We also had a huge sandstone boulder in a pasture at the top of a hill. Nothing remarkable about a big rock- except that this one was composed entirely of small marine animal shells. We called it the cheerio rock because that's what they looked like. I might have been a dumb farm kid, but I was smart enough to know there weren't any oceans close by and nobody was dumb enough to cart that boulder from the nearest salt water to it's current position!
Not necessarily. Eons ago, when the continents were in different locations than they are now (and before all of the mountains we now see were formed), parts of North America were under water. There are marine fossils in parts of this continent that are now nowhere near the ocean.