[phanimahesh]

A million is a mind bogglingly large number, especially in years. I honestly can not say eitherway if anything survives. Coins might end up as a lump of rock with slightly higher metal content than surroundngs.

(also, hi nemo! Found you. :P)

[nemo]

It is a very long time, but we still do have a lot of fossils, and with many human artifacts they won't fossilize so much as just sit there in their strata - we make artifacts that don't even need to fossilize since they are already stable, chemically inert, and resistant to biodegrading or corrosion, and if they do corrode, then in the right conditions those would be a kind of fossil. Ancient life made left lot of traces and humans are currently leaving as many traces as any other species has ever left, and we're leaving artifacts and other traces spread all across the globe, even in the oceans. We have fossils from >3 billion years ago. Not everything subducts. There's existent areas of long term geology stability and those areas are as littered with human traces, artifacts, and other remains as anywhere else. I honestly can't imagine all traces of humanity being undiscoverable considering in 100 million years, in 400 million subduction and time will have erased a lot, but I'm pretty confident there would be quite a few discoverable traces if some future life form were to apply modern archaeological methods then, esp. given that the scale and scope of changes humans are making is massive and global. At the very least future paleontologists would see the effects of humans on their habitat in the fossil record of the ongoing mass extinction, but I expect much more would be discoverable than that.