Abstract
Tidal flats are widely distributed on high-latitude coasts, where sea ice processes have been invoked to explain the abundance and distribution of boulders. This study documents the surface morphology and sediment dynamics of a Low-Arctic macrotidal system, the boulder-rich tidal flats of Koojesse Inlet, fronting the Nunavut capital, Iqaluit, on Baffin Island. This is a region of postglacial isostatic uplift and forced regression, with raised littoral, deltaic, and glaciomarine deposits. The spring-tidal range is 11.1 m and sea ice cover lasts roughly 9 months of the year. The extensive intertidal flats are up to 1 km wide, with a veneer of sand and gravel (including large boulders) resting on an erosional unconformity truncating the underlying glaciomarine mud, forming a terrace within the present tidal range. Over a 3-year study, no consistent pattern of erosion or deposition was evident. Over a longer time scale, the concave hypsometry, low sediment supply, slight ebb dominance of weak tidal currents, abrasion by wave-entrained sand, ebb-oriented ripples formed under subaerial drainage, and slumps on the terrace flanks are consistent with seaward hydraulic and gravitational sediment transport. These processes may be of greater importance than shoreward ice transport. This study underlines the importance of relict glaciomarine deposits, postglacial uplift, and falling relative sea level in the erosional development of these high-latitude tidal flats. Relative sea-level projections for Iqaluit are ambiguous, but a switch to rising sea level, if it occurs, combined with more open water and wave energy, could alter the foreshore dynamics of the system.
Highlights
Tidal flats are low-slope, low-relief, unlithified coastal landforms alternately covered and exposed by the flood and ebb of tides (Bird and Schwartz 1985; Amos 1995; Dyer 1998)
This paper presents a detailed study of the cold-climate macrotidal flats within Koojesse Inlet, aimed at (1) high-resolution morphometric and surficial sedimentary characterization of the entire platform from the backshore to the subtidal, (2) understanding the role of processes other than sea ice in the morphodynamics of this high-latitude shore-zone system; and (3) elucidating the factors that enabled development of the modern, wide, boulder-strewn intertidal flats, and their future stability under uncertain climate and sea-level projections
The coastal features of Koojesse Inlet can be classified into five types: bedrock outcrop, beaches, boulder-strewn tidal flats, sparsely vegetated marsh, and anthropogenic features (Fig. 2)
Summary
Tidal flats are low-slope, low-relief, unlithified coastal landforms alternately covered and exposed by the flood and ebb of tides (Bird and Schwartz 1985; Amos 1995; Dyer 1998). They are generally best developed and most extensive in meso- to macro-tidal settings, though many examples can be found in areas of more restricted tide (Klein 1985; Martini 1991). High-latitude tidal flats typically exhibit textural and morphological indicators of sediment transport by ice, including higher proportions of coarse sediment up to cobble and large boulder size (Dionne 1988). Varying combinations of vertical crustal motion, tidal range, slope, substrate, and exposure can lead to different landform configurations
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