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(Site 1 of paragraph V): Normal faults exposed in the El Salado valley, near El Salado village. Faults cut units of fine-grained sediments composed of alternating calcareous and clay layers. This site is located on the central fault of the AFS. See Fig. 2 for location.
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The large (≈10000 km2) and local-scale (300 m) sedimentary succession was deposited east of the AFS. The succession fills previously deep paleovalleys. And it consists of gravel, so-called “Atacama Gravels”, which passes laterally into fine-grained playa related deposits near the AFS. We interpret the deposition of this succession as a result of a...
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... El Salado river valley immediately 586 west of the El Salado village (Fig. 11). A major 587 tributary of the main valley follows this fault on the 588 southern side of the El Salado river valley. In this 589 tributary valley, 15 m of Neogene sediments com- 590 posed mainly of clay deposits alternating with thin 591 calcareous layers are exposed (Fig. 9). These deposits 592 grade upward into gravels. The basal fine-grained was active following gravel deposition (Fig. 11) (Fig. 12A). A second depositio- ...
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... Furthermore, understanding the intricate interaction between tectonic activity and landforms contributes to the identification and characterization of geological processes that shape the Earth's surface. By integrating various geoscientific disciplines such as geology, geophysics, and stratigraphy, researchers gain deeper insights into the evolution of landscapes and the underlying mechanisms driving their formation [30][31][32][33][34]. The available evidence strongly supports the assertion that tectonic geomorphology offers a comprehensive framework for comprehending the dynamic surface processes of the Earth. ...
Mediterranean basin exposed to ongoing processes of erosion and deformation. Neotectonics is the study of the geological processes involved in the deformation of the Earth’s crust. The topography of the terrain is greatly impacted by these neotectonic events, which has a considerable impact on the drainage pattern and general geomorphology of the region. In this work, the active tectonics were evaluated using the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) and several Geomorphic Indices in the Ain Zerga region of Northeast Algeria. Asymmetry factor, basin form, the ratio of valley floor width to valley height, the sinuosity of mountain fronts, hypsometric integral, hypsometric curve, and transverse topographic symmetry factor were some of the indices used. These findings emphasize the tremendous tectonic activity that exists in the study area. In comparison to sub-watershed N°2, sub-watersheds N°1, N°3, and N°4 had stronger tectonic activity, according to the examination of these geomorphic indicators. The Relative Tectonic Activity Index (Iat) distribution pattern, which concurred with other pieces of information such as stream deflection and lineament analysis, corroborated these conclusions. We were able to learn a lot about the different levels of tectonic activity in the sub-watersheds by using traditional geomorphic indices. The tectonic activity-exhibiting basins consistently displayed connections with structural disturbances, basin geometry, and field research. Geomorphic indices and morphometric characteristics were used to identify tectonically active zones in a portion of the Mellegue transboundary basin, which shows a considerable influence of neotectonic activity in a portion of the Neogene basin.
... SCCP: Sierra Checos del Cobre Peneplain (Bissig and Riquelme, 2010). CS: Cumbre surface (Mortimer, 1973 (Riquelme et al., 2003(Riquelme et al., , 2007. Regarding the geomorphological setting, the Sierra Checos del Cobre Peneplain (SCCP in Fig. 3) is the oldest and highest surface identified in the Salado Canyon watershed Riquelme, 2009, 2010). ...
... In the headwater of the Rio de la Sal Canyon (Fig. 4), thin (~ 5 m thick) alluvial deposits related to the Asientos Pediplain are time-constrained by interbedded tuff layers between 17.45 ± 0.26 Ma and 9.16 ± 0.08 Ma (40Ar/39Ar sanidine, Bissig and Riquelme, 2009). From the axis of the Precordillera to the west, deeply incised drainage systems (up to 2000 m of vertical incision) cut into the bedrock in response to the uplift of the Precordillera during the Eocene to Oligocene Incaic deformation event (e.g., Riquelme et al., 2003Riquelme et al., , 2007Nalpas et al., 2008;Cornejo et al., 2013;Martínez et al., 2019). In the Central Depression and western Precordillera, these deeply incised drainage systems were subsequently filled with up to ~450 m of continental clastic sediments, referred to as the Atacama Gravels ( Fig. 3B; Sillitoe et al., 1968). ...
