Jökull - 01.12.1985, Blaðsíða 11

Late Quaternary Geology and Glacial History
of Hornstrandir, Northwest Iceland:
A Reconnaissance Study
CHRISTIAN HJORT and ÓLAFUR INGÓLFSSON
University of Lund,
Department of Quaternary Geology,
Sölvegatan 13,
S-223 62 Lund,
Sweden.
HREGGVIÐUR NORÐDAHL,
Science Institute
University of Iceland,
Dunhaga 3,
ÍS — 107 Reykjavík,
Iceland.
ABSTRACT
The northern part of the northwest (Vestfirdir) penin-
sula of Iceland is a basalt plateau dissected by fjords and
rather short, glacially eroded valleys. Its northern coast is
called Hornstrandir. Its Quaternary geology was recon-
noitered by the authors in 1982 and 1983.
No signs of glacial erosion or deposition were found
on the high (400—500 m) plateaux and it is therefore
concluded that these were not inundated by actively
eroding glaciers, at least not during the last (Weichselian)
glaciation. Using altitudes of glacially unaffected
plateaux as a measure of the absolute maximum thick-
ness of the outlet glaciers, their maximum horizontal
extent can be approximated. It is then found that the
glaciers could only have reached about halfway to the
edge of the shelf and it is possible that they did not even
reach that far. The time of general deglaciation could not
be absolutely dated, but by analogy with other areas in
Iceland, and around the Northeast Atlantic, it most
probably took place during the latest Weichselian and
earliest Flandrian. The sea then stood 26—15 m higher
than today and at least in some valleys the retreat of the
glaciers was interrupted by a readvance — perhaps an
equivalent to the Younger Dryas readvance elsewhere.
The equilibrium line altitude (ELA) at the end of the
Weichselian was around or below the present 150 m
level. A heavy influx of basaltic tephra, the Haelavík
tephra, took place shortly after deglaciation.
During the Little Ice Age glaciers were re-established
in 7—10 cirques on northern Hornstrandir. The ELA in
these cirques varied with exposure between 300 and 500
m, and some glaciers descended as much as to 150 m
below their basin-floor altitudes. Lichenometric studies
at one site indicate that the Little Ice Age glacial maxi-
mum was reached around 1860 AD, perhaps a little
earlier. The retreat, at that place, was largely finished by
1920, when the glacier had almost disappeared. Today
glaciers are found in only four cirques, but small firns
exist on some high plateaux and mountain ridges.
INTRODUCTION
Hornstrandir is the northernmost part of the north-
west, Vestfirdir peninsula of Iceland (Fig. 1), and is
here defined as the coastal area from Ritur eastwards to
Hornbjargsviti (Fig. 2).
Little has been known about the Quaternary geology
and glacial history of Hornstrandir. Scattered refer-
ences to glacial deposits and striae in the area can be
found in the literature, but detailed stratigraphical and
morphological information has been lacking. This paper
attempts to fill some of the gaps. It is based on two short
reconnaissances of the area, combined with extensive
air-photo interpretation and a re-examination of the
scattered data available in the geological literature.
During one week in July 1982 CH and HN studied the
Adalvík-Rekavík area in the west (Fig. 2), and during
JÖKULL 35. ÁR 9