Sedimentology of an arctic basin: Itirbilung Fiord, Baffin Island, Northwest Territories
Authors: Syvitski J P M , Hein F J 
Published: June 2014

ltirbilung Fiord was investigated using geophysical, oceanographic and sediment surveys in 1982, 1983, 1985, and 1987. ltirbilung typifies a deep arctic basin that experiences episodic sedimentation events, cycled principally by nival and glacier melt with
punctuations by mass-sediment failures. Aeolian transport of sediment into the fiord basin may also be large, possibly four times the sediment volume transported by the ltirbilung River. A Quaternaryfill of greater than 150 mis located in two of the four basins. Paleohydraulic calculations suggest
that for the period 8400 to 6000 years BP, ltirbilungfiord received up to five times the present rate of fluvial delivery, reflecting the ablation of the Late Foxe Ice Sheet. Between 6000 and 150 years BP, a time of Neoglacial ice storage, sediment yield was much lower. Fiord circulation is related
to meltwater (from bath rivers and melting sea ice) during the summer, wind-generated drift during the late summer and fall, deep water exchanges during the Jal/, isohaline-generated circulation of winter, and tidal currents which operate over the entire year. Up-fiord winds initiate downwelling at
thefiordhead and an internai seiche the period of which is equal to the diurnal tide. Dawn-fiord winds caused the dissipation of these internal tides. ltirbilung River delta, one of the largest sandurs on Baffin Island, is largely conditioned by Little Ice Age events. A catastrophic jt/)kolhlaup
about 100 years aga removed much of the raised marine deposits that once covered the sandur, armoured the sandur surface with gravel waves and large boulders, and initiated a massive failure of the delta front. Little Ice Age deposits are very thin over most of the fiord, however, and are of
significance on/y near the head of the fiord. Sixty per cent of the fluvial load is moved offshore by sediment gravity flows that travel along numerous submarine channels. The se channels decrease in number and size down-fiord. Nine medium-strength gravity flow events (&amp;lt;0.36 m s -I ),
lasting between 1 and 5 hours, were measured in one submarine channel. Two types of flows were observed: ( 1) powerful single events which may represent coarse-grained delta front failure, and (2) weaker multi-event flows which may result from retrogressive failure of the prodelta muds. The rate of
sediment accumulation decreases down the fiord, punctuated by side-entry fan deltas that further contribute large volumes of sediment. Basin deposits are largely ponded between the fiord walls, although two of the sills are mantled by hemipelagic deposits. Five seismo-stratigraphic units are
identified and may represent a single phase of ice sheet advance and retreat, i.e. the Late Foxe glaciation. The upper three seismic units contain seven sedimentary facies that show little correlation between 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 turbidity currents and/or me/tout of aeolian sand covering sea ice caver; laminated sand and mud, from the hypopycnal discharge of river plumes; coarse sand/gravel, and pebbly sand and sand, reflecting
very rapid deposition from high concentration, viscous sediment-gravity flows, either as turbidity currents or as sandy debris flows; and the extremely rare crossbedded sands, that may relate to the reworking of turbidity current deposited sands by reverse flow mechanisms.