Jökull - 01.12.1984, Page 125

vertical section of the Melasveit and Leirársveit
strata (Fig. 4).
Sea level changes and chronology
Based on the works of Thoroddsen (1901,
1906) and Bárdarson (1923) a marine limit at 80—
100 m above present sea level is often postulated
for the northern part of the Borgarfjördur region,
and at 60—70 m a. s. 1. for its southern part
(Áskelsson 1934, Thorkelsson 1935, Th. Einars-
son 1961, 1963, 1964, 1968). Recent surveys by
Sœmundsson and Einarsson (1980) and Ing-
ólfsson (1981) have confirmed raised beaches at
60-70 m a. s. 1. in the area south of Hafnarf-
jall-Skardsheidi. Surveys by Ashwell (1967, 1975)
and Torfason (1974) suggest the existence of
marine terraces and outwash plains at 65—70 m
a. s. 1. in the Andakíll-Skorradalur area. Conspi-
cuous raised beaches at 40—50 m a. s. 1., first
described by Bárdarson (1923), have also been
recognized by later workers (Áskelsson 1942,
Thorarinsson et al. 1959, Torfason 1974, Ashwell
1975, Ingólfsson 1981).
E.H. De Geer (1928) was first to recognize the
Borgarfjördur area as an optimal area for
geochronological studies in Iceland. She sug-
gested that the laminated clays described by
Bárdarson (1923) could possibly be dated by
teleconnections with Swedish varve curves. She
drew attention to the possibility of thus estab-
lishing a chronological frame for the formation of
the terminal moraines Bárdarson described in the
tributary valleys of Borgarfjördur. E.H. De Geer
also proposed that the different stages of land
upheaval could be dated in this way. But the
question of chronology remained unsolved for
the years to come.
Bárdarson (1923) postulated that the transgres-
sion of the sea to the marine limit in the Borgar-
fjördur region had occurred after the glaciers had
retreated from the region. He was supported in
this view by Áskelsson (1934) who rather
favoured Postglacial age for the maximum trans-
gression. Kjartansson (1940, 1943) suggested that
his Búdi-stage occurred after or during the max-
imum transgression in South Iceland, and thus
established a Late Weichselian age for this event.
The Búdi-stage in Iceland has been correlated
with the Salpaussellká moraines in Finland, the
Ra moraines in Norway and the Middle Swedish
moraines (Kjartansson 1943). Th. Einarsson
(1967, 1968, 1973, 1979) correlated the Búdi-
stage with the Younger Dryas in Scandinavia.
Table 1. Radiocarbon dates of marine molluscs collected from the lower part of the Borgarfjördur
region.
Tafla 1. Geislakolsaldur fornskelja úr neðri hluta Borgarfjarðarhéraðs.
Location No. (Fig- 1) 1 2 3 4 5 6
Site name Staður Stóri- Sandhóll Andakílsár- virkjun Hreppur Árdalur Grjóteyri Melar
Height of shell
strata above sea level, m Hœð yfir sjó 114-135 16-24 18-23 25-30 15-21 5
14C date, Years B.P. Geislakolsaldur 12.270±150 12.240±200 12.100±250 12.100±150 12.800±220 12.290±160
Reference no
of date 1-1824 1-1825 S-289 S-290 S-291 U-641
Samples no. 1—5 from Ashwell (1975). Sample no. 6 from Th. Einarsson in Olsson et al. (1969). All
samples are referred to 0.95 NBS oxalic acid standard, using the value of 5570 years for the half life of
C14. The base year is 1950. C13/C12 ratios have not been determined, and no corrections have been
made for apparent age of living marine organisms.
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