First conodonts record in the Argentine Puna related to Middle Ordovician graptolites

TORO, BLANCA A.; HEREDIA, S.; HERRERA SÁNCHEZ, NEXXYS C.; MORENO, FLORENCIA; LO VALVO, GERARDO A.

Puerto Madryn

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2019

Asociación Paleontológica Argentina

Newly biostratigraphic research conducted in the Huaytiquina section (Salta province), allowed to obtain the first record of Middle Ordovician conodonts for the western Argentine Puna. The analyzed material comes from calcareous sandstones levels intercalated in the lower portion of the turbiditic succession corresponding to the Coquena Formation. The recovered conodont fauna is composed by species of the genera Baltoniodus, Gothodus, Trapezognathus, Drepanoistodus, Drepanodus, few elements of Microzarkodina and Protopanderodus ,among others. Although the conodont elements are very abundant, the diversity is very low, being the Gothodus elements the most numerous in each sample. The conodont associations indicate a Dapingian (Middle Ordovician) age, linking the conodonts of the Argentine Puna with those from Baltoscandinavia. The productive levels also contain graptolites of the Tetragraptus genus, and are closely related to strata bearing Azygograptus lapworthi Nicholson and Xiphograptus lofuensis (Lee) which are confirming the Dapingian age of the lower and middle portions of the Coquena Formation. The occurrence of Azygograptus lapworthi was also recently recorded in the Argentine Cordillera Oriental related to the index conodont Baltoniodus triangularis (Lindström). The new findings, suggest that a high-resolution correlation between both geomorphological regions could be possible, and they also certifying that both sectors of the Central Andean Basin were connecting during the interval corresponding from the Lower Ordovician (Floian) to the Middle Ordovician (Dapingian). Future taxonomic studies of larger conodont collections and graptolites key taxa will make it possible to accurate the age of the Coquena Formation, improving its regional and global correlations.