ProPublica's Abrahm Lustgarten reports:

New research has concluded that salty, mineral-rich fluids deep beneath Pennsylvania's natural gas fields are likely seeping upward thousands of feet into drinking water supplies.

Though the fluids were natural and not the byproduct of drilling or hydraulic fracturing, the finding further stokes the red-hot controversy over fracking in the Marcellus Shale, suggesting that drilling waste and chemicals could migrate in ways previously thought to be impossible.

The study, conducted by scientists at Duke University and California State Polytechnic University at Pomona and released today in the Proceedings of the National Academy of Sciences, tested drinking water wells and aquifers across Northeastern Pennsylvania. Researchers found that, in some cases, the water had mixed with brine that closely matched brine thought to be from the Marcellus Shale or areas close to it.

No drilling chemicals were detected in the water, and there was no correlation between where the natural brine was detected and where drilling takes place.

Still, the brine's presence – and the finding that it moved over thousands of vertical feet -- contradicts the oft-repeated notion that deeply buried rock layers will always seal in material injected underground through drilling, mining, or underground disposal.

"The biggest implication is the apparent presence of connections from deep underground to the surface," said Robert Jackson, a biology professor at the Nicholas School of the Environment at Duke University and one of the study's authors. "It's a suggestion based on good evidence that there are places that may be more at risk."

The study is the second in recent months to find that the geology surrounding the Marcellus Shale could allow contaminants to move more freely than expected. A paper published by the journal Ground Water in April used modeling to predict that contaminants could reach the surface within 100 years – or fewer if the ground is fracked.

Last year, some of the same Duke researchers found that methane gas was far more likely to leak into water supplies in places adjacent to drilling.

Today's research swiftly drew criticism from both the oil and gas industry and a scientist on the National Academy of Science's peer review panel. They called the science flawed, in part because the researchers do not know how long it may have taken for the brine to leak. The National Academy of Sciences should not have published the article without an accompanying rebuttal, they said.

"What you have here is another case of a paper whose actual findings are pretty benign, but one that, in the current environment, may be vulnerable to distortion among those who oppose this industry," said Chris Tucker, a spokesman for the gas industry trade group Energy In Depth. "What's controversial is attempting to argue that these migrations occur as a result of industry activities, and on a time scale that actually matters to humanity."

Another critic, Penn State University geologist Terry Engelder, took the unusual step of disclosing details of his review of the paper for the National Academy of Sciences, normally a private process.

In a letter written to the researchers and provided to ProPublica, Engelder said the study had the appearance of "science-based advocacy" and said it was "unwittingly written to enflame the anti-drilling crowd."

In emails, Engelder told ProPublica that he did not dispute the basic premise of the article – that fluids seemed to have migrated thousands of feet upward. But he said that they had likely come from even deeper than the Marcellus – a layer 15,000 feet below the surface – and that there was no research to determine what pathways the fluids travelled or how long they took to migrate. He also said the Marcellus was an unlikely source of the brine because it does not contain much water.

"There is a question of time scale and what length of time matters," Engelder wrote in his review. In a subsequent letter to the Academy's editors protesting the study, he wrote that "the implication is that the Marcellus is leaking now, naturally without any human assistance, and that if water-based fluid is injected into these cross-formational pathways, that leakage, which is already ‘contaminating' the aquifers with salt, could be made much worse."

Indeed, while the study did not explicitly focus on fracking, the article acknowledged the implications. "The coincidence of elevated salinity in shallow groundwater... suggests that these areas could be at greater risk of contamination from shale gas development because of a preexisting network of cross-formational pathways that has enhanced hydraulic connectivity to deeper geological formations," the paper states.

For their research, the scientists collected 426 recent and historical water samples -- combining their own testing with government records from the 1980s -- from shallow water wells and analyzed them for brine, comparing their chemical makeup to that of 83 brine samples unearthed as waste water from drilling sites in the Marcellus Shale.

Nearly one out of six recent water samples contained brine near-identical to Marcellus-layer brine water.

Nevertheless, Jackson, one of the study's authors, said he still considers it unlikely that frack fluids and injected man-made waste are migrating into drinking water supplies. If that were happening, those contaminants would be more likely to appear in his groundwater samples, he said. His group is continuing its research into how the natural brine might have travelled, and how long it took to rise to the surface.

"There is a real time uncertainty," he said. "We don't know if this happens over a couple of years, or over millennia."

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  • In this file photo from Oct. 14, 2011, a drilling rig is seen in Springville, Pa. State regulators blamed faulty gas wells drilled for leaking methane into the groundwater in nearby Dimock, Pa. It was the first serious case of methane migration said to be related to the Pennsylvania Marcellus Shale gas field drilling boom. (AP Photo/Alex Brandon, FILE)

  • British police secure the area where demonstrators erected a mock fracking rig with a banner reading 'No fracking in the UK' in a protest against hydraulic fracturing for shale gas outside the Houses of Parliament in London on December 1, 2012. AFP PHOTO / JUSTIN TALLIS

  • SPRINGVILLE, PA - JANUARY 18: A truck with the natural gas industry, one of thousands that pass through the area daily, drives through the countryside to a hydraulic fracturing site on January 18, 2012 in Springville, Pennsylvania. (Photo by Spencer Platt/Getty Images)

