Edwin Dinwiddie McKee, a renowned geologist who studied the sedimentary record of the Grand Canyon’s Colorado Plateau geology, has left an indelible mark on the field of geoscience. Over a span of more than 50 years, McKee meticulously documented the stratigraphy and sedimentation of the Grand Canyon’s Cambrian Tonto Group, which holds a wealth of information about the Cambrian Explosion that occurred some 540 million years ago. Despite his groundbreaking work, McKee’s ideas were often dismissed by the scientific community due to a lack of knowledge about plate tectonics and global sea level changes.
In a new study published in the Geological Society of America’s GSA Today journal, a team of researchers led by Carol Dehler of Utah State University and James Hagadorn of the Denver Museum of Nature & Science has revisited McKee’s work using modern stratigraphic, depositional, and paleontological models. Supported by a National Science Foundation grant, the team has developed an updated framework of McKee’s foundational ideas, shedding new light on the geology of the Grand Canyon and the Cambrian period. The researchers’ efforts have revealed new insights into the processes that shaped the Tonto Group’s sedimentary layers.
The team’s research has uncovered three key pathways for deeper understanding of the Tonto Group’s geology. They have found evidence of catastrophic tropical storms, more powerful than today’s hurricanes, and sea-level rise during a period of high global temperatures when the Earth was ice-free. The rocks of the Tonto Group were deposited across every continent on Earth, reflecting a mosaic of shallow marine, coastal, and terrestrial environments. Advanced chronological tools have provided insights into the rapid diversification of trilobites and other Cambrian fauna, offering a glimpse into the dynamic ecosystem of the time.
James Hagadorn, the Tim & Kathryn Ryan Curator of Geology at DMNS, describes studying the Tonto Group as being akin to solving a mystery at a crime scene. While clues are visible in the rock record, unraveling the sequence of events and understanding the complex story of the Grand Canyon’s geology requires time and effort. The researchers’ new model of the Tonto Group provides a more detailed and nuanced understanding of the processes that shaped the sedimentary layers, offering a glimpse into the ancient world of the Cambrian period.
The team’s work in the Grand Canyon, a geological treasure trove that records global changes in climate and tectonics, highlights the ongoing evolution of scientific knowledge. By connecting people to the science of geology through one of the world’s most iconic landscapes, the researchers aim to showcase the iterative nature of scientific inquiry and the importance of understanding Earth’s geological history. Through their efforts to decode the geological mysteries of the Grand Canyon, the team is contributing to a deeper appreciation and understanding of Earth’s ancient past.