Optically stimulated luminescence (OSL) dating beach ridge sediments is one method for resolving barrier island growth at intermediate scales (decades-centuries), information that is lacking for Louisiana. This research combines OSL, GPR, aerial imagery, and cores to document temporal and spatial evolution of a Louisiana barrier island. Grand Isle is composed of beach ridges organized in distinct, unconformable sets that began forming 0.75 ka until 0.575 ka when deposition ceased, the ridges were partially eroded, and deposition resumed in a more eastward direction. The central ridges formed between 370±30 and 170±10 years ago at a rate of one ridge every 11.6 years with sand from the eroding Caminada headland that, with flanking barriers, forms the Bayou Lafourche transgressive depositional system. Grand Isle’s lithosome (92,600,000 cubic meters) requires an annual longshore transport of 128,625 cubic meters. The lithosome thickness (10 meters) and steady sediment supply stabilize the island relative to other Louisiana barriers.

<p>St. Joseph peninsula is situated on the panhandle of Florida west coast in the northeastern Gulf of Mexico at N29°50‘ and W85°20‘ and is located at the west edge of the westernmost portion of the Apalachicola Barrier Island Complex (ABIC) on the Gulf of Mexico shoreline. Three vibra-cores were collected on Saint Joseph Bay side of Cape San Blas which is part of St. Joseph peninsula to determine its evolution in context of previous work by Rink and Lopez (2010). The study uses detailed textural analysis (PSD - Particle Size Distribution plots), multivariate statistics on the PSDs (Q-mode cluster analysis) and organic matter geochemistry (C/N and δ13C). In addition, Ground Penetrating Radar (GPR) profiles are used to provide broader stratigraphic context.</p> <p>The stratigraphic analysis found that CSB has an older nucleus of strandplain deposits dating to >12 Ka that were subsequently flooded and modified through Holocene sea-level rise at ≈ 2.2 Ka. Actual barrier formation began sometime between 2.2. Ka and 0.6 Ka which is the oldest beach ridge measured by Rink and Lopez (2010). Progradation of the barrier on the St Joseph Bay side began at least by 0.3 Ka and likely earlier. There is no evidence to indicate a higher than present sea-level in our core data and our data follows that of other sea-level studies using submerged offshore samples</p> / Master of Science (MSc)