Surface Sediments of the Nazca Plate

Abstract

A new surface sediment distribution map of the southeast Pacific Ocean has been compiled from approximately 800 existing samples. Ridge sediments are characterized by calcareous ooze; deep ocean basin sediments by clay; trench sediments by mud; and continental margin sediments by mud or material of sand size or larger. Siliceous oozes are generally absent largely because of dilution by calcareous material near the equator and terrigenous material near the continent, and because of dissolution in the water column and on the sea floor. Some sediments on the East Pacific Rise and in the Bauer Depression are markedly enriched in iron and manganese, whereas, in other areas, concentrations of transition metals are confined to nodules. Organic carbon values in bottom sediments bear a direct relationship to the productivity of the overlying surface waters, and range up to 6.9 percent in a strongly upwelling area. Pyroclastic material is more widespread off Peru than Chile. This may be due to easterly upper trophosphere winds over Peru and westerly upper trophosphere winds over Chile.