A high-resolution nonmarine record of an early Danian hyperthermal event, Boltysh crater, Ukraine

Carbon isotope and palynological analysis of the fine-grained organic carbon-rich lacustrine sediments that filled the Cretaceous-Paleogene (K-Pg) boundary-age Boltysh impact crater (Ukraine) preserve a uniquely complete and detailed record of a negative carbon isotope excursion in an expanded section of the early Danian that we estimate lasted as long as similar to 340 k.y. Palynological assemblages recovered through the excursion reflect the increasing dominance of thermophylic Normapolles species, indicating an increasingly warm and dry climate, while those recovered below and above the excursion reflect a cooler and wetter climate. The record of a transient warming event (hyperthermal) in the early Danian at Boltysh has strong similarities with the Dan-C2 hyperthermal event recorded in marine sediments in Tethys and the Atlantic Ocean, and suggests that there were profound environmental changes occurring on a global scale shortly after the K-Pg boundary.