Grand Canyon National Park- Toroweap Formation_0936
A detail of the mixture of stones that make up the Toroweap Formation.
NPS Photo by: Kristen M. Caldon
Toroweap Formation: thickness: 130-375 ft.
The Toroweap Formation, a mixture of shales, sandstones, and limestones, forms the first slope below the rim of the canyon.
It was deposited 273 million years ago, during the Paleozoic Era- Late Early Permian Period.
This formation, with its variable rocks, marks the return of the sea to the Grand Canyon region. Both transgressions and regressions occurred during deposition.
The Toroweap Formation was thus deposited in everything from shallow marine and intertidal to coastal dune environments.