Grand Canyon National Park: Supai Group 0789
Supai Group's 800 foot / 244m rock layers as seen along Hermit Trail. NPS Photo by Kristen M. Caldon.
The rocks of the Supai Group are red sandstones and siltstones, deposited 315-285 million years ago during the Paleozoic Era- Early Pennsylvanian Period.
Supai Group rocks are primarily non-marine, meaning that they were not deposited in the ocean. Instead, the Supai Group was primarily deposited along a coastal low-land plain. At times it was swampy while at other times it was dry and sandy.
Plant fossils and high-angle aeolian (wind-blown) sand dunes reveal these two different environments.
The red color in the Supai Group rocks comes from iron oxide, which is perhaps better known as rust. It is this mineral that also stains the Redwall Limestone below.