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Book Chapter

Breaching the Shelfbreak: Passage from Youthful to Mature Phase in Submarine Canyon Evolution

By
John A. Farre
John A. Farre
Lamont-Doherty Geological Observatory, Columbia University
Palisades, New York 10964;
1
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Bonnie A. McGregor
Bonnie A. McGregor
U.S. Geological Survey, Fisher Island Station, Miami
Florida 33139;
2
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William B. F. Ryan
William B. F. Ryan
Lamont-Doherty Geological Observatory, Columbia University
Palisades, New York 10964;
1
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James M. Robb
James M. Robb
U.S. Geological Survey, Woods Hole
Massachusetts 02543
3
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Published:
January 01, 1983

ABSTRACT

Mid-range side-scan sonar images of the U.S. Middle Atlantic continental margin show the presence of a variety of erosional features. Amphitheatre-shaped scars are present on the continental slope near Carteret Canyon. Several slope canyons, whose heads do not appreciably breach the shelfbreak, have a pinnate drainage pattern on the upper, sediment-draped slope. The thalwegs of these canyons follow nearly straight paths down the slope. In contrast, Wilmington, a shelf-indenting canyon, follows a curved to meandering path down the slope.

On the basis of these and other data, we propose a preliminary explanation of evolution of canyons on the middle Atlantic slope. In this model, localized slope failure begins the process of canyon formation. By headward erosion, these depressions extend upslope and form linear sediment chutes. These slope canyons represent the youthful phase in canyon evolution. Slope canyons begin the transition to a mature phase when the canyon heads breach the shelfbreak. Access to the continental shelf leads to the transport of shelf-derived materials through the canyon.

During the youthful phase, the dominant mechanism of canyon erosion is the failure of the slope itself. In the mature phase, entrenchment is augmented by the episodic cutting by turbulent sediment suspensions enroute from the shelf to the continental rise and abyssal plain. The shelfbreak, in this model, is an important factor in the evolution of a passive continental margin.

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SEPM Special Publication

The Shelfbreak: Critical Interface on Continental Margins

Daniel Jean Stanley
Daniel Jean Stanley
Division of Sedimentology Smithsonian Institution
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George T. Moore
George T. Moore
Chevron Oil Field Research Company La Habra California
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SEPM Society for Sedimentary Geology
Volume
33
ISBN electronic:
9781565761636
Publication date:
January 01, 1983

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