This article series is adapted from the Natural Resources Report Telling Time at Grand Canyon: 2020 Update. Articles in the series, including numeric ages of Grand Canyon rocks, geoheritage of Grand Canyon’s rock record, and missing time at Grand Canyon as well as a full glossary and list of references.
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Grand Canyon National Park
Article 1: Telling Time at Grand Canyon National Park
Geologic time is essential to understanding Grand Canyon. This exploration of geologic time at Grand Canyon consists of a series of web articles that provides numeric ages for rocks exposed at Grand Canyon and provides supporting geologic information. Read more
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Grand Canyon National Park
Article 2: Numeric Ages of Grand Canyon Rocks
Numeric ages based on current geologic research are presented for each of the rock units exposed in Grand Canyon National Park. Read more
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Grand Canyon National Park
Article 3: Grand Canyon’s Three Sets of Rocks
Grand Canyon’s three sets of rocks are informal groupings of its rock record into main packages of rocks based on their age, stratigraphic relationships, and shared geologic history. Read more
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Grand Canyon National Park
Article 4: Vishnu Basement Rocks
The Vishnu Basement Rocks include the oldest rocks at Grand Canyon. These Precambrian (Proterozoic) igneous and metamorphic rocks formed between 1375 and 1840 million years ago. Read more
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Grand Canyon National Park
Article 5: Grand Canyon Supergroup
The Grand Canyon Supergroup is a thick sequence of mostly sedimentary rocks deposited during the Proterozoic (between 729 and 1255 million years ago) and exposed in places in the eastern part of Grand Canyon. Read more
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Grand Canyon National Park
Article 6: Layered Paleozoic Rocks
The Layered Paleozoic Rocks are the nearly horizontal sedimentary units exposed in the upper portion of Grand Canyon’s rock walls. They were deposited during the Paleozoic Era between about 270 and 510 million years ago. Read more
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Grand Canyon National Park
Article 7: Geoheritage of Grand Canyon National Park’s Rock Record
Grand Canyon is one of the most superlative geologic locales in the world with a rock record spanning approximately one third of the planet’s history and important records of the Proterozoic Eon and Paleozoic Era. Read more
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Grand Canyon National Park
Article 8: Missing Time at Grand Canyon National Park
Significant unconformities, or gaps in the rock record that represent periods of missing time, are present between each of Grand Canyon’s three sets of rocks. Read more
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Grand Canyon National Park
Article 9: Geologic Timescale, Geologic Dating Techniques, and Numeric Ages
An understanding of the ways geologists tell time is important for understanding the numeric ages of Grand Canyon rocks. Read more