Impact of the Paleocene–Eocene Thermal Maximum on the macrobenthic community: Ichnological record from the Zumaia section, northern Spain

Trace fossil assemblages from the latest Paleocene to the earliest Eocene were significantly affected by the environmental perturbation of the Paleocene–Eocene Thermal Maximum (PETM). High-resolution ichnological analysis shows well marked different ichnological features pre-, syn-, and post-event. A well developed normal, tiered burrowing community is present in the sediments below the PETM, indicating oxic conditions and normal benthic food availability. During the PETM the record of trace fossil producers disappeared gradually but rapidly, reflecting the global increase in temperature, and the concentration of benthic food in the very shallow surface layer and, probably, the local depletion of oxygen within the sediments, although probably not true anoxia. The environmental perturbation significantly affected the whole benthic habitat, as shown by the correspondence with the main phase of the benthic foraminiferal extinction. After the PETM, the normal, tiered burrowing community recovered gradually and slowly, in a delayed return to pre-PETM environmental conditions. The changes in the trace fossil assemblage thus document the impact of the PETM on the macrobenthic community, a decline in oxygen levels during the PETM in a globally perturbed habitat due to global warming and the similarities and differences in the response of micro- and macrobenthic communities to global phenomena. Thus, ichnological analysis reveals as a very useful additional tool to understanding atmosphere–ocean dynamic during PETM and a potential way in future climate research.