The Canyon’s Clues to Earth’s History

Kaibab Limestone

250 million years old

This limestone is creamy to grayish-white in color. It was formed by a shallow sea that came in and went back out many times. This layer lies on top of both rims. Fossils found here include sponges, corals, and brachiopods or small sea animals.

Toroweap Formation

260 million years old

This slope is pale yellow to gray crumbly limestone, sandstone, and shale. Reptile footprints are found here. They show that this zone was a desert once, when it was the surface of this area.

Coconino Sandstone

280 million years old

These are mighty cliffs of sandstone. This layer was deposited by wind, which blew sand across the region. Tracks of spiders, scorpions, and lizards are found in this layer.

Hermit Formation

285 million years old

The red of this flaky shale comes from iron oxide. That’s rust! It holds fossils of reptiles and amphibian tracks. There are insect fossils too, including a big dragonfly. The shale also contains many worm burrows. Plant fossils of conifers and ferns suggest that, very early, there was plenty of rainfall and maybe even forests.

Supai Group

300 million years old

These shale, limestone, and sandstone layers look like red stairs. They formed when amphibians first evolved. Fossils include corals and other small sea animals. Some places contain land plants and reptile tracks.

Redwall Limestone

340 million years old

This sheer limestone cliff forms a barrier that is hard to cross. This layer divides the forest above it from the desert below. The area is stained red by iron oxides washed down from the layers above. It’s also pitted with caves. Fossilized remains of sea animals are found here.

Temple Butte Limestone

350 million years old

The western region has cliffs hundreds of feet high. The color of this layer ranges from purple in the east to gray or cream in the west. Many marine fossils are found here.

Tonto Group

Group of layers 530 million years old

Muav Limestone (top left)
This layer is a gray limestone separated by shale and sandstone. It has few fossils.

Bright Angel Shale (top center)
Created from mud left after water washed over the area, the shale is mostly green. The rock contains sea animal fossils.

Tapeats Sandstone (top right)
This dark brown layer contains sea animal fossils.

Vishnu Complex

1 to 2 billion years old

The hard rocks at the bottom of the canyon are the oldest. They were spit out as lava when volcanoes erupted. The melted rock cooled and hardened into a variety of colors—gray, black, blue, and even pink.