--> --> Characterization of Surficial Sediments from a Modern Delta Wetland

2019 AAPG Eastern Section Meeting:
Energy from the Heartland

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Characterization of Surficial Sediments from a Modern Delta Wetland


Delta wetlands are important for petroleum exploration and production because many of the world’s petroleum system are ancient deltas, and for understanding modern coastal erosion and deposition processes. Our goal was to analyze the composition of freshly deposited sediments in a modern delta wetland (Wax Lake Delta, Louisiana) and develop statistical relationships between organic matter content, grain size, water depth and vegetation type and abundance. These measurements were made as part of a broader study that also assessed nutrient cycling in the delta top wetland. We collected sediment cores to an approximate depth of 20-30 cm at five locations that spanned levee and lagoon environments. Multiple grain size and organic matter characteristics were measured on the sediment samples, including loss on ignition, as a proxy for organic content, and mud fraction using hydrometer analysis. We hypothesize that organic matter content and mud fraction vary in shallow to deep water and in emergent or submerged vegetation. Preliminary observations show a range of mud:sand fractions from roughly 90:10 to roughly 40:60 that are clustered based on location. Measurements made on the levee have mud:sand ratios from approximately 25:75-35:65. These results will improve understanding of the relationships between grain size and delta morphology (which relates water depth, vegetation, and nutrient cycling) within modern and ancient deltas.