A new high-resolution carbon-isotope stratigraphy for the Campanian (Bottaccione section): Its implications for global correlation, ocean circulation, and astrochronology

Abstract

A high-resolution carbon isotope record is presented for Campanian strata of the Bottaccione section (Umbria-Marche Basin), through an interval that constitutes the standard reference section for the geomagnetic polarity time scale. The identification of prominent δ13C excursions and high frequency variations allows the establishment of robust stratigraphic markers to link this new Tethyan δ13C record with the Boreal realm (Lägerdorf-Kronsmoor section, Northwest Germany and the Trunch borehole, Norfolk, UK). A decoupling of baseline δ13C values between the Boreal and the Tethyan realm is observed during the mid-Campanian, reflecting a plausible change in intermediate/deep-water mass exchange due to a more restricted Tethyan gateway; this is hypothesized to be a consequence of northward movements of Africa associated with opening of the South Atlantic Ocean. Statistical evaluation of a segment of the δ13C dataset with the TimeOpt method for astrochronologic testing provides strong evidence of astronomical forcing, and underscores the potential for development of a complete astronomically tuned Campanian Stage at Bottaccione, allowing astronomical calibration of key geomagnetic and paleobiologic datums.