Nature and origin of the lower continental rise hills off the east coast of the United States

Abstract

Precision depth recordings, seismic reflection records, deep sea drill holes, and piston cores are used to develop a chronological interpretation for the origin of the lower continental rise hills off a portion of eastern United States. A detailed bathymetric map is presented which depicts the geometry and orientation of the "hills" as well as a system of distributory channels, some of which are active and others extinct. An elongated ridge (Hatteras Outer Ridge), which was formed parallel to the continental margin by the Western Boundary Undercurrent (WBUC) is defined by an acoustically transparent zone on seismic reflection records. This ridge, which was eroded by turbidity currents during the Pleistocene, is composed of hemipelagic clays of Miocene-Pliocene age. The turbidity currents created a distributory channel system which gave rise to the "hill-like" features. Subsequent to the erosion of the Hatteras Outer Ridge, turbidity currents filled many channels and injected fine-grained sands, silts, and hemipelagic clays into the contour current (WBUC). The northeast to southwest moving contour current deposited these sediments onto the upcurrent (northeast) sides of the "hills" and gave rise to their apparent upcurrent migration. © 1979.