Bottom sediments of the Upper Barataria Basin and the Mississippi River-Gulf Outlet estuarine complexes consist predominantly of silty clays and clayey silts derived from the erosion of the St. Bernard lobe of the Mississippi River delta. Montmorillonite dominates the sediment clay mineralogy and reflects the influence of the Mississippi River Basin The acid-leachable concentrations of fourteen trace metals were determined for 284 bottom sediment and 44 core interval samples by plasma emission. The areal metal distribution is controlled predominantly by the bottom sediment texture and mineralogy and is significantly correlated with smaller grain-size sediments, carbon content, and aluminum and iron content. Ba, Cd, Pb, and Zn are the least correlatable and may reflect the greatest anthropogenic influence. Sediments have greater mean metal content than Florida and Texas estuarine sediments, generally due to their finer grain size, lack of CaCO3, and higher clay, iron, and carbon content Concentrations of As, Ba, Cd, Pb, V and Zn, elevated relative to basinwide means, were detected from sediments associated with oil and gas drilling and production, sandblasting, dredging, and stormwater and industrial discharges. Average metal contents were comparable to other Gulf Coast estuaries and below the lowest effect level sediment quality guidelines from compiled biological assessments. Biological effects from metal concentrations comparable to those found would be expected to be rare Elutriate testing designed to simulate sediment disruptions similar to dredging operations or major storm events were performed on the most highly contaminated sediments. Results indicate the release of metals into the water column, but at concentrations below the Louisiana Ambient Water Quality Criteria. Sediments displayed an inherent capacity to remove the released metals from the water column upon return to original conditions Sediment accumulation rates were determined from four cores using 210Pb geochronology. Compaction corrected accumulation rates varied from 0.1 to 0.28 cm/yr and were comparable to observed rates from Louisiana estuaries. Within Lake Salvador core intervals, concentrations of As, Ba, Cr, Cd, Pb, and Zn have increased by 10% to 30% in sediments accumulated within the last 50 years, though little variation was noted from sediments accumulated during the 1800's