Jökull


Jökull - 01.12.1984, Side 77

Jökull - 01.12.1984, Side 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
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