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1. Major geologic provinces of the southern central Andes superposed on shaded relief map derived from Shuttle Radar Topography Mission (SRTM). Boundaries of geologic provinces modified after Jordan et al. (1983)
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The history of the Puna Plateau and its marginal basins and ranges in the Eastern Cordillera and the northern Sierras Pampeanas
structural provinces in northwestern Argentina impressively documents the effects of tectonics and topography on atmospheric
circulation patterns, the successive evolution of orographic barriers, as well as their influence...
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The Early Precambrian granulite-gneiss complexes (GGC) of the East European craton (EEC) take their part in extensive areals of the intracontinental magmatism, sedimentary basins and high-temperature metamorphism (Fig. 1 and 2). In this paper the EEC area is considered, the Ukrainian Shield excluding.
Mesoarchean. Granulite-facies metamorphism with...
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... The Puna region is characterized by sedimentary basins with thick sequences of continental evaporites (water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution), developed during the Miocene epoch to recent periods, intercalated with late Eocene to Holocene clastic deposits (Alonso et al., 2006;Kraemer et al., 1999). The endorheic drainage of these basins, combined with an arid to semiarid climate and interior drainage, has resulted in the formation of lacustrine environments such as salt lakes and wetlands (Alonso & Rojas, 2020). ...
... This basin is characterized by a basement composed of Precambrian metamorphic rocks and Paleozoic plutonic and sedimentary rocks, which are overlain by Cretaceous and Paleogene sediments. Followed in the stratigraphic sequence by thick sequences of continental evaporites formed during the Miocene epoch to recent periods, unconformably overlie by late Eocene-Miocene clastic deposits (Alonso et al., 2006;Kraemer et al., 1999). Salar de Antofalla is approximately 140 km long and between 4 and 10 km wide (Voss, 2002). ...
Laguna Verde's dome‐shaped structures are distinctive formations within the Central Andes, displaying unique geomicrobiological features. This study represents a pioneering investigation into these structures, assessing their formation, associated taxa, and ecological significance. Through a multifaceted approach that includes chemical analysis of the water body, multiscale characterization of the domes, and analysis of the associated microorganisms, we reveal the complex interplay between geology and biology in this extreme environment. The lake's alkaline waters that are rich in dissolved cations and anions such as chloride, sodium sulfate, and potassium, coupled with its location at the margin of the Antofalla salt flat, fed by alluvial fans and hydrothermal input, provide favorable conditions for mineral precipitation and support for the microorganism's activity. Laguna Verde's dome‐shaped structures are mainly composed of gypsum and halite, displaying an internal heterogeneous mesostructure consisting of three zones: microcrystalline , organic (orange and green layers), and crystalline . The green layer of the organic zone is predominantly composed of Proteobacteria, Bacteroidetes, and Cyanobacteria, while the orange layer is mostly inhabited by Cyanobacteria. The results of the study suggest that oxygenic photosynthesis performed by Cyanobacteria is the main carbon fixation pathway in the microbial community, supported by carbon isotopic ratios of specific biomarkers. This finding highlights the important role played by Cyanobacteria in this ecosystem.
... The Puna region is characterized by sedimentary basins with thick sequences of continental evaporites (watersoluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution), developed during the Miocene epoch to recent periods, intercalated with late Eocene to Holocene clastic deposits (Kraemer et al. , 1999;Alonso et al. , 2006). The endorheic drainage of these basins, combined with an arid to semiarid climate and interior drainage, has resulted in the formation of lacustrine environments such as salt lakes and wetlands (Alonso and Rojas, 2020). ...
Laguna Verde~̵́s dome-shaped structures represent one of the most important Andean Microbial Ecosystems (AMEs) reported in the Central Andes. To date, this system lacks any kind of geomicrobiological research, so the following article represents the first study of these dome-shaped structures and their associated taxa. For this purpose, a chemical analysis of the water body, multiscale characterization of the domes, and analysis of the associated microorganisms were carried out. The lake’s alkaline waters rich in various minerals and its location at the margin of the Antofalla salt flat, fed by alluvial fans and hydrothermal input, provide favorable conditions for mineral precipitation and support for microorganism’s activity. Laguna Verde´s dome-shaped structures show an internal heterogeneous mesostructure composed of three zones: microcrystalline, organic (orange and green layers) and crystalline. The green layer of the organic zone is predominantly composed of Proteobacteria, Bacteroidetes, and Cyanobacteria, while the orange layer is mostly inhabited by Cyanobacteria. The results of the study suggest that oxygenic photosynthesis performed by Cyanobacteria is the main carbon fixation pathway in the microbial community, supported by carbon isotopic ratios of specific biomarkers. This finding highlights the important role that Cyanobacteria play in this ecosystem.
