Chilean Andes Research Articles

Rapid decline in extratropical Andean snow cover driven by the poleward migration of the Southern Hemisphere westerlies.

Seasonal snow in the extratropical Andes is a primary water source for major rivers supplying water for drinking, agriculture, and hydroelectric power in Central Chile. Here, we used estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) to analyze changes in snow cover extent over the period 2001-2022 in a total of 18 watersheds spanning approximately 1,100km across the Chilean Andes (27-36°S). We found that the annual snow cover extent is receding in the watersheds analyzed at an average pace of approximately 19% per decade. These alarming trends have impacted meltwater runoff, resulting in historically low river streamflows during the dry season. We examined streamflow records dating back to the early 1980s for 10 major rivers within our study area. Further comparisons with large-scale climate modes suggest that the detected decreasing trends in snow cover extent are likely driven by the poleward migration of the westerly winds associated with a positive trend in the Southern Annular Mode (SAM).

Unraveling the Geodynamic Evolution of the Pre– and Early–Andean Margin: Insights From Numerical Modeling

AbstractAn outstanding question in the geological evolution of the Chilean Andes is the cause of the westward shift and relocation of magmatism from the High Andes (HA) to the Coastal Cordillera (CC) during the Late Triassic, Pre–Andean stage. The spatiotemporal distribution of Permian–Triassic–Jurassic igneous rocks in northern‐central Chile (20°S–32°S) reveals a significant westward magmatic shift of ∼120 km during the Norian time. Despite diverse proposed models, the precise geodynamic mechanism behind this shift remains unclear. To address this, we used 2D numerical modeling to investigate two contrasting scenarios: (a) subduction rollback and (b) subduction transference/jump and reinitiation by terrane accretion. Our modeling results strongly support Scenario B, where mantle density and the size of the oceanic plateau are crucial for triggering subduction jump and reinitiation. This model aligns with geological and geophysical evidence and offers new insights into unraveling the Pre– and Early–Andean evolution.

Geological (Dis)orientations: Training Sites, Storytelling, and Fieldwork in the Chilean Andes

This article explores place-based geological storytelling by examining the role of training sites in the geoscientific learning process. Based on ethnographic work conducted with geoscientists in the Liquiñe-Ofqui Geological Fault, I illustrate how sites located in the Chilean Andes have historically been used to practice geoscientific storytelling and to learn the language and theory of plate tectonics. Building on scholarship in STS and the history of science which has documented how plate tectonics and the associated paradigm shift changed the authority of field geology, I show how, rather than replacing fieldwork, place-based observations still play a central role in helping students gain a professional vision in geology. Reflecting on fieldwork training sites and geoscientists’ negotiated attempts to tell geological stories, this article speaks to the question: from where are the stories of the earth told?

Water mites of a high-altitude thermal spring in the Chilean Andes (Acari: Hydrachnidia), with the description of a new Thermacarus species (Acari: Hydrachnidia: Thermacaridae)

New data are presented of water mites from a thermal spring in the high Andes of Chile. Three species have been found, i.e. Thermacarus chilensis n. sp., Hydryphantes thermalis Cook and Wandesia chechoi Cook.

Serological evidence of Coxiella burnetii in sheep herds from Lonquimay valley in the Chilean Andes

Serological evidence of Coxiella burnetii in sheep herds from Lonquimay valley in the Chilean Andes

Glacial to periglacial transition at the end of the last ice age in the subtropical semiarid Andes

Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.

