This perfectly preserved pine cone (not even fossilized) was found 120 feet down in a diatomaceous earth deposit in Northern California.  Tiny water plants called diatoms change carbon dioxide into oxygen.  They multiply extremely rapidly when there is an excess of carbon dioxide in the atmosphere.  "The fountains of the deep" (subterranean volcanoes which initiated Noah's Flood see Genesis 6-8) would have caused such an effect.  This explains the presence of vast deposits of diatomaceous materials in various parts of the earth.