Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an ...Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.展开更多
The páramo of the Northern Andes provide critically important ecosystem services to the Northern Andean region in the form of water provisioning and carbon sequestration, both of which are a result of the pá...The páramo of the Northern Andes provide critically important ecosystem services to the Northern Andean region in the form of water provisioning and carbon sequestration, both of which are a result of the páramo?s organic-rich soils. Little is known, however, about the hydro-geomorphic characteristics of the rivers that drain these ecosystems. With impending plans for widespread hydro-development and increasing implementation of carbon-sequestering compensation for ecosystem services programs in the region it is imperative that we develop a thorough understanding of the hydrogeomorphic role that rivers play in this unique ecosystem. The objective of this study was to quantify bank erosion along an Amazonian headwater stream draining a small, relatively undisturbed páramo catchment to gain a better understanding of the natural erosion regime and the resulting sediment contributions from this unique ecosystem. This study implemented a combination of field, laboratory, and Geographic Information Systems techniques to quantify bank erosion rates and determine a bank erosion sediment yield from the Ningar River, a small páramo catchment(22.7 km^2) located in the eastern Andean cordillera of Ecuador. Results show that bank erosion rates range from 3.0 to ≥ 390.0 mm/yr, are highly episodic, and yield at least 487 tons of sediment annually to the Ningar River. These results imply that 1) páramo ecosystems substantially contribute to the sediment load of the Amazon River basin; 2) bank erosion is a potentially significant flux component of basin-scale carbon cycles in páramo ecosystems; and 3) hydrologic alteration campaigns(dam building) will likely critically alter these contributions and concomitantly disconnect a critical source of sediment and nutrients to downstream ecosystems.展开更多
The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geol...The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic(U-Pb and^(40)Ar/^(39)Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas(～47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene-late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Marquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene-Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San Jose Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene-lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early-middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.展开更多
We investigate the geology of Altar North(Cu-Au) and Quebrada de la Mina(Au) porphyry deposits located in San Juan Province(Argentina), close to the large Altar porphyry copper deposit(995 Mt,0.35% Cu, 0.083 g/t Au), ...We investigate the geology of Altar North(Cu-Au) and Quebrada de la Mina(Au) porphyry deposits located in San Juan Province(Argentina), close to the large Altar porphyry copper deposit(995 Mt,0.35% Cu, 0.083 g/t Au), to present constraints on the magmatic processes that occurred in the parental magma chambers of these magmatic-hydrothermal systems. Altar North deposit comprises a plagioclase-amphibole-phyric dacite intrusion(Altar North barren porphyry) and a plagioclaseamphibole-biotite-phyric dacite stock(Altar North mineralized porphyry, 11.98 ± 0.19 Ma). In Quebrada de la Mina, a plagioclase-amphibole-biotite-quartz-phyric dacite stock(QDM porphyry,11.91±0.33 Ma) crops out. High Sr/Y ratios(92-142) and amphibole compositions of Altar North barren and QDM porphyries reflect high magmatic oxidation states(fO_2= NNO+1.1 to+1.6) and high fH_2O conditions in their magmas. Zones and rims enriched in anorthite(An_(37-48))), SrO(0.22-0.33 wt.%)and FeO(0.21-0.37 wt.%) in plagioclase phenocrysts are evidences of magmatic recharge processes in the magma chambers. Altar North and Quebrada de la Mina intrusions have relatively homogeneous isotopic compositions(^(87)Sr/^(86)Sr_(t)= 0.70450-0.70466, ε_(ND)(t) = +0.2 to +1.2) consistent with mixed mantle and crust contributions in their magmas. Higher Pb isotopes ratios(^(207)Pb/^(204)Pb=15.6276-15.6294) of these intrusions compared to other porphyries of the district, reflect an increase in the assimilation of high radiogenic Pb components in the magmas. Ages of zircon xenocrysts(297,210,204,69 Ma) revealed that the magmas have experienced assimilation of Miocene, Cretaceous, Triassic and Carboniferous crustal rocks.Fluids that precipitated sulfides in the Altar deposit may have remobilized Pb from the host rocks, as indicated by the ore minerals being more radiogenic(207Pb/204 Pb = 15.6243-15.6269) than their host intrusions. Au/Cu ratio in Altar porphyries(average Au/Cu ratio of 0.14 ×10^(-4)by weight in Altar Central)is higher than in the giant Miocene porphyry deposits located to the south: Los Pelambres, Rio Blanco and Los Bronces(Chile) and Pachon(Argentina). We suggest that the increase in Au content in the porphyries of this region could be linked to the assimilation of high radiogenic Pb components in the magmas within these long-lived maturation systems.展开更多
Páramo is a term used to describe tropical alpine vegetation between the continuous timberline and the snow line in the Northern Andes. Páramo environments provide important species habitat and ecosystem ser...Páramo is a term used to describe tropical alpine vegetation between the continuous timberline and the snow line in the Northern Andes. Páramo environments provide important species habitat and ecosystem services. Changes in spatial extent of the páramo ecosystem at Pambamarca in the Central Cordillera of the northern Ecuadorian Andes were analysed using multi-temporal Landsat TM/ETM+ satellite data. The region suffered a loss of 1826.6 ha or 20% of the total area at a rate of 100 ha/annum during 1988-2007 period. It is found that permanent páramo cover decreased from 8350 ha in 1988 to 5864 ha in 2007 at a fairly constant rate(R2=0.94). This loss is attributed to expansion of commercial agriculture and floriculture in the valleys coupled with increased population pressure. Land at higher elevations has been cleared for small scale agriculture. Loss of the páramo ecosystem will exert a number of negative impacts on ecosystem services and livelihoods of the local population at Pambamarca.展开更多
