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The Role of Basin Configuration and Allogenic Controls on the Stratigraphic Evolution of River Mouth Bars

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The Role of Basin Configuration and Allogenic Controls on the Stratigraphic Evolution of River Mouth Bars University of New Orleans ScholarWorks@UNO University of New Orleans Theses and Dissertations Dissertations and Theses Spring 5-18-2018 The Role of Basin Configuration and Allogenic Controls on the Stratigraphic Evolution of River Mouth Bars Joshua Flathers University of New Orleans, [email protected] Follow this and additional works at: https://scholarworks.uno.edu/td Part of the Sedimentology Commons Recommended Citation Flathers, Joshua, "The Role of Basin Configuration and Allogenic Controls on the Stratigraphic Evolution of River Mouth Bars" (2018). University of New Orleans Theses and Dissertations. 2462. https://scholarworks.uno.edu/td/2462 This Thesis is protected by copyright and/or related rights. It has been brought to you by ScholarWorks@UNO with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights- holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Thesis has been accepted for inclusion in University of New Orleans Theses and Dissertations by an authorized administrator of ScholarWorks@UNO. For more information, please contact [email protected]. The Role of Basin Configuration and Allogenic Controls on the Stratigraphic Evolution of River Mouth Bars A Thesis Submitted to the Graduate Faculty of the University of New Orleans in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences by Joshua Flathers B.S. University of New Orleans, 2014 May, 2018 Copyright 2018, Joshua Flathers ii Contents List of Figures iv List of Tables v Abstract vi Introduction ................................................................................................................................................. 1 Methodology and Experimental Design .................................................................................................... 5 Allogenic Controls .................................................................................................................................... 8 Fluvial Discharge .................................................................................................................................. 8 Tides ..................................................................................................................................................... 9 Schematized Basin Configurations ......................................................................................................... 11 Initial Basin Morphology .................................................................................................................... 11 Initial Basin Depth and Slope ............................................................................................................. 11 Lateral Basin Confinement ................................................................................................................. 11 Results ........................................................................................................................................................ 13 Allogenic Controls .................................................................................................................................. 14 Basin configuration ................................................................................................................................. 16 Incipient Basin Morphology ............................................................................................................... 16 Basin Depth and Slope ........................................................................................................................ 18 Lateral Basin Confinement ................................................................................................................. 22 Discussion .................................................................................................................................................. 24 Mud Content ........................................................................................................................................... 24 Allogenic Controls .............................................................................................................................. 24 Incipient Basin Morphology ............................................................................................................... 25 Basin Depth and Slope ........................................................................................................................ 27 Lateral confinement ............................................................................................................................ 28 Morphology and Stratigraphy ................................................................................................................. 28 Allogenic Controls .............................................................................................................................. 29 Incipient Basin Morphology ............................................................................................................... 30 Basin Depth and Slope ........................................................................................................................ 30 Lateral confinement ............................................................................................................................ 31 Conclusion ................................................................................................................................................. 33 References .................................................................................................................................................. 36 Vita ............................................................................................................................................................. 38 iii List of Figures Figure 1— Schematized domain in map view. ............................................................................................. 8 Figure 2— Discharge time series .................................................................................................................. 9 Figure 3— Sinusoidal and astronomic tidal signals imposed ..................................................................... 10 Figure 4— Plan-view example of a confined basin used ............................................................................ 12 Figure 5— The response in mud content to changes in initial conditions and allogenic controls .............. 13 Figure 6— A comparison of mouth bars reulting from characteristic and variable discharge ................... 14 Figure 7— A comparison of mouth bars resulting from sinusoidal and astronomic tidal signals .............. 16 Figure 8— A comparison of mouth bars resulting from the presence of initial basin morphology ........... 17 Figure 9— The response in mud content to varying fluvial discharge, tidal range, and the presence of an incipient mouth bar ................................................................................................................... 18 Figure 10— Bathymetric profiles of mouth bars resulting from varying initial basin depth ...................... 19 Figure 11— A comparison of mouth bars resulting from varying initial basin depth ................................ 20 Figure 12— Bathymetric profiles of mouth bars resulting from varying initial basin slope ...................... 20 Figure 13— A comparison of mouth bars resulting from varying initial basin slopes ............................... 21 Figure 14— The response in mud content to varying initial basin depth and slope. .................................. 21 Figure 15— Bathymetric profiles of mouth bars resulting from varying initial basin width. .................... 22 Figure 16— The response in mud content to varying initial basin width. .................................................. 23 iv List of Tables Table 1— Tidal constituents used for simulations with astronomic tides. ................................................. 10 v ABSTRACT Deltas are important coastal systems throughout the world. River mouth bars are key landforms in the development of deltas, are characterized by sediment deposition, and have high potential for sediment preservation. Scientists and professionals seek to understand the discrete response of mouth bars to the various controls governing their evolution. This study utilizes the numerical modelling software Delft3D to provide additional evidence supporting the morphological and stratigraphic responses resulting from variations in basin configurations and allogenic controls (fluvial discharge, tides, basin width). Mud content within the bar increased analogous to an increase in the tidal modulation, while a decrease in the initial basin depth reduced mud content. Initial basin slope and lateral confinement had less obvious impacts on stratigraphy. Finally, variable fluvial discharge and the incorporation of realistic tidal harmonics produced similar bar morphologies (compared to simulations with constant flow and sinusoidal tides), yet demonstrated significant differences in bar stratigraphy. Keywords: river mouth bar, allogenic controls, deltas, basin configuration, Delft3D, sediment transport,
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