Resolving the conflictive phylogenetic relationships of Oceanites (Oceanitidae: Procellariiformes) with the description of a new species

The family Oceanitidae, formerly considered a subfamily of Hydrobatidae, includes all the small storm-petrels of the southern hemisphere. The ancestor-descendent relationships and evolutionary history of one of its genera, Oceanites, have been partially studied, yielding contrasting results. We revised the phylogenetic relationships of this group using Bayesian inference (BI) based on new sequence data of the mitochondrial gene Cytb and linear morphological measurements of all species and five subspecies-level taxa in Oceanites, including a new taxon from the Chilean Andes. Our BI results show that the Oceanites genus is monophyletic and composed of four well-supported clades (posterior probability > 0.95): (1) chilensis; (2) exasperatus; (3) gracilis, pincoyae, and barrosi sp. nov.; and (4) oceanicus and galapagoensis. The species O. chilensis is a basal clade within Oceanites. According to our time-calibrated tree, the split between Oceanites and the other genera in Family Oceanitidae is estimated to be ~35.9 Mya, and the oldest divergence within Oceanites (the split between O. chilensis and other Oceanites) was dated to the early Miocene, around c. 21.3 Mya. The most probable geographic origin of Oceanites is the Southern Ocean. The morphological data suggest continuous size variation between Oceanites taxa, ranging from smallest in gracilis to largest in exasperatus. Based on our phylogenetic hypothesis, and morphological analyses, we suggest elevating to species status the taxa galapagoensis, chilensis, and exasperatus, and we describe a new taxon barrosi sp. nov., thus recognizing a total of seven species within the genus Oceanites.

PORPHYRY COPPER RECURRENCE IN THE ANDES OF CHILE AND ARGENTINA

Abstract Porphyry Cu deposits in the Chilean and Argentinian central Andes occur in a series of orogen-parallel magmatic arcs, which migrated episodically eastward since the Early Cretaceous. The three Cenozoic belts, corresponding to Paleocene-early Eocene, middle Eocene-early Oligocene, and Miocene-early Pliocene epochs, cut obliquely across a composite belt of subeconomic porphyry Cu mineralization formed at several times during the Late Carboniferous to Triassic interval. Based mainly on U-Pb zircon and Re-Os molybdenite ages, 10 Cenozoic porphyry Cu centers, including major deposits in all three of the Cenozoic belts, occupy the same sites as late Paleozoic-Triassic porphyry Cu mineralization where their respective magmatic arcs cross one another. The sites of recurrent porphyry Cu mineralization are believed to be underlain by long-lived dike conduits that were utilized at least twice—first in the late Paleozoic-Triassic and then again in the Cenozoic—to rapidly transmit hydrous magma from deep to shallow levels of the crust. Contenders for preferential dike localization include arc-oblique fault and subjacent ductile shear zones—transcrustal discontinuities—long hypothesized to be present in the region, particularly where they intersect magmatic arcs and associated porphyry Cu belts. Regardless of the controls on porphyry Cu recurrence, alteration zones hosted by late Paleozoic-Triassic volcanic and plutonic rocks in the central Andes of Chile and Argentina must be considered prime exploration targets for potentially large, high-grade Cenozoic porphyry Cu deposits.

Geomorphic signatures of neotectonic activity along the Western Andean Front in the Chilean Andes (35°S to 37°S)

AbstractCharacterizing neotectonic activity along mountain fronts in active orogens is the key to better understanding trajectories of landscape evolution, climatic‐tectonic couplings and natural hazards. One such prominent mountain front is the Western Andean Front (WAF), which defines the boundary between two main physiographic units along the Chilean Andes (15°S to 39°S): the Central Depression and Principal Cordillera. This study analyses the geomorphic imprints of neotectonic fault activity in the WAF between 35°S and 37°S. We used several topographic metrics, including the mountain‐front sinuosity index (Smf), the valley floor width‐to‐height ratio (Vf) and the stream length‐gradient (SL) index to gain information about the regional distribution of deformation patterns and its relative tectonic activity for distinctive segments. In addition, a raster map combining rock strength (RS) and mean annual precipitation (MAP) allowed discriminating lithology‐climate vs. tectonics influence on SL anomalies from catchments spanning from the main deformation zone to the regional drainage divide. We use the local relief and swath profiles to quantify the incision and transient state of mountain fronts to evaluate the geomorphic response to tectonic and/or climatic input. Our analysis highlights significant variations from north to south, delineating two distinct segments with different topographic, geomorphic and geometric fault characteristics. These segments are indented at approximately 36°S. From north to south, there is a segment with an inactive thrust front with a primarily climate‐driven fluvial response over long timescales and a second segment with a transient state adjusting to relatively high uplift rates. Morphometric data analysis, DEM‐based morpho‐structural maps, geological maps and previous research support the interpretation of two sets of neotectonic faults: (1) NNE‐striking reverse faults with a dextral slip component and (2) NW‐striking sinistral slip faults, likely a response to deformation partitioning caused by oblique subduction on a continental margin.

