While hiking with a friend in New York State, you discover marine fossils in sedimentary strata at hight elevations. What is the most logical explanation for their presence?

There used to be an ocean there millions of years ago but then it dried up and there was a bunch of dead shellfish on the sea floor when the ocean dried up but as the years went on the tectonic plates pushed the ground into mountains and the dead (and now fossilized) shellfish got pushed up too, and that's why there are marine fossils at the top of a mountain in New York.