Stratigraphy and sedimentology of the uppermost Albian-lower Turonian of the Morsott area (Algero-Tunisian Atlasic Basin)

The stratigraphical features and palaeoenvironmental conditions of the uppermost Albian-lower Turonian succession of the eastern Algerian Saharan Atlas domain are described for the first time. Two formations have been recognised, called the Ouled Serradj and the Chemla, respectively. Ammonites and calcareous nannofossils enable us to assign the Ouled Serradj Formation to the upper Albian-Cenomanian and the Chemla Formation to the uppermost Cenomanian-lower Turonian. Based on the field data and microfacies studies, the strata of these formations are arranged into eight microfacies types (MT 1 to MT 8) that are described in terms of depositional environments and grouped into three main facies associations (FA-1 to FA-3): FA-1 (MT 1–4), deep-water outer platform marl-dominated facies association 1 with limestone intercalations; FA-2 (MT 5 and 6), mid-platform marl-dominated facies association 2; and FA-3 (MT 7 and 8), mid- and inner platform limestone-marl facies association 3.