Chronology of late Holocene climatic events in the northern North Atlanticbased on AMS C-14 dates and tephra markers from the volcano Hekla, Iceland

A combination of AMS(14)C dating and tephrochronology has been used to date late Holocene oceanographic events in a 335 cm marine record, covering abo ut 4600 cal. yr with sedimentation rates exceeding 80 cm 1000 yr(-1). The c ore site is located 50 km offshore on the northern Icelandic shelf. Tephra markers from Iceland serve to correlate the marine and terrestrial records. Especially notable is the presence of three geochemically correlated tephr a markers from the Icelandic volcano Hekla (Hekla 4, Hekla 3 and Hekla 1104 ). Benthic and planktonic foraminiferal abundance and distribution as well as the petrography of the sand fraction of the muddy shelf sediments are us ed as palaeoceanographic proxies. The foraminiferal assemblages reflect a g eneral cooling trend during the last 4600 yr. A marked drop in sea-surface temperatures is registered at about 3000 cal. yr BP, corresponding to the l evel of the Hekla 3 tephra. There is faunal indication of temperature ameli oration during the Medieval Warm Period and a cooling again during the Litt le ice Age. Periods of ice rafting events are indicated by ice rafted debri s (IRD) concentrations, e.g. at around 3000 cal. yr BP and during the Littl e Ice Age. The former event occurred just prior to the deposition of the He kla 3 tephra marker, the largest Holocene Hekla eruption. A correlation wit h terrestrial climatic events in Iceland is presented. A standard marine re servoir correction of 400 C-14 yr appears to be reasonable, at least during periods with high influence of water masses from the Irminger Current on t he northern Icelandic shelf. An increase to ca. 530 C-14 yr may have occurr ed, however, when water masses derived from the East Greenland Current were dominant in the area. Copyright (C) 2000 John Wiley & Sons, Ltd.