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Book Chapter

Seafloor Characteristics and Dynamics Affecting Geotechnical Properties at Shelfbreaks

By
Richard H. Bennett
Richard H. Bennett
Naval Ocean Research and Development Activity (NORDA)
Seafloor Division Code 360, NSTL Station, Mississippi 39529
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Terry A. Nelsen
Terry A. Nelsen
National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological Laboratories
4301 Rickenbacker Causeway, Miami, Florida 33149
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Published:
January 01, 1983

ABSTRACT

Variable geotechnical and sedimentological properties of sediments on both active and passive continental margins is the rule rather than the exception. Significant variability is observed in the physical, mechanical, and textural properties of sediments from the individual core to the regional level. Sediment properties and soil “state” are determined by the primary depositional properties and post-depositional processes active on and within shelfbreak deposits. Post-depositional processes play an important role in determining the ultimate nature and time-dependent changes in the mass physical and mechanical properties of submarine deposits. Fundamental geotechnical properties such as shear strength and compressibility from several shelfbreak areas are compared and related to eight shelfbreak sediment textural models. Sediment behavior such as resistance to erosion, slumping, consolidation, and liquefaction depend upon: (1) the basic sediment types present at shelfbreaks (textural model), (2) the fundamental geotechnical properties of the particular deposit, and (3) temporally and spacially variable physical and biological processes active in the shelfbreak zone.

Shelfbreak characteristics important to offshore engineering activities and future scientific studies on continental margins include: varied morphology with steep local slopes; rapid changes in physical oceanographic processes; variable erosion and sedimentation rates; variable offshelf sediment transport; onset of significant pelagic sedimentation; rapid textural changes; rapidly changing benthic community; high variability in geotechnical properties; and the onset of creep and mass wasting processes. Shelfbreak sediment types may be predominantly terrigenous, carbonate, or glacio-marine in origin. Although some of these characteristics can be found in other submarine environments, they can be identified as important elements of many passive and active continental margins.

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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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