Styles of Deformation and Kinematics of Mesozoic Intraforeland Inversion Structures, Central Neuquén Basin, Argentina

Gabriel O. Grimaldi and Steven L. Dorobek
Texas A&M University, College Station, TX

Most published descriptions of inversion structures provide only 2-dimensional views of structural style and tectono-stratigraphic relationships that develop during inversion. Analog models show lateral variations in structural style and stratigraphic development during inversion, but similar relationships have rarely been documented in natural inversion structures, limiting our understanding of the three-dimensional aspects of these features. Late Triassic rift basins within the central Neuquén Basin of Argentina were inverted during transpressional deformation along the Huincul Arch, a 200-km-long, east-west trending, right-lateral shear zone that cuts across the Argentine foreland. Deformation along the Huincul Arch was most active during Jurassic to Cretaceous time, predating the main Andean orogeny. Inversion structures are best developed at a mega-restraining bend along the Huincul shear zone. Some of the inversion structures are imaged in several 3D seismic volumes from north of the Huincul Arch. Lateral and vertical stratigraphic and structural relationships were evaluated to characterize the kinematic history of inversion structures and to identify possible responses of Jurassic-Cretaceous depositional systems to deformation. Triassic rift-related depocenters were inverted with decreasing intensity from southwest to northeast across the Huincul region. During inversion, hangingwalls of former rift half-grabens and their overlying post-rift section were deformed into asymmetric, antiformal structures with steeper limbs cut by reverse faults propagating upward and laterally from reactivated syn-rift normal faults. Normal faults with less vertical offset are oriented roughly perpendicular to reactivated syn-rift normal faults and indicate expansion of the hangingwall's post-rift section during inversion. Stratigraphic relationships show southward migration of structural axes during inversion.

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