Náttúrufræðingurinn - 1955, Side 79

NÁKUÐUNGSLÖGIN
185
figure. The writer maintains that this subsidence in reality was an eustatic trans-
gression, which may be called the Nucella transgression, of the probably magni-
tude of 7-—8 m (cf. Thorarinsson 1951), and corresponding to the youngest
Litorina-Tapes transgression in Scandinavia. There is reason to think that the land
had again risen nearly to the present shore line before tlie end of Subboreal Time.
Fig. 4 is an attempt at a shore line diagram for the Húnaflói region.
Fig. 5 shows some typical bog sections from Northern Iceland and Fig. 6 a
pollen diagram from a moor near Akureyri. That diagram was worked out 20 years
ago and should not be taken for more than it is worth. It, however, supports the
conclusion that can be drawn from field studies of numerous bog sections, viz.
that the Betula maximum in the moors of Northern Iceland falls witliin the Sub-
boreal Time, probably the later part of the time, at, or even above, layer II.,.
The Subboreal Time thus seems to have been the driest period in the postglacial
history of Northern Iceland.
When Bárdarson (from ab. 1895 to the late 1910:s) carried out his thorough
investigations of mollusca along the coasts of Húnaflói, be searched especially for
living specimens of Nucella lapillus, but never found a single one. It may be re-
garded as nearly certain that it did not live at the north coast of Iceland at that
time. In 1918 a single specimen of living Nucella was found at Kolbeinsá in the
northernmost part of Hrútafjördur, in 1929 18 specimens were found on the
northernmost part of Skagi, and in 1951 and 1952 Bárdarson’s son, Dr. Finnur
Gudmundsson, could state that Nucella is now abupdant at the northernmost part
of Hrútafjördur and is even found, though much more scanty, at least as far
south as Bæjará, where it certainly did not exist until 1940. It seems probably
that Nucella has been extinct at Hrútafjördur since the end of Subboreal Time
and in spite of its supposed non-pelagic larval development the present writer
regards its recent recurrence as significative of the present climatic amelioration.
After a period of ab. 3 centuries (1600—1900 A. D.) which probably were the
coldest since Subboreal Time — with the possible exception of the first centuries
of the Subatlantic Time — we have during the last decades been experiencing
a mild period which very likely is the mildest since Subboreal Time. To put it
differently we have during the present century experienced a climatic fluctuation
of a probably greater amplitude than any one since the juncture of the Subboreal and
Subatlantic Times.
HELZTU HEIMILDARIT
List of References
Áskelsson, J.: Quartargeologische Studien von Island. I. Geol. Fören. Stock. Förh. 52.
Stockholm 1930.
— Some Bemarks on the Distribution of the Species Zirphœa crispata L. and
Purpura lapillus L. on the North-Coast of Iceland. Vidensk. Medd. dansk
Naturh. Foren. Kobenhavn 1936.
Bárðarson, G. G.: Purpura lapillus L. i hævede Lag paa Nordkysten af Island.
Vidensk. Medd. dansk Naturh. Foren. Kbh. 1906.
— Mærker efter Klima- og Niveauforandringer ved Húnaflói i Nordisland.
Vidensk. Medd. dansk Naturh. Foren. Kbh. 1910.