Micropaleontology of Foraminifera from the Upper Jurassic of the Chellala Mountains

Abstract

Based on the geological investigations carried out on the Upper Jurassic succession of the eastern Chellala Mountains, located along the Algerian Atlas margin, significant progress has been achieved in understanding the lithostratigraphic, sedimentological, and micropaleontological evolution of the Djebel Harraza area. The studied Lower Kimmeridgian succession was subdivided into two distinct lithological units, reflecting variations in depositional conditions during sedimentation. Micropaleontological analysis of the collected samples revealed a diverse foraminiferal assemblage comprising 30 taxa, including both agglutinated and hyaline forms. The vertical distribution of these taxa allowed the recognition of three characteristic foraminiferal assemblages, providing a refined biostratigraphic framework for the Lower Kimmeridgian succession. From a paleoenvironmental perspective, the integration of foraminiferal assemblages with sedimentological observations indicates that the depositional environment experienced successive variations in water depth. These environmental changes were primarily controlled by eustatic sea-level fluctuations, which influenced the distribution of foraminiferal communities and the evolution of the depositional settings throughout the studied interval.