Abstract

The Aleutian Trench contains vast volumes of clastic sediment sourced mainly from the glacial erosion of Alaska and controlled by allocyclic influences. GLORIA (Geologic Long Range Inclined Asdic) and multi-channel seismic surveys conducted by the US Geological Survey revealed details of both the geometry and distribution of the trench sediments and their associated supply systems. Milankovitch-induced climatic cycles cause the episodic release of sediment transported as both unconfined and confined turbid flows, the latter routed along submarine channels that cross the abyssal plain of the Gulf of Alaska and discharge into the trench. Small volumes of sediment enter the trench directly from glacier snouts at the transform trough-end of the trench and from the Chugach Mountains in the north. A major channel system extends along the trench axis, which acts as a conduit for turbid sediment flows. The channel also reworks and redistributes material supplied from the accretionary prism and the oceanic plate. Subduction of seamount chains coupled with the westward-increasing obliquity of plate collision and accretionary prism-sourced slump, which may be seismically triggered, segment the trench environment, dividing the axial channel system into discrete flow patterns. This effect of compartmentalization creates petrographically distinct segments of fill partly owing to the primary source landscape of accreted terranes formed of ancient island arcs. This serves to emphasize the cyclic nature of Earth processes.

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