Ichnoassemblages from the Wilcox Formation in the Burgos Basin, northeastern Mexico

An ichnological analysis of the Paleocene-Eocene Wilcox Formation at San José de la Laja and La Curva localities within the Burgos Basin in the northeastern Mexico, revealed 7 ichnogenera: Chondrites, Diplocraterion, Ophiomorpha, Palaeophycus, Planolites, Sinusichnus, and Skolithos. The trace fossils were grouped into different ichnoassemblages, including a detailed facies analysis. These results show their apparent association with the Skolithos and Cruziana Ichnofacies in the two studied localities. The integrative analysis of trace fossils and lithofacies made it possible to infer plausible depositional environments for registered periods of fair-weather conditions in both localities of the Burgos Basin, which represent ecosystems characterized by low diversity and abundance. In San José de La Laja, the environment varies from storm affected to tidal setting. In La Curva, lithofacies and ichnology are modulated by storm events in a transitional shoreface, coastal bar, and intertidal setting within a deltaic plain. Both localities indicate a shelf impacted by deltaic processes and storm events. Living conditions for most endobenthic organisms were harsh. These results support a long-term regression of the coastal zone during the Paleogene-Neogene and suggest a paleoenvironment similar to this in the south of Texas during the Paleogene