Jökull - 31.12.2001, Blaðsíða 19

Reviewed research article
Dating of the Fláajökull moraine ridges SE-Iceland; comparison
of the glaciological, cartographic and lichenometrical data
Maciej D^bski
Laboratory of Sedimentology, Faculty of Geography and Regional Studies,
University ofWarsaw, Krakowskie Przedmiescie 30, 00-927 Warsaw, Poland; mdabski@wp.pl
Abstract - New lichenometric measurements performed on moraine ridges by Fláajökull demonstrate the diffi-
culty in assessing lichen growth rate depending on its periglacial environment and climatic fluctuations. Lichens
measured on the Fláajökull moraines do not match precisely any ofthe previously published growth curves. The
Fláajökull glacier has retreated over 1500 mfrom its maximum position during the Little Ice Age (LIA), the old-
est moraine ridge was abandoned in 1894. The recession was interrupted by longer advances or still-stands
between 1903 and 1925 where moraine ridges II, III and IV were deposited. Ridges V, VI and VII were probably
created in the late Pleistocene and were just overridden in LIA without significant remodelling. During the last
two decades ofthe 20th century the glacier had both advances and still-stands, hence the stoss side of the VI1
moraine ridge has a thick new moraine cover. There is a
of Fláajökull and 20th century climatic fluctuations.
INTRODUCTION
Fláajökull is an outlet glacier from the largest ice mass
in Europe, the Vatnajökull ice-cap and its marginal
zone is at about 50ma.s.l. (Figure 1). The east-
em lobe of Fláajökull has formed easily discernible
moraine ridges (Figure 2) which to the west border
moraines from the Heinabergsjökull and Skálafells-
jökull glaciers. These glaciers and Fláajökull formed
a single piedmont lobe between 1860-1870 (Evans et
al., 1999). Dating of the Fláajökull moraine ridges
was previously undertaken by Dabski et al. (1998), in
order to study the dynamics of the Fláajökull glacier
front recession. This work was also a part of a larger
project conceming periglacial phenomena (Dabski
and Gryglewicz, 1998). The aim of this paper is to
review previous dating of the Fláajökull moraines and
compare thern with new lichenometric data. To ob-
tain optimal results several data sources were used
such as glaciological measurements, a map based on
aerial photographs taken in 1946, aerial photographs
from 1989, historical data and information concerning
neighbouring glaciers.
:lear correlation between the overall rate ofthe retreat
Figure 1. Location of Fláajökull. - Kort afrannsókna-
svœðinu.
METHODS
The data used in this review comprise:
1. Glaciological measurements along the Hólmsár-
garður prolile (Figure 3) undertaken regularly since
1934. They are provided by the Icelandic Glacio-
logical Society and published in Jökull and on the
JÖKULL No. 51 17