Environmental Engineering Reference
In-Depth Information
5
Volcanic pulses in the Siberian Traps as inferred from
Permo-Triassic geomagnetic secular variations
vladimir pavlov, fr´d´ ric fluteau, roman veselovskiy, anna
fetisova, anton latyshev, linda t. elkins-tanton, alexander v.
sobolev and nadezhda a. krivolutskaya
5.1 Introduction
There is little reason to believe that eruption of the Siberian Traps occurred gradually.
On the contrary, trap emplacement likely occurred in the form of brief but voluminous
volcanic pulses, as for example demonstrated for the Deccan Traps (Chenet
et al
.,
2008
,
2009
) in India and for the Karoo Traps (Moulin
et al
.,
2011
,
2012
) in South Africa.
To search for evidence of such pulses during formation of the Siberian Traps, and
to obtain time constraints on eruptive activity we have undertaken a paleomagnetic
study of several important trap volcanic sections from the Norilsk and Maymecha
-
Kotuy areas (
Figure 5.1
). To complement our work, we include paleomagnetic
directions published by Heunemann
et al
.(
2004
) from the Norilsk area. A brief
description of the sampling areas and the paleomagnetic results are presented below.
5.2 Sampling
Detailed paleomagnetic sampling was carried out on the Medvejia and Truba
sections in the Maymecha
-
Kotuy region (
Figure 5.1a
,
b
) during
field seasons in
2008 and 2009, and on the Sunduk and Ergalakh sections in the Norilsk region
in 2010 (
Figure 5.1c
). Between 8 and 20 oriented hand samples were collected
from individual lava
flows or tuff units. In total, about 1400 samples, representing
133 lava
flows, were collected and studied.
The Medvejia and Truba sections (
600 m thick) are on the Kotuy River and
include lava
flows of the Arydzhangsky and Onkuchaksky Formations. The
sections collectively constitute the most complete (among those exposed) sequence
of volcanic rocks of these formations in the region (
Figure 5.2
). The Medvejia
section contains in total 37 units of the Arydzhangsky suite, which consists of
