Comparative Sedimentology of Three Tunisian Lagoons

Duncan Heron, Orrin Pilkey

Three major lagoons indent the Tunisia shoreline. The Lake of Bizerte in north Tunisia is in the Mediterranean climatic zone. Bahiret el Bibane, 450 km to the south near the Libyan border, is in an arid setting. The Lake of Tunis, 50 km south of the Lake of Bizerte, is in a semiarid setting. Summer salinities of the three lagoons reflect the climatic differences. Bahiret el Bibane is relatively unaffected by man's activities. The principal alteration of the Lake of Bizerte is deepening of the channel to the Mediterranean. The Lake of Tunis has been profoundly impacted through infilling (an ongoing process), construction of a diked ship channel, and introduction of large amounts of raw sewage.

The sediments of the semirestricted Bahiret el Bibane are dominated by biogenic fragments (mostly mollusks) but with an important wind-transported detrital component. The Lake of Bizerte has a minor wind component and is dominated by mud-size clastics from streams draining farmlands; in addition there is an important biogenic contribution. In the Lake of Tunis, calcareous worm reefs flourish because of the high nutrient content and further restrict the circulation already restricted by the ship channel. This leads to frequent summer eutrophication. The most important sediment in the Lake of Tunis is an organic-rich terrigenous mud derived from the adjacent drainage basin, but biogenic productivity is high and may form a locally dominant component. There is also a small wind-introduced component.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.