Jökull - 01.12.1984, Blaðsíða 126

Concurring with Bárdarson (1923) who suggested
the possibility of the ridge Skorholtsmelar in
Leirársveit being a terminal moraine, Th. Einars-
son (1960) proposed a Late Weichselian glacial
readvance which he named Bessastadir-Leirár-
sveit readvance. In a later paper (Th. Einarsson
1961) changed the name of the readvance to the
Álftanes readvance, and has since correlated it
with the Older Dryas of Scandinavia (Th. Einars-
son 1967, 1968, 1979). Th. Einarsson (1960,
1968) suggested that the maximum transgression
in Iceland occurred in Alleröd time.
Ashwell (1967, 1975) struck a note of sceptic-
ism when he recognized fossiliferous silty
deposits at Stóri Sandhóll in the entrance to
Skorradalur as in situ marine sediments. He pub-
lished radiocarbon dates for shells collected from
the silt at an altitude of 130 m above sea level
(Table 1), and proposed that prior to about
12,500 BP the sea level was higher than the silty
deposits at Stóri Sandhóll. Later, according to
Ashwell, the sea level fell to about 145 m above
present sea level, and later still to about 65 m
above sea level. This interpretation has been
contradicted by Icelandic workers, who consider
the Stóri Sandhóll sediments to be stratified tills,
pushed into place by a glacier advancing over
marine sediments in the Skorradalur valley (Th.
Einarsson 1968, Torfason 1974, G. Sigbjarnar-
son, personal communication 1982). Ashwell
(1975) suggested that the question of ancient sea
levels in the Borgarfjördur region should be left
open until more detailed data were available.
Thorarinsson (1956, 1958) and Jónsson (1957)
pointed out that the sea level changes in Iceland
are not well known, and that only a few ancient
shorelines have been carefully levelled (Jónsson
1957, p. 144).
It has been suggested that glacial isostatic
responses are very rapid in Iceland (Thorarinsson
1958, T. Einarsson 1966, Imsland 1982), and a
chronological frame for the major Late Weichse-
lian and Holocene changes has been suggested
(Thorarinsson 1956, Th. Einarsson 1961, 1968).
However, detailed stratigraphical control of
events is lacking.
General remarks on the Weichselian glaciation in
Iceland with reference to the Borgarfjördur region
Thoroddsen (1891) commented on the alpine
character of the Skardsheidi scenery. He was the
first geologist to suggest the possibility that nuna-
taks had existed in Iceland during the Glacial
Period (Thoroddsen 1906). Thorarinsson (1937,
p. 171) carried this thought further and suggested
that the whole upper part of the Hafnarf-
jall-Skardsheidi massif above 400 m a. s. 1. had
“projected above the mighty ice stream that
found its way down across the Borgarfjördur
plain”. He published a sketch map of areas not
covered by the continuous inland ice during its
maximum extension, and there included the Haf-
narfjall-Skardsheidi massif and Mount Akrafjall.
On the basis of botanical evidence, Steindórsson
(1962) pointed out the Hvalfjördur region as an
ice-free plant refugium during the Weichselian.
Th. Einarsson (1961, 1963, 1967) agreed with
Thorarinsson and Steindórsson on the possible
ice-free areas, but later seemed to question their
importance and extension when he stated that “at
the maximum of the last glaciation most of Ice-
land was covered with glaciers, although some
nunataks may have existed, mainly in northern
Iceland” (Th. Einarsson 1979, p. 18). Th. Einars-
son (1971, 1978) suggested that during the
Weichselian Iceland was covered by a large ice—
cap, with a major inland ice divide, from which
glaciers flowed in all directions. During the
deglaciation the ice-cap broke up, and local ice
centres and divides were active for a rather short
period (Th. Einarsson 1971, p. 221).
Kjartansson’s (1955) investigations of glacial
striae support this proposal of Th. Einarsson.
Andersen (1981, p. 35) strongly echoed the same
view when he stated that “most of Iceland was
covered by an ice sheet in Late Weichselian
times” and “the maximum Late Weichselian ice
front probably lay on the shallow banks off the
coast”.
T. Einarsson (1977) suggested that it was quite
possible that large areas in Iceland remained ice
free during the Weichselian maximum. He stated
that there were many separate glaciated areas
during the Older Dryas and that the whole pic-
ture of the Late Weichselian in Iceland needed
revision. Sigbjarnarson (1982) argued a similar
case. He suggested that the Weichselian in Ice-
land was characterized by many active ice centres
and relatively small ice thickness. Sigbjarnarson
pointed out that the physiography of the Hafnar-
fjall-Skardsheidi and Mount Akrafjall is more
characteristic for cirque and valley glaciation
124 JÖKULL 34. ÁR