Abstract

Sediments deposited in three fjord systems latitudinally spanning the northeast Gulf of Alaska coastline have distinctive rock magnetic characteristics that are derived from glacially eroded accreted terranes. Ideal conditions exist in coastal Alaska to preserve primary rock magnetic properties within the sediment record because of the dominance of glacial erosion and rapid sediment transportation and burial. In temperate glacially dominated marine settings, terrigenous sediment is not diluted by biogenic material and diagenetic alteration is minimal. The juxtaposition of temperate glaciers on the northwest-trending accreted terranes of the southern Alaska continental margin provides magnetic provenance tracers of sediment derived from this region that can aid in the interpretation of glacial, paleoclimate, and tectonic proxy records from marine sediment. Holocene sediment deposited in Glacier Bay is eroded from the Craig subterrane of the Alexander terrane; it is characterized by high-volume magnetic susceptibility and coarse-grained, pseudosingle-domain (PSD) and multidomain (MD) magnetite. In Yakutat and Disenchantment bays, farther to the north, glaciers also erode the Yakutat and Chugach terranes. There, sediment contains slightly finer-grained PSD and MD magnetite, which is chemically distinct from that of Glacier Bay. In the northern-most sector, sediment is eroded from the Chugach terrrane in Harriman and College fiords, adjacent to Prince William Sound. These sediments have low magnetic susceptibility and contain micron-size pyrrhotite.

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