The Navajo Sandstone is the largest unit in Zion National Park. However,
the rocks that are younger were deposited in wetter conditions. The
Navajo Sandstone was deposited during desert conditions which continued
for about 20 million years. The Navajo Sandstone was formed when the
dinosaurs were rulers of the Earth.
In the Navajo Sandstone you see thick, almost horizontal beds, which
may be up to 7 meters in thickness. Within these thick horizontal
beds are thinner structures that show cross bedding, because they
are angled with respect to the horizontal beds. The picture shows both
horizontal and cross beds. Cross bedding indicate that sediments were
deposited by a steady flowing current of either water or wind. So
how do geologists know the Navajo was deposited in desert conditions?
Navajo Sandstone cross bedding