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Sample records for betic cordillera southern

  1. The recycled orogenic sand provenance from an uplifted thrust belt, Betic Cordillera, Southern Spain

    OpenAIRE

    Critelli, Salvatore; Arribas Mocoroa, José; Le Pera, Emilia; Tortosa, A; Marsaglia, Kathleen M.; Latter, Kelly K.

    2003-01-01

    The Betic Cordillera of southern Spain represents an uplifted foreland fold–thrust belt. Source rock types of the Betic Cordillera include metamorphic (mainly phyllite, schist, quartzite, and gneiss), sedimentary (siliciclastic and carbonate), volcanic (felsic to intermediate pyroclasts), and mantle-derived (peridotite, gabbro, serpentinite, and serpentine schist) rocks. The fluvial systems range that transect the Betic Cordillera are the major detrital source of sediment ...

  2. Basement structure of the Granada basin, Betic Cordilleras, southern Spain

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    Morales, J.; Vidal, F.; De Miguel, F.; Alguacil, G.; Posadas, A. M.; Ibañez, J. M.; Guzmán, A.; Guirao, J. M.

    1990-06-01

    The analysis and interpretation of geophysical data (gravity and seismic reflection) has facilitated the definition of the Granada basin structure. The reflector showing the contact between the Betic-Subbetic basement and the Neogene-Quaternary sedimentary filling has been identified. Mapping of the basement in two and three dimensions is presented. The presence of four important depocenters (Genil, Chimeneas, Cubillas and Granada) has been determined. These troughs are limited by ridge areas through important sets of fractures. In some cases the accumulation of Neogene-Quaternary sediments reaches a thickness exceeding 3 km as in the Genii and Cubillas depocenters. The mapping of the most important fractures affecting the basement has been achieved, defining four systems that have influenced and conditioned the genesis and late evolution of the Granada basin. The directions of the most important groups of fractures are: NE-SW, N70W to E-W, N45W and N10-30E.

  3. Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

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    Bellin, N.; Vanacker, V.; Kubik, P.

    2012-04-01

    In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

  4. Multi-temporal InSAR for Deformation Monitoring of the Granada and Padul Faults and the Surrounding Area (Betic Cordillera, Southern Spain)

    NARCIS (Netherlands)

    Sousa, J.J.; Ruiz, A.M.; Hooper, A.J.; Hanssen, R.F.; Perski, Z.; Bastos, L.C.; Gil, A.J.; Galindo-Zaldivar, J.; Sanz de Galdeano, C.; Alfaro, P.; Garrido, M.S.; Armenteros, J.A.; Gimenez, E.; Aviles, M.

    2014-01-01

    The quantification of low rate active tectonic structures is a major target of geodetic and geological studies to improve the knowledge of seismic hazards. The central Betic Cordillera (southern Spain) is affected by moderately active tectonic structures and seismicity. Part of this seismic activity

  5. Multi-temporal InSAR for Deformation Monitoring of the Granada and Padul Faults and the Surrounding Area (Betic Cordillera, Southern Spain)

    NARCIS (Netherlands)

    Sousa, J.J.; Ruiz, A.M.; Hooper, A.J.; Hanssen, R.F.; Perski, Z.; Bastos, L.C.; Gil, A.J.; Galindo-Zaldivar, J.; Sanz de Galdeano, C.; Alfaro, P.; Garrido, M.S.; Armenteros, J.A.; Gimenez, E.; Aviles, M.

    2014-01-01

    The quantification of low rate active tectonic structures is a major target of geodetic and geological studies to improve the knowledge of seismic hazards. The central Betic Cordillera (southern Spain) is affected by moderately active tectonic structures and seismicity. Part of this seismic activity

  6. East-west thrusting and anomalous magnetic declinations in the Sierra Gorda, Betic Cordillera, southern Spain

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    Platzman, E. S.

    1994-01-01

    Structural and palaeomagnetic studies in the Sierra Gorda (Sierra de Loja), located in the External zone of the Betic Cordillera, indicate that westward-directed thrusting is not associated with significant rotations about a vertical axis. Detailed mapping and slip vector analysis show that the Sierra Gorda is a thrust complex composed of three thrust sheets. The uppermost thrust places Early Jurassic pelagic carbonates on top of Jurassic to Oligocene sediments that form a large doubly-plunging footwall syncline. The eastern limb of this syncline has been overturned and is tectonically thinned as a result of the overthrusting. Palaeomagnetic results from Mesozoic and Tertiary sediments both within and around the perimeter of the Sierra Gorda indicate that: (1) the average remanence vector of the seven Late Jurassic localities sampled within the Sierra Gorda has a direction (D = 328° and I = 38°) that is not significantly different from the expected declination for the Upper Jurassic of stable Iberia; and (2) there is no significant difference between the remanences in the two upper thrust sheets indicating that differential rotation did not occur during the initiation and displacement on the thrusts. In contrast, the one Late Jurassic site that was sampled to the west of the Sierra Gorda is rotated, like the rest of the Subbetics, 60° clockwise of the reference direction. The unrotated directions obtained in the Sierra suggest, either that it has rotated in a clockwise sense concordant with the rest of the Subbetic zone and has then been backrotated, or that it has never rotated relative to stable Iberia. In the latter, simpler hypothesis the unrotated declinations may be explained in terms of orthogonal convergence along an irregular continental margin.

  7. Paleomagnetism of the Velez Rubio Dykes: Implications for transport directions in a collapsing orogen (Betic Cordillera, southern Spain)

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    Platzman, E. S.; Platt, J. P.

    2003-04-01

    Palaeomagnetic and structural analysis of a suite of altered Neogene mafic dykes intruded into the Alpujarride allochthon in the Internal Zone of the Betic Cordillera demonstrate that between 32-62° clockwise vertical-axis rotation occurred after the major extensional event on the adjacent Malaguide Alpujarride. Anisotropy of magnetic susceptibility (AMS) measurements show that the dykes are virtually free of a penetrative magnetic fabric associated with this deformational event. Results of demagnetization experiments show that the remanence in many of the dykes is composed of one to three components. The lowest temperature component is usually in the direction of the present earth's magnetic field and is interpreted as a viscous overprint. The intermediate temperature component is carried by pyrrhotite and frequently has a direction identical to the high temperature remanence fraction. The high temperature component, which demagnetizes at the curie point of magnetite (575 °C), has an average declination of 242° and an inclination of -19°. Lack of a well-defined magnetic fabric coupled with a shallow inclination suggests that these dykes have rotated about a horizontal as well as a vertical axis. Rotation of approximately 57° about a horizontal NNE-trending axis, normal to the dykes, brings the inclination into statistical agreement with the expected inclination for the Oligocene. This rotation leaves the dykes in a near-vertical orientation, decreases the declination anomaly to 32° and brings the foliation in the surrounding schists approximately horizontal. We suggest that the regional foliation may have been sub-horizontal at the time of dyke emplacement, probably as a result of the phase of late-orogenic extension. The regional stretching lineation and hence transport direction associated with the extensional event was originally oriented NNE. sub-parallel to the finite extension directions obtained further to the west implying a large component of radial

  8. The Messinian early Pliocene stratigraphic record in the southern Bajo Segura Basin (Betic Cordillera, Spain): Implications for the Mediterranean salinity crisis

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    Soria, Jesús M.; Caracuel, Jesús E.; Corbí, Hugo; Dinarès-Turell, Jaume; Lancis, Carlos; Tent-Manclús, José E.; Viseras, César; Yébenes, Alfonso

