Jökull - 01.12.1967, Blaðsíða 52

Fig. 4. The main features of the history of lake Stórisjór as interpreted from the sediments of the
drillhole.
MyncL 4. Yfirlit yfir sögu Stórasjóar byggt á rannsóknum sýnanna úr borholunni.
water has undoubtedly been cold, since most
of the species are characteristic for cold water.”
Fig. 4 presents a general review of the results
of the investigations and their interpretation.
Besides, the major geological events which have
occurred in the neighbourhood are mentioned.
The second column of the table shows pumice
content in per cent. Here that part of the
samples having grain size > 0.85 mm is regard-
ed as pumice. All vesicular and scoriaceous
grains are also counted as pumice. As grain
sizes smaller than 0.85 mm are reached the
grains have become so small that most of them
have broken down into glass dust. In the fifth
column of the table it is indicated with + and
-t- whether the samples contain diatoms or not.
+ rneans that diatoms were found, (+) that
they were found, but in small quantities, and
-t- that they were not founcl. Other columns
in the table are self-explanatory.
In finiglacial time, a little less than 10,000
years ago, the topography of the Tungnaá area
from the Tungnaárfjöll mountains to lake
Thórisvatn and the Kaldakvísl river was con-
siderably different l'rom the present one. To be
sure the same móberg ridges and mountains as
286 JÖKULL 17. ÁR