Professor Publishes Research about Earth's Geological Past

Dr. Rob Thomas, Professor of Geology and Regents’ Professor at Montana Western, was recently published in the journal, “Lithosphere”, a publication of the Geological Society of America, the largest professional organization of geoscientists in the world.

ROB THOMAS

Dr. Rob Thomas, Professor of Geology and Regents’ Professor at Montana Western, was recently published in the journal, “Lithosphere.”

The article addresses fundamental questions about the nature of the tropical western margin of North America around 500 million years ago.

At that time, the Pacific Ocean was just forming and the coastline was located in the northern Rocky Mountains. For years, geologists considered the old coastal margin to have been “passive,” meaning there was no active mountain building or volcanism, similar to the southeastern coast of the United States today.

The paper was co-authored with Paul Link, Mary Todt and David Pearson from the Department of Geosciences at Idaho State University, and is titled “500-490 Ma detrital zircons in Upper Cambrian Worm Creek and correlative sandstones, Idaho, Montana and Wyoming: Magmatism and tectonics within the passive margin.”

By dating zircon crystals collected from the old marine sediments in Montana, Idaho and Wyoming, the research team was able to show that around 500 million years ago, the coastal margin consisted of many mountains and active volcanoes.

The eroded sediments from these highlands were deposited in the surrounding ocean, allowing the team to reconstruct where the old mountains and volcanoes were located, and how they might have impacted animals and plants living in the ocean at that time.

Future work includes using the technique to reconstruct changes in environments during one of the oldest mass extinction events in Earth’s history.

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