Southern Peru Research Articles

EVALUACIÓN DE LOS PARÁMETROS ZOOTÉCNICOS PARA ALEVINES DE Brycon cephalus SÁBALO COLA ROJA, EN LA ZONA COSTERA DEL SUR DEL PERÚ

In order to evaluate the zootechnical parameters for red-tailed tarpon Brycon cephalus fingerlings, in a region other than Amazonia, the evaluation of growth parameters in temperate waters was carried out for 60 days in the port of Ilo, Department of Moquegua. 84 fingerlings were used in 70 liters of water and two biometrics were performed, fluctuating in size from 3.5 cm to 9 cm at the end of the trial. Fingerlings were fed commercial trout feed of 45% protein, 8% fat and 25% carbohydrate, a feeding rate of 4.5% of biomass, distributed 3 times per day. The results reported as an average water temperature of 20.6°C, survival rate of 2.4%, growth determined by y=0.0155 X 2.8284 and a coefficient of determination of R²=0.975, average condition factor (K): 0.04393±0.0126 SD, Relative Growth Rate (TCR) of 9.5%, Specific Growth Rate (TCE) of 3.9% and Apparent Feed Conversion (CAA) of 1.4. With which it is observed that the parameters evaluated in the coastal zone of southern Peru are close to the native cultivation conditions.

Shallow Suberitida (Porifera, Demospongiae) from Peru.

This study describes 81 specimens belonging to Suberitida, collected during the projects Esponjas del Perú (ESPER), Esponjas da América do Sul (EsponjAS) and Semilla UCSUR 2019 (Demospongiae) along the coast of Peru, down to 30 m depth. Using morphological analyses, eight species were identified, one of which is new to science: Halichondria (H.) cristata, H. (H.) prostrata, Hymeniacidon perlevis, Johannesia reticulosa, Plicatellopsis expansa, Suberites aff. latus, Terpios cf. granulosus and Suberites inti sp. nov. Halichondria (H.) cristata, originally from Tierra del Fuego (SW Atlantic), was found widely distributed along the coast of Peru (06° S-14° S). The Magellanican H. (H.) prostrata and the formerly Chilean endemic P. expansa are extended up to Central Peru (12° S). Hymeniacidon perlevis, which presents a highly variable morphology (colour, shape, and spicule size), is firstly reported from the SE Pacific and its continuous occurrence in Peru (04° S-17° S) should be monitored given its supposed invasive potential. Johannesia reticulosa, previously known from Chile (20° S) and southern Peru (13° S), was found further north (11° S). Suberites latus and T. granulosus were originally recorded far-off from the Peruvian coast, in British Columbia and Hawaii, respectively. Thus, the occurrences of Suberites aff. latus and Terpios cf. granulosus are unexpected and should receive special attention in future molecular studies assessing their taxonomical status. Suberites inti sp. nov. characterised by its skeleton with ectosomal bouquets and multispicular choanosomal tracts, and two categories of straight tylostyles, is provisionally endemic to Paracas (13° S). With these results, the number of shallow Suberitida from Peru increases from 2 to 9. However, this number might rise as sampling in deeper environments could bring descriptions of new records.

COVID-19 and Its Effects on the Management of the Basic Quality Conditions in Universities of Peru, 2022

The purpose of this study was to determine the influences of variables, crisis management, distance education, the organizational image, and student satisfaction on the basic quality conditions in Peruvian universities during the COVID-19 pandemic. A quantitative, nonexperimental explanatory approach with stratified random sampling was used. A questionnaire was applied to 513 students from public and private universities in southern Peru who received distance education during the months of September to November 2022. For the analysis of the results, a structural equation model (SEM). A hierarchical linear regression was carried out to test the hypotheses according to the dimensions studied on the student satisfaction scale. The study findings showed that distance education and student satisfaction had positive impacts on the basic quality conditions, while crisis management and the organizational image had a positive relationship but a smaller effect on the quality of the conditions. We concluded that the applied model allows the causal relationships between variables to be explored and that the results will allow university authorities to generate policies that improve their organizational image and crisis management processes and, at the same time, allow them to better plan their crisis management strategies to achieve better satisfaction within the framework of a sustainable university.

