气候变化领域集成服务门户

Recent studies of estuarine sediment deposits have focused on grain size spectra as a tool to better understand depositional processes, in particular those associated with tidal inlet and basin dynamics. The key to accurate interpretation of lithostratigraphic sequences is establishing clear connections between morphodynamic changes and the resulting shifts in sediment texture. Here, we report on coupled analysis of shallow sediment profiles from a closed estuarine lagoon in concert with recent changes in lagoon morphology reconstructed from historic sources, with a specific emphasis on the ability of suite statistics to provide meaningful insights into changes in sediment transport agency. We found that a major reorganization in lagoon morphology, dating to the 1940s, was associated with a shift in sediment deposition patterns. The restricted inlet was associated with deposition of sediments that were finer, less negatively skewed, and less leptokurtic in distribution than sediments deposited while the lagoon had a more open structure. These shifts are associated with a change in transport process from fluvial (through-flow) to closed basin (trapping). We also found other chemostratigraphic changes accompanying this shift in sediment texture, reflecting changes in organic matter source, wetland species composition, and an increase in sediment organic content, as presumably coarse, well-ventilated floodplain sediments tend to result in mineralization rather than sequestration of organic matter. In conclusion, we found that grain size analysis, in concert with the suite statistics technique, reflected changes in coastal configuration supported by historic maps and photos, however, we also recognize that this analysis was more informative given further context through additional sedimentary analyses. These findings provide a basis for the interpretation of particle size distribution in lithostratigraphic sequences associated with bar-built estuaries, where understanding natural and anthropogenically-modified inlet dynamics may help shape conservation management where concerns exist with respect to fish passage, water quality, and sediment transport. Published by Elsevier Ltd.