Darriwilian conodont biostratigraphy from the Rio Francia section, Central Precordillera, Argentina: A new insight into the Darriwilian conodont biozones

Abstract

Darriwilian conodont data from the uppermost meters of the San Juan Formation in the Rio Francia section are documented. A detailed analysis of conodont biostratigraphy is conducted, recording early-middle Darriwilian interval zones based on first occurrence of the index species of genus Lenodus. Four conodont biozones were documented: Lenodus antivariabilis, L. variabilis, L. crassus and L. pseudoplanus. The overlapped range of the L. variabilis, L. crassus and L. pseudoplanus verified the lower part of L. pseudoplanus Zone for the first time in the Precordillera. The co-occurrence of the P. horridus middle form first and second stage with key species of the Lenodus support this record, providing an accurate regional correlation between several sections in the Central and Eastern Precordillera. Based on the conodont data presented herein, the early-middle Darriwilian conodont biozonation of the Precordillera can now be tied more robustly to global biostratigraphic frameworks.