Jökull - 01.12.1983, Page 110

maximum extent of glaciation in North-West Ice-
land. It is not unlikely that the Skagi lake was
formed at the ice-lake stage in F njóskadalur and it is
tentatively suggested, that the age of the Skagafjall
deposits is 17,000-20,000 B.P.
The provenance of the tephra is from one of the
volcanic systems which are still active or dormant in
Iceland. In postglacial time four volcanoes, Hekla,
Askja, Oræfajökull and Snæfellsjökull are responsi-
ble for most of the acid explosive eruptions (Thorar-
insson 1958). Askja belongs to the tholeiitic series,
Hekla and Oræfajökull to the transitional alkalic
series and Snæfellsjökull to the alkalic seríes(Jakobs-
son 1979). The Skagafjall tephra is tholeiitic in com-
position and most likely originated from Askja or
the Dyngjufjöll area.
Hammer (1980) has shown that most, if not all
violent eruptions that have occurred in the North-
ern Hemisphere in the last 10,000 years can be
detected in cores from the Greenland ice. It is then
possible that aerosols from the eruption, which
produced the Skagafjall tephra, can be detected in
the Greenland ice and then dated exactly.
ACKNOWLEDGEMENTS
The Jield work was mostly carried out in August 1979
and June 1980, and was financed by the author. The field-
work was used as a basis for a 4th year’s thesis at the
University of Iceland (Sigurvinsson 1982). Supervisor dur-
ing fieldwork and preparation of the thesis was Dr. Jón
Eiríksson and I am grateful lo himfor valuable discussions,
assistance and also for reading the manuscript and improv-
ing the English text. Thanks are also due to Professor
Thorleifur Einarsson for his advice and commenls. My
thanks are also due to Dr. Sigurður Steinthorsson for the
chemical analysis. I am also grateful to all others who have
contributed to the work by inspiring discussion.
REFERENCES
Agterberg, F. P. and I. Banerjee 1969: Stochastic model
for the deposition of varves in glacial lake, Bar-
low-Ojibway, Ontario, Canada. Can. J. Earth
Sci. 6: 625-652.
Ashley, G. M. 1975: Rhythmic sedimentation in
glacial lake Hitchcock, Massachusetts-Conn-
ecticut. In: Topling, A. V. and MacDonald, B. C.
(eds.): Glaciofluvial and Glaciolacustrine Sedi-
mentation. Soc. Econ. Palaeontol. Mineral.
Spec. Publ. 23: 304-320.
Einarsson, Th. 1971: Jarðfræði. Heimskringla,
Reykjavík, 254 pp.
Embleton, C. and C. A. M. King 1975: Glacial geo-
morphology. London, Edward Arnold, 583 pp.
Flint, R. F. 1971: Glacial and Quatemary geology.
New York. John Wiley and Sons, 892 pp.
Flint, R. F.,J. E. Sanders and J. Rodgers 1960: Dia-
mictite: A substitute term for symmictite. Bull.
Geol. Soc.Am. 71: 1809-1810.
Galehouse, J. S. 1971: Sedimentation Analysis. In:
Carver, R.E. (ed.): Procedures in sedimentary
Petrology. New York, John Wiley and Sons, 653
pp.
Geer, G.De 1912: A geochronology of the last 12,000
years. C. R. llth int. geol. Congr. (Stockholm,
1910) 1: 241-258.
Gilbert, R. 1975: Sedimentation in Lillooet Lake,
British Columbia. Can. Earth Sci. 12: 1698-
1711.
Gustavson, T. C. 1975: Bathymetry and sediment
distribution in proglacial Malaspina Lake,
Alaska. J. Sed. Pet. 45: 450-461,
Hammer, C. U. 1980: Acidity of polar ice cores in
relation to absolute dating, past volcanism, and
radioechoes. J. ofGlaciol. 25 (93): 359-372.
Ingram, R. L. 1954: Terminology for the thickness of
stratiíication and parting units in sedimentary
rocks. Geol. Soc. Am. Bull. 65: 937-938.
Jakobsson, S. P. 1979: Outline of the petrology of
Iceland. Jökull 29: 57-73.
Kuenen, Ph. H. 1951: Mechanics ofvarve formation
and the action ofturbidity currents. Geol. Fören.
Förh. 73: 69-84.
Mathews, W. H. 1965: Physical limnology and sedi-
mentation in a glacial lake. Geol. Soc. Am. Bull.
67: 537-552.
Norddahl, H. 1981: A prediction of minimum age for
Weichselian maximum glaciation in North Ice-
land. Boreas 10: 471-476.
Rust, B. R. and R. Romanelli 1975: Late Quaternary
subaqueous outwash deposits near Ottawa,
Canada: In: Topling^A. V. and B. C. MacDonald
(eds.): Glaciofluvial and Glaciolacustrine Sedi-
mentation. Soc. Econ. Palaeontol. and Mineral.
Spec. Publ. 23: 177-192.
Shaw,J. R., R. GilbertandJ.J. Archer 1978: Proglacial
lacustrine sedimentation during winter. Arctic
and Alpine Res. 10: 689-699.
Sigurvinsson, J. R. 1982: Kvarter landmótun útness-
ins milli Dýrafjarðar og Önundarfjarðar.
Unpubl. 4th year‘s thesis, University of Iceland,
87 pp.
Thorarinsson, S. 1958: The Öraefajökull eruption of
1362. Acta Nat. Islandica, 2(2): 99 pp.
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