Telling time at Grand Canyon National Park: 2020 update

Grand Canyon National Park's geological record, spanning billions of years, reveals distinct rock formations with precisely dated ages, updating previous stratigraphic nomenclature and numeric age determinations. The study identifies three primary rock sets: the Vishnu Basement Rocks (1,840–1,375 million years ago), the Grand Canyon Supergroup (729–1,255 million years ago), and the Layered Paleozoic Rocks (270–530 million years ago). These sets are separated by unconformities, including the Great Unconformity, which represents significant erosion periods. The research provides numeric ages for all groups and formations, incorporating recent scientific advancements to offer a comprehensive reference for geologic history.

Karlstrom, K., Crossey, L., Matthis, A., & Bowman, C. (2021). Telling time at Grand Canyon National Park: 2020 update (, Ed.). National Park Service. https://doi.org/10.36967/nrr-2285173