Ichnological analysis of the Cretaceous–Palaeogene boundary interval at the Caravaca section, SE Spain

Ichnological analysis of the Cretaceous–Palaeogene (K–Pg) boundary at Caravaca (Betic Cordillera, southeast Spain) reveals significant data for the interpretation of the K–Pg boundary event. The uppermost Maastrichtian marls below the Cretaceous–Palaeogene (K–Pg) boundary at Caravaca contains the dark-coloured trace fossils Chondrites targionii, Planolites, Thalassinoides, Zoophycos, and Alcyonidiopsis. The composition of trace fossil associations in the upper Maastrichtian and lower Danian marls is generally the same, yet much more poorly preserved in the latter, showing, in general, no ichnological evidence of a severe macroinfaunal crisis at the K–Pg boundary. The dark-coloured trace fossils penetrate from two bioturbated horizons in the dark boundary layer, separated by two horizons with primary lamination. The ichnofauna rapidly recovered after the K–Pg event following deposition of the lower, parallel-laminated bed, 14 mm thick, that occurs in the dark boundary layer above the K–Pg boundary. Zoophycos is the deepest trace fossil, penetrating as far as 90 cm below the K–Pg boundary, probably in stiff or partly firm substrate, which was dewatered to some extent during the slow accumulation of the Danian dark boundary layer. The firmness probably prevented the Chondrites trace maker from deeper burrowing. The Maastrichtian sediments may be contaminated with Danian microfossils due to bioturbation.