The middle Cretaceous Tamabra Formation in the central portion of the Valles-San Luis Potosi Platform western margin, central-northeastern Mexico

Abstract

At the western margin area of the Valles-San Luis Potosí Platform (PVSLP), adjacent to the Central Mexico Mesozoic Basin (CMCM), a series of sedimentary sequences, characteristic of a transitional area (slope) was deposited during middle Cretaceous. The sequences are comparable in age and genesis with the rocks of the Tamabra Formation of the eastern margin of the PVSLP. Lithological-facial studies of the Tamabra Formation in the central part of the western margin of the PVSLP, between the San Luis Potosí and Villa de Arista cities in San Luis Potosí state, allowed to identify that the Tamabra Formation in this region is composed by autochthonous sequences of mud- stone and wackestone with pelagic fauna characteristic of deep-water environments that are inter- layered with allochthonous gravity-induced and suspension sediments composed by packstone and grainstone to rudstone with a high content of shallow-water bioclasts and lithoclasts. In the alloch- thonous sequences dominate the debris flows, then the calcareous turbidites associated sporadically with synsedimentary folding due to slumping and sliding. The stratigraphic sequences suggest the development of an abrupt margin between the PVSLP and the CMCM probably of the by-pass type, as a consequence of a high sedimentation rate in the platform margin.