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.