Sedimentation, accretion, and subsidence in marshes of Barataria Basin, Louisiana1

Abstract

Vertical accretion and sediment accumulation rates were determined from the distribution of 137 Cs in cores collected from freshwater, intermediate, brackish, and salt marshes in the Barataria Basin, Louisiana. Vertical accretion rates vary from about 1.3 cm · yr −1 in levee areas to 0.7 in backmarshes. Mineral sediment content of the marsh soil profile decreased with distance from the coast. However, vertical accretion rates were about equivalent in areas of the same type. Autochthonous organic matter appears to be an important factor defining the process and rate of vertical accretion, especially in the freshwater marshes. Except in natural levee areas, marsh accretion rates are less than subsidence measured by water level data, however this alone cannot account for observed land‐loss patterns in the basin area.