Basaltic lavas from the southern Alborz, an area about 40 km northeast of Tehran, Iran, have been paleomagnetically
investigated. The lavas are of Late Devonian-Early Carboniferous age, and belong to the basal member of the
Geirnd Formation. At 11 sites a total of 80 cores was drilled.
Detailed analyses by means of progressive demagnetization of the natural remanent magnetization (NRM) were
made both by the application of alternating magnetic fields and by heating. Also, on a number of specimens a study was
done both with thin sections and with polished sections. There proved to be general agreement between the properties
of the characteristic NRM and the kind of Fe-Ti oxides in the lavas. In the case of specimens containing magnetite
only the characteristic NRM was entirely removed at temperatures just below 600°C, or in alternating fields up
to 1500/2000 Oe peak value; on the other hand, in specimens containing both magnetite and a substantial part of
hematite (martite) the final part of the characteristic remanence was removed at temperatures above 600°C, and this
remanence resisted alternating fields above 2000 Oe peak value. From the characteristic site-mean directions of 5
sites an average paleomagnetic direction is computed with D = 210.8 °, 1 = 66.9 °, and c~95 = 3.9 °.
This result might be taken as an indication that at the Devono-Carboniferous transition the southern part of the
Alborz was located in the present Indian Ocean off the Arabian coast
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