Raiding the Toolbox - Techniques for Assessing Historical, High-Resolution Records of Coastal and Estuarine Sediment Erosion, Transport and Sedimentation

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  • March 19, 2019
Creator
  • Elliott, Emily
    • Affiliation: College of Arts and Sciences, Department of Marine Sciences
Abstract
  • Estuaries act as a buffers to material transport from terrestrial to oceanic environments. Characterizing mechanisms of erosion, transport and deposition within estuaries is crucial for understanding material flux to the marine environment and compositional transformations. However, obtaining multi-decadal high-resolution records of sediment flux, source, and composition within estuaries is a major challenge in coastal research due to dynamic processes that actively erode, resuspend and/or rework the sedimentary record. For this reason, estuarine sedimentology has dominantly focused on either long-term (decadal to millennial) records that show constant sedimentation rates often matching the rate of sea-level rise, or short-term (multi-year to decadal) studies that show variable sedimentation rates associated with events. This dissertation presents a monthly record of estuarine sedimentation that spans ~40 years within a highly accreting mini-basin, Cape Lookout Bight (CLB), NC, utilizing existing and newly-developed methods. This long-term high-resolution record is used to identify the dominant physical drivers of sediment flux within the estuary. Chapter 1 of this dissertation uses the lithologic and the long-term geochronology of this basin to determine its formation and sediment sources through time. Chapter 2 presents and tests the efficacy of a modified uni-directional time-integrated mass suspended-sediment sampler for use within the bi-directional flow of a tidal (estuarine) environment. Modified collectors are then used to verify the dominant estuarine sediment source to the CLB basin. Chapter 3 applies and tests different geochronological models for excess Pb-210 within the estuarine system, showing the strengths and weaknesses of each model application within our system, and presents a method for applying tempestite horizons for increased resolution and accuracy of estuarine geochronologies. Finally, Chapter 4 uses this established high-resolution multi-decadal geochronology, along with historical physical data obtained for the system, to identify sediment source and drivers of sediment transport within the estuary to the coastal ocean through time. This study identifies multiple sedimentation events that are triggered by conditions that have a recurrence interval of ~1 year (+/- 0.5) and advances our understanding of how storms, and therefore climate change may impact sediment erosion, transport and deposition within the coastal zone.
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  • In Copyright
Advisor
  • McKee, Brent
  • Lambert, W.
  • Rodriguez, Antonio
  • Cable, Jaye
  • Seim, Harvey
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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Date uploaded
  • July 6, 2017

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