Last decade ice core digging in the West Antlantic Ice Sheet (WAIS) gave a big surprise. Diatoms in the mud under the ice sheet revealed that there has been a sea bottom with a maximum age of some 500,000 years but possibly younger. Science, Vol 281, Issue 5373, 82-85 , 3 July 1998 There was big commotion but apart from scary stories about sudden collapses of ice sheets the attention receded. Yet we are facing a formal "not understood" (science talk for mystery) phenonemon. Guess what's under the Greenland ice sheet. Grass and Trees! More here. I hope that they can date the sample roughly as carbon dating only goes to about 45,000 years. I think it will be a next surpsrise I doubt that these samples are older than half a million year. Strange that millions of years is automatically assumed because of the "counter intuitive" estimate for younger years, although this would probably yield a world record. Mineralization (fossilization) of small objects can be done in weeks in the right circumstances. These samples seem not to be fossilized. (source It's the question if sub freezing temperatures stop the process completely for millions of years. It may be as young as the last interglacial, the Eemian, 130,000 years ago. Then it would be a nice smoking gun for my little pet idea.