| South Sound, a 3.4 km2, shallow (<2 m), shoreline-parallel, funnel-shaped lagoon, is located on the southwest exposed windward margin of Grand Cayman. The facies, which are defined by biota, grain-size, sorting and skewness are: Thalassia, Sand, Rock Bottom, Brown Algae, Rubble, and Coral Head. Between 1971 and 1992, the Thalassia Facies expanded in area by 17.3%, mostly at the expense of the Sand Facies.;Under fair-weather conditions, sediment production, bioturbation, and Thalassia colonization dominate. The northeast trade winds and lagoonal geometry and orientation, however, induce currents almost everyday that increase in magnitude from east to west. These currents rework and redistribute the sediments to produce accumulations that are thick and fine-grained in the east and close to shore, and sporadic and coarse-grained in the west. Hurricanes enhance the effects of everyday currents, but their force is concentrated on the reef crest. Coral fragments (dominantly Acropora palmata) broken from the reef crest produce a concentrated rubble belt directly behind the reef. Areas of Thalassia are ripped-up by storms, but are maintained grass-free by everyday currents. |
