Micropaleontological study (foraminifera, ostracods) and characterization of the paleoenvironment of middle Cretaceous deposits (Djebel Chemla area, north-eastern Algeria)

Abstract

The Djebel Chemla section is situated in the north-east of Algeria, close to the town of Tébessa and just a few kilometers from the Tunisian border. This section is composed mainly of a sequence of marl and marly limestone levels, alternating with recurring oyster levels which range in age from Vraconnian to the Early Turonian. Firstly, the micropaleontological study of the content (counting of foraminifera and ostracods, thin sections) allows the subdivision of the section into four biozones, with Rotalipora appenninica, Rotalipora globotruncanoides, Rotalipora cushmani, and Whiteinella archaeocretacea as bio-indicators; and, secondly, it provides the opportunity to specify the paleoenvironment. The supposed depositional environment is rather calm and deep, of an external platform type, with a maximum depth of 200 m. Bottom waters seem to be commonly poorly oxygenated. The end-Cenomanian anoxic crisis was also characterized by the presence of Bahloul facies levels, rich in TOC, in filaments and of globulous planktic foraminifera, including a considerable proportion of Heterohelix. The genus Rotalipora has disappeared a few levels lower down.

Quantitative analysis and paleoenvironmental reconstruction of the middle Cenomanian deposits from southern Bellezma-Batna Mountains (northeastern Algeria)

“…Most stratigraphic and sedimentological studies of northeastern Algeria and Bellezma-Batna Mountains have been focused mainly on fossil bioaccumulations at the Cenomanian-Turonian boundary (Chikhi-Aouimeur, 1983, 1998, 2010Herkat, 2007;Grosheny et al, 2008;Ruault-Djerrab& Kechid-Benkherouf, 2010;Chikhi-Aouimeur et al, 2011;Ruault-Djerrab et al, 2012;Aouissi et al, 2018Aouissi et al, , 2022Slami et al, 2018;Bensekhria et al, 2019, Mendir et al, 2019Benmansour, 2023). However, paleoenvironmental investigations in this area have not been undertaken since the study of Yahiaoui (1990).…”