An Article In Meteorite-Times Magazine
by Paul Harris
37.3 Gram Specimen, 6cm x 4.5cm x 1 cm from The Darryl Futrell Collection Of Tektites
Now owned by The Meteorite Exchange, Inc. (Click the image for a larger view)
The North American Strewn Field contains the Georgia tektites, Texas Bediasites, a single specimen from Martha's Vineyard (an island off Massachusetts), and a single specimen found in Cuba. Tektite fragments have been found off-shore New Jersey, and microtektites are found from the oceans off New Jersey, The Gulf of Mexico, and the Caribbean. The age of this strewn field is approximately 35.5 million years old.
Georgiaites are olive-green in transmitted light. Georgia tektites are rare with only about 1300 known specimens. The first Georgiaite recognized as a tektite was found near Empire Georgia in 1938 although specimens had previously been found in 1911 and 1928. Georgiaites have been found as splash forms and as a single Muong Nong type specimen. The world's foremost authority on Georgiaites is Hal Povenmire who we hope will one day grace Meteorite-Times with an article. Hal Povenmire has been mapping the strewn field since 1970 and to date, the size of the strewn field has increased from 500 square miles to over 7000 square miles, and the number of Georgia specimens has increased from about 200 to about 1300. The largest splash form weighs 70.5 grams and was authenticated by Hal Povenmire. The largest Georgiaite is of the Muong Nong type and weighs 130 grams. There have been no ablated specimens found.
For many years the Lunar versus Terrestrial Impact theories battled back and forth. If tektites formed by terrestrial impacts, where is the crater?
Finding The Source Crater - DSDP 612 - A breakthrough for the impact theory.
In 1987 a deep sea drilling core, DSDP 612 drilled off the New jersey coast was the first drill core to yield tektite fragments, microtektites, shocked minerals coesite and stishovite. Finding tektite fragments with microtektites and other impact indicators together was a breakthrough for tektite research and the terrestrial impact theory.
In 1992 seismic reflection profiles indicated a possible impact crater named Tom's Canyon Crater but although it's ejecta blanket contains tektite fragments, it's 24 x 13.5 km size is too small to be the source crater.
In 1994 Dr. Pong published his finding of the Chesapeake Bay Crater beneath Cape Charles. Seismic reflection anomalies show a crater hidden below a few hundred meters of sediments. The impact crater is 90 km in diameter, almost 2 km deep, and resembles the Nordlinger Ries crater with a central ring. The impact generated a series of enormous tsunamis.
Please click on the USGS links below for full size images
that are readable.
Courtesy of USGS http://pubs.usgs.gov/prof/p1612/fig1.html
Courtesy of USGS http://pubs.usgs.gov/prof/p1612/fig2.html
Courtesy of USGS http://pubs.usgs.gov/prof/p1612/fig2.html (scroll down page)
For more USGS information please see http://pubs.usgs.gov/prof/p1612/powars.html#CHES