Stratigraphic response to fragmentation of the Miocene Andean foreland basin, NW Argentina

Abstract

Foreland basins are sensitive recorders of spatiotemporal variations in tectonic and climatic forcing associated with an approaching orogenic front. Thus, analysis of foreland deposits and their associated deformation patterns and provenance signals allows assessment of tectonic and sedimentary processes during orogeny, providing clues to past environmental conditions. The Calchaquí region in the southern part of the northwest Argentinian Eastern Cordillera (ca. 25-26°S lat) structurally evolved from a contiguous Paleogene foreland of the Andes into a broken foreland and finally an intermontane basin landscape. This history is recorded in the sedimentary sequences of the Mio-Pliocene Angastaco and Palo Pintado Formations. We combine sedimentological methods, U-Pb zircon and K-Ar glass geochronology, clay mineralogy, and geochemical weathering indices with apatite fission track and (U-Th-Sm)/ He thermochronology, structural data, and fault modelling to document the stratigraphic response to the fluvial and tectonic processes that followed the formation of the broken foreland. Our observations suggest that fluvial systems in the Calchaquí region repeatedly changed their location and geometry. These fluvial systems were associated with pro-and retrograding gravel wedges that most likely formed in response to the structural growth of the Aguas de Castilla and Altos de Viñaco ranges that bound the basin to the east. A compartmentalisation of the foreland with restricted fluvial networks must have occurred by ca. 9 Ma. Our results demonstrate that the reconstruction of stratigraphic architectures constitutes a powerful means to better understand intrabasin tectonics and surface uplift in foreland basins.

Kinematic Evolution of the Santa Bárbara System in the Foreland of the Central Andes of Northwestern Argentina (26°S)

“…Onset of deformation and uplift of the Candelaria Range is well constrained by growth strata in the lower Jujuy Subgroup (∼9 Ma) flanking this range (Figure 5); this suggests a nearly simultaneous propagation of deformation at this latitude of the El Brete Range, which we infer to have started at ∼10 Ma, similar to the Metán Range (Hain et al, 2011). This appears to be a regional phenomenon, as mountain ranges in the northern Sierras Pampeanas and the southern Eastern Cordillera exhibit a similar timing of late Cenozoic uplift and deformation (Figures 6b, 7a, and 7b;Carrapa et al, 2011;Deeken et al, 2006;del Papa et al, 2021;Garcia et al, 2013;Hain et al, 2011;Löbens et al, 2013a;Mortimer et al, 2007;Payrola et al, 2020;Pearson et al, 2013;Pingel, Deeken, et al, 2023;Sobel & Strecker, 2003;Zapata et al, 2020). Subsequently, activity continued with slip along the Las Animas (1) and Las Iglesia (2) faults, followed by a major pulse of uplift associated with the El Brete Fault (3) (Figure 6b).…”

Tectonic Control on Drainage Evolution in Broken Forelands: Examples From NW Argentina

“…To the north, thermochronologic data from the Sierra de Cachi‐Palermo and growth strata at Lampasillos‐Aguada suggest these ranges were topographic highs by the mid‐late Miocene (Pearson et al., 2012; Vezzoli et al., 2012). Sediments derived from the Sierra de Metán, Sierra Ovejeria, and Sierra León Muerto and AHe data from the Sierra Mojotoro suggest active uplift by ∼10 Ma (Figure 7b; Del Papa et al., 2021; Galli et al., 2014; Hain et al., 2011; Pearson et al., 2013). Exhumation likely began at the eastern flank of Sierra Aconquija at ∼9 Ma and saline lakes to the east suggest the range had sufficient topography to disrupt E‐directed drainage from the proto‐El Cajón‐Santa María basin to Tucumán (Löbens et al., 2013; Zapata, Sobel, del Papa, Muruaga, & Zhou, 2019).…”

Cenozoic Exhumation and Deformation of the Intermontane Pastos Chicos Basin in the Southern Central Andes: Implications for the Tectonic Evolution of the Andean Plateau (Puna) and the Eastern Cordillera Between 23° and 24°S, NW Argentina

“…Including the studies listed above, many researchers have documented Eocene deformation throughout north-western Argentina and northern Chile with an area extending from approximately 22° to 27°S and from 69° to 65°W (Figure 8a, e.g., del Papa et al, 2013;Henríquez et al, 2020Henríquez et al, , 2022Montero-López et al, 2021;Payrola et al, 2020). A more comprehensive list of references used to determine the onset of deformation on a more regional scale (incl., Aramayo et al, 2017;del Papa et al, 2021;Hongn et al, 2011;Montero-López et al, 2017;Reiners et al, 2015;Reynolds et al, 2000;Vezzoli et al, 2012) is provided in Table S6 in Supporting Information S2 and a graphical representation of the data is shown in Figures 8 and 9.…”