Fróðskaparrit - 01.01.1998, Side 255

ELDRI HOLOSENAR RANNSÓKNIR ÚR SAKSUNARDALI
OG UPPRUNIN TIL TAÐ FØROYSKA BIOTA
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Saksunardalur
The Saksunarvatn ash was first reported
from the palaeolake site of Hoydalar,
Streymoy by Waagstein and Jóhansen in
1968. In 1972, Jóhansen was able to obtain
a long core from the lake Saksunarvatn, to-
wards the north west end of the through
valley from Hvalvik to Saksun in northern
Stremoy (Fig. 1). At a depth centred around
30 m, the same tephra horizon, in this case
some 0.45 m in thickness and not the (0.01
m as at Hoydalur, was noted (Jóhansen,
1978; Mangerud et al., 1986). The ash is
now known to be widespread in the North
Atlantic region and has been dated to ca
8930-9060 BP (Birks et al., 1996). Al-
though the ash thickness of 0.45 m clearly
indicates some redeposition into the basin,
it appeared probable that the layer could be
traced into adjacent peat deposits and used
as an isochrone, in order to obtain a more
extensive macrofossil record. In 1980, two
thin white tephra horizons had been noted
in abandoned peat cuttings south east of the
lake, close to where Persson (1971) had
identified similar ash layers, which he had
been able to ascribe a source in mid-
Holocene eruptions of the volcano Hekla in
Iceland. Resampling by Dugmore (in prep.)
has confirmed the presence of Hekla tephra
layers Hsv and H4 in the Faroes, although it
is unfortunate that the Saksunardalur sam-
piing locality visited in 1980 had been lev-
elled for cultivation by a second visit in
1982.
Exposures in the peat cuttings in 1980
were badly eroded, and the two samples
taken (P1 & P2) came from a section in the
stream bank to the northeast (Fig. 2), where
the exposure could be easily cut back and
cleaned. The excellent preservation of the
insects in this material, led to a return visit
to the valley in 1982, in company with
Jóhansen, to obtain samples from beneath
the lower Hekla ash down to the underlying
bedrock, close to the location where Pers-
son had obtained his tephra samples. Un-
like the disturbed stratigraphy of the 1980
locality, this site, although cut over for peat,
had 0.5 m of peat down to the underlying
bedrock, and a tephra horizon at the base
was tentatively identified in the field as the
Fig. 2. Sectionfor insect remains in Saksunardalur
(1985).
Mynd 2. Partar av Saksunardali, har skordýraleivdir
eru (1985).