Abstract: Depositional Characteristics of Sediments at Savannah Ocean-Disposal Site, Georgia

George F. Oertel

Yearly maintenance dredging is performed at the bar-channel system of the Savannah navigation channel. The prominent sources of material filling the channel are fine river deposits, littoral sands, and Pleistocene river gravels. Hopper dredges extract these materials from the floor of the navigation channel and deposit them offshore. Dredge material is released through doors in the hull of the ship, and sorted hydraulically as it settles through the water column. Coarse material generally accumulates in mounds directly under the depositional track of the dredges. Fine materials are dispersed greater distances away from the mounds by water currents.

Fines accumulate at depths below ambient wave base and remain stable during most nonstorm conditions. Bottom stability is indicated by subdued relief at the water-sediment interface and relatively intense bioturbation in the substrate. Coarse material forms mounds and wave turbulence and current velocities are greatest near the water surface causing fines to be winnowed out of mounds. A relatively active sediment carpet on the mounds is indicated by ripples and megaripples. Surveys have indicated that the coarse mounds become asymmetrical and may move as units during major storms.

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