Paleoenvironmental Stasis for the Bioturbating Community During the Paleocene-Eocene Thermal Maximum at the Southern Iberian Margin.

During the Paleocene-Eocene Thermal Maximum (PETM), there was an increase in global temperatures and emissions of isotopically depleted carbon, resulting in a negative carbon isotope excursion (CIE). This climatic event caused a widespread ocean deoxygenation, leading to substantial biotic turnover. Previous ichnological studies of deep-sea environments have suggested that bioturbating communities perished or diminished considerably during this event. In this study, we present an ichnological analysis of a well-known deep-sea outcrop (Rio Gor section; lower bathyal-upper abyssal depth; 1000-2000 m) from the southern Iberian margin. Contrary to previous studies, at this location, the PETM onset did not result in the extinction of the bioturbating community. In fact, high abundances of trace fossils were recorded during the PETM, indicating favorable paleoenvironmental conditions for the community. We discuss how sedimentary and climatic dynamics played a key role in regulating trace fossil abundance throughout the PETM. The paleogeographical position and deep-water circulation of the area appear to have played a crucial role in preventing low-oxygen deep water masses and the impoverishment of the bioturbating community. Overall, our findings reveal the PETM's positive impact on the bioturbating community at the southern Iberian margin. Given the essential ecological functions of these organisms on the seafloor-such as nutrient recycling and sediment mixing-we emphasize their potential importance in future warmer ocean scenarios.