Science fiction and ocean acidification

Zimmer tells us we'll be able to recognize the human era by the sedimentary evidence of ocean acidification and mass extinction.

Sounds plausible. So what should we think of why we find a similar catastrophe 55 million years ago?

An Ominous Warning on the Effects of Ocean Acidification by Carl Zimmer: Yale Environment 360

... Scientists have been scouring the fossil record for periods of history that might offer clues to how the planet will respond to the current carbon jolt. They’ve found that 55 million years ago, the Earth went through a similar change. Lee Kump of Penn State and his colleagues have estimated that roughly 6.8 trillion tons of carbon entered the Earth’s atmosphere over about 10,000 years.

Nobody can say for sure what unleashed all that carbon, but it appeared to have had a drastic effect on the climate. Temperatures rose between 5 and 9 degrees Celsius (9 to 16 Fahrenheit). Many deep-water species became extinct, possibly as the pH of the deep ocean became too low for them to survive...

I'm sure I read this in a science fiction story once. Something to do with smart dinosaurs.

I'm just joking of course. We'd easily recognize the evidence of long extinct prior technological civilization from 55 million years ago. After all, we won't be just a peculiar layer of pollution in 55 million years, will we?

(I really am joking. Though if had been over 200 years rather than "10,000 years" with no volcanic explanation one would have to wonder.)