Norris, R. D.; Firth, John (1999): Mass failure of the eastern North American margin triggered by the K/T impact. Geological Society of America (GSA), Boulder, CO, United States, In: Anonymous, Geological Society of America, 1999 annual meeting, 31 (7), 123, georefid:2000-031028
Abstract:
Ocean drilling and seismic evidence demonstrates that the Chicxulub impact triggered massive slope failure along the eastern margin of North America, Bermuda, and Spain by a combination of direct seismic shaking and tsunamis. Deep sea drilling off eastern Florida (ODP 1049) displays large scale slumping immediately below the K/T boundary ejecta bed. The boundary sequences on Bermuda Rise consist of uppermost Maastrichtian chalk sandwiched in between red claystone and were deposited by mass flows below the CCD. At Site 386 on Bermuda Rise, the chalk is cross-laminated at the base becoming plane laminated and massive near the top and overlies a layer of ejecta spherules similar to those in boundary beds from the Florida margin and New Jersey. Apparently, the chalk accumulated as turbidites originating from the North American margin and perhaps from nearby islands such as Bermuda. Most tellingly, the Maastrichtian chalk sequences on the Bermuda Rise have been previously correlated with an acoustic Horizon A* that has been mapped over nearly all of the western North Atlantic between the Bahamas and the Grand Banks. We suggest that Horizon A* marks a massive slump deposit produced by slope failure along virtually the entire eastern seaboard of North America. Slumping must have immediately predated arrival of impact ejecta on eastern Florida since upper Maastrichtian sediments are severely contorted whereas the ejecta and overlying Paleocene sediments are not. Therefore, slumping may have been triggered by the magnitude 13 earthquake associated with the impact nearly 2000 km to the southeast of the Florida margin. Slumped beds are also present just below the K/T boundary at DSDP Site 398 on the Iberian Margin. Slumps off Bermuda and Spain were probably produced by tsunamis triggered directly by the impact or by slumping along the North American margin. Evidently the Chicxulub impact had significant effects on slope stability far from regions directly affected by the blast.
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West: -10.4306 East: -10.4306 North: 40.5736 South: 40.5736
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