Alec E. Aitken

The glacimarine sedimentary environment of Expedition Fiord, Canadian High Arctic

Abstract Expedition Fiord is a small, shallow inlet on the west coast of Axel Heiberg Island near 80°N latitude. It receives runoff and sediment at its head from a 1079 km 2 drainage basin, 72% of which is glacier-covered. Subbottom acoustic survey and cores from the fiord floor were used to assess the sedimentary environment. Most of the sediment is deposited within 3 km of the inflow from suspension in the overflowing cap and by gravity flows on the foreset beds of the delta. Occasionally, weak turbidity currents reach the mid fiord where they deposit fine-grained sediments. Icebergs from a large calving glacier in an adjacent fiord raft additional sediment, especially to the outer part of the fiord. They also scour the seafloor, although the persistent ice cover and slow currents in the fiord restrict this process. Except near the inflow, the total sediment accumulation since deglaciation is less than 20 m, and the rates of 0.5–1 mm/yr have not varied significantly to the present. A thicker deposit in the outer fiord is probably related to an early Holocene glacier margin near that location.

Holocene Nearshore Environments and Sea-Level History in Pangnirtung Fiord, Baffin Island, N.W.T., Canada

Coastal landforms in Pangnirtung Fiord have developed in response to fluctuating Holocene sea level. A series of raised marine shorelines developed on the shores of the fiord during an early Holoce...

Holocene glacimarine sedimentation and macrofossil palaeoecology in the Canadian High Arctic: environmental controls

Abstract Raised glacimarine sediments adjacent to Strand Bay, Axel Heiberg Island and on Fosheim Peninsula, Ellesmere Island, record sedimentation in environments proximal to tidewater glaciers and glacimarine deltas. The different styles of sedimentation during early Holocene deglaciation (ca. 8–10 ka BP) of these regions are of particular interest. In Strand Fiord, Axel Heiberg Island coarse-grained sediments deposited from high-density turbidity currents generated along the margin of tidewater glaciers, are overlain by laminated fine-grained sediments deposited by suspension settling in a shallow ice-proximal environment. The fining-upward sequence records the reduction in sediment supply as tidewater glaciers retreated onto land. In contrast, on Fosheim Peninsula, Ellesmere Island, laminated to massive fine-grained sediments were deposited from low-density turbidity currents and by suspension settling in a deep prodeltaic environment several kilometres from upland ice caps. Sediment texture coarsens-upward, reflecting increasing proximity to sediment sources as deltas prograded during early Holocene marine regression. Two macrofossil faunas, a Portlandia arctica assemblage and a Hiatella arctica-Mya truncata assemblage, occur in association with early Holocene sediments. Mid-Holocene sedimentation (ca. 4–8 ka BP) in both regions was characterized by the accumulation of laminated or massive fine-grained sediments deposited from low-density turbidity currents and by suspension settling in prodeltaic environments. Several macrofossil faunas are recorded in these sediments; a Portlandia arctica assemblage and an Astarte borealis-Mya truncata assemblage associated with laminated muds deposited in shallow water, and a deep-water Portlandia arctica assemblage associated with massive muds. Variations in sedimentation rates can be correlated with the summer-melt layer record of the Agassiz Ice Cap on Ellesmere Island. Early Holocene deglaciation coincided with a period of increased summer ablation (ca. 8.5–11.5 ka BP) that contributed to the massive influx of sediment into marine environments. The mid-Holocene ice core-record indicates a sharp decline in summer ablation (ca. 6.0–9.5 ka BP) resulting in the reduction of sediment flux to marine environments.