Jökull - 01.12.1982, Page 103

0- Geophys. Res. no. B8, 1982); preliminary magn-
etic results from the deep core drilling in Reyðar-
fjörður are reported by Gibson (1979).
In Fljótsdalur, IValker (in Dagley et al. 1967) mapp-
ed slx profiles on the NVV side of Norðurdalur. A
team from the National Energy Authority carried
out field mapping and polarity measurements in
this area in 1970 (Vilmundardóttir 1972), duplicating
some of VValker's work but also adding several new
profiles within and outside the area mapped by
VValker.
Einarsson (1971) summarised polarity measure-
ments made by Wensink (1964) the I. C./Liverpool
group, and himselfin the Fljótsdalur and Jökuldal-
ur areas, but his correlations between these areas
were not substantiated by later dating results.
McDougall et al. (1975), sampled at Bessastaðaá,
well beyond a short profile of Dagley et al. (1976) in
that river. Magnetic measurements and K-Ar dates
at this locality and at Hengifossá allowed a cor-
relation with the geomagnetic polarity time scale
and eliminated a 4 M. y. volcanic hiatus that had
recently been suggested to occur at the thick sedi-
mentary sequences outcropping in these rivers.
In the meantime, however, Wilson and McElhinny
(1974) had noted a considerable difference in mean
remanence direction between lavas in Fljótsdalur
and those in the fjord profiles to the east (yielding
respectively “far-sided” and “near-sided” poles).
This they suggested might be due to 10° apparent
polar wandering during the above mentioned 4 m.y.
hiatus. However, far-sided mean poles have not
been conlirmed to occur in comparable sequences of
similar age to Fljótsdalur, and the deviating mean
direction in the Fljótsdalur collection has yet to be
satisfactorily explained.
Finally, Guðmundsson (1978) extended previous
stratigraphic mapping efforts to all of Norðurdalur
and Suðurdalur, aided by lluxgate polarity mea-
surements. Some revision of previous correlations
was necessitated, and others may remain tentative.
Thus, the Kaena reverse event was suggested by
Walkins and Walker (1977) to be represented by flows
U 15 and V 8/9. However, the U 15 direction may
onlv be a brief excursion of the virtual pole to low
latitides rather than an event, V 8 is quite unstable
and V 9 is actually of normal magnetization.*
In central Iceland, Piper (1973a, 1979) has carri-
* l licse lavas were rcsampled by the present a uthor for laboratory measure-
ment in 1977 (unpublished). Other new polarity results obtained then
inelude llows T () (undcrlyingsandstone, R) , T 31 (above tillite, N), U 1
(N), V6 (conglomerate) and V 19 (pedestal to Laugarfell, N).
ed out mapping of volcanic units in two Iimited
areas. Some of these units are reversely magnetized
and most likely belong to the I.ate Matuyama
epoch.
N. D. WATKINS ANDOTHERS:
PALEOMAGNETISM
N. D. Watkins, then of the University of Rhode
Island, collected core samples for paleomagnetic
work from Jökuldalur and Bessastadaá in 1927-73
as mentioned above. VVith L. Kristjansson and I.
McDougall, he also sampled in 1973 two sections in
Borgarfjörður that had previously been mapped in
the field by Saemundsscn and Noll (1974) and by Jó-
hannesson) 1975). Results from these, with several
K-Ar dates, were published by Mc Dougall et al.
(1977), Watkins et al. (1977) and McDougall (1977).
In this work, two events in the Gilbert epoch were
dated for the first time. The Borgarfjörður profiles
reach up into the Lower Matuyama, and were
thought to include a normal polarity event, but due
to incomplete sampling and instabilities in ílows
NT102-110 its presence was not fully ascertained.
Additional sampling (Bragason 1981) indicates that
flows 107-112 all are reverse with low pole latitudes
(< 45°) except NT108 which may be normal. Flows
below 107 are reverse.
Watkins and collaborators sampled in 1974-76
and dated a long composite section in central north-
ern Iceland, including a normally magnetized se-
quence identified with geomagnetic epoch 9. In
1973-77, a composite section in Esja, Eyrarfjall and
Akrafjall was sampled. 'Fhese results were publish-
ed respectively by Saemundsson et al. (1980) and Krist-
jansson et al. (1980). See Fig. 6.
Statistical aspects of the geomagnetic secular
variation and reversal rates in these collections have
been discussed by Harrison (1980), llarrison and
Watkins (1979),Harrison et al. (1979), Kristjánsson and
McDougall (1982) andothers.
NW-ICELAND: PAI.EOMAGNETISM
Apart from a few very local details (Mercanton
1931, Einarsson 1963) the first paleomagnetic data
from the Northwest peninsula were reported by
Friedrich (1966) who mapped magnetic polarities in
a several hundred m thick lava pile around the
Brjánslækur fossiliferous sediments, by a compass.
Kristjansson (1968) sampled over60 lava flows in the
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