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The geochemical investigation of 42 clayey samples spanning the uppermost Maastrichtian–lower Danian boundary event in Tamerza, Gafsa Basin, Tunisia, can reveal information related to the fluctuations of pH, carbonate saturation, and redox conditions. Geochemical proxies, including the CaCO3 percentages, the Ca concentrations, the Al-normalized trace-element redox concentrations (Mo/Al, V/Al, Cr/Al, and Zn/Al), and the V/Cr ratio show that the uppermost Maastrichtian–lower Danian marine sediments had experienced variable degrees of carbonate undersaturation and oxygen depletion. The use of multivariate (principal component analysis) and univariate (one-way ANOVA test) analysis allowed to discriminate this event into three statically significant different geochemical Units (P < 0.001). The simultaneous noteworthy decrease in Ca and CaCO3 and enrichment in the V/Cr, Mo/Al, V/Al, Cr/Al, and Zn/Al ratios suggest a pH drop and dissolved oxygen within Unit 1. The decrease of Al-normalized trace-element redox concentrations (Mo/Al, V/Al, Zn/Al, Cr/Al, and Zn/Al) and the V/Cr ratio within Unit 2 are weighted toward oxic conditions and marine ecosystem restoration. However, the abrupt drop of CaCO3 (~0%) and Ca concentrations emphasizes the severe carbonate undersaturation in this Unit. The expansion of carbonate-depleted water in the Tamerza area could explain the abundance of dissolved and fragmented shells and the primary damage of morphological characteristics of benthic foraminifera. On the contrary, Unit 3 shows significant CaCO3 and [Ca] increase and exhibits the maximum values of Mo/Al, V/Al, Cr/Al, Zn/Al, and the V/Cr ratios. Although the carbonate saturation recovered, the fauna suffered severe anoxic conditions in Unit 3. The sulfidic environment had hampered the benthic foraminifera blossoming.

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Geochemical Disturbance and Paleoenvironmental Changes During the Uppermost Maastrichtian–Lower Danian Boundary Event in Gafsa Basin (Tamerza, Tunisia)

  • 会议论文

  • 发表日期：

    2025年

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  • Noura Kotti,
  • Salma Jmal,
  • Ignacio Arenillas,
  • Jamel Abdennaceur Ouali,
  • Besma Mardassi

摘要

The geochemical investigation of 42 clayey samples spanning the uppermost Maastrichtian–lower Danian boundary event in Tamerza, Gafsa Basin, Tunisia, can reveal information related to the fluctuations of pH, carbonate saturation, and redox conditions. Geochemical proxies, including the CaCO3 percentages, the Ca concentrations, the Al-normalized trace-element redox concentrations (Mo/Al, V/Al, Cr/Al, and Zn/Al), and the V/Cr ratio show that the uppermost Maastrichtian–lower Danian marine sediments had experienced variable degrees of carbonate undersaturation and oxygen depletion. The use of multivariate (principal component analysis) and univariate (one-way ANOVA test) analysis allowed to discriminate this event into three statically significant different geochemical Units (P < 0.001). The simultaneous noteworthy decrease in Ca and CaCO3 and enrichment in the V/Cr, Mo/Al, V/Al, Cr/Al, and Zn/Al ratios suggest a pH drop and dissolved oxygen within Unit 1. The decrease of Al-normalized trace-element redox concentrations (Mo/Al, V/Al, Zn/Al, Cr/Al, and Zn/Al) and the V/Cr ratio within Unit 2 are weighted toward oxic conditions and marine ecosystem restoration. However, the abrupt drop of CaCO3 (~0%) and Ca concentrations emphasizes the severe carbonate undersaturation in this Unit. The expansion of carbonate-depleted water in the Tamerza area could explain the abundance of dissolved and fragmented shells and the primary damage of morphological characteristics of benthic foraminifera. On the contrary, Unit 3 shows significant CaCO3 and [Ca] increase and exhibits the maximum values of Mo/Al, V/Al, Cr/Al, Zn/Al, and the V/Cr ratios. Although the carbonate saturation recovered, the fauna suffered severe anoxic conditions in Unit 3. The sulfidic environment had hampered the benthic foraminifera blossoming.