The Salina del Fraile pull-apart basin, northwest Argentina

Abstract

The Salina del Fraile in northwest Argentina is a Pliocene to Recent pull-apart basin developed at a releasing stepover along the NNE-SSW-trending E1 Fraile sinistral strike-slip fault. The basin is 35 km long and 12 km wide with a characteristic rhomboidal shape and is starved of synkinematic sediments thus providing unique 3D exposures. Prominent basin sidewall fault systems form scarps 700 m high and large tilted fault blocks form a terraced system along the southwest basin sidewall. A short-cut, basin-floor fault transects the pull-apart basin connecting the northwest strand of the El Fraile Fault to the southeast strand. An anticlinal positive flower structure in the northwest of the basin is a relict of early, segmented, fault growth typical of strike-slip fault evolution. Extension faults in the basin floor indicate a NE-SW intrabasinal extension direction during the Pliocene to Recent. The pull-apart basin accommodates an estimated 7.7 km of sinistral displacement along the E! Fraile fault system. The morphology and fault architecture of the Salina del Fraile pull-apart can be directly compared to scaled sandbox models of strike-slip pull-apart basins. This first detailed analysis of the Salina del Fraile pull-apart basin provides a model for 3D architecture and evolution of similar pullapart basins, and may serve as a template for the interpretation of other pull-apart systems.

Normal faulting along the southern margin of the Puna Plateau, northwest Argentina

“…Digital topography of southern Puna Plateau (SRTM 90 m data, http://seamless.usgs.gov/ index.php). Active normal, strike-slip, and thrust faults compiled from Allmendinger [1986], Allmendinger et al [1989], Martinez [1995], Mon and Salfity [1995], Mon and Mansilla [1998], Reijs and McClay [2003], Schnurr [2003], and our own interpretation of SRTM and Landsat (https://zulu.ssc.nasa.gov/mrsid/) satellite imagery. Note that extensional faulting is almost completely confined to the plateau as defined by the line of internal drainage (heavy blue dashed line) or the smoothed 3000 m contour (white).…”

“…Near Pastos Grandes a normal fault cuts 1.5 Ma lacustrine sediments [Strecker, 1987]. Although not very well constrained, the Salina del Fraile basin to the west of the Salar de Antofalla may accommodate extension in a left-stepping pull-apart basin along the sinistral El Fraile fault [Reijs and McClay, 2003]. At Tiomayo a 6.75 ± 0.05 Ma ignimbrite is displaced [Ort, 1991;Cladouhos et al, 1994].…”

Volcanism and tectonism in the southern Central Andes: Tempo, styles, and relationships

“…The northern Imilac-Salina del Fraile lineament is recognized in the Salina del Fraile pull-apart basin, previously identified as a NNE sinistral strike-slip fault (Reijs and McClay, 2003). Nevertheless, our observations allow us to redefine this basin as a consequence of a NW-SE dextral transtension fault.…”

Flexural basin reworked by salt-related pull-apart structures: the Adony Basin

“…A significant difference to other strike-slip basins in a similar evolutionary stage (e.g. Reijs and McClay 2003;Cembrano et al 2005), as well as analogue models on pull-aparts (e.g. Dooley and McClay 1997;Wu et al 2009) is the lack of cross-basin shortcut faults.…”