Impact of bottom water currents on benthic foraminiferal assemblages in a cold-water coral environment: the Moira Mounds (NE Atlantic)

• Published in: Marine Micropaleontology
• Main Authors: Fentimen, Robin, Lim, Aaron, Rüggeberg, Andres, Wheeler, Andrew J., Rooij, David Van, Foubert, Anneleen
• Other Authors: Laboratoire de Planétologie et Géosciences - Angers (LPG-ANGERS), Laboratoire de Planétologie et Géosciences UMR_C 6112 (LPG), Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), University College Cork (UCC), Department of Geosciences, University of Fribourg, Fribourg, Switzerland, Universiteit Gent = Ghent University (UGENT), Université de Fribourg = University of Fribourg (UNIFR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: carbonate mounds; taphonomy; living vs. dead assemblages; reworked species; transport; carbonate mounds taphonomy living vs. dead assemblages reworked species transport; [SDE]Environmental Sciences; North East Atlantic
• Online Access: https://univ-angers.hal.science/hal-04330027; https://univ-angers.hal.science/hal-04330027/document; https://univ-angers.hal.science/hal-04330027/file/Manuscript%20-%20Fentimen%20et%20al.%20FINAL.pdf; https://doi.org/10.1016/j.marmicro.2019.101799

International audience Strong bottom currents play a key role in cold-water coral environments by shaping their morphology and providing the necessary food for the corals to thrive. This study investigates the differences between living and dead benthic foraminiferal assemblages in such environments, more precisely on the Moira Mounds (NE Atlantic). A specific focus is to understand the role of currents and their influence on the taphonomy of benthic foraminiferal assemblages. Here, we analyze high-resolution sediment grain size distributions coupled with benthic foraminiferal assemblage composition to assess how much deep-sea bottom currents affect benthic foraminiferal assemblages. We suggest that the dead benthic foraminiferal assemblage consists of a reworked glacial fauna associated with contemporary species. Reworked glacial species (Elphidium excavatum, Sigmoilopsis schlumbergeri) are the most abundant. Dominant species that are present almost exclusively in the living assemblage (Alabaminella weddellensis, Nonionella iridea, Trifarina spp.) are associated with high phytodetritus input, possibly as a response to the later phase of the North-east Atlantic spring bloom. Dead assemblages are further characterized by the scarcity of organic-walled agglutinated foraminifera in comparison to living assemblages. Sediment grain size distributions show that the downslope Moira Mounds consist of well-sorted fine sand, typical of contourite deposits in the area. Grain size distributions and the average Shannon diversity of living and dead foraminiferal assemblages indicate that the coral cover offers a sheltered environment, baffling eroded sediment and preventing post-mortem transport of dead foraminifera. We conclude that cold-water coral environments provide a valuable paleoenvironmental archive by trapping sediment in an otherwise non-depositional system.