Abstract

EGUILUZ DE ANTUNANO, Samuel  and  CARRANZA-CASTANEDA, Óscar. Stratigraphic revision and age of the Mayrán Formation (Alloformation) in the Parras area, Coahuila, Mexico. Bol. Soc. Geol. Mex [online]. 2013, vol.65, n.2, pp.397-404. ISSN 1405-3322.

This paper discusses the stratigraphy of the Mayrán Formation, and intends to redefine it as an alloformation. The lower part of the alloformation consists of interbedded limestone and sandstone, and the upper succession is tufa and shaly limestone. Both sequences show internal unconformities caused by interruptions during their deposition. The Mayrán alloformation is undeformed and underlie the Upper Cretaceous Difunta Group in angular unconformity , whereas the upper contact is a parallel unconformity (paraconformity) with Holocene soils. The proposed Mayrán Alloformation stratotype is exposed south of the Palo Alto locality, with reference sections in the Cruz Verde and El Durazno plateaus, northeast of Parras de la Fuente, Coahuila state. Based on their stratigraphy, Equus molars, and isotopic ages, these lithostratigraphic units range in age from Pliocene to Pleistocene.

Keywords : Mayrán; alloformation; Pliocene; Pleistocene; tufa; Equus; Coahuila.