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No. 87: May-Jun 1993

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Giant impact-wave deposit along u.s. east coast

Along the shore from North Carolina to Maryland and also into Chesapeake Bay, deep-sea drillers have charted the Exmore Boulder Bed. No minor deposit this; it is is over 60 meters thick in places and covers more than 15,000 square kilometers. In the bed are found boulders (up to 2 meters in diameter), cobbles, pebbles, and traces of tektite glass and shocked quartz. The youngest microfossils date from the Eocene, and argon dating of the ejecta yield a date of 35.5 million years, which correlates with the North American tektite strewn field. C.W. Poag et al interpret this boulder bed as follows:

"On the basis of its unusual characteristics and its stratigraphic equivalence to a layer of impact ejecta at Deep Sea Drilling Project (DSDP) Site 612 (New Jersey continental slope), we postulate that this boulder bed was formed by a powerful bolidegenerated wave train that scoured the ancient inner shelf and coastal plain of southeastern Virginia. The most promising candidate for the bolide impact site (identified on seismic reflection profiles) is 40 km north-northwest of DSDP Site 612 on the New Jersey outer continental shelf."

(Poag, C. Wylie, et al; "Deep Sea Drilling Project Site 612 Bolide Event: New Evidence of a Late Eocene Impact-Wave Deposit and a Possible Impact Site, U.S. East Coast," Geology, 20:771, 1992.)

Comment. Our planet's land surfaces are also strewn with many debris deposits that are probably the consequence of giant impact waves. See ESM12 in Neglected Geological Anomalies, where they are termed "marine incursions". Ordering information here.

From Science Frontiers #87, MAY-JUN 1993. 1993-2000 William R. Corliss