Lithological Variations over the Last Two Millennia within the Sedimentary Fillings of El- Guettiate in South East Tunisia: The Holocene Cyclostratigraphy

Abstract

Abstract The Holocene sedimentary record of the Sebkha El Guettiate is located on the southern coast of Skhira, Gulf of Gabès in Tunisia. The cyclostratigraphic study depends on the idea that important segments of the stratigraphic record have recognizably encoded the orbital armature, periodic variations of the terrestrial insolation (Milankovitch cycles). It is a specific method of stratigraphy which studies the succession of different geological strata based on the results of climatology, astronomy and mathematical techniques. Holocene cyclostratigraphy is related to solar activity and other oceanographic and astronomical factors. This study aimed to test the climatic cyclicity along a core of Sebkha El-Guettiate located along the Mediterranean coast in Tunisia, by focusing on the study of the particle size distribution, in particular the variability of the sandy and silty fractions. Based on the dating of Zaibi et al. (2011) they were estimated to cover the last millennia with a sedimentation rate of 0.32 mm/year. This rate accepts the preparation of a depth-age model to perform the spectral analysis.Our analysis found cycles of ≈ 2000, ≈ 1600, 1300, 1000, 800, 595, 324 and 166 years. The 2000 year and 1000 year cycles are related to solar activity. The 1600 years cycle is likely related to internal forcing of the Atlantic Ocean. The 1300-year and 800-year cycles are probably related to the thermohaline circulation of the oceans. However, the other cycles of 600 years 324 years and 166 years are probably related to other oceanographic and atmospheric factors.