New conodont species and biostratigraphy of the Santa Rosita Formation (upper Furongian-Tremadocian) in the Tilcara Range, Cordillera Oriental of Jujuy, Argentina

ZEBALLO F.J., ALBANESI G.L.

GEOLOGICAL JOURNAL (CHICHESTER)

JOHN WILEY & SONS LTD

Año: 2012 vol. 48 p. 170 - 193

0072-1050

A new conodont collection from the Alfarcito area of the Tilcara Range, Cordillera Oriental of northwestern Argentina, has been studied. The Santa Rosita Formation exposed in this area consists of the Tilcara, Casa Colorada, Pico de Halcón, Alfarcito, Rupasca and Humacha members, which have a combined total thickness of ca. 1100 m. The sequence is composed of interbedded shales and sandstones, including calcarenites and coquinas, mostly appearing in the upper parts of the units. An abundant fauna of conodonts (ca. 11000 elements), associated with graptolites and trilobites, was recorded. The biostratigraphic analysis allows for the identification of the C. intermedius and C. lindstromi sensu lato zones at the base of the Alfarcito Member. The C. angulatus Zone spans the upper part of the latter unit, and the Paltodus deltifer Zone (Paltodus deltifer pristinus and P. deltifer deltifer subzones) is identified in the Rupasca and Humacha members. The new species Acanthodus raqueli, A. humachensis, Utahconus tortibasis, U. scandodiformis, U. purmamarcensis, Variabiloconus crassus, Kallidontus gondwanicus and Acodus primitivus are recorded from the two latter biozones and they are herein described. The genera Acanthodus and Variabiloconus are emended, and a new genus Tilcarodus is created to include T. humahuacensis (Albanesi and Aceñolaza). The diversity of forms and species frequency of conodonts from the Cordillera Oriental is typical of the Cold Domain from the Shallow-Sea Realm, but the presence of the genera Acanthodus and Utahconus suggests certain participation of taxa from the Tropical Domain in the regressive  sequences.