  If an industrial civilization had existed on Earth many millions of years
prior to our own era, what traces would it have left and would they be
detectable today? We summarize the likely geological fingerprint of the
Anthropocene, and demonstrate that while clear, it will not differ greatly in
many respects from other known events in the geological record. We then propose
tests that could plausibly distinguish an industrial cause from an otherwise
naturally occurring climate event.
