The scientists used a combination of chemical, isotopic and physical evidence to show that the groundwater is around 100–145 million years old. The water is twice as salty as modern seawater.
Chesapeake Bay was formed about 35 million years ago when a large comet or meteorite blasted a 90-kilometre-wide hole in the ocean floor. It’s one of only a few documented oceanic impact craters.
‘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,’ said lead author Ward Sanford. ‘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.’
‘This study gives us confidence that we are working directly with seawater that dates far back in Earth’s history,’ said Jerad Bales, acting associate director for water at the USGS. ‘The study has also heightened our understanding of the geologic context of the Chesapeake Bay region as it relates to improving our understanding of hydrology in the region.’
This story was published in the January 2014 edition of Geographical Magazine
