Jökull - 01.12.1990, Blaðsíða 29

Late Weichselian and
Early Holocene deglaciation
history of Iceland
Hreggviður Norðdahl
Science Institute, University oflceland
Reykjavik, Iceland
abstract
During approximately 100 years of deglaciation
studies in Iceland Late Weichselian deglaciation mod-
els have developed from the earliest models of unin-
terrupted continuous deglaciation to single advance
deglaciation (SAD) and double advance deglaciation
(DAD) models, andfinally towards the present multi
advance deglaciation (MAD) model.
The MAD-model contains two widely recognized
advances ofthe Icelandic inland ice sheet in Late We-
tchselian and EarlyHolocene times, which culminated
at about 9,700 and 10,600 B.P., i.e. during the Pre-
boreal and Younger Dryas Chronozones. The MAD-
model also comprises two advances of the inland ice
sheet that have only been recognized at one locality
each, where the younger advance culminated at about
11,800 B.P. in West Iceland and the older one at about
12,700 B.P. in Northeast Iceland, i.e. during the Older
Dryas and Bplling Chronozones, respectively.
The MAD-model also accounts for markedly
greater extent of the lcelandic inland ice sheet dur-
lng the Preboreal and the Younger Dryas advances
than was proposed by the preceding SAD and DAD-
models. The extent of the inland ice sheet during the
Older Dryas and the B0lling advances is as yet un-
known.
INTRODUCTION
Tahe main purpose of this paper is to describe our
Present state of knowledge conceming the Late We-
ichselian deglaciation history of Iceland and to out-
line the models of deglaciation, which have been de-
veloped during the last 100 years of deglaciation re-
search in Iceland. This development has been from
a simple model of continuous deglaciation towards
a more complicated model of repeated stadials and
interstadials. End-moraines and end-moraine com-
plexes formed by advancing glaciers during the Late
Weichselian deglaciation of Iceland are the main sub-
ject of this paper. On land, these features are found
below the 100 m contour line, in a zone which is fairly
broad in South and West Iceland but relatively narrow
in other parts of the country. The review of the Late
Weichselian deglaciation history of Iceland given here
is not a comprehensive bibliographical review of the
research history as it only accounts for selected refer-
ences conceming the most important contributions to
Late Weichselian studies in Iceland.
End-moraines and end-moraine complexes in the
zone between present sea-level and the 100 m level
were formed by glaciers, that advanced in response
to Late Weichselian and early Holocene climatic de-
teriorations. During the deglaciation of the interior
parts of Iceland (above the 100 m level), topography
and glacier surges are thought to have played a greater
role in stagnation and readvances of glaciers than cli-
matological factors such as temperature and precipi-
tation (Kaldal and Víkingsson, 1991). Changes in the
position of relative sea-level have been coupled with
changes in the extent of the inland ice sheet. Glacier
readvance was usually accompanied by a transgression
JÖKULL, No. 40, 1990 27