Jökull - 01.01.2014, Blaðsíða 2

Leó Kristjánsson
66˚N
50 km
65.5˚N
24˚W 22˚W
Breiðafjörður
Skálavík
Súgandafj.
Önundarfj.
Dýrafj.
Arnarfjörður
Patreksfj.
Tálknafj.
Ísafjarðardjúp
Aðalvík
Fljótavík
TF
TE
Figure 1. Northwest peninsula of Iceland. Colored lines indicate cross-sections from which the polarity columns
in Figure 2 are derived. Box shows location of Figure 3. Black dots mark approximate mid-positions of cen-
tral-volcano complexes (Jóhannesson and Sæmundsson, 2009). Profiles TF and TE (see text) were sampled
by Kristjánsson et al. (2003) and Kristjánsson (2009) respectively. – Vestfirðir. Lituðu línurnar marka samsett
jarðlagasnið á 2. mynd, punktarnir marka miðjur megineldstöðva, og kassi sýnir staðsetningu 3. myndar.
lignite and/or well-preserved impressions of vegeta-
tion. These attracted the attention of scientists al-
ready in the 18th century. The lignite locations of
Northwest-Iceland were by many thought to belong to
a single horizon (Thoroddsen, 1896) signifying a hia-
tus in volcanic activity in the Eocene, or between the
Eocene and the Miocene. Bárðarson (1927, p. 146–
150) who agreed with the view of a single long hiatus,
states that the lava flows below the lignite sediments
have suffered considerably more alteration, tilting and
intrusion by dikes than those above. No detailed stud-
ies have yet been made of the lava pile to establish
whether a significant discontinuity in these aspects ac-
tually occurs at that level. The view of an Eocene age
of the oldest lignites in both Northwest- and East Ice-
land was supported by studies of fossil pollen (Pflug,
1959), and the dominant view of Iceland’s geologi-
cal history in the first half of the 20th century was
one of intermittent (possibly alternating) episodes of
volcanism, erosion, and vertical tectonic movements
(Bárðarson, 1927; Einarsson, 1960).
Research in 1960–1970
Views of the volcanic and tectonic activity at the Mid-
Atlantic Ridge underwent a revolution in the mid- to
late 1960s, with the general acceptance of sea floor
spreading which among other things introduced the
possibility of significant lateral movements of large
areas. The picture of Iceland’s geology was also
changed dramatically, especially due to the research
of G.P.L. Walker and his students and collaborators
(e.g., Walker, 1959; Watkins and Walker, 1977). This
change included recognition of the key role of central-
volcano complexes, and replacement of the older view
of intermittent volcanic and tectonic episodes by a
2 JÖKULL No. 64, 2014