    2008-01-01

    The analysis of the Messinian and Pliocene stratigraphy of the southern Bajo Segura Basin (Betic Cordillera, Spain) has revealed three highstand sedimentary phases (Messinian I, Messinian II, and Pliocene) bounded by two lowstand erosional surfaces (intra-Messinian and end-Messinian unconformities). The Messinian I highstand phase is characterized by the progradation of coastal and shallow marine sandstones (La Virgen Fm) over slope and pelagic-basin marls (Torremendo Fm). After this first phase, a fall in sea level brought about the intra-Messinian unconformity, a subaerial erosional surface with local accumulations of karstic breccias and caliche-like carbonate crusts. The Messinian II highstand phase is represented by sandy beaches and muddy lagoons (Garruchal Fm) correlative with shallow marine evaporites (San Miguel Fm); this second phase records the intra-Messinian reflooding of the basin, which characterizes the salinity crisis in the marginal basins of the Mediterranean. A new sea-level fall resulted in the end-Messinian unconformity, of which the most significant feature is the presence of a broad palaeovalley, c. 200 m deep, which, along its course, completely eroded the deposits of the Messinian II phase and part of the deposits of the Messinian I phase. The Pliocene highstand phase begins with coastal and shallow marine conglomerates and sandstones (La Pedrera Fm) which fill the deep part of the above-mentioned palaeovalley. These bottom deposits evolved gradually upwards towards pelagic marls (Hurchillo Fm), over which shallow marine and coastal sandstones prograded (Rojales Fm). This third phase records the flooding of the basin at the beginning of the Pliocene, when the salinity crisis ended in the marginal basins of the Mediterranean. The combination of calcareous nannoplankton biostratigraphy and magnetostratigraphy has confirmed that both the end of the sedimentation of the Messinian I phase, as well as the two lowstand erosional surfaces (intra

  9. Latest extension of the Laujar fault in a convergence setting (Sierra Nevada, Betic Cordillera)

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    Martínez-Martos, Manuel; Galindo-Zaldívar, Jesus; Sanz de Galdeano, Carlos; García-Tortosa, Francisco Juan; Martínez-Moreno, Francisco José; Ruano, Patricia; González-Castillo, Lourdes; Azañón, José Miguel

    2017-02-01

    The present-day relief of the Betic Cordillera formed since the Late Miocene through the regional N-S to NW-SE Africa-Eurasia convergence that developed large folds. The Laujar Fault Zone is a south-dipping E-W oriented structure located at the northern boundary of the Alpujarran Corridor Neogene intramontane basin, which separates Sierra Nevada and Sierra de Gador antiforms, in the Internal Zones of the Betic Cordillera. The fault zone acted in a first stage as a dextral strike-slip fault. Currently it moves as a normal fault evidenced by striated calcretes, also in agreement with regional continuous GPS (CGPS) data that support the hypothesis of an active N-S extension in the fault area. In order to analyse the deep geometry of the Laujar Fault Zone, we combined several geophysical techniques (gravity, magnetic, electric resistivity tomography and audio-magnetotelluric data) with field geological observations. Fault surfaces seem to join at a southward-dipping shallow detachment level, including faults covered by the sedimentary infill. The fault zone was developed in a previously weakened area by wrench faults parallel to the Alpujarran Corridor. The recent normal activity of this fault zone may be a consequence of a change in the Africa-Eurasia convergence orientation, which implies a decrease in the N-S compression component. This structure along the southern limb of Sierra Nevada antiform evidences the gravitational collapse of previously thickened crust in a regional compressional context simultaneous to metamorphic core uplift.

  10. Active rollback in the Gibraltar Arc: Evidences from CGPS data in the western Betic Cordillera

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    Gonzalez-Castillo, L.; Galindo-Zaldivar, J.; de Lacy, M. C.; Borque, M. J.; Martinez-Moreno, F. J.; García-Armenteros, J. A.; Gil, A. J.

    2015-11-01

    The Gibraltar Arc, located in the western Mediterranean Sea, is an arcuate Alpine orogen formed by the Betic and Rif Cordilleras, separated by the Alboran Sea. New continuous GPS data (2008-2013) obtained in the Topo-Iberia stations of the western Betic Cordillera allow us to improve the present-day deformation pattern related to active tectonics in this collision area between the Eurasian and African plates. These data indicate a very consistent westward motion of the Betic Cordillera with respect to the relatively stable Iberian Massif foreland. The displacement in the Betics increases toward the south and west, reaching maximum values in the Gibraltar Strait area (4.27 mm/yr in Ceuta, CEU1, and 4.06 mm/yr in San Fernando, SFER), then progressively decreasing toward the northwestern mountain front. The recent geological structures and seismicity evidence moderate deformation in a roughly NW-SE to WNW-ESE compressional stress setting in the mountain frontal areas, and moderate extension toward the internal part of the cordillera. The mountain front undergoes progressive development of folds affecting at least up to Pliocene deposits, with similar recent geological and geodetical rates. This folded strip helps to accommodate the active deformation with scarce associated seismicity. The displacement pattern is in agreement with the present-day clockwise rotation of the tectonic units in the northern branch of the Gibraltar Arc. Our data support that the westward emplacement of the Betic Cordillera continues to be active in a rollback tectonic scenario.

  11. Large Holocene morphogenic earthquakes along the Albox fault, Betic Cordillera, Spain

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    Masana, E.; Pallàs, R.; Perea, H.; Ortuño, M.; Martínez-Díaz, J. J.; García-Meléndez, E.; Santanach, P.

    2005-09-01

    The Eastern Betic Shear Zone (EBSZ) in the Betic Cordillera (southern Spain) accommodates part of the Neogene and Quaternary shortening between the Iberian and the African plates. Although the EBSZ is characterised by shallow low to moderate magnitude instrumental seismicity, it seems to be the source of several historical catastrophic events with MSK intensities ranging from VII to X. Despite the fact that it crosses a densely populated area, the seismogenic behaviour of the EBSZ is still poorly understood. The EBSZ is mainly formed by a set of NE-SW-trending left-lateral strike-slip faults, including the Alhama de Murcia and Albox faults. This paper presents a palaeoseismological study of the eastern Albox fault based on surface and trenching observations. This fault ruptures the surface and is probably seismogenic, with short-term slip-rates ranging from 0.01 to 0.4 mm/a. Ground effects of at least two paleoearthquakes were detected: the first one took place not long before 660 years A.D. with an estimated maximum Mw of 6.5 ± 0.1, whereas the second one occurred between 650 A. D. and the XVIII century. The latter produced only a centimetric offset and was not regarded as characteristic. The elapsed time is, therefore, ca. 660 years. The distribution of the long-term cumulative and the short-term ground effects suggest an eastwards migration of the fault tip.

  12. Active shallow extension in central and eastern Betic Cordillera from CGPS data

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    Galindo-Zaldivar, J.; Gil, A. J.; Sanz de Galdeano, C.; Lacy, M. C.; García-Armenteros, J. A.; Ruano, P.; Ruiz, A. M.; Martínez-Martos, M.; Alfaro, P.

