PALEOMAGNETISM OF TRAP BASALTS IN THE NORTHWESTERN SIBERIAN CRATON, FROM CORE DATA
N.E. Mikhal'tsova, A.Yu. Kazanskya, V.V. Ryabovb, A.Ya. Shevkob, O.V. Kuprisha, and V.Yu. Bragina
aA.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
bV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Paleomagnetism, magnetostratigraphy, trap basalts, trap magmatism, Permian-Triassic boundary, Siberian craton, Noril'sk area
Pages: 1228-1242
Abstract
We present new paleomagnetic data for continental flood basalts (Siberian traps) obtained from cores of two boreholes in the northwestern Noril'sk area, within the Kharaelakh and Vologochan basins. Paleomagnetic measurements of lava and tuff samples from KhS-59 and SSV-19 boreholes allowed reconstructing and correlating the polarity patterns. Thus, multiple paleomagnetic anomalies (PA) have been discovered as short-term polarity changes in narrow intervals of the magnetostratigraphic section above the principal reversal at the boundary between the Ivakin and Syverma Formations.
The most prominent anomalies are observed at the bases of the Morongo and Mokulai Formations. The samples from the anomalous intervals differ from those of other intervals neither in magnetic properties nor in mineralogy and magnetic grain sizes. Therefore, the revealed PMA record excursions of the geomagnetic field. Comparison of the results with the Meishan Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary implies a revision to the P-T position in the trap basalt succession of the Noril'sk area. Judging by the EMF behavior, basalts in this part of the trap province erupted for at least 500 Kyr during the interval of stable normal polarity.
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