Provenance Changes of Fine Quartz Sands in Glacial and Interglacial Intervals of the Feni and Gardar Drifts, North Atlantic: Fourier Shape Analysis

Abstract

Using a combination of Fourier shape analysis and scanning electron microscopy, very fine quartz sand grains from sediments of the Feni and Gardar drifts (Holes 610A and 611A) were analyzed to obtain provenance information. Three grain populations were defined: (1) smooth: grains covered with fine-grained silica plastering, interpreted as weathered from continental bedrock; (2) intermediate: angular, freshly fractured grains, probably transported by glaciers and icerafting; and (3) irregular: grains covered with irregular, platy silica overgrowths, likely the products of submarine erosion of fine-grained marine sediments. Examination of the proportions of each grain type in samples from intervals interpreted to be glacial (dark, calcareous muds) and interglacial (light-colored calcareous oozes) showed that there are changes in provenance across the boundaries between these intervals. Proportions of each grain type vary widely within glacial intervals, but remain relatively invariant in inter glacials. This suggests that factors affecting provenance, such as the amount of sea ice, water depth on the continental shelf, and strength and direction of bottom currents, are more variable during glacial periods. Presence of the irregular grain type indicates that erosion and redeposition of marine sediments is a major source of sediment in sediment drifts in the deep sea.

Provenance and Glacial History of Very Fine Quartz Sand from the Weddell Sea|Antarctica

“…Mazzullo and Anderson (1987) used both grain shape and surface texture to distinguish till from glacial marine sands in the Weddell and Ross Seas, but with only limited success. Fourier grain shape and surface texture analyses have also been used to define glacial-interglacial cycles (Dowdeswell et al, 1985;Eggers and Ehrlich, 1987).…”