Contemporary Sedimentary Environments on Baffin Island, N.W.T., Canada: Glaciomarine Processes in Fiords of Eastern Cumberland Peninsula

Abstract

Maktak, Coronation, and North Pangnirtung fiords are major confluent trenches in the dissected plateau of eastern Baffin Island. Fresh water and sediment from large outlet glaciers of Penny Ice Cap, and from smaller ice fields nearby, enter and pass along the fiords largely as surface overflow. Mixing with salt water beneath is inhibited near the fiord heads by the strong density gradient at the pycnocline. Patterns of current and suspended sediment deposition on the fiord floors are determined in part by the influence of Coriolis force. Despite a small tidal range (1.1 m), the absence of sills within the fiords allows free exchange of sea water and frequent or quasi-continuous circulation at depth. Except near the head of the fiords in high-energy environments of rapid sedimentation, bioturbation by molluscs and echinoderms destroys many of the fine sedimentary structures. However, from studies of grab samples and short cores, four principal processes of sedimentation are proposed: (1) infrequent deposition of coarse particles from ice rafting and subaerial rock fall; (2) settling from suspension in overflowing fresh water of fine sand and flocculated silt and clay at rates that probably do not exceed several millimeters per year except near the fiord heads; (3) gravity flows, including slumping of oversteepened subaqueous slopes, turbidity currents which produce thin, graded beds of moderately sorted sands, and nonturbulent liquified or fluidized flow depositing ungraded layers of well-sorted coarse sand (the latter may be important at the toe of Coronation Glacier where fresh water entering at depth rises to the surface leaving its coarse load to spread over the fiord floor); and (4) aeolian transport from the sandur surfaces depositing distinctive bands of medium sand.