    2015-11-01

    The Betic Cordillera is an Alpine belt formed in the western Mediterranean by the westward displacement of the Alboran Domain in between the Eurasian and African convergent plates. New CGPS data from the central and eastern Betic Cordillera and its foreland-obtained mainly from the Topo-Iberia project-allowed us to precisely determine the rate of tectonic deformation. Most of the displacements of the central and eastern Betics are westward, with a variable southwestward component, in relation to the Eurasian stable plate. While in the Iberian foreland the displacements are extremely low, some deformation related to low compressional deformation occurs in the easternmost foreland basin and eastern Betic Cordillera. The displacement increases substantially southwards and westwards in relation to present-day extensional deformation. Major active discontinuities correspond to the NW-SE normal fault zones, which dip westwards; they are located in Almeria-Tabernas; Balanegra, and western Sierra de Gador; whereas the Padul fault zone located west of Sierra Nevada extends northwards to the Granada Basin. NW-SE extensional faults are also observed to the north, in the Baza Basin. Moreover, the activity of dextral faults along the Sorbas-Tabernas-Alpujarras-Guajares band, generally considered as a transfer fault zone, is evidenced by the displacement data. These results come to demonstrate the low activity or inactivity of the large northern E-W oriented folds of the central and eastern Internal Zone, such as the Sierra de Los Filabres antiform. They also point to the possible residual activity of the northern part of the NE-SW Sierra Nevada antiform, where the maximum relief of the Cordillera is found. Altogether, our data support a heterogeneous present-day westward extension that affects the upper crust of the Betic Cordillera and increases towards the thinned continental crust of the Alboran Sea and towards the west, which is compatible with roll-back subduction along

  13. JURASSIC PALEONTOLOGICAL HERITAGE OF MURCIA (BETIC CORDILLERA, SOUTH-EASTERN SPAIN

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    GREGORIO ROMERO

    2004-03-01

    Full Text Available Jurassic rocks of the External and Internal Zones of the Betic Cordillera are widespread in the province of Murcia. Four areas are considered of special interest for stratigraphical and paleontological analysis: a Sierra Quípar and b Sierras Lúgar-Corque (External Subbetic, c Sierra Ricote (Median Subbetic and d Sierra Espuña (Malaguide Complex. The first two contain Jurassic sections including Sinemurian-Tithonian deposits, and major stratigraphic discontinuities, containing significant cephalopod concentrations of taphonomic and taxonomic interest, occuring in the Lower-Upper Pliensbachian, Lower/Middle Jurassic and Middle/Upper Jurassic boundaries. These areas are also relevant for biostratigraphical analysis of the Middle-Upper Jurassic interval. In the Sierra de Ricote, the Mahoma section is of especial interest for the study of Lías/Dogger transition. Casa Chimeneas section constitutes the best Subbetic site for the analysis of the Lower/Upper Bajocian boundary. In the La Bermeja-Casas de Vite area, the Bajocian-Tithonian interval is well-represented, including a parastratotype of the Radiolarite Jarropa Formation. Finally, the Malvariche section in Sierra Espuña represents the best Jurassic succession of Internal Zones of the Betic Cordillera and could be considered as a reference section for this Betic Domain. In this paper a heritage evaluation has been carried out for these classical jurassic sections with the object of protecting these sites according to the legal framework prevailing in the province of Murcia.

  14. CO2-rich thermomineral groundwater in the Betic Cordilleras, southeastern Spain: Genesis and tectonic implications

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    Cerón, J. C.; Martín-Vallejo, M.; García-Rossell, L.

    The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological setting, physical and chemical characteristics, and 13C-isotope content. The study area is about 60km northeast of Almería city, in southeastern Spain. The thermomineral waters are plentiful and are related to regional geothermal anomalies. Temperatures of 20 -41°C, high bicarbonate concentrations (183-1824mg/L), and high amounts of PCO2 (aguas termales con elevados contenidos en CO2 de las Cordilleras Béticas han sido estudiadas en relación con los aspectos geológicos e hidrogeológicos, sus características físicas y químicas, y sus contenidos en 13C. El área de estudio se encuentra aproximadamente a 60km al noreste de la ciudad de Almería, en el sureste de España. Las aguas termominerales son numerosas y están relacionadas con anomalías geotermales regionales. El agua subterránea tiene una temperatura comprendida entre 20-41°C, alta concentración de bicarbonatos (entre 183-1824mg/L) y elevada PCO2 (agua subterránea origina problemas en los sondeos y en el uso del agua. El carácter hidrotermal de este área estaría relacionado con su actividad neotectónica.

  15. Faulted hybrid joints: an example from the Campo de Dalias (Betic Cordilleras, Spain)

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    Marín-Lechado, Carlos; Galindo-Zaldívar, Jesús; Rodríguez-Fernández, Luís. Roberto; González-Lodeiro, Francisco

    2004-11-01

    The development of hybrid and faulted joints has not been studied in detail in natural outcrops. This field study in the Campo de Dalias (Betic Cordilleras) establishes the distinctive features of these structures as compared with those predicted by theoretical studies. Hybrid joints appear as two sets of vertical joints forming variable angles, but generally about 25°, with opening directions orthogonal to joint planes. Their development requires low differential stresses with a tensile minimum stress. The main criteria that indicate the existence of faulted joints are: (1) the presence of subvertical fault planes with oblique slip forming a complex pattern of dextral and sinistral faults developed under a single stress regime; (2) faults with similar geometries as joints in the same outcrop, showing an inconsistent cross-cutting relationship; and (3) the development of small basins with variable polarity of asymmetric wedge filling. A permutation in stress orientation since the Tortonian in the Campo de Dalias was responsible for the development of a faulted hybrid joint system, with a constant ENE-WSW extension trend and a switch of σ1 between NNW-SSE and vertical.

  16. Structure of Sierra Blanca (Alpujarride Complex, west of the Betic Cordillera

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    Andreo, B.

    1995-04-01

    Full Text Available Sierra Blanca, situated in the SW of Málaga, forms part of the Blanca unit, belonging to the Alpujarride Complex of the Betic Cordillera. Its lithologic sequences are made up of a group of migmatites, gneisses and schists and an upper formation of marbles (white dolomitic and the bottom and blue calcareous towards the top, linked with a transitional contact. The structure of Sierra Blanca is comprised of folds, generally isoclinal, with reversed limbs and with important tectonic transpositions, the direction of which is approximately E-W in the eastern area and N-S and E-W in the West. In both areas the folds present opposing vergences, consistently towards the interior of the sierra. The origin of these structures is explained with a model of westerly movements of the Blanca unit, in relation to the Los Reales unit, with the formation of frontal and lateral folds. In its advancement, the western part of Sierra Blanca underwent an important anti-clockwise rotation responsible for the co-existence of folds in N-S and E-W directions. These structures occurred under ductile conditions, owing to the presence of important overthrusting peridotitic masses of the Los Reales unit. This model of westerly displacement is inserted in the process undergone by the Betic-Rif Internal Zones (with Blanca and Los Reales units included which occurred at the end of the Oligocene-Early Miocene when the Gibraltar arch began to be formed.Sierra Blanca, situada al SW de Málaga, forma parte de la unidad de Blanca que pertenece al complejo Alpujárride de la Cordillera Bética. Su secuencia litológica está compuesta por un conjunto inferior de migmatitas, gneises y esquistos, y por una formación superior de mármoles, blancos dolomíticos en la base y mármoles calizos azules hacia la parte superior, entre los que existe un tránsito gradual. La estructura de Sierra Blanca está formada por pliegues, generalmente isoclinales, con flancos invertidos que muestran

  17. The Padul normal fault activity constrained by GPS data: Brittle extension orthogonal to folding in the central Betic Cordillera

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    Gil, Antonio J.; Galindo-Zaldívar, Jesús; Sanz de Galdeano, Carlos; Borque, Maria Jesús; Sánchez-Alzola, Alberto; Martinez-Martos, Manuel; Alfaro, Pedro

