Central Andes Research Articles

Lithium mica clasts document magmatic evolution prior to eruption in the macusani volcanic field in peru

Typically found in rare-metal granites and pegmatites, lithium micas are increasingly considered a resource for lithium as global demand surges. In a recently discovered major lithium resource within the Macusani Volcanic Field in Peru, lithium mica crystal clasts hosted by a tuffaceous mudstone represent an important ore constituent. The mm-scale mica clasts comprise a zinnwaldite core and a lepidolite rim. Compositionally similar to micas in global peraluminous, rare-metal-rich leucogranites and LCT pegmatites, they exhibit enrichment in incompatible, fluid-mobile lithophile elements relative to micas in other volcanogenic and intrusive units in the Macusani Volcanic Field. The compositions of the mica crystal clasts record high degrees of magmatic differentiation and exsolution of a magmatic vapor phase during their crystallization in a ligand-rich, peraluminous crystal mush. 40Ar/39Ar dating of zinnwaldite-lepidolite crystal clasts reveals cooling between 8823 ± 9 and 8717 ± 44 ka, coinciding with a regional magmatic lull in the Central Andes of southern Peru. A general slowdown in magmatic activity and a hiatus in volcanism may have contributed to extreme differentiation and pre-eruptive volatile build-up. This study provides crucial insights for lithium exploration, highlighting volcanogenic-sedimentary lithium mica deposits as a promising exploration target in peraluminous volcanic fields.

Management of South American camelids in the eastern Andes of Northwestern Argentina: a comparative study of archaeological cases in the last two millennia

Human-camelid interactions were an essential component in the everyday life of the societies that inhabited the South and Central Andes. While numerous studies have concentrated on this topic, they have primarily focused on the Puna plateaus, where camelids remain a key resource today. In contrast, the eastern Andean regions of Northwestern Argentina have been historically viewed as marginal and the presence of camelids in zooarchaeological assemblages has been often attributed to hunting or specialized pastoralist production for political and administrative centers located in the western valleys. Recent research in this area challenges and reshapes this view. This paper reassesses the presumed marginality of these regions by critically looking at zooarchaeological information including taxonomic, osteometric, age profiles and skeletal parts representation analyses from several key sites. We propose a preliminary model of camelid management in these environments, contributing to broader discussions of similar practices in non-high-Andean regions of South America.

Description of the first species of the genus Archaeopodagrion (Philogeniidae: Odonata) from the Colombian Central Andes

Archaeopodagrion oelmannae sp. nov. is described from the northern Central Colombian Andes, representing the first record of the genus in the Central Cordillera. The species seems to be very rare, only one male specimen found after an extensive sampling effort. The species is probably endangered, as it has been found only in a small protected forest in a region where the habitat is threatened by agricultural expansion. This paper also presents a novel taxonomic key for the genus based on the prothorax of the males and a distribution map for all species in the genus.

Plio-Pleistocene Western Retroarc Magmatic Evolution and Its Relation With Variable Subduction Settings in the Southern Central Andes (34-38 °S)

Plio-Pleistocene magmatism in the Southern Central Andes (34–38 °S) developed contemporaneously with inferred steepening and destabilization of the subducted Nazca plate associated with a slab tearing at 38°S. Within this setting, arc-related magmatic activity developed in N-S striking belts. Particularly, the studied Varvarco Volcanic Field (VVF) formed in an unusual western retroarc position (70 °W), between the eastern retroarc (69°30’ W) and the present-day arc (68°30’ W). Here we present new field data along with major, minor, and trace elements analyses, Sr-Nd-Pb isotope systematics, and a zircon U/Pb age of ~2.36 Ma to better constrain the linkage between emplacement of the VVF during the Nazca plate steepening and the westward migration of the asthenospheric wedge. The VVF is characterized by basic to intermediate lavas interbedded with pyroclastic deposits, and rhyolitic intrusives. The Basal Lava Flows are calc-alkaline basaltic andesites to andesites, whereas the Upper Lava Flows are less evolved tholeiitic basalts to basaltic andesites. Steepening of the Nazca plate and the onset of the upper plate extension during the VVF emplacement favored the rapid ascent of the latest VVF magma pulses, which underwent low degrees of fractional crystallization. A regional comparison is made to evaluate the impact of the variable tectonic setting on Plio-Pleistocene Andean magmatism. The VVF magmatism shows an arc-like signature, although less pronounced than the present-day volcanic arc. This behavior is also seen when considering all Plio-Pleistocene western retroarc volcanism, whose moderate slab fluids input is associated with their higher distance to the trench relative to the main volcanic arc. Meanwhile, the upwelling of a plume-like structure associated with the Nazca plate tearing has only affected the southern Payenia eastern retroarc volcanoes and the southeastern magmatic units of the western retroarc located just above the tearing.