Adjacent Iron Oxide-Apatite and Iron Oxide Copper-Gold Mineralization in the Acarí District, Peru: The Magmatic to Hydrothermal Transition

Abstract Hierro Acarí and Cobrepampa are adjacent, Lower Cretaceous iron oxide-apatite (IOA) and iron oxide copper-gold (IOCG) districts, respectively, emplaced in the Coastal Cordillera of southern Peru, separated by a regional NW-trending fault. Mineralization in both districts is hosted mainly by Lower Cretaceous plutons of the Coastal batholith that intrude sedimentary and volcanic sequences of the inverted Cañete basin. The deposits form part of a region that includes the much larger Marcona and Pampa del Pongo IOA/skarn and the Mina Justa IOCG deposits, although Marcona is 60 m.y. older than the others. Hierro Acarí contains fracture-controlled steeply dipping, shallow-plunging N- and NE-trending magnetite veins in a 101.7 ± 1.4 Ma dioritic intrusive, and hematite mantos in a quartzite roof pendant. The magnetite ore shoots show colloform and microporous textures and grade downward within 150 m to actinolite and carbonates, which replace the magnetite. The Cobrepampa district comprises numerous NW-striking chalcopyrite-pyrite ± hematite veins and oxidized equivalents in a 99.7 ± 0.4 Ma monzonitic intrusive. Fluid inclusions indicate that the copper mineralization was deposited at 166° to 266°C from a fluid with low to moderate salinity of 3.8 to 16.5 wt % NaCl equiv. Colloform and microporous textures in magnetite are interpreted in comparable Chilean deposits to indicate colloidal transport of magnetite microlites, crystallized from a magma, which attach to bubbles in the magmatic-hydrothermal fluid in a process resembling froth flotation. Magnetite textures at Hierro Acarí suggest that magnetite was transported by this late magmatic process and deposited in the roof zone of the host intrusive. The hydrothermal fluid may have evolved to deposit hematite as mantos in the overlying sediments under more oxidizing conditions and may then have deposited the Cobrepampa copper and hematite veins in distal NW-trending faults. Recent studies into the geochemistry of Cañete basin volcanic rocks suggest that a mid-ocean ridge was subducted at the latitude of the Raúl-Condestable IOCG deposit, 350 km northwest of the Acarí district, at approximately 130 Ma, predating current Andean subduction below southern Peru. That situation could result in a configuration resembling the Gulf of California, where a series of fault-terminated pull-apart basins focus hydrothermal fluids at intervals along the main trough. IOCG and IOA/skarn mineralization in the Acarí district occurred during the early stages of Late Cretaceous basin inversion and intrusion of the Coastal batholith. However, the Marcona IOA deposit in the same districts was emplaced during an earlier, unrelated Jurassic to Early Cretaceous mineralizing episode.

Ceramic production in the Tiwanaku sphere: LA-ICP-MS in the Moquegua, Titicaca, and Cochabamba regions

Between 600 and 1100 CE, the Tiwanaku site emerged as the principal center of an impactful cultural phenomenon in the Andean altiplano. Its influence stretched from the Pacific coast to the Amazonian valleys and south into the Atacama Desert. We examine the results of a series of research projects utilizing LA-ICP-MS on ceramics and clays from a cross-section of Tiwanaku settlements in three of the principal regions of influence: the Cochabamba region of Bolivia, the Bolivian altiplano including the Tiwanaku site, and the Moquegua valley of southern Peru. Our research seeks to synthesize the nature of Tiwanaku ceramic production in its heartland and in the distinctive Tiwanaku settlements on both sides of the Andean continental divide. We use the geochemical data to elucidate the extent of ceramic exchange between regions as well as the diversity of ceramic production within local areas to assess the ways in which ceramic production was enacted in different places. This contribution is part of a special issue synthesizing the results of geochemical analysis of Andean ceramics through time and across space and makes reference to those other comparative studies in the volume.

Notable range extension of Chinchillula sahamae Thomas, 1898 (Rodentia, Sigmodontinae) to central Peru, with natural history notes

Chinchillula sahamae Thomas, 1898 is a sigmodontine rat, known to occur in southern Peru, northern Chile, and western Bolivia. In this study, we report new records of the species in the departments of Huancavelica and Junín, Peru, which extend this species’ known distribution 370 km northwest, and new records in the department of Tacna, which extend the upper elevational range of the species to 5100 m, 250 m higher than previously known. In addition, we include notes on natural history, especially nesting behaviour, based on direct observations.

