Biodiversity and taphonomy of bivalve assemblages of the Pliocene of Algeria (Bas Chelif Basin)

Abstract

Similar to the Miocene, the Pliocene of the outcrops of Bas Chelif Basin delivered abundant and much diversified fossiliferous levels of malacofauna (bivalvia). The paleontological study of two typical Pliocene series, in the center (Sidi Brahim) and at the northwestern margin of the Bas Chelif Basin (Sassel Beach), permit the identification of 4 orders, 8 families, 15 genera, and 20 species among the bivalvia. The simultaneous study of autoecological and taphonomic features of the fauna contained in the Sidi Brahim geological section allowed distinguishing at once four fauna associations, in which each one characterizes a particular ecozone which is attributed to an environment: (1) the muddy deep environment association (Cristatopecten cristatum , Pelecyroa brochii , and Tellina donacina ); (2) the muddy instable and frankly deep environment association (Anadara diluvii, C. cristatum, P. brochii, and T. donacina); (3) the association of the infralittoral environments, rich in sandy supplies; and (4) the association of the upper infralittoral sandy environment and three shell assemblages-the "3D census assemblage," "3D multihabitat time-averaged assemblage," and "3D allochthon assemblage"-where their spatiotemporal enchainment allowed making obvious four phases of transgressive-regressive oscillation in the general transgressive tendency of Sidi Brahim section, during the lower and average Pliocene. With a reduced thickness, the Sassel Beach section is characterized, on one hand, by the setup of two fauna associations of the infralittoral sandy environments (Pecten benedictus and Ostrea lamellosa) and infralittoral muddy environments (Aequipecten opercularis , Aequipecten seniensis, and P. benedictus), and of other parts by the piling up of three types of assemblages (3D allochthonous assemblage, 3D census assemblage, and 3D multihabitat time-averaged assemblage), defining three phases, comparatively less pronounced of the transgressive cycle of the Pliocene.

First record of blister pearls in the oyster Hyotissa hyotis (Linné, 1758) from Pliocene deposits at Sidi Brahim, Lower Chelif Basin (north-west Algeria)

“…1, 2) which surround the north-eastern side of Lower Chelif Basin, about 1.5 km south of the city of Sidi Ali. This outcrop has been studied by many authors during many decades (Anderson, 1936;Atif et al, 2008;Satour, 2012;Satour et al, 2013;Bendella et al, 2021;Benyoucef et al, 2021). The Neogene series is complete in the Lower Chelif Basin and ranges from the Burdigalian to the Pliocene (Benyoucef et al, 2021).…”

Borers and epizoans on oyster shells from the upper Tortonian, Lower Chelif Basin, NW Algeria

“…The stratigraphic studies of Miocene deposits of the Lower Chelif Basin had been the purpose of several earlier authors (Neurdin-Trescarte, 1992;Mansour, 2004;Belekebir et al,2008;Belhadji et al, 2008;Atif et al, 2008;Saint-Martin, 2008;Satour et al, 2011Satour et al, , 2013Satour et al, , 2020Satour,2021). The upper Miocene deposits are more distinguished in the center of the basin and contain many discontinuities, allowing a large variety of facies (Perrodon, 1957).…”

New insights on the latest Messinian-to-Piacenzian stratigraphic series from the Dahra Massif (Lower Chelif Basin, Algeria): Lago Mare, reflooding and bio-events

“…The overlying grey marls are still of Zanclean age and are in turn overlain by Piacenzian alternating marls and sandstones. They are marked by bivalve shell concentrations (Rouchy et al, 2007;Belhadji et al, 2008;Mansouri et al, 2008;Atif et al, 2008;Satour et al, 2013Satour et al, , 2020Bendella et al, 2021;Satour, 2021;Osman et al, 2021;Benyoucef et al, 2021;Mansouri, 2021).…”