Louisiana Cheniers: Clues to Mississippi Delta Historyby William F. Tanner, Florida State Univ, Tallahassee, United States,
Abstract: The cheniers of southern Louisiana have map differences, deeding differences, and granulometric differences that distinguish them from swash-built beach ridges and from dune ridges. Instead, they are like late-storm settling deposits in near-shore water beyond the surf zone. Granulometric methods (suite statistics) distinguish between these cheniers and swash-built ridges. On a plot of mean kurtosis vs standard deviation of kurtosis, these cheniers are far from all known beach ridges or beaches. Mean K is close to 10 (very high ) in a region where 4 was expected. The standard deviation of the kurtosis is also about 10, where 2 or less was expected. No other beach ridge set is known with this parameter as high as six. The cheniers under study were built by settling over periods of a few centuries when sea level stood 1-2 m higher than now, but not by a single storm. Each wide swale between cheniers represents a similar interval when sea level stood 1-3 m lower than now. Each chenier may be equal to a beach ridge set in other settings, and thus may reflect some of the parts of late Holocene sea level history. The type of sediment indicates proximity to a major river delta.
Subject Headings: History | Beaches | Sea level | Statistics | Nearshore | Dunes | Mapping | Light rail transit | North America | Louisiana | United States | Mississippi
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