Sedimentary environments and facies in an arctic basin, Itirbilung Fiord, Baffin Island, Canada

Abstract

Itirbilung Fiord typifies a deep arctic basin that experiences episodic sedimentation events, cycled principally by aeolian transport, nival and glacier melt, with punctuations by mass-sediment failures. A Quaternary sedimentary fill exceeding 150 m is found in two of the fjord's four sub-basins. Basin circulation is associated with meltwater influx during the summer, wind-generated drift during the fall accompanied by deep-water exchanges, winter isohaline-generated circulation, and tidal currents which operate over the entire year. Sediment accumulation decreases down the basin; this general trend is interrupted by side-entry fan deltas that locally contribute large volumes of sediment. Basin deposits are largely ponded between the fjord walls, although two of the fjord's sills are mantled by hemipelagic deposits. Five seismo-stratigraphic units are identified and may represent sedimentary deposits associated with a single phase of ice sheet advance and retreat. The upper three seismic units were cored and contain seven sedimentary facies that show little correlation between sub-basins: pebbly-sandy-mud, from the melt of debris-laden ice; burrowed /mottled mud, reflecting the bioturbation of hemipelagic deposits; wispy laminated /mottled mud, from low-velocity currents and/or melt-out of seasonal sea ice cover, and bioturbation; laminated sand and mud, from the hypopycnal flows from rivers; graded-coarse sand/gravel, and pebbly sand and sand, reflecting very rapid deposition from high-concentration turbidity currents or from sandy debris flows; and cross-bedded sands, that may relate to the reworking of turbidity current deposited sands, possibly by reverse flow mechanisms.