Productivity and bottom water redox conditions at the Cenomanian-Turonian Oceanic Anoxic Event in the southern Tethyan margin, Tunisia
Résumé
In Tunisia, five Bahloul spaced sections, Bargou, Jerisa, Guern Halfaya, Kherij and Gafsa were analysed for major and trace elements. These high-resolution chemostratigraphic integrated analyses for the Late Cenomanian-Early Turonian Bahloul Formation provide new insight on the palaeoceanographic evolution of the southern Tethyan margin. Relative low abundance of related terrigenous Ti/Al and K/Al ratios and enrichment of some productivity proxies such as Ba, Cu, and Ni (organic matter related trace elements) suggests that the Bahloul, deposited during a relative short period (400 kyr), was of relatively elevated primary productivity and minimal detrital input. While higher D* values concurrent with lower Ti/Al ratios are interpreted as caused by enhanced fluvial material contribution, due to more humid climate during the OAE-2. Enhanced humidity triggered probable fluvial influxes, resulted in a sluggish water circulation and consequent anoxic/euxinic conditions favouring the preservation of organic matter at the sea floor. Enrichments in redox-sensitive trace metals U, V, and Mo in the Bahloul Formation deposits and redox indices, such as V/(V+Ni), U/Th, V/Cr, and Ni/Co, indicate that oxygen-restricted conditions prevailed during the Late Cenomanian - earliest Turonian times. High Baxs values and Uauth may indicate anoxic conditions at least at the water-sediment interface during the Bahloul Formation deposition and provide information about low to moderate sulphate-reduction reactions.
Domaines
Géologie appliquée
Origine : Fichiers produits par l'(les) auteur(s)
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