... The western border of the Central Depression exposes playa lake sedimentary facies that can be followed to the west forming aggradation fluvial terraces along the Salado Canyon up to the Atacama Fault, in the axis of the Coastal Cordillera. The playa lake deposition has been explained by the activity of the Atacama Fault, which accommodates the relative uplift of the western Coastal Cordillera (Riquelme et al., 2003(Riquelme et al., , 2007 before ~5.97 Ma (Nalpas et al., 2008). This fault activity may have blocked the drainage to the Pacific Ocean. ...
Pediplains are classically identified as flat landscape surfaces in arid regions linked to tectonic quiescence, whereas deep incision of a pediplain is attributed to tectonic uplift. In the Atacama Desert, pediplains are generally used as morphotectonic markers to define the chronology of episodes of Late Cenozoic Andean uplift from their erosion and incision patterns and timings. The Atacama Pediplain (AP) extends over >12,000 km² (26° to 28°S Lat) through the Central Depression and Precordillera of the southern Atacama Desert. In this study we perform geomorphologic and stratigraphic observations on the AP in the Salado Canyon area, combining new geochronological results derived from ⁴⁰Ar/³⁹Ar biotite ages from volcanic layers interbedded within the alluvial deposits, and ²¹Ne exposure ages on quartz-clasts on alluvial plains, to determine the chronology of the AP evolution. Results show that the evolution of the AP is a long-term and continuous process (from >20 to ~2.3 Ma) of alluvial deposition and subsequent alluvial plain formation developed by interplay between the climate variability of the Atacama Desert and Andean uplift. The AP alluvial deposition occurred in two spatially and temporally separated episodes of alluvial backfilling: 1) shortly before ~20.14 Ma and to prior to ~9.4 Ma, a timespan that allows for the drainage capture of the eastern Precordillera, and considerable landscape rearrangement; 2) post ~9.4 Ma, with a re-positioning of alluvial backfilling from the Precordillera towards the Central Depression. This occurs after the Mid Miocene onset of the hyperarid conditions in the Central Depression and is more likely due to late Miocene surface uplift. Exposure ages reveal the cessation of basin-scale deposition and the abandonment of the alluvial plains during ~5.24 to ~3.8 Ma linked to the incision of Salado Canyon. Subsequent climate conditions modulated the surfaces by the development of lag deposits until ~2.69 to ~2.3 Ma when hyperarid conditions reach a threshold that limits surficial activity. Additionally, the drainage capture of the Precordillera by headwards erosion of the Salado Canyon explains marked deep incision depth of this canyon without the need for an increase in surface uplift or a change in climate conditions. The AP is not a general marker of a single climatic or tectonic event/period but a composite paleosurface formed by a complex concatenation of extrinsic and intrinsic geomorphic processes over more than ~17 myr.
... However, the imprint of neotectonics is frequently obscured in low-relief environments by the sedimentary cover, hampering identification of the origin of different landforms (Ruszkiczay-Rüdiger et al., 2009). Tectonically influenced landscapes are usually identified by a series of geomorphological indicators, such as entrenched channels, a high degree of incision along the channels flowing across active faults, or a sudden change in channel morphology (e.g., Rhea, 1993;Schumm et al., 2002;Bishop et al., 2003;Riquelme et al., 2003;Silva et al., 2003). The Chobe Enclave, situated in northern Botswana, is bounded by the Chobe and Linyanti faults and has a generally flat topography ( Fig. 1a-d). ...
