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An extinction contributer?



The October 23rd issue of Science News carried an interesting little
report on an event dated 55 mya.

An ocean sediment study turned up a "global burp" (as the article
title put it) of "billions of tons of carbon-rich gas". This had
the effect of further warming up an already warm climate.

The study indicates the oceans were flooded with these gases over
a very short period of time, perhaps just a few thousands of
years, and that it took 120,000 years for the oceans to
restabilize themselves. This gas release has been of for a
few years, tho details have been lacking.

Another researcher, Gerald Dickens of Townsville, Australia,
has proposed that the gas came from frozen methane hydrate
deposits that sit on the continental shelves. If the hydrate
becomes "unstable" (warmed, presumably), then methane gas
is released, first into the oceans, then into the atmosphere.
The hydrate hypothesis is said to be gaining favor, esp. 
since it fits the results from the sediment study.

The question is what destabilized the hydrate. Suggestions
include shifting ocean currents and even a volcano eruption
(in the Caribbean no less!).

This article states that this event is of interest as this
caused "a massive oceanic extinction and fostered a grand
migration of land species between continents".

Now, the first thing I thought here was: how about a 
meteor/comet impact? From there I also thought, how about
something like this just 10 million years earlier?

I've noted the number of recent posts on extinction and
the list of possible contributors. Could a hydrate
release have played a role? Based on what happened at
55 mya, pronounced effects are possible. 

This would appear to have some testable components. For
example, would sediments from that time period show
evidence of gas release? If methane is assumed, what is 
the amount that could be tolerated by those species
that survived the KT boundary? 

And could the dinosaurs have had little tolerance?

Some refs for this article appear at

 http://www.sciencenews.org/sn_arc99/10_23_99/fob1ref.htm

rich