Chapter 52 - Iceland: glacial landforms from the Younger Dryas Stadial

Abstract

The Iceland ice sheet (IIS) started to reexpand at the end of the Bølling–Allerød interstadial and the onset of the Younger Dryas (YD) due to climate deterioration and cooling of the marine environment associated with the southward migration of the Polar front and the shutdown of the Irminger Current. Increased glacial load related to the reexpansion of the IIS caused isostatic depression and transgression of relative sea level, resulting in widespread formation of well-preserved YD shorelines. These shorelines commonly occur at altitudes between ~30 and ~100m a.s.l. and are typically truncated within fjords to delimit the extent of outlet glaciers and ice streams. Recent studies suggest that the IIS margin experienced significant oscillations and was more dynamic during the YD than previously thought. This is particularly well demonstrated by a series of glaciotectonic end moraines in West Iceland and ice-lake strandlines in central North Iceland. A modified reconstruction of the IIS during the YD shows that it extended beyond the present coastline in many major fjords and was separated from an independent ice cap over the West Fjords. The YD age of the IIS margin is generally constrained with absolute ages from ice-marginal sediments and landforms, bedrock surfaces and erratics, as well as tephrochronology and stratigraphical and morphological correlations with features of Bølling–Allerød or Preboreal (Early Holocene) age.