Jökull - 01.12.1999, Blaðsíða 6

Ingólfsson, 1999), and the purpose of the present
paper is to present a summary of the results from the
Skagi project.
THE STUDY AREA
The Skagi peninsula is situated in the valley and
fjord landscape of northern Iceland, between the
Húnaflói and Skagafjörður fjords (Fig. 2). In its south-
ern part, the peninsula is mountainous with peaks
reaching 1000 metres, while the northem part is a gen-
tly undulating lowland area carrying many lakes and
reaching c. 250 m a.s.l. (Fig. 3). The bedrock in the
northern part of the peninsula consists mainly of
Upper Pliocene and Lower Pleistocene basic and inter-
mediate extrusive rocks, 3.1-0.7 Myr in age, while
Upper Tertiary (older than 3.1 Myr) basic and interme-
diate extrusive rocks dominate in the southern part of
the peninsula (Jóhannesson and Sæmundsson, 1989).
Early deglaciation of the northernmost part of the
Skagi peninsula is suggested by Skagi’s position be-
tween two major fjords and the direction of glacial
striae (Einarsson, 1967, 1994), which indicate that the
last inland ice sheet was drained towards the shelf on
each side of the peninsula. The dating results present-
ed by Björck et al. (1992) show that this part of Ice-
land was free from ice by c. 11,300 BP, but this is only
a minimum age for the deglaciation. A prominent fea-
ture in the coastal areas of northernmost Skagi is a se-
ries of pronounced raised beach ridges (Moriwaki,
1990; Fig. 2), indicating that the area has experienced
marked sea-level variations since deglaciation.
Mean annual temperature at Hraun, in the north-
eastern corner of Skagi, is 2.5°C. Mean January tem-
perature is -1.8°C, and mean July temperature 8.2°C.
Annual precipitation is around 475 mm. Due to the
harsh climate on northemmost Skagi, alpine vegeta-
tion reaches down to sea level. Dwarf-shmb heaths
are dominant (Fig. 4) and alternate with fell-fields,
herb and grass tundra, and Carex-dominated fens.
Empetrum nigrum, Betula nana, Salix herbacea and
Dryas octopetala are the most abundant dwarf-shmb
species, but also Salix callicarpea, S. phylicifolia,
Vaccinium myrtillus and V. uliginosum occur within
the area. Juniperus communis is rare and occurs only
as prostrate forms, while Betula pubescens ssp. tortu-
osa is absent from northernmost Skagi. The present
vegetation is, as in most parts of Iceland, not entirely
natural due to grazing by sheep and horses, which is
likely to have favoured grasses and some herb species
(Einarsson, 1962, 1994; Hallsdóttir, 1987). In addi-
tion, a few areas, mainly in the coastal lowlands, have
been subjected to draining and cultivation.
Five lake basins, situated at varying elevations
below the highest identified raised beach ridge in the
area (65 m a.s.l.), were selected for the study in order
to enable a detailed reconstmction of relative sea-level
changes (Fig. 2). As regression below present sea level
has been shown to have occurred prior to 9000 BP in
other parts of Iceland (Thorarinsson, 1956; Kjartans-
son et al., 1964; Thors and Helgadóttir, 1991; Ingólfs-
son et al., 1995), sediments deposited up to that time
were collected from all five lakes. Younger sediments
were only sampled in Lake Torfadalsvatn, which was
chosen as the reference site for the reconstruction of
vegetational and climatic changes. The 9000 BP level
was easily located in all lake sequences due to the
presence of the Saksunarvatn ash, dated to c. 9000 BP
(Mangerud et al., 1986; Björck et al., 1992; Birks et
al., 1996), which was recorded as a thick (> 4 cm),
black and silty deposit that was hard to penetrate with
the sampler.
The Saksunarvatn ash was also found in an open
section at c. 1.5 m a.s.l. (Fig. 2), which made it possi-
ble to get a stratigraphic record from an altitude
below the lowest cored lake, close to present sea
level. Consequently, it was possible to test if regres-
sion below present sea level really took place before
9000 BP on northernmost Skagi.
Lake Torfadalsvatn (47 m a.s.l., 0.37 km2, 66°04’N,
20°23’W; Fig. 4)
The lake is situated in a depression in an area
dominated by rocky plateaux. Two minor streams
enter the lake at its southern end, and one of them
drains a small neighbouring lake. The outflow is
small (c. 0.5 m wide) and runs towards the north over
a till threshold. A series of raised beaches have devel-
oped at a lower elevation north of the lake. The lake
shores are mostly gravelly and steep, and dwarf
shrubs dominate the surrounding vegetation. The core
4
JÖKULL, No. 47, 1999