RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES1004, doi:10.2205/2006ES000191, 2006

Introduction

[2]  The boundary between the Paleozoic and Mesozoic eras was marked by the intensive plume-type magmatism, associated with the activity of the Siberian superplume and other plumes, the origin of which is believed to have been associated with the Earth core and mantle boundary [Ernst and Buchan, 2003; Grachev, 2000; and others]. In this case, this must have been reflected in the behavior of the geomagnetic field. As follows from the analysis of the geomagnetic field in the Cenozoic and in the vicinity of the Mz-Kz boundary [Pechersky, 2001; Pechersky and Garbuzenko, 2005], a change in the core conditions, leading to the geomagnetic field reversals and to changes in the paleointensity, is not directly related to this boundary, or to the generation of lower-mantle plumes, or to the generation of the magnetic field direction variations. The magnitude of the field direction variations grows closer to the epicenters of lower-mantle plumes, the vigorous magmatic activity of which being close to the modern one (Afar, the volcanoes of the Khamar-Daban Ridge and of the Bolshoi Anyui R. basin, and the Buve, Hawaii, Iceland, Reunion, and Samoa volcanic islands), or to the Mz-Kz boundary (North-Atlantic volcanic province and Deccan traps). However, the origin of these plumes, which is usually correlated with the growth of the magnetic field variation magnitude, took place 25-50 million years befor present-day or before the Mz-Kz boundary. This "retardation" is usually associated with the time of the plume rising from the core-mantle boundary to the Earth surface. A change in the core condition, which caused the geomagnetic field reversals, also began some 20 million years earlier than the Mz-Kz boundary.

[3]  The retardations of the onsets of the geological eras from the minima of the reversal frequencies were reported for the Phanerozoic [Khramov et al., 1982; Molostovskii et al., 1976; Pechersky and Didenko, 1995] and for the whole of the Neogaean [Pechersky, 1997, 1998]. This retardation from the reversal frequency peaks is typical of the average velocity peaks of the continent motions [Pechersky, 1998]. This retardation varies from 20 to 60 million years with the average value being 35 pm 10 million years, which correspond to the velocity of the material rising from the core-mantle boundary to the Earth surface, ranging from 4 cm year-1 to 10 cm year-1. This velocity agrees with the average drifting velocities of the main continental plates [Jurdy et al., 1995; Pechersky, 1997, 1998; Zonenshain et al., 1987; and others].

[4]  The aim of this paper is to analyze the behavior of the geomagnetic field in the time interval of 340 Ma to 200 Ma and the potential association of the Siberian superplume with it. This time interval includes the P/T boundary and the potential time interval prior to, during, and after the formation of the Siberian plume and its manifestations on the Earth surface. According to many data, the time of the igneous activity of the Siberian traps was dated 251 pm 0.2 Ma and coincided with the P/T boundary, where as generally the trap magmatism of Siberia lasted roughly from 260 Ma to 240 Ma [Ivanov et al., 2005]. As follows from the magnetostratigraphic data available [Gurevich et al., 1995, 2004], the major period of the volcanic trap activity in Siberia can be dated 251-249 Ma, generally embracing two magnetozones in the Late Permian (Maimecha-Kotui Province) and five magnetozones in the Early Triassic (West Taimyr Traps).


RJES

Citation: Pechersky, D. M. (2006), Geomagnetic field in the vicinity of the Paleozoic-Mesozoic boundary and the Siberian superplume, Russ. J. Earth Sci., 8, ES1004, doi:10.2205/2006ES000191.

Copyright 2006 by the Russian Journal of Earth Sciences

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