Utah geology graduate student Jeremiah Bernau operates a coring rig with Ben Marconi while extracting cores from the Bonneville Salt Flats in 2019. Both were graduate students at the University of Utah at the time. Credit: Elliot Jagniecki (Utah Geological Survey).
The salt flats of Bonneville, Utah, have long been assumed to have formed when the ancient lake of the same name dried up 13,000 years ago. But new research from the University of Utah gutted that narrative, determining that these crusts didn’t form until several thousand years after Lake Bonneville disappeared, which could have important implications for the management of this an element that has been shrinking for decades, much to the dismay of the racing community. and others who revere the salt pan 100 miles west of Salt Lake City.
This salt beach, spanning 40 square miles of the Great Basin Desert, perfectly flat and white, has served as the scene for land speed records and the backdrop to memorable scenes in numerous films, including “Buckaroo Banzai” and “Pirates of the Caribbean”. Caribbean.”
Drawing on radiocarbon analysis of pollen found in salt cores, the study, published in the journal Quaternary Researchconcludes that salt began to accumulate between 5,400 and 3,500 years ago, demonstrating that this geological feature is not a permanent feature of the landscape.
“This now gives us an idea of how the landscape of the Bonneville Salt Flats responds to environmental changes. Originally, we thought this salt formed here just past Lake Bonneville and was “a static landscape over the past 10,000 years,” said the study’s lead author. , Jeremiah Bernau, former University graduate student in geology.
“This data shows us that that’s not the case, that during a very dry period over the last 10,000 years, we actually saw a lot of erosion and then accumulation of gypsum sand. And as the The climate was becoming cooler and wetter, so the salt began to accumulate.
And what’s even more intriguing, researchers say, is that the sediments immediately beneath the salt are much older, predating even the existence of Lake Bonneville. In other words, the ancient lake bed has largely been blown away, indicating that this landscape is much more dynamic than previously thought.
“We can show that a lot of the material was removed before the salt arrived,” said lead author Brenda Bowen, a professor of geology and chair of the Department of Atmospheric Sciences who directs the Center on Global Change and the sustainability of the University. “It’s really interesting when you think about what’s happening now with the exposed beds of the Great Salt Lake and the risk of the dust being washed away and eroded.”
Neighboring Great Salt Lake, a remnant of Lake Bonneville, has receded significantly over the past two decades thanks to drought and decades of upstream water diversion. The research offers a potential prediction of what could happen if the Great Salt Lake continues to shrink.
Since 1960, scientists have monitored the Bonneville Salt Flats, under lease agreements and management plans overseen by the federal Bureau of Land Management. The playa has lost about a third of its salt volume over the past six decades.
Today, the crusts measure 5 feet at their thickest point and cover an area 5 by 12 miles at the foot of the Silver Island Mountains. Bowen began measuring salt in 2016 with a research team that included Bernau, who joined the Utah Geological Survey after completing his doctorate.
But they went deeper than others before, drilling into sediments beneath the salt that are difficult to break through.
“Salt is pretty brittle,” Bowen said. “You generally can’t use fluids or water (to aid drilling) because it will dissolve the sediment.”
Instead, they used sonic drilling, which uses vibrations.
“Once you get to the mud under the salt,” she said, “it’s like toothpaste and it slides right through.”
Bowen and Bernau collaborated with the Records of Environmental Disturbance (or RED) laboratory in the University’s geography department to drill additional cores in 2018 and 2020, this time using a device called a “vibracorer”, built by Isaac Hart, a former construction worker and welder who was then a graduate student in anthropology.
The equipment consists of a 21-foot-long irrigation tube attached to a concrete mixer motor.
“The vibration of the motor helps drive the tube into the ground if the sediment is relatively fine and soft (like the bottom of the Lake Bonneville basin), after which we fill the tube with water and cap it to create a vacuum for that the dirt doesn’t fall out of the tube when we remove it from the ground,” Hart, co-author of the study, said in an email. He is now field director for the nonprofit American Center for Mongolian Studies.
Bernau added: “This method was manually laborious, but we extracted some truly magnificent cores.”
They shared these cores, varying in length from 10 to 13 feet, with study co-author Charles “Jack” Oviatt, professor emeritus of geology at Kansas State University and a leading expert on the Pleistocene lake beds, particularly that of Lake Bonneville. After examining the sediments, Oviatt concluded that they bore little resemblance to the bed of Lake Bonneville elsewhere.
“It really made us feel like we had something interesting on our hands,” recalls Bernau, who now works for private industry in Texas. To make sense of the cores, researchers first had to identify the age of the salt crusts and their underlying sediments.
Scientists can determine this. Applying this technique to sediments, the researchers found dates dating back more than 40,000 years, older than Lake Bonneville itself, suggesting the earlier presence of intermittent lakes.
Dating the overlying salt crusts was more difficult because radiocarbon dating requires the analysis of organic material. However, by examining the salt cores under a microscope, the researchers discovered what they needed to carbon-15 date the salt: tiny pollen grains.
The team also examined sediment structures, mineralogy, diatoms and geochemistry to characterize the depositional records. Isotopic ratio measurements of gypsum and strontium carbonate were used to determine the water sources that transported sediment to the salt pans.
“We put all of our tools into this study to get as solid an understanding as possible of how this environment was changing over time,” said Bowen, whose study builds a revisionist history of this place.
Lakes have come and gone for tens of thousands, even hundreds of thousands of years, in response to climate change, disappearing and reappearing as conditions alternate between wet and dry periods.
The data indicates that the area that is now home to the salt flats was home to a series of three shallow lakes between 45,000 and 28,000 years ago, before the arrival of Lake Bonneville. 13,000 years ago, the lake bed was exposed to wind erosion.
Three to six feet of sediment was blown away before water returned about 8,300 years ago, bringing the brines that eventually formed the salt pans we see today. The study shows that the Bonneville Salt Flats are more ephemeral than many think, offering insight into how this special place might be managed differently.
“Sometimes we adapt to the current landscape thinking this is what it has to be,” Bowen said, “but in reality it has to be able to adapt and change.”
More information:
Jeremiah A. Bernau et al, Lateral and temporal constraints on the depositional history of the Bonneville Salt Flats, Utah, USA, Quaternary Research (2024). DOI: 10.1017/qua.2023.79
Provided by University of Utah
Quote: Utah’s Bonneville Salt Flats have long been in flux, new research shows (February 21, 2024) retrieved February 21, 2024 from
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