The Significance and Limitations of Statistical Parameters for Distinguishing Ancient and Modern Sedimentary Environments of the Lower Georgia Coastal Plain

Abstract

ABSTRACT The lower Coastal Plain of Georgia is considered to be a significant area for the study of preserved coastline sediments because ancient deposits are generally well preserved and provide a comprehensive record of the geomorphological and sedimentological history of the region. Samples have been collected from six Pleistocene barrier coastlines and the Holocene coast in an attempt to evaluate the significance and limitations of statistical parameters for distinguishing ancient and modern sedimentary environments. The sediments of each barrier coastline can be subdivided into lagoon-salt marsh and barrier-island facies. The former include estuarine and tidal channel sediments whereas the barrier facies also include dune, littoral, shallow neritic and offshore channel deposits. Barrier island sands are better sorted than those from lagoon-salt marsh environments although all samples have mean grain size values higher than 1.50. The coarsest sediments in the barrier island environments are found in the tidal inlets and channels, and about 70 percent of the samples are negatively skewed. Diagenesis possibly accounts for a small percentage of positively skewed Pleistocene barrier island sands. About 30 percent of the lagoon-salt marsh sands are positively skewed. More than 90 percent of the Holocene beach sands are negatively skewed, but about 70 percent of the dune sands show positive skewness. The sign of skewness in this study is related to energy variations in different sedimentary environments, despite the fact that investigations of paleoenvironments in general can present interpretative problems.