Glacial and volcanic landforms in the upper catchment of Claro River, Central Chile (35.5°S): A Late Quaternary geomorphological case study

AbstractThe upper catchment of the Claro river is located within the Transitional Southern Volcanic Zone in the Maule Region of Chile (35.5°S), at the foothills of Manantial Pelado volcano, a Pleistocene stratovolcano whose morphology suggests the occurrence of important glacial processes in the area. The observed glacial landforms can be sequenced and associated with episodes of volcanic activity. Different units of volcanic and glacial origin were identified based on field observations, detailed mapping, and digital elevation model and satellite image analysis. The contact relations between them made it possible to discern four events that can be linked to Marine Isotope Stages 8, 6, 4‐2, and to the Neoglacial. We propose seven stages in the geomorphological evolution from the late Pleistocene to the late Holocene, where there is coexistence between volcanic and glacial episodes, such as the emplacement of the Manantial Pelado volcano overlying the Abanico and Cola de Zorro formations; a subsequent debris avalanche; the enlargement of the Del Indio valley during the Penultimate Glaciation; the construction of Cerro Redondo (a minor eruptive center at the head of Del Indio valley); ongoing fluvial incision; and Neoglacial advances. The relative chronology proposed in this work contributes to clarifying the Pleistocene–Holocene geomorphological history in this catchment and to further understand the interplay between volcanic and glacial processes in the central Chilean Andes during the Quaternary.

Discriminating viscous-creep features (rock glaciers) in mountain permafrost from debris-covered glaciers – a commented test at the Gruben and Yerba Loca sites, Swiss Alps and Chilean Andes

Abstract. Viscous-flow features in perennially frozen talus/debris called rock glaciers are being systematically inventoried as part of the global climate-related monitoring of mountain permafrost. In order to avoid duplication and confusion, guidelines were developed by the International Permafrost Association to discriminate between the permafrost-related landform “rock glacier” and the glacier-related landform “debris-covered glacier”. In two regions covered by detailed field measurements, the corresponding data- and physics-based concepts are tested and shown to be adequate. Key physical aspects which cause the striking morphological and dynamic differences between the two phenomena/landforms concern the following: tight mechanical coupling of the surface material to the frozen rock–ice mixture in the case of rock glaciers, contrasting with essential non-coupling of debris to the glaciers they cover; talus-type advancing fronts of rock glaciers exposing fresh debris material from inside the moving frozen bodies, as opposed to massive surface ice exposed by increasingly rare advancing fronts of debris-covered glaciers; and increasing creep rates and continued advance of rock glaciers as convex landforms with structured surfaces versus predominant slowing down and disintegration of debris-covered glaciers as often concave landforms with primarily chaotic surface structure. Where debris-covered surface ice is or has recently been in contact with thermally controlled subsurface ice in permafrost, complex conditions and interactions can develop morphologies beyond simple either–or-type landform classification. In such cases, the remains of buried surface ice mostly tend to be smaller than the lower size limit of “glaciers” as the term is applied in glacier inventories and to be far thinner than the permafrost in which they are embedded.

