Pre-Cenozoic Stratigraphy and Paleogeography of the Grand Canyon, AZ

Amanda D’Elia

Abstract: The Grand Canyon is a geologic wonder offering a unique glimpse into the early geologic history of the North American continent. The rock record exposed in the massive canyon walls reveals a complex history spanning more than a billion years of Earth’s history. The earliest known rocks of the Southwestern United States are found in the basement of the Grand Canyon and date back to 1.84 billion years old (Ga). The rocks of the Canyon can be grouped into three distinct sets based on their petrology and age (Figure 1). The oldest rocks are the Vishnu Basement rocks exposed at the base of the canyon and in the granite gorges. These rocks provide a unique clue as to the early continental formation of North America in the early Precambrian. The next set is the Grand Canyon Supergroup, which is not well exposed throughout the canyon, but offers a glimpse into the early beginnings of before the Cambrian explosion. The final group is the Paleozoic strata that make up the bulk of the Canyon walls. Exposure of this strata provides a detailed glimpse into North American environmental changes over nearly 300 million years (Ma) of geologic history. Together these rocks serve not only as an awe inspiring beauty but a unique opportunity to glimpse into the past.