ABSTRACT: Gloria Mosaic of the Gulf of Alaska and the British Columbia Margin: Deep-Sea Channels, Margin Deformation, and the Queen Charlotte Fault

Terry R. Bruns, P. R. Carlson, A. J. Stevenson, M. A. Fisher, H. F. Ryan, D. M. Mann, Maxwell Dobson, Quentin Huggett, Lindsay Parson, N. G. T. Fannin

GLORIA images collected from 1986 to 1989 show sea-floor morphology from the shelf break seaward to 400 km in the Gulf of Alaska and a 70-km-wide swath along British Columbia.

Along the Aleutian convergent margin, sediment is dominantly trapped in mid-slope basins, where few canyons reach the trench. Accretionary wedge structures range from highly discontinuous to long and continuous.

The Yakutat transition margin is either extensively cut by dendritic drainages or, at sea-valley mouths, covered by glacially derived sediment. Young structures underlie the slope from Middleton Island to Pamplona Spur, but are absent from Pamplona Spur to Cross Sound.

Along the southeast Alaska transform margin, the Queen Charlotte fault is imaged as a narrow linear feature. The fault steps westward at Tuzo Wilson Knolls, which likely is a spreading ridge segment. Large anticlines lie seaward of and trend parallel to the fault.

On the abyssal plain off the Shumagin margin, inherited structural and bathymetric features trend parallel to magnetic anomalies, and trench parallel features reflect faulting as the ocean plate bends into the trench. To the north, three turbidite systems drain the margin. The Surveyor system begins between Pamplona Spur and Alsek Canyon and empties into the Aleutian Trench. The Chirikof system arises near Cross Sound and ends in turbidite fans south of the Kodiak-Bowie Seamount chain, a relic Chirikov channel that once carried sediment westward to the Aleutian Trench. The Mukluk and Horizon channels start along southeast Alaska and end 1000 km away on the Tufts abyssal plain.

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