excavation products border gouges as continuous ridges; elsewhere they form isolated massive extrusion mounds with fissured crests. In some years a transient layer, as thick as 50 cm of flocculated silt and clay, blankets the surface, and only the crests of excavation products protrude. This transient layer remains trapped only in narrow gouges, where as much as 60 cm of mud may accumulate yearly. Original gouge floors commonly consist of smoothly striated compacted mud, as distinguished from the soft fill. The sea floor between recent gouges has subdued relief, is very firm, and is characterized by sediment-texture variations from clean sand to silty clay ver distances of 10 m or less; pebbles are rare. Cores typically contain clean cross-bedded sand interbedded with mottled mud in 10 to 20-cm thick lenses, as well as ice-disruption structures. Distinct layers in closely spaced cores cannot be correlated. The addition of gouge fill--sinuous, crisscrossing shoestring-like deposits of mud--appears to be the primary accretional process on shallow arctic shelves.

End_of_Article - Last_Page 978------------