Cordillera De Research Articles

B-Value Maps for Some Volcanoes Worldwide: What Do We Learn?

Abstract We evaluate, using the method of Godano et al. (2022), the b-value 3D maps for some volcanoes worldwide: Cordillera de Guanacaste, Costa Rica; Etna, Italy; Hawaii, United States; Santorini, Greece; and Yellowstone, United States. The original method (using unstructured gridding in the process of building the cells of the volume) has been modified introducing a new technique for the estimation of the completeness magnitude mc based on the evaluation of the variability coefficient cv. This provides a very efficient estimation of mc. All the b-values distributions show an anomaly (larger than the others) associated with a hydrothermal system. This suggests that our method could be efficient in characterizing the rheological behavior and the temperature of the volcanic rocks.

First Red List of Ecosystems assessment of a tropical glacier ecosystem to diagnose the pathways towards imminent collapse

Abstract Tropical glaciers are rapidly disappearing, particularly in isolated mountain peaks below 5,000 m elevation. These glaciers are fundamental substrates for unique cryogenic ecosystems in high tropical environments where the ice, melting water and rocky substrate sustain microbiological communities and other meso- and macro-biota. This study uses the Red List of Ecosystems guidelines to diagnose the collapse of the tropical glacier ecosystem of the Cordillera de Mérida, Venezuela. We undertook the assessment with existing estimates of glacier ice extent, indirect historical estimates of ice mass balance and global mechanistic models of future ice mass balance. We complemented these with additional statistical analysis of trends and bioclimatic suitability modelling to calculate and predict rates of decline and relative severity of degradation in selected ecosystem indicators. The evidence suggests an extreme risk of collapse (Critically Endangered) because of a prolonged and acute reduction in ice extent and changes in climatic conditions that are leading to the complete loss of ice mass. The ice substrate has declined 90% in the last 20 years, and observed acceleration of the rate of decline suggests it will probably disappear within the next 5 years. Loss of ice substrate will trigger an immediate loss of supraglacial, englacial and subglacial biotic compartments and initiate a decades-long succession of forefield vegetation. However, ongoing inventories of native biota and monitoring of ecosystem transitions can provide valuable insights and lessons for other ecosystems facing similar risks. The Red List of Ecosystems assessment protocol provides a useful framework for comparative analysis of cryogenic ecosystems.

Phylogeographic patterns of Cyphocharax from trans-Andean rivers and northward expansion to lower Central America (Teleostei, Curimatidae).

Phylogenetic analyses of mitochondrial and nuclear data of 31 specimens of Cyphocharax from trans-Andean rivers support the presence of one lineage of Cyphocharax aspilos in Lago Maracaibo and three cryptic lineages of Cyphocharax magdalenae: (1) Cauca-Magdalena and Ranchería, (2) León and Atrato, and (3) Chucunaque-Tuira, Santa María, and Chiriquí basins of Central America. Results suggest that the Serranía del Perijá facilitated Late Miocene cladogenetic events, whereas post-Isthmian C. magdalenae expansion was enabled by gene flow across the lower Magdalena valley and Central American lowlands. Time-calibrated phylogenetics indicate that the C. magdalenae colonized lower Central America in the Pliocene (3.7 MYA; Ma), the divergence Atrato-Magdalena occurred in Late Pliocene (3.0 Ma) and the split Ranchería-Magdalena during the Middle Pleistocene (1.3 Ma). Updated geographic distribution data support the hypothesis that the Cordillera de Talamanca functions as a barrier to northward expansion of C. magdalenae in Central America.

New records of Dipsas welborni Arteaga & Batista, 2023, Gelanesaurus flavogularis (Altamirano-Benavides, Zaher, Lobo, Grazziotin, Sales-Nunes & Rodrigues, 2013), and Synophis insulomontanus Torres-Carvajal, Echevarría, Venegas, Chávez & Camper, 2015 in the Cordillera de Colán, Peru

A herpetological survey during recent expeditions to the foothills of the Cordillera de Colán in the Amazonas region of Peru resulted in new records and extensions of the geographical distribution of three poorly known species of reptiles: Dipsas welborni (family Colubridae), Gelanesaurus flavogularis (family Gymnophthalmidae), and Synophis insulomontanus (family Colubridae).

