EVIDENCE FOR NON-DIPOLE SOURCES IN THE DEVONIAN GEOMAGNETIC FIELD FROM ANALYSIS OF PALEOMAGNETIC VECTORS IN ROCKS OF THE MINUSA DEPRESSION (SOUTHERN SIBERIA)

We propose a new outlook on the problem of the anomalous configuration of the Devonian geomagnetic field. The scattered distribution of paleomagnetic vectors identified in basic magmatic formations of the Minusa Depression resulted from the input of non-dipole sources of the main geomagnetic field when its strength was at a minimum. Fast alternations of ultra-brief episodes of decreasing paleointensity in the usually dominant geocentric axial dipole caused by extra-frequent reversals led to an increasing role in the shape of the geomagnetic field being played by the equatorial dipole and/or higher-order zonal harmonics, as well as global magnetic anomalies. Using statistical analysis in the observed pseudo-chaotic distribution of paleomagnetic vectors, we demonstrate clusters that could reflect the input of such sources. The calculated virtual poles coincide with global magnetic and gravitational anomalies, showing the probable present-day position of these sources and assume their long-term stationarity. The best fit is achieved by placing the Siberian paleocontinent near the northwestern African coast, above the hotspots, whose activity in the Devonian period could theoretically have caused the formation of known mantle plume provinces, including the Minusa Depression.

Devonian geomagnetic field, geocentric axial dipole, equatorial dipole, global magnetic and gravitational anomalies