Document Type

Thesis

Abstract

Muddy fine-grained sediments often dominate estuarine seabeds, and the dynamics of these cohesive sediments influences the management of coastal waters, ecological health and navigational safety. Through the use of a newly designed square sediment push core and laboratory acoustic technology, this project aimed to discover what acoustic wavelengths best portray fine-scale sediment laminations in the first 0-10 centimeters of the sediment bed (ephemeral layer) and define the sediment characteristics (grain size, bulk density, fecal pellet content, and organic content). The Clay Bank (37.62°N, 76.62°W) and Ferry Point (37.37°N, 76.64°W) study sites in the middle region of the York River estuary, VA were investigated through the collection of four sediment cores in August and September 2012. Two distinct sediment compositions were found at each site, with the Ferry Point study site containing 20% or more sand in addition to silt, clay, and shell bits. Clay Bank sediments contained primarily silt and clay constituents (i.e. mud) and less than 10% sand. Fecal pellet content, a proxy for benthic biota activity and biostablization, portrayed higher concentrations at Clay Bank, as expected when compared to the turbid shoal environment of Ferry Point. X-radiography images were used to determine small-scale changes in sediment bulk density and compared to laboratory grain size analysis bulk density measurements. Ultimately, acoustic sensing technology did not decipher the best frequency (MHz) to identify small-scale sediment laminations due to high attenuation at a shallow depth in the sediment (around 5 centimeters). Further investigation with acoustic frequencies, spatially registered xradiography and laboratory grain size analysis is needed to obtain a sufficient amount of comparison data and the most effective acoustics.

Date Awarded

2013

Department

Geology

Advisor 1

Christopher M. Bailey

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