Two new species of <i>Telipogon</i> (Orchidaceae: Oncidiinae) from Costa Rica

The Neotropical genus Telipogon (Orchidaceae: Oncidiinae), comprising approximately 250 species, exhibits remarkable species diversity in the humid, montane forests of southern Central America and the Tropical Andes. Telipogon, when broadly defined, encompasses both the large-flowered species that mimic tachinid flies and the small-flowered species formerly classified under Stellilabium. In Costa Rica, this genus includes 55 species, with 16 classified as small-flowered species. While the large-flowered species of Telipogon (in the strict sense) have been taxonomically revised, the small-flowered species have yet to be the subject of a thorough taxonomic revision. Our research aims to partially fill this gap by focusing on a comparative morphological analysis of two novel small-flowered Telipogon species. We describe and illustrate Telipogon lateritius and T. muntzii, both discovered in the humid mid-elevation forest of the Caribbean watershed in Cordillera de Talamanca, Costa Rica. Telipogon lateritius is notable for its distinctive brick-colored flowers, featuring sepals, petals, and lips striped in chestnut brown; the lateral sepals connate into a triangular-ovate synsepal, complemented by sparse, stiff pubescence at the base of the lip. Telipogon muntzii, although closely resembling T. anacristinae, differs in its unique olive-green flowers, sparse trichomes on the lip, narrowly oblong lateral lobes of the column, and a helmet-shaped median lobe of the column exclusively covered by simple trichomes. This study provides new additions for a future taxonomic revision of Telipogon in Costa Rica.

Holocene hydroclimate in highland Costa Rica: new evidence from hydrogen and carbon isotopes in n‐alkanes of terrestrial leaf waxes in a 10 000‐year sediment profile

ABSTRACTWe conducted compound‐specific stable hydrogen (δD) and carbon (δ13C) isotope analysis on n‐alkanes from terrestrial leaf waxes preserved in a 10 000‐year sediment profile from Lago de las Morrenas 1 (9.4925° N, 83.4848° W, 3480 m), a glacial lake on the Chirripó massif of the Cordillera de Talamanca in Costa Rica. Our results demonstrate millennial‐scale variations in hydroclimate across the Holocene, with drier than average conditions in the highlands during the early Holocene, but with gradually increasing precipitation; mesic conditions during the middle Holocene with a gradual drying trend; and highly variable conditions during the late Holocene. This general pattern is punctuated by several centennial‐scale manifestations of global climate events, including dry conditions during the 8200, 5200 and 4200 cal a bp events and the Terminal Classic Drought (1200–850 cal a bp). Our δ13C analyses demonstrate that carbon isotope signals are responding to changes in hydroclimate at the site and reinforce prior interpretations of a stable páramo plant community that established following deglaciation and persisted throughout the Holocene. The shifts in hydroclimate inferred from analyses of n‐alkanes in Lago de las Morrenas 1 sediments show correspondence with charcoal records in multiple lakes, with fires most common during drier intervals.

First evidence of prickly shark, Echinorhinus cookei Pietschmann 1928, aggregation on seamounts in the eastern Pacific, Panama.

In May 2022, twelve prickly sharks, Echinorhinus cookei Pietschmann 1928, were sighted at 151-350 m depth in the Cordillera de Coiba seamounts, Pacific Panama. This discovery expands our knowledge of the distribution and habitat use of this rare deep-sea species. It underscores the potential significance of the Cordillera de Coiba seamounts, an offshore marine protected area, as a critical habitat for E. cookei, a species threatened by commercial fishing. Although unverified reports exist on its presence in the tropical eastern Pacific, this publication represents the first documented record of live specimens of E. cookei in Panama.

A new dwarf gecko of the genus Pseudogonatodes (Squamata: Sphaerodactylidae) from the eastern slope of the Andean Cordillera de Mrida in northern South America.

Pseudogonatodes is a poorly known genus of small bodied, diurnal, ground-dwelling geckos widely distributed in northern South America. No additional species have been described in over two decades. Herein we describe a new species from the eastern slope of the Cordillera de Mrida in the Venezuelan Andes. The new species is readily diagnosable morphologically from the other seven recognized species of Pseudogonatodes by having a single postnasal scalea putative autapomorphy. Furthermore, it is characterized by a unique combination of phenotypic characters that includes granular dorsal scales, three large postrostrals, five to six loreals, mental U-shaped, four to six postmentals, 2629 ventrals between anterior levels of fore- and hind limbs, third lamella under fourth toe not distinctly enlarged, and subcaudal pattern 11. In addition to characterizing the external morphology, we present a description of the skull, based on 3D digital models reconstructed from high resolution computed microtomography scans. The discovery of this new species highlights the still underestimated diversity of this group of Neotropical dwarf geckos and underscores the need for further studies on its systematics and taxonomy.

