El Cenomaniense-Turoniense de Tamajón (Guadalajara, España): contexto geológico, contenido fósil e interpretación paleoambiental

Abstract

La sección del Cenomaniense-Turoniense de Tamajón, con un alto valor científico, educativo y divulgativo, incluye las formaciones Utrillas, Villa de Vés y Picofrentes, y la parte inferior de la Formación Ciudad Encantada. Contiene huellas de vertebrados (cocodrilomorfos, un posible dinosaurio terópodo y peces), otros icnofósiles (principalmente Thalassinoides), plantas vasculares, una considerable diversidad de invertebrados, incluyendo corales, briozoos, braquiópodos, bivalvos, gasterópodos, cefalópodos, equinodermos (equinoideos) y crustáceos decápodos, y algunos restos de peces y reptiles marinos, entre otros fósiles. El conjunto de la sección registra una transgresión marina y el inicio de una regresión, incluyendo el paso de un medio continental y de transición, a un entorno claramente marino con abundantes invertebrados, que finalmente fue afectado por un descenso eustático.

The Cenomanian-Turonian section (Upper Cretaceous) of Tamajón (Guadalajara, Spain) combines high scientific, educational and outreach values. Their materials unconformably lie onto Triassic deposits in Buntsandstein facies, being included into the Utrillas, Villa de Vés and Picofrentes formations, and the lower part of the Ciudad Encantada Formation. The section contains beds showing several tracks (occasionally trackways) of numerous crocodyliforms, a possible theropod dinosaur and some fishes, and different ichnofossils (mainly bioturbations Thalassinoides) usually caused by invertebrates. It also yields some fragments of trunks and branches of vascular plants, a high diversity of invertebrates, including scleractinian corals, bryozoans, brachiopods, bivalves (a high variety, including ostreids and rudists), gastropods, cephalopods (mainly ammonoids), echinoderms (echinoids), and decapod crustaceans, together with osteichtian and chondrichthyan fishes, and marine reptiles, among many other remains. The whole section records a marked marine transgression and the beginning of a regression, showing the change from a terrestrial and transitional setting, with vascular plants and crocodyliforms (Utrillas and Villa de Vés formations), to a fully marine environment, extraordinary rich in molluscs and other invertebrates (Picofrentes Formation), which finally was affected by a notable eustatic fall (lower part of Ciudad Encantada Formation).