Jökull - 01.01.2005, Blaðsíða 77

A late Holocene jökulhlaup, Markarfljót, Iceland: nature and impacts
H. Haraldsson, who first studied the site in 1992 and
presented discussions of these findings in Haraldsson
(1993).
Eggertsson et al. (2004) have carried out den-
drochronological work on the Drumbabót trees which
indicates that the trees died en masse and that they
reached 70–100 years old. They state that the width of
the tree rings indicate a similar summer temperature to
that recorded in southern Iceland between 1930–1940,
the highest temperatures ever registered in Iceland.
Local folklore mentions buried trees at this loca-
tion (Markús Runólfsson, pers. comm. to HH, 1978),
which is also supported by the site name (drumbur =
tree trunk). Sedimentological studies involving sur-
face analysis and deeper coring experiments were car-
ried out in 1978, prior to the exhumation of the trees,
to try to find tree remains. The only organic deposit
found at this time was discovered at Teigsaurar, about
3 km east of Drumbabót; a 40 cm thick layer of silty
sediments containing remains of plants and birch trees
with trunks up to 10 cm in diameter, covered with
roughly 3 metres of sand and fine gravel. Haraldsson
(1981) radiocarbon dated a sample from the middle of
this layer to 1485±65 14C yr BP (U-2807; calibrates
to 1520–1290 cal BP). In many profiles in the coastal
plain of Landeyjar where the Markarfljót river and
sandur reaches the sea, Haraldsson (1981; 43) found
a horizon of fine sand at a similar stratigraphic level
in different localities, usually close to the former river
channels in the area. Near the farm Hólmar, in south
east Landeyjar, peat directly below this sand layer was
dated to 1350±65 14C yr BP (U-4298; calibrates to
1390–1130 cal BP).
Figure 2. a) Partially exposed birch tree stumps in the
eroded flood deposit at Drumbabót. b) Tree trunk
found lying horizontally within the deposits and in-
situ tree stump exposed in riverbank section. c) In-situ
birch tree stump within the flood deposit at Drumba-
bót. Bark dated to 1230±35 14 C yr BP (AA-48027).
– a) Stubbar af birkitrjám standa að hluta til uppúr
flóðaseti sem rofist hefur ofanaf við Drumbabót. b)
Trjástofn sem fannst láréttur í setinu og trjástubbur í
lífsstöðu í árbakkanum. c) Birkitrjástubbur í lífsstöðu
í flóðaseti við Drumbabót. Börkurinn hefur verið ald-
ursgreindur, 1230± 35 C14 ár.
a)
b)
c)
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