Recent marine sediments and submarine topography, Sverdrup Islands, Canadian Arctic Archipelago

Horn, David R.
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Submarine topographic features of the channels, sounds, fiords, and bays can best be explained as the products of extensive glacial excavation of a pre-existing drainage system. Troughs, hanging troughs, strings of deeps or basins, terminal sills, linear rises and depressions, and oversteepened deltas are considered direct or indirect evidence of glacial scour. Following glaciation, a negative movement of the Sverdrup Basin was accompanied by flooding of the northern part of the Archipelago. Only the upper portions of former interfluvial areas remained above sea level. These topographic highs are the present-day islands of the Canadian Arctic Archipelago. Statistical analyses of beach, fluvial, deltaic, and offshore marine sediments reveal characteristics that may be unique to polar deserts and ice-covered seas. Textures of beach and fluvial sediments are a function of associated relief and parent material. The deltaic environment is defined as that portion of the sea floor extending from the mouth of a river to approximately 3,200 feet from shore. Deltaic sediments show a progressive decrease in grain size seaward. Size distribution is related to the settling velocities of particles of different diameters. Offshore sediments have uniform textural properties. They are a combination of silt and clay (settled from suspension), and a minor but significant portion of sand- to granule-sized sediment (ice-rafted). An increase in mean grain size on the crests of submarine topographic highs suggests that winnowing by currents is taking place over these features. Two large areas of the sea floor lack a cover of Recent sediment. Organic carbon constitutes 0.84 to 2.14% of the offshore sediments. A dual source, terrigenous and phytoplanktonic, may explain the relatively high percentage of organic carbon. There is a positive correlation between percent organic carbon and amount of clay in the samples. Results of semiquantitative clay-mineral analyses of source rock, fluvial, deltaic, and offshore marine sediments indicate that montmorillonite, kaolinite, and illite are the dominant clay minerals. In this northern region, there is no change in clay mineralogy during weathering and transport. It is suggested that this may be characteristic of weathering under polar desert conditions. The mineralogy of parent materials on the islands controls the clay mineral distribution in offshore areas. In Louise Fiord, well-crystallized kaolinite is differentially flocculated close to shore. A study of the roundness of quartz grains of sand, silt, and clay size reveals that the distribution of this property is bimodal. Coarse and medium sands are well rounded, fine sands through coarse silts are angular, and fine silt and clay-sized particles are well rounded. High roundness of grains in the medium to coarse sand grades is attributed to abrasion. Well rounded quartz in the silt-clay size range is considered to be a product of solution.