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

• Published in: Arabian journal of geosciences 2019-05, Vol.12 (9), p.1-11, Article 296
• Main Authors: Gammoudi, Amal, Essefi, Elhoucine, Rigane, Hafedh
• Format: Article
• Language: English
• Subjects: Astronomy; Celestial bodies; Clay; Climate change; Climatic conditions; Climatology; Cycles; Dynamics; Earth and Environmental Science; Earth science; Earth Sciences; Geographical locations; Holocene; Mathematical analysis; Original Paper; Solar activity; Spectral analysis; Stratigraphy; Thermohaline circulation; Variability
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-019-4472-3

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 (≈ 2600 yr. BP). A high-resolution sampling of 3 mm was carried out (335 samples). In terms of analyses, different fractions were recuperated based on five sieves (50, 63, 100, 250, and 500 μm). Based on the spectral analysis, we found out cycles of ≈ 2000, 1700, 1500, 1300, 700–800, 630, 533, 433–383, and 122 years. The 1700 yr. cycle is related to the oceanic activity. Also, the 1500-year and 700–800 yr. cycles are possibly related to the oceanic thermohaline circulation. About 1500 years 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 years and 630 yr. cycles have a link with the North Atlantic fluctuations. About 500 yr. cycles are may be related to the solar activity. About 433–383 years and 122 yr. cycles are possibly linked to other atmospheric and oceanographic forcings.