All three formations of the Glen Canyon Group were laid down in the Mid to Late Triassic during a time of increasing aridity. Slightly clockwise and northward movement of the North American Plate was bringing the area into a dryer climatic belt. The direction of cross-bedding in Glen Canyon Group sand dunes suggests that prevailing winds from the north transported the sand into the region. Outcrops of the Glen Canyon Group's three formations are the most prominently exposed rock layers in the spine of the Waterpocket Fold. Together they reach a thickness of 1,500 to 2,700 feet (460 to 820 m) in the area and their sandstones are seen in many of the arches, domes and slot canyons in Capitol Reef. They are, from oldest (lowest) to youngest (highest);