EARLY CRETACEOUS (APTIAN) UPLIFT OF PATAGONIA RECORDED ON DETRITAL ZIRCONS POPULATION FROM THE PATAGONIAN ANDES

GHIGLIONE, M.C.; NAIPAUER, M; BARBERON, V.; RONDA, G.; PEREYRA-FERNÁNDEZ, E.; AGUIRRE-URRETA B.; VALENCIA, V.; RAMOS, V.A.

Córdoba

Congreso; XIX Congreso Geológico Argentino, Junio 2014, Córdoba; 2014

Detrital and volcanic zircon U-Pb geochronology was undertaken on the first coarse-grained regressive units represented by the Río Belgrano and Río Tarde Formations at the northern end of the basin in Lago Pueyrredón (Aguirre-Urreta and Ramos, 1981), revealing the maximum age for the ending of sag conditions. The maximum depositional age of the basal green sandstones of Río Belgrano Formation is 115.1 ± 2.1 Ma based on the youngest single zircon age, although a more conservative estimate would be the represented by a ~122 Ma age peak (Early Aptian), including 36% of the 98 dated zircons. The youngest single zircon of the overlaying red coarse sandstones of Río Tarde Formation yields an age of 118.4 ± 1.5 Ma, however the ~ 122 Ma peak (31% of dated zircons) is also present. The top of the sequence was dated by U/Pb from a volcanic tuff from the uppers levels of Río Tarde Formation, indicating an eruption age of 111.9 ± 1.5 Ma