Jökull - 01.12.1985, Page 22

distal part of an alluvial cone or elevated sandur below
one of these cirques (Grasadalur) on the south side of
Rekavíkurvatn, and a similar altitude of the upper
surface of a much dissected glaciofluvial deposit at the
southern end of Rekavíkurvatn, indicate the approxi-
mate base level at the time of deglaciation. It could not
be ascertained whether the Rekavíkurvatn basin con-
tained inactive ice when these sediments were depo-
sited. However, an inactive ice body must have been
left in the small basin (Hálsavatn) east of Rekavíkur-
vatn, or the sediment pile between the two lake basins
could not have been deposited. There are also remnants
of a terminal moraine on the north shore of easternmost
Rekavíkurvatn, deposited by a glacier coming from the
east. On the watershed between the Rekavík valley and
the Látrar lowlands an interlobate drainage pattern
illustrates the separation of the two ice bodies.
We re-examined Thoroddsen’s (1892a) evidence of an
ancient strandline at 63 m above present sea level inside
Rekavík and came to the conclusion that the featuere in
question is a bedrock structure, without any relevance
to ancient sea levels.
No clear indications on the marine limit around
northern Adalvík were found, but the above mentioned
data and the rather diffuse border between abraded and
non-abraded glacial features inland from Látrar places
it somewhere between 15 m and 25 m above present sea
level.
Summary and correlation of the late glacial events
The most complete late glacial sequence is probably
found in Haelavík. Morphological and stratigraphical
features there reveal the following sequence of events:
(1) An initial glacial retreat was followed by (2) the
deposition of marine silt to at least 8 m above present
sea level and (3) by a glacial readvance, whereafter (4)
the final deglaciation took place, when the sea stood
26-27 m higher than today. Deglaciation was (5) fol-
lowed by regression of the sea to or below the present
sea level.
Another fairly complete glacial geological sequence is
revealed in the Stadarvatn valley of southern Adalvík,
where two glacial advances are probably documented.
One interpretation of the geology there suggests a
development similar to that in Haelavík. But the final
deglaciation at Stadarvatn took place when the sea
stood only 15 m higher than today, which indicates a
later deglaciation than in Haelavík, perhaps contempor-
aneously with that of Hlöduvík.
We correlate the lateral terrace at Látrar with the
short lower lateral terrace north of Stadarvatn (zone C
in Fig. 6). The stratigraphy of the Látrar terrace may
suggest a transgression from < 10 m up to 20—25 m
above present sea level, i.e. to a level similar to the
marine limit in Haelavík.
The ELA during some part of the late glacial has
been around or lower than 150 m above present sea
level. This is inferred from the altitude of the low level
cirques which were glaciated at that time. Such are
found in Hornvík, Hlöduvík (Fig. 7) and at southeast-
ern Adalvík, but also at places along the outer coast,
near Ritur and Straumnes. A good example is shown in
Fig. 11.
Dating the full glacial to late glacial sequence
No shell bearing sediments from the full glacial or late
glacial periods were found on Hornstrandir. Probably
most fine grained sediments from that time lie below
present sea level, with the exception of the shell- and
foraminifera-free silt in section 1 at Haelavík. Nor have
we found any other material which could be absolutely
dated, as the gyttja silt in sections 2 and 3 at Haelavík
contains too little organic matter and too few pollen.
Thus the age of the glacial deposits can only be sug-
gested by analogy with other areas.
New interpretations of data from Northeast Green-
land (Funder 1982, 1984, Hjort and Björck 1984) sug-
gest the nonexistence of any extensive Early or Middle
Weichselian glaciation there and tentatively place the
Weichselian maximum around 20.000—18.000 years
BP. Data from Svalbard (Miller 1982) may be inter-
preted in the same way.
Norddahl (1983) suggested that the glacial maximum
in central North Iceland dated from before 18.000-
24.000 BP, but his oldest glacial stages are not neces-
sarily of Weichselian age. In fact, the Weichselian maxi-
mum has never been properly defined or absolutely
dated anywhere in Iceland, so there seems to be no
reason to, initially, suggest any other age for it on
Hornstrandir than the classical 20.000—18.000 BP one,
as proposed for Iceland in general by Tr. Einarsson
(1966) and Th. Einarsson (1973).
The best clue to the age of the final deglaciation, of at
least northern Hornstrandir, is the deposition at or near
present sea level of lacustrine/fluvial sediments which,
although with an erosional discontinuity, follow directly
upon the till in section 3 at Haelavík. These mirror the
regression after the final deglaciation, from the 26 m
level (section 1 at Haelavík) down to present sea level.
From other parts of Iceland we know that already
around 9000 BP the relative sea level had come down to
or below its present level (Thórarinsson 1956, 1964, Th.
Einarsson 1956, 1964, 1968). If applied on Hornstrandir
20 JÖKULL 35. ÁR