The imprint of neotectonics is frequently obscured in low-relief environments by the sedimentary cover. This is the case in the Chobe Enclave, part of a pristine region of the Middle Kalahari Basin in northern Botswana, where numerous fossil landforms, such as sand dunes, pans, sand ridges, and carbonate islands, can be observed but whose detailed origins are unclear. In this study, a combination of near-surface geophysical surveys, sedimentological analysis, and optically-stimulated luminescence (OSL) dating were used to study the relationship between landscape development and neotectonic activity in one region of the Chobe Enclave. Specifically, electrical resistivity tomography (ERT) and ground penetrating radar (GPR) surveys were used to define the lateral and vertical distribution of sedimentary deposits associated with a prominent sand ridge and its margins. Sedimentological analysis and OSL dating of soil samples from pits taken along the survey lines were then used to calibrate the geophysical results and establish a chronostratigraphical framework. Our results lead to the following hypotheses regarding the evolution of this part of the Chobe landscape: (i) during the Late Pleistocene (>~25 ka), fluvial channels were buried due to epeirogenic movements, resulting in paleo-channels; (ii) between ~25 ka and ~6 ka, a paleo-lake shoreline formed, which resulted in the linear eastern margin observed on the considered sand ridge. Erosional bounding surfaces suggest the syndepositional uplift of the sand ridge morphologies during this time; (iii) a neotectonic influence on the evolution of the landscape is revealed by the incision of the sand ridge forming fluvial watergaps since ~6 ka ago; and (iv) due to continuous aeolian and fluvial reworking, the western-most ridge became gradually isolated from the floodplain resulting in an inherited relief. In conclusion, this investigation allowed the deformation caused by epeirogenic movements acting on a low relief landscape to be characterized in terms of landforms and sedimentary body properties.
... The Southern Central Andes comprise, in its northern sector (22°-27°S): (i) the Coastal Range, which mainly includes Jurassic to Cretaceous magmatic arcs and associated sedimentary basins (Reutter et al., 1996;Riquelme et al., 2003;Oliveros et al., 2006); (ii) the Chilean Precordillera, or Domeyko Range, corresponding to the Late Cretaceous to Eocene magmatic arc, developed over a Devonian to Triassic basement (Coira et al., 1982;Amilibia et al., 2008;Mpodozis and Cornejo, 2012); (iii) the Western Cordillera, with the Miocene to Holocene magmatic arc (De Silva et al., 2006;Kay and Coira, 2009); (iv) the internallydrained Altiplano/Puna plateau, with an average elevation of 4000 m (Isacks, 1988;Allmendinger et al., 1997); (v) the doubly vergent thrust belt of the Eastern Cordillera, which uplifts late Proterozoic to Paleo-zoic metasedimentary and sedimentary rocks Reutter et al., 1994;Kley and Monaldi, 2002;Hongn et al., 2010), (vi) the active eastward-tapering sedimentary wedge of Paleozoic to Neogene rocks of the Sub-Andean fold-and-thrust belt, north of 24°S, and the Santa Bárbara basement-involved fault system, south of 24°S (Mingramm et al., 1979;Allmendinger et al., 1983;Roeder, 1988;Sheffels, 1990;Baby et al., 1992Baby et al., , 1995Dunn et al., 1995;Kley and Reinhardt, 1994;McQuarrie, 2002); and, (vii) the foreland basin, filled with wedge-shaped Neogene clastic strata of up to 6 km of thickness, known as the Chaco Plains (Uba et al., 2005(Uba et al., , 2006. This basin is underlayed by the Brazilian craton, which has been a stable nucleus of South America since the Proterozoic (Litherland et al., 1985). ...
