Jökull - 01.12.1982, Page 101

region, another team from Utrecht was sampling for
paleomagnetic measurements on the east side of
Eyjafjördur. Its work does not appear to have been
published in detail; some preliminary results are
quoted by Rutlen and Veldkamp (1964), and a polarity
sequence is shown by Hebeda et al. (1974). It in-
cludes a thick (1600 m) normal series of lavas bet-
ween Dalsmynni and Steinsskarð. 15 K-Ar dates
reported by Hebeda etal. from this area are scatter-
ed within the range of7-15 M. y.
R. R. DOELL
R. R. Doell of the U. S. G. S.,a pioneer in paleo-
magnetic researchin the western U.S., sampled 107
lavas in Iceland in 1964. These included 44 lavas in
I jömes and 35 in Snaefellsnes, the remainder being
late interglacial and Recent. Doell had developed
the first efiicient diamond core drill for extensive
field use, and his sampling was very thorough,
generally with 8 widely spaced samples per llow.
Due to delays in K-Ar dating attempts ( which
proved unsuccessful ), his detailed paleomagnetic
results were published several years later (Doell
1972).
Doell’s data on Icelandic postglacial flows appear
to be very reliable although he prefers to report only
NRM directions from many ofthese. However, they
do not fit well with the pole path drawn earlier by
Brynjólfsson (1957), and 2()th century lavas of these
investigators and Hospers do not yield poles close to
the present (IGRF) magnetic pole for Iceland. The
reason for this is probably to be found in the pres-
ence of strong magnetic anomalies in Iceland, from
scales of tens of km (lineations) to km (individual
volcanic centers), tensofm (local topography) and
m (irregularities surface relief and remanence in-
tensity in the flow itselfand underlying flow during
cooling). Other effects, such as the movement of
large rafts of these flows after solidification, may
also play a part. Further directional data from
postglacial Icelandic lavas were reported by
Schweitzer and Soffel (1980), but their samples were
largely oriented in declination by magnetic com-
pass only.
In Snaefellsnes, Doell (1972) found that some
lavas given as normal by Hospers (1953b, 1954c) in
Stöð and Búlandsgil, were actually ofreverse prim-
ary magnetization. Heconfirms, however, the nor-
mal polarity ofsome lavas in Mávahlíð sampled by
Hospers. Jóhannesson (1980) has compiled results
from extensive stratigraphic and polarity measure-
ments in Snaefellsnes and finds that the Tertiary-
Quaternary unconformity there spans millions of
years, contrary to speculative assumptions by Doell
(1972, p. 470).
Doell’s measurements on lavas from Tjörnes are
summarized in Einarsson et al. (1967). The Tjörnes
sequence is difficult to interpret unambiguously in
terms of global biostratigraphic and geomagnetic
time scales (see review by Eiríksson (1980)) but the
bottom flows of the Höskuldsvík lavas are most
likely older than the Kaena event in age. According
to Hospers (1953a, fig. 35) the upper part of the
underlying main sedimentary sequence is normally
magnetized but the lower part is reverse. This may
indicate that the sediments were deposited near the
Gauss-Gilbert boundary, but Soviet magnetic mea-
surements on these sediments (quoted by Eiríksson
1980) are not quite in agreement with those of
Hospers. It would be useful to carry out careful
sampling of the Tjörnes beds and the underlying
lavas to ascertain theiroriginal magnetic polarity.
Doell brought with him to Iceland in 1964 a
portable fluxgate magnetometer which had recently
been developed by him and A. V. Cox. He kindly
allowed Icelandic scientists to borrow this instru-
ment; with Doell's permission an improved model
was marketed in the following year by Rafagna-
tækni Ltd. of Reykjavík. Fluxgate meters havesince
then been used extensively in local stratigraphic
mapping in Iceland.
IMPERIAL COLLEGE/LIVERPOOL GROUP
-GENERAL PALEOMAGNETISM
Around 1950 P.M.S. Blackett had developed a
very sensitive magnetometer, soon found to be an
excellent instrument for paleomagnetic research.
One of his students at Imperial College, R. L. VVil-
son from Ontario, did a paleomagnetic study of
Antrim basalts mapped by G. P. L. VValker of that
College.
In 1964 VVilsonbegan paleomagnetic sampling in
Iceland in collaboration with T. Sigurgeirsson and
T. Einarsson. I'he first part of this effort covered
profiles in SVV-Iceland mapped by Einarsson, the
second part (1964-65) covered a section through the
lava pile in E-Iceland where VValker had already
provided an entirely new picture of volcanic and
tectonic processes by lús mapping.
VVilson’s 1964 party included P. Dagley from
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