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Lohne O.S.,University of Bergen | Mangerud J.,University of Bergen | Mangerud J.,The Bjerknes Center for Climate Research | Svendsen J.I.,University of Bergen | Svendsen J.I.,The Bjerknes Center for Climate Research
Journal of Quaternary Science | Year: 2012

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±120 cal a BP, and that the ice margin stayed in this position for 170±120 years. The subsequent retreat started at 11 590±100 cal a BP, i.e. close to the YD/Holocene boundary. Withdrawal was probably triggered by abrupt climatic warming at this time. © 2011 John Wiley & Sons, Ltd.

Romundset A.,University of Tromsø | Lohne T.S.,University of Bergen | Lohne T.S.,The Bjerknes Center for Climate Research | Mangerud J.,University of Bergen | And 3 more authors.
Boreas | Year: 2010

The first relative sea-level (RSL) curve from the mid-Hardangerfjorden area covering the entire Holocene is presented. The curve is based on a series of AMS 14C dates on terrestrial plant macrofossils across the isolation level in each of five lakes located between 3.5 and 74.5 m a.s.l. During the first 1200 years, the RSL fell very rapidly from the marine limit at 98 m a.s.l. to 33 m a.s.l., i.e. at a rate of 5.4 cm yr-1. The emergence rate then slowed considerably and was close to standstill 8000-6500 cal. yr BP. However, an emergence of 16.5 m has taken place during the past 6000 years. Radiocarbon dates of terrestrial plant macrofossils from the basal strata in a lake above the marine limit and mollusc shells from glaciomarine silt in the isolation basins yielded a mean age for the local ice-margin retreat of 11 300 cal. yr BP. This verifies that Hardangerfjorden was glaciated during the Younger Dryas - an interpretation that has recently been disputed. The ice margin retreated at a rate of about 300 m yr-1 from the position of the Younger Dryas moraine to this site some 60 km further into the fjord. © 2009 The Authors, Journal compilation © 2009 The Boreas Collegium.

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