Artículos de revistas
Paleoenvironments and age of the Talampaya Formation: The Permo-Triassic boundary in northwestern Argentina
Fecha
2015-08Registro en:
Gulbranson, Erik L.; Ciccioli, Patricia Lucia; Montañez, Isabel P.; Marenssi, Sergio Alfredo; Limarino, Carlos Oscar; et al.; Paleoenvironments and age of the Talampaya Formation: The Permo-Triassic boundary in northwestern Argentina; Elsevier; Journal of South American Earth Sciences; 63; 8-2015; 310-322
0895-9811
CONICET Digital
CONICET
Autor
Gulbranson, Erik L.
Ciccioli, Patricia Lucia
Montañez, Isabel P.
Marenssi, Sergio Alfredo
Limarino, Carlos Oscar
Schmitz, M. D.
Davydov, V.
Resumen
The Talampaya Formation is the basal unit of the Ischigualasto-Villa Unión rift system and has been traditionally assigned to the Triassic based on stratigraphic relationships. A median U–Pb age of 252.38 (+0.09/−0.22) Ma was obtained from volcanic zircons collected from a tuff bed close to the top of this unit at the Bordo Atravesado locality in the Cuesta de Miranda area (La Rioja, Argentina). This radiometric age is very close to the accepted Permian–Triassic boundary indicating that, at least in this locality, sedimentation occurred during the Late Permian but may have extended into the earliest Triassic. This new evidence indicates that the onset of the extensional event that gave rise to the rift basins in western Argentina started during the Permian. Detailed sedimentological studies of the 260 m thick Talampaya Formation allowed subdividing the succession into seven facies associations grouped into three evolutionary stages indicating that sedimentary environments initially evolved from alluvial fans to a braided river system. Subsequent intrabasinal volcanism associated with sediment deposition by low-to moderate-sinuosity rivers is recorded in the lower third of the column. The middle and upper part of the unit captures the evolution from ephemeral fluvial systems with an eolian interval to an ephemeral clastic lake with intermittent volcanic ash deposits. These changes indicate a progressive lowering of the landscape and a transition towards arid or semiarid conditions.