Chesapeake Bay Impact Crater Is Home To Oldest Seawater On Earth
November 22, 2013

100 Million Year Old Seawater Discovered Under Chesapeake Bay

[ Watch the Video: Old Water Found In The New World ]

redOrbit Staff & Wire Reports - Your Universe Online

US Geological Survey (USGS) hydrologists drilling into the largest crater in the country have stumbled across an amazing discovery – the oldest body of seawater ever unearthed.

The water, which according to Discovery News is at least 100 million years old, was found over one kilometer beneath Chesapeake Bay in Virginia. The seawater is believed to have come from the earliest days of the Atlantic Ocean and was hidden beneath a more recent, 56-mile-wide impact crater near the bay’s entrance.

The USGS investigators did not realize how old the water was until they completed an analysis of the chemicals it contained. As it turns out, the water held forms of chloride and bromide, as well as other chemicals that helped them determine that the liquid is, in fact, from the Early Cretaceous Period. While older water has been discovered in Canada, the newly discovered crater is now officially the oldest large body of water on Earth.

“Previous evidence for temperature and salinity levels of geologic-era oceans around the globe have been estimated indirectly from various types of evidence in deep sediment cores,” USGS research hydrologist Ward Sanford, lead author of a paper detailing the find which appeared earlier this month in the journal Nature, told Rachel Reilly of the Daily Mail. “In contrast, our study identifies ancient seawater that remains in place in its geologic setting, enabling us to provide a direct estimate of its age and salinity.”

Sanford also told National Geographic’s Christine Dell'Amore that the water was actually in the sediment prior to the impact, and that the even actually helped preserve it by reshuffling the sediment in large blocks. The water in now trapped deep beneath the ground in a region approximately the size of a large lake, some 60 square miles (155 square kilometers) across.

Sanford called the discovery “mind-blowing.” So how did it occur? According to Dell’Amore, the research team began drilling into the crater in 2005 as part of a joint international project, but had to wait several years to discover the actual age of the water they discovered.

By measuring the ratio of chloride and bromide in the drilling samples, they determined that it was ocean water. Next, they compared helium samples in the liquid to those found in other underground water sources in the region, discovering that the gas concentration was approximately one-hundred times higher than that of the other coastal samples. By figuring out the helium accumulation rate, Sanford and his colleagues were able to determine that the water they located was between 100 million and 150 million years old.

“Various theories related to the crater impact have been developed to explain the origin of this high salinity. But, up to this point, no one thought that this was North Atlantic Ocean water that had essentially been in place for about 100 million years,” Jerad Bales, chief scientist for hydrology, told Reilly.

“This study gives us confidence that we are working directly with seawater that dates far back in Earth’s history,” he added. “The study also has heightened our understanding of the geologic context of the Chesapeake Bay region as it relates to improving our understanding of hydrology in the region.”