About This Item
Share This Item
Shallow seismic reflection surveying of the continental rise between Accomac and Baltimore Canyons shows stratified layers overlying an unstratified interval believed to be mass-flow deposits. Planktonic and benthonic foraminifera from 43 piston cores and grab samples, collected between 150 and 2,360 m (492 and 7,743 ft) depth, have been used to interpret the source and age of unstratified sediments along canyon axes.
Five mappable seabed faunal distributions characterize the outer shelf, slope, and upper rise. Multiple regression was used to relate Rose bengal stained assemblages as well as total sediment assemblages to water depth, median grain size, bottom temperature, and oxygen content in order to index the subsurface samples to these modern physical parameters.
Major lithologic and micropaleontologic contrasts characterize the sediment columns from the canyon axes: soupy, olive clays with foram assemblages similar to living populations overlie firm, gray to rusty-brown clays with Pleistocene planktonic foraminifera and benthics today found in upper slope areas. This, combined with the presence of sand layers bearing shelf forams, suggests that the mass-flow deposits are related to slope failures in response to glacially lowered sea levels.
End_of_Article - Last_Page 557------------