Abstract This paper addresses the issue of the characteristic grain-size spectra of glacial and glacial marine sediments, an important topic because of the increasing emphasis on the use of specific sand-size fractions as indicators of iceberg rafting. Different methods of IRD identification can lead to different palaeoclimatic interpretations. We use three methods of grain-size analyses, with examples from the Labrador Sea, East Greenland, North Iceland, and the Ross Sea, Antarctica. The first method illustrates the ‘real’ grain size of glacial marine sediments by an examination of X-radiographs by image analysis and the sizing of clasts larger than 2 mm. Typically, grain-size analyses only apply to the matrix fraction of the sediment (smaller than 2 mm), and ignore the larger size clasts. The mean grain size appears to be between 8 to 10 mm. The second method includes counting the number of clasts larger than 2 mm from X-radiographs, and counts of particles (106–1000 μm). These latter counts show that diamictons from the North Iceland shelf indicate a dominance of glacially abraded basaltic grains, but they also contain a small, consistent proportion of angular volcanic glass shards of various compositions. The third method is to examine grain-size spectra of surface samples from East Greenland and the Ross Sea region of Antarctica and compare these data with down-core data from neoglacial-age glacial marine sediments from Nansen Fjord, East Greenland, and with late glacial diamictons from the North Iceland shelf. These sediments have a mode in the silt fraction, but they frequently have secondary peaks in the coarse sand and fine sand/coarse silt areas, and a trough in the range of 100 to 500 μm (medium to coarse sand). Most of the sediment samples analysed in this study contain 20–50% in the below 1 μm grain size, which reinforces the importance of examining this fraction in provenance studies in glacial marine sediments.

The records of glaciation and climate change preserved in sediments on the Canadian and northwest Greenland margins of Baffin Bay pertaining to the last interglacial-glacial transition are remarkably similar. In both regions, warmer than present terrestrial and nearshore marine facies of the last interglacial sensu stricto (s.s.) are overlain by glacial sediments that represent the most extensive advance of continental ice during the last glaciation. Chronometric controls ( 14 C, thermoluminescence, amino acids) indicate an isotope stage 5 age for this advance. Evidence for extensive high-latitude glacial erosion during stage 5 is recorded by abundant pre-Quaternary palynomorphs in Baffin Bay sediment cores, in contrast to a much reduced flux during the remainder of the last glaciation. Warm nearshore marine conditions (seasonally ice free) also occurred near the end of stage 5 along both the eastern Baffin Island and northwest Greenland coasts after the maximum glacial advance; surface water in central Baffin Bay apparently was dominated by meltwater at this time. Subsequently (isotope stages 4, 3, and 2), terrestrial conditions were colder and drier, sea-surface temperatures were lower, and ice margins were retracted. Minimum summer insolation at high latitudes, coupled with mild winters and vigorous meridional oceanic (and presumably atmospheric) circulation characterized the inception phase of the last glaciation during isotope stage 5. In contrast, the 20 ka B.P. (isotope stage 2) “last glacial maximum” was characterized by a zonal circulation regime that resulted in cold and dry conditions over Baffin Bay; the margins of the northwest Greenland and northeast Laurentide ice sheets did not extend beyond the fiords at this time.

Abstract The objective of this chapter is to provide information on the magnitude of elevation changes and rates of deformation that are associated with the recovery of North America, Greenland, and Iceland from the late Quaternary ice loads (Fig. 1). These topics are addressed in detail in various chapters of The Quaternary Geology of Canada and Greenland (Fulton, ed., 1989). In particular, the various regional treatments contain much of the basic information on which this present chapter is based. Andrews and Peltier (1989) also provide a survey of both the observational data and glacial isostatic theory. Of the major glaciated areas of North America, only Alaska has a paucity of studies on relative sea-level movements during the last deglacial cycle from the region directly influenced by an ice load (see Mann, 1986). However, Clark (1977) has evaluated the effect of recent changes in glacier thickness on the sea-level history of southeast Alaska. Neotectonics associated with glacial unloading of the Earth's surface are a different set of processes than movements associated with normal faulting or with the movements of plate margins, although there may be connections between them (e.g., Clark, 1982; Quinlan, 1984; Adams, 1989a, b). Glacial isostatic recovery affects large areas (ca. 14 × 10 6 km 2 of North America) and is characterized most commonly by spatial and temporal coherence of the response (e.g., Peltier, 1976; Clark, 1980; Quinlan, 1985; Quinland and Beaumont, 1982). Glacial isostatic observations have been used on this predictive basis for several decades to constrain appropriate models of