New Paper on Permian Extinctions

Paul bristolia at yahoo.com
Wed Jan 23 09:48:28 EST 2008

The Journal of Geology has just published a new paper on Permian
extinctions. It is:

Retallack, G. J., and A. H. Jahren, 2008, Methane Release from
Igneous Intrusion of Coal during Late Permian Extinction Events
Journal of Geology. vol. 116, no. 1, pp. 1-20.

http://www.journals.uchicago.edu/doi/abs/10.1086/524120

"Abstract

Unusually large and locally variable carbon isotope excursions
coincident with mass extinctions at the end of the Permian
Period (253 Ma) and Guadalupian Epoch (260 Ma) can be attributed
to methane outbursts to the atmosphere. Methane has isotopic
values (δ13C) low enough to reduce to feasible amounts the
carbon required for isotopic mass balance. The duration of the
carbon isotopic excursions and inferred methane releases are here
constrained to <10,000 yr by counting annual varves in lake
deposits and by estimating peat accumulation rates. On
paleogeographic maps, the most marked carbon isotope excursions
form linear arrays back to plausible methane sources: end-Permian
Siberian Traps and Longwood-Bluff intrusions of New Zealand and
end-Guadalupian Emeishan Traps of China. Intrusion of coal
seams by feeder dikes to flood basalts could create successive
thermogenic methane outbursts of the observed timing and
magnitude, but these are unreasonably short times for
replenishment of marine or permafrost sources of methane.
Methane released by fracturing and heating of coal during
intrusion of large igneous provinces may have been a planetary
hazard comparable with bolide impact"

Yours,

Paul