An application of foraminiferal ecology Vicinity of Horn Island, Mississippi

Foraminifera were examined in 159 samples cut from 23 piston c ores collected in the vicinity of Horn Island, Mississippi. The age of the oldest marine sediment cored is approximately 5000 years . The following data on depositional surface Foraminifera were determined and compared with those data from reports on similar areas: (a) specific composition, (b) percentage of arenaceous Foraminifera, (c) numbers of species, (d) specific dominance, and (e) numbers of specimens. These date show that environments of core samples can be determined by their foraminiferal content and such interpretation utilized to reconstruct the depositional history of an area. A non-marine clay and sand existed in the area at a time when sea level was lower. As sea level rose, nearshore marine deposition occurred in the present open-gulf area . Alternating brackish and near-marine conditions existed in the present Sound area. A barrier island system, established early in the period of core sediment deposition, offered varying degrees of resistance to the invasion of marine waters. As deposition continued, a "near-delta" influence was impressed upon the area. This influence existed throughout most of the depositional period. At present, a brackish environment exists north of Horn Island and a marine environment occurs south of the island. Mixing of these environments occurs in the passe s on each end of Horn Island. The island acts as a barrier to marine water, and brackish water from the Sound now dilutes the open gulf to a greater extent than in t he past. The "near-delta" influence is now negligible .