La cuenca de antepais terciaria asociada a la faja plegada y corrida de los Andes Patagónicos entre los 41º y 42º S, SO de Argentina

In Argentina, between 41"-42" S and related to the Andean Patagonian fold and thrust belt, two synorogenic sedimentary sequences were deposited in the Tertiary foreland basin. They represent different moments of the eastward migration of the orogenic front, during upper Eocene to Mio-Pliocene times. The units within the sequence have a characteristic wedge shape, and the proximal facies on the west, prograde to the east and cover the lower distal-medium facies. Structural relationships diplay discordant boundanes near the active orogenic front, which progressively change to concordant towards the foreland. Eocene-Oligocene volcano-sedimentary basa1 sequence contains marine intercalations with Pacific affinities, while Oligocene-lower Pliocene upper sequence has a sedimentary-pyroclastic composition. Based on the age and geometrical characteristics, we proposed a preliminary correlation between proximal to distal facies in the synorogenic formations, and the well known litostratigraphic units outcropping in the El Bolsón valley and the Ñirihuau-Collón Cura basin