The most heavily glacierized tropical range in the world– the Peruvian Cordillera Blanca-has been losing ice since the end of the Little Ice Age(LIA).In this study,the decline of the Churup glacier(9°28’18"...The most heavily glacierized tropical range in the world– the Peruvian Cordillera Blanca-has been losing ice since the end of the Little Ice Age(LIA).In this study,the decline of the Churup glacier(9°28’18"S;77°25’02"W)and associated processes were documented employing multi-proxy approach including the analysis of remotely sensed images(1948-2016),the Schmidt hammer rock test and lichenometric dating.It is shown that Churup glacier has lost the vast majority of its estimated LIA extent(1.05±0.1 km^2;45.0×10^6-57.4×10^6 m^3).The rate of glacier retreat is documented to vary in space(SE,SW and NW-facing slopes)and time,with the peak between 1986 and 1995.With an area of 0.045 km^2 in 2016,it is expected that the complete deglaciation of the Churup valley is inevitable in the near future.Recently(post-LIA)exposed bedrock surfaces have shown higher R-values(54.2-66.4,AVG 63.3,STDEV 2.9)compared to pre-LIA exposed surfaces(46.1-59.3,AVG 50.1,STDEV 4.9),confirming the links to the duration of rock weathering.The Lichenometric dating is applied to recently exposed areas and elevations above 4800 m a.s.l.,revealing only limited reliability and agreement with the age of deglaciation estimated from remotely-sensed images in such an environment.展开更多
Many Andisols of the Andes have been disturbed by traditional potato-based rotation agriculture disrupting soil structure, water retention capacity and organic matter content. This study was undertaken to investigate ...Many Andisols of the Andes have been disturbed by traditional potato-based rotation agriculture disrupting soil structure, water retention capacity and organic matter content. This study was undertaken to investigate the contribution of conservation farming technology or reduced tillage in potato-based rotations in the Colombian Andes in order to rehabilitate total and aggregated soil organic C in disturbed organic matter-rich Andisols. Soils were sampled from farms with 7-year of reduced tillage and farms with conventional farming practices. Ultrasound energy was applied to samples to disrupt aggregation and total soil C was determined in order to investigate the amount of carbon held inside the aggregates of different soil size classes. Results indicated that reduced tillage in potato-based crop rotations increased the soil C concentration and average C content in the whole profile (≈117 cm depth) by 50 and 33% (1636 t C ha?1 vs. 1224 t C ha?1), respectively, as compared to conventional farming practices. Carbon content increased 177% in the subsoil (A2 horizon, 78 -117 cm depth, from 215 to 596 t?ha?1), although most of the soil C was in the A1 horizon (between 0 -78 cm average thickness, 1097 t?ha?1). These increases show that reduced tillage enhances C stores in Andisols which are already high in organic matter. In addition, C in aggregates represented more than 80% of the total organic matter and it was positively affected by conservation practices. The C increase was preferential in the smaller macroaggregates (展开更多
Several orogenic cycles of mountain building and subsequent collapse associated with periods of shallowing and steepening of subduction zones have been recognized in recent years in the Andes.Most of them are characte...Several orogenic cycles of mountain building and subsequent collapse associated with periods of shallowing and steepening of subduction zones have been recognized in recent years in the Andes.Most of them are characterized by widespread crustal delamination expressed by large calderas and rhyolitic flare-up produced by the injection of hot asthenosphere in the subduction wedge.These processes are related to the increase of the subduction angle during trench roll-back.The Payenia paleoflat-slab,in the southern Central Andes of Argentina and Chile(34°—37°S) recorded a complete cycle from crustal thickening and mountain uplift to extensional collapse and normal faulting,which are related to changes in the subduction geometry.The early stages are associated with magmatic expansion and migration,subsequent deformation and broken foreland.New ages and geochemical data show the middle to late Miocene expansion and migration of arc volcanism towards the foreland region was associated with important deformation in the Andean foothills.However,the main difference of this orogenic cycle with the previously described cycles is that the steepening of the oceanic subducted slab is linked to basaltic flooding of large areas in the retroarc under an extensional setting.Crustal delamination is concentrated only in a narrow central belt along the cordilleran axis.The striking differences between the two types of cycles are interpreted to be related to the crustal thickness when steepening the subducting slab.The crustal thickness of the Altiplano is over 60-80 km,whereas Payenia is less than 42 km in the axial part,and near 30 km in the retroarc foothills.The final extensional regime associated with the slab steepening favors the basaltic flooding of more than 8400 km^3 in an area larger than 40,000 km2,through 800 central vents and large fissures.These characteristics are unique in the entire present-day Andes.展开更多
Communities in developing country mountain areas,in part due to their remoteness,find themselves excluded from social,political and economic systems; and excluded from access to resources. This paper aims to study the...Communities in developing country mountain areas,in part due to their remoteness,find themselves excluded from social,political and economic systems; and excluded from access to resources. This paper aims to study the impact of information and communication technologies (ICTs) on remoteness and exclusion. It utilises two models - the resource movement framework,and the "information chain" - to analyse a telecentre in one district of mountainous Huancavelica,Peru's poorest region,set in the high Andes. It finds ICTs enabling new and positive resource flows for the two key user groups:teenaged school students and young farmers. These help to maintain social networks. They also support information searches that have improved agricultural practice where other information chain resources have been available. But non-use and ineffective use of the telecentre are found where information chain resources are lacking. ICTs have some impacts on intangible elements of remoteness. In this particular example,they also offer access to some previously-excluded resources. But they have not really addressed the systematic exclusions faced by mountain communities. And they so far appear to be a technology of inequality; favouring those residents who begin with better resource endowments.The paper concludes by offering some recommendations for mountain ICT project practice.展开更多
This paper presents preliminary results of three-dimensional thermo mechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the centra...This paper presents preliminary results of three-dimensional thermo mechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes(16°S-26°S) up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker-Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area.In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters(e.g. viscosity, fault friction, velocity, shear heating) on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing computational time.展开更多
