Jökull - 01.12.1990, Blaðsíða 69

Studies in the vegetational history of North Iceland.
A radiocarbon-dated pollen diagram from Flateyjardalur
Margrét Hallsdóttir
Science Institute, University oflceland
Reykjavík, Iceland
abstract
A pollen diagram is presented from the lowest 110
ctn of a 560 cm core from the mire Krosshólsmýri
ln Plateyjardalur. Two radiocarbon dates are used
to estimate the sedimentation rate and to interpo-
late/extrapolate agesfor events in the pollen diagram.
These are 9650 and8740 B.P. Thepollen diagram rep-
resents some 2500 HC-years, including the Late Pre-
boreal, Boreal and Early Atlantic Chronozones and
records the first stages in the local vegetational his-
tory after the deglaciation in early Preboreal.
The first phase recorded in the vegetational devel-
opment is a Salix-Ericales-herb tundrajollowed by a
Betula- Juniperus-/?er/? tundra. After some retreat of
the spreading Betula woodland in the Early Atlantic
Chronozone, the valley seems to become occupied by
a Betulaforest tundra about 7000 B.P.
introduction
Flateyjardalur (dalur = valley) is located on Flat-
eyjarskagi (skagi = peninsula) between the fjords of
Eyjafjörður and Skjálfandi in central North Iceland
(Fig. 1). Morphologically it is an earlier northward
prolongation of Fnjóskadalur, but is now separated
from it by the 200 m high threshold named Flateyjar-
dalsheiði (Norðdahl, 1979). The highest mountains
°n Flateyjarskagi reach some 1200 m, but on the aver-
age they are 700-900 m a.s.l. dissected by two main
valleys, one of them being Flateyjardalur, and several
tributaries.
Today the landscape of Flateyjardalur is charac-
terized by dwarf shrub heath, birch copses and sedge
Figure 1. Map of central North Iceland. Shaded area
is covered by Fig. 2. Black dots are weather stations
given in Table I. — Flateyjardalur og nágrenni.
Jarðfrœðikortið á mynd 2 er af skyggða svœðinu.
Veðurstöðvar, sem taldar eru upp í töflu I, eru sýndar
með svörtum punktum.
JÖKUFL, No. 40, 1990 67