Intraplate Foreland Deformation in the Neuquén Embayment

Alfonso Mosquera¹ and Victor A. Ramos^2
1 Tecpetrol S.A, Buenos Aires, Argentina
² University of Buenos Aires, Buenos Aires, Argentina

The Neuquén embayment developed along the eastern foothills of the southern Central Andes, one of the most prolific hydrocarbon basins of southern South America (EUR: 9700 MMBOE), records a complex history of Mesozoic and Cenozoic retroarc-foreland intraplate deformation. Intraplate deformation was the result of three main elements, Paleozoic basement fabrics, Early Jurassic hemigrabens and convergence vectors between the Aluk, Farallon, and Nazca oceanic plates and the Gondwana or South American continental plates. Three main basement fabrics, E-W (Huincul system-southern margin), NW-SE(Entre Lomas system – eastern margin) and N-S( Chihuidos system – western depocenter)resulted form the accretion of three terranes to the Gondwana margin during the Paleozoic. Three stages of intraplate deformation were identified that postdated a brief Early Jurassic rift stage that resulted in a dense mosaic of hemigrabens The Aluk stage (Early Jurassic-Valanginian) is the earliest contraction episode, with the main stress oriented in the N-NW sector. It resulted in the tectonic inversion by contraction and right lateral strike slip deformation of the Huincul system and subtle deformation in the Chihuidos and Entre Lomas systems. The Farallon stage (Valanginian-Miocene) with a more orthogonal orientation, resulted in a westward retreat of the deformation along the southern margin and an increase of the inversion along the Entre Lomas system during the Cenomanian, together with the westward inception of the Agrio fold belt. Nazca stage, with orthogonal stress resulted in the development of the fold belt and broken foreland system. Stress changes were correlated with the pacific and Gondwana –South America plate convergence vectors.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005