The Coniacian-Santonian series in the Aures Mountains of northeastern Algeria is characterized by marly-dominated sedimentation processes. This study aims to comprehensively investigate this series by combining lithostratigraphic and biostratigraphic data. The unique paleogeographic position of the Aures basin supports the co-occurrence of diverse paleontological contents in the Upper Cretaceous sediments. The methodology employed in this study includes a detailed bio-lithostratigraphic analysis to subdivide the Coniacian-Santonian series into two distinct sets. The first set comprises alternating marl-limestone units that exhibit a high fossil concentration from the Coniacian age, while the second set mainly consists of marly sediments corresponding to the Santonian age. The results obtained from this study highlight the geographical distribution of litho-biostratigraphic characteristics and reveal the presence of two formations. The lower formation is characterized by carbonated marls intercalated with limestone banks, containing fossils of Peroniceras (Tissotia tissoto) from the Coniacian age. Meanwhile, the upper formation is predominantly marly and indicates the Santonian age by displaying fossils of Palcenticeras polypsis. Furthermore, a biostratigraphic analysis focused on foraminifers allows for the subdivision of the Coniacian-Santonian series in the Aures Mountains into three distinct biozones. The first biozone corresponds to the lower Coniacian age and is identified by the presence of Dicarinella primitiva. The second biozone represents the middle to upper coniacian age and contains Dicarinella concavata fossils. Finally, the third biozone, belonging to the Santonian age, is marked by the occurrence of Dicarinella asymetrica. The boundary between the Coniacian and Santonian series in the Aures Mountains is characterized by the first appearance of Dicarinella asymetrica and Palcenticeras polypsis species. This multidisciplinary study provides valuable insights into the litho-biostratigraphic characteristics and geographical distribution of the Coniacian-Santonian series in the Aures Mountains. The findings make a significant contribution to a better understanding of sedimentary processes and the paleontological content within this region during the Upper Cretaceous period.