Foraminiferal and Geochemical Input to OAE 2 Event at Jebel Bou Arif (Aures, Eastern Algeria)

Abstract

To highlight the anoxic event (OAE2) in the Aurès, a multidisciplinary study was conducted on the northern slope of Djebel Bou Arif (Aurès) where the sedimentation is marked by (1) marl-limestone deposits rich in bivalves and echinids and by foraminiferal limestones of the lower Turonian represented by Whiteinella archeocretacea [1], Helvetoglobotruncana Helvetica [2], Heterohelix sp. Microfacial analysis coupled with foraminiferal counting results, for quantitative and qualitative analyzes to calculate bioeonotic indices, demonstrated periods of basin instability. Two peaks of faunal renewal were observed. The first occurred at the Cenomanian-Turonian passage. It coincides with the anoxic event OAE₂ and the second during the Middle Turonian. The interpretation of the geochemical results (CaCO₃, TOC: Total Organic Carbone, δ¹³C and δ¹⁸O) indicates the presence of an important anoxic phase that starts in the Whiteinella archeocretacea zone and increases at the base of the Helvetoglobotruncana helvetica zone. The presence of organic matter associated with the evolutionary response of benthic foraminifera preceding the δ¹³C isotopic signal explains a well-marked transgressive regime.