Presencia de niveles piroclásticos pérmicos en las Sierras Australes-cuenca de Claromecó, provincia de Buenos Aires

ARZADÚN, G; TOMEZZOLI R.N.; TRINDADE, R.I.F.; GALLO, L.C.; CESARETTI, N.N.

S.M. de Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

Asociación Geológica Argentina

In the Tunas Formation (Harrington 1947), Permian of Gondwana, two pyroclastic levels were dated, one of them corresponding to an outcrop situated in its base, in the Sierras Australes, and the other intercalated with coal levels in the PANG0001 well, in the Claromecó Basin. The levels classify as fine tuff and tonsteins. The U/Pb age in zircons are 291.7 ± 2.9 Ma in the outcrop sample and 295.5 ± 8.0 Ma in the well sample (Sakmarian, low Permian). Older ages were obtained that correspond to zircons of older sources. The ages coincide with ages obtained in other outcrop of the Tunas Formation, with paleomagnetic data and with the fossil findings and they are correlated with other U/Pb ages of tuff intercalated in sequences of the Parana Basin in Brazil, and the Karoo Basin in South Africa, all basins situated at the southwest margin of Gondwana. The data suggest a regional event due to the San Rafael orogenic fase that produces a Permian age deformation.