This panorama opens facing a rather blank wall. However, look closely and you can see the contact between the Tapeats sandstone formation and the Vishnu Schist formation. The Tapeats sandstone is the horizontally layered material which lies above the blocky, dense looking material just a few feet above the canyon floor. The the Contact Zone between them is the Great Unconformity. The Great Unconformity is a "line" where there is missing geological record of between 100 million and 1 billion years.