Jökull - 01.01.2005, Blaðsíða 152

Leó Kristjánsson
on dikes and faults, zeolites, tectonic tilts, etc., and
most other studies on such features in Iceland.
Walker’s admirable research on central-volcano
complexes was a key ingredient in the new under-
standing of the geology of Iceland. Although the exis-
tence of such features here had been implied by some
earlier geologists (e.g. G.W. Tyrrell, see Kristjánsson,
1995), Walker was the first to demonstrate their exis-
tence and describe their main characteristics.
The Icelandic scientists Trausti Einarsson and
Thorbjörn Sigurgeirsson had been studying magnetic
remanence directions in Icelandic basalts since 1953,
and Einarsson was applying them to extensive strati-
graphic mapping in Southwestern and Eastern Ice-
land. Sigurgeirsson had contacts with P.M.S. Black-
ett of Imperial College who had become interested
in planetary magnetism and the magnetic properties
of rocks in connection with his Nobel prize-winning
research on cosmic rays. Sigurgeirsson presumably
learned about Walker’s research in Eastern Iceland as
soon as it began, through these contacts or the Na-
tional Research Council of which he was director un-
til 1957. Einarsson (1960) wrote a very favorable ac-
count of Walker’s mapping work in Reyðarfjörður.
1961–1965
GeorgeWalker received grants from the Science Fund
of Iceland in 1961–1963; these grants were probably
very small in proportion to total costs of a field project
like Walker’s, but it was a rare distinction for a foreign
scientist.
One of Walker’s major contributions to improved
understanding of the stratigraphy and tectonics of Ice-
land was his realization that the country had been
formed by processes of crustal spreading. Walker and
G. Böðvarsson, who was then at the State Electric-
ity Authority, collaborated on an important paper on
this matter (Böðvarsson and Walker, 1964). It was
submitted just before the Vine and Matthews (1963)
hypothesis on generation of the ocean floor appeared
in print, and I expect independently of it. Some Ice-
landic geoscientists were sceptical of the spreading
concept, for various reasons. It might be instructive
to discuss these in detail but I shall only mention a
few here: the traditional belief that Iceland was the
remnant of a continent (supported by the presence of
acidic rocks); its oldest exposed rocks being thought
to be of Eocene or even older age (until 1968); and the
absence of vertical structures like those prominent in
the Vine-Matthews model.
In early 1963, Sigurgeirsson discussed the pos-
sibility of a major sampling project in Iceland dur-
ing a visit to Blackett’s laboratory (see Kristjánsson,
1993). One of Blackett’s former students, R. L. Wil-
son, wrote an application for the funding of such an
expedition which eventually took place in 1964 and
1965. The 1964 sampling began in SW-Iceland in
June, in profiles mapped by T. Einarsson. In the first
days of August the party (Figure 2) set up camp near
Neskaupstaður and began sampling in 15 lava profiles
mapped byWalker. He painted a number on each lava,
which greatly aided their correct identification. Addi-
tionally, Walker provided a diagram of each profile,
with geological information and sometimes instruc-
tions regarding access. A complete set of his origi-
nal 1964 drawings, dated between 25 July and 1 Sept.
are in my possession, and one is reproduced here as
Figure 3. They must have been made in his tent or
his Land-Rover, and some were delivered only a day
or two before the sampling of the respective profiles
began. Invariably, they were very well done and cer-
tainly served their purpose. In July of 1965 Walker
mapped another six profiles along the Norðurdalur
valley of Fljótsdalur, for sampling by an expedition
of smaller size.
1966–1977
Although Walker’s main research emphasis shifted
away from Iceland after 1965, he visited the country
a number of times later. The instances which I recall
include the 1974 conference on “The geodynamics of
Iceland and the North Atlantic area” where he pre-
sentedmajor new results and ideas about the country’s
geology and also about its deeper crustal structure.
Subsequently, he published a paper (Walker, 1975) on
areas in Iceland where the lower crust had been ex-
posed by deep erosion, relating his findings to stud-
ies by others of ophiolites such as Troodos in Cyprus
which had by then been accepted to represent slices of
ocean crust and uppermost mantle rocks.
The 1964–1965 paleomagnetic sampling expedi-
tion in Iceland had been by far the largest single effort
152 JÖKULL No. 55, 2005