Abstract

Terrestrial and marine records provide the first reconstruction of past glacial events on west-central Axel Heiberg Island. Lateral moraines along Expedition Fiord define an early Holocene ice margin when a trunk glacier occupied the inner half of the fiord. Limited sediment accumulation in the outer fiord (< 10–40 m) questions whether this ice margin records the limit of the last glaciation. Ice retreat began > 8.4 ka BP, principally by calving of an unstable ice front to a position well upvalley of the present ice limit. Rapid deglaciation is evidenced by (i) an absence of ice marginal landforms and related marine biofacies; (ii) a scarcity of raised marine sediments; and (iii) exceptionally thin sediments (< 5–20 m) in the inner fiord. A transition from a Hiatella arcticaMya truncata macrofossil assemblage to an Astarte borealisMya truncata assemblage reflects a change from moderate to low energy depositional environments at the fiord head by 7.9 ka BP.The extensive ice advance into Expedition Fiord is contrasted by a more restricted advance in adjacent Strand Fiord, which contains both glacial and marine features that appear to predate the last glaciation. The difference in ice extent between the two fiords is explained by drainage basin morphometry and fiord bathymetry, and reflects modern analogues. Initial retreat of trunk glaciers may have occurred in response to rising sea level, with regionally synchronous ice retreat occurring at 8.4 ka BP when climatic factors were dominant. Glacier dynamics controlled the rate of ice retreat, with tidewater glaciers retreating much more rapidly than those with terrestrial margins.

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