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We present records of stable carbon and oxygen isotopes,CaCO3 content, and changes in calcareous nannofossil assemblages acrossan 81 m thick section of upper Paleocene–lower Eocene marine sedimentaryrocks now exposed along the Cicogna Stream in northeast Italy. The studiedstratigraphic section represents sediment accumulation in a bathyalhemipelagic setting from approximately 57.5 to 52.2 Ma, a multi-million-yeartime interval characterized by perturbations in the global carbon cycle andchanges 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, andincludes both a long-term drop in δ13C and multiple short-termcarbon isotope excursions (CIEs). This precise correlation of widelyseparated δ13C records in marine sequences results fromtemporal changes in the carbon composition of the exogenic carbon cycle.However, diagenesis has likely modified the δ13C record atCicogna, an interpretation supported by variations in bulk carbonate δ18O, which do not conform to expectations for a primary signal. Therecord of CaCO3 content reflects a combination of carbonate dilutionand dissolution, as also inferred at other sites. Our detailed documentationand statistical analysis of calcareous nannofossil assemblages show majordifferences before, during and after the Paleocene–Eocene Thermal Maximum.Other CIEs in our lower Paleogene section do not exhibit such a distinctivechange; instead, these events are sometimes characterized by variationsrestricted to a limited number of taxa and transient shifts in the relativeabundance of primary assemblage components. Both long-lasting andshort-lived modifications to calcareous nannofossil assemblagespreferentially affected nannoliths or holococcoliths such as Discoaster, Fasciculithus, Rhomboaster/Tribrachiatus, Sphenolithus andZygrhablithus, which underwent distinct variations in abundance as well as permanentevolutionary changes in terms of appearances and disappearances. Bycontrast, placoliths such as Coccolithus and Toweius, which represent the main component of theassemblages, were characterized by a gradual decline in abundance over time.Comparisons of detailed nannofossil assemblage records at the Cicognasection and at ODP Site 1262 support the idea that variations in therelative and absolute abundances, even some minor changes, were globallysynchronous. 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 additionalwork

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