As the archetype of mountain building in subduction zones, the Central Andes has constituted an excellent example for investigating mountain-building processes for decades, but the mechanism by which orogenic growth occurs remains debated. In this study we investigate the Southern Central Andes, between 22° and 35°S, by examining the along-strike variations in Cenozoic uplift history (<45 Ma) and the amount of tectonic shortening-thickening, allowing us to construct seven continental-scale cross-sections that are constrained by a new thermomechanical model. Our goal is to reconcile the kinematic model explaining crustal shortening-thickening and deformation with the geological constraints of this subduction-related orogen. To achieve this goal a representation of the thermomechanical structure of the orogen is constructed, and the results are applied to constrain the main decollement active for the last 15 Myr. Afterwards, the structural evolution of each transect is kinematically reconstructed through forward modeling, and the proposed deformation evolution is analyzed from a geodynamic perspective through the development of a numerical 2D geodynamic model of upper-plate lithospheric shortening.
In this model, low-strength zones at upper-mid crustal levels are proposed to act both as large decollements that are sequentially activated toward the foreland and as regions that concentrate most of the orogenic deformation. As the orogen evolves, crustal thickening and heating lead to the vanishing of the sharp contrast between low- and high-strength layers. Therefore, a new decollement develops towards the foreland, concentrating crustal shortening, uplift and exhumation and, in most cases, focusing shallow crustal seismicity. The north-south decrease in shortening, from 325 km at 22°S to 46 km at 35°S, and the cumulated orogenic crustal thicknesses and width are both explained by transitional stages of crustal thickening: from pre-wedge, to wedge, to paired-wedge and, finally, to plateau stages.
... However, the imprint of neotectonics is frequently obscured in low-relief environments by the sedimentary cover, hampering identification of the origin of different landforms (Ruszkiczay-Rüdiger et al., 2009). Tectonically influenced landscapes are usually identified by a series of geomorphological indicators, such as entrenched channels, a high degree of incision along the channels flowing across active faults, or a sudden change in channel morphology (e.g., Rhea, 1993;Schumm et al., 2002;Bishop et al., 2003;Riquelme et al., 2003;Silva et al., 2003). The Chobe Enclave, situated in northern Botswana, is bounded by the Chobe and Linyanti faults and has a generally flat topography ( Fig. 1a-d). ...
... Topographic swath profiles are constructed by projecting equally spaced topographic profiles within a strip or swath of 200 m (Baulig, 1926;Tricart & Cailleux, 1958;D'Agostino et al., 2001;Fielding et al., 1994). These profiles provide a general view of the topographic pattern of the carbonates deposits and have been widely used to characterize regional-scale morphology (D'Agostino et al., 2001;Riquelme et al., 2003;Grohmann, 2005;Molin et al., 2004Molin et al., , 2012Scotti et al., 2014;Azañón et al., 2015). The GE imagery allows studying the architecture of the upper Lithothamnium unit and its relation with the lower bioclastic unit previously deposited. ...
The Messinian (Upper Miocene) is characterized at the level of its marginal basins by the development of numerous carbonate platforms. This study concerns the Messinian platform of the Boukadir region in the south of the Chelif Basin in Algeria. It is composed of a lower prograding rimmed platform and an upper aggradational homoclinal ramp resting upon the Tortonian–Lower Messinian Blue Marl Formation, and its thickness reaches ~280 m in the Chelif Basin. The upper red-algae unit is uniform and subhorizontal with a minimum thickness of 90 m. Petrographic analysis of the upper ramp reveals three different microfacies, characterized by Lithothamnium, foraminifera, high porosity, and a microsparitic matrix. MF1 is a packstone, MF2 a packstone/bindstone deposited above the fair-weather wave base and MF3 is a wackestone to packstone deposited below this level. The upper unit is made up entirely of autochthonous biogenic elements without significant external fluvial contribution. It was formed in a shallow marine environment, with very high productivity and a significant export of the sediments produced. This aggradation was followed by a rapid exhumation (regression) transforming all the aragonite into calcite. The platforms correspond to the T2 complex reef formation (6.7–5.95 Ma) documented on the other Messinian carbonate platforms in the South of the Alboran Sea that formed just before the Messinian Salinity Crisis.
