I am considering a plot for a screenplay in which it would be necessary for evidence of an alien visitation in the Mesozoic era to be discoverable today. Perhaps a message, or tools, or even better, alien technology. I have read that if mankind disappeared tomorrow, all traces of civilization aside from possible excavation or nuclear waste would be gone in a million years or so. I don't know if that is true, but I am wondering if it is possible to construct a material which could survive or preserve something for 65 million years. Certainly there are insects preserved naturally for millions of years in amber, so it would seem possible to create materials artificially. Any suggestions?