Animal-sediment relationships on a subarctic intertidal flat, Pangnirtung Fiord, Baffin Island, Canada

Broad, boulder-strewn intertidal flats border the shores of Pangnirtung Fiord, Baffin Island. These intertidal flats support a benthic biota dominated by bivalves, sedentary polychaetes and phaeophycean algae. The assemblage of organisms inhabits a variety of substrates ranging from muddy sand through gravelly sand and boulders. Six depositional environments defined on the basis of sediment texture, primary sedimentary structures and their associated macrofauna and ichnofauna are recognized on Pangnirtung Fiord intertidal flats. Proceeding seaward, these are beaches, sand bars, muddy sand flats, Macoma balthica sand flats, Arenicola marina sand flats, and boulder barricades. Such sediments, in outcrop, may differ only subtly from their equivalents in other latitudes. Modern biogenic structures provide essential information for environmental reconstruction in Arctic marginal marine environments. Their use in sedimentology is enhanced by the low preservation potential of primary sedimentary structures and shell material as a result of disturbance by drift ice, bioturbation, and dissolution. The ichnofauna exhibiting the greatest preservation potential is characterized by vertical domichnia of bivalves and polychaetes and resembles the ichnofauna recorded on the Bay of Fundy intertidal flats.