Chronology and extent of the Lofoten–Vesterålen sector of the Scandinavian Ice Sheet from 26 to 16 cal. ka BP

Abstract

Laberg, J. S.: Chronology and extent of the Lofoten-Vester alen sector of the Scandinavian Ice Sheet from 26 to 16 cal. ka BP.The interplay between the onshore and offshore areas during the Last Glacial Maximum and the deglaciation of the Scandinavian Ice Sheet is poorly known. In this paper we present new results on the glacial morphology, stratigraphy and chronology of Andøya, and the glacial morphology of the nearby continental shelf off LofotenVester alen. The results were used to develop a new model for the timing and extent of the Scandinavian Ice Sheet in the study area during the local last glacial maximum (LLGM) (26 to 16 cal. ka BP). We subdivided the LLGM in this area into five glacial events: before 24, c. 23 to 22.2, 22.2 to c. 18.6, 18 to 17.5, and 16.9-16.3 cal. ka BP. The extent of the Scandinavian Ice Sheet during these various events was reconstructed for the shelf areas off Lofoten, Vester alen and Troms. Icecaps survived in coastal areas of Vester alen-Lofoten after the shelf was deglaciated and off Andøya ice flowed landwards from the shelf. During the LLGM the relative sea level was stable until 18.5 cal. ka BP, and thereafter there was a sea-level drop on Andøya. Thus, relative sea level (i.e. a sea level rise) does not seem to be a driving mechanism for ice-margin retreat in this area but the fall in sea level may have had some importance for the grounding episodes on the banks during deglaciation. The positions of the grounding zone wedges (GZWs) in the troughs are related to the morphology as they are often located where the troughs narrow.

New geophysical evidence for a revised maximum position of part of the NE sector of the Greenland ice sheet during the last glacial maximum

“…These small ridges are inferred to be recessional moraines (e.g. Ó Cofaigh et al 2008;Rydningen et al 2013;Vorren et al 2015). The majority of these ridges were most probably formed during halts and/or minor re-advances of the grounding line.…”

Deglacial dynamics of the Vestfjorden – Trænadjupet palaeo‐ice stream, northern Norway

“…IRD peaks corresponding to glacial advances were also found by Vorren et al . () in the offshore record. However, they also envisaged a correspondence between the release of icebergs at glacial retreats and IRD peaks.…”

“…These expansions to the shelf break are locally termed Egga I and II advances, in accordance with Andersen (, ), separated by the Andøya interstadial (Vorren et al . ). Egga II was estimated to have occurred prior to 22.2 ka BP offshore from Andøya (Vorren et al .…”

“…Egga II was estimated to have occurred prior to 22.2 ka BP offshore from Andøya (Vorren et al . ). Results from the continental margin to the south of Lofoten showed that the sedimentary environment was significantly influenced by fluctuations of the Fennoscandian Ice Sheet, repeatedly reaching the outermost shelf between c. 25.9–18.1 ka BP (Dahlgren & Vorren ; Rørvik et al .…”

Causes of time-transgressive glacial maxima positions of the last Scandinavian Ice Sheet

“…Clark et al (2012), Svendsen et al (2015) and Hughes et al (2016), however, consider the possibility of a long period of sustained confluence between the two ice sheets, but with reduced extent over the North Sea area following a preceding phase of maximum western expansion. Regardless of these uncertainties, the general picture of the southwestern flank of the ice sheet is that of a highly oscillatory ice margin with multiple advances and retreats following early attainment of maximum icesheet limits (e.g., Nygård et al, 2004Nygård et al, , 2007Hubbard et al, 2009;Sejrup et al, 2009;Mangerud et al, 2013;Vorren et al, 2015;Hughes et al, 2016). At the same time, there was steady eastward growth of the ice sheet (Hughes et al, 2016), finally culminating in long, low-gradient ice lobes in NW Russia .…”