Two new species of wood lizards (Hoplocercinae: Enyalioides) from Cordillera de Colán in north-eastern Peru

Two new species of wood lizards (Hoplocercinae: Enyalioides) from Cordillera de Colán in north-eastern Peru

Epidendrum scandens: an unusual new orchid species endemic to the Cordillera de Talamanca in Costa Rica

We describe and illustrate a new species of Epidendrum from the montane forests on the Cordillera de Talamanca, in Costa Rica. Epidendrum scandens is unusually among the ‘Rugosum subgroup’ of ‘Ramosum group’ in the plants forming large mats, composed of elongate, scandent, climbing stems that are notoriously branching and flexuous, becoming liana-like. The 2–3-flowered inflorescence is extremely discrete in relation to the stem, it bears typical yellowish-green flowers partially hidden by large floral bracts. The triangular lip is unusual in the conspicuous apical thickening. A taxonomic description, illustration, distribution map and conservation status are provided for the new species.

Vulnerability of elevation-restricted endemic birds of the Cordillera de Talamanca (Costa Rica and Panama) to climate change

ABSTRACT Animals endemic to tropical mountains are known to be especially vulnerable to climate change. The Cordillera de Talamanca (Costa Rica and Panama) is a geographically isolated mountain chain and global biodiversity hotspot, home to more than 50 endemic bird species. We used eBird community science observations to predict the distributions of a suite of 48 of these endemic birds in 2006–2015, and in 2070, under four climate change scenarios. Species distributions were predicted using program Maxent, incorporating elevation, satellite derived habitat data, and WorldClim climate variables. Model fit, as assessed by Area under the Receiver Operator Curve (AUC), was very high for most species, ranging from 0.877 to 0.992 (mean of 0.94). We found that most species are predicted to undergo range contractions by 2070, with a mean of 15% under modest climate change (RCP 2.6) up to a mean of 40% under more severe climate change (RCP 8.5). Most of the current ranges of these species are within existing protected areas (average of 59% in 2006–2015), and with prospective range contractions, the importance of these protected areas is forecast to increase. We suggest that these predicted range declines should elevate conservation concerns for this suite of species, and vigilance, in the form of better population monitoring, is urgently needed.

TWO NEW FROGS (ELEUTHERODACTYLUS) FROM THE SERRANÍA DE PERIJÁ, COLOMBIA

Two new species of the genus Eleutherodactylus are described from the northern part of the Serranía del Perijá. One species is similar to a species known from the Cordillera de Mérida and the other resembles a species known from the Cordillera Oriental in Norte de Santander and Santander.

Understanding the initial upper plate architecture and shortening distribution in subduction-related orogens: Insights from the Central Andean forearc

The Central Andean Forearc (26°S) structure has been debated for decades. Extension, contraction, and strike-slip deformation are commonly proposed mechanisms to explain the main tectonic elements exposed in the Domeyko Cordillera, Salar de Pedernales Basin, and others partially exposed in the Coastal Cordillera and Central Depression. Although pre-Andean tectonic inheritance seems to have influenced the style and mechanisms of mountain uplift in this region, its current architecture and the way it controlled the shortening distribution during orogen evolution are highly speculative, mainly because some of the tectonic provinces in this segment consist of covered areas (e.g., the Central Depression). To address this question, we present the first balanced cross-section and pre-shortening restoration of the Andean forearc at 26°S. We integrated new field data from the Coastal and Domeyko cordilleras with well data and re-interpreted 2D seismic profiles from the Salar de Pedernales Basin to construct a regional-scale cross-section of 210 km length from the Coastal Cordillera to the current Volcanic Arc, thus showing a two-dimensional (2D tectonic model to help understand the tectonic evolution of the western Central Andes. The results indicate a pre-shortening architecture dominated by Late Permian–Jurassic half-graben structures related to continental rifting. West- and east-dipping basement-rooted normal faults controlled rift-related basins, along which kilometric-scale marine and continental syn-rift sequences accumulated. During early Andean orogenesis, the normal faults were partially inverted, and large anticlines developed at the hanging wall faults, which Upper Cretaceous progressively covered to Paleocene synorogenic units. This suggests that the initial topographic relief in the region resulted from a basin inversion. During the more advanced stages of orogenesis (mid-Cenozoic), new reverse and thrust faults (or shortcut faults) were created, which connected upward with incompetent stratigraphic units and facilitated the propagation of localized fold-and-thrust belts in the eastern Domeyko Cordillera and Salar de Pedernales basins. A minimum of 16.3 km of W-E shortening was reported; however, nearly 11 km was accommodated by the newly created thrusts, indicating that these were most relevant to mountain building.

