Abstract
The Milancovitch Theory explaining the ancient cyclostratigraphy does not file a case for the Holocene cyclostratigraphy. Instead, other astronomical and oceanographic mechanisms control the cyclicity within Holocene sediment. This work aimed to find out the climatic cyclicity along a core from the sebkha of Sidi Mansour located along the Mediterranean coast in Tunisia, through using different proxies: the magnetic susceptibility, carbonate percentages and chemical elements (Ca, Na, and K). Based on previous radiocarbon and tephrochrnological dating in the study area, the core was estimated to cover the two last millennia with a sedimentation rate of 0.35 mm/yr. This rate allows the elaboration of a depth-age model to carry the spectral analysis. Not all the proxies visualize the same climatic cycles. For instance, the spectral analysis of the magnetic susceptibility and Sodium data visualized a 1000 yr cycle. The spectral analysis of Potassium data did not visualize significant cycles. The spectral analysis of the carbonate percentages and calcium data visualized dual cycles of 1700-700 yr and 493-329 yr respectively. The about 500 yr and 1000 yr cycles are related to Sun activity. Other oceanographic and atmospheric factors could generate other cycles of 1700 yr, 700 yr, 493 yr, and 329 yr. The majority of these cycles were worldwide recorded as interplay between the oceanography and the solar forcing. Contrary to the earth-driven cyclostratigraphy related to orbital parameters and geographical positions, the Holocene cyclostratigraphy is sun-driven.
Highlights
Sun activity and its effect on climatic cyclicityThe Milancovitch Theory explaining the ancient (e.g., Cretaceous and Miocene) cyclostratigraphy does not file a case for the Holocene cyclostratigraphy
The first part (25 cm) is characterized by a downward increasing of the magnetic susceptibility due to the coming of ferromagnetic and ferrimagnetic minerals from continental vicinity. As it was proven by Boyle et al [21], we can interpret this increase in magnetic susceptibility as a result of wet climatic conditions, which are the responsible agent for reaching the sebkha by an amount of detritic material via Wadis
The results prove that sodium is the most representative elements, whereas calcium and sodium exist with minor proportions
Summary
Sun activity and its effect on climatic cyclicityThe Milancovitch Theory explaining the ancient (e.g., Cretaceous and Miocene) cyclostratigraphy does not file a case for the Holocene cyclostratigraphy. The decadal to millennial scales cycles of the Late Holocene sediment in lakes and sebkhas recorded based on geophysical and geochemical parameters were less than likely explained by this Theory. Other astronomical and oceanographic causes have been recently highlighted to explain short climatic cycles [1,2,3,4,5,6]. The Gleissberg cycle (87 yr) is due to the variability in Sun diameter [11] Other cycles such as that of Vriès (210 yr) are still unknown [12]. In the westernmost Mediterranean Sea, major periodicities at 1300 yr and 1515 yr, linked with North Atlantic climate variability and the African monsoon system were found out along the past 20,000 yr. The aim was studying the Holocene cyclostratigraphy along a core from an endorheic system (sebkha Sidi Mansour) located at the coast of the Mediterranean Sea
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