The tully limestone stands out as a ridge of rock between valleys developed on the moscow and geneseo formations. what might account for this landscape pattern?

Shales weather in what are called a declining pattern. They erode more eagerly than limestone or dolomite which weather very slowly. If the limestone has been tilted on edge, a valley would form on either side of the limestone ridge since the shales would weather much more rapidly around it. Likewise if two rivers erode the formations at dissimilar positions of exposure of the different shales, the ridge will be left between them.