Geological Time Recorded in Grand Canyon Rocks

The Grand Canyon's exposed rock layers span from the Precambrian to the Cenozoic, offering a window into billions of years of Earth history:

Precambrian (~1.8 billion years ago)

• Vishnu Schist: Oldest exposed rocks; metamorphic, revealing early crust formation.

Paleozoic (541–252 million years ago)

• Tapeats Sandstone: Base of Paleozoic sedimentary sequence.
• Bright Angel Shale: Cambrian; rich in ancient marine fossils.
• Muav Limestone: Middle Cambrian; well-preserved marine fossils.
• Temple Butte Limestone: Mississippian; marks depositional change.
• Redwall Limestone: Mississippian–Pennsylvanian; thick, massive limestone.

Mesozoic (252–66 million years ago)

• Supai Group: Permian; includes Hermit Shale, Coconino Sandstone, Kaibab Limestone.
• Chinle Formation: Triassic; colorful layers with petrified wood (Shinarump Member).

Cenozoic (66 million years ago–present)

• Grand Canyon Supergroup: Includes Toroweap Formation and Kaibab Limestone; records erosion and landscape evolution.

These layers reveal ancient environments, climate shifts, geological processes, and life's evolution.