... The harsh climatic conditions prevailing in the Puna are mostly attributed to the Neogene uplift of the Andean Cordillera, which blocks the easterly humid winds, casting a shadow of dryness on the leeward [8][9][10]. However, the reconstructed climates from the Paleogene are remarkably different from those of today; during the Paleocene and early Eocene, sedimentological information (e.g., clay minerals and paleosols) from the Salta Group, in Northwestern Argentina, indicate humid-subtropical to tropical climates, although episodes of seasonality have been identified [11][12][13][14]. ...
The southern Central Andes-or Puna-now contains specialized plant communities adapted to life in extreme environments. During the middle Eocene (~40 Ma), the Cordillera at these latitudes was barely uplifted and global climates were much warmer than today. No fossil plant remains have been discovered so far from this age in the Puna region to attest to past scenarios. Yet, we assume that the vegetation cover must have been very different from what it looks today. To test this hypothesis, we study a spore-pollen record from the mid Eocene Casa Grande Formation (Jujuy, northwestern Argentina). Although sampling is preliminary, we found ~70 morphotypes of spores, pollen grains and other palynomorphs, many of which were produced by taxa with tropical or subtropical modern distributions (e.g., Arecaceae, Ulmaceae Phyllostylon, Malvaceae Bombacoideae). Our reconstructed scenario implies the existence of a vegetated pond surrounded by trees, vines, and palms. We also report the northernmost records of a few unequivocal Gondwanan taxa (e.g., Nothofagus, Microcachrys), about 5,000 km north from their Patagonian-Antarctic hotspot. With few exceptions, the discovered taxa-both Neotropical and Gondwanan-became extinct from the region following the severe effects of the Andean uplift and the climate deterioration during the Neogene. We found no evidence for enhanced aridity nor cool conditions in the southern Central Andes at mid Eocene times. Instead, the overall assemblage represents a frost-free and humid to seasonally-dry ecosystem that prevailed near a lacustrine environment, in agreement with previous paleoenvironmental studies. Our reconstruction adds a further biotic component to the previously reported record of mammals.
... Northwards from this point occurs the transition between the Subandean sierras and the Eastern Cordillera domains, marked by changes in the topography and vegetation. The Eastern Cordillera corresponds to a orographic barrier to the moisture coming from eastern South America, that causes a higher precipitation frequency in the Subandean/Interandean zones (Alonso et al., 2006;Schildgen & Hoke, 2018), which favour the development of a denser vegetation in the region. Across the road from the Mirador crops out the Puncoviscana Fm, composed here by brown phyllites overlain in an angular unconformity by coarse Quaternary deposits. ...
This guide presents seven itineraries to investigate the geology of the Central Andes, which can be done in seven days of field work along main roads in northern Argentina and Chile. A total of 32 field stops are organized in a complete cross-section that cuts over 600 km of the mountain range, from the Subandean Zone and Eastern Cordillera, between latitudes 24°–23° 20ʹ (Purmamarca–Quebrada de Humahuaca), to the Coastal Cordillera, between latitudes 22° 10ʹ–20° 17ʹ (Tocopilla–Iquique), passing through the domains of North Puna, Western Cordillera, Modern Volcanic Arc, Cordillera de la Sal and Cordillera Domeyko. The proposed transect exhibits diverse structural, morphotectonic, stratigraphic, volcanic and sedimentary features of the magnificent Andean mountain range, which is the main example of a non-collisional orogen in the world. The geological features mentioned in this guide are widely documented and contextualized here according to recent bibliography. The stops were selected from a broader field trip guide, part of the Geology of the Central Andes course, held during four years by the Geosciences Institute of the Federal University of Rio Grande do Sul (BR), with groups with up to 50 people, so that the feasibility of the route with large bus was properly tested and is assured. Additionally, travel logistics tips, based on our experience, are provided along this guide.KeywordsOrogenyAccretionary orogenField trip guideCentral AndesNorthern ArgentinaNorthern Chile
... The central Andean uplift since the Late Miocene was followed by a gradual passage from aridity to hyper aridity in the Atacama Desert (Armijo et al., 2015;Hoorn et al., 2022). Intensified aridity conditions were recorded in the Pliocene when the climate became drier in southern South America due to the slow rise of the Andean chain and the cold Humboldt Current (Alonso et al., 2006). The uplift of Andes at 14-11 Ma is strongly linked to the onset of grassland open formations in eastern Andes (Pascual et al., 1996;Donato et al., 2003;Ortiz-Jaureguizar and Cladera, 2006), which also promoted the diversification of grass-adapted taxa (Ceccarelli et al., 2019 and references therein). ...