... Furthermore, the highest values of standard deviation are observed at profile distance >6.1 km (Figure 8b). The standard deviation of the altitude reflects variations in the amount of fluvial incision; higher values indicate a more deeply incised valley floor (e.g., Riquelme et al., 2002). ...
We present insights into the Cenozoic tectonic evolution of the region around the Pontarlier strike‐slip fault zone within the Jura fold‐and‐thrust belt by combined study of paleostress and geomorphic analyses. A preliminary separation of heterogeneous fault‐slip data and bedding‐tilt correction was performed before determining the paleostress axes orientations. The paleostress results provide evidence of multiphase deformation history consisting of four successive events. These events include a strike‐slip stress regime with ∼N‐S directed compression, a NW‐SE directed extensional stress regime, a NW‐SE trending compressional stress regime, and a strike‐slip stress regime with a mean NW‐SE directed compression. The directions of extension and compression for the second and third events are consistent with the general direction of maximum horizontal far‐field stress near the northern segment of the Pontarlier fault and generally deviate from those found near the southern segment.
Geomorphic analysis of selected rivers along the southern segment of the Pontarlier fault, together with sub/surface geological observations provides new clues on Late Cenozoic strike‐slip reactivation of inherited extensional structure of Mesozoic age. These clues include (i) anomalous zones of high gradient within uniform bedrock lithology that spatially coincide with an obvious change in the depth to top Mesozoic layers; and (ii) right‐lateral offset of river channels, which is consistent with NW‐SE compression related to the youngest paleostress and current stress field. A combination of paleostress and geomorphic analyses provides a useful complementary approach for unraveling the Cenozoic tectonic evolution of the region characterized by a general lack of outcrop of Cenozoic rocks.
... The analysis was performed for a source elevation of 2200 m, similar to the current mining pit elevation. Nevertheless, it is possible that the source elevation above sea-level was different at the time of deposition, in that it was either higher because the relief had decreased or lower because this region may have been uplifted since then (e.g., Riquelme et al., 2003;Jordan et al., 2014) since then. A <1000 m difference in the elevation results in a <50% difference in the production rates. ...
Increasing evidence suggests that supergene exotic copper deposits were emplaced during periods of geomorphic quiescence and pulses of humidity in arid environments. We tested this idea in the Centinela Mining District in the Atacama Desert (northern Chile). We collected 14 sand samples at depth (up to 110 m) in two open‐pit mines (Central Tesoro and Mirador) exposing Miocene sediment, and located in the El Tesoro Basin, which hosts two exotic copper‐rich orebodies. We inverted the 10Be and 21Ne concentrations by using a two‐box model (IMIS, Inversion of Multi Isotopes in a Sedimentary basin) composed of an eroding source of sediment and a depositional sedimentary basin, and by selecting denudation and sedimentation rate histories that can explain our data. The ages found demonstrate that the two exotic orebodies were deposited during a narrow period between 14 Ma (10 Ma younger than previously thought) and 9.5 Ma, when an ignimbrite covered the sedimentary sequence. The dated lower exotic copper orebody was deposited during or just before a sharp decrease in the sedimentation rates (from >100 to 0.5‐5 m/Ma), which is consistent with published sedimentological and carbonate isotopic data in this district. This confirms the idea that exotic deposits form during a quiescence of the geomorphic activity. Nevertheless, our model suggests that the back‐ground denudation rate providing sediment to these basins between ~14 Ma and ~9.5 Ma was surprisingly high (>250 m/Ma) for such an arid environment. These denudation rates can be explained by a relatively rapid local back‐scarp retreat providing most of the sediment to these basins and possibly a wetter climate compared to the present. Then, during the period 10‐7 Ma, the denudation rates decreased to >50 m/Ma. This decrease may correspond to a local progressive decrease in the slope of the surrounding hills, or to a progressive aridification, or a combination of both phenomena.
