Prehistoric Atlantic Ocean Was Twice As Salty As Today

By Becky Lang | November 13, 2013 1:06 pm


It’s been 35 million years since a large meteorite slammed into the Earth, cracking bedrock beneath what is now the Chesapeake Bay. The impact left pores that collected groundwater from beneath it. Now researchers have dated that water to between 100 million and 145 million years old, and report that it’s twice the salinity of modern sea water.

Salinity levels of ancient oceans tend to be estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. These analyses had hinted that groundwater beneath the Chesapeake was highly saline.

Now for the first time scientists have extracted and tested the ancient water directly. They collected water from core samples taken from more than a mile deep by using a centrifuge to extract the liquid.

Ocean, Trapped in Time

Chemical tests on the water indicated it had been undisturbed for 100-145 million years—making it a direct remnant of Early Cretaceous North Atlantic seawater. It’s the oldest “sizeable” body of seawater yet discovered, according to the USGS. The research appears today in Nature.

However the water wouldn’t have been preserved all these years if it weren’t for a fortuitous meteorite impact, NBC News explains:

Ordinarily, water from such underground reservoirs drain away through underground channels, but a meteorite that crashed into the Chesapeake Bay 35 million years ago “broke up the plumbing” that would have flushed the pool out, Ward Sanford, a hydrologist at the United States Geological Survey, who was part of the drilling team, told NBC News.

Soon after, however, the North Atlantic Ocean lost its super-salinity—leaving just this pocket of evidence—according to LiveScience:

Sanford and his colleagues suggest that by the start of the late Cretaceous Period, roughly 100 million years ago, water in the widening North Atlantic Ocean was more diluted, with salinity levels that are similar to that of modern seawater.


Image by Jan Miko / Shutterstock



CATEGORIZED UNDER: Environment, top posts
MORE ABOUT: earth science, ocean
  • Mikels Skele

    But why?

    • Neil

      Exactly, I don’t think there was an answer. Weird coming from a Science website.

  • ObeyMyBrain

    Wait it says that normally the water would have drained away through underground channels. If the impact 35 million years ago broke up those channels, that means that water had been sitting there for 65-110 million years without draining away. What did the impact do again?

    • Kaito

      The impact made a new pocket which didn’t have any of those channels, most likely

  • Ward Sanford

    Off and on during the last ice age (1,000,000 years) fresh water partially flushed out some of the other Coastal Plain aquifer sediments during low sea level stands. The asteroid impact broke up those aquifers and so the saline water in the crater was trapped and did not flush out like most of the rest of the coastal plain. That type of flushing was not occurring before the impact, allowing the more ancient seawater to stay there for a much longer time period.

  • Christos Themistocles Fotinako

    The explanation for the different levels of salinity between now and 100 million years ago needs to be taken with a grain a salt – excuse the pun.


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