CAMBRIAN CONODONTS AND JUJUYASPIS KEIDELI KOBAYASHI (TRILOBITA) FROM THE ALFARCITO MEMBER OF THE SANTA ROSITA FORMATION, QUEBRADA DE HUMAHUACA, CORDILLERA ORIENTAL OF JUJUY

摘要

CAMBRIAN CONODONTS AND Cambro-Ordovician JUJUYASPIS KEIDELI KOBAYASHI (TRILOBITA) FROM THE ALFARCITO MEMBER OF THE SANTA ROSITA FORMATION, QUEBRADA DE HUMAHUACA, CORDILLERA ORIENTAL OF JUJUY. A conodont fauna from the lower levels of the Alfarcito Member (Santa Rosita Formation) at the Salto Alto section, Quebrada de Humahuaca, is analyzed. Recorded conodonts are associated to the trilobite Jujuyaspis keideli keideli Kobayashi, among others, which represents the homonymous zone. Although the range of this taxon has been considered largely to be restricted to the lower Tremadocian (basal Lower Ordovician), the conodont assemblage refers to the Cordylodus intermedius Zone, Hirsutodontus simplex Subzone, from the upper Cambrian. The conodont species Albiconus postcostatus Miller, Cordylodus cf. andresi Viira and Sergeyeva, C. cf. tortus Barnes, Hirsutodontus simplex (Druce and Jones), Variabiloconus datsonensis (Druce and Jones), ? "Prooneotodus" mitriformis Dubinina, Prosagittodontus sp., Teridontus gallicus Serpagli, Ferretti, Nicoll and Serventi, and Westergaardodina polymorpha Muller and Hinz, are described for the first time in the Cordillera Oriental of Argentina from Cambrian levels. The faunal assemblage shows a strong resemblance with that one found in western Newfoundland incorporating Baltic taxa. Therefore, the faunal condition fits consistently with previous paleobiogeographic reconstructions for this latitude.