Phylogeny of Berberidopsidales based on nuclear and chloroplast loci, with the description of a new species of Berberidopsis endemic to Central Chile

AbstractBerberidopsidales comprises two families: monotypic Aextoxicaceae (Aextoxicon punctatum in Chile and Argentina) and Berberidopsidaceae. The latter includes Australian monotypic Streptothamnus (S. moorei) and Berberidopsis (B. beckleri in Australia and B. corallina in Chile). A new Berberidopsis species from the Central Chilean Andes is here described. Phylogenetic analyses based on nuclear and chloroplast data clarified the relationships within Berberidopsidales. The new species, Berberidopsis granitica, is sister to the Chilean endemic B. corallina, and this clade is sister to the Australian B. beckleri. The dated molecular phylogeny places the split between the South American B. corallina and B. granitica into the late Miocene/early Pleistocene and the split between South American and Australian Berberidopsis to the late Miocene and Pliocene, suggesting transoceanic dispersal rather than vicariance. Climatic niche analyses show two distinct and non‐overlapping climatic niches for the Australian and southern South American species. Berberidopsis granitica and B. corallina also differ clearly in their habitat and morphology, in addition to their climatic niche. Berberidopsis granitica has a very restricted distribution area and grows in the Andes under montane climatic conditions, unique within Berberidopsidales.

The application of PRISMA hyperspectral satellite imagery in the delineation of distinct hydrothermal alteration zones in the Chilean Andes: The Marimaca IOCG and the Río Blanco-Los Bronces Cu-Mo porphyry districts

This study provides an overview of the application of hyperspectral imagery acquired by the Italian satellite mission “PRecursore IperSpettrale della Missione Applicativa” (PRISMA), for mapping hydrothermal and supergene mineral alteration zones associated with different Cu deposits in the Chilean Andes. Study areas include the Marimaca Copper Project in the Naguayán district (Antofagasta Province), hosting Late Jurassic – Early Cretaceous iron oxide-copper–gold mineralizations and the Río Blanco-Los Bronces district (Santiago Region) known for its Late Miocene – Early Pliocene copper-molybdenum porphyry deposits. These mineral systems exhibit hydrothermal alteration haloes extending over several kilometers, with upward and outward mineral zonation.To characterize the surface-exposed alteration, the satellite imagery was processed using a multiple feature extraction workflow targeting the relative abundances and compositions of specific supergene and hydrothermal alteration minerals, including Fe-oxides and hydroxides (hematite-goethite), phyllosilicates (micas-kaolinite-chlorite), hydroxyl-bearing sulfates (alunite-natroalunite-jarosite) and epidote. The results reveal a zonation from proximal sulfates (natroalunite to alunite) and Al-rich white mica (ranging from 0.3 km-wide for the area identified to the east of the Marimaca deposit to 1 km-wide in correspondence of the Los Sulfatos deposit, respectively) to distal Al-poor white mica (0.2 to 0.5 km-wide, respectively) and an outer chlorite-epidote zone. In the Marimaca Project area, the structurally-controlled alteration evolves west to east from chlorite-rich to phengitic white mica (Al-poor). A NNE-SSW trending supergene leached cap covers a 6 km-long and up to 2 km-wide area from north to south. Our study documents how spaceborne hyperspectral imaging spectroscopy can support mineral exploration by enabling non-invasive reconnaissance mapping of the outcropping rocks, providing specific targeting information for follow-up field surveys and drilling campaigns.

A critical evaluation of the role of a geothermal system in lithium enrichment of brines in the salt flats: A case study from Laguna Verde in the Atacama Region of Chile

