Sediment characteristics in iceberg dominated fjords, Kangerlussuaq region, East Greenland

Abstract

Abstract Sediment cores from three East Greenland fjords contain sediment lithofacies and depositional processes in an iceberg dominated glacial marine setting. Three major lithofacies, diamicton, fine-grained mud, and sand, are deposited by two processes, sediment rain-out and sediment gravity flows. The sediments in Kangerlussuaq Fjord are predominately fine-grained muds deposited by rain-out from icebergs and glacier meltwater, with sediment gravity flows acting as secondary agents of deposition. Miki Fjord records rain-out of fine-grained muds from a river plume emanating from a proglacial delta at the fjord head. Alternating units of diamicton and fine-grained mud in Nansen Fjord are deposited by sediment rain-out from icebergs; particle size is governed by the oceanographic conditions in the fjord at the time of deposition. Despite their proximity to each other, each fjord is distinguished by a distinct sedimentological signature: Kangerlussuaq Fjord has low total organic carbon contact, Miki Fjord has high mass magnetic susceptibility, and Nansen Fjord has high amounts of ice-rafted debris. Comparison of the East Greenland iceberg dominated and Alaska glacial meltwater dominated environments indicates few major differences between sediments deposited in these two settings. This similarity raises doubt as to how well glacial marine sedimentary sequences can be used to interpret and reconstruct differences between glacial marine environments in the past without knowledge of sediment accumulation rates, environmental conditions at the time of sediment deposition, and comparable sedimentological data between studies.