Glacier-permafrost interactions and glaciotectonic landform generation at the margin of the Leverett Glacier, West Greenland

Abstract

Abstract This paper describes the key characteristics of a proglacial moraine complex at the Leverett Glacier, western Greenland. The presence of a large stream-cut exposure allowed the examination of its internal structure, as well as its surface geomorphology. It is composed of a variety of ice and sediment facies, including debris-poor ice, ice-rich diamicton and ice-rich gravel. These units are glaciotectonized, with the exposure featuring a major fault and associated drag fold, a planar, erosional unconformity, and a variety of small-scale folds. Various interpretations are considered, including the possibility that the sequence represents a buried basal ice layer. However, it is argued that the structural characteristics are best explained by a two-phase model involving ice advance and proglacial or ice-marginal compression, followed by overriding and subglacial deformation and erosion, tentatively related to ice advance after the Holocene Hypsithermal ( c. 4900–3000 calendar years bp ). The polygenetic origin of this ice-marginal, glaciotectonic landform contrasts with the majority of Arctic push-moraines, which are largely considered the result of proglacial deformation and the stacking of imbricate thrust sheets of frozen sediment. This contrast may reflect differences in the thickness and spatial continuity of permafrost within the glacier foreland, and adds to the range of ice-marginal landforms associated with glacier-permafrost interactions.