Mass/age distribution and composition of sediments on the ocean floor and the global rate of sediment subduction

The total mass of sediments on the ocean floor is estimated to be 262 × 10 21 g. The overall mass/age distribution is approximated by an exponential decay curve: (11.02 × 10 21 g) e −0.0355 t Ma. The mass/age distribution is a function of the area/age distribution of ocean crust, the supply of sediment to the deep sea, and submarine erosion and redeposition. About 140 × 10 21 g of the sediment on the ocean floor is pelagic sediment, consisting of about 74% CaCO 3 , with the remainder opaline silica and red clay. Of the sediment on the ocean floor, 122 × 10 21 g is detritus, mostly terrigenous, but a small portion (about 6 × 10 21 g) is volcanic. Because very little pelagic sediment is obducted, virtually all of the pelagic sediment mass and some fraction of the terrigenous sediment is being subducted at a rate estimated to be about 1 × 10 21 g per million years. The composition of sediment on the ocean floor differs significantly from that of average passive margin and continental sediment, so that the loss of ocean floor sediment through subduction may drive the composition of global sediment toward enrichment in silica, alumina, and potash and toward depletion in calcium.