High resolution trilobite biostratigraphy for the early late Tremadocian (Tr2) interval (Early Ordovician) Santa Rosita Formation, Argentine Cordillera Oriental

MEROI AERCERITO, FACUNDO; WAISFELD, BEATRIZ; VACCARI, EMILIO; MUÑOZ, DIEGO

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2018 vol. 55 p. 531 - 553

0002-7014

The early late Tremadocian (Tr2) interval is exceptionally well represented in eastern areas of the Argentine Cordillera Oriental. New field collections and a detailed taxonomic work, as well as a revaluation of regional data, permit the development of a highly resolved biostratigraphic framework based on trilobites. The concept of the traditional Bienvillia tetragonalis biozone is emended and the new Asaphellus nazarenensis biozone is proposed. Hence, the Tr2 interval encompasses a succession of four trilobite biozones including in ascending order the K. teiichi, the B. tetragonalis, the A. nazarenensis, and the N. orthometopa biozones. This resolution is notably higher than that provided by biostratigraphically significant groups such as graptolites and conodonts, and allows a detailed basinwide correlation. New taxonomic information on A. nazarenensis and N. orthometopa is provided and the new species Asaphellus alba sp. nov. is defined. Detailed correlation of the trilobite fauna from the Tr2 interval with that of other paleocontinents is difficult. Taxa are mostly endemic or display wide geographic distribution but long stratigraphic ranges. Overall, both trilobite-based and indirect international correlations highlight that this interval is hardly recognized, incompletely preserved, or the trilobite fauna is poorly known in most areas of Gondwana. Consequently, due to the completeness of the stratigraphic and fossil records of the Tr2 in the Cordillera Oriental, this region represents a worldwide reference site for the study of this interval.