Continental Shelf Sediments Off Northeastern Asia

Abstract

ABSTRACT About 260 sediment samples from the continental shelves off Vladivostok, Kamchatka, and in the Bering Sea were examined and mapped as the third of a series of studies of sediments off the Asiatic coast by the authors. The results show that biogenic calcium carbonate (mostly foraminiferal tests and mollusk shells) is much less abundant than in sediments farther south where the water temperature and salinity are higher. In contrast, amorphous silica (from diatom tests and sponge spicules) is more abundant than farther south, owing to the well known greater content of dissolved silica in northern waters. Organic matter exhibits less dependence upon latitude than upon the grain size of its enclosing sediment. In addition to modern biogenic components, the sediments contain an abundant rel ct detrital component (especially off Kamchatka) left from times of glacially lowered sea level. The major component is modern detrital sediment contributed by streams and marine erosion and distributed by currents across the narrow shelves. Off Vladivostok the modern detrital component apparently has completely buried the earlier relict component, but off Kamchatka the supply of sediment is insufficient, and in the Bering Sea the shelf area is so great that modern detrital sediments have been unable to bury the relict component.