Oyster-dominated macrobenthic associations in the Cenomanian of Djebel Bouarif (Aures Mountains, Northeastern Algeria)

In the Batna area of Algeria, the Cenomanian is represented by the Smail Marls Formation, a highly fossiliferous unit with a diverse benthic macrofauna (mainly of ostreid bivalves). A total of 1090 speci-mens belonging to 65 macrobenthic species were identified from 19 stratigraphic samples. The mac-rofaunal communities were quantitively analyzed using the hierarchical clustering (HC), nonmetric multidimensional scaling (NMDS), and permutational analysis of variance (PERMANOVA). Five distinct associations are recognized: 1) Costagyra olisiponensis, 2) Rhynchostreon suborbiculatum, 3) Aspidiscus cristatus, 4) Rhynchostreon suborbiculatum-Mecaster ameliae, and 5) Pycnodonte vesicularis. Data suggests that during the Cenomanian, the dominance of high-energy opportunistic oyster species within the soft marly sediments are related to their adaptive strategies. The changes noted in the community structure are attributed to sea-level fluctuations, rate of sedimentation and the prevailing hydrodynamics. Towards the uppermost Cenomanian and the CenomanianeTuronian boundary, the oysters become rare due to eustatic sea-level rise and this decline coincides with increasing predation intensity on oysters and the destruction of their shallower habitats.& COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

In the Batna area of Algeria, the Cenomanian is represented by the Smail Marls Formation, which contains a diverse benthic macrofauna. The mac-rofaunal communities were analyzed using several statistical methods and five distinct associations were recognized. The dominance of high-energy opportunistic oyster species within the soft marly sediments is related to their adaptive strategies, and changes in community structure are influenced by sea-level fluctuations and sedimentation rates.