The first Holocene relative sea‐level curve from the middle part of Hardangerfjorden, western Norway

Abstract

Svendsen, J. I. 2010 (January): The first Holocene relative sea-level curve from the middle part of Hardangerfjorden, western Norway. 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 14 C 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 À1 . 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 À1 from the position of the Younger Dryas moraine to this site some 60 km further into the fjord.

Late glacial and holocene 10Be production rates for western Norway

“…Furthermore, based on 12 radiocarbon dates of plant macrofossils and shells, Romundset et al (2009) inferred that deglaciation of a site 60 km up-fjord of Halsnøy occurred at $11300 cal a BP. Consequently, the ice margin must have started to retreat from the island of Halsnøy earlier than 11300 cal a BP, in accordance with the retreat age from Halsnøy of 11590 AE 100 cal a BP.…”

“…However, assuming a typical response function of the lithosphere, most of the rebound would have occurred shortly after deglaciation and therefore the period that the site would have experienced lower production rates than modern would have been relatively short lived, lasting only some few hundred years or so (e.g. Lohne et al, 2007;Romundset et al, 2009). Because a well-constrained rebound curve exists for this part of Hardangerfjord, we incorporate corrections for isostatic rebound, which yields a 1-2% increase in 10 Be production rate if rebound were not accounted for.…”

Timing of the younger dryas glacial maximum in western Norway

“…On the contrary, we suggest that numerous observations and radiocarbon dates that have been obtained from shell-bearing tills ( Fig. 1; Supporting Information Table S1), lake stratigraphies with meltwater sediments from Halsnøy (Lohne, 2006) and Tysnes (present paper), and postglacial sediment from Tørrvikbygd (Fig 1; Romundset et al, 2010) demonstrate that the Scandinavian Ice Sheet extended to the Halsnøy Moraine during the YD. This is also consistent with the mapping of the moraine (Undås, 1963;Aarseth and Mangerud, 1974).…”

Early Holocene in Gästrikland, east central Sweden: shore displacement and isostatic recovery

“…Many investigations show a clear difference in average RSL fall between the earliest time after deglaciation and the subsequent Holocene (e.g. Clague & James 2002;Berglund 2004;Lindén et al 2006;Romundset et al 2010): the initial postglacial RSL fall is usually rapid but slows after 500-1500 years. The mechanism of isostatic rise may include a rapid response to recent or ongoing unloading and a slower underlying response, persisting at a decreasing rate up to the present, related to mass transfer within the upper part of the mantle (cf.…”