Fróðskaparrit - 01.01.1998, Blaðsíða 206

212
HIGHLAND AEOLIAN DEPOSITS IN THE FAROE ISLANDS
ed aeolian material (Ballantyne and Whit-
tington, 1987).
In the Faroe Islands sediments and or-
ganic materials are seen on ablating snow-
patches in spring and summer (Fig. 5).
Therefore it is very possible that some of
the poorly-sorted aeolian deposits are
niveo-aeolian in origin also here. As the
wind speed in general is strongest in the
winter (Søgaard, 1996), a niveo-aeolian
origin for some of the high-lying wind-
blown deposits is very likely. In the high-
lands most precipitation falls as snow in
winter, enabling snowdrift particularly in
these areas.
Sediment sources
Obviously the sediments of the aeolian de-
posits are the result of weathering of
bedrock and erosion of the glacial sedi-
ments that otherwise cover the landscape.
Since vegetation was first established in the
Faroese landscape in the early Holocene
(Johansen, 1985), primarily free faces and
other high-lying exposed bedrock surfaces
must have been the main sediment source
areas. This could explain the largest occur-
rence of aeolian sheets above coastal free
faces, as these are presumably most pro-
ductive in terms of weathering. Inland free
faces are generally lower and not so steep
as the near vertical coastal cliffs. In vegeta-
tion free areas with active periglacial land-
forms, such as e.g. small-scale sorted poly-
gons and sorted stripes, presumably some
sediment is blown away and therefore en-
able aeolian accumulation in local topo-
graphical lee sites.
Age
As the windblown deposits occur in former
glaciated areas and below periglacial trim-
lines, these are younger than the last glacia-
tion. Some aeolian sheets, however, occur
above trimlines, indicating that they can be
of Weichselian age. The existence of peat
layers below some of the windblown de-
posits indicates a mid to late Holocene age,
as peat layers on the Faroe Islands are pri-
marily known to have accumulated since
the early to mid Holocene (Humlum et al.,
1996).
Luminescence dating of sand grains
from some aeolian deposits has been at-
tempted, despite that the sediments are de-
void of quartz, but does contain feldspars.
So far the luminescence technique has,
however, not been successful because the
luminescence property of the feldspar
grains seems to be too small to be mea-
sured. Presumably ash layers found in parts
of the aeolian deposits, and 14C AMS dat-
ing of macrofossil plant remnants from or-
ganic rich layers in the aeolian deposits
could date parts of the aeolian deposits, just
as pollen stratigraphical investigations
might lead to a closer determination of the
flora at the time of deposition.
Conclusions
For the first time the geomorphology of the
extensive highland aeolian deposits of the
Faroe Islands has been described. They
have been found to be primarily located on
south facing slopes, indicating predomi-
nantly northerly wind directions during
time of deposition. Texturally and morpho-
logically they resemble similar deposits in