Sub-orbitally paced cycles from the lowermost Danian Elles section (Tunisia): implications for the timing of climate evolution after the Cretaceous/Paleogene boundary impact

The Cretaceous-Paleogene (K-Pg) boundary, ca. 66 million years ago, marks the one of the largest mass extinction events ever. It is widely appreciated that the K-Pg extinction event was mainly caused by the impact of a large extraterrestrial body, known as the Chicxulub asteroid impact. The impact led to dramatic global environmental changes. In addition to the dust in the vapor-rich plume of ejecta the impact produced several climatically active gas components, including aerosol-producing sulfur oxides, greenhouse-warming CO2 and H2O, and ozone-depleting Cl and Br. The possible primary and secondary global climatic and environmental effects include a short-term global cooling phase, the so-called impact “winter” sustained by impact generated S-bearing gases followed by CO2 greenhouse warming. Besides modelling, the acquisition of temporally well resolved proxy records form expanded and continuous sedimentary archives can provide insights into the direct and indirect effects of the K/Pg impact in the aftermath of the event. The identification of orbital (Milankovitch band) and suborbital periodicities is a fundamental pre-requisite to build a sufficiently resolved time framework for the succession of proxy-based reconstruction in such sedimentary successions.  To develop a high-resolution chronology of the post-K/Pg interval, we analyzed a 0.9 cm-resolved record of grain-size straddling the lowermost Danian at the expanded Elles section (Tunisia). Spectral analysis of this record allowed us to recognize sub-orbital periodicity that provides a fine scale chronology of the evolutionary and environmental events in the aftermath of the impact.