Upper Cretaceous microfauna of the Cárdenas Formation, San Luis Potosí, NE Mexico. Biostratigraphical, palaeoecological, and palaeogeographical significance

The study of the microfauna of the lower member of the Cardenas Formation occurring in the Cardenas Basin (San Luis Potosi, NE Mexico) has been carried out at the type-locality of Lepidorbitoides minima Doville. A re-examination of the larger foraminifera sampled in this locality, in addition to the study of the associated planktonic foraminifera and ostracodes, suggest a deposition in an open marine environment with terrigenous input during the middle-upper Campanian (Globotruncana ventricosa Zone and/or calcarata Zones). These preliminary results might be useful to precise the geological setting of the Cardenas Formation. Moreover, the comparison of the studied microfauna with other Upper Cretaceous Tethyan ones have led to establish its strong similarities with the microfauna found in the Caribbean realm and the U.S. Gulf Coastal Plain but its tenuous European affinities.