The greatest mass extinction occurred some 245 million years ago, when an estimated 96 percent of all marine species were wiped out.
Around three-quarters of land species also went extinct.

This is from a story out several days ago that attempts to explain the cause for huge fossil layers of crustaceans and fish that are found all over the world (even on mountain tops).  Every amateur fossil hunter knows that you can easily find rocks with compacted layers of marine invertebrates, sometimes even in gravel driveways.  Fossils are only formed if they are buried relatively quickly, so fossil layers are usually explained as the result of local catastrophes (landslides, eruptions, meteors, floods). 

The story above points to that old enemy global warming, as the cause of these fossil layers.  Geologist Greg Retallack from the University of Oregon thinks that massive surges of methane and CO² killed off the millions of life forms preserved under our feet, many now extinct.  The global warming/extinction theory still leaves room for the giant meteorite that supposedly finished off the dinosaurs, but "global warming was already causing extinctions" when it struck, according to the story.

Creationists have a rather obvious solution for these widespread fossil layers:  Most were caused by a global flood that distributed marine life forms around the planet.  The dynamics of the flood, and the sediment settling that occurred during the slow receding of the floodwater, are responsible for the fossil patterns we observe today.