Heinabergsjökull and Skalafellsjökull, Iceland: active temperate piedmont lobe and outwash head glacial landsystem

Abstract

A 1:15,000 scale map of the glacial geomorphology and surficial geology of the Heinabergsjökull and Skalafellsjökull glacier forelands in southeast Iceland depicts a landsystem imprint of actively receding temperate glaciers in a mountain terrain with a high glacifluvial sediment yield. The landsystem is characterised by the three diagnostic depositional domains for active temperate glacier systems (marginal morainic; subglacial; glacifluvial/glacilacustrine) together with site-specific landform-sediment assemblages indicative of jökulhlaup drainage from ice-dammed lakes. Other features are overridden moraines and fluted kame terraces, indicative of ice-marginal and glacifluvial palimpsests preserved beneath temperate glacier ice. A significant outwash head in front of Heinabergsjökull records the long-term accumulation of proglacial outwash and was responsible for a radical change in proglacial drainage patterns (topographically unrestricted to restricted) once the glacier snout had receded from the ice-contact face of the landform. The Heinabergsjökull/ Skalafellsjökull foreland constitutes a modern analogue for active temperate piedmont lobes associated with the construction of large outwash heads fed by high glacifluvial sediment yields. This is one of the most common glacial depositional scenarios associated with the more restricted, mountain-based, average glaciation style during a typical cold stage.

Fláajökull (north lobe), Iceland: active temperate piedmont lobe glacial landsystem

“…This landsystem signature displays many similarities to that of the neighbouring forelands of Heinabergsjökull and Skálafellsjökull (Evans & Orton, 2014), indicative of all these glacier snouts being characterized by the dynamics of active temperate piedmont lobes. However, the density of overridden moraines and widespread occurrence of sawtooth moraines (cf.…”

“…More common are thin tills (<1 m thick) and individual recessional push moraines, which are produced every year and typically have a sawtooth or crenulated plan form ( Figure 5). This morphology has been clearly related in Iceland to construction along glacier snouts strongly indented by closely spaced, longitudinal crevasses or pecten (Evans & Orton, 2014;Evans & Twigg, 2002;Price, 1970;Sharp, 1984). The localized close spacing of these moraines, together with annual shifts in the positioning of pecten, gives rise to areas of extremely complex superimposition ( Figure 5).…”

“…They are inset, low-amplitude arcs of fluted till (cf. Evans & Orton, 2014;Evans et al, 2009;Evans & Twigg, 2002;Krúger, 1994) deposited prior to or during glacier advance to the historical Little Ice Age limit and then superimposed by sharper relief recessional push moraines during snout recession. The crests of the more recent push moraines are predominantly orientated parallel to the summit crests of the overridden moraines, making them easy to distinguish from other adornments including crevasse fill ridges and till eskers.…”

Submarine landform assemblages and sedimentary processes related to glacier surging in Kongsfjorden, Svalbard

“…In places the Kongsfjorden ridges exhibit a saw-tooth pattern in planform, which could be related to formation by a combination of longitudinal crevasse infill and sediment pushing at the glacier snout [21,24,26,70]. This could suggest that both processes were active in Kongsfjorden, and that the De Geer moraines thus reflect a combination of recessional push moraines and crevasse-squeeze ridges.…”

Snæfellsjökull volcano-centred ice cap landsystem, West Iceland

“…Small areas of the fluted forelands, especially on the Blá-gilsjökull foreland, are characterized by discontinuous arcuate chains of low amplitude ridges (Figure 8), which are interpreted as overridden moraines (sensu Evans, Archer, & Wilson, 1999, 2009, 2015aEvans & Orton, 2014;Evans & Twigg, 2002;Krüger, 1994).…”