There is need for a quantitative assessment of the importance of glaciohydraulic supercooling for basal ice formation and glacial sediment transfer. We assess the contribution of supercooling to stratified facies basal ice formation at Svı´nafellsj¨okull and Skaftafellsj¨okull, southeast Iceland, both of which experience supercooling. Five stratified basal ice subfacies have previously been identified at Svı´nafellsj¨okull, but their precise origins have not been determined. Analysis of stratified basal ice stable isotope compositions (d 18 O and dD), spatial distribution and physical characteristics demonstrates that two subfacies present at both glaciers are consistent with supercooling. These 'supercool' subfacies account for 42% of stratified facies exposed at Svı´nafellsj¨okull, although estimates at Skaftafellsj¨okull are precluded by limited basal ice exposure. Owing to their high debris contents, supercooling-related facies contribute a debris flux of 4.8 to 9.6 m 3 m À1 a À1 at Svı´nafellsj¨okull (83% of the stratified facies debris flux). Other stratified subfacies, formed by non-supercooling processes, account for 58% of the stratified basal ice at Svı´nafellsj¨okull, but only contribute a debris flux of 1.0 to 2.0 m 3 m À1 a À1 (17% of the stratified facies debris flux). We conclude that supercooling has a significant role in glacial sediment transfer, although in stratified basal ice formation its role is less significant at these locations than has been reported elsewhere.

Glaciers are highly effective agents of erosion that have profoundly shaped Earth's surface, but there is uncertainty about how glacial erosion should be parameterised in landscape evolution models. Glacial erosion rate is usually modelled as a function of glacier sliding velocity, but the empirical basis for this relationship is weak. In turn, climate is assumed to control sliding velocity and hence erosion, but this too lacks empirical scrutiny. Here, we present statistically robust relationships between erosion rates, sliding velocities, and climate from a global compilation of 38 glaciers. We show that sliding is positively and significantly correlated with erosion, and derive a relationship for use in erosion models. Our dataset further demonstrates that the most rapid erosion is achieved at temperate glaciers with high mean annual precipitation, which serve to promote rapid sliding. Precipitation has received little attention in glacial erosion studies, but our data illustrate its importance.

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The interpretation of glacigenic diamictons is a subjective process, for which quantitative support is frequently sought from parameters such as clast shape and fabric. It has been widely suggested that different glacigenic diamicton facies possess distinct clast‐fabric signatures. This paper examines this concept using a data set of 111 clast fabrics, and a synthesis of published results. Eigenvalues are calculated and compared for a variety sedimentary facies. It is concluded that clast fabric alone is not able to discriminate between different glacigenic facies, and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments. It is suggested, therefore, that although clast fabric may continue to have a role as an indicator of relative strain at specific sites, its use in the discrimination of glacigenic facies is limited. Consequently, we should be much more selective in undertaking such analyses in the future. Copyright © 1999 John Wiley & Sons, Ltd.

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