A COMPARATIVE ANALYSIS OF THE STRATIGRAPHIC FRAMEWORK IN RELATION TO THE GEOMORPHIC EVOLUTION OF THE CAILLOU BAY HEADLAND, SOUTH CENTRAL, LOUISIANA

Previous studies have documented spatially and temporally variable rates of surface subsidence across the Mississippi River delta plain of Louisiana. Part of this subsidence is attributed to compaction of subsurface strata that, because of textural and compositional variation, undergo different compaction rates. Consequently, variations in patterns and rates of delta plain subsidence may reflect the subsurface distribution of compaction-prone lithosomes. This research investigates whether historical changes in the surface geomorphology of the Caillou Bay headland are correlated to the distribution of buried lithosomes within the headland. The goal is to contribute toward the development of stratigraphic models that provide a predicative measure for patterns of future land loss in deltaic headlands of the Mississippi River delta plain. The project consisted of two phases: 1) the development of a lithostratigraphic framework model for the Caillou Bay headland, and 2) the documentation of the Caillou Bay headland’s geomorphic evolution as indicated by historic maps. In Phase 1 twenty-seven cores were collected and integrated with preexisting borehole data to establish the fundamental stratigraphic architecture of the Caillou Bay headland. These data were used to identify primary lithosomes, construct isopach maps of facies, and establish the spatial distribution of different sedimentary units within the headland (e.g. peat versus sand units). Phase 2 focused on developing a database of maps that collectively show patterns of shoreline change and interior wetland loss across the headland. Five maps were used for this purpose, ranging between 1863 to the present. Patterns of shoreline change and interior land loss for three time intervals were determined, indicating that patterns of land loss varied through time. Land loss maps were then overlain on lithosome contour maps to calculate the amount of land loss overlying each lithosome contour interval. Preliminary analyses of our results reveal that land loss was not uniform throughout the headland and that land loss patterns for several time periods vary as a function of the thickness of compaction-prone lithosomes.