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HREGGVIDUR NORDDAHL HAFLIDI HAFLIDASON 《Boreas: An International Journal of Quaternary Research》1992,21(1):23-41
A composite stratigraphical sequence, the Fnjóskadalur Sequence, reveals ten cycles of glacier advances and formation of ice-dammed lakes in Fnjóskadalur in central North Iceland. Chemical analyses of the Skógar Tephra, with its type locality in this valley, have enabled a correlation with Ash zone I in deep sea sediments of the North Atlantic and with the Vedde Ash Bed on land in western Norway, where it is dated to 10,600 BP. The Skógar Tephra is composed of two layers, a basaltic tephra (STP-1) and a rhyolitic tephra (STP-2) erupted almost simultaneously from two different Icelandic volcanoes. The STP-1 tephra originates from the Katla volcano in South Iceland, and the öræfajökull volcano in Southeast Iceland is considered a plausible source of the STP-2 tephra. This new dating of the Skógar Tephra puts the three youngest glacier advances of the Fnjóskadalur Sequence within a 1000 year period between 10,600 and 9650 BP. The redated Late Weichselian glacial history now extracted from the Fnjóskadalur Sequence shows that glaciers in North Iceland were more extended in Younger Dryas and Preboreal times than previously assumed. This fits with the revised deglaciation pattern which has evolved in recent years. 相似文献
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HREGGVIDUR NORDDAHL 《Boreas: An International Journal of Quaternary Research》1981,10(4):471-476.
The Weichselian glaciation in Norht lceland is locally divided into three main stages:(1) The maximum stage, when North Iceland was ice-covered northwards to the island of Grimsey; (2) the ice-lake stage, when a series of ice-dammed lakes were formed in Fijóskadalur; and (3) the Langhöll Stadial, 14 C age about 10,000 B.P., an advance restricted to the valleys on both sides of Eyjafjördur, after the final emptying of the youngest lake in Fnjöskadalur, By combining changes in strandine gradients with time, an age of about 20,700 B.P. for the oldest ice-dammed lake is predicted. As this a ge is greater than the assumed age, 18,000 B.P., of the maximum extent of the Weichselian glaciation, it is unlikely that the maximum occurred at that time. Possibly, the maximum extent of the Weichselian glaciation in North lceland took place concurrenly with some of the early s tadials that have been identified in Arctic Canada, in East Greenland and on Svalbard. 相似文献
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ÓLAFUR INGÓLFSSON HREGGVIDUR NORDDAHL HAFLIDI HAFLIDASON 《Boreas: An International Journal of Quaternary Research》1995,24(3):245-259
In connection with a new deglaciation concept for Iceland, implying an extensive glaciation during the Younger Dryas and the decay of the Icelandic inland ice sheet during the Preboreal, the history of relative sea-level changes on Iceland has been re-evaluated. New field data from the Reykjavik area, in Faxaflói Bay southwestern Iceland, were obtained in order to construct the first stratigraphically controlled curve of relative sea-level displacements for Iceland. The curve is constructed on the basis of radiocarbon-dated shells in raised marine deposits and on tephrostratigraphically controlled and radiocarbon-dated, submerged peat deposits. The curve suggests that a post-glacial relative sea-level change of about 45 m, from + 43 m a.s.1. to — 2 m a.s.l, occurred over a period of 900 14 C-years in the Reykjavik area between 10 300 BP and 9400 BP. The sea-level curve shows a shoreline displacement of c . 5 cm 14 Cyr-1 for that period. The mean absolute uplift rate is calculated to be 6.9 cm 14 C yr-1 , which is about double the fastest rate reported from any other coastal North Atlantic site. Although this rapid uplift can probably be partly explained by a 14 C plateau around the termination of the Pleistocene, it is more than likely controlled by rapid Preboreal deglaciation, together with low asthenosphere viscosities below Iceland and the release of hydroisostatic stresses in connection with the deglaciation. 相似文献
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