A new species of frog (Terrarana, Strabomantidae, Phrynopus) from the Peruvian Andean Grasslands

We describe a new terrestrial frog from the puna grasslands adjacent to the Mantaro dry valley in southern Peru. Phrynopus apumantarumsp. nov. is similar in appearence to P. bufoides but is differentiable by lacking discoidal fold and enlarged warts on dorsum, lacking a prominent post ocular fold and having canthal and post ocular stripe. Lastly, we propose to place the new species under the Vulnerable (VU) category of the IUCN Red List, due its small distribution and habitat loss recorded at the type locality.

Diseño y validación de la escala de motivación para publicar un artículo científico en universitarios peruanos (MOPu-AC)

IntroductionPromoting student scientific production in Peru requires motivation to publish scientific articles. The objective of this study was to design and validate the scale of motivation to publish a scientific article in Peruvian university students. MethodsCross-sectional instrumental study, in which 417 university students of health sciences (58.0% women), aged 18 to 35 years (SD = 20.77, SD = 3.49), who were selected under a non-probabilistic convenience sampling, participated. Participants were recruited from medicine, nursing, psychology and nutrition, from two universities in southern Peru (private and state). The scale was designed in 5 stages, following international standards. Aiken's V coefficient was used to assess content-based validity, confirmatory factor analysis was used to analyze internal structure, and reliability was assessed by means of the Omega coefficient. ResultsAll items obtained a favorable evaluation in the expert judgment (V > 0.70). The confirmatory factor analysis supported an internal structure composed of 9 items distributed in 1 factor, reporting satisfactory goodness-of-fit indices (Chi2 = 62.72 with 27 gl, CFI = 0.98, TLI = 0.97, RMSEA = 0.05, SRMR = 0.02 and WRMR = 0.06). Finally, reliability reached a very acceptable level (ω = 0.96). ConclusionThe MOPu-AC scale demonstrates initial psychometric evidence of content-based validity, internal structure and reliability in university students in southern Peru; therefore, it may be useful as a management tool for formative research.

A note on the occurrence of sperm whales (Physeter macrocephalus) off Peru, 1995-2002

Thirty-eight sightings of sperm whales (Physeter macrocephalus) were recorded off Peru (3-18°S) during 21 surveys conducted aboard platforms of opportunity, 1995-2002, with a search effort of 33,407 nautical miles of observation. Two main areas of concentration were detected: northern Peru (19 sightings) and southern Peru (16 sightings). Almost 58% of sightings occurred during the same or consecutive days. Group size ranged 1-18 individuals, with a mean of 3.5 (SD=3.9). The modal group size was one, accounting for 36.8% of sightings. Groups of three or more individuals accounted for 39.5%. An important increase in sightings occurred between 2001 and 2002, accounting for 68% of the records and suggesting migration into Peruvian waters from other regions. Positive correlations between indices of relative abundance and the anomaly of sea surface temperature were found, although warm events such as El Niño increased the uncertainty in sighting rates, reducing correlation values. The positive relationship between indices of relative abundance and commercial catch per unit effort for the squid Dosidicus gigas suggests some degree of interaction, although the extent of the role of this squid in the diet of sperm whales in the area requires further study

