The Upper Paleocene of the Zumaya Section (Northern Spain): Review of the Ichnological Content and Preliminary Palaeoecological Interpretation

Abstract

The upper Paleocene, deep-marine succession from Itzurun beach (Zumaya, Northern Spain) has been studied using a bed-by-bed analysis. Seventeen ichnogenera were recognized and grouped into eight ichnoassemblages. Most of the ichnotaxa and ichnoassemblages are closely related to a particular lithology. Of the trace fossils, only Chondrites and Palaeophycus tubularis are lithology-crossing ichnotaxa. Among the ichnoassemblages, only the Palaeophycus tubularis and the Chondrites ones were recorded in a variety of lithologies. In hemipelagic limestones and marly limestones, Zoohycos insignis, Zoophycos brianteus and Palaeophycus tubularis ichnoassemblages have been described. The two Zoophycos ichnoassemblages were produced under relatively firmground conditions. The particular type of Zoophycos morphology present, can be interpreted in terms of either discontinuous or more continuous input of benthic food to the environment. Palaeophycus tubularis ichnoassemblages developed in softer to slightly firm, well-oxygenated substrates rich in benthic food. The Planolites bevelreyensis ichnoassemblage is related to event beds and a clear sequential colonization can be recognized. The ?Palaeophycus tubularis ichnoassemblage represents the colonization of the fine-grained, organic matter-rich tail of turbiditic events. Siliciclastic turbidites show little evidence of bioturbation. It is represented by Planolites beverleyensis ichnoassemblage, Helmithopsis, and Ophiomorpha annulata ichnoassemblages, the latter two only rarely observed.

Keywords:

• Trace fossils
• ichnoassemblage
• Palaeoecology
• deep-marine
• Paleocene
• North Spain

ACKNOWLEDGMENTS

The research project and the field work were financed by the Von Humboldt Foundation. The authors would like to thank Victoriano Pujalte and Juan Ignacio Baceta of the University of Bilbao for their support and useful discussions on the outcrops; Asier Hilario, director of the Algorri Interpretation Center (Zumaya), for assistance in the field work; and Dr. Nicola Falocci (Servizio Studi del Consiglio Regionale Umbria, Italy) for the mathematical elaboration of the data set. The authors would like to thanks also Francisco Rodriguez Tovar and Andreas Wetzel, who provided numerous comments useful to improve the manuscript.