A geologist believes that a peculiar rock formation is proof of the Silurian hypothesis: the remains of an incredibly ancient civilisation that pre-dates the evolution of humans. They put together a team that comes to the conclusion that the formation is a calendar on a geologic scale over millions of years, which is warning of something that is set to recur soon. But it is not a warning, it is a promise: the ancient builders are 'returning'.
alternatively
A palaeontologist gets put into a dream state and projects himself back into the body of a Tyrannosaur, in which shape he kills a bunch of dinosaurs and arranges their bodies to be fossilised in a particular way in order to spell out an insult to his rival.
A short story in a Twilight Zone mode