“After death, though, iron is let free from its cage. It forms minuscule iron nanoparticles and also generates free radicals, which are highly reactive molecules thought to be involved in aging. “The free radicals cause proteins and cell membranes to tie in knots,” Schweitzer said. “They basically act like formaldehyde.””
The fatal flaw in this explanation is that we don’t see this “iron preservation” in any more recent remains. Why doesn’t iron preserve soft tissue in remains that are only a few thousand years old, if it can preserve soft tissue in remains that are millions of years old? Logic dictates that there should be a much greater number of more recent remains preserved by this method, but in fact we see just the opposite.
Actually, they have been looking at younger fossils and have found similar results. See: http://rspb.royalsocietypublishing.org/content/274/1607/183
This is very new and has been controversial, centered mostly on Dinosaurs because because that’s where the original discovery took place.