Abstract

Surveyor Deep-Sea Channel extends for approximately 700 km across the northern Alaskan Abyssal Plain. It originates near the base of the continental slope opposite Dry Bay and Alsek Strath, Alaska, and terminates in the Aleutian Trench south of Kodiak Island. East of Giacomini Seamount, the axial gradient of the channel is about 1.0 m per km, and its morphology is in agreement with that predicted by assuming a depositional equilibrium with channelized turbidity currents. West of Giacomini Seamount, the axial gradient increases to values as high as 7.5 m per km as the channel course turns toward the northwest and plunges into the trench. Over this part of its length, the measured relief and sectional area of the channel increase and are no longer in depositional equilibrium. The lower channel is found to be erosional in nature, this effect being a response to the downwarping of the northern rim of the Pacific plate into the Aleutian Trench, causing a steepening of the channel axial gradient with a corresponding increase in the velocity of turbidity current flows.

Piston cores recovered from areas near the channel typically consist of a sequence of fine sand and pelitic intervals. Cores obtained at greater distances from the channel consist of lower laminated silt units, again capped by pelitic intervals. There is a tendency for the coarse-grained units to thin and become less frequent with distance from the channel, while the pelitic units appear generally to thicken.

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 as much as 200 km south of its present position with respect to the North American plate and may have been linked with one of the fossil sea channels on the eastern Aleutian Abyssal Plain. The channel is not contiguous with a submarine canyon and throughout its history has not been linked with any consistent river-drainage system-its sediment source instead being the large system of piedmont glaciers in southeastern Alaska.

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