High-resolution conodont biostratigraphy from the Darriwilian Stage (Middle Ordovician) of the Argentine Precordillera and biodiversity analyses: a CONOP9 approach

N. A. FELTES; F. SERRA; D. GOLDMAN; G. L. ALBANESI

LETHAIA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 52 p. 188 - 203

0024-1164

Ordovician conodonts have been extensively documented in the Argentine Precordillera,providing a robust database for a diverse set of palaeontological studies. Despitethe numerous studies, the published taxonomy and stratigraphical ranges, data remaincontradictory for particular time intervals. Data from a new conodont collection fromthe Gualcamayo Formation exposed at the Cerro La Chilca section, and new informationon the occurrence and ranges of species from the Las Chacritas and Las Aguaditassections are presented herein. We used a computer-assisted numerical sequencing program(CONOP9) to construct a composite stratigraphical range chart from data of 57conodont species in four sections from the Argentine Precordillera. The identifiedzones of Lenodus variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanusand Eoplacognathus suecicus allowed us to verify and adjust the biostratigraphicalscheme for the Darriwilian of the Central Precordillera. Additionally, species of thegenera Histiodella, namely Histiodella sinuosa, Histiodella holodentata, Histiodellakristinae and Histiodella bellburnenisis, enable a reasonable correlation between theHistiodella-based zonation and the Baltoscandian zonation. Conodont diversity isevaluated using conventional measures (total diversity and normalized diversity) andan interval-free approach with CONOP9 software. Our data show a positive pattern inconodont diversification, increasing rapidly through the L. variabilis to the Y. crassuszones and reaching a peak in the E. pseudoplanus Zone. When analysing diversity fluctuationswith respect to the environmental changes within the depositional basin,migrations in and out of the basin related to local sea level fluctuations appear to bean important process driving the conodont diversity pattern in thePrecordillera.