Tectonic architecture of the Tarapacá Basin in the northern Central Andes: New constraints from field and 2D seismic data

Abstract

The Tarapacá Basin is one of the larger basins created on the western margin of South America during the Mesozoic times. Regional studies focused their attention on understanding its Cenozoic surface structures, traditionally interpreted as a west-verging thrust and fold belt. However, its internal and deep architecture and the influence of previously developed Mesozoic extensional structures on its current structure have not been analyzed in detail. We used new field data and 2D seismic data to determine the tectonic architecture of the Tarapacá Basin. We have paid special attention to defining both the deep and superficial structures to understand its tectonic evolution. The seismic data reveal the existence of a series of half-graben structures along which Mesozoic synrift stratigraphic sequences accumulated. We also show that Upper Cretaceous and Cenozoic synorogenic sequences mainly accumulated over contractional folds (anticlines and synclines). The structure is characterized by a thickskinned structural style dominated by structures inverted during the oblique reactivation of ancient Mesozoic normal faults and also by newly formed reverse faults in the form of shortcut and bypass faults. The presence of Upper Cretaceous to Tertiary synorogenic sequences over the contractional structures, separated by angular unconformities, allowed us to show that the basin inversion and its subsequent deformation occurred at least since the Late Cretaceous until Recent times. These results aid in understanding the role of extensional structures in the evolution of orogenic belts and can be compared with similar structures around the world.

Northward propagation of Andean genesis: Insights from Early Cretaceous synorogenic deposits in the Aysén-Río Mayo basin

“…Further to the south in the Central Andes between 20°S and 25°S, the beginning of Cretaceous contraction is well recorded within the Tarapacá and Atacama foreland basins (Schiller, 1912;Mpodozis et al, 2005;Arriagada et al, 2006;Fuentes et al, 2018;Martínez et al, 2018a) (Fig. 1a).…”

“…We suggest that this tectonic pattern is not likely the result of selective erosion of earliest synorogenic deposits in the Andes. The latter is supported by the preservation of Early Cretaceous sedimentary rocks in several basins of the Central and Northern Andes associated with thermal subsidence or basin extension (Jaillar and Soler, 1996;Charrier et al, 2007;Ramos, 2009;Menegazzo et al, 2016;Fuentes et al, 2018;Zapata et al, 2018; among others).…”

Effects of pre‐orogenic tectonic structures on the Cenozoic evolution of Andean deformed belts: Evidence from the Salar de Punta Negra Basin in the Central Andes of Northern Chile

“…Our results indicate that, in the Salar de Punta Negra Basin, the tectonic inversion of basement normal faults was an important mechanism during the first contractional deformation episodes and for the creation of the early relief in the inner forearc of the southern Central Andes (23º–24ºS). These inverted normal faults produced inversion anticlines, which have been recognized in neighbouring regions, such as the Domeyko Cordillera and Tarapacá Basin in Chile (Amilibia et al, 2008; Fuentes et al, 2018), and the Salta Basin and the Puna plateau in Argentina (Carrera et al, 2006; Iaffa et al, 2011; Kley et al, 2005; Monaldi et al, 2008). The pre‐orogenic normal faults in the Salar de Punta Negra Basin mostly consist of east‐dipping fault with secondary west‐dipping faults (Martínez et al, 2018) related to Paleozoic (mainly Permian) and Mesozoic back‐arc extensional‐related basins (Figures 12–14).…”

“…Farther to the west, in northern Chile between 22º and 26ºS (Figure 1), the interplay between the pre‐orogenic extensional and the contractional structures related to the Andean orogeny is not well understood. Although this region contains examples of tectonic interaction between Mesozoic and Andean (late Cretaceous and younger) structures, only a few studies at these latitudes (Amilibia et al, 2008; Arriagada, Cobbold, & Roperch, 2006; Fuentes, Martínez, Bascuñán, Arriagada, & Muñoz Mardones, 2018; Jordan et al, 2007; Martínez, González, Bascuñan, & Arriagada, 2017; Martínez, López, Bascuñan, & Arriagada, 2018; Rubilar, Martínez, Arriagada, Becerra, & Bascuñán, 2017) have analysed the position and geometry of the pre‐orogenic Mesozoic extensional systems and their influence on the growth of the western Central Andes. To understand the effects of pre‐orogenic structures on the tectonic evolution of the Andean structures, we analysed the inner forearc region of the Central Andes, specifically using the Salar de Punta Negra Basin in northern Chile (24º–25ºS, Figure 1) as a case study.…”

Complex Basement‐Involved Contractional Structures in the Pre‐Andean Basins of Northern Chile: A Review From Seismic Data

“…17 of 23 et Arriagada et al, 2006;Fuentes et al, 2018;López et al, 2019;Martínez et al, 2019). They have indicated that the basement-involved structures result from the positive reactivation of ancient Mesozoic extensional faults.…”