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ABSTRACT: Sedimentary Depositional Environments in the Gulf of Alaska from GLORIA Imagery

Paul R. Carlson, T. R. Bruns, A. J. Stevenson, D. M. Mann, Q. Huggett, U. K. Wormly, M. Dobson

GLORIA side-scan images provide new insight to the morphology and sedimentology of the Gulf of Alaska and show that tectonism strongly influences downslope and abyssal plain sediment transport.

Along the Fairweather-Queen Charlotte transform margin, south of Cross Sound, short, chute-like canyons cross the slope to submarine-fan channels. At least one canyon is offset by strike-slip motion along the fault. Fan channels coalesce to form two deep-sea turbidite channels (Mukluk and Horizon) that extend 1000 km southward to the Tufts Abyssal Plain.

From Cross Sound to Pamplona Spur, dendritic gulley systems and short chutes cross the slope into tributary channels that merge into major channels. Tributary channels from Cross Sound to Alsek Valley form the Chirikov channel system, which bends westward and ends in turbidite fans south of the Kodiak-Bowie Seamount chain. A probable ancestral Chirikov channel carried sediment westward to the Aleutian Trench. Channels from Alsek Valley to Pamplona Spur coalesce 280 km seaward of the slope to form the Surveyor Channel, which meanders across the abyssal plain 500 km to the Aleutian Trench.

Between Pamplona Spur and Middleton Island, dendritic slope canyons reach the eastern end of the Aleutian Trench; sediment moves southwestward along the trench. Southwest of Middleton Island, discontinuous trench-parallel subduction ridges change slope drainage from a dendritic to trellised pattern as sediment is forced to flow around the ridges to the Aleutian Trench. At least two small fans have been constructed on the trench floor. Southwest of Kodiak Island, subduction ridges create mid-slope basins that trap modern sediment.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990