Someone has actually written up a scientific paper discussing the hypothesis that the PETM or other events in the geologic record was caused by a prior industrial civilisation. (If you’re one of the authors, I apologise for telling you something you already know, but if you’re not, I thought you might be interested.) The short version is that there’s no smoking gun, but they can’t rule it out either.
One item the authors don’t go into, which I think is relevant, is the question of whether there are missing fossil fuels. Google tells me that pretty much all existing fossil fuels were formed at least 65 million years ago, which I think makes it unlikely that the PETM 55mya was a previous industrial civilisation, because they’d have burned those fuels instead of leaving them for us to find. But I have zero geological expertise, so someone who knows better than me might be able to pick holes in that argument.
Someone has actually written up a scientific paper discussing the hypothesis that the PETM or other events in the geologic record was caused by a prior industrial civilisation. (If you’re one of the authors, I apologise for telling you something you already know, but if you’re not, I thought you might be interested.) The short version is that there’s no smoking gun, but they can’t rule it out either.
One item the authors don’t go into, which I think is relevant, is the question of whether there are missing fossil fuels. Google tells me that pretty much all existing fossil fuels were formed at least 65 million years ago, which I think makes it unlikely that the PETM 55mya was a previous industrial civilisation, because they’d have burned those fuels instead of leaving them for us to find. But I have zero geological expertise, so someone who knows better than me might be able to pick holes in that argument.