Rit (Vísindafélag Íslendinga) - 01.06.1976, Page 172
well be derived from a precipitation deposited more than 10 000
years ago.
Our ðu-results are in good agreement with the assumption that
the hot springs and wells at Húsavík, Hafralækur, Reykjahverfi,
Laugar and Marteinsflæða (sample No. 203) all discharge water
from a main thermal groundwater stream which flows from Vatna-
jökull to the north coast, hut that it takes more than 10 000 years
for the water to flow for the entire distance of approximately 150
km.
The water at Marteinsflæða, approximately 25 km north of
Vatnajökull, has the same 5D-value as found at the present in the
glacier, which is in accordance with our assumption that this water
is probably only a few hundred years old on the average. The water
at Húsavík and Hafralækur, 150 km north of the glacier with
5D = — 130%o to — 142%0, is apparently at least 10 000 years old.
Thus it tums out that the water at Laugar and Reykjahverfi, with
ðD = — 117%0 and 8D = — 111 %0 respectively, might well be de-
posited in times when the 5D-value of the precipitation changed
from its ice-age value to a value which is the same as in present
day precipitation. In other words, the water at Laugar and Reykja-
hverfi should be as much as 8000 to 10 000 years old on the average.
Of course the conclusion conceming Laugar and Reykjahverfi is
rather speculative. These intermediate ðD-values could equally well
be explained by assuming mixing of thermal water with more
local groundwater. More detailed studies performed on this area
might, however, either verify or disprove the above hypothesis.
Therefore drilling of more holes in this area, from which water
samples could be collected for analysis, would be of a great interest.
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