Probing the Ancient History of the Northern Rockies

April 19th (Tuesday), 6 p.m., Via Zoom (online) & Live at St. John’s Episcopal Church – Open to Public.
Presentation: “Probing the Ancient History of the Northern Rockies”
Presented by Kendra Murray, Idaho St. Univ. 

When you look at Mt. Moran, the Flathead Sandstone atop the mountain is about 500 million years old. But, the igneous and metamorphic rocks immediately beneath it are more than 2 billion years older! The contact between the Flathead and the rocks it was deposited upon is a profound gap in the geologic record and a local example of what is called “The Great Unconformity”, which is found on every continent on Earth. Despite early (18th century) recognition that much of Earth’s history is missing from the geologic record across such unconformities, geologists have had no choice but to rely on the surviving record to reconstruct the evolution of Earth’s tectonics, biosphere, and climate. As a result, gaps in the rock record, particularly those that span more than one billion years like “The Great Unconformity”, correspond with profound knowledge gaps in the understanding of our planet. Exciting recent advances in the new field of deep-time thermochronology have demonstrated that the deposition of sediments and erosion of rocks—even in areas where rocks are no longer preserved for us to observe—makes a thermal imprint on underlying ‘basement’ rocks that can persist for hundreds of millions of years. Thus, we can now use the temperature history of basement rocks as a robust proxy for events and processes in the deep past and decipher previously inaccessible times in Earth’s history. In this talk, I’ll present my recent work applying this method in Colorado’s Front Range, which reveals an exciting story of ancient tectonics. I’ll also preview a new project taking a similar approach here in the Northern Rockies. We are planning to work at the spectacular Great Unconformity exposures in the Tetons, where more than two billion years—nearly half of Earth’s history—is missing from the rock record and thus our understanding of the region’s geology.

Topic: Probing the Ancient History of the Northern Rockies
Time: Apr 19, 2022 06:00 PM Mountain Time (US and Canada)

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