Jökull - 01.01.2005, Page 76

Kate T. Smith and Hreinn Haraldsson
Figure 1. Mýrdalsjökull, the Katla caldera and Eyjafjallajökull. The main outlet glaciers are Kötlujökull (K),
Sléttjökull (SL), Sólheimajökull (S) and Entujökull (E). Sediment sites 1-4 (1: Drumbabót; 2: North Aurasel;
3: Einhyrningsflatir; 4: North Þórsmörk) are described in Table 3. Inset: Location map of Iceland. – Yfirlitskort
af rannsóknarsvæðinu. Sýnatökustöðum 1–4 er lýst í Töflu 3.
the existence and impact of an important, relatively
recent, smaller scale Katla flood to the west.
Drumbabót in the Fljótshlíð area in the Markar-
fljót sandur plain is a key site in the westward-flowing
Katla jökulhlaup story, indicating that not only have
major floods flowed down this route from sources up-
valley, north of the popular wooded area of Þórsmörk,
but that a hundred or so years before the Norse settle-
ment of Iceland (landnám) a medium to small scale
event had a major impact on the landscape. The
’Drumbabót flood’ swamped and killed an extensive
mature birch wood in the Markarfljót lowlands. This
paper describes these buried trees, and presents new
data on their age and the sediments in which they are
found. We place this in the context of earlier studies in
the area and assess the implications for understanding
the palaeo-environment and flood record of the Mark-
arfljót valley. We present two new radiocarbon dates
(from Smith 2004) and also discuss a number of pub-
lished dates. Details of these are summarised in Table
1. We have calibrated all the radiocarbon dates that
we discuss using OxCal v.3.10 (Bronk Ramsey 1995,
2001, 2005) with atmospheric data from Reimer et al.
(2004) and present calibrated ages calculated at 95.4%
confidence levels.
Past studies in Landeyjar and the Drumbabót
trees
Around 1990 large-scale storms in the northernMark-
arfljót sandur area eroded extensive areas of the un-
vegetated sand deposits which make up the sandur
plain at Drumbabót, an abandoned farm site just south
of the rich agricultural area of Fljótshlíð (Figures 1
and 2), exposing mature birch tree trunks which pro-
truded about 0.5 m above the sandur surface and had
hitherto been buried. Changes in smaller branches of
the Þverá river, also around this time, caused river
bank erosion and gave access to the sediment layers
in which the trees were rooted. Farmers in the area
first discovered these exhumed trees. Markús Run-
ólfsson (of Langagerði) contacted one of the authors,
76 JÖKULL No. 55