Sediment-hosted contaminants and distribution patterns in the Mississippi and Atchafalaya River Deltas

Gulf Coast Association of Geological Societies Transactions
By: , and 

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Abstract

The Mississippi and Atchafalaya Rivers transport very large amounts of bedload and suspended sediments to the deltaic and coastal environments of the northern Gulf of Mexico. Absorbed onto these sediments are contaminants that may be detrimental to the environment. To adequately assess the impact of these contaminants it is first necessary to develop an understanding of sediment distribution patterns in these deltaic systems. The distribution patterns are defined by deltaic progradational cycles. Once these patterns are identified, the natural and industrial contaminant inventories and their depositional histories can be reconstructed. Delta progradation is a function of sediment discharge, as well as channel and receiving-basin dimensions. Fluvial energy controls the sediment distribution pattern, resulting in a coarse grained or sandy framework, infilled with finer grained material occupying the overbank, interdistributary bays, wetlands and abandoned channels. It has been shown that these fine-grained sediments can carry contaminants through absorption and intern them in the sediment column or redistribute them depending on progradation or degradation of the delta deposit.


Sediment distribution patterns in delta complexes can be determined through high-resolution geophysical surveys and groundtruthed with direct sampling. In the Atchafalaya and Mississippi deltas, remote sensing using High-Resolution Single-Channel Seismic Profiling (HRSP) and Sidescan Sonar was correlated to 20-ft vibracores to develop a near-surface geologic framework that identifies variability in recent sediment distribution patterns. The surveys identified bedload sand waves, abandoned-channel back-fill, prodelta and distributary mouth bars within the most recently active portions of the deltas. These depositional features respond to changes in deltaic processes and through their response may intern or transport absorbed contaminants. Characterizing these features provides insight into the fate of sediment-hosted contaminants.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Sediment-hosted contaminants and distribution patterns in the Mississippi and Atchafalaya River Deltas
Series title Gulf Coast Association of Geological Societies Transactions
Volume 52
Year Published 2002
Language English
Publisher Gulf Coast Association of Geological Societies
Contributing office(s) Coastal and Marine Geology Program
Description 13 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Gulf Coast Association of Geological Societies Transactions
First page 277
Last page 289
Country United States
State Louisiana
Other Geospatial Atchafalaya Delta;Mississippi Delta
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