Journal article Open Access
Bourhim, Loubna; Amhoud, Hamid; Sadki, Driss; Ait Addi, Abdellah; Chbani, Boumediane; Akasbi, Ayad
Benthic foraminifera from the Middle Jurassic of the Rich-Gourrama (High Atlas, Morocco) : biostratigraphy, faunal renewal and adaptive strategies. - The stratigraphic distribution of the main benthic foraminifera recorded from the Middle Jurassic (Aalenian to basal Bathonian) of the Central Eastern High Atlas (Rich-Gourrama area) shows a succession of different changes in the benthic foraminiferal associations. The analyses of the associations allowed us : - to establish a biostratigraphic scale thanks to the index species. Four associations comparable to those identified in other Moroccan basins for the same period are recognized : (1) association with Lenticulina galeata and Garantella ampasindavaensis, (2) association with Lenticulina quenstedti and Garantella stallata, (3) association marked by the proliferation of agglutinated species of genus Lenticulina, with test ribbed and unrolled, and (4) association with predominantly agglutinated forms ; - to follow the evolution of microfaunal populations in relation with palaeoenvironmental changes (bathymetry, oxygenation, substrate nature, etc.). These changes are witnessed by the foraminiferal record highlighting different adaptive strategies, expressed by morphological changes concerning, inter alia, the form of the test, the winding mode and the external surface of the test. Consequently, the relative frequencies of foraminiferal populations during this period show an eco-sequence in perfect agreement with the evolution of deposits.