Increased moisture availability in the Central Andes during the Miocene Climatic Optimum

Increased moisture availability in the Central Andes during the Miocene Climatic Optimum

Aulonemia insolita (Bambusoideae: Bambuseae: Arthrostylidiinae) a new remarkable woody bamboo species with internode dimorphism endemic to Bolivia and Peru

Species belonging to the genus Aulonemia have distribution across Mexico, Central America, northern and central Andes, the Guiana shield and southern Brazil. Three Aulonemia species: Aulonemia hirtula, A. queko, and A. herzogiana are known to have dimorphic internodes. In this study, we describe a new species of Aulonemia, characterized by culms with a pattern of one long internode followed by four to five shorter internodes. Notably, this species exhibits erect culm leaf blades, an uncommon trait within the genus. This study provides a comprehensive description of this new Aulonemia species, along with a distribution map, photographs and a morphological key to the species of Aulonemia with dimorphic internodes.

Morphometric disparities in skull size and shape of capuchin monkeys (Cebidae: Cebus) in northern South America and Central America.

Taxonomic classifications of the gracile capuchin monkeys, Cebus, have traditionally been based on cranio-dental and pelage characters. Advances in molecular biology have provided information on the evolutionary history of the genus but the taxonomy and distribution limits of taxa in the northern Andes are still under debate. To assess morphometric disparities and compare the results with hypotheses based on genetic evidence for Cebus taxonomy, we used 2D geometric morphometrics on 206 adult specimens (127 males, 77 females, 2 unsexed) belonging to 12 taxa by assigning Type I landmarks in the frontal (11), lateral (18) and ventral (16) views of the skull, and 14 in the mandible. Our results show that skull shape is more variable than centroid size and that morphometric disparities exist across and within all three geographic groups (Central America, Andes, and Amazon). Although skull shape in Cebus tends to vary slightly, our results suggest differences among some taxa and highlight the utility of studying shape in addition to methods that have focused on size. Some results concur with the taxonomic classifications based on molecular evidence but it is important to note that Cebus species are wide-ranging with high inter- and intraspecific phenotypic variability in diverse ecological conditions. This makes it difficult to provide species diagnoses based just on morphometric or morphological characters and suggests the need to integrate different sources of evidence to resolve uncertainties about the taxonomy and the evolutionary relationships in the genus.

Not all trade-offs and synergies between ecosystem services are created equal: assessing their spatio-temporal variation in response to land cover change in the Colombian Andes

Recent increases in societal demands for ecosystems have caused significant shifts in vegetation, land use, and ecological dynamics, particularly in sensitive mountain regions with strong environmental gradients like the tropical Andes, where environmental change is occurring rapidly, altering crucial services related to water and soil, including hydrological regulation and erosion control. These changes affect ecosystem functions at different time scales, and the effects can vary through space. However, most studies focus on individual services and rarely assess how these services interact across different spatial and temporal scales. By applying a disaggregated spatio-temporal approach, we investigate synergies and trade-offs between ecosystem services under various land-use transition scenarios in the tropical Andes. Focusing on a strategic watershed in the central Andes of Colombia, we analyzed 22-years of land cover change and tested transitions between three hypothetical land cover scenarios: scenario 1—natural, scenario 2—pastures, and scenario 3—crops. The results show that while hydrological flows remained stable due to consistent land cover, hypothetical scenarios highlight the significant impact of vegetation cover on hydrological regulation, soil erosion, and their interactions. Our spatial analysis reveals 81 distinct land transition types, leading to synergies and trade-offs between services depending on environmental factors. Notably, the same transition may produce either a synergy or a trade-off depending on contextual variables. This approach offers a novel method for analyzing ecosystem service dynamics over space and time, providing valuable insights for targeted land management and conservation planning. These findings highlight the importance of understanding these dynamics for effective decision-making in critical ecosystems.

A new section within Passiflora subgenus Decaloba (Passifloraceae) borne from the “Passiflora lobbii group”, with three new species from the montane forests of southern Ecuador and Bolivia

Various previous authors have questioned the cohesion and taxonomic association of a group of Central Andean Passiflora species hereto commonly referred to as “The Lobbii group”. Following targeted studies, both literature and in the field, we here elevate this monophyletic group to the independent rank of section within subgenus Decaloba, supersection Multiflora. The alleged infraspecific variability and the highly disjunct distribution of the Bolivian typified Passiflora exoperculata has also been evaluated. Following targeted fieldwork to Ecuador and Bolivia, previously unavailable high-resolution photos allow the definition of distinct morphological features to separate the Ecuadorean Passiflora skrabaliana sp. nov. from the Bolivian Passiflora exoperculata; and Passiflora justinianoi sp. nov. and Passiflora lobbii subsp. charazanica subsp. nov. from the enigmatic Passiflora solomonii. The ecology and taxonomic association of the Passiflora lobbii group, now Lobbii sect. nov., is highlighted. A key to the species of this new section depicting morphological details between these close relatives is presented.

