This sandstone layer is younger than those shale and limestone beds." This statement is an example of?

Answer 1

An advancing shoreline or a delta prograding out to sea. A certain depths sea critters excrete limestone, which they use to build their shells. As (silt) sediments start clouding the water limestone can no longer precipitate. As the seafloor get more and more shallow, sands start to deposit, as in a beach environment. Somewhere near is (probably) a river delta, supplying siliclastics for the beach.