DEGLACIATION IN EASTERN AND CENTRAL ... - arkisto.gsf.fi

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CONTlNUATION CONTINUATION OF THE SALPAUSSELKÄS SALPAUSSELI(AS IN NORTH
KARELIA I(ARELIA IN THE LIGHT LIGIIT OF RECENT RECENT CONCEPTS
CONCEPIS
Biostratigraphieal Biostratigraphical and and morphologie morphological al
interpretations rehabilitated
As a consequence, consequence, the ice-marginal ice-marginal deposits in easternmost Finland and in Soviet
Karelia were were largely ignored ignored until until the the 1960s, when a fresh look was taken at the
concepts of shoreline shoreline displacement displacement (Hyvärinen 1966a, 1966a, b), and studies on the course
of the ice-marginal landforms were reopened reopened using using a geomorphological approach
(Rainio, 1972). 1972). Pollen and and radiocarbon radiocarbon evidence was used to demonstrate presence
of organic organic deposits ofYounger of Younger Dryas Dryas age in the southem southern foreland ofNorth of North Karelian
end end moraines moraines (Selkäkangas) (Selkakangas) whereas whereas at sites farther north north the pollen re record cord opens
with Early Holocene assemblages; assemblages; hence hence the end moraines moraines could be
biostratigraphically correlated correlated with the the Younger Younger Dryas Dryas (Hyvärinen 1971a, Lg7ra, 1972, Lg72,
1973).
In the early 1970s, 1970s, the the Geological Survey of Finland Finland and the geologists of Soviet
Karelia joined forces in studying studying the the deglaciation of the Salpausselkä phases
(Lukashov et al., 1981). As As a result, result, the the work ofRosberg of Rosberg on Russian Karelia becnme became
topical topical on once ce more (see Hyvärinen, 1973).
Position of the iee ice sheet front front during during
the deposition of Salpausselkä Salpausselkä I I
The The chain chain of of ice-marginal ice-marginal ridges included included in Salpausselkä Salpausselkä I comes to an end at the
Patsola Patsola marginal plain plain in Värtsilä, North North Karelia (Berghell, 1904; Ramsay, 1921; Ig2L;
Repo & Tynni, 1967, p. 136; Rainio, 1983 tll). [I]). The terrain to the east and northeast
ofthe plain rises rises and is supra-aquatic. supra-aquatic. As can be inferred from from the orientation ofthe
easternmost eastemmost plains of Salpausselkä I, the front of the continental continental ice sheet could
well weIl have continued continued north-northeastwards north-northeastwards in this area (cf. Rainio 1983 tll, [I], p. G8). 68).
Various ideas ideas about the position of the ice front northeast of Patsola have been put put
forward since the late 1970s without, however, any distinct, continuous end
moraines moraines being found to support support them. them. In the following following these studies are reviewed.
In 1978 1978 and 1980, Rainio suggested that at the time the Salpausselkä I was forming
the front of the continental continental ice sheet continued continued from Patsola Patsola northeastwards northeastwards to
Möhkö and from from there there to Russia. He maintained maintained that the position position of the ice front,
which which he called the Ilomantsi zone, was indicated indicated by the discontinuous chain of
esker deltas, ice-marginal formations and areas of ofhummocky hummocky moraines and that the
Iandforms landforms of ofthe the ice front corresponding to Salpausselkä I were within a lO-km-wide 10-km-wide
zone. In other words, the ice front had had withdrawn withdrawn about 10 km here, whereas
farther west it had remained approximately stationary stationary at Salpausselkä I.