    2017-08-01

    The Padul Fault is located in the Central Betic Cordillera, formed in the framework of the NW-SE Eurasian-African plate convergence. In the Internal Zone, large E-W to NE-SW folds of western Sierra Nevada accommodated the greatest NW-SE shortening and uplift of the cordillera. However, GPS networks reveal a present-day dominant E-W to NE-SW extensional setting at surface. The Padul Fault is the most relevant and best exposed active normal fault that accommodates most of the NE-SW extension of the Central Betics. This WSW-wards dipping fault, formed by several segments of up to 7 km maximum length, favored the uplift of the Sierra Nevada footwall away from the Padul graben hanging wall. A non-permanent GPS network installed in 1999 constrains an average horizontal extensional rate of 0.5 mm/yr in N66°E direction. The fault length suggests that a (maximum) 6 magnitude earthquake may be expected, but the absence of instrumental or historical seismic events would indicate that fault activity occurs at least partially by creep. Striae on fault surfaces evidence normal-sinistral kinematics, suggesting that the Padul Fault may have been a main transfer fault of the westernmost end of the Sierra Nevada antiform. Nevertheless, GPS results evidence: (1) shortening in the Sierra Nevada antiform is in its latest stages, and (2) the present-day fault shows normal with minor oblique dextral displacements. The recent change in Padul fault kinematics will be related to the present-day dominance of the ENE-WSW regional extension versus NNW-SSE shortening that produced the uplift and northwestwards displacement of Sierra Nevada antiform. This region illustrates the importance of heterogeneous brittle extensional tectonics in the latest uplift stages of compressional orogens, as well as the interaction of folding during the development of faults at shallow crustal levels.

  18. Approach to the Lower Pliocene marine-continental correlation from southern Spain. The micrommamal site of Alhaurín el Grande-1 (Málaga Basin, Betic Cordillera, Spain

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    Guerra-Merchán, A.

    2013-06-01

    Full Text Available A new micromammal site at Alhaurín el Grande (Málaga, southern Spain located above early Pliocene marine deposits allows an approach to the marine-continental correlation for this age. The early Pliocene marine filling throughout the Málaga Basin is developed in three transgressive-regressive sequences (Pl-1, Pl-2, and Pl-3 units bounded by discontinuities. At the top of the intermediate sequence Pl-2, peaty sediments have yielded fossils of Rodentia, Lagomorpha, Insectivora, and Crocodylia. The presence of Cricetus barrieri Mein & Michaux, 1970 in combination with murids, both of primitive morphology, such as Apodemus gudrunae Van de Weerd, 1976, something clearer (i.e. Occitanomys brailloni Michaux, 1969 and Stephanomys donnezani cordii Ruiz Bustos, 1986, points to an early Ruscinian age(MN14 biozone. Based on the planktonic foraminifers, the biostratigraphic data indicate that marine sediments just below the micromammal beds belong to the the MPl-2 biozone of the early Zanclean. Available paleomagnetic data from the marine sediments show that the micromammal bed must be located between the normal geomagnetic subchron C3n3n (4.89-4.80 Ma and the subchron C3n2n (4.63-4.49 Ma, limiting the age of this site to the late part of the early Zanclean.Un nuevo yacimiento de micromamíferos en Alhaurín el Grande (Málaga, Sur de España situado sobre depósitos marinos del Plioceno inferior permite una aproximación a la correlación marino-continental para esa época. El relleno sedimentario marino del Plioceno inferior en el conjunto de la cuenca de Málaga comprende tres secuencias transgresivas-regresivas (unidades Pl-1, Pl-2 y Pl-3 limitadas por discordancias. A techo de la secuencia intermedia Pl-2, sedimentos turbosos han liberado restos de Rodentia, Lagomorpha, Insectivora y Crocodylia. La presencia de Cricetus barrieri Mein & Michaux, 1970 en asociación con dos múridos, uno con morfología primitiva (Apodemus gudrunae Van de Weerd, 1976 y

  19. Evidence of a large deep conductive body within the basement of the Guadalquivir foreland Basin (Betic Cordillera, S-Spain) from tipper vector modelling: Tectonic implications

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    González-Castillo, L.; Galindo-Zaldívar, J.; Junge, A.; Martínez-Moreno, F. J.; Löwer, A.; Sanz de Galdeano, C.; Pedrera, A.; López-Garrido, A. C.; Ruiz-Constán, A.; Ruano, P.; Martínez-Martos, M.

    2015-11-01

    The Betic Cordillera is an Alpine belt formed by the interaction of the Eurasian and African plates and the westward motion of the Alboran Domain. Long Period Magnetotelluric observations at 26 sites in its westernmost part provide induction arrows that have been compared with 3D forward models including bathymetry and major geological bodies. The results highlight the presence of a major conductive body (0.05 Ω m) unknown to date and located within the basement of the Guadalquivir foreland basin. Aeromagnetic and field magnetic measurements further support the occurrence of magnetic anomalies related to the top of this anomalous body. This major structure is interpreted as an intermediate or basic igneous rock, with a high proportion of metallic mineralization. Its origin is discussed in the framework of the regional geological setting, possibly produced in the southern Iberian Variscan Massif by a huge concentration of volcanogenic massive sulphide (VMS) in the prolongation of the Iberian Pyrite Belt during Devonian-early Carboniferous times. Another possibility is that the conductive anomaly is due to magmatic intrusions associated with the Mesozoic fragmentation of Southern Iberia and the opening of the Tethys.

  20. The Eastern delta-fan deposits on the Granada Basin as tectonic indicators of the Sierra Nevada uplift (Betic Cordillera, South Spain)

    Science.gov (United States)

    Roldán, Francisco Javier; Azañon, Jose Miguel; Mateos, Rosa Maria

    2014-05-01

    Sierra Nevada uplift and with original NE-SW normal left-lateral fault system associated with a compatible ESE-WNW normal fault system. The asymmetrical morphologies of the two delta-fan bodies confirm this configuration as tectonic induced deposits. References Braga, J.C., Martín, J.M. and Alcalá, B. (1990). Coral reefs in coarse-terrigenous sedimentary environments (Upper Tortonian, Granada Basin, southern Spain). Sedimentary Geology, 66, pp 135-150. Clark, S.J.P.and Dempster, T.J. (2009). The record of tectonic denudation and erosion in an emerging orogen: an apatite fission-track study of the Sierra Nevada, southern Spain. Journal of the Geological Society, London, Vol. 166, pp. 87-100. Dabrio, C.J., Fernández, J., Peña, J., Ruíz-Bustos, A. y Sanz de Galdeano, C. (1978). Rasgos sedimentarios de los conglomerados miocénicos del borde noreste de la Depresión de Granada. Estudios Geológicos, 34, pp 89-97. García-García, F., Fernández, J., Viseras, C. and Soria, J.M. (2006). Architecture and sedimentary facies evolution in a delta stack controlled by fault growth (Betic Cordillera, southern Spain, late Tortonian). Sedimentary Geology, 185, pp. 79-92. García-García, F., Viseras, C. and Fernández, J. (1999). Organización secuencial de abanicos deltaicos controlados por la tectónica (Tortoniense superior, cuenca de Granada, Cordillera Bética). Rev. Soc. Geol. España, 12 (2): 199-208.

