Jökull - 01.12.1990, Side 36

Figure 3. Late Weichselian and early Holocene end-moraines, marine-limit features and ice-dammed lakes in
North Iceland. Legend: 1) End-moraines. 2) Ice-dammed lake. 3) Raised deltas. 4) 14C dates. 5) Raised
beaches. 6) Terminal zones. —Jökulgarðar, sjávarborðsmenjar og jökulstífluð lónfrá síðjökultíma og upphafi
nútímaá Norðurlandi. Tákn: 1) Jökulgarður. 2) Jökullón. 3) Fornar óseyrar. 4) Geislakols aldursákvarðanir.
5) F'orn fjörumörk. 6) Oviss lega jökuljaðars.
the Weichselian glaciation when Grímsey, about 40
km off the present coast (Fig. 1), was overridden by
glaciers from the mainland. An intermediate phase
was apparently characterized by climatologically con-
trolled variations in the extent of the main outlet
glaciers in North Iceland. A consequence of variable
glacier extent was, that Dalsmynni and Ljósavatns-
skarð were repeatedly and simultaneously blocked by
glacier tongues from the outlet glaciers in Eyjafjörður
and Bárðardalur. At the same time the northem part
of Fnjóskadalur remained ice-free and at least eight
successive ice-dammed lakes, with their outlets over
the Flateyjardalsheiði threshold (Fig. 3), were formed
in the valley (Norðdahl 1983). Of these eight ice-
dammed lakes the youngest four have left prominent
strandlines along both sides of Fnjóskadalur. A sur-
vey of these strandlines has led to a fairly accurate
reconstruction of the extent of the two youngest ice-
dammed lakes, the Austari-Krókar and Fnjóskadalur
ice-dammed lakes (Fig. 3), which were formed during
the Fornhólar and the Belgsá readvances (Norðdahl,
1983). In both instances the outlet glacier in Eyjafjörð-
ur terminated in a zone south of Hrísey, and the outlet
glacier in Bárðardalur terminated in a zone close to
the present coastline of Skjálfandi (Fig. 3) (Norðdahl,
1982; 1991 ). In Fnjóskadalur the outlet glacier ter-
minated in the southemmost part of the valley (Norð-
dahl, 1983). A third phase includes a readvance of
local valley and cirque glaciers especially in the outer
parts of the elevated peninsulas Tröllaskagi and Flat-
34 JÖKULL, No. 40, 1990