Genesis and Evolution of A Beach-Ridge Plain Reflecting Relative Sea-Level Rise: A Case Study From Trab El Makhadha Gulf of Gabes, Southeastern Tunisia

Abstract

Abstract The Trab El Makhadha beach-ridge plain presents a progradational shoreline feature on the Gulf of Gabes (Tunisia). Diachronic analysis coupled with a morpho-sedimentary approach was applied to elucidate the genesis mode of the beach-ridge plain, its sedimentary sources, and the climatic conditions responsible for the prograding trends in the Gulf of Gabes. Shapes, dimensions, sedimentologic compositions, and other textural parameters of the sandy ridges have been analyzed. Therein, we found that the Trab El Makhdha Coast is made up of two distinctive categories of eolian beach-ridge complex (progradational sequences), implying a significant change in climatic and hydrological conditions during the deposition of each ridge. In the Holocene sequence, about 5600 14C years old, the predominance of detrital material suggests an important contribution to sediment supply from continental input. The preservation of the eolian beach ridge and its adjacent marine sediment has been favored by the postglacial hydro-isostatic rebound. Today, the paucity of rainfall is reflected by the decrease in input of terrigenous material. Therefore, the modern sequence, which has been emerging since 1987, is made mainly of bioclastic sand supplied by subaqueous shoals due to a rapid rise in sea level. The observed decrease of sea level around 2100 14C yr B.P. largely contributed to the formation of the swale. The formation of the beach-ridge plain shows that since the middle Holocene highstand the coastal segment of Trab El Makhadha has been governed by equilibrium of sediment abundance.