Evaluating tracemaker recovery after the Cretaceous–Paleogene (K–Pg) boundary event: different biotic responses at the Caravaca section

Abstract

AbstractTrace fossils are an aid to characterize major extinction events, enriching evolutionary paleoecology research. Ichnological analysis at the Cretaceous–Paleogene (K–Pg) marine boundary interval, worldwide, points to a relatively minor disruption in the macrobenthic tracemaker community; that is, trace-fossil assemblages do not change significantly across the K–Pg boundary, showing relatively rapid recovery, locally in just a few years post-impact. To evaluate the incidence of this event and the rapid recovery of the tracemaker community afterwards, the evolution of planktic and benthic groups at the K–Pg boundary interval was analysed in the Caravaca section (Betic Cordillera) based on the integration of available data. In general terms, planktic foraminifera and calcareous nannoplankton dropped in abundance and diversity at the K–Pg boundary, whereas benthic foraminifera did not show significant extinction, but rather a sudden and dramatic decrease in diversity and reorganization. After the K–Pg boundary event, planktic communities exhibit a prolonged delay in recovery—mainly occurring above the dark boundary layer—with respect to benthic foraminifera. The K–Pg boundary event did not induce a severe crisis for the burrowing macroinfauna, as revealed by the similarity between pre- and post-event ichnotaxa, showing a comparatively rapid first colonization phase, less than 2 ky after the event. The record of Zoophycos and Chondrites at the base of the dark boundary layer evidences an opportunistic behaviour of tracemakers and a high independence from oxygen in pore waters and food in the sediment, allowing for the colonization of an overall unfavorable environment.