  1. Flow in the shallow mantle in the westernmost Mediterranean: insights from xenoliths in Plio-Pleistocene alkali basalts from the eastern Betic Cordillera (SE Spain)

    Science.gov (United States)

    Konc, Zoltán; Hidas, Károly; Garrido, Carlos J.; Tommasi, Andréa; Vauchez, Alain; Padrón Navarta, José Alberto; Marchesi, Claudio; Acosta-Vigil, Antonio; Szabó, Csaba; Varas-Reus, Maria Isabel

    2016-04-01

    Peridotite mantle xenoliths in Plio-Pleistocene alkali basalts of the eastern Betic Cordillera (Cartagena area, Murcia, SE Spain) provide a snapshot of the structure and composition of the lithospheric mantle at the northern limb of the Alpine Betic-Rif arched belt in the westernmost Mediterranean. The xenoliths are spinel and plagioclase lherzolite with minor harzburgite and wehrlite, displaying porphyroclastic to equigranular textures. Regardless of composition and texture, the Crystal Preferred Orientation (CPO) of olivine shows an axial-[100] pattern characterized by a strong alignment of [100]-axes near or parallel to the peridotite lineation and a girdle distribution of [010]-axes with a maximum normal to the peridotite foliation. This CPO pattern is consistent with ductile deformation accommodated by dislocation creep with dominant activation of the high temperature {0kl}[100] olivine slip system, indicative of deformation by simple shear or combinations of simple shear and pure shear with a transtensional component. Calculated seismic properties are characterized by fast propagation of P-waves and polarization of fast S-waves parallel to olivine [100]-axis, indicating the flow direction. SKS and Pn anisotropy in the eastern Betics can be explained by a lithospheric mantle peridotite with similar fabric to the one displayed by the studied mantle xenoliths. Considering the limited thickness of the mantle lithosphere in the Betics (40-80 km), the measured azimuths and delays of SKS waves in the eastern Betics are consistent with a steeply dipping mantle foliation and a subhorizontal lineation with ENE strike. This geometry of the lithospheric fabrics implies active or frozen mantle flow with a dominantly strike-slip component subparallel to the paleo-Iberian margin. Synkinematic overprinting of mineral assemblages from the garnet-spinel to the plagioclase facies demonstrates 36-40 km uplift continuously accommodated by ductile shear thinning of the

  2. The role of western Mediterranea tectonic evolution in the geometry of a karstic domain in the Betic Cordilleras (Sierra Gorda, Spain): Importance of a tardy extensional regime

    Science.gov (United States)

    Pistre, Séverin; Lopez-Chicano, Manuel; Pulido-Bosch, Antonio; Drogue, Claude

    1999-01-01

    Located in the central part of the Betic Cordilleras, the large carbonate Sierra Gorda Massif provides an example of a west-Mediterranean karstic aquifer. In spite of a complex polyphased tectonic history, the fracturing presents, from aerial views and at outcrop scale a quite organised geometry. Four fracture directions are found over the massif: N000-010, N050-070, N090-100 and N140-170. The statistical and geostatistical approach allows the characteristics (lengths, orientations) and the spatial structure for each fracture set to be determined. The NOOO-010 and N140-170 sets are grouped in packets whereas the two other sets are grouped in bands. The microtectonic study describes the evolution of the massif in the geodynamic context of this part of Mediterranea, distinguishing three recent stages of brittle tectonic activity in the massif: a WNW-ESE Middle Miocene compression, then a NNW-SSE to NW-SE compression with a poorly wrenching regime, and finally a probably pre-Quaternary N-S radial distension. This last stage is essential for the karstification of the massif and groundwater circulation. From the combined analysis of fracture network geometry and palaeostresses a multiple porosity model in agreement with hydrological observations made inside the massif can be proposed: in particular, the hectometric N090-100 (and N050-070) fractures which are essential for the network connectivity, and have a major drainage role at aquifer scale, while the N000-010 and N140-170 ones have a more local drainage role. This extensive tardy regime, which is for the first time described separately from the internal zones of the Cordilleras, must be considered as a significant phenomenon on a regional scale, and henceforth integrated in future geodynamic schemes of this part of Mediterranea.

  3. Curved fold-and-thrust accretion during the extrusion of a synorogenic viscous allochthonous sheet: The Estepa Range (External Zones, Western Betic Cordillera, Spain)

    Science.gov (United States)

    Pedrera, Antonio; MaríN-Lechado, Carlos; Martos-Rosillo, Sergio; RoldáN, Francisco Javier

    2012-08-01

    New structural, borehole, and time domain electromagnetic data allow us to reconstruct the 3-D geometry of the Estepa range (External Zones of the Western Betic Cordillera), which constitutes an isolated curved fold-and-thrust range made up of Jurassic shallow marine carbonates and Cretaceous to Paleocene marls and marly limestones. Contraction and rising load linked to the accretion of the Subbetic nappe enhanced the expulsion of Triassic evaporites and overpressured clays during the early and middle Miocene, finally forming part of a highly deformed mélange unit. This plastic extrusion favored the disconnection of External and Middle Subbetic blocks, including the Sierra de Estepa Range. There, deformation is characterized by northwest-vergent curved folds-and-thrusts associated with NE-SW frontal ramps and NW-SE lateral transfer faults that segmented the folds active between 18 and 12 Ma. At a local scale, curvature was achieved under a nearly uniform NW/WNW transport direction suggesting a primary arc type. Friction variation across the heterogeneous detached plastic basal Triassic unit mainly controlled the curvature and segmentation of the fold systems. Transport direction is consistent with previously published slip data from the Internal Subbetic and the Campo de Gibraltar units. After the Late Serravallian, accretion slowed down and a shallow marine unit deposited unconformably placed over the main thrust and folds. The sequence of deformation and emplacement of these ranges is interpreted as a continuous process linked to the early Miocene E continental collision of the Iberian margin thin continental crust and subduction of the Flysch trough oceanic crust beneath the Alboran continental domain.

  4. Geochemistry and tectonic setting of the «ophites» from the external zones ofthe Betic Cordilleras (S. Spain

    Directory of Open Access Journals (Sweden)

    Aguirre, L.

    1997-08-01

    Full Text Available Mesozoic basic magmatism in the External Zones of the Betic Cordilleras (S. Spain is represented by small tectonic bodies (ophites in Triassic formations, and submarine flows with abundant pillow-lavas interbedded with Jurassic sediments. Both basic igneous manifestations suffered very low- to low-grade metamorphism, more intense in the case of the ophites. Two types of ophites are distinguished on the basis of their primary mineralogy. In the first type, orthopyroxene is present in the less differentiated products. Clinopyroxene and Ca-plagioclase are the main primary phases and quartz appears in the more evolved rocks. In the second type, olivine is present in the less differentiated products. Ti-rich augite and Ca-plagioclase are also important primary minerals, but quartz is absent. Whole-rock chemistry (major and trace elements, including REE also allows us to discriminate between these two groups. The first group has higher SiO2, and lower TiO2, P2O5 and lower Na2O/K2O ratios than the second. Normative quartz is almost invariably present in this first group, whereas normative nepheline (lower than 5% is characteristic of the second group. Both groups are Sr, K, Ba, Rb, Th, Nb and Ce enriched with respect to normal MORB, but the first group has higher K, Rb, Ba, Th and lower Nb, Ce contents than the alkaline group. Nb/Y and Ti/V ratios are also different and show a tholeiitic affinity for the first group and transitional to alkaline for the second. Chondrite-normalised REE patterns in both groups are similar and characterized by LREE enrichment with respect to HREE. LREE/HREE ratios are, however, slightly higher in the transitional to alkaline group. Various discriminant tectonic diagrams indicate a continental intraplate setting for both ophite groups. This magmatism is related to the first extensional period of the Betic Cordilleras, during the Triassic-Jurassic. Geochemical differences between the two groups could evidence different

  5. Using nanogranitoids and phase equilibria modeling to unravel anatexis in the crustal footwall of the Ronda peridotites (Betic Cordillera, S Spain)

    Science.gov (United States)

    Bartoli, Omar; Acosta-Vigil, Antonio; Tajčmanová, Lucie; Cesare, Bernardo; Bodnar, Robert J.

    2016-07-01

    Anatexis in the crustal footwall of Ronda peridotites (Betic Cordillera, S Spain) is apparently related to the hot emplacement of this mantle slab over metasedimentary rocks. In this study, we combine the analysis of melt inclusions (MI) and phase equilibria calculations on quartzo-feldspathic mylonites (former migmatites) occurring at the contact with the mantle rocks, in the region of Sierra Alpujata (Ojén unit). The goal is to better characterize anatexis in these rocks and to provide new constraints on the geodynamic evolution of the crustal footwall. Such data are important for understanding the mechanisms of crustal emplacement of the mantle slice. The quartzo-feldspathic mylonites are characterized by the mineral assemblage Qtz + Pl + Kfs + Sil + Grt + Ilm + Bt ± Ap ± Gr. Clusters of MI are observed both at the core and toward the rim of peritectic garnet. In each cluster, MI range from totally glassy to nanogranitoids, consisting of Qtz + Kfs + Bt + Ms + Pl aggregates. The trapped melt is leucogranitic and peraluminous with variable Na2O/K2O values and low H2O contents (≈ 2-4 wt%). Phase equilibria modeling in the MnO-Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2-TiO2-O2-C (MnNCaKFMASHTOC) system with graphite-saturated fluid constrains the P-T conditions of melting at ≈ 6 kbar, ≈ 820 °C. MI data support the fluid-absent character of melting. The investigated MI represent the primary anatectic melts produced during prograde anatexis of the host rocks via biotite dehydration melting. Field, compositional, and textural observations indicate that mylonitic migmatites represent strongly deformed former diatexites. The comparison between the new data and some recently published information on migmatites located further from the contact with the peridotites and toward the bottom of the crustal footwall, raises some important issues which question the previously proposed geodynamic models for this region. Among them, (i) the crustal footwall at Sierra Alpujata

  6. At the craton edge: Geodynamic evolution of the southern Canadian Cordillera

    Science.gov (United States)

    DiCaprio, L.; Eaton, D. W. S.

    2016-12-01

    In the southern Canadian Cordillera, the thermal and mechanical interface with the craton may influence the geodynamic evolution of the lithosphere-asthenosphere system. Evidence including recent Rayleigh-wave tomography studies suggest that, beneath the southern Canadian Cordillera, the mantle lithosphere is virtually absent. Here, the boundary between craton and Cordillera also marks a step change in measured surface heat flux and a westward termination of magnetic anomalies. This study provides a numerical simulation of lithospheric-mantle removal by geodynamic processes that include delamination, viscous erosion, and mantle dripping. An additional constraint to the geodynamic model comes from thermochronologic data demonstrating long wavelength uplift of the cordilleran plateau in the Eocene. We have developed a suite of 2D visco-plastic models of a transect through the southern Canadian Cordillera and North American Craton. Sensitivity tests elucidate a range of geodynamic models that are consistent with tomographic results and the observed uplift history.

  7. Tectonics of the Western Betics: the role of E-W strike slip fault corridors

    Science.gov (United States)

    Frasca, Gianluca; Gueydan, Frédéric; Brun, Jean-Pierre; Célérier, Bernard

    2014-05-01

    The tectonic origin of the arcuate Betic-Rif orogenic belt that surrounds the Alboran Sea at the western tip of the Mediterranean Sea remains debated. Here, we investigate the tectonic units cropping out in the Western Betics (Malaga region, Southern Spain) with the main goal of reconstructing the Oligo-Miocene evolution of the area. New structural data and geological mapping together with available data allow us to identify the main structural features of the area. Deformation is found to be extremely diffused but two E-W elongated tectonic blocks with different lithological composition are outlined by marked E-W dextral strike-slip corridors ending up in horse-tail splays. These E-W strike slip corridors are responsible for late Miocence tectonics of both the internal and external zones of the Betic Cordillera.

  8. Orogenesis at the southern tip of the Americas: the structural evolution of the Cordillera Darwin metamorphic complex, southernmost Chile

    Science.gov (United States)

    Cunningham, W. Dickson

    1995-04-01

    New, detailed lithologic and structural data are presented from three separately mapped areas along the southern boundary of the Cordillera Darwin metamorphic complex of southernmost Chile. Cordillera Darwin is a unique uplift because it exposes the highest grade rocks in the Andes south of Peru and averages 1 km higher in elevation than adjacent areas. The structural data indicate that Cordillera Darwin experienced mid-Late Cretaceous trans-pressional deformation with a partitioned strike-slip component localized along the Beagle Channel that forms the southern boundary to the range. Foliation, lineation and fold axis trends indicate NE-SW-directed contraction and NW-SE strike-slip shearing (present directions) during progressive {D1}/{D2} Andean deformation. D2 deformation is marked by outcrop-to 10 km-scale south-southwest-vergent folds. Late Cretaceous-Tertiary brittle-ductile and brittle left-lateral strike-slip faults and shear zones crosscut all {D1}/{D2} structures. Although limited structural evidence for extensional tectonics was documented in this study, apparent normal offsets across both arms of the Beagle Channel and previously documented field evidence for extension from other areas in Cordillera Darwin suggest that transtensional displacements also may have occurred in southern Cordillera Darwin during the Late Cretaceous-Early Tertiary. Cordillera Darwin's position within the evolving Patagonian Orocline adjacent to an evolving Mesozoic-Cenozoic left-lateral transform boundary between the South American and Antarctic plates, and later the South American and Scotia plates, necessitates consideration of the possible effects of regional counterclockwise rotation on development of structures. Regional counterclockwise rotation of Cordillera Darwin may have controlled the temporal and spatial transition of deformational regimes within Cordillera Darwin. Exhumation of the metamorphic core of Cordillera Darwin during the Late Cretaceous-Early Tertiary is

  9. Nucleation, linkage and active propagation of a segmented Quaternary normal-dextral fault: the Loma del Viento fault (Campo de Dalías, Eastern Betic Cordillera, SE Spain)

    Science.gov (United States)

    Pedrera, Antonio; Marín-Lechado, Carlos; Stich, Daniel; Ruiz-Constán, Ana; Galindo-Zaldívar, Jesús; Rey-Moral, Carmen; de Lis Mancilla, Flor

    2012-02-01

    Active faults from the Campo de Dalías (SE Betic Cordillera) allow us to constrain the deformation styles involved in the development of segmented oblique-slip faults. This sector constitutes the widest outcrop of Plio-Quaternary sediments in the northern boundary of the Alboran Sea. It has emerged since the Late Pliocene, and therefore provides recent deformation markers that are not disturbed by erosive processes. The faults started to grow during the Pleistocene, reactivating previous hybrid joints, with a normal-dextral slip. We present a detailed map of the largest fault in the area, the Loma del Viento fault, comprising six onshore segments. Based on field work and aerial photography, the distributions of the contiguous joints have been mapped, and the joints reactivated as faults are identified. Some of these fault segments are hard-linked, and fault slip enhances toward the linkage sectors between them with associated sedimentary depocenters. An electrical tomography profile reveals the wedge geometry of a unit of Pleistocene conglomerates and red silts that were coevally deposited during the fault movement. Long-term slip rate in the central part of the fault is estimated at 0.07 ± 0.03 mm/y. In addition, a seismic crisis nucleated close to the Loma del Viento fault during November 2010 was recorded. Moment tensor analysis of the two mainshocks (Mw 3.5 and 4.2) provides a focal solution indicating a N120°E striking right-lateral strike-slip fault. The corrugated morphology of the Loma del Viento fault may have influenced its seismic behavior. Some of the fault segments are oblique to the general motion of the fault. These oblique segments would provide higher resistance against the general fault motion and could lock the fault, leading to accumulate elastic energy.

  10. Palaeogene to Early Miocene sedimentary history of the Sierra Espuña (Malaguide complex, internal zone of the Betic cordilleras, SE Spain. Evidence for extra-Malaguide (Sardinian? provenance of oligocene conglomerates: Palaeogeographic implications

    Directory of Open Access Journals (Sweden)

    Geel, T.

    1996-12-01

    Full Text Available The Sierra Espuña is situated at the northern edge of the Internal Zone in the eastern Betic Cordilleras and is part of the unmetamorphosed Malaguide Complex. Palaeontological and sedimentological analysis of the Eocene to Aquitanian sediments on the northwest side of the Espuña yielded unexpected new information of importance for the reconstruction of the history of the Espuña itself and the Malaguides in general. The socalled Upper Eocene (Auversian rocks are of Early Oligocene (P20 age and contain supermature detritus derived from outside the Malaguide realm. The hundreds of meters thick limestone conglomerate formation of the Espuña is of Middle Oligocene (P21 age and represents a backstepping fan delta complex at the margin of a carbonate platform situated to the northeast of the Espuña. Analysis of the clasts suggests that this platform was a part of the north Sardinian block given the majority of fragments of Upper Jurassic sheltered inner platform (Clypeina-Trocholina limestones and dolomites. Contrary to former views (Paquet, 1966; Lonergan, 1993, the conglomerates cannot be considered to be the erosional products of Malaguide imbricated units. Therefore, one of the main arguments for early (Late Eocene to Oligocene thrusting and nappe emplacement in the Espuña area is not valido Other arguments for early kinematics are discussed, among others the allegedly continuous sedimentation from the Late Eocene until the Langhian northwest of the Espuña. Our data indicate the existence of a stratigraphic gap, comprising the middle Aquitanian to middle Burdigalian. A new model for the development of the Espuña within the Malaguide realm during the Palaeogene to Early Miocene is presented. Main thrusting and nappe emplacement is thought to have been taken place during the late Aquitanian. Finally, the recently proposed 2000 clockwise rotation of the Espuña as a coherent block during the Early to Middle Miocene (AlIerton el al., 1993 is

  11. P-wave tomographic images in the Central Betics-Alborán Sea (South Spain) using local earthquakes: Contribution for a continental collision

    Science.gov (United States)

    Serrano, Inmaculada; Morales, José; Zhao, Dapeng; Torcal, Federico; Vidal, Francisco

    To investigate the relationship between shallow and intermediate-depth earthquakes and the crust and upper mantle structure beneath the Betic-Cordillera and Alborán sea region, we have applied seismic tomography to 2569 P-wave arrival times from 367 microearthquakes recorded by both permanent and temporary seismic stations deployed in the region. These earthquakes occurred in the depth range of 0 to 110 km beneath the Central Betic Cordilleras and Alborán sea. Our results have revealed significant structural heterogeneities in the crust and upper mantle beneath the study area. In the upper crust there is a high-velocity anomaly at Sierra Gorda (western boundary of the Granada basin) penetrating to 15 km depth, which is in good agreement with the aeromagnetic anomaly. In the Granada basin, a low-velocity anomaly is located in the middle crust, which coincides with a previously detected greater cutoff depth of seismicity, and are considered to be associated with a highly fractured zone generated by an intracrustal detachment. The northern boundary of the Alborán sea (Málaga coast) is well imaged as low velocities from 50 to 90 km depths. This low-velocity zone in the upper mantle is associated with the intermediate-depth seismicity, which outline a section of continental crust related to the collision/subduction beneath the northern part of the Alborán sea-southern part of the Central Betics.

  12. Recent large fold nucleation in the upper crust: Insight from gravity, magnetic, magnetotelluric and seismicity data (Sierra de Los Filabres-Sierra de Las Estancias, Internal Zones, Betic Cordillera)

    Science.gov (United States)

    Pedrera, Antonio; Galindo-Zaldívar, Jesús; Ruíz-Constán, Ana; Duque, Carlos; Marín-Lechado, Carlos; Serrano, Inmaculada

    2009-01-01

    Rheological heterogeneities in the upper-crust have a close relationship with the fold position where rigid bodies could constitute initial perturbations that allow the nucleation of folds. Consequently, establish the position and geometry of anomalous rocks located in the upper-crust by geophysical studies help to understand the folded structure observed on surface. New geological observations in the field, along with gravity, magnetic, magnetotelluric and seismicity data, reveal the subsurface structure in the Sierra de Los Filabres-Sierra de Las Estancias folded region part of the Alpine belt in southern Spain. The geometry of the upper crust is determined by geological field data, 2D gravity models, 2D magnetic models and 2D MT resistivity model, while seismicity evidences the location of the deep active structures. These results allow us to propose that a basic rock body at 4 to 9 km depth has determined the nucleation and development of the Sierra de Los Filabres kilometric antiform. N-vergent large late folds are subjected to a variable present-day stress field. Earthquake focal mechanisms suggest the presence in depth of a regional NW-SE compressive stress field. However, most of the seismogenetic structures do not extend up to the surface, where NW-SE and WNW-ESE outcropping active normal faults are observed, thus indicating a NE-SW extension in the upper crust simultaneous to orthogonal NW-SE compression related to reverse faults and minor folds developed in the Eastern Almanzora Corridor and in the nearby Huércal-Overa Basin. The recent and active tectonic studies of cordilleras hinterland subjected to late folding greatly benefits from the integration of surface observations together with geophysical data.

  13. Syntectonic remagnetization in the southern Methow block: Resolving large displacements in the southern Canadian Cordillera

    Science.gov (United States)

    Enkin, R.J.; Mahoney, J.B.; Baker, J.; Kiessling, M.; Haugerud, R.A.

    2002-01-01

    The Upper Cretaceous Ventura Member of the Goat Wall unit in the southern Methow block of southern British Columbia and northern Washington State holds a syntectonic magnetization. Eight new sites from Manning Park in British Columbia give a mean direction of D = 27.5??, I = 60.1??, k = 304.7, ??95 = 3.2?? after optimal partial tilt correction. Of five groups of bedded sites from farther south in the basin reported by Bazard et al. [1990], four have a syntectonic remanence with a direction similar to what we observe. The exception is one group which has optimal concentration of remanence directions on >100% untilting and an abherent direction which must be rejected. Combining the accepted sites, the optimal differential syntilting direction is D = 11.8??, I = 61.5??, k = 39.3, ??95 = 3.4?? (N = 47), giving a mean pole of 79.8??N, 359.2??E, K = 19.5, and A95 = 4.8??. The age of the remagnetization is constrained to be between 88 and 80 Ma. Compared to cratonic North America, this result indicates that the southern Methow block was displaced from the south by 1800 ?? 500 km, meaning it lay south of the Sierra Nevada subduction zone but well north of other paleomagnetically constrained Cretaceous rock units from the Insular superterrane, including correlative strata of the Mount Tatlow area in the northern Methow block. Among several possibilities to reconcile this discrepancy, the most plausible has the whole Methow block translated coherently but with the southern Methow block strata remagnetized during transit.

  14. Oligocene-to-Early Miocene depositional and structural evolution of the Calabria-Peloritani Arc southern terrane (Italy) and geodynamic correlations with the Spain Betics and Morocco Rif

    Science.gov (United States)

    Bonardi, Glauco; de Capoa, Paola; Di Staso, Angelida; Estévez, Antonio; Martín-Martín, Manuél; Martín-Rojas, Iván; Perrone, Vincenzo; Tent-Manclús, José Enrique

    2003-11-01

    The Calabria-Peloritani Arc southern terrane is a stack of crystalline basement nappes, some of them provided with a widely outcropping Alpine sedimentary cover, sealed by clastics of the Stilo-Capo d'Orlando Formation (SCOF). New field observations in the Stilo area lead to define a Pignolo Formation as a sedimentary cycle predating the emplacement of the uppermost nappe (Stilo Unit) of the tectonic pile. It includes the well-known Lithothamnium and larger foraminifers bearing calcarenites, previously interpreted as a basal member of the SCOF. The biostratigraphic revision of both formations, together with recently published data about other preorogenic deposits, point to a stacking of the whole terrane between the Aquitanian and the middle-late Burdigalian. A comparison between the sedimentary cycles characterising the Calabria-Peloritani southern terrane during the Oligocene-Early Miocene and those almost coeval of the Betic-Rifian internal units highlights their quite similar evolution. Thus it is reliable that both the orogenic belts originated from contiguous paleogeographic realms. These considerations confirm that the present western Mediterranean Chains were originally segments of a continuous orogenic belt disrupted by the opening of the Balearic and Tyrrhenian basins.

