Jökull - 01.12.1999, Blaðsíða 89

ever, they are mainly encountered on slightly higher
gravel banks (level II: Figure 1) which formed during
the last phases of the catastrophic 1918 jökulhlaup but
has significantly fewer kettles than the level VI kettle
field.
CONCLUSIONS
(1) Geomorphological analyses of 16 kettles limited
to a confined region of the Höfðabrekkujökull fore-
field show that they originate in sediments formed
during the declining phase of the 1918 jökulhlaup.
The kettle region, located on levels VI and Vla, lacks
various forms which are common on the higher sandur
plain (level II, which formed during the main phase of
the flood) such as rims and gravel, diamicton, moraine
and boulder mounds.
(2) Morphological analyses indicate that five kettles
(no. 7, 10, 12, 14, 17) are probably linked with the
degradation of ice deposited on a secondary whereas
four kettles have characteristics closer to the deposi-
tion of ice in situ. The evaluation of kettle shape on
the basis of their axes ratios indicates the predomi-
nance of oval kettles, a total of ten, along with three
elliptical-basinic kettle-holes.
(3) The kettles are underlain by moraine material
released by melting of the glacier ice and con-
tain sedimentary fillings made up of three lithofa-
cies types, out-melting-denudative facies, denudative-
deformative facies, as well as still-water or weak-
current fluvioglacial lithofacies set.
(4) Whereas kettle 10 is classed as normal kettle
16 has a rimmed-normal form with a more complex
structure and morphogenesis, with thicker side de-
posits, rims. The rim development occurs in stages
and is poligenetic.
(5) The width of the sandur sediment subsidence is
almost twice as large around a normal kettle than a
rimmed-normal kettle. Melting icebergs which nor-
mal kettles fromed around were probably flat which
facilitated their covering by fluvioglacial deposits. On
the other hand, rimmed-normal kettles or rimmed ket-
tles described by Maizels (1992) on the higher level
(II), were formed by the melting of thicker and more
isometric blocks of ice.
ACKNOWLEDGEMENTS
This work was carried out within framework of the
KBN grant No. 6P04E 001 11 during the international
programme “Monitoring of Natural Land Surface
Change in Iceland Using ERS-l/ERS-2 and Other Re-
mote Sensing Systems” (1995-97) ESA Project ERS
AO. 2D 116. We are grateful to our Icelandic, Ger-
man, Austrian and Polish friends and colleagues for
their support during the field work in Iceland and
would in particular like to thank Prof. dr hab. Ed-
ward Wisniewski, the leader of our expedition group,
for his critical review of the manuscript and helpful
comments.
ÁGRIP
Setmyndunarrannsóknir á sextán jökulkerjum á ofan-
verðum Mýrdalssandi sýna að kerin mynduðust í kjöl-
far tiltölulega stórs jökulhlaups. Setgerð kerjanna
leiðir ekki í ljós hvort þau mynduðust við bráðnun
jökulíss eða dauðíss, þ.e. hvort ísjakarnir brotnuðu frá
jöklinum í hlaupinu eða bárust úr jökulgörðum út á
sandinn.
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