Shore-line displacement in the Murchisonfjorden area, Nordaustlandet, Svalbard - Indications for ice-free Younger Dryas and Mid-Holocene regrowth of glaciers

In Late Pleistocene, the Svalbard area was part of Barents-Kara Ice Sheet during three glacial events, correlated to marine isotope stages (MIS) 5d, 4, and 2. The shape of emergence rate isolines indicates a thicker and more extensive glaciation to the eastern parts of the archipelago than to the western parts. Also in the Murchisonfjorden area, evidence of three glacial events was found. Earlier studies concluded that glaciers in western Svalbard were at same size or smaller than today during the Younger Dryas, whereas in eastern Svalbard evidence of growing glaciers is found. This study focuses on the ice-free strip of land along Murchisonfjorden, the westernmost part of Nordaustlandet, Svalbard. The shore-line displacement was studied by the data set, that includes a total of 16 radiocarbon dated driftwood samples and isolation horizons of lake sediments. The age range for raised beaches is ca. 12 660-4800 Cal BP, and the altitude of the dated beaches varies between the present sea level and 54 m a.s.l. The average rate of emergence for the Early Holocene (11 500-8100 Cal BP) is ca. 15 mm yr-1 and for the Mid-Holocene (7400-5500 Cal BP) ca. 4.5 mm yr-1, and total emergence rates are 24 mm yr-1 and 7.5 mm yr-1, respectively. No evidence from shorelines above the present sea level and younger than ca. 4600 Cal BP was found. Higher shorelines between 54 m a.s.l. and ca. 60 m a.s.l. were observed, but suitable material for age determinations was not recovered. The marine sediment below the isolation contact of the lake Einstaken (54 m a.s.l.) was AMS-dated from foraminifera samples, and it shows an age of 12 700 Cal BP. The bulk lake sediment above the isolation contact was dated back to 13 300 Cal BP, but since the bulk 14C-dates are problematic in Arctic regions, it was not used for interpretation. The age of the contact indicates that at least locally the Mucrhinsonfjorden area was ice-free during the Younger Dryas stadial. The Early Holocene record obtained in this study indicates rapid land uplift until ca. 8100 Cal BP. Between ca. 8000-7000 Cal BP rate of the relative land uplift gradually slowed down leading finally to a transgressional phase, which coinsides approximately the age of the diamicton in nearby Isvika marine section. This may indicate a local glacier advance and/or calving glacier front at the vicinity of the site. The results show relatively steady land uplift from ca. 7000 Cal BP until 5500 Cal BP. The last 5000 years the shore line has remained stable, possibly below present sea level except for the recent centuries.