Náttúrufræðingurinn - 1964, Blaðsíða 46

140
NÁTTÚRUFRÆÐINGURINN
S U M M A R Y
C14 Datings of Quaternary Deposits in Iceland
by Kjartansson, G., Thorarinsson, S. ancl Einarsson, Th.
Introductory
by Signrdur Thorarinsson
Museum o/ Natural History, Department of Geology, Rcylijavik.
Since 1950 geologists have collected a lot of samples in Iceland for C14
datings and these samples have been dated at different laboratories in Europe
and America. Most of these samples have been collected and submitted
to dating by the authors of the paper here presented. They have felt it
justified to list all the datings in one paper, together with the datings of
samples collected by others, for the convenience of students of the Quaternary
geology of Iceland, who otherwise would have to seek these datings in a great
number of papers.
In the present paper the localities and sections where the samples were taken
are shortly described, the purpose of the dating is outlined and the consequences
of the determined ages briefly discussed. The figures in brackets refer to the
key map Fig. 1. The results given are expressed in years B. P.
The authors are greatly indebted to the directors and staffs of the C14 dating
laboratories where the samples ltave been datecl.
Dating of Some Lava-Flows in S and SW Iceland
by Guðmundur Kjarlansson
Museurn of Nalural History, Department of Geology, Reykjavik.
Peat underlying- the Thjórsá Lava at Þjórsárbrú (16)
8065 ± 400 years (W-482)
8170 ± 300 years (W-913)
Both samples were taken from the surface layer of the peat and may be con-
sidered of practically the same age as the overlying lava (Fig. 2). This lava-flow,
called the (Great) Thjórsá Lava (Þjórsárhraun), is the largest known lava-flow
in Iceland and even on Earth (Fig. 3). Tlie structure and surface forms of
this huge flow are everywhere those of a postglacial lava that has never been
covered by a glacier or by the sea. Therefore, its dating at about 8000 years
B. P. also shows that by that time the last glacial ice-sheet had receded at least
so far inland as to leave the whole course of the lava-flow ice-free. As the
source of the Thjórsá Lava — probably an eruptive fissure, now buried under
younger volcanic products — is situated in the part of the Central Highlands
from where the glacial striæ radiate in all directions, the dating of this lava-