Geoscientists utilized modern stratigraphic, depositional, and paleontological models, along with cutting-edge technology, to enhance our understanding of the Cambrian period in the Grand Canyon.
Anyone from the boomer generation to Gen Alpha who has delved into geology has probably been influenced by Edwin Dinwiddie McKee’s significant research on the sedimentary history of the Grand Canyon—even if many aren’t familiar with his name.
The esteemed scientist, who lived from 1906 to 1984, dedicated over 50 years to exploring and documenting the stratigraphy and sedimentation of the Colorado Plateau, particularly focusing on the Cambrian Tonto Group of the Grand Canyon. His enduring principles have shaped the perspectives of many geologists for decades.
According to Carol Dehler, a professor at Utah State University, “The Tonto Group is rich with sedimentary layers and fossils that record the Cambrian Explosion approximately 540 million years ago. This was a time when the initial vertebrates and shelled animals emerged rapidly, coinciding with rising sea levels that inundated continents with new marine life.” She noted that, even though McKee was fascinated by this crucial geological era, his lack of awareness regarding plate tectonics or global sea level changes led to his ideas being often dismissed by his contemporaries.
But what if McKee could have moved through time to access modern stratigraphic, depositional, and paleontological methodologies, data, and technology?
Dehler and her team—James Hagadorn from the Denver Museum of Nature & Science, Frederick Sundberg, Karl Karlstrom, Laura Crossey from the University of New Mexico, Mark Schmitz from Boise State University, and Stephen Rowland from the University of Nevada, Las Vegas—along with their students and interns, have taken advantage of these contemporary tools to reconstruct an enhanced version of McKee’s foundational work. Their findings are detailed in the cover story of the November 2024 issue of the Geological Society of America’s GSA Today journal, which was made available online on October 23, 2024.
This research received funding from a National Science Foundation Division of Earth Sciences grant.
“The Grand Canyon serves as a remarkable Rosetta Stone for geology,” explained Hagadorn, the Tim & Kathryn Ryan Curator of Geology at DMNS. “Our research is helping to decode its complexities, as the rocks in the Grand Canyon reflect global shifts in climate and tectonics. This understanding is crucial for grasping the global stratigraphic record from the Cambrian period.”
He likens studying the Tonto Group to investigating a crime scene.
“You can uncover clues and piece together parts of the story,” Hagadorn commented. “However, determining how everything unfolded and in what order is a painstaking process. Like a crime scene, the Grand Canyon’s rock record is far more intricate than what we currently comprehend, and its narrative is still being developed.”
Dehler emphasizes that their new model reveals three significant avenues for enhanced comprehension.
“The 500-meter-thick layers of the Tonto Group reveal insights about rising sea levels and the impact of catastrophic tropical storms—likely more intense than modern hurricanes—during an era of extremely high temperatures when the planet was devoid of ice,” she articulated.
Dehler further explained that during this period, sea levels were so elevated that Tonto Group rocks were deposited over every continent on Earth, with seas creating a complex mix of shallow marine, coastal, and land environments.
Moreover, she noted that advanced chronological techniques are uncovering fresh details about the rates of sedimentation and the swift diversification of trilobites and other “ugly, cockroach-like creatures.”
“Our research serves as a reminder that science is an ongoing process,” Hagadorn reflected. “Our work in the Grand Canyon, a globally cherished and iconic landscape, brings people closer to the scientific journey in a deeply personal fashion.”
