Jökull - 01.12.1999, Page 12

of relative sea-level fall (Fig. 6). A palaeogeographical
reconstraction of the situation at 10,800 BP is present-
ed in Fig. 7.
10,600-9900 BP
Complete sediment records of this episode are pre-
sent in the two most elevated lakes, i.e. Lake Torfa-
dalsvatn and Lake Hraunsvatn, and sediments repre-
senting its later part were recorded in Lake Kollusáturs-
vatn and Lake Neðstavatn (Rundgren et al., 1997). The
transition to RPAZ Skagi-3 (Fig. 5) is marked by a dra-
matic drop in concentration and influx values of terres-
trial pollen, most clearly in Lake Torfadalsvatn (Rund-
gren, 1995; Rundgren et al., 1997). Very few pollen of
shrabs and dwarf shrabs were recorded in the period
10,600-9900 BP, but there are indications of a relative-
ly diverse herb flora (Rundgren, 1995; Rundgren and
Ingólfsson, 1999), the most important taxa being
Capsella bursa-pastoris type, Saxifraga, Chenopodi-
aceae and Caryophyllaceae. Grasses dominated the
vegetation, which can be described as a grass tundra,
and plant cover was sparse compared with the situation
before 10,600 BP. Low lake productivity and cold cli-
matic conditions are suggested by very low Pediastrum
concentration values and organic carbon content, and
the coastal waters were probably extensively covered
by sea-ice during this episode (Rundgren, 1995), which
is believed to represent the Younger Dryas cold event.
Fig. 7. Palaeogeographical map of northernmost Skagi at 10,800 BP with inferred terrestrial vegetation and sea-ice conditions.
T=Torfadalsvatn; H=Hraunsvatn; G=Geitakarlsvötn; K=Kollusátursvatn; N=Neðstavatn; 0=Open section; A=raised beach
ridge at 65 m a.s.l. - Kort afnyrsta hluta Skaga eins og hann hefur litið útfyrir 10.800 BP. Gróðurfar og hafísástand er einnig
sýnt. T-Torfadalsvatn; H=Hraunsvatn; G=Geitakarlsvötn; K=Kollusátursvatn; N=Neðstavatn; 0=Opnur; A= Fornar strand-
línur við 65 m y.s.
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JOKULL, No. 47, 1999