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St. Petersburg Coastal and Marine Science Center > Barrier Island Evolution > Research > Geologic Analysis

Barrier Island Evolution

Research - Geologic Analysis

Sediment cores collected during the early part of 2012 show gradual increase in organic matter and porosity, decrease in bulk density upcore, which reflect longer term fair-weather deposition.
Sediment cores collected during the early part of 2012 show gradual increase in organic matter (OM) and porosity, decrease in bulk density upcore, which reflect longer term fair-weather deposition. Following Hurricane Isaac, sediment cores have sharp contacts of low OM and porosity and high bulk density reflecting the denser and presumably sandier, sediment transported across the island by overwash and/or breaching processes. [larger version]

Geomorphic series of the Chandeleur Islands, Louisiana, depicting nearshore digital elevation models (50 m x 50 m) of merged single-beam and interferometric sonar soundings for the years 2011, 2012, 2013, and 2015 (small, focused survey with interferometric only).
Geomorphic series of the Chandeleur Islands, Louisiana, depicting nearshore digital elevation models (50 m x 50 m) of merged single-beam and interferometric sonar soundings for the years 2011, 2012, 2013, and 2015 (small, focused survey with interferometric only). [larger version]

Geologic variability (changes in stratigraphy, modern sediment distribution and composition, and morphology) has long been associated with barrier island evolution over centennial and millennial time scales. However, the relative importance of geologic variability over shorter time scales (days to years) remains poorly understood.

Regional-scale research, while helpful for establishing the geologic framework in which barrier islands evolve, lacks the finer-scale resolution necessary for addressing seasonal and interannual system response. Furthermore, models of morphologic evolution are often ill equipped to incorporate the complexity of natural geologic variability and often assume uniformity in sediment distribution, composition, and availability that may not exist. This leads to results that may not be consistent with observations.

In order to address medium-term relationships between geologic variability and storm and non-storm processes, high-resolution information from highly dynamic areas of the nearshore, surf zone, and back-barrier must be obtained, and observed geologic variability must be suitably parameterized for integration with predictive models. Quantifying changes in morphology and sediment distribution over short time scales will demonstrate how geologic variability influences medium-term barrier island response and near-term barrier island trajectories and help to refine sedimentological boundary conditions for morphologic evolution models.

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