Degree
Doctor of Philosophy (PhD)
Department
Oceanography and Coastal Sciences
Document Type
Dissertation
Abstract
This dissertation investigates geomorphology, sediment transport, and morphodynamic evolution within abandoned and active depositional environments of the Mississippi River Delta system in the northern Gulf of America using integrated geophysical, sedimentological, and geospatial approaches. Across coastal bays, offshore shoals, dredged borrow areas, and active delta-front environments, both relict and modern Mississippi River distributary systems exert primary control on sediment distribution, substrate composition, and seafloor morphology.
High-resolution CHIRP seismic data and sediment-core analyses revealed that the shallow subsurface of Upper Barataria Bay preserves distributary-associated deposits, interdistributary basin muds, and shallow biogenic gas accumulations linked to former Mississippi River delta occupation. Buried paleochannel systems remain preserved beneath the modern bay and continue to influence sediment texture, hydrologic connectivity, and shallow subsurface structure. Round Lake preserves remnants of an abandoned distributary corridor, whereas Bay Batiste exhibits more heterogeneous distributary-mouth and crevasse-associated architecture. Shallow gas occurrence was concentrated within fine-grained organic-rich muddy deposits and produced widespread acoustic disruption throughout portions of the basin.
Time-series sediment analyses across eastern Ship Shoal demonstrated that the shoal crest remained comparatively coarse and stable through time, whereas dredged borrow pits rapidly accumulated finer-grained, organic-rich sediments following excavation. The older Caminada pit exhibited the highest organic matter and finest sediments, while the younger Terrebonne pit displayed transitional early-stage infilling conditions. These results indicate that offshore restoration sediment resources are directly tied to relict distributary and channel-associated deposits emplaced during earlier phases of Mississippi River lobe development.
Terrain analyses derived from multibeam bathymetry showed that antecedent depositional setting strongly governs post-disturbance geomorphic adjustment across the Louisiana shelf. Mud-capped dredge pits exhibited the broadest slope distributions and greatest persistence of irregular terrain, whereas sandy pits displayed lower slopes and more efficient morphologic relaxation. Seafloor Complexity Index mapping identified zones of persistent geomorphic adjustment and elevated relative geohazard potential.
Collectively, these results demonstrate that inherited Mississippi River depositional systems continue to shape offshore sand resources, sediment transport pathways, substrate stability, and seafloor morphodynamics across coastal Louisiana, emphasizing the importance of antecedent geomorphology and depositional history in future Louisiana coastal restoration projects.
Date
5-26-2026
Recommended Citation
Gartelman, Adam M., "Geomorphology and Sediment Transport in Abandoned Lobes of the Mississippi River Delta in the Northern Gulf of America" (2026). LSU Doctoral Dissertations. 7093.
https://repository.lsu.edu/gradschool_dissertations/7093
Committee Chair
Xu, Kehui
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1
Included in
Geology Commons, Geomorphology Commons, Geophysics and Seismology Commons, Oceanography Commons, Sedimentology Commons