Application of Ichnofossils and Microfossils in the Paleoenvironmental Reconstruction of Turbidite Sequences from the Chicontepec Basin, Central-Eastern Mexico

The Chicontepec Basin is located in the states of Veracruz, Hidalgo, and Puebla, in the central and eastern region of Mexico. The basin was formed during the Paleocene-Eocene, due to the orogenic process associated with the Sierra Madre Occidental (SMO) formation, and by lithospheric flexure with the consequent subsidence that allowed the development of a foreland-type sedimentary basin. The basin was filled with a more than 2000-m-thick layer of turbidite terrigenous sediments derived from the SMO (from the west), and from the Tuxpan paleo-platform (from the east), lying discordantly on Jurassic-Cretaceous rocks. Sedimentological, micropaleontological, and ichnological observations of the Chicontepec Formation indicate low-energy deposition influenced by turbidites. The deep-water marine environment is indicated by the dominance of planktonic foraminifera deposited in a parautochthonous assemblage. The ichnotaxa association from Chicontepec is characteristic of the Zoophycos and Nereites Ichnofacies, supporting the idea that it was a deep-water deposit, because these ichnofacies usually develop in the bathyal zone, where turbidites appear, while the development of ichnofossils requires quiet and stable conditions. This is mainly indicated by the conspicuous presence of Paleodictyon ichnogenus, which is considered as typical ichnofossil of flysch deposits. The post-turbidite association is represented by the trace fossil, composed mainly by feeding burrows represented by Cruziana isp., Cosmorhaphe sinuosa, Halopoa imbricata, Helicolithus sampelayoi, Helminthorhaphe crassa, H. japonica, Lorenzinia apenninica, Megagrapton irregulare, Paleodictyon minimum, P. strozzii, Paleomeandron cf. robustum, Scolicia prisca, Scolicia isp., Spirorhaphe azteca, Spongeliomorpha oraviense, Thalassinoides isp., Urohelminthoida appendiculata, and Zoophycos isp.