Abstract

Sediment (deposits of unconsolidated material) on the continental shelf is affected by two groups of sedimentary processes that differ in nature and disposition with time. One of these groups of processes supplies particles to the shelf, and if it does so at present, we may say that the particles are now being supplied; otherwise the particles were supplied in the past. The other group of processes distributes the particles on the shelf to form them into sedimentary deposits; if this group is operating at present, we may say that the resulting deposits are modern; otherwise they are relict.

The interrelations of these two groups of processes are used to classify shelf sediment into five classes of sediment process-age: Neoteric sediment is a modern deposit that consists of particles now being supplied to the shelf. Proteric sediment is a modern deposit that consists of particles supplied to the shelf before the present. Amphoteric sediment is a modern deposit that consists not only of particles now being supplied to the shelf but also of particles that were supplied to the shelf before the present. Palimpsest sediment is a relict deposit that mainly contains particles supplied to the shelf before the present but also includes some particles now being supplied to the shelf. And relict sediment is a relict deposit that consists solely of particles supplied to the shelf before the present. At a given locality, the duration of present conditions varies with the intensity of the sedimentary processes; between localities, the duration varies inversely with the rate of sediment accumulation.

This classification can be used in conjunction with measurements of sedimentary processes on the shelf. For example, measurements of processes that distribute sediment to form deposits may be of direct use in explaining neoteric, proteric, or amphoteric sediment but of no use in explaining palimpsest or relict sediment. And measurements of processes that supply particles to the shelf may be of direct use in explaining the presence of particles in neoteric sediment and of some but not all particles in amphoteric or palimpsest sediment but of no use in explaining particles in proteric or relict sediment.

These expanded concepts that concern modern and relict sediments are aimed at assisting the extrapolation of measurements of sedimentary processes into unmonitored areas of the shelf.

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