Fróðskaparrit - 01.01.1998, Síða 295

ÚTBREIÐSLA AV SEINGLASIALARITEFRU f NORÐURLONDUM
301
vatn Ash is probably the Grímsvotn vol-
cano on south-eastern Iceland and this ma-
jor basaltic eruption has been dated to c.
9000 l4C years BP (e.g. Birks et al., 1996)
or to c. 10,400 - 10,200 ice-core years BP
in the GRIP and GISP2 ice cores (Gronvold
etal., 1995; Zielinski et al., 1997).
Conclusions
The possibility for establishing a tephro-
chronological framework for the Last
Glacial-Interglacial Transition in south
Scandinavia has been improved greatly by
the discovery of several new sites with the
Vedde Ash in south Sweden and by the ap-
plication of the new technique for extract-
ing tephra shards from minerogenic de-
posits. The đispersal fans of the Laacher
See Tephra and the Icelandic tephras may
in some areas coincide, so that sites with
more than one tephra horizon can be found.
This would be a great step forward as it
would enable many sediment sequences to
be tied directly to the ice-core records, and
it would also provide a link between the
tephrochronological frameworks of North
and Central Europe. The most suitable ar-
eas for further research include the south-
ern Baltic Sea area and adjacent land areas,
e.g. northern Germany, Denmark and south
Sweden (cf. Fig. 1).
The Swedish clay-varve chronology (the
“Swedish Time Scale”) is presently regard-
ed as floating with an offset of 600-800
years to other calendar-year based time-
scales (e.g. Wohlfarth, 1996). If time-syn-
chronous tephra horizons can be detected
within the Swedish Time Scale, then the
possible errors and the precision of this cal-
endar-based time-scale can be determined
independently.
Acknowledgements
I am grateful to Chris Turney, John Lowe, Steve Roberts
and Andy Dugmore for many stimulating discussions on
tephrochronology. Laszlo Madarasz drew the map.
References
Bard, E., Amold, M., Mangerud, J., Paterne, M.,
Labeyrie, L., Duprat, J, Melieres, M.-A., Sønste-
gaard, E. and Duplessy, J.C. 1994. The North Atlan-
tic atmosphere-sea surface 14C gradient during the
Younger Dryas climatic event. Earth and Planetary
Science Letters 126: 275-285.
Bennett, K., Boreham, S., Sharp, M.J. and Switsur, V.R.
1992. Holocene history of environment, vegetation
and human settlement on Catta Ness, Lunnasting,
Shetland. Journal ofEcology 80: 241-273.
Birks, H.H., Gulliksen, S., Hafliðason, H. and Mange-
rud, J. and Possnert, G. 1996. New Radiocarbon
Dates for the Vedde Ash and the Saksunarvatn Ash
from Western Norway. Quatemary Research 45:
119-127.
Bjorck, S., Ingólfsson, O, Hafliðason, H., Hallsdóttir,
M. and Anderson N.J. 1992. Lake Torfadalsvatn: a
high resolution record of the North Atlantic ash zone
I and the last glacial-interglacial environmental
changes in Iceland. Boreas 21: 15-22.
Bjorck, S., Kromer, B., Johnsen, S., Bennike, O., Ham-
marlund, D„ Lemdahl, G„ Possnert. G„ Rasmussen,
T.L., Wohlfarth, B„ Hammer, C.U. and Spurk, M.
1996. Synchronized Terrestrial-Atmospheric Degla-
cial Records Around the North Atlantic. Science
214: 1155-1160.
van den Bogaard, P. and Schmincke, H.-U. 1985.
Laacher See Tephra: A widespread isochronous late
Quaternary tephra layer in central and northern
Europe. Geological Society of America Bulletin 96:
1554-1571.
Bunting, M.J. 1994. Vegetation history of Orkney,
Scotland: Pollen records from two small basins in
West Mainland. New Phytologist 128: 771-792.
Edwards, K.J. and Craigie, R. 1998. Vegetatation
change associated with the deposition of Saksunar-
vatn ash in the Faroe Islands. Fróðskaparrit 46: 245-
258.