Jökull - 01.12.1984, Page 77

may also play a part in determining remanence
stability.
CONCLUSIONS
Paleomagnetism is an important technique to
geological research in Iceland, especially in stra-
tigraphic mapping and in the interpretation of
aeromagnetic anomalies.
Considerable information can be obtained by
means of simple methods, such as fluxgate
measurements of hand samples in the field. How-
ever, this method should only be used in conjunc-
tion with other stratigraphic indicators rather
than on its own. Also, error sources in the
method, connected with secondary burial, the
presence of viscous remanence, and secular varia-
tion, etc. should be allowed for; and adjacent
profiles should overlap significantly.
When such precautions are taken, laboratory
measurements of remanence are generally found
to confirm field polarities.
The quantitative interpretation of magnetic
anomalies in Iceland in terms of crustal structure
is still at a very preliminary stage. However, it is
clear that both the surface geology and the
magnetic properties of rocks have to be reason-
ably well known before such interpretations can
be attempted. It appears that the magnetic prop-
erties of basalt lavas do not vary greatly between
regions of Iceland outside the active volcanic
zone; the vertical variation of these properties is
minor above sea level, but the more highly
altered subsurface formations have not been suf-
ficiently investigated.
ACKNOWLEDGEMENTS
Some of the measuremetits described herein
were made during a three-month visit to the
School of Oceanography, Oregon State University
in 1983; discussions with Shaul Levi, Gunnar
Bödvarsson, Bob Karlin and Haraldur Auduns-
son during this visit were particularly useful. This
research visit was sponsored by the Fulbright
Exchange Visitors Programme.
REFERENCES
Deutsch, E. R., L. Kristjánsson and B. T. May
1971: Remanent magnetism of Lower Terti-
ary lavas on Baffin Island. Can. J. Earth Sci.
8: 1542-1552.
Ellwood, B. B. 1978: Flow and emplacement
direction determined for selected basaltic
bodies using magnetic susceptibility anisot-
ropy measurements. Earth Planet. Sci. Lett.
41: 254-264.
Kristjansson, L. 1983: Bergsegulmælingar — nyt-
söm tækni við jarðfræðikortlagningu. Nátt-
úrufræðingurinn 53: in the press.
Kristjansson, L., and I. McDougall 1982: Some
aspects of the late Tertiary geomagnetic field
in Iceland. Geophys. J. Roy. Astr. Soc. 68:
273-294.
Piper, J. D. A. 1973: Interpretation of some
magnetic anomalies over Iceland. Tecto-
nophysics 16: 163—187.
Watkins, N. D. and G. P. L. Walker 1977: Mag-
netostratigraphy of Eastern Iceland. Am. J.
Sci. 277: 513-584.
Wilson, R. L., S. E. Haggerty and N. D. Wat-
kins: Variations of paleomagnetic stability
and other parameters in a vertical traverse of
a single Icelandic lava. Geophys. J. Roy.
Astr. Soc. 16: 79—96.
Wood, D. A. and I. L. Gibson 1976: The
relationship between depth of burial and
mean intensity of magnetization for basalt
from Eastern Iceland. Geophys. J. Roy. Astr.
Soc. 46: 497-498.
Manuscript accepted 30 Dec 1983.
Ágrip
ATHUGASEMDIR VARÐANDI
TÚLKUN SEGULSTEFNU-
MÆLINGA Á BERGI
Leó Kristjánsson,
Raunvísindastofnun Háskólans
Á undanförnum árum hafa mælingar á segul-
stefnu gegnt mikilvægu hlutverki við kortlagn-
ingu á afstæðum aldri jarðlaga hérlendis, einkum
Tertier hraunlaga. Höfundur, sem hefur fengist
við slíkar mælingar í allmörg ár, hefur nýlega lýst
undirstöðu þessara aðferða (Kristjánsson 1983).
Mælingar af þessu tagi má gera hvort heldur er á
handsýnum, á borkjörnum Jarðborana, á smærri
kjörnum í rannsóknastofu, eða með túlkun seg-
ulmælinga úr lofti.
Við þær mælingar, sem gerðar hafa verið á
undanförnum árum, hefur aflast margskonar al-
menn reynsla og þekking á fyrrnefndum mæliað-
JÖKULL 34. ÁR 75