Petrography and geochemistry of successions from northwest Bolivia

A complete section of Paleozoic sedimentary rocks has been sampled in northwest Bolivia to investigate compositional changes based on petrographic but mainly geochemical data. Studies of Paleozoic succession in southern Peru, northern Chile and northwest Argentina allowed to decipher the paleotectonic history of the region for the Paleozoic (e.g. compilations in Bahlburg et al., 2009). However, a few is only known about the area geographically in between. We focus here on an area in the vicinity of the capital La Paz, where the Paleozoic belongs paleogeographically to the so-called ‘altiplano’ and the ‘Cordillera Oriental del Norte’ and tectonically to the ‘Faja de Huarina del Norte’. The objective of the study is, hence, to establish a first complete stratigraphic insight of the Paleozoic to enable further studies on key formations or horizons. While the abovementioned areas to the north and south do reflect in the sedimentary record the emergence of a continental arc during the Ordovician, followed by a significant tectonic quiescence during the late Silurian and Devonian and succeeded by the evolution of a second active margin with a continental arc during the late Paleozoic, these events are not visible in the Bolivian samples which is sandwiched between the westerly Arequipa Massif and the eastern Sunsas belt, both composed of mainly metamorphic rocks.The Paleozoic section in northwest Bolivia shows highly recycled quartz-arenites of Ordovician age followed by Silurian and Devonian successions mainly composed of subangular to surrounded detritus, moderately sorted, devoid of significant typical metamorphic detritus. During the late Paleozoic, the rocks tend to a larger variability, partly even poorly sorted, higher amount of angular grains and the occurrence of volcaniclastic debris. Geochemically the same trend can be observed, with strongly recycled successions during the Ordovician (Zr/Sc 20–200) followed by moderately recycled rocks (mainly Zr/Sc 10–20100) with typical trace element composition for unrecycled upper continental crust (UCC). During the Permian, sediments which are less weathered and slightly less fractionated in their overall geochemical composition, have been deposited. The geochemistry may point to the evolution of late Paleozoic volcanism, recorded in overlying, but however, Triassic rocks. Significant increase or even typical UCC values of compatible elements or ratios are absent besides Cr and Ni increase in Ordovician rocks. The absence of any significant input of arc related detritus can be explained by not effective sediment dispersal system to transport arc related detritus into the depositional area. The low compositional and low to moderate textural maturity throughout the entire post-Ordovician stratigraphy implies relatively proximal sources and insignificant intra-basinal recycling. This together with the absence of metamorphic detritus, allows in proposing thick homogeneous sedimentary successions with low or no metamorphic overprint as major sources. Those covered possibly the today exposed metamorphic successions of the aforementioned basin surroundings. Sedimentary or any other lithologies older than the Ordovician and younger than Mesoproterozoic are nearly unknown in the region, besides one exception (Chilla beds; Bahlburg et al., 2020). Those hypothetical deposits would be at this stage of knowledge the best explanation.

Effect of religious fatalism and concern about new variants on the acceptance of COVID-19 vaccines.

To protect public health, it is important that the population be vaccinated against COVID-19; however, certain factors can affect vaccine acceptance. The objective of this study was to determine whether religious fatalism and concern about new variants have a significant effect on the acceptance of COVID-19 vaccines. An explanatory study was conducted with 403 adults of legal age captured through non-probabilistic convenience sampling in vaccination centers in the 13 health networks of the Regional Health Directorate of Puno, Peru. Data were collected through a brief scale of religious fatalism, a scale of acceptance of vaccines against COVID-19 and a scale of concern about a new variant of COVID-19. The proposed model obtained an adequate fit. There was a negative effect of religious fatalism on vaccine acceptance, a positive effect of fatalism on vaccine rejection, a positive effect of concern about new variants on the acceptance of vaccines, and a positive effect of concern about new variants on vaccine rejection. These findings provide evidence for the usefulness of considering both religious fatalism and concern about new variants affect the intention to receive the COVID-19 vaccine in adults in southern Peru.

Sediment dispersal and basin evolution during contrasting tectonic regimes along the western Gondwanan margin in the central Andes

A >15-20 km-thick succession in southern Bolivia forms the most-complete stratigraphic record in western Gondwana. Upper Neoproterozoic–Carboniferous clastic rocks record ∼300 Myr of marine, nonmarine, and glacially influenced sedimentation in diverse basin systems generated by variable tectonic regimes along the western edge of Gondwana during active and passive-margin conditions. New provenance results help resolve key uncertainties regarding source regions and sediment dispersal patterns. The findings are integrated with spatial variations in stratigraphic thicknesses to evaluate regional patterns of basin subsidence, magmatism, and deformation during long-term evolution of the western Gondwanan margin in the central Andes.Detrital zircon U–Pb geochronological data for 17 sandstone samples reveal sedimentary input from Precambrian cratonic basement provinces and pre-Andean basement, magmatic arc, and fold-thrust belt source regions. The basement age signatures indicate derivation from the flanking Brasiliano (900-560 Ma) and Pampean (650-500 Ma) provinces to the south and east, and the distal Rio de la Plata craton (2400-2000 Ma) along the eastern South American margin ∼1000–1500 km to the southeast. Although the greater Amazonian craton was not a major contributor, subordinate Amazonian signatures from the Sunsás (1300-950 Ma) province to the east and northeast selectively fed the northern basin regions of the central Andes. Despite the lack of Paleozoic igneous rocks in Bolivia, detrital zircons of Ordovician age attest to the pre-Andean influence of the subduction-related Famatinian magmatic arc. Limited Devonian-Carboniferous igneous material was contributed locally from western pre-Andean highlands or regionally by axial northward transport from selected igneous sources in Argentina and Chile. Episodic recycling of Neoproterozoic–Paleozoic basin fill, including a sharp reappearance of Famatinian-age detritus, can be linked to periods of Paleozoic crustal shortening and foreland sedimentation ascribed to Famatinian, Ocloyic, Chañic, or Gondwanide phases of deformation.The spatial distribution of sediment sources along with temporal shifts in sediment routing highlight several stages in the paleogeographic evolution of the western Gondwanan margin preserved in the central Andes. Initial regional subsidence spanned a multiphase Neoproterozoic to early Paleozoic history of Rodinia breakup, Brasiliano-Pampean orogenesis, and post-orogenic back-arc extension prior to final late Paleozoic amalgamation of Gondwana. The early Paleozoic onset of subduction and Famatinian arc magmatism led to high-magnitude subsidence (>10–15 km) likely driven by Ordovician slab rollback in an extensional back-arc basin. Thereafter, intermittent Paleozoic contraction in a poorly understood pre-Andean system (best expressed in the Eastern Cordillera of Bolivia and neighboring segments of northern Argentina and southern Peru) generated transient topographic loads that produced superimposed flexural foreland and successor basin systems.