Aridity conditions and expansion of arid biomes in South America are closely linked to the onset of Andean orogeny since at least 30 Mya. Among arid-associated taxa, spiders belonging to the genus Petrichus are found along the Andes mountains and across the diagonal of open formations of the Chaco and Cerrado domains. In this contribution, we asked whether Petrichus originated prior to the central Andean uplift and what historical processes have promoted their diversification. We time-calibrated the phylogenetic tree of Philodromidae and estimated the divergence times of Petrichus. Considering phylogenetic uncertainty, we assessed biogeographical hypotheses of the historical events associated with the diversification of these spiders in South America. Petrichus originated along the Pacific coastal deserts in the Central Andes during the Early Miocene. The species likely dispersed from the western to the eastern side of the Andes coincidently with the central Andean uplift. The diversification of these spiders is coeval with the expansion of open grassland formations during the Late Miocene and Early Pliocene. Multiple dispersal events occurred from the Monte desert to southern South America and eastward to Chaco between ∼8 and 2.5 Mya. The Andes might have played a role as a corridor favoring geographical range expansions and colonization of new environments. In addition, we also suggest that Philodromidae might have an Oligocene origin or earlier. Future analyses based on further evidence and larger taxon sampling should be carried out to corroborate our findings.
... Since late Pleistocene until present, the Central Andean region had experience climatic fluctuations during short periods of time (Abbott et al., 2003;Alonso et al., 2006;Strecker et al., 2007). The sedimentary record of Central Andes endorheic lacustrine systems is an excellent indicator of these climatic fluctuations (Abbot et al., 1997;Grosjean, 1994;Valero-Garcés et al., 2000). ...
... This region is characterized by a steep local relief, caused by contractional 'basins and ridges' and volcanoes (Kraemer et al., 1999) (Figure 1). In addition to this, an arid to semi-arid climate with endorheic watersheds allows the formation of evaporation environments such as lakes, salt plains and wetlands (Alonso et al., 2006;Alonso & Rojas, 2020;Jordan & Mpodozis, 2006). Throughout its extension, the Puna region presents a diversity of basins composed by continentalevaporitic Pleistocene deposits, in addition to volcanic and clastic deposits (Alonso et al., 1991;Alonso & Rojas, 2020;Strecker et al., 2007) (Figure 1). ...
... From the late Pleistocene to the present, the Puna region underwent varied climatic fluctuations in short periods of time caused by orbital eccentricity, glaciations/deglaciations, El Niño Southern Oscillation (ENSO), among other climatological factors (Abbott et al., 2003;Alonso et al., 2006;Strecker et al., 2007). Due to the complex topography and internal drainage networks, climatic fluctuations are regionally controlled (Alonso et al., 2006;Strecker et al., 2007) and are well recorded in the sedimentary sequence of lakes and lagoons (Abbott et al., 2003;Alonso et al., 2006). ...
The study of microbialites development is a key tool to understand environmental pathways during deposition. We provide a detailed analysis of modern Central Andean microbialites from high‐altitude lakes. The stratigraphic record of Turquesa Lake shows a significant short‐term recolonization by microbialite‐producing microorganisms during environmental stress. Far from a crisis paradigm, the coasts and paleocoasts of Turquesa lake exhibit three microbialitic buildups formed along different stages, providing a good study case of biological resilience of these systems in harsh environments. The MI and MII microbialite buildups occupied two paleocoasts. Both are composed of oncoids with micritic to microsparitic textures. Morphological, textural and mineralogical similarities between the two buildups suggest that they were formed at different times, but under very similar environmental conditions. The microorganisms that produced the microbialitic buildup MIII are currently colonizing the coast of this lake. The previous oncoid morphology change to a parallel micritic–spartic lamination. This remarkable changes in the microstructure can be explained by an important environmental change caused by the isolation of the Peinado Lake, and a subsequently microorganism adaptation. This microbialite structures can be proposed as an interesting modern analogue for environmental changes along the geological record.
