COMPOSITION AND MASS FLUX OF SEDIMENT ENTERING THE WORLDS SUBDUCTION ZONES: IMPLICATIONS FOR GLOBAL SEDIMENT BUDGETS, GREAT EARTHQUAKES, AND VOLCANISM

Abstract

Lithologic data compiled from Deep Sea Drilling Project and Ocean Drilling Program sites, when combined with orthogonal convergence rates at convergent plate boundaries, permit quantification of the mass flux of sediment into subduction zones. We have made such calculations for each major sediment component -- terrigenous grains, calcium carbonate, opal, and water -- for twelve trench systems. Results show that 1.4 x 10^15 g/yr of sediment and 0.9 x 10^15 g/yr of water enter the trenches in the oceanic sedimentary layer. Most of the entering sediment, 1.1 x 10^15 g/yr, is terrigenous; the remainder is more carbonate than opal. For most of geologic time an order of magnitude more sediment enters the ocean than leaves it via subduction. The global sedimentary cycle need be in balance only over an entire Wilson cycle. Comparison of sediment fluxes into trenches with the magnitude of large earthquakes and with the composition of bulk volcanic rock shows no correlation.