Origin of old saline groundwater in the deep coastal formations of the Atacama Desert region: Consideration of lithium, boron, strontium and uranium isotopes contents

This paper presents a multi-isotopic study to investigate the origin of saline groundwater in the Cordillera de la Costa, in the arid Atacama Desert region in northern Chile. Understanding the origin of deep saline groundwater can be challenging using only hydrogeochemical and common isotope methods. New 87Sr/86Sr, δ11B, δ7Li, and 234U/238U values of dissolved salts have been added to previously known chemical and isotopic compositions of groundwater, inorganic dissolved carbon, and sulfate. In this extremely arid area, the chemical and isotopic compositions of coastal springs primarily reflect the concentration of salts from atmospheric wet and dry deposition, which accumulate in the topsoil and dissolve during the occasional heavy rainfall events. These events recharge the aquifer with sodium-chloride type, high salinity water, with rock weathering contributing minimally to the chemical composition of groundwater. However, high salinity water of the calcium chloride and sodium-calcium chloride types in the deep fractured aquifer have a significantly different chemical and isotopic composition. In this investigation, it has been concluded that the salinity of these last waters is due to remnants of ancient marine water, mineral alteration and interaction with predominantly andesitic volcanic rocks in the Cordillera de la Costa. The deep saline groundwater has δ11B values between 17.3‰ and 20.7‰, and 87Sr/86Sr values below 0.706, suggesting mixing with recharge groundwater. The δ7Li composition of the deep groundwater varies between 23.5‰ and 31.5‰, pointing to a contribution of salts of marine origin and mineral alteration. However, the low Li concentrations relative to B in recharge water and in deep groundwater shows a preferential Li removal from pore water. Uranium and uranium isotopes data are limited to shallow groundwater due to the very low U concentrations in deep groundwater following reduction of U, and point to enhanced water–rock interaction in a rock-dominated environment. The dissolution of old buried saline deposits at shallow depth as a source of salinity is ruled out.

A reappraisal of the distribution of the Yellow-headed Manakin (Chloropipo flavicapilla) in Colombia and Ecuador

The Yellow-headed Manakin (Chloropipo flavicapilla) is a rare and threatened species that is thought to occur between the Andes of Colombia and northeastern Ecuador. However, only three records support the presence of C. flavicapilla in Ecuador: a 19th-century specimen from Hacienda Mapoto, Tungurahua province, and two undocumented field observations from the early 1990s — one from Cordillera de Guacamayos and one from Volcán Sumaco. I investigated these records and found that the Mapoto specimen is a Green Manakin (Cryptopipo holochlora) deposited in the Museum and Institute of Zoology, Polish Academy of Sciences (MIZ 22050). The correct specimen identity was reported by Hellmayr (1929), but his notes were overlooked. The two undocumented sightings occurred in well-surveyed areas populated with eBird hotspots that are frequently visited by birders. Furthermore, there are no publicly available records of C. flavicapilla for these locations or anywhere else in Ecuador. Lastly, I analyzed the species distributional limits in southern Colombia. Two biogeographical barriers limit its distribution to northern Ecuador: (1) The Patía Valley in the western Andes and (2) the Colombian Massif in the central and eastern Andes. In conclusion, there is no tangible evidence that C. flavicapilla has been recorded in Ecuador, and based on its current distribution, it should be considered endemic to Colombia.

A new species of Andean frog of the genus Phrynopus (Anura: Strabomantidae) from southeastern Peru.

The Cordillera de los Andes is one of the most important regions for biodiversity. Among amphibians, many endemic species of terrestrial-breeding frogs have recently been discovered. Herein we describe Phrynopus sancristobali from the Andes of southeastern Peru based on molecular and morphological data. The new species is known from the ecotone between humid puna and montane forest at 3910 m a.s.l. on the left side of the Apurímac Valley in the Department of Ayacucho. The new species differs from congeners by having dorsum bearing pustules and light brown with dark brown reticulations surrounding the areolas, and coloration consisting of flanks golden brown with gray or dark brown marks, palms pale orange, soles deep orange, toes IV and V dark brown in dorsal and ventral view, belly cream to yellow with gray to light brown marks, and groin and throat deep orange. The snout-vent length (SVL) is 20.7 and 22.2 in two females, and 19.5 mm in one male. According to our phylogeny inferred using Maximum Likelihood with a concatenated dataset of three mitochondrial and two nuclear genes, P. sancristobali is sister taxon of P. apumantarum, recently described from Department Huancavelica. Our description extends the known geographic range of Phrynopus 73 km to the south, and P. sancristobali is the only species in the genus known to occur south of the Mantaro River, whose deep valley is hypothesized to be a biogeographic barrier for high-Andean organisms. The discovery of P. sancristobali confirms the high levels of endemism and beta diversity of Phrynopus in the moist puna grasslands and montane forests of the high Andes of Peru, and suggests that further work will reveal the presence of additional species in southern Peru.

