First documentation of the late Albian transgression in northwest Algeria: Bivalve stratigraphy and palaeobiogeography

Abstract

Fourteen bivalve species are recorded for the first time from new exposures of poorly known upper Albian marine rocks in northwest Algeria provided by construction works in the south of Tiaret city. The documentation of the Albian transgression in the study area is here presented in a comprehensive stratigraphical and palaeobiogeographical framework. The sections studied exposed the Mcharref Formation that is subdivided here into two members, based on differences in lithological features. Stratigraphical ranges of the bivalves identified and of the associated ammonite Mortoniceras pricei date the successions studied as late Albian. In addition, strata in the study area are interpreted to have been deposited in a shallow-marine carbonate ramp setting with two third-order depositional sequences, separated by irregular and diagnostic unconformity surface that coincides with the boundary between the two members. Based on correlations, this sequence boundary correlates well with the fifth global sequence boundary of Albian age. Furthermore, the wide distribution of the common genus Neithea in the study area plays an important role in tracing the palaeogeographical distribution of the faunal assemblage. Tethyan Albian bivalves of Algeria show strong affinities with those from the North and South Atlantic provinces, which may be due to the opening of the equatorial Atlantic gateway during that time.