Boletín de la Sociedad Geológica Mexicana Volumen 67, núm. 1, 2015, p. 45-57 http://dx.doi.org/10.18268/BSGM2015v67n1a4

Berriasian–early Valanginian calcareous shallow-water facies from the Arperos Basin: A proposal from the foraminiferal assemblage of the clasts of the Guanajuato Conglomerate, central Mexico

Lourdes Omaña^1,*, Raúl Miranda-Avilés², María Jesús Puy-Alquiza²

¹ Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510, México, D.F., México.
² Departamento de Minas, Metalurgia y Geología, Universidad de Guanajuato, Ex-Hacienda de San Javier, 36020, Guanajuato, Gto., México.

^* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The Eocene Guanajuato Conglomerate is composed of clasts derived from igneous and metasedimentary sources that can be related to the Upper Jurassic–Lower Cretaceous arc and back-arc assemblages of the El Paxtle and Arperos Basin. Limestone clasts contain a shallow-water platform fauna that includes bivalves, brachiopods, gastropods, echinoderms and foraminifers. Foraminiferal studies were carried out on these limestone clasts. The benthic foraminiferal association is composed of Pseudocyclammina lituus (Yokoyama, 1890); Everticyclammina virguliana (Koechlin, 1942); Montsalevia salevensis (Charollais, Brönnimann and Zaninetti, 1987); Neotrocholina valdensis (Reichel, 1955); Andersolina cherchiae (Arnaud-Vanneau, Boisseau and Darsac, 1988); Neotrocholina molesta (Gorbatchik, 1959); Pfenderina neocomiensis (Pfender, 1938); Nautiloculina bronnimanni Arnaud-Vanneau and Peybernès, 1978; Hechtina praeantiqua Bartenstein and Brand, 1949; Protopeneroplis cf. P. banatica Bucur, 1993; Istriloculina sp., Moesiloculina sp., Protomarsonella sp., Ammovertellina sp. and Glomospirasp.

The Tethysian foraminiferal assemblage observed in the limestone clasts indicate the age of the calcareous source as Berriasian–early Valanginian, which is the age of the deposition within the Arperos Basin.

The occurrence of these shallow-water limestone clasts suggests the existence of a shallow-water platform deposit located in the Arperos Basin. This is significant considering that all previous work focused on the deep-water sedimentary rocks (siliciclastic and calcareous). Thus, these clasts are a key to reconstructing the depositional history and architecture of this basin.

Keywords: Tethysian benthic foraminifera, Berriasian–early Valanginian, Guanajuato Conglomerate.