Fróðskaparrit - 01.01.1998, Síða 185

Holocene Tephra Layers
in the Faroe Islands
Holosenar tefrafláir í Føroyum
191
Andrew J. Dugmore and Anthony J. Newton
University of Edinburgh, Department of Geography, Drummond Street, Edinburgh
EH8 9XP, Scotland, UK
Phone: + 44 131 650 8156, fax: + 44 131 650 2524, emaii: ajd@geo.ed.ac.uk
Úrtak
Tekin um minst fimm kisiltefrafláir og eina basalttefra-
flógv úr holosenari tíð eru funnin í Føroyum. Tað er
sannlíkt, at allar hesar tefrafláimar hava sín uppruna í
Islandi. Harafturat benda søgulig skjøl á møguligt avfall
frá trimum nýligum eldgosum úr Køtlu í 1625, 1660 og
1755, men enn er eftir at staðfesta hetta við tefrafundum.
Ein av basaltfláunum í Føroyum, sum vit í løtuni vita
um, er nevnd Saksunarvatnstefran, og hon settist um
9100 BP. Hon myndar eina týðandi økisisokron, sum
fevnir um allan landnyrðingspartin av atlantsøkinum.
Her verður greitt frá nýggjum jarðevnafrøðiligum tilfari
um Saksunarvatnstefruna og eini eldri kisiltefru, sum er
merkt L3574. Meðan upprunin hjá tveimum teimum
yngstu holosenu kisiltefrufundunum í Føroyum fram-
vegis er óvissur, leggja vit jarðevnafrøðiligt tilfar fram
um tvær miðholosenar kisiltefrur, ið eyðmerkir tær sum
íslendsku tefrurnar H-4 (3800 BP) og H-S (3500 BP).
Abstract
Evidence of at least five silicic and one basaltic tephra
layers of Holocene age have been found in the Faroe Is-
lands. All these tephras are likely to have originated in
Iceland. In addition, historical records suggest fallout
may have occurred after three recent eruptions of Katla
in 1625 AD, 1660 AD, 1755 AD, but this has yet to be
confirmed with finds of tephra. The one basaltic layer
currently known in Faroe is called the Saksunarvatn
tephra, and was deposited about 9100 BP. It forms an
important regional isochrone, that is present throughout
the north-east Atlantic region. We report new geochem-
Fróðskaparrit 46. bók 1998: 191-204
ical data on the Saksunarvatn tephra from the type site,
and an older silicic tephra designated L3574. While the
identity of the two youngest Holocene silicic tephras
found in Faroe remains uncertain, we present geochem-
ical data on two mid-Holocene silicic tephras which
identifies them as the Icelandic tephras H-4 (3800 BP)
and H-S (3500 BP).
Introduction
A key step in understanding environmental
changes in the North Atlantic Islands is de-
termining the timing of events. No one
technique satisfies all requirements for pre-
cision, accuracy and applicability, and
there is a continuing search for new tech-
niques to both refine and extend existing
chronologies. Tephrochronology is one
well-established dating method that is gai-
ning wider applications in the North At-
lantic region due to a series of recent
methodological advances (Dugmore et al.,
1995a). Tephrochronology is based on the
identification, correlation and dating of lay-
ers of volcanic ash, and provides a means of
defming precise time-parallel marker hori-
zons, or isochrones.
In the North Atlantic region, tephro-
chronology is based on the ash layers pro-
I