Hreggviður Norðdahl kynnir Aldursákvarðanir með geislakoli og meðhöndlun þeirra og umhverfisbreytingar á Íslandi á árabilinu frá 15.000 til 9000 árum fyrir nútíma (1950 AD).
In the talk I will give a short overview of the Last Glacial Maximum (LGM) extent (~25.0 cal. ka BP) of the Icelandic Ice Sheet (IIS) when it reached out onto and to the edge (200 m b.s.l.) of the Iceland shelf. At that time the ice sheet was so thick that no nunataks (ice-free enclaves) protruded above the surface of the extended ice sheet. When the IIS was growing, getting both thicker and more extended, its increasing weight depressed the crust at such a rate that a glacio-isostatic equilibrium prevailed at all times, also during the post LGM deglaciation of Iceland.
The earliest dated marine shorelines in Iceland are found on the Melrakkaslétta peninsula (14.9 cal. ka BP) in Northeast Iceland and in Stóri-Sandhóll (14.7 cal. ka BP) in West Iceland. These shorelines were formed subsequently to to a collapse of the IIS and during a brief period with little or no glacio-isostatic uplift. Then, in a period of about 1000 cal. a, the IIS retreated reaching its Late Weichselian minimum extent (~20-25% of its LGM volume) with relative sea level (RSL) rapidly falling down to and eventually well below its present-day position.
Later, at two separate occasions, the IIS advanced depressing the crust causing relative transgression of the sea with formation of shorelines now found at about 60 and 40 m a.s.l., respectively. During final retreat of the IIS towards central parts of Iceland, RSL fell and reached its lowest position (~40 m b.s.l.) some 9.0 cal. ka BP. About 7.4 cal. ka BP RSL was situated some 3-5 m a.s.l. in Northeast Iceland and has since then throughout Iceland been oscillating around 0 m a.s.l.
Norðdahl et al. 2018: Glacio-isostatic age modelling and Late Weichselian deglaciation of the Lögurinn basin, East Iceland. Boreas, doi.org/10.1111/bor.12366
Norðdahl & Ingólfsson 2015: Collapse of the Icelandic ice sheet controlled by sea-level rise? Arktos 1:13 doi.org/10.1007/s41063-015-0020-x
Pétursson et al. 2015: Late Weichselian history of relative sea level changes in Iceland during a collapse and subsequent retreat of marine based ice sheet. Cuadernos de Investigación Geográfica 41, doi.org/10.18172/cig.2741
dagskrá vorsins 2019