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This paper describes the internal architecture of a push moraine formed by a winter-spring surge of Hagafellsjokull-Eystri (Iceland) in 1998/99. The sedimentary architecture of this push moraine consists of a multilayered slab of glaciofluvial sediments with a monoclinal structure that has been displaced laterally by the advancing ice margin. The crest and ice-distal face of the moraine consist of subhorizontal sediment sheets, while the ice-proximal face dips steeply (45° to 90°) towards the ice margin. The core of the moraine consists of frozen sediment and thin slabs of glacier ice are embedded in its proximal face. The sediment slabs are characterized by both brittle and ductile styles of deformation. We argue that the observed variation in deformation style is dependent on whether the glacial foreland was frozen or unfrozen at the time of displacement. Frozen foreland would behave in a brittle fashion, while unfrozen foreland is likely to have deformed in a more ductile manner. The associated spatial variations in the degree of foreland freezing could be explained by variation in ice-marginal snow cover. We conclude that the thermal regime of the foreland, and the timing of the ice advance, is of importance to the style of internal deformation found within ice-marginal push moraines.

Although eskers are frequently described glaciofluvial landforms, they are poorly understood. To assist with the interpretation of Pleistocene examples, modern analogue data are required. This paper documents the morphology, sedimentology and formation of a 650 m long esker system in front of the high-arctic glacier Vegbreen in Svalbard. The esker is located between the Neoglacial maximum and the present ice front and appears to have formed both as a supraglacial trough-fill and as a channel/conduit-fill along the suture formed by two confluent glacier lobes. A range of sedimentary facies is preserved within this ridge system providing evidence for braided rivers, ephemeral lakes, episodic flow regimes and sediment gravity flows. This case study provides an important analogue for glaciofluvial sedimentation between retreating ice lobes.

The tidewater glacier complex of Kongsvegen/Kronebreen, at the head of Kongsfjorden in north-west Spitsbergen, has advanced rapidly several times since its Neoglacial maximum. Two such advances, 1869 and 1948, are well constrained in time and space and are widely interpreted as glacier surges. During the 1869 advance an ice-dammed lake formed on the western side of Ossian Sarsfjellet. This ice-dammed lake is associated with a thrust moraine complex. Four lake levels are identified, two of which are associated with rock-cut shorelines implying a degree of lake stability. The history of this lake, the nature of the ice dam and its relationship to the thrust moraine complex are discussed. The lake history spanning 28 to 35 years is used to assess the ice-marginal dynamics of the Kongsvegen/Kronebreen glacier. It is concluded that, contrary to previous suggestions, the rapid advance of this tidewater glacier may simply be an example of a non-climatic ice-marginal fluctuation, of the type common to tidewater glacier, as opposed to a glacier surge. A second ice-dammed lake, to the east of Ossian Sarsfjellet, formed sometime after 1869 as the ice retreated, and still exists today. This largely supraglacial lake is associated with a very different geomorphological assemblage, which has a poor long-term preservation potential. The geomorphological characteristics of the two lakes on Ossian Sarsfjellet are compared and used to discuss the problems associated with the recognition of ice-dammed lakes within the Pleistocene record. On the basis of the evidence presented here, ice-dammed lakes may be more common during deglaciation than currently suggested.

Areas of apparently chaotically organised moraine mounds and ridges are commonly associated with British Younger Dryas glaciers, and are also found at many contemporary glacier margins (Boulton & Eyles 1979; Benn 1992; Bennett & Boulton 1993b; Hambrey et al. 1997). Particularly in the British context, such landforms have commonly been referred to as ‘hummocky’ moraine. Whilst this term is undoubtedly an apt description of their morphology, genetic connotations have become attached to it, with some authors using it exclusively to refer to sediment-landform associations associated with wasting ice (e.g. Benn & Evans 1998: p. 483). Work undertaken over the last two decades has demonstrated that British Younger Dryas ‘hummocky’ moraine only rarely formed in association with stagnant ice, and it is now clear that they are polygenetic in origin (e.g. Benn 1992; Bennett & Boulton 1993b). For this reason the non-genetic, and similarly descriptive, ‘moraine-mound complex’ has been proposed for features of undetermined origin (Bennett et al. 1996b), and this term is adopted here.