Abstract: Shelf-Sediment Dynamics and Solid-Waste Disposal

D. S. Gorsline

Most historic disposal sites are on the continental margins in depths of less than 100 m. Within those depths the major agents of sediment dispersal are surface waves of all periods including tides, wind-generated and sometimes thermohaline currents, and internal waves. The application of this spectrum of forces depends on latitude, shelf relief, climatic regime, and the ratio of normal conditions to storm conditions and of storm frequency.

The resulting pattern of energy application together with the location of sediment sources, rates of input, and nature of the sediment input determines the areas of erosion and deposition and produces a surface distribution of sediment types. Obviously, the best locales for solid-waste disposal, if dispersal is desired, would be regions of high-energy systems. If a fixed or nondispersive mode is the desired objective, low-energy systems perhaps would be best. In either example, pretreatment might be required to enhance the response of the waste to the shelf energy regime.

Shelf dispersal systems obviously must be defined to determine the acceptability of disposal. Because sediments in nature move by reason of their hydraulic characteristics (simplified to size and relative density), a necessary prerequisite for disposal is to determine the hydraulic equivalence of the solid wastes. If these two are known, the capacity of the given shelf can be determined readily. The definition of capacity, in turn, will depend on the acceptable levels of such factors as water turbidity, sediment-type changes, and resulting bioeffects. The comparative effects of normal energy levels and of storm levels must be known. Particulates move by floating, suspension, and bottom traction and of these the most critical probably are floating and suspension, for they represent the modes of fastest transport. We know least about bed-load and floating-transport processes. These considerations will define the areas of primary research needs.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC