LANDRUM, KENNETH E., Department of Geology, Tulane University, New Orleans, LA

ABSTRACT: The Environmental Sedimentology of the Barataria Basin

Bottom sediments of the Barataria Basin estuarine complex consist predominantly of clayey silts and silty clays derived from the erosion of the Lafourche and St. Bernard lobes of the Mississippi River delta and sediments associated with historic crevasses along the modern Mississippi River. The clay mineralogy of the sediments is dominated by montmorillonite and kaolinite with lesser amounts of illite also present. The bottom sediments of the complex directly reflect the influence of the Mississippi River basin.

The concentrations of fourteen trace-metals was determined for 150 bottom sediment samples by plasma emission analyses. The aerial distribution of trace-metals is controlled predominantly by the texture and mineralogy of the basin sediments. The centers of the lakes in the Barataria basin reflect an enrichment in trace-metals due to their high clay contents. The high clay and carbon contents of the sediments provide excellent sites for the adsorption and complexation of trace-metals from the water column as sedimentation within the basin acts as a sink for trace-metal accumulation.

An interpretive model using Florida estuarine sediments was used to account for natural trace-metal variability and anthropogenic enhancement. Various trace-metal concentrations were normalized against aluminum, iron, and clay concentrations and correlations were determined. Of the fourteen trace-metals analyzed barium, cadmium, and lead are the least correlatable and represent those trace-metals with the greatest anthropogenic influence. Areas influenced by produced waters display little variation in trace-metal concentrations relative to the entire basin. Although evidence of anthropogenic input exists within parts of the basin, comparisons of the average trace-metals data with other Gulf Coast estuaries indicates that the Barataria Basin has not been heavily impacted.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.