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Abstract

AAPG Bulletin, V. 95, No. 1 (January 2011), P. 27-60.

Copyright copy2011. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/06301009165

Fault framework and kinematic evolution of inversion structures: Natural examples from the Neuquen Basin, Argentina

Gabriel O. Grimaldi,1 Steven L. Dorobek2

1Department of Geology and Geophysics, Texas AampM University, College Station, Texas 77843; present address: Chevron Global Upstream and Gas, 1500 Louisiana Street, Houston, Texas 77382; [email protected]
2Department of Geology and Geophysics, Texas AampM University, College Station, Texas 77843; present address: BP America, 501 Westlake Park Boulevard, Houston, Texas 77079; [email protected]

ABSTRACT

Mesozoic tectonic inversion in the Neuquen Basin of west-central Argentina was investigated by analyzing a three-dimensional seismic and borehole data set over prominent inversion structures related to transpressional tectonics along the Huincul arch. This conspicuous strike-slip deformation has been active since the Early Jurassic to Early Cretaceous and caused the reactivation of normal faults and the inversion of Triassic half grabens, some of which are imaged by the seismic data. Detailed structural and stratigraphic mapping allowed the identification of two main fault systems associated with inversion structures: (1) deep faults that affected basement and synrift strata where preexisting faults were selectively reactivated during inversion based on their length and (2) shallow faults that affected postrift and syninversion strata. Normal faults formed at high angle to the reactivated half-graben bounding fault as a result of hanging-wall expansion and internal deformation as it accommodated the shape of the curved footwall during oblique inversion. Structural restorations suggest that contraction during inversion was initially accommodated by folding and internal deformation of synrift sedimentary wedges, followed by displacement along half-graben bounding faults. We suspect that during late inversion, the weight of the overburden inhibited additional fault displacement and folding became the main shortening-accommodating mechanism. Natural examples described in this study exhibit significant along-strike variation in structural style and high structural complexity associated with relatively small amounts of inversion, which suggest the need for incorporating more complex deformation scenarios into analog models. Fault framework development and its linkage to a specific mechanism (e.g., hanging-wall deformation because of oblique inversion) enables the predictive analysis of subseismic faulting and fracture distribution, which can impact our understanding of the petroleum systems in the Neuquen Basin's northern embayment, especially regarding the significant fault development within the Cuyo Group, which may impact the Los Molles petroleum system.

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