Utah's Bonneville Salt Flats have been in flux for a long time.

Utah geology graduate student Jeremiah Bernau, top, operates a coring device with Ben Marconi in 2019 extracting core from the Bonnell Salt Flats. Both were graduate students at the University of Utah at the time. Credit: Elliot Jagnecki (Utah Geological Survey).

It has long been assumed that Utah’s Bunyol Salt Flats were formed when the lake of its ancient namesake dried up 13,000 years ago. But new research from the University of Utah undermines the narrative that these crusts weren’t laid down until thousands of years after Lake Bonneville disappeared, which could have important implications for the management of the feature that spanned decades. The shrinking racing community is frustrated. and others who revere the salt pans 100 miles west of Salt Lake City.

This salt flat, spread over 40 square miles of Great Basin desert, perfectly level and white, has served as a stage for land speed records and as the backdrop for memorable scenes in several movies, including “Bakaro Banzai.” and “Pirates of the” included. Caribbean.”

Relying 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, showing how this geological feature is not a constant reality on the landscape.

“This now gives us a record of how the landscape of the Bonneville salt flats is responding. . Originally, we thought this salt formed here after Lake Bonneville and that it was a static landscape over the last 10,000 years,” said the study’s lead author, Jeremiah Bernau, a former U graduate student in geology.

“These data show us that’s not the case. In a very dry period in the last 10,000 years, we actually saw a lot of erosion and then deposition of gypsum sands. And as the climate got cooler and wetter. was happening, then the salt began to accumulate.”

And even more interesting, according to the researchers, the sediments beneath the salt are very old, even predating the existence of Lake Bonneville. In other words, the old lake bed was largely blown away, indicating that the landscape was much more dynamic than previously thought.

“We can show that a lot of material was removed before the salt arrived,” said senior author Brenda Bowen, professor of geology and chair of the Department of Environmental Sciences at the UK Center for Global Change and Sustainability. is the head of “It’s really interesting when we think about what’s happening right now with the exposed lake beds of the Great Salt Lake and the potential for dust to blow up and end up.”

The nearby Great Salt Lake, a remnant of Lake Bonneville, has shrunk over the past two decades thanks to drought and decades of diversion of upper waters. The research offers a possible prediction of what could happen if the Great Salt Lake continues to shrink.

Since the 1960s, scientists have been monitoring the Bonneville Salt Flats, as part of 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 are 5 feet at their thickest point and cover an area of ​​5 by 12 miles at the foot of the Silver Island Mountains. Bowen began measuring the 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 ever before, drilling holes in the sediment beneath the salt, which is harder to get through.

“Salt is quite brittle,” Bowen said. “You can’t use fluids or water normally [to aid in drilling] Because it will dissolve the sediment.”

Instead, they used sonic drilling, which uses vibrations.

“Once you get to the mud under the salt,” he said, “it’s like toothpaste and it just slides right off.”

Bowen and Bernau collaborated with the U Geography Department’s Records of Environmental Disturbance (or RED) lab to drill additional cores in 2018 and 2020, this time using a device called a “vibracorer” from a former construction worker. and was made by Isaac Hart, a welder. He 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 allows the tube to be pushed down into the ground if the sediment is relatively fine and soft (like the floor of the Lake Bunyol basin), after which we fill the tube with water and seal it off. Create a vacuum so that the dirt doesn’t fall out of the tube when we pull it out of the ground,” Hart, co-author of the study, said in an email. He is now the field director of the international nonprofit American Center for Mongolian Studies.

“The method was manually laborious, but we got really beautiful covers,” added Bernau.

They shared the cores, which ranged from 10 to 13 feet in length, to Charles “Jack” Ovitt, study co-author, professor emeritus of geology at Kansas State University and an expert in Pleistocene lake beds, particularly Lake Bonnell. With a leading expert. After examining the sediments, Ovett concluded that they bore little resemblance to the bed of Lake Bonneville elsewhere.

“That really signaled to us that we had something interesting on our hands,” recalls Bernau, who now works for private industry in Texas. To understand the core, the researchers first had to identify the salt crusts and the ages of their underlying sediments.

Scientists can determine. Applying this technique to the sediments, the researchers found dates older than 40,000 years, older than Lake Bonneville itself, suggesting the earlier presence of intermittent lakes.

More salt crusts were more difficult to date because radiocarbon dating requires organic material to be analyzed. However, in examining the salt cores under a microscope, the researchers found what they needed to carbon date the salt: minute grains of pollen.

The team also examined sedimentary structures, minerals, diatoms and geochemistry to characterize the accumulated record. Gypsum and carbonate strontium isotope ratios were measured to determine the sources of water that transported the sediments to the salt flats.

“We put all our tools into this study to get as strong an understanding as possible of how this environment is changing over time,” said Bowen, whose study is one of the most important for the space. Creates a revision date.

Lakes have come and gone for millions, if not thousands, of years in response to climate change, disappearing and reappearing as conditions alternate between wet and dry periods.

The data show that the area now supporting the salt flats hosted a series of three shallow lakes between 45,000 and 28,000 years ago, before the arrival of Lake Bonneville. After 13,000 years ago, the lake bed suffered wind erosion.

About 8,300 years ago, three to six feet of sediment was blown away before the water receded, forming the salt water. We see today. The study shows that the Bonneville salt flats are more temporary than many people realize, offering insight into how this special place could be managed differently.

“Sometimes we manage the existing landscape thinking it needs to,” Bowen said, “but actually, it needs to be able to adapt and change.”

More information:
Jeremiah A. Bernau et al, Background and temporal constraints on the depositional history of the Bonnell Salt Flats, Utah, USA, Quaternary Research (2024). DOI: 10.1017/budh.2023.79

Provided by
University of Utah

Reference: Utah’s Bonneville Salt Flats Long Lasting, New Study Shows (2024, February 21) February 21, 2024 https://phys.org/news/2024-02-utah-bonneville-salt-flats- Retrieved from flux.html

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