Biostratigraphy of the Upper Paleozoic of the Tres Lagunas Valley, Tepuel Hill, Chubut Province

Abstract

?Biostratigraphy of the Upper Paleozoic of the Tres Lagunas Valley, Tepuel Hill, Chubut Province?. The neopaleozoic of the Tres Lagunas Valley reaches 1600 m of thickness, constituting the upper third of the sequence of Tepuel. Three sections are distinguished, the lower one (Section I) in the uppermost terms of the Pampa de Tepuel Formation and the others two (Sections II and III) in the younger Mojon de Hierro Formation. Section includes glacimarine outcrops with marked lateral facial variations and the top of the Levipustula levis biozone (Namurian ? Upper Westphalian?). Sections II and III include marine deposits with the Costatumulus amosi (ex Cancrinella cf. farlevensis) fauna, corresponding with the widespread sea level rise that takes place at the end of the glaciations of the Upper Paleozoic (Asselian-Tastubian) in the whole Gondwana. This fauna would have been developed almost parallelly to the Eurydesma's fauna but in lower paleolatitudes or in less cold seas. An important interruption of the stratigraphic record would take place in the interval between the Levipustula and Costatumulus biozones, more precisely in the contact between the Pampa de Tepuel and Mojon de Hierro Formations and it would include the Stephanian (?).