This paper discusses participatory research in the Andes and presents a case study in Cotacachi, Ecuador, where sustainability scientists and indigenous people seek common ground in their respective but drastically di...This paper discusses participatory research in the Andes and presents a case study in Cotacachi, Ecuador, where sustainability scientists and indigenous people seek common ground in their respective but drastically different research and social agendas. Participatory research based on Andean experiences pre-dated and inspired much of the later international movement in agriculture, health, and conservation. Andean communities have a long history in demanding that outsiders address the needs of the community as a condition for carrying out scientific or applied activities. What an Andean community, however, sees as relevant may or may not be within the rubric of ‘participatory research’ as it is practiced throughout much of the world. In fact, overzealous participatory researchers are just as bothersome as their predecessors bearing long questionnaires. More important to Andean people is an equitable relationship with researchers and developers in which exchanges of value are made. A distinction between ‘enriching’ and ‘extractive’ research is drawn. In the case of the SANREM project in Cotacachi, Ecuador, scientists carried out enriching research activities of interest to local people as a wayto generate social capital for conducting basic research which does not have an obvious, immediate local benefit. The requested research did not have a conventional participatory methodology but provided valuable products (educational opportunity, germplasm, community visualization tools, and information) to the indigenous community in exchange for time and resources to conduct research on more basic natural resource questions. We argue that in the Andean context the key to reconciling the needs of scientists and of local needs is seeking new forms of equitable collaboration which reach beyond the present and now somewhat tired discourse of ‘participation’.展开更多
Projections of climate change are essential to guide sustainable development plans in the tropical Andean countries such as Peru. This study assessed the projections of precipitation and potential evaporation, rain er...Projections of climate change are essential to guide sustainable development plans in the tropical Andean countries such as Peru. This study assessed the projections of precipitation and potential evaporation, rain erosive potential, and precipitation concentration in the Mantaro River Basin, in the Peruvian Andes, which is important for agriculture and energy production in Peru. We assumed the Intergovernmental Panel on Climate Change(IPCC)A_1B greenhouse gas emission scenario and simulated the global climate change by the HadCM_3 global climate model. Due to the steepness of the mountain slopes and the narrowness of the river valley, this study uses the downscaling of the global model simulations by the regional Eta model down to 20-km resolution. The downscaling projections show decrease in the monthly precipitation with respect to the baseline period, especially during the rainy season,between February and April, until the end of the 21st century. Meanwhile, a progressive increase in the monthly evaporation from the baseline period is projected. The Modified Fournier Index(MFI) shows a statistically significant downward trend in the Mantaro River Basin, which suggests a possible reduction in the rain erosive potential. The Precipitation Concentration Index(PCI) shows a statistically significant increasing trend, which indicates increasingly more irregular temporal distribution of precipitation towards the end of the century. The results of this study allow us to conclude that there should be a gradual increase in water deficit and precipitation concentration. Both changes can be negative for agriculture, power generation, and water supply in the Mantaro River Basin in Peru.展开更多
A molecular phylogenetic analysis of most of the species of Perezia reveals that,as traditionally defined,the genus is not monophyletic with two species more closely related to Nassauvia than to Perezia.In addition,ou...A molecular phylogenetic analysis of most of the species of Perezia reveals that,as traditionally defined,the genus is not monophyletic with two species more closely related to Nassauvia than to Perezia.In addition,our results show that Burkartia(Perezia) lanigera is related to Acourtia and is the only member of that clade in South America.The remaining species are monophyletic and show a pattern of an early split between a western temperate and an eastern subtropical clade of species.Within the western clade,the phylogeny indicates a pattern of diversification that proceeded from southern,comparatively low-elevation habitats to southern high-elevation habitats,and ultimately into more northern high-elevation habitats.The most derived clades are found in the high central Andes,where significant radiation has occurred.展开更多
In the summer of 2010/2011 Chile suffered the third most severe energy and water supply crisis in only one decade.This may be surprising as the Andes which accompany the country along 4,200 km are a water tower and co...In the summer of 2010/2011 Chile suffered the third most severe energy and water supply crisis in only one decade.This may be surprising as the Andes which accompany the country along 4,200 km are a water tower and could provide more electricity and water than needed.On top of that,it has to be mentioned that Chile also counts with sunny and windy climates and with excellent geothermal energy resources and thus has a huge potential as far as renewable energies are concerned.After analyzing the existing natural conditions,the infrastructure and the present challenges of climate change,it has to be asked in which way Chile can make use of this potential in the near future,considering the legal and political situation and the technological opportunities.It seems that the resources are still hidden in the Andes,and only the key is missing to realize the country's natural potential.This research has been based on the analysis of existing literature,media,quantitative data from government institutions and other antecedents obtained by the authors in field work done in the South of Chile in 2010.The added value of this compilation lies in the comprehensive perspective,linking the knowledge of climatologists,hydrologists,mountain researchers and energy experts in order to support a sustainable energy and water supply for the future in Chile.From this present research,it can be concluded that Chile necessarilyhas to adopt new energy-related strategies,particularly those aimed at diminishing the strong dependence on traditional sources of energy and establishing new techniques and technologies for generating electricity and utilizing the vast potential that the country is ready to offer,such as that provided by the Andes along 4,200 kilometers.展开更多
