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

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doi: 10.5194/cp-12-883-2016
Author(s): Agnini, Claudia; Spofforth, David J. A.; Dickens, Gerald R.; Rio, Domenico; Palike, Heiko; Backman, Jan; Muttoni, Giovanni; Dallanave, Edoardo
Author Affiliation(s): Primary:
Universita di Padova, Dipartimento di Geoscienze, Padua, Italy
Other:
Compagnie Générale de Géophysique, United Kingdom
Rice University, United States
Stockholm University, Sweden
University of Bremen, Germany
Universita Statale di Milano, Italy
Ludwig-Maximilians Universität München, Germany
Volume Title: Climate of the Past
Source: Climate of the Past, 12(4), p.883-909. Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1814-9324
Note: In English. 169 refs.; illus., incl. strat. cols., 1 plate, 1 table, geol. sketch map
Summary: We 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.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Atlantic Ocean; Belluno Italy; Biologic evolution; Biozones; Blake Nose; Blake Plateau; C-13/C-12; Calcium carbonate; Carbon; Carbon cycle; Cenozoic; Cicogna Stream; Climate forcing; Correlation; DSDP Site 577; Deep Sea Drilling Project; Diagenesis; Eocene; Europe; Geochemical cycle; Geochemistry; IPOD; Isotope ratios; Isotopes; Italy; Leg 171B; Leg 199; Leg 208; Leg 86; Lower Eocene; Lower Paleogene; Marine environment; Microfossils; Nannofossils; Nannoplankton; North Atlantic; North Pacific; Northwest Pacific; O-18/O-16; ODP Site 1051; ODP Site 1215; ODP Site 1262; Occurrence; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleocene; Paleocene-Eocene Thermal Maximum; Paleogene; Plankton; Plantae; Sedimentary rocks; Shatsky Rise; South Atlantic; Southern Europe; Species diversity; Stable isotopes; Statistical analysis; Stratigraphy; Tertiary; Upper Paleocene; Veneto Italy; Walvis Ridge; West Pacific
Coordinates: S271100 S271100 E0013500 E0013400
N322628 N322632 E1574324 E1574323
N460700 N460700 E0121126 E0121126
Record ID: 2017017646
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany