Fróðskaparrit - 01.01.1998, Blaðsíða 210

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HUMAN IMPACT AT TJØRNUVÍK IN THE FAROE ISLANDS
Introduction
The divergence between the historical dates
for the earliest settlement in the Faroe Is-
lands (AD 825)(Debes, 1990) and radiocar-
bon dating of the first cereal cultivation
(AD 600-700s) (Jóhansen, 1971; 1985;
Hannon and Hermanns-Auðardóttir, 1996;
Hannon, 1997) has caused intense discus-
sion as to which is the more reliable source
of information. Debate has focused on the
original palaeobotanical studies (Jóhansen,
1971; 1985) and doubts have been raised
about the radiocarbon evidence such as the
inherent inaccuracy of bulk dates (Arge,
1991), and the possibility of a local dilution
of the atmospheric 14C concentration due to
depleted oceanic air masses (Olsson, 1983;
1990) . The reliability of cereal pollen grain
identification has been questioned (Arge,
1991) , and it has been considered surpris-
ing that the fossil insect evidence for early
settlement is not detected from the horizon
in which the first cereals were recorded at
recorded at Tjørnuvík, one of Jóhansens
(1971; 1985) early settlement sites (Buck-
land, 1990).
The recognition of human activity on the
landscape can be problematic, as these is-
lands may have been predominantly tree-
less during the Holocene. However, the po-
tential impact is large because of the fragili-
ty of the ecosystems. In this paper, we de-
fine permanent settlement as meaning
pollen evidence for cereal crop cultivation,
associated with their characteristic suite of
weed species defined by macrofossil re-
mains. As part of a multidisiplinary project
called ‘Settlement and Chronology in the
North Atlantic region’ (Hermanns-Auðar-
dóttir, 1993), high resolution pollen and
macrofossil sampling has been carried out
from a series of sites in order to establish
the settlement horizon using a combinatión
of techniques. Having achieved that, the
next tasks were (1) to extract sufficient ter-
restrial plant macrofossil remains to redate
the settlement horizon using the high reso-
lution AMS radiocarbon techniques now
available, and to compare with previous
dating projects (2) to numerically distin-
guish large wild grass pollen grains from
those of cereals and (3) to see if volcanic
ash was associated with the pollen inferred,
settlement layer.
A distinctive two-coloured volcanic ash
layer originating from the Vatnaoldur fis-
sure in southern Iceland (Zielinski et al.,
1997; Larsen, 1984), which itself is partial-
ly located within the Torfajókull central
volcano, was first described by Thorarins-
son as Vlla+b (Thorarinsson, 1944). It is
often used as a stratigraphic marker
because of its close association with the
time of the first permanent settlements on
Iceland (Hallsdóttir, 1987) and thus has
been named the ‘Landnám' tephra. Tephras
are valuable, synchronous time marker
horizons, and have distinctive chemical
characteristics. If located within a sediment
sequence, they can provide an independent
dating control to the radiocarbon or histor-
ical evidence. The ‘Landnám’ tephra has
been chemically fínger-printed in Iceland
(Hafliðason etal., 1992;Boygle, 1994)and
geochemically identified in the Greenland
Ice Cores where it has been dated in calen-
dar years to AD 871 ± 2 (GRIP)(Gronvold
et ai, 1995) and AD 874 ± 4 (GISP2)