Spectral Analysis of a Core from the Sebkha of Sidi Mansour, Southern Tunisia: The Holocene Cyclostratigraphy

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.