Grain-size distribution and origins of unconsolidated fine sediments in ice-free areas, Soya Coast, East Dronning Maud Land, East Antarctica

Abstract

Unconsolidated fine sediments (UFS), sporadically deposited in Soya Coast ice-free areas, have often been described as glacial deposits (till) or subglacial till in previous studies, but their genesis and depositional environments have never been discussed so far. In this study, 95 samples of UFS were analyzed for grain-size distribution, and their properties and origins were examined by contrast with the grain-size distribution of primary subglacial-debris (PSD): debris in basal ice and lodgement tills. Primary subglacial-debris is composed of a very broad range of grain size from clay to sand, and exhibit a typically bimodal frequency distribution with peaks in sand and clay parts. In contrast, some of the UFS covered by gravel or raised beach deposits have the same grain-size distribution with PSD, although almost all UFS consist mainly of clay and/or silt and exhibit various frequency distributions. Therefore, it seems reasonable to conclude that the UFS contains abundant reworked materials from the PSD, which were widely deposited on the Soya Coast formerly ice-free areas.