Extraction strategies and technological tradition at late pre-Hispanic quarries, southern Peru (ca. 1000–1532 CE)

Studies of Inka quarry operations have focused on large-scale quarries in the Inka imperial heartland, with emphasis on finishing techniques and geochemical sourcing. To assess diachronic variation in the technological organization of late pre-Hispanic building stone extraction, we compare survey data from the Chuquibamba District (Arequipa Region) – an Inka provincial context – and the Sacred Valley, a vital part of the Inka imperial heartland. Our sample (n = 41) includes small- and large-scale quarries that supplied material for Inka state and elite projects as well as local vernacular construction during the Late Intermediate Period and Late Horizon (ca. 1000–1532 CE). To chronologically contextualize quarry sites, we assess use periods based on scale, diagnostic technology, and building stone provenance. We deploy a multilinear approach using archaeological data, colonial chronicles and dictionaries, and analogies to ethnographic and modern cases to analyze the knowledge, decision-making process, and mechanics that facilitated material extraction. The results demonstrate that Inka building stone quarrying techniques developed out of widely shared vernacular knowledge and practice. This study articulates a new approach to late pre-Hispanic Andean architecture while providing a case study to evaluate the relationship between political organization and technological systems.

An Ensemble Approach of Feature Selection and Machine Learning Models for Regional Landslide Susceptibility Mapping in the Arid Mountainous Terrain of Southern Peru

This study evaluates the utility of the ensemble framework of feature selection and machine learning (ML) models for regional landslide susceptibility mapping (LSM) in the arid climatic condition of southern Peru. A historical landslide inventory and 24 different landslide influencing factors (LIFs) were prepared using remotely sensed and auxiliary datasets. The LIFs were evaluated using multi-collinearity statistics and their relative importance was measured to select the most discriminative LIFs using the ensemble feature selection method, which was developed using Chi-square, gain ratio, and relief-F methods. We evaluated the performance of ten different ML algorithms (linear discriminant analysis, mixture discriminant analysis, bagged cart, boosted logistic regression, k-nearest neighbors, artificial neural network, support vector machine, random forest, rotation forest, and C5.0) using different accuracy statistics (sensitivity, specificity, area under curve (AUC), and overall accuracy (OA)). We used suitable combinations of individual ML models to develop different ensemble ML models and evaluated their performance in LSM. We assessed the impact of LIFs on ML performance. Among all individual ML models, the k-nearest neighbors (sensitivity = 0.72, specificity = 0.82, AUC = 0.86, OA = 78%) and artificial neural network (sensitivity = 0.71, specificity = 0.85, AUC = 0.87, OA = 79%) algorithms showed the best performance using the top five LIFs, while random forest, rotation forest, and C5.0 (sensitivity = 0.76–0.81, specificity = 0.87, AUC = 0.90–0.93, OA = 82–84%) outperformed other models when developed using all twenty-four LIFs. Among ensemble models, the ensemble of k-nearest neighbors and rotation forest, k-nearest neighbors and artificial neural network, and artificial neural network and rotation forest outperformed other models (sensitivity = 0.72–0.73, specificity = 0.83–0.84, AUC = 0.86, OA = 79%) using the top five LIFs. The landslide susceptibility maps derived using these models indicate that ~2–3% and ~10–12% of the total study area fall within the “very high” and “high” susceptibility. The obtained susceptibility maps can be efficiently used to prioritize landslide mitigation activities.