... Puna (in Argentina) and Altiplano (in Bolivia) are an elevated region rising to an average of 3,700 m.a.s.l., characterized by a steep local relief caused by contractional "basins and ranges, volcanoes, and sluggish erosion due to an arid climate (Kraemer et al., 1999). Puna region exhibits sedimentary basins with thick sequences of Miocene to recent in age continental evaporates, unconformably overlying Late Eocene to Miocene clastic deposits (Kraemer et al., 1999;Alonso et al., 2006). The endoreic drainage of their basins, added to an arid-to-semiarid climate, allows the formation of lacustrine evaporites environments resulting in salt flats (Jordan and Mpodozis, 2006). ...
Modern microbialites in Argentina’s Puna (Central Andes) are considered a reliable tool for understanding the evolution of early life on our planet and developing strategies for detecting life on Mars. The morphological, structural and geochemical variations in these deposits, together with their distribution and architecture, are some of the most important parameters for understanding and characterising them. However, the lack of appropriate cartography and/or the high price to access it, added to the complex geological and geomorphological context in this region, complicate a traditional mapping on a good scale of detail. This paper presents a GIS-based methodology for a detailed mapping and architectural modeling of Las Quínoas microbialitic deposit (Holocene). To meet this objective, the geoprocessing of the information obtained from drone surveys, fieldwork and laboratory work, is carried out using ArcGIS software. The result is a high-resolution reconstruction of the deposit architecture, together with several thematic maps that represent the variation of the morphological, structural and geochemical characteristics of the oncoids (microbialites) with respect to depth and their position in the water body. From an integral point of view, this work provides a new methodological approach for microbialites mapping and improves the survey strategies in Central Andes.
... The central Andean uplift since the Late Miocene was followed by a gradual passage from aridity to hyper aridity in the Atacama Desert (Armijo et al., 2015;Hoorn et al., 2022). Intensified aridity conditions were recorded in the Pliocene when the climate became drier in southern South America due to the slow rise of the Andean chain and the cold Humboldt Current (Alonso et al., 2006). The uplift of Andes at 14-11 Ma is strongly linked to the onset of grassland open formations in eastern Andes (Pascual et al., 1996;Donato et al., 2003;Ortiz-Jaureguizar and Cladera, 2006), which also promoted the diversification of grass-adapted taxa (Ceccarelli et al., 2019 and references therein). ...
... Evaporites are sediments formed by physicochemical precipitation of brines [78]. In endorheic basins of the Central Andes region, salt flats are common Quaternary evaporitic deposits [79][80][81] [80,[82][83][84][85]. However, depending on the location of the salt flat, the dominant mineralogical facies can vary between lacustrine carbonate facies, halite facies, boratiferous facies, and gypsum-boratiferous facies [79,80]. ...
... In endorheic basins of the Central Andes region, salt flats are common Quaternary evaporitic deposits [79][80][81] [80,[82][83][84][85]. However, depending on the location of the salt flat, the dominant mineralogical facies can vary between lacustrine carbonate facies, halite facies, boratiferous facies, and gypsum-boratiferous facies [79,80]. In these salt flats, the dominant AMEs are gypsum evaporitic microbial ecosystems (GEMEs) [13,14,[86][87][88]. ...
The wetlands and salt flats of the Central Andes region are unique extreme environments as they are located in high-altitude saline deserts, largely influenced by volcanic activity. Environmental factors, such as ultraviolet (UV) radiation, arsenic content, high salinity, low dissolved oxygen content, extreme daily temperature fluctuation, and oligotrophic conditions, resemble the early Earth and potentially extraterrestrial conditions. The discovery of modern microbialites and microbial mats in the Central Andes during the past decade has increased the interest in this area as an early Earth analog. In this work, we review the current state of knowledge of Central Andes region environments found within lakes, small ponds or puquios, and salt flats of Argentina, Chile, and Bolivia, many of them harboring a diverse range of microbial communities that we have termed Andean Microbial Ecosystems (AMEs). We have integrated the data recovered from all the known AMEs and compared their biogeochemistry and microbial diversity to achieve a better understanding of them and, consequently, facilitate their protection.
