Multiple early Eocene benthic foraminiferal assemblage and δ13C fluctuations at DSDP Site 401 (Bay of Biscay — NE Atlantic)

摘要: Abstract Within the last decade, several early Eocene hyperthermals have been detected globally. These transient warming events mainly characterized geochemically – using stable isotopes, carbonate content measurements or XRF core scanning yet detailed micropaleontological records are sparse, limiting our understanding of driving forces behind and contemporaneous paleoceanography. Here, geochemical quantitative benthic foraminiferal presented from lower pelagic sediments Deep Sea Drilling Project Site 401 (Bay Biscay, northeast Atlantic). In calcareous nannofossil zone NP11, clay-enriched levels correspond to negative δ13C δ18O bulk-rock excursions with amplitudes up ~ 0.75‰, suggesting that significant injections 12C-enriched greenhouse gasses small temperature rises took place. Coeval these hyperthermal events, record reveals increased relative abundances oligotrophic taxa (e.g. Nuttallides umbonifera) a reduction in abundance buliminid species followed by an increase opportunistic Globocassidulina subglobosa Gyroidinoides spp.). short-lived faunal perturbations thought be caused reduced seasonality productivity resulting decreased Corg flux seafloor. Moreover, sedimentological suggests enhanced influx terrigenous material occurred during events. Additionally, most intense decline (here called level δ) gives rise small, pronounced long-term shift composition at this site, possibly due reappraisal upwelling intensification bottom water currents. observations imply environmental changes (smaller) also reflected deep-sea communities on both short (