Magneto-biostratigraphy of the Cicogna section (Italy): implications for the late Paleocene-early Eocene time scale.

We present the magnetostratigraphy and calcareous nannofossil biostratigraphy of the ~81 m thick upper Paleocene–lower Eocene Cicogna section from the Belluno Basin of NE Italy. The Cicogna section extends in stratigraphic continuity from Chron C25r to Chron C23r and from nannofossil Zone NP7/NP8 to NP12 (=CP6–CP10), thus covering an interval of time comprised between ~56.6 and ~52.2 Ma. Inferred sediment accumulation rates were relatively constant in the order of ~18 m/Myr, and were used to estimate the age of standard calcareous nannofossil events for comparison with, and improvements of, current time scales. We found several new and potentially useful biohorizons that help refining the chronology of this critical interval of time encompassing a long and biochronologically poorly known Chron C24r. We furthermore observed an apparent correlation between rock-magnetic properties of the sediments and global climate variability as revealed by a reference benthic δ18O record from the literature, whereby higher relative amounts of oxidized magnetic phases such as hematite and/or maghemite seem to correlate to extreme warm periods like the PETM at ~55 Ma and the early Eocene from ~54 to ~52.5 Ma. Mechanisms able to explain this apparent coupling between rock-magnetic variability and long-term global climate are presently under scrutiny.