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Re: The K-T boundary extinction: bolide or volcano?
I can't say anything about the Siberian Traps. They are humongous beyond
imagination, and their precise stratigraphic relationship to the P-Tr
boundary and any part of the mass extinction is still not known.
But what is said about the Deccan Traps, frankly, is just a rehash of the
old "argument" that I thought had at long last died out: "if something is 1)
popular and 2) spectacular, that proves it must be false". _Yes_, the
biggest eruption phase of the Deccan Traps _did_ have an effect on the
climate (the global average temperature rose by at most the difference
between glacial and interglacial), and then the episode _ended_ and the
climate _cooled to pre-eruption levels_ _100,000 years before_ the K-Pg
That was in Science, well over two years ago. In my personal experience
Science articles are easier to miss than those of Nature, but... I mean...
it's not the Special Papers of the Occasional Publications of the Town Hall
Museum of Superbled-sur-Loire.
G. Ravizza & B. Peucker-Ehrenbrink: Chemostratigraphic Evidence of Deccan
Volcanism in the Marine Osmium Isotope Record, Science 302, 1392 -- 1395 (21
"Continental flood basalt (CFB) volcanism is hypothesized to have played a
causative role in global climate change and mass extinctions. Uncertainties
associated with radiometric dating preclude a clear chronological assessment
of the environmental consequences of CFB volcanism. Our results document a
25% decline in the marine 187Os/188Os record that predates the
Cretaceous-Tertiary boundary (KTB) and coincides with late Maastrichtian
warming. We argue that this decline provides a chemostratigraphic marker of
Deccan volcanism and thus constitutes compelling evidence that the main
environmental consequence of Deccan volcanism was a transient global warming
event of 3° to 5°C that is fully resolved from the KTB mass extinction."