Abstract

HEREDIA, Susana. Biostratigraphy of Middle Darriwilian (Ordovician) conodonts from Argentina: Las Aguaditas Formation, Central Precordillera. Rev. mex. cienc. geol [online]. 2012, vol.29, n.1, pp. 76-86. ISSN 1026-8774.

Several P elements of Eoplacognathus were recovered from samples collected in Las Aguaditas Formation, Las Chacritas river section, San Juan Province, Argentina. These dark grainstones, packstones, and wackestones represent distal carbonate rampfacies. The key conodonts Eoplacognathus pseudoplanus (Viira) and Eoplacognathus suecicus Bergström, document the Eoplacognathus pseudoplanus and the E. suecicus Zones pointing out middle Darriwilian age for the conodont-bearing strata in Las Aguaditas Formation. The species E. suecicus is recorded here for first time in the Argentine Precordillera. An evaluation of the record of this middle Darriwilian conodont genus in the Precordillera is presented here. Finally, the use of the middle Darriwilian Baltic conodont chart is proposed for the Argentine Precordillera.

Keywords : Biostratigraphy; Eoplacognathus; Darriwilian; Argentine Precordillera.