Environmental Engineering Reference
In-Depth Information
18
Oceanic anoxia during the Permian
Triassic
transition and links to volcanism
-
ellen k. schaal, katja m. meyer, kimberly v. lau, juan carlos
silva-tamayo and jonathan l. payne
18.1 Introduction
One of the best-documented environmental perturbations at the Permian
-
Triassic
transition is the development of extensive oceanic anoxia, a prime suspect in the
mass extinction of marine organisms at the end-Permian (Wignall and Hallam,
1992
). Ever since the eruption of the Siberian Traps
flood basalt province was
recognized as contemporaneous with the Permian
-
Triassic boundary (PTB; Renne
et al
.,
1995
), there has been ongoing research on how the Siberian Traps may
have caused changes in ocean chemistry and, ultimately, mass extinction. Massive
volcanism could affect ocean oxygen content through both greenhouse warming
and reduced solubility of oxygen in seawater (Wignall and Twitchett,
1996
) and
continental weathering feedbacks on nutrient delivery, primary productivity and
oxygen demand (Meyer
et al
.,
2008
).
The development of new proxies for ocean redox chemistry over the last decade
has enabled rapid increases in empirical constraints on Permian
-
Triassic ocean
anoxia. Consequently, numerous proxy records have been produced since the last
systematic review of the topic by Wignall and Twitchett (
2002
). Here, we review
the constraints provided by each proxy (summarized in
Table 18.1
) and discuss
insights from Earth system models and geological observations in evaluating the
potential role for Siberian Traps volcanism in driving ocean anoxia.
18.2 Lithological evidence for anoxia
18.2.1 Bioturbation intensity and black shales
Poorly bioturbated,
fine-grained sediments are typical of dysaerobic to anoxic
depositional settings (reviewed in Wignall,
1994
). Such sediments have long been
