Cryptospore assemblages from the Ordovician/Silurian boundary in the Puna, North-West Argentina

RUBINSTEIN, C. V; VACCARI, N.E.

PALAEONTOLOGY

The Palaeontological Association - Blackwell Publishing

Lugar: London; Año: 2004 vol. 47 p. 1037 - 1061

0031-0239

Palynomorph assemblages have been recovered from deposits believed to straddle the Ordovician/Silurian boundary, from the upper member of the Salar del Rincón Formation, in the Puna region of north-west Argentina. The palynomorph assemblages are dominated by terrestrial cryptospores, but also contain marine microbiota (acritarchs, prasinophycean algae and chitinozoans). The cryptospore assemblages are similar in composition to those described from coeval deposits worldwide, suggesting that the producers were cosmopolitan and tolerated a wide range of climatic conditions. The cryptospore assemblages are correlated with the Imperfectotriletes spp. Interval Biozone (sub-biozone a) of the Imperfectotriletes spp.-Laevolancis divellomedia Assemblage Biozone, indicating a Hirnantian (latest Ordovician)  age. Acritarchs include late Ordovician species such as Eupoikilosusa striata and Villosacapsula cf. setosapellicula, that coexist with the Llandovery species Dactylofusa estillis. Based on lithological and palynological evidence, an early Llandovery, or a late Hirnantian (post-glacial) age is proposed for the basal part of the upper member of the Salar del Rincón Formation.