If we weren’t the first industrial civilization on Earth, would we ever know?

A fascinating insight – what traces would be left of a civilisation which died out 4 million years ago? Certainly nothing on the surface (the oldest is only 1.8m years), and fossils are incredibly rare (only a few thousand dinosaur fossils exist despite their 180m year existence) – but what about chemical traces? https://rob.al/2K3Qjwz
Fossils and objects are unlikely to survive more than a few million years. Searching for chemical traces of industrialization offers an intriguing alternative.