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