The association between geothermal fluids and lithium-rich brines in salt flats has been evaluated in a unique natural laboratory in the Chilean Andes. The area encompasses Laguna Verde (LV), a hypersaline lake, and a salt flat (salar) within a closed basin surrounded by volcanoes. The predominant lithology consists of andesitic-dacitic rocks, with limited occurrences of rhyolitic rocks. The LV geothermal system exhibits surface manifestations, including over 20 hot springs reaching 47 °C along the lake's southern margin. The upflow zone is represented by the fumarolic field in the Nevado Ojos del Salado volcano, 25 km southwest of LV. Lithium concentrations range from 2.76 to 4.46 mg/L in thermal water and 0.59 to 0.76 mg/L in the Peñas Blancas river water, which feeds into LV after passing through a volcanic environment rich in lithium-bearing rocks. However, the thermal waters contribute over six times more lithium than non-thermal waters, highlighting their significance in releasing and transporting lithium from the source rocks to its eventual accumulation in LV. This natural laboratory at LV provides an excellent opportunity to evaluate the association between geothermal fluids and lithium-rich brines, offering valuable insights into the processes involved in lithium enrichment in similar geological and climatic conditions in other geographic areas.

Metaphoric veiled image-schema of kinship organization in ceremonial space: A south Andean case

This study is an interdisciplinary approach to a veiled metaphoric design expressed in the present-day spatial layout of ecologically-derived patronyms of Mapuche lineages and families positioned in public ceremonial plazas. The perspective combines ethnoarchaeological, cognitive, iconographic, oral tradition, allegoric metaphor, and historical approaches to the organization and meaning of this design, taking into account the past and present dimensions of ritual media (e.g., political, ideological and sensorial) to render a concept publicly graspable. Shamans and other informants state that the design represents an ancient foundational schema established for intercommunity political solidarity during times of both peace and conflict in the Spanish colonial and Republican era of the south-central Andes of Chile. Shamans were asked to draw their mental image of the hidden design of the plaza to pictographically reveal its visual representation. By examining the iconography of patronyms depicting a loosely structured order of families hierarchically positioned in ceremonial space, the invisible nature of this pattern and its wider political and kinship meaning is considered. Viewed from an archaeological perspective, this schema is suggested to be associated with a “chiefdom” or intermediate, polity-level society, and may represent a type of mental imagery and template that served as a precursor to the visible iconography on wood, stone, adobe, ceramic, textile and other media of complex Pre-Colombian societies. Ultimately, this schema is a conceptual metaphor: mapping and structuring knowledge of a trophic hierarchy of elements in the natural world to evoke a political and public organizational principle through sensorial experiences and life concerns in the invisible and visible domains of an Andean-like ceremonial format.

Drivers of plant diversity, community composition, functional traits, and soil processes along an alpine gradient in the central Chilean Andes.

High alpine regions are threatened but understudied ecosystems that harbor diverse endemic species, making them an important biome for testing the role of environmental factors in driving functional trait-mediated community assembly processes. We tested the hypothesis that plant community assembly along a climatic and elevation gradient is influenced by shifts in habitat suitability, which drive plant functional, phylogenetic, and spectral diversity. In a high mountain system (2400-3500 m) Región Metropolitana in the central Chilean Andes (33°S, 70°W). We surveyed vegetation and spectroscopic reflectance (400-2400 nm) to quantify taxonomic, phylogenetic, functional, and spectral diversity at five sites from 2400 to 3500 m elevation. We characterized soil attributes and processes by measuring water content, carbon and nitrogen, and net nitrogen mineralization rates. At high elevation, colder temperatures reduced available soil nitrogen, while at warmer, lower elevations, soil moisture was lower. Metrics of taxonomic, functional, and spectral alpha diversity peaked at mid-elevations, while phylogenetic species richness was highest at low elevation. Leaf nitrogen increased with elevation at the community level and within individual species, consistent with global patterns of increasing leaf nitrogen with colder temperatures. The increase in leaf nitrogen, coupled with shifts in taxonomic and functional diversity associated with turnover in lineages, indicate that the ability to acquire and retain nitrogen in colder temperatures may be important in plant community assembly in this range. Such environmental filters have important implications for forecasting shifts in alpine plant communities under a warming climate.

