(NEWSER) – The remains of a salty ocean ancient enough for dinosaurs to have drowned in it have been found deep in the sediment under the Chesapeake Bay. The seawater—believed to be 100 to 150 million years old—was isolated, trapped a half-mile underground, and preserved with the help of an asteroid that smashed into the area around 35 million years ago, creating a huge crater. The watery fossil holds around 3 trillion gallons, and is "the oldest large body of ancient seawater in the world," according to government hydrologists who made the amazing find while mapping the ancient crater under Virginia's Cape Charles. "We weren't looking for ancient seawater," the lead researcher tells the Washington Post, calling the find "surprising."
The underground seawater, twice as salty as that found in today's oceans, comes from a time when "the Atlantic was a smaller ocean," the lead researcher tells NPR. "It had only been in existence for about 50 million years and it was isolated from the rest of the world's oceans. It had its own salinity and its salinity was changing at a different rate and by different amounts from the rest of the global oceans." But while the distinct chemical signature of the Cretaceous-era ocean has been preserved, the remnants are scattered among countless cracks and pores, meaning any ancient ocean life is very unlikely to have survived