THE ORDOVICIAN CONODONT FAUNA OF THE SANTA GERTRUDIS FORMATION, CORDILLERA ORIENTAL OF NW ARGENTINA: NEW TAXA, AGE AND ENVIRONMENTAL SIGNIFICANCE

G. L. ALBANESI; R. J. ALDRIDGE

Simposio; 3rd International Conodont Symposium & Regional Field Meeting IGCP 591; 2013

e Santa Gertrudis Formation, which crops out in the Mojotoro Range, close to Salta city, bears a conodont fauna that includes similar taxato those mentioned by Iglesias (1949) from the Sierras Subandinas of Jujuy, in the first report on conodonts from Argentina. Brief publicationshave subsequently dealt with the Santa Gertrudis fauna, revealing taxonomic and biostratigraphic problems. is contribution describes all ofthe species recorded from the uppermost strata of the Santa Gertrudis Formation, representing Erismodus, Erraticodon, Plectodina, Semiacontiodus,and new genera. e host rock is a massive dark mudstone with a shelly fauna dominated by linguliid brachiopods, probably representing alagoonal environment. e conodont elements are exquisitely preserved, with a CAI 1.5 and without evidence of reworking, in contrast torecent interpretations by other authors. e conodont fauna is related to previously reported faunas from the Central Andean Basin, i.e. theCapillas Formation of the Sierras Subandinas and the Sepulturas Formation of the Cordillera Oriental of Jujuy, but it is either slightly older orfrom a different contemporaneous facies. e Capillas and Sepulturas formations share some species with the Santa Gertrudis Formation buthave also yielded remains of the oldest pteraspidomophs of South America, Sacabambaspis janvieri Gagnier et al. Elsewhere, in the La CanteraFormation of the Precordillera of San Juan Province, Argentina, Sacabambaspis has been dated as Middle Darriwilian by its association withconodonts of the Pygodus serra Zone.