Jökull - 01.12.1982, Blaðsíða 97

Fig. 2. Pen and ink drawing ofj. Hospers, made
by Oddur Björnsson at Háls, N-Iceland in 1950.
Mynd. 2. Pennateikning afjan Hospers ejtir Odd Bjöms-
son.
were taken from scattered outcrops, the potential of
Iceland for the mapping of polarity reversals was
not realized until the field work of J. Hospers (Fig.
2) began in 1950.
By 1950, the geology of Iceland had been studied
by several eminent geologists, but the emphasis in
their work was naturally on the active volcanic,
tectonic and geothermal manifestations of the
country. In older regions, individual localities of
plant and marine fossils, alteration minerals, intrus-
•ons, and glacial deposits had received most attent-
•on. Of course, no radiometric dates were available
°n Icelandic rocks; theoldest fossil occurrences had
long been considered to be of Miocene age, but the
opinion of an Eocene age grew stronger during the
forties to middle sixties. Systematic mapping of
stratigraphy in the pile of ílood basalts had not
started in 1950, and it may indeed have seemed a
dull and difficult taskgiven the apparent uniformity
of lava flows in the pile.
J. HOSPERS
During the 1950’s R. W. van Bemmelen and M.
G. Rutten from Utrecht carried out extensive field
mapping of Plio-Pleistocene extrusive and glacial
formations in Iceland. In 1950 they were joined by
J. Hospers, astudent from Utrecht who was beginn-
ing graduate research at Cambridge University. He
took part in their mapping eífort in the Akureyri to
Mývatn area, including both geological and gravity
work. and collected 25 samples from lavas in Ljósa-
vatnsskarð for paleomagnetic measurements (Hos-
pers 1951). Van Bemmelen intended to find if
magnetic intensity variations could be used for
stratigraphic studies in lavas (J. Hospers, pers.
comm. 1982). In 1951 Hospers continued his paleo-
magnetic work in Iceland, collecting that summer
altogether 633 hand samples. Some of these he mea-
sured in the field only, using a portable vertical-field
magnetometer. Specimens from others were mea-
sured in Cambridge (except for sediment samples
which were measured in Blackett’s laboratory in
Manchester). Those oollections that were reported
in Hospers’ published papers included five Hekla
lava flows, eight other postglacial flows, 65 Plio-
Pleistocene and Tertiary flows from Snaefellsnes,
over 50 flows from Esja and Hvalfjördur and 80
from Ljósavatnsskarð, as well as over 40 samples of
sediments from five different Icelandic localities.
Collections were also made e. g. from Iavas in Tjör-
nes and from the Palagonite formation in the Eyja-
fjöll area.
Hospers’ thesis (1953a) and papers on these
magnetic measurements from Iceland and elsew-
here (1953b, 1954a, b, c, d, 1955) had considerable
impact upon the geoscience community and were
widely quoted. His laboratory measurements of
remanencedirections yielded self-œnsistent results
which showed e.g. that the mean direction of the
field since the Pliocene approximated that of an
axial geocentric dipole; it followed that polar
wandering in this time had been much slower than
some authors had suggested. They also showed that
the lavas occurred in zones of several consecutive
flows which had alternating polarities but were
otherwise similar in overall mean directions, in
other magnetic properties, and in gross chemistry.
(The term “reverse” magnetization was first used
by Hospers in the above papers; he was also the first
to calculate pole positions from paleomagnetic
directions). As there was considerable variation on
the character of the lavas within each zone, Hospers
JÖKULL 32. ÁR 93