Geochemistry and Sedimentary Sources of the Surface Sediments from the Continental Shelf off the Indus Delta, Pakistan

Abstract

This study focuses on the spatial distribution of the major and minor elements (Al, Ca, Fe, K, Ti, Ba, Sr, V, Zn, Cr, Ni, Li, Zr, Cu, and Co) and the textural characteristics of the surface sediments from the continental shelf off the Indus delta, Pakistan. The sediments from the inner shelf near the Indus River mouth and around the Indus canyon towards the outer shelf region are fine-grained clayey silt with low (~30%) carbonate. The coarse-grained sediments, high (40–70%) in carbonate with abundant skeletal material cover the western shelf area. The inter-element relationship, elements distribution, and associated textural characteristics of the sediments suggest a common detrital source except for Ca. The concentration of the major elements (Al, Fe, K and Ti) and the trace elements (Ba, V, Zn, Cr, Ni, Li, Zr, Cu, and Co) is highest in the silty clayey sediments from the inner shelf and near the Indus River mouth, around the Indus canyon and towards the outer shelf region. The Indus River sediments are the major contributing source of these elements. A relatively high concentration of Cr, Zr, Ni, Zn and Cu in the sediments from the western shelf area imply a source different from the major Indus River probably from the western Makran or Murray ridge zone. Association of Ca and Sr with CaCO3 in the western and central west area of the Indus shelf suggests that calcareous skeletal fragments are the main contributor of these elements in the surface sediments that contain 40–70% carbonate.