Tectonic interaction between Mesozoic to Cenozoic extensional and contractional structures in the Preandean Depression (23°–25°S): Geologic implications for the Central Andes

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

“…The new U-Pb detrital zircon ages reported from the syn-kinematic sedimentary rocks of the Pajonales Formation exposed in the footwall block of an east-verging basement reverse fault (see details in Figures 2 and 4) along the northern basin (eastern Sierra de Almeida) and outside of the 2-D seismic coverage, suggest that contractional deformation started at least during the late Cretaceous. These rocks could be correlated with the Upper Cretaceous syn-kinematic Purilactis Formation exposed in the northwest part Salar de Atacama Basin (Bascuñan et al, 2015;Bascuñan et al, 2019) and also with those syn-kinematic seismic reflection packages identified under Paleocene tectonosequences in the central part of the basin (Figure 13; Martínez et al, 2018). Based on this, we suggest that basement faulting within the study area originated between the late-Cretaceous and Paleocene periods ( Figures 12-14).…”

“…The basal sections consist of Upper Cretaceous to Paleocene continental and sedimentary successions composed of 100 m of red conglomerates, sandstones and shale beds of the Pajonales Formation (Figure 4a) and 600 m of volcanic, orange conglomerates and sandstones defined as the Naranja Formation (Figure 4b and 4c). These successions have been correlated to similar cretaceous through Cenozoic rocks in the Salar de Atacama Basin (Figure 1) north of the study area (Arriagada et al, 2006; Martínez et al, 2018; Ramírez & Gardeweg, 1982; Solari et al, 2017). The Upper Cretaceous and Paleocene successions have previously been interpreted as syn‐kinematic basin deposits accumulated during the shortening of the pre‐Andean Depression (Bascuñan, Arriagada, Roux, & Deckart, 2015; Henriquez, DeCelles, & Carrapa, 2019; Martínez, López, Parra, & Espinoza, 2019).…”

“…The inversion anticlinal folds form part of a regional contractional domain that is also recognized in the Salar de Atacama Basin (Martínez et al, 2018). They commonly display along-strike variations in their wavelength.…”

“…The Upper Cretaceous and Paleocene successions have previously been interpreted as syn‐kinematic basin deposits accumulated during the shortening of the pre‐Andean Depression (Bascuñan, Arriagada, Roux, & Deckart, 2015; Henriquez, DeCelles, & Carrapa, 2019; Martínez, López, Parra, & Espinoza, 2019). The syn‐kinematic nature of these strata is based on their fan geometry observed in W‐E–oriented seismic profiles distributed along the central and northern parts of the Salar de Atacama and Salar de Punta Negra basins, respectively (Arriagada et al, 2006; Martínez et al, 2018), which showed growth strata over contractional structures.…”

“…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.…”