Coastal dynamics and the evolution of the Acholla lagoon (Gulf of Gabes, Tunisia): a multiproxy approach
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Arabian Journal of Geosciences. 2021-09-16, vol. 14, n° 19
Resumen en inglés
This study explores the paleoenvironmental changes of the Acholla coast over the last 2000 years by means of subsurface sediment analyses of lagoonal deposits via a multiproxy approach. A sequence of 5 steps is shown to ...Leer más >
This study explores the paleoenvironmental changes of the Acholla coast over the last 2000 years by means of subsurface sediment analyses of lagoonal deposits via a multiproxy approach. A sequence of 5 steps is shown to have shaped the coastal development at Acholla and includes (i) the settlement of an open marine embayment during the Upper Pleistocene (substage 5e) in response to a transgressive event as evidenced by the deposition of carbonate sandstones rich in mollusc associations and marine elemental ratios Sr/Al, Ca/Al, Cl/Al, and S/Al; (ii) a sea-level rise towards183 AD, after a long period of emergence of the coast, leading to transgressive deposits of poorly sorted fine sands that are rich in diversified mollusc and ostracod taxa; (iii) a high-energy event (towards 417AD) with a peculiar biofacies characterized by coarse bioclastic mollusc-rich sands, charcoal particles, Tyrrhenian lithoclasts, and high values of marine elemental ratios Cl/Al, S/Al, and Ca/Al; (iv) a progradation of coastal habitats (between 417 and 1577 AD), favored by a period of flooding/detrital input and longshore current drifts, resulting in the development of an extensive sandspit and the formation of the Acholla lagoon. The construction of a Roman pier, originally constructed to protect the Acholla harbor from sedimentation, was counterproductive and favored the expansion of coastal swash bars and extension of the sandspit, ultimately resulting in the abandonment of the Acholla harbor; (v) the closure of the lagoon (from 1577 AD onward) and the built-up of well-sorted silt deposits are marked by the decrease of detrital elemental ratios (Ti/Al, Si/Al, and K/Al) and by reduced ostracod species richness values. The inferred scenario for the evolution at Acholla coast matches those for Sfax and Skhira coast in the Gulf of Gabes (Tunisia). Unlike Sfax and Skhira, however, the Acholla coast has been subjected to uplift by active faults, resulting in a time shift of depositional patterns. © 2021, Saudi Society for Geosciences.< Leer menos
Palabras clave en inglés
Ostracods
Sea level
Acholla lagoon
Roman harbor
Holocene
Sandspit
Paleogeography
Tunisia
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