Tephrostratigraphy of An Loch Mor, nis Oirr, western Ireland: implications for Holocene tephrochronology in the northeastern Atlantic region

Abstract: Twelve definable cryptotephra layers younger than c. 8600cal. BP are reported from lacustrine core material taken from An Loch M6r, Inis Oirr, Aran Islands, western Ireland. The geochernistry of these shard layers, which represent more Holocene tephras than previously geochemically characterized from any European site outside the proximal volcanic influence of Italy or Iceland, is presented. Of these tephras, four may correlate with known Iceland-derived tephra horizons (Vo 1477, HI, Lairg A and H5); one appears to have two possible named correlatives (Hoy; 'Lairg B ' at Sluggan Bog, N Ireland); another has a plausible correlative (AD 860A); but two others represent Icelandic tephras apparently not pre-viously reported on Iceland itself, including a tephra that has geochemistry very similar to Hl (AD 1104) but which dates to c. cal. AD 840. Four tephras that date from the period c. AD 40-1400 have a distinct geochemical signature that relates to Jan Mayen, 750km to the northeast of Iceland and some 1800km distant from An Loch M6r. The results contribute substantially to the chronology of the sedi-~~~ ~ ~~~ments from An Loch Mor and, at the international level, to the tephrostratigraphy of the northeast Atlan-A tic region. The well-attested Icelandic H4 tephra (from a Hekla eruption of c. 4260cal. BP) was not HOLOCENE recorded; it is suggested that An Loch M6r lies south of its recordable distribution in this part of the RESEARCH northeast Atlantic region. Taken together with work at other sites, the findings point to a wealth of poten