PALEOECOLOGY AND PALEOBIOGEOGRAPHY OF DARRIWILIAN CONODONTS FROM THE LAS CHACRITAS FORMATION, CENTRAL PRECORDILLERA OF SAN JUAN, ARGENTINA

F. SERRA; G. L. ALBANESI

PUBLICACION ESPECIAL - ASOCIACION PALEONTOLOGICA ARGENTINA

ASOCIACIÓN PALEONTOLÓGICA ARGENTINA

Año: 2013 p. 103 - 108

0328-347X

The study of Cambrian and Ordovician faunas has beenuseful for understanding the early history of the Precordilleraterrane, including its origin, trajectory and timing of accretion.Herrera and Benedetto (1991) suggested that in Darriwiliantime, Celtic and Baltic genera of brachiopods migrated into thePrecordillera basin, which resulted in a mixed Laurentian,Baltic, and Celtic provincial assemblage. Moreover, Benedettoet al. (2009) interpreted the similarity between Famatinan andPrecordilleran Darriwilian brachiopods as a result of the finalaccretion of the Precordillera terrane to the Gondwana margin.Lehnert et al. (1999) analyzed the Darriwilian-Sandbian conodontassociation from the Lindero Formation, which is partof the Cuyania Terrane. These authors suggested that the coldwater conodont fauna found in the shallow water strata in thelower part of their studied succession was due to a considerablegeographic separation between this region and Laurentia, thisPrecordillera region occupying a higher latitude position betweenLaurentia and Gondwana (Lehnert et al., 1999). Thestudy carried out by Albanesi (1998) stated that the lateTremadocian conodont assemblage from the Precordillera isclosely similar to that from the Tropical Domain, whereasFloian- Dapingian assemblages comprise a mixed fauna typicalof Baltica and peripheral environments of Laurentia. Albanesiand Bergström (2010) studied the Early and Middle Ordovician paleogeographic relations of the Precordillera Terrane using a precise comparison between conodont faunas from diverselocalities in the Precordillera, North America, Baltic region,China, and Australia. In agreement with the hypothesis thatthe Precordillera rifted from Laurentia and was exotic to Gondwana,the latter authors demonstrated that conodont speciesassemblage from the Precordillera shows significant similarityto that of the Tropical Domain in the Lower Ordovician.Previous studies on the conodont faunas from the LasChacritas Formation have centered on biostratigraphy. As anoriginal contribution, using a large data base of conodonts, weexamine in this study aspects of the conodont paleoecology.The purpose of this paper is to describe and analyze the dynamicsof the conodont communities through the upper San Juanand Las Chacritas formations in order to interpret the depositionalenvironments and the way changes in the paleoecologicalconditions affected the spatial distribution of the conodont faunasthrough the studied time span. In addition, we investigatedhow conodont associations contribute to a better understandingof the position of the Cuyania Terrane during the middleDarriwilian.