Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Subject: search.filters.subject.Sedimentary geology

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Now showing 1 - 3 of 3
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    Integrated Geochemical Studies of the Shuram Excursion in Siberia and South China
    (2024) Pedersen, Matthew; Kaufman, Alan J; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Ediacaran Period Shuram Excursion (SE) is a globally-distributed and highly controversial phenomenon where over millions of years, sedimentary carbonates record δ13C values of -10‰ and lower. This carbon cycle anomaly may reflect disequilibrium in the world’s oceans, driven by the oxidation of a large pool of dissolved organic carbon (DOC), with the oxidants sourced from the intense weathering of the continents, forcing major changes to ocean chemistry through the ventilation of the deep ocean, evidenced by a positive shift in carbonate uranium isotope values, and invoking the onset of early animal biomineralization. This study utilizes high-resolution carbonate Li isotopes from two SE-successions, U isotopes, REE abundances and Ce anomalies which reveal the dynamic interplay between intensified continental weathering associated with tectonic reconfiguration and the subsequent environmental and ecological response that may have been amplified by the ecosystem-engineering abilities of a newly discovered sponge-grade animal.
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    Spatial and Temporal Variability in Suspended Sediment Characteristics in the Surface Layer of the Upper Chesapeake Bay
    (2020) Barletta, Stephanie Marie; Sanford, Lawrence P; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Periodic high discharge events flush suspended sediments from the Susquehanna River and Conowingo Dam reservoir into the upper Chesapeake Bay, which extends from the mouth of the Susquehanna River to the Bay Bridge near Annapolis, MD. Sediment characteristics in the surface layer of the upper Bay and changes in these characteristics with varying river discharge and distance downstream are not well known. In order to develop an integrated understanding of surface layer sediment dynamics, several in-situ data sets were examined at the Bay head and downstream along the Bay’s center channel, providing data on the spatial and temporal variability of suspended particle characteristics including concentration, settling speed, bulk density, and size. It was found that particles are entirely disaggregated at the Dam, later aggregating to a limited extent down Bay, and that downstream characteristics are more weakly linked to Susquehanna flow at lower flows and longer distances.
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    Near Threshold Sediment Transport by a Forced Jet Impinging on a Mobile Sediment Bed
    (2015) Corfman, Kyle; Kige, Kenneth; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Although sediment transport has been extensively studied in the past, flows such as rotorcraft brownout with large-scale coherent structures call many of the simplifying assumptions into question. The objective of this study is to develop a model for the prediction of sediment removal, referred to as erosion, based on independent measurements of the single-phase flow and the evolution of bedforms on the surface of a mobile sediment bed. A series of phase-resolved particle image velocimetry (PIV) flow measurements have been conducted to quantify the stress induced by an acoustically forced impinging jet, analagous to tip-vortices within the rotor wake. The threshold conditions for incipient particle motion are quantified through a series of PIV measurements of the single-phase flow at conditions found to produce quantifiable erosion of the surface. A force balance approach is used to develop a model, following the theory presented by Bagnold (1966), to predict the transport of sediment due to the stress above the theshold. A series of surface elevation measurements are analyzed to quantify the removal of sediment, for the evaluation of the predicted model. An additional series of PIV measurements are performed on a prototype bedform, modeled after the observed bedforms, to quantify the changes in the flow field caused by their developement. The proposed model is shown to provide a better prediction of the observed erosion than classical sediment transport models, especially for cases close to the threshold conditions. For higher speed cases however, the model dramatically over predicts the observed erosion. Several physcially-based explanations are provided for this kink in the trend.