Microfossils of the Yangtzeplacognathus crassus zone in the middle darriwilian of the argentine precordillera

Abstract

The San Juan Formation of the Eastern and Central Precordillera is composed mainly of fossiliferous limestone and marly limestone. The conodont biostratigraphy of the very top of this unit has been studied on several localities such as: Don Braulio, La Pola, Cecilia and Del Aluvión creeks, recording the Y. crassus Zone for this levels (Mestre, 2010; Mestre, 2013, Heredia and Mestre, 2013). The microfossils associated to this conodont biozone are represented by spicules, foraminifers and protoconchs, which are reported and figured in this work.