Environmental Engineering Reference
In-Depth Information
5.5 Conclusions
(1) Paleomagnetic studies of several key sections of the Permo-Triassic traps
of the northern Siberian platform indicate that the majority of volcanism in
the Norilsk and Maymecha
-
Kotuy regions was formed during a limited
number of volcanic pulses and individual eruptions. Specifically, for the
composite Kotuy section our calculations reveal 17 pulses and 13 individual
eruptions, and for the composite Norilsk section, 23 pulses and 12 individual
eruptions. This conservatively implies that the duration of active volcanism in
the Kotuy and Norilsk sections did not exceed a time interval on the order of
10 000 years. This estimate does not include the quiescence periods that
separate the volcanic pulses and individual eruptions. Nevertheless, the general
absence of sedimentary layers and weathering crusts between the
flows in the
studied areas is a clear indication that the quiescence periods were brief.
(2) Our study con
rms the occurrence of thick transitional and excursional inter-
vals in sections of the Norilsk region, as suggested by Heunemann
et al
.(
2004
)
and Gurevitch
et al
.(
2004
). These intervals can be traced across the entire
Norilsk region. This observation indicates that at least one-quarter of the
Norilsk region volcanic sequence may have been formed during a relatively
short time interval at the time of a reversal of the geomagnetic
field, i.e. within
several tens of thousands years or even faster. However, we stress that
available data are not suf
rm that observed transitional and excur-
sional intervals are parts of the same geomagnetic reversal. Therefore, the time
period between observed transitional and excursional intervals may have been
signi
cantly larger, as was suggested in recent petrological and geodynamical
studies (Sobolev
et al
.,
2009
,
2011
). Tracing the transitional interval through
the Kharaelakh, Norilsk and Imangda troughs as well as the subdivision of
sections suggested in this study, implies that more than 20 000 km
3
of lava
may have been erupted in just a few volcanic pulses and individual eruptions.
cient to af
Acknowledgements
This work was supported by the US National Science Foundation
“
The Siberian
flood basalts and the end-Permian Extinction
”
(EAR-0807585); Russian Founda-
tion for Basic Research, projects #12-05-00403, #13
-
05-12030 and #10-05-00557;
and The Ministry of Education and Science of the Russian Federation (grant 14.
Z50.31.0017).
References
Biggin, A. J., van Hinsbergen, D. J. J., Langereis, C. G., Straathof, G. B. and Deenen,
M. H. L. (2008). Geomagnetic secular variation in the Cretaceous Normal Superchron
and in the Jurassic.
Physics of the Earth and Planetary Interiors
, 169,3
-
19.
