A reservior of 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, according to U.S. Geological Survey scientists.
USGS scientists believe the find 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 the Chesapeake Bay.
The Chesapeake Bay impact crater is one of only a few oceanic impact craters that have been documented worldwide. According to USGS, the crater was formed about 35 million years ago when a huge rock or chunk of ice traveling through space blasted a 56-mile-wide hole in the shallow ocean floor near what is now the mouth of the Chesapeake Bay.
The force of the impact ejected enormous amounts of debris into the atmosphere and spawned a train of gigantic tsunamis that probably reached as far as the Blue Ridge Mountains, more than 110 miles away.
The impact of the comet or meteorite would have deformed and broken up the existing arrangement of aquifers (water-bearing rocks) and confining units (layers of rock that restrict the flow of groundwater). Virginia’s “inland saltwater wedge” is a well-known phenomenon that is thought to be related to the impact crater. The outer rim of the crater appears to coincide with the boundary separating salty and fresh groundwater.
The research study appears in the November 14 issue of the journal Nature.
source: U.S. Geological Survey
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