The Central Andes of South America: a review of its tectono-magmatic evolution

The Central Andes of South America: a review of its tectono-magmatic evolution

Monogenetic volcanism fed by complex magmatic processes: El Negrillar volcanic field (Central Andes, Chile)

Monogenetic volcanism fed by complex magmatic processes: El Negrillar volcanic field (Central Andes, Chile)

Tombs as Evidence of Religious Diversity in the Sacred Valley, Peru (ca. AD 1000–1532)

Abstract This article articulates a regional, diachronic approach to precontact central Andean tombs by interpreting differences in materiality and function as evidence for distinct religious traditions. I analyze a sample of 788 tombs from 30 sites in the Sacred Valley and adjacent tributary valleys (Cusco, Peru), built and used during the Late Intermediate and Inka periods (ca. AD 1000–1532). Combining primary and published datasets, this sample includes a wide variety of tombs that variably facilitated or impeded certain interactions and relationships between the living, the dead, and the environment. To understand this diversity, I develop a typology comprising six tomb types based on morphological traits, which exhibit overlapping distribution patterns at local and regional scales. In contrast to studies that emphasized commonality and timelessness in central Andean mortuary practices, these data attest to considerable diversity in belief and value systems during half a millennium. As such, this study challenges existing models and presents new interpretations of late precontact tombs, considering that central Andeans across time and space held divergent beliefs about life and death. Recognizing diversity in past and present Indigenous societies is required for an empirical and decolonial archaeology that rejects stereotypes of cultural homogeneity.

Preadult Living Conditions During Sociopolitical Transition in Quebrada Chupacigarro Cemetery (500–400 bc), Supe Valley, Peru: Childhood Morbidity and Sociopolitical Change in Prehistoric Central Andes

ABSTRACTThrough a detailed assessment of nonspecific stress markers in 67 individuals (47 under 8 years old), this paper investigates the health conditions of preadults in Quebrada Chupacigarro Cemetery (QCC), North‐Central Coast of Peru, during the transition between the Middle and Late Formative periods (500–400 bc), a critical time of sociopolitical change in the Central Andes. Our objectives are to determine (i) the nature of preadult morbidity and mortality, (ii) periods of greater vulnerability in the population, and (iii) the etiological factors associated with health–disease processes in this context of population pressure. The results show a high prevalence of anemia‐related stress markers in preadults with a strong selective mortality in < 3.5‐year‐old individuals, and recurrent periods of adult morbidity. These findings indicate exposure to disease because of overcrowding, lack of sanitation and malnourishment, and support the idea of precarious living conditions in the Supe Valley around 500–400 bc.

Linking large-volume landslides with potential neotectonic activity of the Pocuro fault system, Central Andes (32°-33°S)

Linking large-volume landslides with potential neotectonic activity of the Pocuro fault system, Central Andes (32°-33°S)

Thermobarometry applied to the long-lived Cordillera de San Buenaventura volcanic complex in Central Andes. Part II: The effect of “liquid” in inverse modelling

Thermobarometry applied to the long-lived Cordillera de San Buenaventura volcanic complex in Central Andes. Part II: The effect of “liquid” in inverse modelling

Structural style of the Guañacos Fold and Thrust Belt (southern Central Andes): A tectonic setting for the Cura Mallín Basin revisited

Structural style of the Guañacos Fold and Thrust Belt (southern Central Andes): A tectonic setting for the Cura Mallín Basin revisited

Trans-crustal magmatic processes revealed by amphibole breakdown textures at the Quillacas monogenetic volcanic center, Bolivia

Trans-crustal magmatic processes revealed by amphibole breakdown textures at the Quillacas monogenetic volcanic center, Bolivia

Mesozoic to Cenozoic deformation of the western Central Andes: an update from structural and U–Pb data of the Calama Basin and surrounding areas

