Date of Award

Spring 1981

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

George F. Oertel

Committee Member

John C. Ludwick

Committee Member

Ronald E. Johnson

Committee Member

Dennis A. Darby

Call Number for Print

Special Collections LD4331.O35 B69

Abstract

Sediment samples taken from a washover deposit were used to determine the mode of sediment transport within overwash surges. The determination of sediment transport mode is based on the concept of hydraulic equivalency of different density grains. Hydraulic equivalency may be based on settling velocities or entrainment velocities. Two individual mineral grains of different densities cannot have the same settling and entrainment velocities. If the settling velocities of each grain are similar, then the less dense grain must be physically larger to settle at the same rate as the smaller denser mineral. However, once both of these grains have made bed contact, the larger surface area of the lighter mineral protrudes further into the water column and is more susceptible to transport than the smaller, denser grain. Similar settling velocities of different density minerals indicate deposition out of suspension. Different settling velocities indicate transport involving some form of bed contact.

This study, conducted on the Outer Banks of North Carolina, involved the settling velocities of magnetite, garnet and quartz minerals separated from the same sample to determine principal mode of transport. Results indicated that 16 percent of the samples analyzed were the result of transport by suspension, while the remaining 84 percent of the samples were transported with bed contact of varying intensity.

Magnetite consistently showed the slowest settling rates, followed by garnet and quartz minerals, The study further indicated that magnetite was the most difficult to entrain due to its high density, spherical shape and the larger relative size of the bed material.

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DOI

10.25777/7zwv-b514

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