The Agrio Fold And Thrust Belt: Structural Analysis And Its Relationship With The Petroleum System Vaca Muerta-Agrio-Troncoso Inferior (!), Argentina

Abstract

The structural style of the Agrio Fold and Thrust belt of the Neuquen Basin, Argentina, is characterized by = the insertion of basement tectonic wedges into the sedimentary column that deform pre-existing thinskinned triangle zones; constituting a multi-episodic orogen. Based on the revision of regional geologic data and carefull analysis of cross-cutting field relationships it can be determined that the upper limit of the beginning of the Andean deformation of the Agrio FTB, given by the extrusive rocks of the Colipilli-Cayanta Fm., corresponds to the Lower to Middle Eocene. These units are intruding and covering the previously formed structures. Other authors lower this age down to the Senonian (Upper Cretaceous) and it would be manifested by the unconformity between the Rayoso Fm and the Neuquen Group. Within the study area, the cross-cutting field relationships may lower this age up to Cerro Lisandro Mb. (88 Ma?); with another reactivation pulse at the Lower to Middle Miocene (18-12 Ma). These evidence allow to adjust the timing relationship to the critical moment of the petroleum system (Upper Cretaceous) Vaca Muerta-Agrio-Troncoso Inferior; contrarily to conclusions of previous studies that showed only one uplift event of Miocene age. The application of new structural models, together with the change in the timing relationship promotes the study of new exploratory leads for liquid hydrocarbons. Finally a new regional correlation for the Tertiary in this area of the Agrio Fold and Thrust belt is proposed.