The age of the Tunas Formation in the Sauce Grande basin-Ventana foldbelt (argentina): implications for the Permian evolution of the southwestern margin of Gondwana

LOPEZ-GAMUNDÌ, O.R., A. FILDANI, A. WISOGEL & E.A. ROSSELLO

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2013 p. 250 - 258

0895-9811

New SHRIMP radiogenic isotope dating on zircons in tuffs (280.8 1.9 Ma) confirms the Early Permian(Artinskian) age of the uppermost section of the Tunas Formation. Tuff-rich levels in the Tunas Formationare exposed in the Ventana foldbelt of central Argentina; they are part of a deltaic to fluvial sectioncorresponding to the late overfilled stage of the Late Paleozoic Sauce Grande foreland basin. RecentSHRIMP dating of zircons from the basal Choiyoi volcanics exposed in western Argentina yielded an ageof 281.4 2.5 Ma (Rocha-Campos et al., 2011). The new data for the Tunas tuffs suggest that thevolcanism present in the Sauce Grande basin can be considered as the distal equivalent of the earliestepisodes of the Choiyoi volcanism of western Argentina. From the palaeoclimatic viewpoint the newTunas SHRIMP age confirms that by early Artinskian glacial conditions ceased in the Sauce Grande basinand, probably, in adajacent basins in western Gondwana.