The Mesozoic to Cenozoic deformation of the Andean forearc of northern Chile is interpreted as a mix of crustal extension, contraction and strike-slip faulting. The effects of these diverse processes on the evolution of the western slope of the Central Andes have been widely debated. However, some factors (e.g. the initial distribution of the Pre-Andean structural and stratigraphic elements, the location and nature of the main sediment sources active during the deformation, the timing of Andean uplift and the location of synorogenic depocenters) are still unknown. In response to these questions and to update our previous knowledge of the tectonic evolution of the Andean forearc, we developed a regional study of the Calama Basin and surrounding areas considering the occurrence of good exposures and the availability of subsurface data. We integrated previous and new field data, 2D seismic profiles and zircon U–Pb ages from Mesozoic to Cenozoic units. Our results indicate a Triassic–Jurassic deformation dominated by rifting that progressed from an intracontinental domain, with the development of isolated half-graben in the Triassic, to the opening of broad marine rift-related basins during Jurassic times, thus confirming many of the interpretations made previously for the Pre-Andean evolution of northern Chile. The new ages of the continental post-rift units suggest that the rift system remained active at 95 Ma. After the post-rift units, the Late Cretaceous orogenic history started with the inversion of pre-existing Triassic and Jurassic rift-related structures, thus allowing the extrusion of synrift and post-rift strata. The latter is well outlined by the Chintoraste Fault exposed in the Loa and San Salvador rivers. During this period, the Andean deformation front was positioned in this region, as recorded by nearly 2 km of Upper Cretaceous to Paleocene synorogenic strata deposited on the inversion anticlines. From the Eocene, an important basement-involved tectonism took place as a result of the eastward migration of the Andean deformation front. The latter allowed the unroofing of the Paleozoic pre-rift basement blocks, creating a topographic relief dominated by contractional intermontane basins (e.g. the Calama Basin). These were filled by sediments eroded from the basement blocks (e.g. the Sierra Limón Verde and Tuina sectors) elevated by reverse faults and by the Mio-Pliocene volcanic products of the magmatic arc.

Paleomagnetic data from volcanic rocks in the southern Central Andes of Argentina and their implications for tectonics and geomagnetic field behavior

Paleomagnetic data from volcanic rocks in the southern Central Andes of Argentina and their implications for tectonics and geomagnetic field behavior

New particle formation dynamics in the central Andes: contrasting urban and mountaintop environments

Abstract. In this study, we investigate atmospheric new particle formation (NPF) across 65 d in the Bolivian central Andes at two locations: the mountaintop Chacaltaya station (CHC, 5.2 km above sea level) and an urban site in El Alto–La Paz (EAC), 19 km apart and at 1.1 km lower altitude. We classified the days into four categories based on the intensity of NPF, determined by the daily maximum concentration of 4–7 nm particles: (1) high at both sites, (2) medium at both, (3) high at EAC but low at CHC, and (4) low at both. These categories were then named after their emergent and most prominent characteristics: (1) Intense-NPF, (2) Polluted, (3) Volcanic, and (4) Cloudy. This classification was premised on the assumption that similar NPF intensities imply similar atmospheric processes. Our findings show significant differences across the categories in terms of particle size and volume, sulfuric acid concentration, aerosol compositions, pollution levels, meteorological conditions, and air mass origins. Specifically, intense NPF events (1) increased Aitken mode particle concentrations (14–100 nm) significantly on 28 % of the days when air masses passed over the Altiplano. At CHC, larger Aitken mode particle concentrations (40–100 nm) increased from 1.1 × 103 cm−3 (background) to 6.2 × 103 cm−3, and this is very likely linked to the ongoing NPF process. High pollution levels from urban emissions on 24 % of the days (2) were found to interrupt particle growth at CHC and diminish nucleation at EAC. Meanwhile, on 14 % of the days, high concentrations of sulfate and large particle volumes (3) were observed, correlating with significant influences from air masses originating from the actively degassing Sabancaya volcano and a depletion of positive 2–4 nm ions at CHC but not at EAC. During these days, reduced NPF intensity was observed at CHC but not at EAC. Lastly, on 34 % of the days, overcast conditions (4) were associated with low formation rates and air masses originating from the lowlands east of the stations. In all cases, event initiation (∼ 09:00 LT) generally occurred about half an hour earlier at CHC than at EAC and was likely modulated by the daily solar cycle. CHC at dawn is in an air mass representative of the regional residual layer with minimal local surface influence due to the barren landscape. As the day progresses, upslope winds bring in air masses affected by surface emissions from lower altitudes, which may include anthropogenic or biogenic sources. This influence likely develops gradually, eventually creating the right conditions for an NPF event to start. At EAC, the start of NPF was linked to the rapid growth of the boundary layer, which favored the entrainment of air masses from above. The study highlights the role of NPF in modifying atmospheric particles and underscores the varying impacts of urban versus mountain top environments on particle formation processes in the Andean region.