Differentially cemented & eroded sandstone in the Eocene of Fantasy Canyon, Utah, USA.

Fantasy Canyon has the most spectacular examples of differential weathering and differential erosion I've ever seen. The rocks are quartzose sandstones that were deposited on the eastern shore of ancient Lake Uinta, which existed during the Eocene. Some wisps and ribbons of dark-colored, magnetite-rich sand are present in the sandstone. The variety of chaotic rockforms at Fantasy Canyon are quite diverse - these cannot be explained by ordinary weathering and erosion. Close examination shows that erosion has acted upon differentially cemented sandstone. The sandstone has not undergone complete lithification and diagenesis - groundwater lobes have preferentially cemented portions of the sandstone, especially immediately adjacent to joint planes. The poorly-cemented sandstone was easily eroded & the better-cemented sandstone remains.

Stratigraphy: member C, Uinta Formation, Eocene