Jökull - 01.01.2016, Blaðsíða 51

Reviewed research article
Geomorphological and sedimentological records of glacial
events in the northern part of the marginal zone of
Tungnaárjökull, Iceland, since the Little Ice Age
Paweł Molewski and Leon Andrzejewski
Department of Geomorphology and Paleogeography of the Quaternary, Faculty of Earth Sciences,
Nicolaus Copernicus University in Toruń, Lwowska 1, 87–100 Toruń, Poland,
corresponding author: molewski@umk.pl
Abstract — We present geomorphological mapping of glacilacustrine and glacifluvial landforms and lithofa-
cies analysis of deposits in the northern part of the marginal zone of Tungnaárjökull as it retreated from its
Little Ice Age (LIA) maximum. This is the first time that this type of study has been conducted in the marginal
zone of Tungnaárjökull. Landforms identified included preserved shorelines, small wave-cut platforms, fossil
deltas and a kame terrace, all associated with ice-dammed lakes. Lake, delta and kame depositional environ-
ments were interpreted on the basis of sedimentological analysis. Ice-dammed lakes developed in the northern
part of the forefield as a result of Tungnaárjökull damming the outflow of meltwater between its snout and the
Jökulgrindur volcanic ridge. Based on historical maps and aerial photographs the damming of meltwater was
probably associated with the 1945 surge.
INTRODUCTION
Tungnaárjökull is one of several outlet glaciers drain-
ing the western part of the Vatnajökull ice cap in
SE Iceland (Figure 1A). It is located between 64◦15’
and 64◦24’ north latitude, between Skaftárjökull in
the south and Sylgjujökull in the north (Figure 1B).
The marginal zone of Tungnaárjökull covers the
area between its maximum extent during the Little
Ice Age (LIA) and its current edge. The indicated
marginal zone is about 25 km long and ranges in
width from approximately 1.2 km in the northern
part to 2.5 km in the central and southern parts of
its forefield (Molewski, 2005; Evans et al., 2009).
Beyond it are extensive outwash plains of various
ages. The topography of the volcanic bedrock and
forefield of Tungnaárjökull fundamentally determine
the spread and dynamics of the glacier snout (An-
drzejewski and Molewski, 2000; Andrzejewski, 2002;
Evans et al., 2009). A pattern of parallel, Upper Pleis-
tocene northeast–southwest volcanic ridges are visi-
ble both in the relief of the forefield of the glacier
and in the morphology of its surface (Figure 1B
and 1C). In the northern part of the Tungnaárjök-
ull forefield, at a distance of approximately 1.5 km
from its snout and running parallel to this margin, is
the Jökulgrindur volcanic ridge of maximum height
about 940 m a.s.l. (above sea level), limiting the west-
ward spreading of the glacier’s snout. In the central
and southern parts of the glacier’s forefield, the vol-
canic ridges are oblique or perpendicular to its snout
which has a significant influence on the local dynam-
ics of ice masses and the distribution of meltwaters
on the forefield, creating the diverse glacial, glaciflu-
vial and glacilacustrine landforms of Tungnaárjök-
ull’s marginal zone (Andrzejewski, 2002; Evans et al.,
2009).
JÖKULL No. 66, 2016 51