Jökull - 01.12.1978, Page 14

Fig. 12. Map and actions showing the fluvioglacial valley train in Austurdalur. (Compare
Fig. 10). — Mynd 12. Kort, langsniö ogþversnið af jökulársetsfyllingu í Austurdal. (Sbr. mynd 10).
have been local, as no end moraines or other
ice-contact features have been found in
Vesturdalur or at other places which could be
correlated with an ice front at Abær. A
threshold just downstream of Abær may have
facilitated such a local stillstand.
ICE WEDGE CASTS, THEIR CLIMATIC
INDICATION AND POSSIBLE AGE
Casts of some very well developed ice wedges
were found in a gravel pit at Vatnsá about 4
km to the south of Vindheimamelar (for
location see Fig. 9). Fig. 13 shows a cross sec-
tion through the pit. At the bottom of the
profile a hard layer of horizontally layered silt
and sand is overlain by an up to 3 m thick
layer of fluvial sand and gravel of much finer
texture than the fluvioglacial stony-bouldery
sediments in the vicinity. The silty-sandy
sendiments at the bottom of the profile are
thought to have been deposited in a water
filled kettle, which was later gradually filled
by the river deposits. Later, ice wedges formed
in the gravel. They extended down to the fine
grained lacustrine sediments. Layers in the
material between the ice wedges are bent
down near the wedges. The material filling the
wedges is coarser than the bulk of the deposit,
but not so coarsely grained as the surrounding
fluvioglacial sediments. In the lower parts of
the ice wedge casts the material is more like
the undisturbed sediments between the casts.
The coarse material in the casts is most prob-
ably due to sorting caused by frost heaving
and transport of coarse particles to the edges
12 JÖKULL 28. ÁR