A high-resolution record of environmental changes from a Cretaceous-Paleogene section of Seymour Island, Antarctica

A high-resolution sedimentological and palynological study was performed in combination with biomarker-based organic geochemical temperature proxies TEX86 and MBT'/CBT, on a 7.4-m-thick continuous section straddling the Cretaceous-Paleogene (K-Pg) boundary at Seymour Island, at the northern tip of the Antarctic Peninsula. The K-Pg interval of the Seymour Island section was deposited in a deltaic/estuarine system with considerable sedimentary input from the erosion of a distant volcanic arc at the Antarctic Peninsula, combined with ash fallouts from explosive volcanic eruptions. The Maastrichtian interval represents the prodelta of a delta prograding in a marginal marine setting, whereas the Paleocene interval was deposited in more open, shallow marine conditions, following sea-level rise and shoal submergence above the K-Pg boundary. Dinocyst biostratigraphy indicates that in the studied section the K-Pg boundary is represented by a gentle erosive surface, 30 cm below a partially-indurated, marker sandstone bed. The dinoflagellate assemblages show quantitative changes across the boundary. Representatives of Manumiella group together with abundant Palambages dominate the assemblages in the lower part of the section, i. e. below the K-Pg boundary. There is an evident peak of Fibrocysta/Ifecysta/Cordosphaeridium just above the boundary. In the upper part of the section, Senegalinium reaches relatively high abundance together with Impletosphaeridium clavus. While relatively high concentrations of soil-derived organic matter inhibit the use of the TEX86 paleothermometer to reconstruct sea surface temperatures, the MBT'/CBT paleothermometer indicates warm mean annual air temperatures for the latest Cretaceous (16.0-16.5 degrees C). These high temperatures, coinciding with the lowest abundance of the high-latitude pollen taxon Nothofagidites, may reflect the terminal Cretaceous Deccan Traps-warming pulse. Fluctuating temperatures followed in the early Paleocene, characterized by similar to 2 degrees drop in air temperatures, coincident with the maximum percentage of the high-latitude angiosperm Nothofagidites spp. and the cold-water dinocyst taxon Impletosphaeridium clavus. The recognition of ecological signals of disturbances and their relationship with short-term climatic and environmental changes, provides new insights related to the effect of the impact at the high-latitude K-Pg boundary of Antarctica.