Due to their ecological disadvantages,many mountain regions have experienced land-use abandonment and shrub encroachment on former grassland at higher altitudinal zones—especially during recent decades of urbanizatio...Due to their ecological disadvantages,many mountain regions have experienced land-use abandonment and shrub encroachment on former grassland at higher altitudinal zones—especially during recent decades of urbanization. But does this trend also apply to the hinterland of urban settlements? By using the Southern Colombian example of Popayán, a medium-sized city located in the Northern Andes, we can show that the landscape changes observed between 1989 and 2010 can hardly be related to agricultural abandonment. Hypsometric variations of land-cover change indicate that, until 2001, woods or shrubland expanded faster at the lower altitudinal range adjacent to the city than at the more remote higher zones. In contrast, after 2001 grassland areas increased on former woods or shrubland at all altitudinal belts. Both periods thus present developments that can be interpreted as the result of land-use expansion below 2000 m asl and land-use persistence in the tierra fría of the mountain city's hinterland.展开更多
The nuclear ribosomal ITS region and the chloroplast trnL-trnF (trnLF) intergenic region were se-quenced for 45 accessions of Paranephelius and six accessions of Pseudonoseris, the two genera of the subtribe Paranephe...The nuclear ribosomal ITS region and the chloroplast trnL-trnF (trnLF) intergenic region were se-quenced for 45 accessions of Paranephelius and six accessions of Pseudonoseris, the two genera of the subtribe Paranepheliinae (Liabeae, Asteraceae) distributed in the alpine regions of the Andes. This data set was used to estimate relationships between these genera and within each genus to aid in evaluating morphological variation and classification. Our results with both ITS and trnLF markers support the monophyly of subtribe Paranephelii-nae, and place Pseudonoseris discolor as the first diverged taxon sister to the clade containing Paranephelius. Pseudonoseris szyszylowiczii exhibited intraspecific divergence supporting intergeneric hybridization between Pseudonoseris and Paranephelius. Within Paranephelius, genetic divergence is low and not adequate to fully resolve phylogenetic relationships at the species level, but two genetically and morphologically recognizable groups were revealed by the ITS data. Several accessions possessing multiple ITS sequences represent putative hybrids between the two groups. These putative hybrids have caused some taxonomic confusion and difficulties in establishing species boundaries in Paranephelius. The divergence time estimates based on ITS sequences indi-cated that the stem of subtribe Paranepheliinae dates to 13 million years ago, but the diversification of the crown clade of the extant members began in the early Pleistocene or late Pliocene, perhaps associated with the uplift of the Andes and the climatic changes of global cooling.展开更多
Climate data of mean monthly temperature and total monthly precipitation compiled from different sources in northern Patagonia were interpolated to 20-km resolution grids over the period 1997–2010. This northern Pata...Climate data of mean monthly temperature and total monthly precipitation compiled from different sources in northern Patagonia were interpolated to 20-km resolution grids over the period 1997–2010. This northern Patagonian climate grid(NPCG) improves upon previous gridded products in terms of its spatial resolution and number of contributing stations, since it incorporates 218 and 114 precipitation and temperature records, respectively. A geostatistical method using surface elevation from a Digital Elevation Model(DEM) as the ancillary variable was used to interpolate station data into even spaced points. The maps provided by NPCG are consistent with the broad spatial and temporal patterns of the northern Patagonian climate, showing a comprehensive representation of the latitudinal and altitudinal gradients in temperature and precipitation, as well as their related patterns of seasonality and continentality. We compared the performance of NPCG and various other datasets available to the climate community for northern Patagonia.The grids used for the comparison included those of the Global Precipitation Climatology Project, ERAInterim, Climate Research Unit(University of East Anglia), and University of Delaware. Based on three statistics that quantitatively assess the spatial coherence of gridded data against available observations(bias,MAE, and RMSE), NPCG outperforms other global grids. NPCG represents a useful tool for understanding climate variability in northern Patagonia and a valuable input for regional models of hydrological and ecological processes. Its resolution is optimal for validating data from the general circulation models and working with raster data derived from remote sensing, such as vegetation indices.展开更多
Investigations into the Andean orocline revealed a counterclockwise rotation of about 37° in the north and a clockwise rotation of about 29° in the south. This rotation would have started in the Eocene becau...Investigations into the Andean orocline revealed a counterclockwise rotation of about 37° in the north and a clockwise rotation of about 29° in the south. This rotation would have started in the Eocene because the Nazca and South American plates converged. The transition zone between the Puna and the Sierras Pampeanas has a clockwise rotation pattern. Our new data show that the NE convergence of the Nazca and South American plates caused the counterclockwise rotation around the NW end of the Sierras Pampeanas. The temperature rise during a magmatic activity at 13 Ma would have favored a counterclockwise rotation of the mountain blocks of about 20° on a detachment zone within 10 to 15 km of depth. These range rotations generated local stress tensors trending NE and NW, facilitating the development of valleys, basins, mineralized dikes, mineral deposits, and alluvial fans separated from their origin. The Atajo fault shows both ductile and brittle characteristics. A mylonitic belt from the Sierra de Aconquija was juxtaposed on the rocks of the Ovejería Block and the Farallón Negro Volcanic Complex by reverse vertical displacement, and a dextral horizontal component of displacement resulted in curvatures that gave rise to pull-apart basins and step over features. The Santa Maria Valley, Campo del Arenal, Hualfín Valley, and Pipanaco salt flat most likely constituted a vast early Miocene basin rarely interrupted by low feature relief.展开更多
基金supported by grants from National Key R&D Program of China (2017YFC0601302)the NSF of China (41672214)Geological Survey Project of China Geological Survey (DD20189612, DD20190004).