... The analysis was performed for a source elevation of 2200 m, similar to the current mining pit elevation. Nevertheless, it is possible that the source elevation above sea-level was different at the time of deposition, in that it was either higher because the relief had decreased or lower because this region may have been uplifted since then (e.g., Riquelme et al., 2003;Jordan et al., 2014) since then. A <1000 m difference in the elevation results in a <50% difference in the production rates. ...
Increasing evidence suggests that supergene exotic copper deposits were emplaced during periods of geomorphic quiescence and pulses of humidity in arid environments. We tested this idea in the Centinela Mining District in the Atacama Desert (northern Chile). We collected 14 sand samples at depth (up to 110 m) in two open-pit mines (Central Tesoro and Mirador) exposing Miocene sediment, and located in the El Tesoro Basin, which hosts two exotic copper-rich orebodies. We inverted the 10 Be and 21 Ne concentrations by using a two-box model (IMIS, Inversion of Multi Isotopes in a Sedimentary basin) composed of an eroding source of sediment and a depositional sedimentary basin, and by selecting denudation and sedimentation rate histories that can explain our data. The ages found demonstrate that the two exotic orebodies were deposited during a narrow period between 14 Ma (10 Ma younger than previously thought) and 9.5 Ma, when an ignimbrite covered the sedimentary sequence. The dated lower exotic copper orebody was deposited during or just before a sharp decrease in the sedimentation rates (from >100 to 0.5-5 m/Ma), which is consistent with published sedimentological and carbonate isotopic data in this district. This confirms the idea that exotic deposits form during a quiescence of the geomorphic activity. Nevertheless, our model suggests that the background denudation rate providing sediment to these basins between ~14 Ma and ~9.5 Ma was surprisingly high (>250 m/Ma) for such an arid environment. These denudation rates can be explained by a relatively rapid local back-scarp retreat providing most of the sediment to these basins and possibly a wetter climate compared to the present. Then, during the period 10-7 Ma, the denudation rates decreased to >50 m/Ma. This decrease may correspond to a local progressive decrease in the slope of the surrounding hills, or to a progressive aridification, or a combination of both phenomena.
... La unidad Gravas de Atacama es la de mayor extensión y presenta en su superficie el desarrollo del denominado Pedimento de Atacama, coetáneo al desarrollo del Pedimento de Tarapacá hacia el norte (Marquardt et al., 2000;Riquelme et al., 2003Riquelme et al., , 2007. Este pedimento está cubierto por la Ignimbrita San Andrés (Clark et al., 1967), a partir de la cual se estima el término de la depositación sobre este pedimento entre los 10 y 8 Ma., al inicio del Mioceno tardío. ...
The present thesis develops a geodiversity sites inventory process within Copiapó and Caldera communes, from which arise descriptives sheets of the selected sites, thematic tours and educatives and touristic resources. This proposals pretends to promote a correct local management of geoheritage and the enhacement of the sites among the community, in particular students and tourists, because nowadays are exposed to hazards and deficiencies in its conservation strategies.
Inventory enabled to identify nine geologic contexts in the study zone, with seven in common between Copiapó and Caldera communes. Included in this contexts, thirty sites with recognized or potential geoheritage elements were pre-selected and evaluated qualitative and quantitavely, in order to discriminate those with sufficient educational and/or touristic values and without limitations based on their conservartion status, accesibility or hazards. Final selection considered fifteen sites, six in Copiapó and nine in Caldera, whereas twelve were not selected and three remained pending for further works. Descriptives sheets were created to the selected sites, with useful information and figures to access to each one, understand its relevants geological elements and associate them to others values of surrounding areas. Based on this, two tours were made, the “Ruta por el Río Copiapó” and “Ruta por el Borde costero”. To achieve the correct application and scope to different ages and capabilities people, educational and touristic resources were proposed to promote formal and equable management strategies related to the recognized sites. This results improve the knowledgement of the local geodiversity, contribute to the conservation of its natural resources and promote to cultural and economic benefits for their inhabitants and visitors.