Comparing the biotite and amphibole single-mineral thermobarometric models: A case study from the Cordillera de San Buenaventura volcanic rocks, Puna plateau of Central Andes (Argentina)

We applied a new thermobarometric model based solely on biotite composition to the trachyandesitic to rhyolitic volcanic rocks of the Cordillera de San Buenaventura, a long-lived magma plumbing system (spanning from the Late Miocene to the Holocene) in the Southern Puna plateau (Central Volcanic Zone of the Andean Cordillera). Within these rocks, biotite is a widespread mineral phase found in association with amphibole, as either glomerocrysts, mutual inclusions, or free phenocrysts. This allowed us to compare the biotite-only model with other thermobarometric estimates that rely on amphibole, mineral-melt, and mineral-mineral composition. Our goal was to determine the conditions of formation for biotite and its petrogenetic significance in the evolution of the Cordillera de San Buenaventura magma system. The results indicate that biotite crystallization occurred mainly at middle-to upper-crustal depths (2.1–5.1 kbar) with temperatures below 1000 °C (763–919 °C). The biotite-only T-P estimates for individual lithologies are consistent with those obtained using the amphibole-only model, and this is particularly true for the thermometer. Furthermore, our findings align with the existing petrogenetic models, which suggest extensive fractional crystallization, and with the analyses of mineral textures, that indicates events of magma replenishment. Therefore, our results support the validity of the biotite-only model and its ability to elucidate magmatic processes, including magma differentiation via fractional crystallization, magma ascent and cooling, and magma replenishment and/or mixing events.

Satellite-Based Damage Assessment Following a Wildfire Event in Cordillera de Sama Bolivia

Satellite-Based Damage Assessment Following a Wildfire Event in Cordillera de Sama Bolivia

The birth of the Gondwanide arc: Insights into Carboniferous magmatism of the North Patagonian Andes (Argentina)

New geological, structural, and geochemical information was obtained for the late Paleozoic basement of the North Patagonian Andes. The studied rocks are mainly formed by foliated diorites and gabbro-diorites with a primitive continental arc signature, according to trace elements patterns. Similar petrological and structural characteristics, together with previously reported ages between ca. 330 and 323 Ma, permit the correlation of these rocks with plutonic bodies located in the North Patagonian Andes, North Patagonian Massif and Cordillera de la Costa of Chile, documenting the onset of Gondwanide subduction along the proto-Pacific margin of Gondwana between ca. 37 and 45°S. Geochemical and geochronological data, together with field evidence, suggest mafic magma replenishment during the construction of this large batholith. The presence of sheeted zones and magmatic fabrics allow to interpret pluton emplacement in a highly coupled system linked with a tectonically active setting, under pressure conditions of ca. 6 ± 1 Kbar.

The rise and fate of a long-lived deep crustal ‘hot zone’ beneath the neogene-quaternary Cordillera de San Buenaventura in the Southern Puna Plateau (NW Argentina)

ABSTRACT Arc magmatism plays a key-role in the growth and differentiation of continental crust. In particular, the prolonged magmatic flux events control the genesis of deep crustal hot zones where magma accumulation and fractionation favour the continental arc crust evolution and geochemical stratification. In this view long-lived magmatic systems located in arc domains, with their erupted products spanning from basalts to rhyolites are formidable archive for the understanding the evolution of transcrustal magmatic plumbing systems and the construction of a stratified continental crust. This study focuses on the long-lived (ca. 9 Ma) Miocene-Holocene Cordillera de San Buenaventura volcanic system in the Southern Puna Plateau (NW Argentina), a unique natural laboratory where exploring the building up of MASH-zones (or deep crustal ‘hot zones’) and related sustained volcanism. Synthesis of new and published data, together with new thermobarometry and fractional crystallization modelling, indicates a cyclic scenario with mantle melts undergoing fractional crystallization dominated incipient and waning stages alternate to major mafic magma recharge events during the building up phase of the MASH-zone. This magmatic scenario is also discussed in the light of the coeval geodynamic framework dominated by the subduction of the Nazca plate and the eastward migration of the frontal arc magmatism.