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tional environment is inferred and where the sand constitutes a thin surfi cial veneer. In
Europe, cover-sand is extensive over large areas of the western and central European
lowlands (Catt, 1977; Maarleveld, 1960; Nowaczyk, 1976). It is typically between 0.5 m
and 5.0 m in thickness.
Cover-sand is related to a nearby sediment source. It shows a degree of alternating
bedding involving layers of silty sand and sand that is interpreted as the result of deposi-
tion on an alternating wet and dry surface. The loam is reworked loess. Cryoturbation
structures and occasional faunal remains in cover-sand further indicate a cold climate.
Thus, cover-sand is regarded as being largely niveo-eolian in origin, having been modifi ed
by sheetwash processes (Koster, 1988; Schokker and Koster, 2004). A variant of cover-
sand occurring in northwestern France is the silty sandy layers termed “limons-a-
doublets” (Lautridou and Giresse, 1981). These layers are best explained by the migration
of clay and iron within loess following initial loss of carbonate. In Eastern England, much
of the cover-sand is thought to have been deposited during the Younger Dryas (12.5-
11.4 ka) (Bateman, 1998).
Cold-climate eolian sand may also accumulate in thicker layers to form sand sheets and
sand dunes. In both Europe and North America, they occur in areas located immediately
beyond the Late-Pleistocene ice margins (Figure 13.8). According to Koster (1988), the
sands were derived from fl ood plains, glacial outwash plains, till plains, and lake shores.
Parabolic and transverse dunes are common, similar to those that form in warm semi-arid
regions today. Facies analyses indicate a complex interaction between fl uvial, lacustrine,
and eolian processes in their formation (Ruegg, 1983; Schokker and Koster, 2004; Schwan,
1986). Under favorable conditions, wind direction can be inferred from dune morphology
and orientation, the dip of the foreset beds, and the relation of dunes to known sediment-
source areas (Koster, 1988; Maarleveld, 1960). In the southeastern Netherlands, the
majority of the sediments were deposited during successive Middle- and Late-Pleistocene
glacial periods (Kasse, 1997). The latest period of sand-sheet formation in Northwestern
Europe occurred between
14 and 12 ka, and coincided with a period of permafrost deg-
radation and increased aridity.
Like the loess deposits described earlier, cold-climate eolian sand represents further
evidence of the importance of wind in the mid-latitudes during the cold periods of the
Pleistocene.
13.4. FLUVIAL ACTIVITY
The drainage of the immediate ice-marginal, or proglacial, zone surrounding the conti-
nental ice sheets was dominated by large water bodies. These were of two kinds. First,
meltwater discharge was concentrated within wide shallow channels aligned approxi-
mately parallel to the ice margin. On the North European Plain, these channels are termed
“pradolinas” or “ürstromtalers.” They experienced episodic and repeated use, especially
toward the end stages of each cold period. In parts of Canada and the Russian Plain, large
freshwater lakes, often interconnected, were impounded against the retreating ice margin.
Detailed accounts of these water bodies are contained in the many regional geology
reports of various areas, and useful summaries, including maps, are provided by Velichko
(1982) and Fulton (1989). Second, larger fl uvial drainage systems extended away from the
ice margins. Rather then being constrained within erosive channels, these rivers formed
broad outwash plains characterized by braided-channel surfaces composed of coarse
clastic sediment. Today, similar surfaces occur around the margins of ice sheets and
glaciers, and are termed sandur (plural: “sandar”; Church, 1972; Krigstrom, 1962).
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