Dynamic response to strike-slip tectonic control on the deposition and evolution of the Baranof Fan, Gulf of Alaska

Abstract

The Baranof Fan is one of three large deep-sea fans in the Gulf of Alaska, and is a key component in understanding largescale erosion and sedimentation patterns for southeast Alaska and western Canada. We integrate new and existing seismic refl ection profi les to provide new constraints on the Baranof Fan area, geometry, volume, and channel development. We estimate the fan's area and total sediment volume to be ~323,000 km2 and ~301,000 km3, respectively, making it among the largest deep-sea fans in the world. We show that the Baranof Fan consists of channel-levee deposits from at least three distinct aggradational channel systems: the currently active Horizon and Mukluk channels, and the waning system we call the Baranof channel. The oldest sedimentary deposits are in the northern fan, and the youngest deposits at the fan's southern extent; in addition, the channels seem to avulse southward consistently through time. We suggest that Baranof Fan sediment is sourced from the Coast Mountains in southeastern Alaska, transported offshore most recently via fjord to glacial sea valley conduits. Because of the translation of the Pacifi c plate northwest past sediment sources on the North American plate along the Queen Charlotte strike-slip fault, we suggest that new channel formation, channel beheadings, and southward-migrating channel avulsions have been infl uenced by regional tectonics. Using a simplifi ed tectonic reconstruction assuming a constant Pacifi c plate motion of 4.4 cm/yr, we estimate that Baranof Fan deposition initiated ca. 7 Ma. © 2014 Geological Society of America.