Jökull - 01.12.1990, Page 42

lowlands, four samples were collected from sediments
in close relation to the Búði moraine in the area be-
tween Þjórsá and Stóra-Laxá in Hreppar (Fig. 8). Two
samples from a position below the moraine yielded
ages of 9,995 ± 90 B.P. (Lu-2403) and 9,855 ± 90
B.P.(Lu-2404), a sample from within the moraine it-
self provided an age of 9,745 ± 140 B.P. (Lu-2401)
and a sample taken above the moraine showed an age
of 9,595 ± 160 B.P. (Lu-2402) (Hjartarson and Ing-
ólfsson, 1988). The stratigraphical and chronolog-
ical evidence suggests that at least this part of the
Búði moraine was formed at about 9,670 B.P. (be-
tween 9,745 ± 140 B.P. and 9,595 ± 160 B.P.), i.e. in
Preboreal time. Furthermore, three 14C dated samples
from the westem, formerly submarine part of the huge
raised Rangárvellir sandur area, formed proximally to
the southeastem part of the Búði moraine, indicate
that it was formed between 10,015 ± 90 B.P. (Lu-
2406) and 9,505 ± 90 B.P. (Lu-2598), i.e. also in
Preboreal time (Hjartarson and Ingólfsson, 1988).
An important result of the studies by Hjartarson
and Ingólfsson is, that South Iceland was subjected
to a much heavier Younger Dryas glaciation than was
formerly suggested by the DAD-model. According
to Hjartarson and Ingólfsson (1988) relative sea-level
was above the 60-75 m level both prior and subsequent
to the glacier advance which formed the Búði moraine
between Þjórsá and Stóra-Laxá. Kjartansson (1943)
concluded that the advance coincided with formation
of the marine limit at 110 m a.s.l., which consequently
should date from the Preboreal Chronozone.
SOUTHWEST ICELAND
The Fossvogur beds in Reykjavík (Fig. 9) are gen-
erally considered to have been deposited during the
last (Eemian) interglacial (Th. Einarsson, 1968). The
sequence begins with a lodgement tillite on top of stri-
ated bedrock surface. Erosional unconformities and
fluvial, marine and debris-flow sediments above the
tillite indicate phases of sea-level changes which may
have been accompanied by renewed glaciation of the
area. Finally a lodgement till was deposited indicat-
ing the last glacial episode in Reykjavík, which was
followed by deposition of sand and gravel from the fi-
nal deglaciation of the area (Geirsdóttir and Eiríksson,
Figure 9. Late Weichselian and early Holocene
end-moraines and marine-limit features in South-
west Iceland. Legend: 1) 14C dates. 2) Raised
marginal delta. 3) Raised beaches. — Jökulgarð-
ar og sjávarborðsmenjar frá síðjökultíma og upphafi
nútíma á Suðvesturlandi. Tákn: 1) Geislakolsaldurs-
ákvarðanir. 2)Forn jaðaróseyri. 3) Fornfjörumörk.
1990). Measurements of aminoacid racemization in
the lowestfacies sequence of the Fossvogurbeds have
yielded alle/Ue ratios ranging from 0.16 to 0.58, in-
dicating Eemian or pre-Eemian age (Eiríksson et al.,
1990).
A conventional 14C date from the Fossvogur beds
in Nauthólsvík yielded an Allerod age of 11,165 ±
100 B.P. (Lu-2599) (Hjartarson, 1987). A series of
AMS 14C dates from Nauthólsvíkhave produced ages
ranging between 11,435 ± 150 B.P. (AAR-2C) and
10,765 ± 120 B.P. (AAR-8) (Andersen et al, 1989).
According to Hjartarson (1989), the marine sediments
in Fossvogur are overlain by a tillite, which he corre-
lated with a Younger Dryas glacier advance. This indi-
cates, that the Reykjavík area was covered by glaciers
in Younger Dryas time. Hjartarson (1989) suggested
that the area was finally deglaciated close to 9,815 ±
150 B.P. (AAR-3B) and that relative sea-level reached
the marine limit in Reykjavík at 40-45 m a.s.l. at the
same time, i.e. in early Preboreal times (Fig. 9).
At the time of maximum elevation of relative sea-
level in the Reykjavík area, a large ice-contact delta
was formed close to the 55-60 m level at the mouth
of Mosfellsdalur northeast of Reykjavík when a re-
40 JÖKULL, No. 40, 1990