Disconformity between the El Abra Formation underlying the “Temazcal unit” in Cerro Quemado locality, Temazcal, San Luis Potosí, Mexico: Biostratigraphy and microfacies analysis

Abstract

On the western part of the Valles–San Luis Potosí Platform located in Cerro Quemado near Temazcal, municipality of Armadillo de Los Infante, two sequences crop out. The lower one is the shallow-water El Abra Formation of the mid–upper Cenomanian, unconformably covered by a deep-water deposit of the upper Maastrichtian informally called here the “Temazcal unit.” The succession presents a nonconforming contact between these two sedimentary units, displaying a hiatus as the result of a time of non-deposition in the sedimentary record, showing a subaerial exposure with erosion yielding topographic relief. Based on the lithological changes from the underlying limestone toward the overlying silty limestone, as well as a detailed biostratigraphic study based on foraminiferal associations that provide an accurate dating, it has been possible to estimate the magnitude of the hiatus, which spans from the lower part of the Turonian, including the Coniacian, the Santonian, and possibly the lower part of the Maastrichtian.