文摘Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.
基金an Oak Ridge Associated Universities Junior Faculty Enhancement Awardan Appalachian State University Board of Trustees International Research Grant+1 种基金an Appalachian State University Research Council grant awarded to PI Martina Fulbright Foundation Science and Technology grant awarded to PI Wemple
文摘The páramo of the Northern Andes provide critically important ecosystem services to the Northern Andean region in the form of water provisioning and carbon sequestration, both of which are a result of the páramo?s organic-rich soils. Little is known, however, about the hydro-geomorphic characteristics of the rivers that drain these ecosystems. With impending plans for widespread hydro-development and increasing implementation of carbon-sequestering compensation for ecosystem services programs in the region it is imperative that we develop a thorough understanding of the hydrogeomorphic role that rivers play in this unique ecosystem. The objective of this study was to quantify bank erosion along an Amazonian headwater stream draining a small, relatively undisturbed páramo catchment to gain a better understanding of the natural erosion regime and the resulting sediment contributions from this unique ecosystem. This study implemented a combination of field, laboratory, and Geographic Information Systems techniques to quantify bank erosion rates and determine a bank erosion sediment yield from the Ningar River, a small páramo catchment(22.7 km^2) located in the eastern Andean cordillera of Ecuador. Results show that bank erosion rates range from 3.0 to ≥ 390.0 mm/yr, are highly episodic, and yield at least 487 tons of sediment annually to the Ningar River. These results imply that 1) páramo ecosystems substantially contribute to the sediment load of the Amazon River basin; 2) bank erosion is a potentially significant flux component of basin-scale carbon cycles in páramo ecosystems; and 3) hydrologic alteration campaigns(dam building) will likely critically alter these contributions and concomitantly disconnect a critical source of sediment and nutrients to downstream ecosystems.
基金funded by Fondecyt Projects(Nos. 1151146 and 1110914)Programa de Fomento y Transferencia tecnológica en Exploración Minera, código BIP № 30114940-0, PIP CONICET 2015-2017 No. 11220150100426,UBACYT 2015-2017 No. 20020150100166BA, PICT 2016 No. 2252, NSF EAR-165031the Yale Institute for Biospheric Studies
文摘The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic(U-Pb and^(40)Ar/^(39)Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas(～47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene-late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Marquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene-Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San Jose Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene-lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early-middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.
基金financed by CONICET(PIP 330)Universidad Nacional del Comahue (PIN 4-1-209)Minera Peregrine Argentina S.A.-Stillwater Mining Company
文摘We investigate the geology of Altar North(Cu-Au) and Quebrada de la Mina(Au) porphyry deposits located in San Juan Province(Argentina), close to the large Altar porphyry copper deposit(995 Mt,0.35% Cu, 0.083 g/t Au), to present constraints on the magmatic processes that occurred in the parental magma chambers of these magmatic-hydrothermal systems. Altar North deposit comprises a plagioclase-amphibole-phyric dacite intrusion(Altar North barren porphyry) and a plagioclaseamphibole-biotite-phyric dacite stock(Altar North mineralized porphyry, 11.98 ± 0.19 Ma). In Quebrada de la Mina, a plagioclase-amphibole-biotite-quartz-phyric dacite stock(QDM porphyry,11.91±0.33 Ma) crops out. High Sr/Y ratios(92-142) and amphibole compositions of Altar North barren and QDM porphyries reflect high magmatic oxidation states(fO_2= NNO+1.1 to+1.6) and high fH_2O conditions in their magmas. Zones and rims enriched in anorthite(An_(37-48))), SrO(0.22-0.33 wt.%)and FeO(0.21-0.37 wt.%) in plagioclase phenocrysts are evidences of magmatic recharge processes in the magma chambers. Altar North and Quebrada de la Mina intrusions have relatively homogeneous isotopic compositions(^(87)Sr/^(86)Sr_(t)= 0.70450-0.70466, ε_(ND)(t) = +0.2 to +1.2) consistent with mixed mantle and crust contributions in their magmas. Higher Pb isotopes ratios(^(207)Pb/^(204)Pb=15.6276-15.6294) of these intrusions compared to other porphyries of the district, reflect an increase in the assimilation of high radiogenic Pb components in the magmas. Ages of zircon xenocrysts(297,210,204,69 Ma) revealed that the magmas have experienced assimilation of Miocene, Cretaceous, Triassic and Carboniferous crustal rocks.Fluids that precipitated sulfides in the Altar deposit may have remobilized Pb from the host rocks, as indicated by the ore minerals being more radiogenic(207Pb/204 Pb = 15.6243-15.6269) than their host intrusions. Au/Cu ratio in Altar porphyries(average Au/Cu ratio of 0.14 ×10^(-4)by weight in Altar Central)is higher than in the giant Miocene porphyry deposits located to the south: Los Pelambres, Rio Blanco and Los Bronces(Chile) and Pachon(Argentina). We suggest that the increase in Au content in the porphyries of this region could be linked to the assimilation of high radiogenic Pb components in the magmas within these long-lived maturation systems.
