What proof do you have that rocks are a certain age?
Evolutionists have been taking their own assumptions as truth and building "evidence" with them for a long time.
The New York Times lies consistently. You can't trust it.
The exact answer is above my pay grade. I would assume that the level or rock had material mixed with it that could be carbon dated, or else mixed in with other fossils that could be dated. Also the evidence for these ancient jellyfish was found in Utah. I am not an expert in archeology, paleontology, and geology, so I won’t take it beyond the following, but I can say that it has been a few years since the ocean covered Utah. I was just trying to help, because I was curious as well.
I can vouch for that. Man, it is dry as a bone out here. But, we do have some "fishy" artifacts.