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16 Matti Sauramo, The mode of the land upheaval in Fennoscandia.
At the periphery the land emergence followed immediately on the
retreat and the diminishing of the ice-sheet, even the oldest known
shore-line of the Baltic Ice-lake having been tilted before the
formation of the succeeding beaches of the same ice-lake. In the centre of
glaciation the uplift apparently set in already during these early
times. There is no reason to believe that such was not the case. This
is. however, only an assumption. Of greater importance for our purpose
is the progress of deformation of this area as actually established by
means of the raised shore-lines. As long as there are greater remnants
of immelted ice the upheaval is fairly slow and equal throughout the
whole area, and these remnants act as a brake, hindering the normal
tilting upwards (Fig. 7). After the disappearance of this brake, the
delay has been compensated by an abnormally rapid tilting about the
hinge-line. The area inside the hinge-line bulged like a buckle on the
surface of a rubber ball. We will call the limit of this buckle the
fini-glacial hinge-line.
GOTIGLACIAL HINGE-LINE.
Another hinge-line of gotiglacial age exists in the periphery of
the glaciated area. It can be established by means of the oldest known
shore-line (BI) of the Baltic Ice-lake. In the author’s first diagram
from the year 1934 he placed the line representing this water plane
chiefly according to Munthe’s investigations at Mount Billing in
Central Sweden (Munthe 1928). In Finland only the region north-east
of Lake Ladoga was studied in this respect, first by Ramsay (1931)
and later on by the young geologist Sampo Kilpi (1932). In the
summer of 1937 the author traced the shore-line in question in the whole
of Eastern Finland, especially in Northern Carelia, checking there
earlier observations (Wilkman 1912) and at the same time making
new ones. According to the observations then made, unexpectedly
large areas of this very thinly populated region have been submerged
at the retreat of the land ice. Varved sediments occur in local basins,
though they were later on almost entirely covered by peat bogs.
The highest limit of the ice-lake is marked by shore features and also
by glacifluvial deltas, one of these being the Selkäkangas, south of
Lake Koitere and about 75 km. north-east of Joensuu. Among the
fairly numerous glacifluvial terraces that the author has seen in
Fennoscandia, Selkäkangas is the largest single one, being at the same time
also the most beautiful in its features. The flat surface of the delta,
which is 1 or 2 km broad and about 20 km. long, lies at an elevation
of about 176 m.
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