文摘Páramo is a term used to describe tropical alpine vegetation between the continuous timberline and the snow line in the Northern Andes. Páramo environments provide important species habitat and ecosystem services. Changes in spatial extent of the páramo ecosystem at Pambamarca in the Central Cordillera of the northern Ecuadorian Andes were analysed using multi-temporal Landsat TM/ETM+ satellite data. The region suffered a loss of 1826.6 ha or 20% of the total area at a rate of 100 ha/annum during 1988-2007 period. It is found that permanent páramo cover decreased from 8350 ha in 1988 to 5864 ha in 2007 at a fairly constant rate(R2=0.94). This loss is attributed to expansion of commercial agriculture and floriculture in the valleys coupled with increased population pressure. Land at higher elevations has been cleared for small scale agriculture. Loss of the páramo ecosystem will exert a number of negative impacts on ecosystem services and livelihoods of the local population at Pambamarca.
基金the Ministry of Education, Youth and Sports of the Czech Republic within the framework of the National Sustainability Programme Ⅰ(NPU Ⅰ), Grant No. LO1415
文摘The most heavily glacierized tropical range in the world– the Peruvian Cordillera Blanca-has been losing ice since the end of the Little Ice Age(LIA).In this study,the decline of the Churup glacier(9°28’18"S;77°25’02"W)and associated processes were documented employing multi-proxy approach including the analysis of remotely sensed images(1948-2016),the Schmidt hammer rock test and lichenometric dating.It is shown that Churup glacier has lost the vast majority of its estimated LIA extent(1.05±0.1 km^2;45.0×10^6-57.4×10^6 m^3).The rate of glacier retreat is documented to vary in space(SE,SW and NW-facing slopes)and time,with the peak between 1986 and 1995.With an area of 0.045 km^2 in 2016,it is expected that the complete deglaciation of the Churup valley is inevitable in the near future.Recently(post-LIA)exposed bedrock surfaces have shown higher R-values(54.2-66.4,AVG 63.3,STDEV 2.9)compared to pre-LIA exposed surfaces(46.1-59.3,AVG 50.1,STDEV 4.9),confirming the links to the duration of rock weathering.The Lichenometric dating is applied to recently exposed areas and elevations above 4800 m a.s.l.,revealing only limited reliability and agreement with the age of deglaciation estimated from remotely-sensed images in such an environment.
文摘Many Andisols of the Andes have been disturbed by traditional potato-based rotation agriculture disrupting soil structure, water retention capacity and organic matter content. This study was undertaken to investigate the contribution of conservation farming technology or reduced tillage in potato-based rotations in the Colombian Andes in order to rehabilitate total and aggregated soil organic C in disturbed organic matter-rich Andisols. Soils were sampled from farms with 7-year of reduced tillage and farms with conventional farming practices. Ultrasound energy was applied to samples to disrupt aggregation and total soil C was determined in order to investigate the amount of carbon held inside the aggregates of different soil size classes. Results indicated that reduced tillage in potato-based crop rotations increased the soil C concentration and average C content in the whole profile (≈117 cm depth) by 50 and 33% (1636 t C ha?1 vs. 1224 t C ha?1), respectively, as compared to conventional farming practices. Carbon content increased 177% in the subsoil (A2 horizon, 78 -117 cm depth, from 215 to 596 t?ha?1), although most of the soil C was in the A1 horizon (between 0 -78 cm average thickness, 1097 t?ha?1). These increases show that reduced tillage enhances C stores in Andisols which are already high in organic matter. In addition, C in aggregates represented more than 80% of the total organic matter and it was positively affected by conservation practices. The C increase was preferential in the smaller macroaggregates (
基金supported by different grants received supported by different grants received from CONICET,UBACYT
文摘Several orogenic cycles of mountain building and subsequent collapse associated with periods of shallowing and steepening of subduction zones have been recognized in recent years in the Andes.Most of them are characterized by widespread crustal delamination expressed by large calderas and rhyolitic flare-up produced by the injection of hot asthenosphere in the subduction wedge.These processes are related to the increase of the subduction angle during trench roll-back.The Payenia paleoflat-slab,in the southern Central Andes of Argentina and Chile(34°—37°S) recorded a complete cycle from crustal thickening and mountain uplift to extensional collapse and normal faulting,which are related to changes in the subduction geometry.The early stages are associated with magmatic expansion and migration,subsequent deformation and broken foreland.New ages and geochemical data show the middle to late Miocene expansion and migration of arc volcanism towards the foreland region was associated with important deformation in the Andean foothills.However,the main difference of this orogenic cycle with the previously described cycles is that the steepening of the oceanic subducted slab is linked to basaltic flooding of large areas in the retroarc under an extensional setting.Crustal delamination is concentrated only in a narrow central belt along the cordilleran axis.The striking differences between the two types of cycles are interpreted to be related to the crustal thickness when steepening the subducting slab.The crustal thickness of the Altiplano is over 60-80 km,whereas Payenia is less than 42 km in the axial part,and near 30 km in the retroarc foothills.The final extensional regime associated with the slab steepening favors the basaltic flooding of more than 8400 km^3 in an area larger than 40,000 km2,through 800 central vents and large fissures.These characteristics are unique in the entire present-day Andes.