  • SAN FRANCISCO, CA - MAY 30: Protestors stage a demonstration against fracking in California outside of the Hiram W. Johnson State Office Building on May 30, 2013 in San Francisco, California. Dozens of protesters with the group Californians Against Fracking staged a protest outside of California Gov. Jerry Brown's San Francisco offices demanding that Gov. Brown ban fracking in the state. (Photo by Justin Sullivan/Getty Images)

  • People demonstrate on August 3, 2013 in La Petite Brosse, near Jouarre, outside Paris, to protest against an exploratory oil shale drilling, considering that it opens the door to the exploration of shale gas in the Parisian Basin. Banner reads 'Stop gas and oil shale'. AFP PHOTO / PIERRE ANDRIEU

  • In this Nov. 26, 2012 photo, Steve Lipsky demonstrates how his well water ignites when he puts a flame to the flowing well spigot outside his family's home in rural Parker County near Weatherford, Texas. The U.S. Environmental Protection Agency had evidence a gas company's drilling operation contaminated Lipsky's drinking water with explosive methane, and possibly cancer-causing chemicals, but withdrew its enforcement action, leaving the family with no useable water supply, according to a report obtained by The Associated Press. The EPA's decision to roll back its initial claim that hydraulic fracturing, or “fracking,” operations had contaminated the water is the latest case in which the federal agency initially linked drilling to water contamination and then softened its position, drawing criticism from Republicans and industry officials who insisted they proved the agency was inefficient and too quick to draw conclusions. (AP Photo/LM Otero)

  • In this file photo of Jan. 17, 2013, Yoko Ono, left, and her son Sean Lennon visit a fracking site in Franklin Forks, Pa., during a bus tour of natural-gas drilling sites in northeastern Pennsylvania. Ono and Lennon have formed a group called “Artists Against Fracking,” which has become the main celebrity driven anti-fracking organization. (AP Photo/Richard Drew, File)

  • In this March 29, 2013 file photo, a worker checks a dipstick to check water levels and temperatures in a series of tanks at a hydraulic fracturing operation at a gas drilling site outside Rifle, Colorado. (AP Photo/Brennan Linsley)

  • In this March 29, 2013 file photo, a worker switches well heads during a short pause in the water pumping phase, at the site of a natural gas hydraulic fracturing and extraction operation outside Rifle, in western Colorado. (AP Photo/Brennan Linsley)

  • In this March 29, 2013 file photo, workers tend to a well head during a hydraulic fracturing operation at a gas well outside Rifle, in western Colorado. (AP Photo/Brennan Linsley)

  • Josh Fox, director of the anti-fracking, Oscar-nominated documentary “Gasland” testifies during a House Committee hearing on oil drilling, "fracking" legislation at the Illinois State Capitol Tuesday, May 21, 2013, in Springfield, Ill. (AP Photo/Seth Perlman)

  • This is a Thursday Aug. 15, 2013 image of the Cuadrilla exploration drilling site in Balcombe, southeast England. (AP Photo/Gareth Fuller/PA)

  • A child plays near a farmers' protest in an area where oil company Chevron plans to put a drilling rig exploring for shale gas in the south-eastern Polish village of Zurawlow on June 11, 2013. AFP PHOTO / JANEK SKARZYNSKI

  • Protesters hold a banner during a protest outside of the Momentive resin plant, Monday, July 8, 2013, in Morganton, N.C. Dozens of environmental activists blocked a chemical plant Monday to protest against the company's sale of products used in the natural gas drilling process called hydraulic fracturing, or fracking. (AP Photo/The News Herald, Mary Elizabeth Robertson)

  • A fracking rig exploring for shale gas of oil company Chevron on June 11, 2013 in a village of Ksiezomierz in south-eastern Poland. AFP PHOTO / JANEK SKARZYNSKI

  • People demonstrate on August 3, 2013 in La Petite Brosse, near Jouarre, outside Paris, to protest against an exploratory oil shale drilling, considering that it opens the door to the exploration of shale gas in the Parisian Basin. AFP PHOTO / PIERRE ANDRIEU

  • Opponents of hydraulic fracturing in New York state attend a news conference and rally against hydraulic fracturing, also known as fracking, on January 11, 2012 in New York City. (Photo by Spencer Platt/Getty Images)

  • Eric Weltman of Food & Water Watch attends a news conference and rally against hydraulic fracturing, also known as fracking, in New York State on January 11, 2012 in New York City. (Photo by Spencer Platt/Getty Images)

  • Opponents and supporters of gas-drilling, or fracking, walk into the last of four public hearings on proposed fracking regulations in upstate New York on November 30, 2011 in New York City. (Photo by Spencer Platt/Getty Images)

  • Engineers on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers at work on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • General views of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers look at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • A lump of shale rock on display at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers at work on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Drill heads on display at the entrance to the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • An engineer displays a lump of shale rock at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Actor/director Mark Ruffalo (C) speaks at the Hydraulic Fracturing prevention press conference urging the protection of the drinking water source of 15 million Americans at Foley Square on April 25, 2011 in New York City. (Photo by D Dipasupil/Getty Images)

  • (L-R) Actor/director Mark Ruffalo, Denise Katzman, Wenonah Hauter, and Water Defense co-founder/campaign director Claire Sandberg attend the Hydraulic Fracturing prevention press conference urging the protection of the drinking water source of 15 million Americans at Foley Square on April 25, 2011 in New York City. (Photo by D Dipasupil/Getty Images)