Fossils found in these layers include ... and sponges. Known as the Grand Canyon Supergroup, these layers of rock lie at an angle relative to the layers of rock above. The layer labeled Bass ...

so significant fossils are extremely rare. Next comes the Paleozoic Strata, comprised of the layered reddish rocks that you most associate with the Grand Canyon. This layer is a relic from the ...

"The Tonto Group of Grand Canyon holds a treasure trove of sedimentary layers and fossils chronicling the Cambrian Explosion some 500 million years ago," paper author and Utah State University ...