Paleobathymetric Influence on the Distribution of Ammonite and Foraminifer Settlements in the Callovian of the Saïda Region (Western Algeria)

Abstract

Saïda clay formation (NW Algeria) of Callovian-Oxfordian age is widespread in the Tlemcenian Domain. In the Saida region, its lower limit is placed above a general gap of the upper Bathonian age. Its upper limit is overlaid by the first coarser sandstone beds (Bou-Medine Sandstone Fm) belonging to the Oxfordian. The Saïda clays rest on a slab of limestone with iron-rich stromatolitic ovoids that coincide with sedimentation resumption and fed by the arrival of an abundant clay-sandstone material. It is composed of a rhythmic alternation of clays and sandstone rich in sedimentary figures and structures. The monotony is sometimes broken by calcareous beds intercalations and often fossiliferous (ammonites) considered as biostratigraphical benchmark levels of lower, middle and upper Callovian. In this area fine-grained sandstone with rhizocorallium level divides the formation into two members. Foraminifera collected in the marly levels are Nodosariidae-rich which are associated with other families such as Spirillinidae, Lituolidae, Epistominidae, Saccamminidae, Hormosinidae, Nebucularidae and Textulariidae. Their vertical distribution enabled us to highlight three micro-faunal (foraminifera) renewals.