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Oldest Large Body of Ancient Seawater Identified under Chesapeake Bay Active

By Chesapeake Bay Activities January 24, 2017

USGS scientists have determined that high-salinity groundwater found more than 1,000 meters (0.6 mi.) deep under the Chesapeake Bay is actually remnant water from the Early Cretaceous North Atlantic Sea and is probably 100-145 million years old. This is the oldest sizeable body of seawater to be identified worldwide.

Twice as salty as modern seawater, the ancient seawater was preserved like a prehistoric fly in amber, partly by the aid of the impact of a massive comet or meteorite that struck the area about 35 million years ago, creating Chesapeake Bay.

"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 Ward Sanford, a USGS research hydrologist and lead author of the investigation. "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, W., Doughten, M., Coplen, T. et al. Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater. Nature 503, 252–256 (2013). https://doi.org/10.1038/nature12714 

  • Overview

    USGS scientists have determined that high-salinity groundwater found more than 1,000 meters (0.6 mi.) deep under the Chesapeake Bay is actually remnant water from the Early Cretaceous North Atlantic Sea and is probably 100-145 million years old. This is the oldest sizeable body of seawater to be identified worldwide.

    Twice as salty as modern seawater, the ancient seawater was preserved like a prehistoric fly in amber, partly by the aid of the impact of a massive comet or meteorite that struck the area about 35 million years ago, creating Chesapeake Bay.

    "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 Ward Sanford, a USGS research hydrologist and lead author of the investigation. "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, W., Doughten, M., Coplen, T. et al. Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater. Nature 503, 252–256 (2013). https://doi.org/10.1038/nature12714