Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

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dc.citation.firstpage883en_US
dc.citation.journalTitleClimates of the Pasten_US
dc.citation.lastpage909en_US
dc.citation.volumeNumber12en_US
dc.contributor.authorAgnini, Claudiaen_US
dc.contributor.authorSpofforth, David J.A.en_US
dc.contributor.authorDickens, Gerald R.en_US
dc.contributor.authorRio, Domenicoen_US
dc.contributor.authorPälike, Heikoen_US
dc.contributor.authorBackman, Janen_US
dc.contributor.authorMuttoni, Giovannien_US
dc.contributor.authorDallanave, Edoardoen_US
dc.date.accessioned2016-06-27T18:44:08Zen_US
dc.date.available2016-06-27T18:44:08Zen_US
dc.date.issued2016en_US
dc.description.abstractWe present records of stable carbon and oxygen isotopes, CaCO3 content, and changes in calcareous nannofossil assemblages across an 81 m thick section of upper Paleocene–lower Eocene marine sedimentary rocks now exposed along the Cicogna Stream in northeast Italy. The studied stratigraphic section represents sediment accumulation in a bathyal hemipelagic setting from approximately 57.5 to 52.2 Ma, a multi-million-year time interval characterized by perturbations in the global carbon cycle and changes in calcareous nannofossil assemblages. The bulk carbonate δ13C profile for the Cicogna section, once placed on a common timescale, resembles that at several other locations across the world, and includes both a long-term drop in δ13C and multiple short-term carbon isotope excursions (CIEs). This precise correlation of widely separated δ13C records in marine sequences results from temporal changes in the carbon composition of the exogenic carbon cycle. However, diagenesis has likely modified the δ13C record at Cicogna, an interpretation supported by variations in bulk carbonate δ18O, which do not conform to expectations for a primary signal. The record of CaCO3 content reflects a combination of carbonate dilution and dissolution, as also inferred at other sites. Our detailed documentation and statistical analysis of calcareous nannofossil assemblages show major differences before, during and after the Paleocene–Eocene Thermal Maximum. Other CIEs in our lower Paleogene section do not exhibit such a distinctive change; instead, these events are sometimes characterized by variations restricted to a limited number of taxa and transient shifts in the relative abundance of primary assemblage components. Both long-lasting and short-lived modifications to calcareous nannofossil assemblages preferentially affected nannoliths or holococcoliths such as Discoaster, Fasciculithus, Rhomboaster/Tribrachiatus, Sphenolithus and Zygrhablithus, which underwent distinct variations in abundance as well as permanent evolutionary changes in terms of appearances and disappearances. By contrast, placoliths such as Coccolithus and Toweius, which represent the main component of the assemblages, were characterized by a gradual decline in abundance over time. Comparisons of detailed nannofossil assemblage records at the Cicogna section and at ODP Site 1262 support the idea that variations in the relative and absolute abundances, even some minor changes, were globally synchronous. An obvious link is through climate forcing and carbon cycling, although the linkages between variations in calcareous nannoplankton, changes in δ13C records and oceanography will need additional work.en_US
dc.identifier.citationAgnini, Claudia, Spofforth, David J.A., Dickens, Gerald R., et al.. "Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)." <i>Climates of the Past,</i> 12, (2016) Copernicus Publications: 883-909. http://dx.doi.org/10.5194/cp-12-883-2016.en_US
dc.identifier.doihttp://dx.doi.org/10.5194/cp-12-883-2016en_US
dc.identifier.urihttps://hdl.handle.net/1911/90803en_US
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.rightsThis work is distributed under the Creative Commons Attribution 3.0 License.en_US
dc.rights.urihttps://creativecommons.org/licenses/by/3.0/us/en_US
dc.titleStable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)en_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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