基金a grant from the International Development Research Centre, Canada, and Microsoft Corporationsupport of the Seminario Permanente de Investigacion Agraria (Permanent Seminar on Agricultural Research), SEPIA
文摘Communities in developing country mountain areas,in part due to their remoteness,find themselves excluded from social,political and economic systems; and excluded from access to resources. This paper aims to study the impact of information and communication technologies (ICTs) on remoteness and exclusion. It utilises two models - the resource movement framework,and the "information chain" - to analyse a telecentre in one district of mountainous Huancavelica,Peru's poorest region,set in the high Andes. It finds ICTs enabling new and positive resource flows for the two key user groups:teenaged school students and young farmers. These help to maintain social networks. They also support information searches that have improved agricultural practice where other information chain resources have been available. But non-use and ineffective use of the telecentre are found where information chain resources are lacking. ICTs have some impacts on intangible elements of remoteness. In this particular example,they also offer access to some previously-excluded resources. But they have not really addressed the systematic exclusions faced by mountain communities. And they so far appear to be a technology of inequality; favouring those residents who begin with better resource endowments.The paper concludes by offering some recommendations for mountain ICT project practice.
文摘This paper presents preliminary results of three-dimensional thermo mechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes(16°S-26°S) up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker-Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area.In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters(e.g. viscosity, fault friction, velocity, shear heating) on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing computational time.
文摘This paper discusses participatory research in the Andes and presents a case study in Cotacachi, Ecuador, where sustainability scientists and indigenous people seek common ground in their respective but drastically different research and social agendas. Participatory research based on Andean experiences pre-dated and inspired much of the later international movement in agriculture, health, and conservation. Andean communities have a long history in demanding that outsiders address the needs of the community as a condition for carrying out scientific or applied activities. What an Andean community, however, sees as relevant may or may not be within the rubric of ‘participatory research’ as it is practiced throughout much of the world. In fact, overzealous participatory researchers are just as bothersome as their predecessors bearing long questionnaires. More important to Andean people is an equitable relationship with researchers and developers in which exchanges of value are made. A distinction between ‘enriching’ and ‘extractive’ research is drawn. In the case of the SANREM project in Cotacachi, Ecuador, scientists carried out enriching research activities of interest to local people as a wayto generate social capital for conducting basic research which does not have an obvious, immediate local benefit. The requested research did not have a conventional participatory methodology but provided valuable products (educational opportunity, germplasm, community visualization tools, and information) to the indigenous community in exchange for time and resources to conduct research on more basic natural resource questions. We argue that in the Andean context the key to reconciling the needs of scientists and of local needs is seeking new forms of equitable collaboration which reach beyond the present and now somewhat tired discourse of ‘participation’.
基金FAPEMIG (PPM X 45-16)CNPqpartially funded by CNPq 308035/2013-5
文摘Projections of climate change are essential to guide sustainable development plans in the tropical Andean countries such as Peru. This study assessed the projections of precipitation and potential evaporation, rain erosive potential, and precipitation concentration in the Mantaro River Basin, in the Peruvian Andes, which is important for agriculture and energy production in Peru. We assumed the Intergovernmental Panel on Climate Change(IPCC)A_1B greenhouse gas emission scenario and simulated the global climate change by the HadCM_3 global climate model. Due to the steepness of the mountain slopes and the narrowness of the river valley, this study uses the downscaling of the global model simulations by the regional Eta model down to 20-km resolution. The downscaling projections show decrease in the monthly precipitation with respect to the baseline period, especially during the rainy season,between February and April, until the end of the 21st century. Meanwhile, a progressive increase in the monthly evaporation from the baseline period is projected. The Modified Fournier Index(MFI) shows a statistically significant downward trend in the Mantaro River Basin, which suggests a possible reduction in the rain erosive potential. The Precipitation Concentration Index(PCI) shows a statistically significant increasing trend, which indicates increasingly more irregular temporal distribution of precipitation towards the end of the century. The results of this study allow us to conclude that there should be a gradual increase in water deficit and precipitation concentration. Both changes can be negative for agriculture, power generation, and water supply in the Mantaro River Basin in Peru.
文摘A molecular phylogenetic analysis of most of the species of Perezia reveals that,as traditionally defined,the genus is not monophyletic with two species more closely related to Nassauvia than to Perezia.In addition,our results show that Burkartia(Perezia) lanigera is related to Acourtia and is the only member of that clade in South America.The remaining species are monophyletic and show a pattern of an early split between a western temperate and an eastern subtropical clade of species.Within the western clade,the phylogeny indicates a pattern of diversification that proceeded from southern,comparatively low-elevation habitats to southern high-elevation habitats,and ultimately into more northern high-elevation habitats.The most derived clades are found in the high central Andes,where significant radiation has occurred.
文摘In the summer of 2010/2011 Chile suffered the third most severe energy and water supply crisis in only one decade.This may be surprising as the Andes which accompany the country along 4,200 km are a water tower and could provide more electricity and water than needed.On top of that,it has to be mentioned that Chile also counts with sunny and windy climates and with excellent geothermal energy resources and thus has a huge potential as far as renewable energies are concerned.After analyzing the existing natural conditions,the infrastructure and the present challenges of climate change,it has to be asked in which way Chile can make use of this potential in the near future,considering the legal and political situation and the technological opportunities.It seems that the resources are still hidden in the Andes,and only the key is missing to realize the country's natural potential.This research has been based on the analysis of existing literature,media,quantitative data from government institutions and other antecedents obtained by the authors in field work done in the South of Chile in 2010.The added value of this compilation lies in the comprehensive perspective,linking the knowledge of climatologists,hydrologists,mountain researchers and energy experts in order to support a sustainable energy and water supply for the future in Chile.From this present research,it can be concluded that Chile necessarilyhas to adopt new energy-related strategies,particularly those aimed at diminishing the strong dependence on traditional sources of energy and establishing new techniques and technologies for generating electricity and utilizing the vast potential that the country is ready to offer,such as that provided by the Andes along 4,200 kilometers.