La competencia portuaria entre Arica y Cobija en el advenimiento de la Confederación Perú-Boliviana

En la Bolivia decimonónica se vivió un largo conflicto portuario entre las fuerzas locales partidarias de utilizar Arica para dar salida a los productos bolivianos, centradas alrededor de La Paz, y aquellas que querían potenciar el puerto de Cobija, en el Litoral boliviano, sobre todo en Potosí y Chuquisaca. La formación de las fronteras internacionales trabó el tránsito por Arica, pero la dejadez y lejanía del Litoral impidió a Cobija constituirse como puerto nacional. En el artículo presente, se defiende que uno de los motivos para la construcción (y destrucción) de la Confederación Perú-Boliviana fue la búsqueda de una solución para el conflicto portuario, superando el obstáculo del uti possidetis fronterizo. La colección epistolar del presidente Andrés de Santa Cruz da testimonio de las medidas tomadas al respecto, y presenta al paceño Atanasio Hernández como ejemplo de los discursos de las fuerzas locales estudiadas.

New age constraints on the break-up of Rodinia and amalgamation of southwestern Gondwana from the Choquequirao Formation in southwestern Peru

Abstract The Choquequirao Formation is a >3 km-thick amphibolite-grade succession that outcrops in the Central Andes of southern Peru. To constrain its age and tectonostratigraphic setting, detrital zircon and metamorphic zircon, titanite, and rutile U–Pb isotopic analyses were conducted. Mantle-derived c. 640 Ma detrital zircons constrain the maximum age of the lower part of the succession and 550–490 Ma metamorphic zircon domains constrain its minimum age. The absence of early Paleozoic detrital zircons suggests that deposition predated early Paleozoic orogenesis in southwestern Gondwana. The close similarity of detrital zircon age spectra to those from sediments deposited on the Arequipa basement suggests that the Choquequirao Formation was deposited on the Arequipa Terrane. Metamorphic titanite dates are highly overdispersed, yet they overlap with c. 460 Ma peak metamorphism recorded by metamorphic zircon. Pb-loss pathways displayed by metamorphic titanite have a lower intercept that overlaps with c. 325 Ma metamorphic rutile, which corresponds to Hercynian orogenesis. A poorly constrained upper intercept of c. 510 Ma may correspond to Pampean and/or early Famatinian orogenesis. We interpret the Cryogenian–Ediacaran Choquequirao Formation as having been deposited during the opening of the Palaeo-Iapetus (Puncoviscana–Clymene) Ocean between eastern Arequipa and southern Kalahari prior to the subsequent collision with southwestern Amazonia during the Pampean Orogeny.

Mineral Texture Classification Using Deep Convolutional Neural Networks: An Application to Zircons From Porphyry Copper Deposits

AbstractThe texture and morphology of igneous zircon indicates magmatic conditions during zircon crystallization and can be used to constrain provenance. Zircons from porphyry copper deposits are typically prismatic, euhedral, and strongly oscillatory zoned which may differentiate them from zircons associated with unmineralized igneous systems. Here, cathodoluminescence images of zircons from the Quellaveco porphyry copper district, Southern Peru, were collected to compare zircon textures between the premineralization Yarabamba Batholith and the Quellaveco porphyry copper deposit. Quellaveco porphyry zircons are prismatic, euhedral, and strongly oscillatory zoned, whereas the batholith zircons are subhedral‐anhedral with weaker zoning. We adopt a deep convolutional neural network (CNN) approach to demonstrate that a CNN can classify Quellaveco porphyry zircons with high success. We trial several CNN architectures to classify zircon images: LeNet‐5, AlexNet and VGG, including a transfer learning approach where we used the weights of a VGG model pretrained on the ImageNet data set. The VGG model with transfer learning is the most effective approach, with accuracy and receiver operating characteristic‐area under curve (ROC‐AUC) scores of 0.86 and 0.93, indicating that a Quellaveco porphyry zircon CL image can be ranked higher than a batholith zircon with 93% probability. Visualizing model layer outputs demonstrates that the CNN models can recognize crystal edges, zoning, and mineral inclusions. We trial implementing trained CNN models as unsupervised feature extractors, which can empirically quantify crystal textures and morphology. Therefore, deep learning provides a tool for the extraction of information from large, imaged‐based petrographic data sets which can facilitate petrologic and provenance studies.

