Jökull - 01.12.1990, Síða 53

Early Holocene deglaciation in Central Iceland
Ingibjörg Kaldal and Skúli Víkingsson
Orkustofnun
Grensásvegi 9,108 Reykjavík
ABSTRACT
The deglaciation of Central Iceland was charac-
terized by repeated readvances of several ice lobes
leaving end moraines, fluted moraine and otherfea-
tures depicting the glacierfronts at different times. The
readvances are interpreted as surges of a constantly
retreating glacier but not as an evidence for climatic
changes. Datingsfrom outside the research area indi-
cate that the deglaciation is ofPreboreal age. Glacial
striae and fluted moraine show a gradual change in
'ceflow direction. The oldest ice flow direction indi-
cates an ice divide between North and South Iceland
soniewhere near the present watershed. As the ice di-
tninished, individual culmination areas in the periph-
cry became independent ice caps and the culmination
area of the main ice gradually moved towards south
and southeast. During thefinalphase ofthe deglacia-
tion an ice divide was situated in the area between
Vatnajökull and Mýrdalsjökull and another to the NE
ofVatnajökull.
INTRODUCTION
For several years the authors of this paper have
mapped superficial deposits in certain areas of Central
Iceland, as a part of general geological mapping for
hydropower projects by two institutions, the National
Energy Authority and National Power Company. The
results are presented on special maps of superficial
deposits in scale 1:50.000.
The most prominent deposits on the central high-
lands of Iceland are of glacial origin, particularly from
the deglaciation of the Weichselian ice sheet. For this
kind of mapping a thorough knowledge of the direc-
tion of glacial movement is essential. For the history
Figure 1: Key map. —Staðsetningarkort.
of the deglaciation, mapping of glacial landforms such
as glacial striae, fluted moraine, end moraines and es-
kers is of greatest importance. Glacial movement is
indicated by striae and fluted moraine, and eskers give
information about runoff pattern. End moraines indi-
cate the position of the glacier margin at the time of
their formation. The image of glacier snouts is often
complemented by diverging flutes, ice contact sandur
plains and termination of eskers.
Gradually a considerable amount of data relating
to the direction of glacier movement have been col-
lected and computerized. They are presented here on
several local maps (Fig. 1). Altogether they give a
good overview of the deglaciation of Central Iceland.
No absolute datings are available from the area,
but the time period within which the deglaciation took
place is defined by datings from outside the research
area.
i
JÖKULL, No. 40, 1990 51