Timing of the younger dryas glacial maximum in western Norway

Abstract

This study precisely constrains the timing of the Younger Dryas (YD) glacial maximum in south-western Norway by utilizing sediment records from lake basins. Two of the basins, located on the distal side of the mapped Herdla-Halsnøy Moraine, received meltwater directly from the ice sheet only when the ice margin reached its maximum extent during the YD. In the cores, the ice maximum is represented by well-defined units with meltwater deposits, dominantly laminated silt. Plant macrofossils in the sediment sequences are common and we obtained 18 radiocarbon ages from one of the cores. By applying Bayesian age-depth modelling we obtained a precise date for this meltwater event and thereby also for the timing of the YD glacial maximum. We conclude that the ice-sheet advance culminated at the Halsnøy Moraine at 11 760 AE 120 cal a BP, and that the ice margin stayed in this position for 170 AE 120 years. The subsequent retreat started at 11 590 AE 100 cal a BP, i.e. close to the YD/Holocene boundary. Withdrawal was probably triggered by abrupt climatic warming at this time.

Late glacial and holocene 10Be production rates for western Norway

“…We assume the sampled boulders were exposed to cosmic rays for the first time when the ice-margin retreated from the Halsnøy moraine. Lohne et al (2011) studied the sediment record from a lake basin directly fed by the ice sheet. The lake basin is located just outside the Halsnøy moraine on the island of Tysnes (Fig.…”

“…A series of 18 14 C dates were taken throughout glacial silt and across the boundary with the overlying organic sediments on terrestrial macrofossils, which should give an accurate age range of the timing of occupation of the Halsnøy moraine. Bayesian age modelling using the OxCal software package (Bronk Ramsey, 2008 (Lohne et al, 2011).…”

Early break-up of the Norwegian Channel Ice Stream during the Last Glacial Maximum

“…Third, 10 Be ages from southern Bømlo (Mangerud et al, 2013) correspond with radiocarbon ages from basal lacustrine sediments from the same island (Karlsen, 2009). Fourth, the Younger Dryas moraine in Hardangerfjorden is precisely dated by 14 C ages of distal sediments (Lohne et al, 2011) and by 10 Be ages from boulders on an associated lateral moraine (Mangerud et al, 2013). Note that we have omitted the boulders on the end moraine that were used to determine the production rate that we apply (Goehring et al, 2012).…”

10Be ages of late Pleistocene deglaciation and Neoglaciation in the north‐central Brooks Range, Arctic Alaska

“…For example, it is unknown whether glaciers in the Brooks Range responded to the abrupt climate changes that define the Lateglacial period in the North Atlantic region (Alley et al, 1993;Denton et al, 2010;Harrison et al, 2010). Although glacier advance during the Younger Dryas period (YD; 12.9-11.7 ka) may be prevalent in some areas around the North Atlantic region (Ingó lfsson et al, 1997;Lohne et al, 2012), evidence elsewhere is less definitive (e.g. Gosse et al, 1995;Mangerud and Landvik, 2007;Kelly et al, 2008).…”