Náttúrufræðingurinn - 1981, Blaðsíða 35

S U M M A R Y
HEIMILDIR
Sedimetary layers
below the south coast
of Iceland
by Ólafur G. Flóvenz
National Energy Authority
Grensásvegur 9, 108 Reykjavík
A careful study of four seismic refraction
profiles close to the south coast of Iceland,
indicates a low velocity layer in the crust.
The P-wave velocity in this layer is esti-
mated to be 3.6 km/s and the thickness is
0.5-0.7 km. The depth to this layer is esti-
mated 0.8-2.2 km.
In Skammadalskambar near the village
Vík on the south coast of Iceland, xenoliths
are found in palagonite formations. The
xenoliths contain marine fossils which, acc-
ording to similar fauna in the Tjörnes
sedimentary layers, indicate an age of 2.5-
3.0 m.y. for the sedimentary layers below
the south coast (Áskelsson 1960, Albertsson
1978).
This low velocity layer is interpreted as
sedimentary layer, from which the xenoliths
in Skammadalskambar are derived.
The dept to the bottom of this layer is at
1.5-2.7 km. This indicates that the crust has
subsided 5-9 mm/year on average in the last
3 m.y. as result of accumulation of new lava
and sediments.
Albertsson, Kristinn. 1978. Um aldur jarðlaga
á Tjörnesi. Náttúrufræðingurinn. 48:1-8.
Askelsson, Jóhannes. 1960. Fossiliferous xeno-
liths in the móberg formation of south
Iceland. Acta Nat. Islandica II. 3:30s.
Bjömsson, Sveinbj'órn, Stefán Arnórsson & Jens
Tómasson. 1972. Economic evaluation of
Reykjanes thermal brine area. Am. Ass.
Petr. Geol. Bull. 56:2380-2391.
Einarsson, Einar H. 1962. Fornskeljar í
móbergi í Höfðabrekkuheiði. Náttúru-
fræðingurinn. 32:35-45.
Einarsson, Einar H. 1967. Steingervingar í
Skammadalskömbum. Náttúrufræðing-
urinn. 37:93-104.
Einarsson, Porleifur, D.M. liopkins & R.R. Do-
ell. 1967. The Stratigraphy of Tjörnes,
northern Iceland, and the history of the
Bering land Bridge. í: Hopkins D.M.
(ritstj.) The Bering land Bridge. 312-
325. University Press, Stanford.
Flóvenz, Ólafur G. 1979. Jarðsveiflumælingar
á höfuðborgarsvæðinu 1976. Dýpi á lag
3. Orkustofnun OS79039/JHD17:68 s.
Flóvenz, Ólafur G. 1980. Seismic structure of
the Icelandic crust above layer three and
the relation between body wave velocity
and the alteration of the basaltic crust.
Journal of Geophysics 47, 1-3:211-220.
Pálmason, Guömundur. 1971. Crustal
structure of Iceland from explosion
seismology. Vísindafélag íslendinga.
Rit. 40:187 s.
Pálmason, Guðmundur, Jens Tómasson & Isleifur
Jónsson. 1965. Djúpborun í Vestmanna-
eyjum. Raforkumálastjóri, Jarðhitadeild
og Jarðboranir ríkisins:43 s.
177
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