... La región se caracteriza por un relieve local escarpado, causado por "cuencas y cordilleras" contractivas y volcanes (Kraemer et al., 1999) (Fig. 1). A esto se le suma un clima árido a semiárido con cuencas hídricas endorreicas, permitiendo la formación de ambientes lacustres de evaporación, como lagos, llanuras saladas y humedales (Alonso et al., 2006;Jordan y Mpodozis, 2006;Alonso y Rojas, 2020). ...
... El basamento de la Puna se compone principalmente de rocas metamórficas silicoclásticas de edad Pérmica, intruidos por varias generaciones de granitoides y aplitas durante el Paleozoico. A esto le siguen importantes secuencias Jurásicas donde alternan lutitas, areniscas y rocas volcánicas con lechos de coquina y calizas oolíticas (Alonso et al., 2006). Desde el Eoceno tardío al Plioceno, las cuencas sedimentarias presentan diferentes sucesiones de sedimentos clásticos no marinos intercalados con rocas piroclásticas y lavas. ...
... Desde el Eoceno tardío al Plioceno, las cuencas sedimentarias presentan diferentes sucesiones de sedimentos clásticos no marinos intercalados con rocas piroclásticas y lavas. Mientras que durante el Mioceno, se observan importantes niveles de evaporitas continentales que se superponen de manera discordante a los depósitos clásticos anteriormente nombrados (Kraemer et al., 1999;Alonso et al., 2006). 15 Durante el cuaternario es común la formación de evaporitas en zonas deprimidas, rodeadas por bloques tectónicos orientados meridionalmente y formaciones volcánicas. ...
During the last decade, important Holocene microbialitic deposits have been reported in Central Andes. These are capable of developing under extreme environmental conditions, in a region subject to constant climatic changes. Initially these systems have been studied mainly from a genetic and microbiological biodiversity point of view, but little is known about the relationship between their producing microorganisms and the environmental factors of their habitat, and how this varies dynamically over time.
This doctoral thesis seeks to determine the intrinsic factors (producing microorganisms) and extrinsic (environmental parameters) in the Holocene microbialites of Las Quinoas (Salar de Antofalla), Laguna Verde (Salar de Antofalla) and Laguna Turquesa (Cuenca del Peinado); Puna Argentina, Central Andes. This study provides a tool to reconstruct the paleoenvironmental conditions of the host water bodies, and contributes valuable information to understand the adaptation of these microorganism communities to high stress environments. Added to this, their potential as analogues for the fossil record is evaluated, through a direct comparison with deposits of approximately 5.3 ma. and 66 ma.
Las Quinoas is a deposit of oncoids distributed along channels that enter in the Salar de Antofalla. Its growth is mainly controlled by the mineral saturation/sedimentary supply rate ratio, which depends on its position in the channels. These environmental factors directly influence its internal morphology and construction mechanisms. However, despite these variations, its producers (Proteobacteria and Bacteroidetes mainly) remain constant.
On the other hand, Laguna Verde is a hypersaline water body with important seasonal chemical variations. It is populated by domic structures, internally characterized by gypsum and carbonate facies. The growth of these structures is dominated by marked seasonal changes. Inside, the producing microorganisms (Cyanobacteria, Proteobacteria and Bacteroidetes), not only find protection against desiccation and UV-B radiation, but also participate directly and indirectly in the precipitation and degradation of the mineral facies that compose it.
Finally, in Laguna Turquesa, an important water crisis has been observed during the last decades, which modified the physicochemical conditions of the environment. However, the producing microorganisms have overcome these events in short periods of time, recolonizing the coast and paleocosts on three occasions. This new record
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provides evidence of the short-term resilience capacity of these communities, offering a key approach to understanding analogous processes throughout Earth's history.
Based on this, we can conclude that the studied microbial ecosystems constitute an important record to determine the environmental variations experienced at the local level in the Central Andes. At the same time, they allow to determine the adaptation and/or resilience capacity of their producing microorganisms to extreme conditions and climatic changes.
Surprisingly, important similarities at the microstructural level with the fossil stromatolites studied are described. These deposits show affinity for the same building mechanisms, microbial building blocks, and microstructural elements. Therefore, they can be considered as a potential natural laboratory to understand the mechanisms of microbialite formation throughout the fossil record.
