East-vergent thrusts and inversion structures: An updated tectonic model to understand the Domeyko Cordillera and the Salar de Atacama Basin transition in the western Central Andes

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

“…This angular unconformity (see red unconformity in Figure 3) typically marks the transition from an extensional tectonic environment to a compressive one. The volcanic rocks have reported U-Pb ages of 80-70 Ma (Bascuñán et al, 2015(Bascuñán et al, , 2019Henríquez et al, 2018;Martínez et al, 2020; Figure 3) and exhibit important contractional growth strata along syncline folds, thereby recording the first tectonic pulse of Andean orogenesis in the region (Bascuñan, et al, 2019). The rocks are unconformably covered by Paleocene to Eocene (65-45 Ma, Figure 3) sedimentary successions of well-stratified orange and red sandstones intercalated with conglomerate beds (e.g., Arriagada et al, 2006;Dingman, 1963;Mpodozis et al, 2005) exposed along the westernmost part of the Salar de Atacama and Salar de Punta Negra basins (Figure 2b).…”

“…The large reverse faults exposed in this region have commonly been interpreted as east and west-dipping faults affecting the prerift basement rocks of ancient Mesozoic rift basins, which are well exposed in the neighboring ranges (e.g., Domeyko Cordillera, Figure 2b; Arriagada et al, 2006;Martínez et al, 2019Martínez et al, , 2020A. J. Tomlinson et al, 1999, among others).…”

“…These consist of moderate to high-angle faults created during Cenozoic times. Previous works (López et al, 2019(López et al, , 2020Martínez et al, 2018) argued that these resulted from the full reactivation of Mesozoic normal faults. For many years, the Pre-Andean basins were considered flexural basins whose subsidence was influenced by the tectonic uplift of crustal blocks along large reverse fault systems (Amilibia et al, 2008;Arriagada et al, 2006;Reutter et al, 1996); however, the kinematic of these structures have long been debated and two mechanisms (tectonic inversion accompanied of strike-slip motion and pure contraction) were proposed to explain their upward propagation.…”

“…Considering the vast extent of the study region and in order to simplify the stratigraphic description, we only use major chronological units in this study; the key details of each formation are summarized in Figure 3. Our description is based on previous studies (Amilibia et al, 2008;Arriagada et al, 2006;Bascuñán et al, 2015;González et al, 2015;Martínez et al, 2020;Mpodozis et al, 2005) and complemented with geological information obtained from the Toconao 1X borehole (Figures 2b and 3) located in the Salar de Atacama Basin. We divide the major geological units into Paleozoic, Mesozoic, and Cenozoic rocks, in order to simplify their stratigraphic position, and describe them in detail in the following subsections.…”

“…In general, there is a consensus that the basement-involved contractional structures result from the reactivation of previous zones of weakness in the upper crust (e.g., lineaments, regional-scale foliation, and suture zones) and/or previous brittle faults (R. W. H. Butler & Mazzoli, 2006;R. Butler et al, 2018;Carrera et al, 2006;Lacombe & Bellahsen, 2016;Martínez et al, 2020;Nemcok et al, 2009;Poblet & Lisle, 2011); however, in Andean-type orogens, these structures can also result from variations of the thermo-tectonic state of the lithosphere related to migration of volcanic arcs, whereby a hot crust is more prone to basement-involved deformation (Lacombe & Bellahsen, 2016). Recent regional studies using geophysical (gravity and seismic) and field data have highlighted the existence of complex basement-involved structures along the inner forearc of the Central Andes, which has been active since at least the Upper Cretaceous (Bascuñan et al, 2019;López et al, 2019;Martínez et al, 2020aMartínez et al, , 2020b.…”