Chemical variations in sedimentary facies of an inner continental shelf environment,Northern Gulf of Mexico

Four major sedimentary provinces of the inner continental shelf off the Louisiana coast have been recognized by textural studies (Krawiec, 1966): deltaic, non-deltaic, and relict sediments; and deltadestructional sands. Samples from these provinces have been analyzed for Rb, Sr, Ni, Fe,Mn, Ti, and Zr; trend surface analysis has been used to discern regional trends of these elements. These trends substantiate the previous division of shelf provinces. Although deltaic and non-deltaic sediments cannot be distinguished by chemical criteria, they are distinctive from relict sediments, which are low in Mn, Fe, Ti, Zr, Rb, and Ni, and high in Sr. The delta-destructional sands are distinctive from the other three provinces by their low contents of Mn, Fe, Rb, and Ni, and high Ti, Zr, and Sr.In an energetic environment such as this, processes subsequent to deposition tend to disperse Rb, Fe, Ni, and Mn, as these elements are closely associated with the clays; these processes may give rise to enrichment of Zr due to the high stability and density of the mineral zircon, or the enrichment of Sr by accumulation of organic remains.