Jökull - 01.12.1982, Page 54

Fig. 1. Geological and topo-
graphical features in the Búr-
fell area. Legend: 1) The
Tungnárhraun lavas. 2) The
Hekla lavas. 3) Outwash
plain. 4) Bedrock of
Pleistocene age.
Mynd 1. Megindrettir jarðfrœði
og landslags umhverfis Búrfell.
Skýringar: 1) Tungnárhraun. 2)
Hekluhraun. 3) Sandur. 4) Berg-
grunnur frá ís'óld.
part of the area, for example in Búrfell and Sáms-
staðamúli south of Skeljafell.
1.2 Hyaloclastites (the so-called Móberg), dat-
ing from the Brunhes normal geomagnetic epoch
(< 700,000 years) and created in subglacial erupt-
ions. They form the mountain ridges in the eastern
part of the area, for example the Sauðafellsalda west
ofHekla.
2. Holoceneformations, which are of four main class-
es:
2.1 Outwash plains formed during the retreat
of the Weichselian ice sheet. Deposits of this kind
are, for example, found within the Trjáviðarlækur
basin.
2v2 Lava flows. As Fig. 1 shows, lavas are wide-
ly distributed in the area. The main bulk of lava
flows, the so-called Tungnárhraun, originated in an
eruptive fissure swarm called the Veiðivötn Volcan-
ic System, 40-50 km ENE of Búrfell (Vilmundardóttir
1977, Jakobsson 1979). One of the Tungnárhraun
lava flows (Þjórsárdalshraun) is found at the west-
ern margin of the Trjáviðarlækur basin. As many as
seven of the Tungnárhraun flows have been found
in the area.
Lavas from Hekla are found at the eastern marg-
50 JÖKULL 32. ÁR