USGS Earth Science Photographic Archive digital files: hjk00831 and hjk0831a
The white caprock along Stillwater Canyon displays dark streaks of desert varnish that are typical on the White Rim Sandstone (late Permian). The White Rim sandstone stands out in contrast to the reddish beds of the underlying Organ Rock Formation (Permian) and the overlying Moenkopi Formation (Triassic). The softer shales of the Moenkopi Formation weather and erode faster than the underlying White Rim Sandstone. As a result, the White Rim Sandstone forms a caprock ledge along the Green and Colorado River gorges throughout much of the Canyonlands National Park region. They are particularly visible from overlooks throughout the Island-In-The-Sky District.
