HIGH RESOLUTION TRILOBITE BIOSTRATIGRAPHY FOR THE EARLY LATE TREMADOCIAN (Tr2) INTERVAL (EARLY ORDOVICIAN) SANTA ROSITA FORMATION, ARGENTINE CORDILLERA ORIENTAL

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

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2018

0002-7014

Theearly late Tremadocian (Tr2) interval is exceptionally wellrepresented in eastern areas of the Argentine Cordillera Oriental.New field collections and detailedtaxonomic reassessments, as well as a revaluation of regional data,permit the development of a highly resolved trilobite-basedbiostratigraphic framework. The concept of the traditional Bienvilliatetragonalis biozone is emended and thenew Asaphellus nazarenensisbiozone is proposed. Hence, the Tr2 interval encompasses a successionof four trilobite biozones including in ascending order the Kainellateiichii, the Bienvilliatetragonalis, the Asaphellusnazarenensis, and the Notopeltisorthometopa biozones. This resolutionis notably higher than that provided by biostratigraphicallysignificant groups such as graptolites and conodonts, and allows adetailed basinwide correlation. New taxonomic information on A.nazarenensis Tortello and Esteban,2014, and N. orthometopa(Harrington, 1938), is provided and the new species Asaphellusalbae sp. nov. is defined. Detailedcorrelation of the trilobite fauna from the Tr2 interval with that ofother paleocontinents is difficult. Taxa are mostly endemic ordisplay wide geographic distribution but with long stratigraphicranges. Overall, both trilobite-based and indirect internationalcorrelations highlight that this interval is hardly recognized,incompletely preserved, or thetrilobite fauna ispoorly known in most areas of Gondwana. Consequently, due to thecompleteness of the stratigraphic and fossil records of the Tr2 inthe Cordillera Oriental, this region represents a global referencesite for the study of this interval.