Stratigraphy and sedimentology of the upper Cenomanian–lower Coniacian in the Northern Aures Range (Algeria)

Abstract

The stratigraphical features and palaeoenvironmental conditions of the upper Cenomanian–lower Coniacian carbonates from the northern part of the Aures Range are described for the first time. Four formations have been recognised, namely the Arris, Adahri, Yabous, and Bou Ouali, respectively. Planktonic foraminifera enable us to assign the upper part of the Arris Formation and the lower part of the Adahri Formation to the Middle–Upper Cenomanian (Rotalipora sp. cf. R. cushmani Total Range Zone), the upper part of the Adahri Formation to the Cenomanian–Turonian Transition to the lower Turonian (Whiteinella archaeocretacea Partial Range Zone and Helvetoglobotruncana helvetica Total-Range Zone, respectively), the lower member of the Yabous Formation to the middle Turonian (Marginotruncana sigali Partial Range Zone), and the upper member of the Yabous Formation to the upper Turonian (Marginotruncana schneegansi Partial Range Zone). The Turonian–Coniancian boundary was dated approximately. This biozonation enables a correlation with several upper Cenomanian–lower Coniacian sections outside Algeria, mainly within the Tethyan and Boreal domains. Based on the field data, and microfacies studies, the strata of these formations are arranged into eleven microfacies types (MT 1 to MT 11) that are described in terms of depositional environments, and grouped into three main facies associations (FA 1, FA 2, and FA 3): (i) a deep shelf-basin facies zone; (ii) marginal sand shoals, an open-marine/restricted platform facies zone; and (iii) an outer platform and toe-of-slope/distal slope facies zone. Analysis of the sequence stratigraphy has allowed the recognition of three third-order depositional sequences grouped into two megasequences and correlated to a regional scale.