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

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doi: 10.1016/j.marmicro.2012.02.006
Author(s): d'Haenens, Simon; Bornemann, André; Stassen, Peter; Speijer, Robert P.
Author Affiliation(s): Primary:
Katholieke Universiteit Leuven, Department of Earth and Environmental Sciences, Leuven, Belgium
Other:
Universität Leipzig, Germany
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, Vol.88-89, p.15-35. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Supplemental information/data is available in the online version of this article; includes appendix. 177 refs.; illus., incl. 2 plates, 4 tables, sketch map
Summary: Within the last decade, several early Eocene hyperthermals have been detected globally. These transient warming events have mainly been characterized geochemically--using stable isotopes, carbonate content measurements or XRF core scanning--yet detailed micropaleontological records are sparse, limiting our understanding of the driving forces behind hyperthermals and of the contemporaneous paleoceanography. Here, detailed geochemical and quantitative benthic foraminiferal records are presented from lower Eocene pelagic sediments of Deep Sea Drilling Project Site 401 (Bay of Biscay, northeast Atlantic). In calcareous nannofossil zone NP11, several clay-enriched levels correspond to negative δ13C and δ18O bulk-rock excursions with amplitudes of up to ∼0.75 ppm, suggesting that significant injections of 12C-enriched greenhouse gasses and small temperature rises took place. Coeval with several of these hyperthermal events, the benthic foraminiferal record reveals increased relative abundances of oligotrophic taxa (e.g. Nuttallides umbonifera) and a reduction in the abundance of buliminid species followed by an increase of opportunistic taxa (e.g. Globocassidulina subglobosa and Gyroidinoides spp.). These short-lived faunal perturbations are thought to be caused by reduced seasonality of productivity resulting in a decreased Corg flux to the seafloor. Moreover, the sedimentological record suggests that an enhanced influx of terrigenous material occurred during these events. Additionally, the most intense δ13C decline (here called level δ) gives rise to a small, yet pronounced long-term shift in the benthic foraminiferal composition at this site, possibly due to the reappraisal of upwelling and the intensification of bottom water currents. These observations imply that environmental changes during (smaller) hyperthermal events are also reflected in the composition of deep-sea benthic communities on both short (<100kyr) and longer time scales. We conclude that the faunal patterns of the hyperthermals observed at Site 401 strongly resemble those observed in other deep-sea early Paleogene hyperthermal deposits, suggesting that similar processes have driven them. Abstract Copyright (2012) Elsevier, B.V.
Year of Publication: 2012
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Atlantic Ocean; Bay of Biscay; Benthic taxa; Biostratigraphy; Biozones; C-13/C-12; Calcium carbonate; Carbon; Cenozoic; Cluster analysis; Correspondence analysis; DSDP Site 401; Deep Sea Drilling Project; Deep-sea environment; Eocene; Foraminifera; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 48; Lower Eocene; Marine environment; Microfossils; Nannofossils; North Atlantic; O-18/O-16; Oxygen; Paleo-oceanography; Paleoclimatology; Paleoecology; Paleoenvironment; Paleogene; Plantae; Protista; Quantitative analysis; SEM data; Stable isotopes; Statistical analysis; Taphonomy; Tertiary
Coordinates: N472538 N472540 W0084837 W0084838
Record ID: 2012056700
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands