Náttúrufræðingurinn - 1993, Blaðsíða 26

adjacent regions (ritstj. D.R. Bowes &
B.E. Leake). Geol. J. Spec. Iss. No. 10.
415-432.
Kvamme, T., J. Mangerud, H. Furnes &
W. Ruddiman 1989. Geochemistry of
Pleistocene ash zones in cores from the
North Atlantic. Norsk Geologisk Tids-
skrift 69. 251-272.
Magnús Á. Sigurgeirsson 1992a. Gjósku-
myndanir á Reykjanesi. M.S.-ritgerð við
Háskóla Islands. 114 bls.
Magnús Á. Sigurgeirsson 1992b. Gjósku-
gos við Reykjanes á 13. öld. Yfirlit og
ágrip, veggspjaldaráðstefna. Jarðfrœða-
félag íslands. Bls. 48-49.
Mangerud, J., H. Furnes & J. Jóhansen
1986. A 9000-year-old Ash Bed on the
Faroe Islands. Quaternary Research 26.
262-265.
Sigurður Þórarinsson 1956. Mórinn í
Seltjörn. Náttúrufrœðingurinn 26. 179-
193.
Sveinn P. Jakobsson 1979. Petrology of
Recent Basalts of the Eastern Volcanic
Zone, Iceland. Acta Nat. Isl. 26. 1-103.
Þorleifur Einarsson 1956. Frjógreining
fiörumós úr Seltjörn. Náttúrufrœðingur-
inn 26. 194-198.
Þorleifur Einarsson 1961. Pollenanalyt-
ische Untersuchungen zur spát- und
postglazialen Klimageschichte Islands.
Sonderv. Geol. Inst. Univ. Köln 6. 52
bls.
Þorleifur Einarsson 1962. Vitnisburður
frjógreiningar um gróður, veðurfar og
landnám á íslandi. Saga 1961-63. Bls.
442-469.
SUMMARY
Two early holocene tephra
layers in the Sogamýri peat
deposit, Reykjavík
, by
Magnús Á. Sigurgeirsson
National Energy Authority
Grensásvegi 9
IS-108 REYKJAVÍK
Iceland
and
Markús A. Leosson
The University of Leeds
Dep. of Earth Science
LEEDS LS2 9JT
England
Tephrochronological investigation of the
Sogamýri peat deposil in Reykjavík reveals
that at least eleven tephra layers are
preserved there (Fig. 1). The peat is
between 2 and 3 meters thick and rests
upon a blue-green clay, formed at the end
of the Weichselian glaciation. With the aid
of major element analyses, the sources for
the tephra layers can be evaluated.
According to the geochemical data, at least
five possible sources may be involved: the
Hekla, Katla, Torfajökull, Veiðivötn and
Grímsvötn or Kverkfjöll volcanic systems.
Two closely spaced tephra layers are
found near the base of the peat deposit. In
this study, special attention was paid to
these two layers, which were clearly from
early postglacial time and had not been
described in previous studies of this area.
The main objective of this paper is to
present some results obtained from geo-
chemical and textural analyses of these two
layers. Chemical analyses indicate that the
tephra layers are basaltic, of tholeiitic
composition, and that their sources may
either be in the Grímsvötn or Kverkfjöll
volcanic systems (Fig. 2). Texture analyses
indicate that the lephra layers are com-
posed of brown-coloured, angular, sparsely
vesiculated, glass shards with irregular
concave and concex surfaces. Crystals
u
136