Nutrient spatial variation during intrabasinal upwelling at the Cenomanian–Turonian oceanic anoxic event in the westernmost Tethys: An ichnological and facies approach

Facies and ichnofabrics of two sections of the Cenomanian–Turonian boundary interval are correlated and compared to evaluate changes in palaeoceanographic conditions controlled by palaeogeography in the distal zone of the westernmost Tethys (southern Iberian continental palaeomargin). The oceanic anoxic event (OAE-2) was interrupted by short aerobic or dysaerobic sub-events with slight differences in facies and ichnofabrics. These sub-events display a tendency to expansion from the more distal section (Hedionda) towards the proximal one (El Chorro). The anoxia spread out from the open sea, probably from slope upwellings. Higher diversity and abundance of trace fossils in comparatively distal position during the pre- and post-event intervals can be caused by a higher abundance of food available for tracemakers. Shape of the correlation bands of the OAE-2 event suggests that the event started earlier by about a few tens of thousands years in the most distal areas than in proximal, slightly higher bottom settings.