AbstractsEarth & Environmental Science

Surveyor Deep-Sea Channel extends for approximately 700 km over the northern Alaskan Abyssal Plain. It originates near the base of the continental slope opposite Dry Bay and Alsek Strath and terminates in the Aleutian Trench south of Kodiak Island. East of Giacomini Seamount, the axial gradient of the channel is in the order of 10 m/km and its morphology is in agreement with prediction, assuming a depositional equilibrium with channelized turbidity currents. West of Giacomini Seamount, the axial gradient increases to values as high as 7.5 m/km, as the channel course turns toward the northwest and plunges into the trench. Over this part of its length the measured center channel relief and cross-sectional area of the channel increase, contradicting prediction. The lower channel is found to be erosional in nature, this effect being a response to downwarping of the northern rim of the Pacific Plate into the Aleutian Trench. The channel originated in early to middle Pliocene time coeval with the initiation of pronounced tectonism and intense glaciation in southeastern Alaska. At this time, the channel was located perhaps 200 km south of its present position with relation to the North American Plate, and may have been linked with one of the fossil sea-channels on the eastern Aleutian Abyssal Plain. Throughout its history, the channel has not been linked with any consistent river drainage system, its sediment source instead being the large system of piedmont glaciers in southeastern Alaska. The distribution of coarse sedimentary material over the northern Gulf of Alaska strongly suggests that turbidity current activity has not been confined to only those regions close to Surveyor Deep-Sea Channel.