Building a Cabin on Solid Rock
You need an engineer, and he may want/need a site characterization. Ledge, thickness, type, stability, likeness to shift side to side, up and down, etc. Rock can make a very stable foundation; however, it can also be more apt to shift than normal soil under certain conditions.
I have a friend whom built on Lake Champlain up here. His lot was basically a ledge. He dug to the ledge. They drilled and shot anchors of some sort into the ledge and his footings were poored directly on it. It was a very overbuilt place (that's his style) but nothing ever moved. He had mammoth footings, one in the center of the house that was like 8'x8'x4' that supported a granite planter box which separated the dining room and kitchen. There was another for a similary constructed fireplace.