Preserved extensional structures in an inverted Cretaceous rift basin, northwestern Argentina: Outcrop examples and implications for fault reactivation

Abstract

During the Cretaceous‐Eocene interval a system of intracontinental rift basins, the Salta group rift, evolved in northwestern Argentina. Individual segments of the rift later suffered different degrees of inversion during Cenozoic shortening. The Tres Cruces subbasin, on the west side of the Eastern Cordillera, was strongly deformed, being now part of a thick‐skinned thrust belt with a predominantly N‐S structural trend. On its eastern border, tilting due to folding and thrusting and subsequent erosion have produced exceptional outcrops of preserved east‐trending extensional structures including half grabens, rollover anticlines, and extensional fault‐propagation folds. Farther west, the synrift succession is only intermittently exposed, although the interference of north‐ and east‐trending structures as well as peculiar, dome‐shaped anticlines with spur‐like extensions suggest that north‐ and east‐trending Cretaceous faults were reactivated, particularly near their intersections. Compilation of published data and analysis of our new data focused on the Salta rift indicates three main factors favoring the contractional reactivation of normal faults: dip angles lower than approximately 60°, especially for faults striking roughly normal to contraction; strikes no closer to the contraction direction than approximately 30°; and low downdip fault curvatures. Occasional dip‐slip reactivation of east‐trending faults does not match the present and long‐term Andean stress regimes and presents an unresolved problem.

Synorogenic foreland rifts and transtensional basins: A review of Andean imprints on the evolution of the San Jorge Gulf, Salta Group and Taubaté Basins

“…According to Bianucci et al (1981Bianucci et al ( , 1999 Basin fill were progressively incorporated into the orogenic wedge as it expanded eastwards (Monaldi et al, 2008, DeCelles et al, 2011 (Fig.11C). Thus, the Lomas Olmedo Subbasin turned transpressively deformed with different degrees of inversion (Chiarenza and Ponzoni, 1989, Comínguez and Ramos, 1995, Bianucci et al, 1999.…”

“…Also, similarly oriented release faults in the Tres Cruces Sub-basin were also slightly reactivated during this stage (Monaldi et al, 2008). This process could have been progressively inhibited since the late Eocene when intense orogenesis inverted most of the Salta Group Basin filling (Fig.11B).…”

“…On the other hand, a late extensional reactivation event, well documented through seismic surveys, was associated with normal faulting affecting post-rift units mostly in Lomas de Olmedo Sub-basin (Bianucci et al, 1981, 1999, Comínguez and Ramos, 1995, Monaldi et al, 2008 (Fig.9A). This poorly understood late extensional event was responsible for base level fall, variations in sedimentary thicknesses and facial changes in post-rift units (Bianucci, 1981, 1999, Gómez Omil and Boll, 1989, Di Persia, 1991, Monaldi et al, 2008, Starck, 2011 ( Fig.8, 9B and 9C). Particularly, the Pre-Olmedo event, that took place between the Yacoraite and Olmedo Fms.…”

Basin fragmentation controlled by tectonic inversion and basement uplift in Sierras Pampeanas and Santa Bárbara System, northwest Argentina

“…During the Cretaceous a back-arc rift basin was developed with many sub-basins of different trends (Salfity & Marquillas 1981;Monaldi et al 2008), named the Salta Rift and constituted by a series of extensional troughs or sub-basins (Fig. 2).…”

The role of inherited extensional fault segmentation and linkage in contractional orogenesis: a reconstruction of Lower Cretaceous inverted rift basins in the Eastern Cordillera of Colombia

“…In the more severely inverted basins of many orogens, however, detailed ¢eld-based accounts regarding the mechanical interaction of segmented former extensional faults, the nature of displacement transfer, and how such structures are incorporated into the orogenic realm are rare (Hayward & Graham, 1989;Garc|¤ a Senz, 2002;Kley et al, 2005;Monaldi et al, 2008). These problems are often compounded by a general lack of good seismic images with unequivocal extensional features.…”