Fróðskaparrit - 01.01.1998, Qupperneq 216

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HUMAN IMPACT AT TJØRNUVÍKIN THE FAROE ISLANDS
Lab no. Site Material dated Author Depth(cm) below surface Age BP Old calibration cal. Years New calibration 1 sigma New calibration mid-point
St-2135 Mýramar bulk sediment Persson 1968; 1971 21-23 900±120 1050 AD 1017-1276 1165 AD
K-1699 Tjørnuvík Calliergon moss Jóhansen 1971; 1985 170-175 880±100 1070 AD 1028-1276 1176 AD
K-1700 Tjømuvík bulk sediment Jóhansen 1971;1985 190-200 1350±100 600 AD 627-779 668 AD
K-1787 Tjømuvík bulk sediment Jóhansen 1971;1985 179-181 1330±100 620 AD 640-786 676 AD
K-1788 Tjørnuvík bulk sediment Jóhansen 1971; 1985 182-184 1300±100 650 AD 654-872 690 AD
TUa-1412 Tjømuvík seeds Hannon 1996; 1997 211.3 211.6 1270±60 675-823 838-861 732 AD
Table 2. Recalibrated bulk radiocarbon datesfrom Tjørnuvík (Jóhansen 1971; 1985) andfrom Mýrarnar
(Persson, 1968; 1971) together with the AMS datefrom the present study.
Talva 2. Endurkalibreraðar kolevni 14-dagfestingar íTjørnuvík (Jóhansen, 197 i; 1985) og á Mýrunum (Persson,
1968; 1971) saman við AMS-dagfestingunum úr hesi rannsókn.
Microtephra
Tephra shards were identified in all sam-
ples with a distinct peak in concentration at
207.4 cm, c. 3.5 cm above the first settle-
ment as inferred from palaeobotanical đata.
Most shards are colourless or weak brown,
but dark brown basaltic shards were also re-
trieved. A sample from this level was cho-
sen for microprobe analysis, as the concen-
tration of tephra was too low in samples
taken closer to the settlement horizon to al-
low geochemical analysis. Two rhyolitic
populations dominate the sample: The larg-
er consists of glass with Si02 content be-
tween 65 and 75 %, and exhibits a low TiO
content (0.09 - 0.47 %) and a low MgO
content (0.03 - 0.58 %) (Table 3). The geo-
chemistry of this tephra shows affínities to
the Hekla volcanic system (cf. Dugmore et
al., 1995). A second subordinate popula-
tion is only defined by three analyses so far.
It has a Si02 content of c. 63 %, and dis-
tinctly higher TiO and MgO contents than
the main population (Table 3). This proba-
bly rules out the Hekla volcanic system as
source area. A single basaltic shard was
analysed which compares well with the
geochemical data in the literature for the
basaltic phase of the Landnám tephra
(Table 4). As we are unable yet, to correlate
the rhyolitic tephra results to known hori-
zons on Iceland, or in Ireland or Scotland,
we propose that the main population found
at Tjørnuvík is called the Tjørnuvík A