基金funded by the Austrian Science Fund (FWF) [Project No. P24692]
文摘Due to their ecological disadvantages,many mountain regions have experienced land-use abandonment and shrub encroachment on former grassland at higher altitudinal zones—especially during recent decades of urbanization. But does this trend also apply to the hinterland of urban settlements? By using the Southern Colombian example of Popayán, a medium-sized city located in the Northern Andes, we can show that the landscape changes observed between 1989 and 2010 can hardly be related to agricultural abandonment. Hypsometric variations of land-cover change indicate that, until 2001, woods or shrubland expanded faster at the lower altitudinal range adjacent to the city than at the more remote higher zones. In contrast, after 2001 grassland areas increased on former woods or shrubland at all altitudinal belts. Both periods thus present developments that can be interpreted as the result of land-use expansion below 2000 m asl and land-use persistence in the tierra fría of the mountain city's hinterland.
文摘The nuclear ribosomal ITS region and the chloroplast trnL-trnF (trnLF) intergenic region were se-quenced for 45 accessions of Paranephelius and six accessions of Pseudonoseris, the two genera of the subtribe Paranepheliinae (Liabeae, Asteraceae) distributed in the alpine regions of the Andes. This data set was used to estimate relationships between these genera and within each genus to aid in evaluating morphological variation and classification. Our results with both ITS and trnLF markers support the monophyly of subtribe Paranephelii-nae, and place Pseudonoseris discolor as the first diverged taxon sister to the clade containing Paranephelius. Pseudonoseris szyszylowiczii exhibited intraspecific divergence supporting intergeneric hybridization between Pseudonoseris and Paranephelius. Within Paranephelius, genetic divergence is low and not adequate to fully resolve phylogenetic relationships at the species level, but two genetically and morphologically recognizable groups were revealed by the ITS data. Several accessions possessing multiple ITS sequences represent putative hybrids between the two groups. These putative hybrids have caused some taxonomic confusion and difficulties in establishing species boundaries in Paranephelius. The divergence time estimates based on ITS sequences indi-cated that the stem of subtribe Paranepheliinae dates to 13 million years ago, but the diversification of the crown clade of the extant members began in the early Pleistocene or late Pliocene, perhaps associated with the uplift of the Andes and the climatic changes of global cooling.
基金Supported by the Instituto Nacional de Tecnología Agropecuaria,Consejo Nacional de Investigaciones Científicas y TcnicasAustralian Research Council(ARC DP120104320)+1 种基金Inter-American Institute for Global Change Research(IAICRN02-47)
文摘Climate data of mean monthly temperature and total monthly precipitation compiled from different sources in northern Patagonia were interpolated to 20-km resolution grids over the period 1997–2010. This northern Patagonian climate grid(NPCG) improves upon previous gridded products in terms of its spatial resolution and number of contributing stations, since it incorporates 218 and 114 precipitation and temperature records, respectively. A geostatistical method using surface elevation from a Digital Elevation Model(DEM) as the ancillary variable was used to interpolate station data into even spaced points. The maps provided by NPCG are consistent with the broad spatial and temporal patterns of the northern Patagonian climate, showing a comprehensive representation of the latitudinal and altitudinal gradients in temperature and precipitation, as well as their related patterns of seasonality and continentality. We compared the performance of NPCG and various other datasets available to the climate community for northern Patagonia.The grids used for the comparison included those of the Global Precipitation Climatology Project, ERAInterim, Climate Research Unit(University of East Anglia), and University of Delaware. Based on three statistics that quantitatively assess the spatial coherence of gridded data against available observations(bias,MAE, and RMSE), NPCG outperforms other global grids. NPCG represents a useful tool for understanding climate variability in northern Patagonia and a valuable input for regional models of hydrological and ecological processes. Its resolution is optimal for validating data from the general circulation models and working with raster data derived from remote sensing, such as vegetation indices.
文摘Investigations into the Andean orocline revealed a counterclockwise rotation of about 37° in the north and a clockwise rotation of about 29° in the south. This rotation would have started in the Eocene because the Nazca and South American plates converged. The transition zone between the Puna and the Sierras Pampeanas has a clockwise rotation pattern. Our new data show that the NE convergence of the Nazca and South American plates caused the counterclockwise rotation around the NW end of the Sierras Pampeanas. The temperature rise during a magmatic activity at 13 Ma would have favored a counterclockwise rotation of the mountain blocks of about 20° on a detachment zone within 10 to 15 km of depth. These range rotations generated local stress tensors trending NE and NW, facilitating the development of valleys, basins, mineralized dikes, mineral deposits, and alluvial fans separated from their origin. The Atajo fault shows both ductile and brittle characteristics. A mylonitic belt from the Sierra de Aconquija was juxtaposed on the rocks of the Ovejería Block and the Farallón Negro Volcanic Complex by reverse vertical displacement, and a dextral horizontal component of displacement resulted in curvatures that gave rise to pull-apart basins and step over features. The Santa Maria Valley, Campo del Arenal, Hualfín Valley, and Pipanaco salt flat most likely constituted a vast early Miocene basin rarely interrupted by low feature relief.
