The twisted and deformed layers of sandstone at White Pocket in northern Arizona have puzzled geologists for some time. The parent formation is the 140 million-year-old dune-forming Navajo Sandstone, that covered a large area, much like todays Sahara Desert. One theory holds that after the Navajo was deposited, but before it was turned to stone by the weight of younger layers, there was a period of time when portions of it were wet. An earthquake triggered a sand-slide in a large dune and the layers of sand were plastic enough to deform, but not brittle enough to break completely. The whole area was subsequently covered by younger sand that we eventually turned to stone through pressure and weight, and all that rock was removed by erosion in the last fifty million years, uncovering what we see today
From my ebook: Signatures.