Groundwater at depths of several hundred meters or more can be hundreds of millions of years old and are often thought to be stagnant and isolated from the atmosphere and the water cycle, a reason why these underground areas are targeted as potential sites for underground waste disposal, Ferguson said. .
“But things are more dynamic than we thought,” said Ferguson, a professor of civil, geological and environmental engineering in USask’s College of Engineering and co-author of the journal article. Geophysical research papers.
The paper describes the surprising findings in the Paradox Basin, located in southeastern Utah and southwestern Colorado, where the research team found unexpectedly young groundwater at a depth where aquifers are conventionally found much older
“That’s what was so exciting about this study,” said co-author Dr. Jennifer McIntosh (Ph.D.), University of Arizona (U of A) Distinguished Scholar in the Department of Hydrology and Atmospheric Sciences and adjunct professor at USpregunta.
“We expected to find that groundwater would age progressively as it goes deeper,” McIntosh said. “Instead, we found million-year-old groundwater, which is relatively young, about three kilometers below the surface in sediments that are hundreds of millions of years old.”
McIntosh led the team in which Ferguson was the lead in physical hydrology. Dr. Jihyun Kim (Ph.D.), now a graduate student at the University of Calgary and former Ph.D. candidate that McIntosh and Ferguson co-supervised, was the first author.
This study is one of the first to use a relatively new krypton-81 technique to date deep groundwater. Unlike carbon-14, which scientists use to determine the age of materials up to 40,000 years old, the longer decay period of radioactive krypton 81 can be used to calculate the age of water up to 1, 2 million years.
The study’s findings are linked to rapid geological changes over the past three million to 10 million years in the Colorado Plateau, where the dramatic incision (undercutting or erosion beneath the river bed) of the great Colorado River, which formed the Grand Canyon. clean up old groundwater.
Before the incision of the Colorado River, the Colorado Plateau was relatively flat, and seawater from the Paleozoic Era (500 million to 250 million years ago) was trapped within the sediments for hundreds of millions of years. years, Ferguson said.
“Essentially, what the incision did was create drainages that allowed surface water to penetrate and carry the ancient highly saline waters of the aquifers both above and below the salt deposits into the center of the groundwater system deep”.
This research shows that landscape evolution can produce dramatic change in the subsurface environment in a few million years, a short period of geologic time, McIntosh said. The study is useful because the same techniques can be applied to characterize sites elsewhere to learn how they are connected to the atmosphere and surface, he said.
A newly funded project on the Colorado Plateau led by McIntosh is also examining the relationship between subsurface hydrology and life in more detail, testing the hypothesis that deep circulation of water from the surface may have re-inoculated microbial life in sediments that were deeply buried and buried. sterilized by high temperatures in the geological past.
The team plans to extend this work to other regions, including the Canadian prairies, where Ferguson said geological events, such as the uplift of the Rocky Mountains 80 to 50 million years ago, and the glaciation that covered much of ‘North America from about 2.8 million years ago. would have caused major hydrological changes.
“Especially from a Saskatchewan perspective, we’re thinking about the different ways we can use the subsoil, whether it’s to store oil and gas fluids, or to sequester carbon, we’re going to have those legacies going forward,” he said. “I don’t think we’ve really scrutinized these systems the way we could or should.”
Scientists measure new depths at bottom of hydrologic cycle More information: Ji-Hyun Kim et al, Krypton-81 Dating Constrains Timing of Deep Groundwater Flow Activation, Geophysical research papers (2022). DOI: 10.1029/2021GL097618 Provided by University of Saskatchewan
Citation: Discovery of ‘young’ deep groundwater tells surprising story (2022, July 20) Retrieved July 22, 2022 from
This document is subject to copyright. Other than any fair dealing for private study or research purposes, no part may be reproduced without written permission. Content is provided for informational purposes only.