Abstract

A "modified" deep-sea fan has formed at the terminus of the Wilmington Canyon System (4500 m) off the middle Atlantic U.S. continental margin. The fan has been modified by the presence of the lower continental rise hills. These lower rise hills acted to disperse and divert turbidity currents that flowed to the Hatteras Abyssal Plain. Such downslope movements deposited coarse grained turbiditic sediments in the troughs of the lower rise hills when the flows occasionally failed to bypass the rise. Deposition on the rise may reflect the low velocity of some turbidity currents by the time they reach the rise or the damming effect of the lower rise hills. As a result of the topographic control exerted by the lower rise hills, turbidite deposition has played an important role in the formation of the lower continental rise in the study area. Detailed petrographic analyses of sands from selected turbidite sequences indicate the sands were ultimately derived from a piedmont source. Fresh and highly angular feldspars with better rounded and more highly altered feldspars indicate that a portion of the sediment is polycyclic in nature while the remainder of the sediment is of a first cycle origin. An abundance of shallow water allochemical material in the muddy gravel turbidites points to shallow waters as the place of initiation for at least some of the turbidity currents.

First Page Preview

First page PDF preview
You do not currently have access to this article.