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K-Pg extinction global firestorms



From: Ben Creisler
bcreisler@gmail.com


A new paper of interest:

Douglas S. Robertson, William M. Lewis, Peter M. Sheehan & Owen B. Toon (2013)
K-Pg extinction: Reevaluation of the heat-fire hypothesis.
Journal of Geophysical Research: Biogeosciences (advance online publication)
DOI: 10.1002/jgrg.20018
http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20018/abstract


The global debris layer created by the end-Cretaceous impact at
Chicxulub contained enough soot to indicate that the entire
terrestrial biosphere had burned. Preliminary modeling showed that the
reentry of ejecta would have caused a global infrared (IR) pulse
sufficient to ignite global fires within a few hours of the Chicxulub
impact. This heat pulse and subsequent fires explain the terrestrial
survival patterns in the earliest Paleocene, because all the surviving
species were plausibly able to take shelter from heat and fire
underground or in water. However, new models of the global IR heat
pulse as well as the absence of charcoal and the presence of
noncharred organic matter have been said to be inconsistent with the
idea of global fires that could have caused the extinctions. It was
suggested that the soot in the debris layer originated from the impact
site itself because the morphology of the soot, the chain length of
polycyclic aromatic hydrocarbons, and the presence of carbon
cenospheres were said to be inconsistent with burning the terrestrial
biosphere. These assertions either are incorrect or have alternate
explanations that are consistent with global firestorms. We show that
the apparent charcoal depletion in the Cretaceous-Paleogene layer has
been misinterpreted due to the failure to correct properly for
sediment deposition rates. We also show that the mass of soot
potentially released from the impact site is far too low to supply the
observed soot. However, global firestorms are consistent with both
data and physical modeling.

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Press release:
http://www.colorado.edu/news/releases/2013/03/27/cu-study-provides-new-evidence-ancient-asteroid-caused-global-firestorm