why should it be any bigger mystery than finding fossilized fish and seashells on mountains???
We have that too here in Panama. I saw fossilized seashells with my own eyes in a local geology course I took. What happens is Panama continues to rise out of the sea And this was way up high on a hill above the canal.
I assumed tectonic lift of the local plate was the reason sea levels around panama viejo had dropped enough to let foliage begin to grow in the old sea bed. I would assume within 10 years it could be out beyond the toll road bridge.