Bivalvos pérmicos de la Formación Tupe en la quebrada de La Herradura, provincia de San Juan

Andra F. Sterren

Abstract


Resumen. En este trabajo se dan a conocer bivalvos provenientes de la Formación Tupe en la quebrada de La Herradura, ubicada en la vertiente occidental de la sierra de Perico, a 20 km al noreste de Jáchal en la provincia de San Juan. Se describen nueve especies: Nuculavus levatiformis (Walcott), Phestia sp. aff. P. bellistriata (Stevens), Modiolus (Modiolus) sp., Septimyalina sp., Palaeolima retifera (Shumard), Aviculopecten sp., Streblochondria sp., Schizodus sp. y Pleurophorella ? sp. Los bivalvos estudiados son de edad pérmica temprana, indicada por la fauna de braquiópodos asociada, que corresponde a la Biozona de Tivertonia jachalensis-Streptorhynchus inaequiornatus. Entre los bivalvos que integran esta biozona se reconocen géneros con afinidades tethyanas que sugieren temperaturas relativamente más elevadas que las inferidas previamente en la región. Se analiza el contexto paleogeográfico y se discuten brevemente las posibles causas que habrían favorecido la composición de esta fauna.


Abstract. PERMIAN BIVALVES FROM THE TUPE FORMATION IN THE HERRADURA CREEK, SAN JUAN PROVINCE. A taxonomic analysis of bivalves from the Tupe Formation in the La Herradura Creek, located on the western flank of Perico Hill, about 20 km northeast of Jáchal, San Juan province is carried out. Nine species are described and figured: Nuculavus levatiformis (Walcott), Phestia sp. aff. P. bellistriata (Stevens), Modiolus (Modiolus) sp., Septimyalina sp., Palaeolima retifera (Shumard), Aviculopecten sp., Streblochondria sp., Schizodus sp., and Pleurophorella ? sp. An Early Permian age is suggested for the studied bivalves in view of their occurrence along with brachiopods belonging to the Tivertonia jachalensis-Streptorhynchus inaequiornatus Zone. Some genera with tethyan affinities are recognized among the bivalves present in this biozone. These genera suggest relatively higher temperatures than those previously inferred for the region at that time. The paleogeographic context is analyzed, and the possible influential factors upon the faunal composition are briefly discussed.