Monitoring surface velocity changes of rock glaciers in the Chilean Andes using DINSAR technique with PAZ imagery

Vertical deformation associated with the displacement of rock glaciers in the upper Mapocho river basin, in the central Andes of Chile, was monitored using a series of PAZ radar satellite images and the DInSAR technique. Forty-one PAZ images of ascending and descending orbit were processed with the Small Baseline Subset (SBAS) technique. Regarding the obtained results, it was estimated that the vertical displacement velocity of rock glaciers between October 9, 2019 and April 22, 2021 reached up to -22 mm/year and the movement in the W-E direction ranged from -47 to 38 mm/year. This remote sensing technique is a useful tool to measure the surface displacement of rock glaciers, compared to conventional techniques such as GNSS point measurements, especially in the semi-arid Andes, which is one of the most important reservoirs of these geoforms worldwide.

Overview of the distributed image processing infrastructure to produce the Legacy Survey of Space and Time

Overview of the distributed image processing infrastructure to produce the Legacy Survey of Space and Time

The role of intra-arc strike-slip fault systems on landslide generation at Curarrehue (Central Southern Chilean Andes)

Climate change has increased extreme rainfall events in the Central Southern Andes, favouring slope instabilities and triggering landslides. However, other predisposing factors that control landslides in this region are still poorly constrained. We systematically study the link between landslides and active faults systems thought detailed mapping and classification, highligthing mainly rock avalanches. Our analysis was complemented with hand-specimen and optical microscope host rock description, clay classification via x-ray diffraction and fluorescence, and an exhaustive fault kinematics assessment to determine the controlling the strain in the zone. Our results show that 90.5% of the landslides are linked with active strike-slip faults, characterised by phyllosilicate-bearing hydrothermally altered host rock. In this regard, the presence of clay minerals in fault-slip planes contributes to the generation of landslides in mountain ranges. This phenomenon could be enhanced due the ability to clays induce pressure variations by swelling triggering by extreme rainfalls. This interaction between faults and landslides is important for geological hazard assessment and landslide monitoring as being a recurrent configuration in this section of the Central Southern Chilean Andes.

Micromonospora parastrephiae sp. nov. and Micromonospora tarensis sp. nov., isolated from the rhizosphere of a Parastrephia quadrangularis plant growing in the Salar de Tara region of the Central Andes in Chile.

Two novel Micromonospora strains, STR1-7T and STR1S-6T, were isolated from the rhizosphere of a Parastrephia quadrangularis plant growing in the Salar de Tara region of the Atacama Desert, Chile. Chemotaxonomic, cultural and phenotypic features confirmed that the isolates belonged to the genus Micromonospora. They grew from 20 to 37 °C, from pH7 to 8 and in the presence of up to 3 %, w/v NaCl. The isolates formed distinct branches in Micromonospora gene trees based on 16S rRNA gene sequences and on a multi-locus sequence analysis of conserved house-keeping genes. A phylogenomic tree generated from the draft genomes of the isolates and their closest phylogenetic neighbours showed that isolate STR1-7T is most closely related to Micromonospora orduensis S2509T, and isolate STR1S-6 T forms a distinct branch that is most closely related to 12 validly named Micromonospora species, including Micromonospora saelicesensis the earliest proposed member of the group. The isolates were separated from one another and from their closest phylogenomic neighbours using a combination of chemotaxonomic, genomic and phenotypic features, and by low average nucleotide index and digital DNA-DNA hybridization values. Consequently, it is proposed that isolates STR1-7T and STR1S-6T be recognized as representing new species in the genus Micromonospora, namely as Micromonospora parastrephiae sp. nov. and Micromonospora tarensis sp. nov.; the type strains are STR1-7T (=CECT 9665T=LMG 30768T) and STR1S-6T (=CECT 9666T=LMG 30770T), respectively. Genome mining showed that the isolates have the capacity to produce novel specialized metabolites, notably antibiotics and compounds that promote plant growth, as well as a broad-range of stress-related genes that provide an insight into how they cope with harsh abiotic conditions that prevail in high-altitude Atacama Desert soils.