Hydrological impacts of dam regulation for hydropower production: The case of Lake Sibinacocha, Southern Peru

Study regionVilcanota-Urubamba river basin, Southern Peru. Study focusHydraulic infrastructure plays a fundamental role for energy production, drinking and irrigation water storage and flood control in regions with seasonal river flow. The high-Andean Lake Sibinacocha has been regulated since 1988 to increase energy production of the Machupicchu hydropower plant. In this study, river streamflow changes are evaluated by analyzing precipitation and discharge trends using indicators of hydrologic alteration and ecoflow for natural (1965–1987) and altered (1988–2016) flow regimes. New hydrological insights for the regionFor the altered flow regime, an ecodeficit of about 20% (compared to natural river flow) and an ecosurplus > 30% were found during the wet season (December-February) and dry season (June-August), respectively. These changes have reduced the risk of water shortage (dry season) and flood (wet season) and contribute to increasing water use including hydropower production, irrigation and drinking water. However, river alteration might lead to considerable impacts on riverine ecosystems.Despite major limitations related to data scarcity and complex environmental processes in the basin, our results highlight the usefulness of combined methods of hydrological alteration and ecoflow to effectively evaluate water regime changes in regulated basins. An integrated scientific approach is necessary to address uncertainties and develop meaningful future water availability scenarios that guide hydropower projects with improved water and energy security considering minimal impacts on human and natural systems.

The role of temple institutions in Wari imperial expansion at Pakaytambo, Peru

During the Andean Middle Horizon (CE 600–1000), the highland Wari emerged as an expansive power that formed the largest pre-Inka imperial project in the Andes. Although territorially discontinuous, the introduction of Wari state institutions to disparate regions of Peru knit together far-flung and diverse social groups. Recent excavations at Pakaytambo in southern Peru have uncovered a Wari ritual complex replete with a d-shaped temple, patio-group architecture, and monumental platform construction. The complex was established in the upper Majes-Chuquibamba drainage of Arequipa at ∼ 1700 masl and was strategically placed along a major pre-Inka road at the nexus of highland-coastal populations and socio-ecological zones. In this article, excavations at Pakaytambo are presented and discussed in terms of architectural canons, site chronology, and material studies in consideration to broader changes during the late Middle Horizon. d-shaped temples represent the most ubiquitous form of civic-ceremonial architecture related to Wari religious institutions and imperial ideology. Thus, Pakaytambo provides invaluable insights into the production of state authority through public ritual and performance in regions beyond a state heartland. A focus on institutions, their group members, norms, shared objectives, and archaeological patterning provides a middle-level unit of social analysis complimentary to high theory of the state.

The late Cenozoic evolution of the Humboldt Current System in coastal Peru: Insights from neodymium isotopes

The Humboldt Current System along the Pacific coast of South America creates one of the most productive ecosystems on Earth. To trace the origin of the water masses in this area, we measured neodymium isotope compositions (ԑNd) in tooth enameloid of two genera of coastal sharks from latest Oligocene to early Pleistocene strata in the Pisco and Sacaco basins in southern Peru. Most ԑNd values range from −4 to −1, with a strong negative excursion in the late Miocene (∼8–7 million years ago [Ma]) with values as low as −9.2. The overall trend of the ԑNd values resembles that of equatorial Pacific deep waters, though with an offset of about +2 ԑNd units until about 6 Ma. With a major input of hinterland weathering considered unlikely, we interpret this pattern as reflecting a modern-type upwelling regime, though with a lower contribution of Antarctic waters than today. Starting about 6 Ma, the contribution of Antarctic waters to the upwelling waters increased approximately to present-day levels, coincident with, and possibly driven by, increased Antarctic glaciation and the Andes reaching their present-day elevation, both of which likely enhanced the counter-clockwise circulation in the South Pacific Ocean. The negative excursion of ԑNd values in the Pisco/Sacaco basins ∼8–7 Ma coincides with a late Miocene biogenic bloom in the Pacific Ocean and elsewhere, and with a strongly increased northward bottom current observed on the Nazca Drift System just offshore our sampling area. Thus, the negative excursion of ԑNd values in the Pisco/Sacaco basins likely resulted from a southern sourced input of nutrient-rich, unradiogenic water, which could have been an important contributor to the biogenic bloom.