An expanded Tethyan Kimmeridgian magneto-biostratigraphy from the S'Adde section (Sardinia) : implications for the Jurassic timescale

The Kimmeridgian (Late Jurassic) stage has proven difficult to define in modern timescales essentially because the land sections used to describe it are typically condensed and discontinuous. For example, no single land section has been able to replicate the full record of magnetic polarity reversals recorded on the ocean floor as marine magnetic anomalies. Here, we report the magnetostratigraphy of the S'Adde carbonate succession from the Tethyan realm of Sardinia (Italy) that was previously studied for nannofossil biostratigraphy. We applied a statistical approach to correlate this magneto-biostratigraphic record to a recent global stack of M-sequence magnetic anomalies. We found that the base of the Tethyan Kimmeridgian, as approximated by the first occurrence (FO) of nannofossil Faviconus multicolumnatus, falls within M25Ar1n at a nominal age of ~152.8 Ma, while the base of the Tethyan Tithonian (top Kimmeridgian) as approximated by the FO of Conusphaera mexicana minor falls in the lower part of M22n at a nominal age of ~146.5 Ma. A discussion of the relationship between our Tethyan Kimmeridgian and the Sub-Boreal Kimmeridgian as defined in the Flodigarry GSSP candidate section is also provided. By virtue of its continuity, the S'Adde section is a valuable reference section for defining the Tethyan Kimmeridgian in modern Jurassic timescales.