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

Resumen

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 Glomospira sp. 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.