No, I very literally thought the local rocky hills were formed from huge piles of gigantic petrified sea turtles, horseshoe crabs, and stingrays. I saw their outlines and suggestions of their shapes in the rocks. It seemed self-evident to me that here were ancient creatures that had mineralized over time in rough piles. In smaller rocks they looked more like isopods, more creepy and Giger-like.

I took lots of pictures because I knew nobody would believe me. They are picture of rocks :)

That's hilarious.

neither here nor there but it sounds exactly like my experience on mushrooms, in which I explored a lot and took extensive notes of my thoughts and observations in what were later very self evident ways. The vastness of time was very evident. I wouldn't be shocked if the pathways activated were similar. I really wish we had more real time brain activity scanning available, then we could easily see when someone is going through X/Y/Z episode

They are describing a psychotic episode.

Is it a common metaphor?

The description is not a metaphor. “Lost my marbles” is a common one for psychosis, dementia and the like, though.

I know I'm being overly sensitive but I'm baffled at the downvotes on my post asking for clarification :/

You asked if it was a common metaphor in reply to someone saying it is not a metaphor. Perhaps you replied to the wrong comment by mistake?

If it's any consolation, I interpreted your question as "outside of this person's experience". It seems fair to ask the seemingly knowledgeable eurasiantiger such a question. In the interests of charitable interpretations.

It is not a metaphor.

Psychotic episodes are typically marked by delusions and hallucinations caused by things like sleep deprivation and stress leading to excess catecholaminergic activity, which causes the brain to temporarily misinterpret the senses and construct delusional logic around the interpretations in an attempt to form a cohesive internal narrative of the experience.