Holocene paleoenvironmental change in inner continental shelf sediments, Southeastern Mediterranean, Egypt

Abstract

The palynology of marine sediments from CS Core taken on the inner continental shelf offshore Nile Delta, Southeastern Mediterranean, has been used to reconstruct the regional paleoenvironment during the past 5380 yr BP. This includes detailing the relative abundances of dinoflagellate cysts, acritarchs, prasinophytes and other algal spores, microforaminiferal linings, crustacean eggs, and fungal hyphae. The composition and ecological interpretation of the dinoflagellate cyst assemblages, acritarchs and other non-pollen palynomorphs is discussed. Concentrations of dinoflagellate cysts range from 5926 to 416 specimens per gram of sediment, and the most common taxa were Lingulodinium machaerophorum, Operculodinium centrocarpum, Operculodinium israelianum, Polysphaeridium zoharyi, Spiniferites ramosus, Spiniferites mirabilis, Echinidinium transparantum and Protoperidinum nudum. The assemblages are like those on the Tunisian Shelf, but with more protoperidinioid cysts. It is concluded that the shelf sediments were deposited under suboxic bottom water conditions. A high nutrient supply to the area during the deposition of the CS Core sediments is evidenced by the strong significant correlation ( R-values) between the nutrient-demanding species, L. machaerophorum and P. zoharyi, toxic species, total phosphorous percent (TP%) and total organic carbon percent (TOC%). These data suggest that Nile discharge from the Damietta Channel increased during the past 5830 yr BP and was accompanied by increases in fresh or brackish water algae and fungal hyphae.