Variability of the grain-sized fractions during the last three millennia within the sedimentary fillings of the saline system of Mhabeul: the Holocene cyclostratigraphy

Abstract

Cyclostratigraphy is the study of cyclicity potentially recorded in sedimentary series. It is a specific method of stratigraphy studying the succession of different geological layers, based on results of climatology, astronomy, and mathematical techniques. Cyclostratigraphic signal, showing distinct orders of sedimentary cyclicities, is the result of variations in a climatic variable. Indeed, the Milankovitch theory, corresponding to the ancient cyclostratigraphy, is related to geographical locations and orbital factors, though the Holocene cyclostratigraphy is related to the solar activity and other oceanographic and astronomical factors. This study aims to infer the climatic signal within the sedimentary filling of sebkha Mhabeul, relying on the study of the grain-sized distribution, specifically the variability of the silty and sandy fractions. Previous granulometric study of the clay pan of Mhabeul (Essefi et al., J Basic Appl Res Int 15(2–4):140–152, 2015a) showed the importance of coarse fractions to highlight changes related to the sedimentary dynamics. Indeed, the percentages of different sandy and silty fractions contribute to the understanding of climatic conditions and the depositional environment. This work is meant to study the climatic cyclicity along a 100.5-cm core (Mh 1) from the saline system of Mhabeul, located in southeastern Tunisia through the grain-sized fractions. Based on the age model of Marquer et al. (Quat Res 70:240–250, 2008), the core covers the last three millennia (≈\u20092600\xa0yr. BP). A high-resolution sampling of 3\xa0mm was carried out (335 samples). In terms of analyses, different fractions were recuperated based on five sieves (50, 63, 100, 250, and 500\xa0μm). Based on the spectral analysis, we found out cycles of ≈\u20092000, 1700, 1500, 1300, 700–800, 630, 533, 433–383, and 122\xa0years. The 1700\xa0yr. cycle is related to the oceanic activity. Also, the 1500-year and 700–800\xa0yr. cycles are possibly related to the oceanic thermohaline circulation. About 1500\xa0years can have a link with a NAO-like circulation. The 2000-yr. cycle is related to the solar activity and the monsoonal regime. About 1300\xa0years and 630\xa0yr. cycles have a link with the North Atlantic fluctuations. About 500\xa0yr. cycles are may be related to the solar activity. About 433–383\xa0years and 122\xa0yr. cycles are possibly linked to other atmospheric and oceanographic forcings.