Ichnology of the Paleocene-Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM) is among the most extensively studied climatic events in Earth’s history, primarily due to its relevance as an analogue for future climate change. This brief interval (<200kyr) is marked by a pronounced global temperature increase of approximately 4–8°C and widespread environmental disruptions, including ocean acidification, sea-level rise, intensification of the hydrological cycle, ice-sheet retreat, and significant species extinctions. Despite its importance, ichnological analyses—an essential tool for paleoenvironmental interpretation—remain relatively scarce compared to other Earth science studies.

To address this gap, we performed an ichnological analysis across several sections of the Iberian Peninsula: four sites within the Pyrenean Basin (Esplugafreda, Serraduy, Campo, and Zumaia), representing a continental-to-marine transect in a deep-water gulf opening toward the Bay of Biscay, and one deep-sea section along the southern margin of the Iberian Massif, connected to the Tethys Sea (Río Gor). In the south-pyrenean foreland, conforming an elongated restricted basin, the onset of the PETM coincided with the extinction of the tracemaker community. After that, on the platform areas, trace fossil assemblages were re-established prior to the recovery of the carbon isotope excursion, whereas in deep-sea settings, assemblages only partially recovered even after the excursion ended. These findings indicate a prolonged tracemaker recovery period during the PETM, suggesting that deep-sea tracemaker communities experienced extended ecological stress. In the southern margin of the Iberian Massif (i.e., open ocean setting), during the PETM a high trace fossil abundance is recorded.

Finally, by comparing our results with those from other parts of the world (previous published studies and ongoing research), we can hypothesize why the PETM did not cause a global extinction in the macrobenthic tracer community.