Oblique half-graben inversion of the Mesozoic Neuquén Rift in the Malargüe Fold and Thrust Belt, Mendoza, Argentina: New Insights from analogue models.

YAGUPSKY D.; CRISTALLINI, E.O.; FANTIN, J.; ZAMORA VALCARCE, G.; BOTTESI, G.; VARADE, R.

JOURNAL OF STRUCTURAL GEOLOGY

Elsevier Ltd.

Año: 2008 vol. 30 p. 839 - 853

0191-8141

The Malargu¨ e fold and thrust belt, located in the Andean mountains between 34S and 36300S, formed in response to contraction during Cenozoic times. Its structural style and geometry was controlled by the Mesozoic rift system that formed the Neuque´n basin in west-central Argentina. The rift architecture in the southern sector of this belt was previously interpreted in terms of the present N?S compressive structural trends, assuming the inversion of pre-existing normal faults with the same orientation. Here, we propose that the NW?SE-trending El Manzano?Liu Cullý´n lineament, located in the northern termination of the Sierra Azul, reflects the presence of a half-graben master fault in the subsurface. This hypothesis is supported by subsurface data, a balanced cross section, and it is tested using a series of scaled sandbox analogue models. We suggest that the lineament responds to a reactivated NW-trending half-graben fault, hidden by the mainly N?S-trending Andean structures. The proposed orientation is in agreement with the NE?SWextension developed in the Neuque´n basin during the Triassic?Early Jurassic. The modeling of the inverted oblique half-graben reveals that the strikes of the main structures of inversion-related belts may often be independent of the orientation of the previously developed extensional system, providing a new perspective for their interpretation.0S, formed in response to contraction during Cenozoic times. Its structural style and geometry was controlled by the Mesozoic rift system that formed the Neuque´n basin in west-central Argentina. The rift architecture in the southern sector of this belt was previously interpreted in terms of the present N?S compressive structural trends, assuming the inversion of pre-existing normal faults with the same orientation. Here, we propose that the NW?SE-trending El Manzano?Liu Cullý´n lineament, located in the northern termination of the Sierra Azul, reflects the presence of a half-graben master fault in the subsurface. This hypothesis is supported by subsurface data, a balanced cross section, and it is tested using a series of scaled sandbox analogue models. We suggest that the lineament responds to a reactivated NW-trending half-graben fault, hidden by the mainly N?S-trending Andean structures. The proposed orientation is in agreement with the NE?SWextension developed in the Neuque´n basin during the Triassic?Early Jurassic. The modeling of the inverted oblique half-graben reveals that the strikes of the main structures of inversion-related belts may often be independent of the orientation of the previously developed extensional system, providing a new perspective for their interpretation.