Environmental Engineering Reference
In-Depth Information
10
The origin of gases that caused the
Permian
-
Triassic extinction
alexander v. sobolev, nick t. arndt, nadezhda a. krivolutskaya,
dimitry v. kuzmin and stephan v. sobolev
10.1 Introduction
Even though a causal relationship between the emplacement of the Siberian large
igneous province (LIP) and the end-Permian mass extinction remains unproven,
the synchronicity of the two events, each the largest of its kind, makes it extremely
likely that the magmatism was linked directly to the biological crisis. Recent dating
has placed the eruption of the
flood basalts in the interval 252.4 to 251.2 Ma
(Kamo
et al
.,
2003
; White and Saunders,
2005
; Svensen
et al
.,
2009
; and other
chapters in this volume), which almost entirely overlaps that of the mass
extinction. Song
et al
.(
2012
) identi
ed two distinct extinction events: one at the
end-Permian and the other at the early Triassic, each of which contributed to the
mass extinction, and both within the time frame of the eruptions.
The cause of the mass extinctions was probably the release of gases that dramat-
ically increased global temperatures, upset the chemical balance within the
oceans, destroyed the ozone layer or were sufficiently toxic to destroy life both on
land and in the oceans (e.g. Wignall
et al
.,
2009
). There are two probable sources
of these gases, both related with the Siberian LIP. First, the mantle source
the
Siberian plume could potentially release large amounts of CO
2
and Cl, if it contains
altered recycled oceanic crust (Sobolev
et al
.,
2011
). These gases are released either
by explosive eruptions that typically occurred early in the magmatic episode,
or by degassing of erupted or intruded magmas during the major magmatic event.
The second possible source of gases lies within the sedimentary pile beneath the
volcanic plateau. These sediments consist, in large part, of carbonates and evaporites,
which are overlain by terrestrial sediments containing coal measures. When heated
at
-
flood volcanism, these sediments
released large amounts of CO
2
,SO
2
and halocarbons; when organic matter or coal
the margins of the intrusions that fed the