  15. Initiation of continental accretion in the Betic-Rif domain

    Science.gov (United States)

    Maxime, Daudet; Frederic, Mouthereau; Stéphanie, Brichau; Ana, Crespo-Blanc; Arnaud, Vacherat

    2017-04-01

    The Betic - Rif cordillera in southern Spain and northern Morocco, respectively, form one of the tightest orogenic arc on Earth. The formation of this arcuate orogenic belt resulted from the westward migration of the Alboran crustal domain, constituted by the internal zone of the orogeny and the basement of the Alboran back-arc basin, that collided with the rifted margins of Iberia and Africa at least since the early Miocene. This collision is intimately linked to the post-35-30Ma regional slab roll-back and back-arc extension in the western Mediterranean region. The geodynamics of the Betic-Rif domain, which is of great importance for the paleogeographic reconstructions of the Tethys-Altantic and the Mediterranean sea, is still largely debated. Answers will come from a more detailed structural analyses, including refinement of the time-temperature paths and kinematics of the main structural units, which is one of the main objectives of the OROGEN research project, co-financed by BRGM, TOTAL & CNRS. In this study, we focus on the well-developed flysch-type sediments now accreted in the Betics-Rif but initially deposited in a basin, north of the african margin and on the iberian margin from the Early Cretaceous to the Early Miocene. Using low-temperature thermochronology (fission-track and (U-Th)/He analyses) combined with zircon U-Pb geochronology on the flyschs deposited on the most distal part of the margin, we aim to constrain the thermal history of both the source rocks and accreted thrust sheets at the earliest stages of continental accretion. Sample have been collected in flyschs series ranging from Mesozoic, Paleogene to Neogene ages. Additional samples have been collected in the Rif where Cretaceous series are more developed. Combined with a detailed structural analysis, LT thermochronological constraints will refine the kinematics of thrust units when continental accretion started before the final thrust emplacement occurred in the Early Miocene

  16. A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate

    Science.gov (United States)

    Bromley, Gordon R. M.; Schaefer, Joerg M.; Hall, Brenda L.; Rademaker, Kurt M.; Putnam, Aaron E.; Todd, Claire E.; Hegland, Matthew; Winckler, Gisela; Jackson, Margaret S.; Strand, Peter D.

    2016-09-01

    Resolving patterns of tropical climate variability during and since the last glacial maximum (LGM) is fundamental to assessing the role of the tropics in global change, both on ice-age and sub-millennial timescales. Here, we present a10Be moraine chronology from the Cordillera Carabaya (14.3°S), a sub-range of the Cordillera Oriental in southern Peru, covering the LGM and the first half of the last glacial termination. Additionally, we recalculate existing 10Be ages using a new tropical high-altitude production rate in order to put our record into broader spatial context. Our results indicate that glaciers deposited a series of moraines during marine isotope stage 2, broadly synchronous with global glacier maxima, but that maximum glacier extent may have occurred prior to stage 2. Thereafter, atmospheric warming drove widespread deglaciation of the Cordillera Carabaya. A subsequent glacier resurgence culminated at ∼16,100 yrs, followed by a second period of glacier recession. Together, the observed deglaciation corresponds to Heinrich Stadial 1 (HS1: ∼18,000-14,600 yrs), during which pluvial lakes on the adjacent Peruvian-Bolivian altiplano rose to their highest levels of the late Pleistocene as a consequence of southward displacement of the inter-tropical convergence zone and intensification of the South American summer monsoon. Deglaciation in the Cordillera Carabaya also coincided with the retreat of higher-latitude mountain glaciers in the Southern Hemisphere. Our findings suggest that HS1 was characterised by atmospheric warming and indicate that deglaciation of the southern Peruvian Andes was driven by rising temperatures, despite increased precipitation. Recalculated 10Be data from other tropical Andean sites support this model. Finally, we suggest that the broadly uniform response during the LGM and termination of the glaciers examined here involved equatorial Pacific sea-surface temperature anomalies and propose a framework for testing the viability

  17. Evolution and hazard analysis of high-mountain lakes in the Cordillera Vilcabamba (Southern Peru) from 1991 to 2014

    Science.gov (United States)

    Guardamino, Lucía; Drenkhan, Fabian

    2015-04-01

    In recent decades, glaciers in high-mountain regions have experienced unprecedented glacier retreat since the Little Ice Age (LIA). This development triggers the formation and growth of glacier lakes, which in combination with changes in glacier parameters might produce more frequent conditions for the occurrence of disasters, such as Glacier Lake Outburst Floods (GLOF). Facing such a scenario, the analysis of changing lake characteristics and identification of new glacier lakes are imperative in order to identify and reduce potential hazards and mitigate or prevent future disasters for adjacent human settlements. In this study, we present a multi-temporal analysis with Landsat TM 5 and OLI 8 images between 1991 and 2014 in the Cordillera Vilcabamba region (Southern Peru), a remote area with difficult access and climate and glaciological in-situ data scarcity. A semi-automatic model was developed using the band ratios Normalized Difference Snow Index (NDSI) and Normalized Difference Water Index (NDWI) in order to identify glacier and lake area changes. Results corroborate a strong glacier area reduction of about 51% from 1991 (200.3 km²) to 2014 (98.4 km²). At the same time, the number of lakes (total lake surface) has increased at an accelerated rate, from 0.77% (0.48%) in 1991 to 2.31% (2.49%) in 2014. In a multiple criteria analysis to identify potential hazards, 90 out of a total of 329 lakes in 2014 have been selected for further monitoring. Additionally, 29 population centers have been identified as highly exposed to lake related hazards from which 25 indicate a distance less than 1 km to an upstream lake and four are situated in a channel of potential debris flow. In these areas human risks are particularly high in view of a low HDI below Peru's average and hence pronounced vulnerability. We suggest more future research on measurements and monitoring of glacier and lake characteristics in these remote high-mountain regions, which include comprehensive risk

  18. Middle-Miocene (Serravallian) temperate carbonates in a seaway connecting the Atlantic Ocean and the Mediterranean Sea (North Betic Strait, S Spain)

    Science.gov (United States)

    Braga, Juan C.; Martín, José M.; Aguirre, Julio; Baird, Catherine D.; Grunnaleite, Ivar; Jensen, Niels Bo; Puga-Bernabéu, Angel; Sælen, Gunnar; Talbot, Michael R.

    2010-03-01

    Miocene deposits in the contact area between the Prebetic and Subbetic domains (Betic Cordillera, S Spain) record the last stages of marine deposition on the southern Iberian margin and the final closure of the North Betic Strait in the early Tortonian (Late Miocene). Serravallian (Middle Miocene) shallow-water carbonates and mixed carbonate-siliciclastics formed on a platform at the southern margin of the North Betic Strait. These shallow-water deposits, informally termed the La Escalera Formation, onlap an erosion surface carved into underlying Miocene and older rocks. Carbonate components are mainly bryozoans, coralline red algae, molluscs, and benthic and planktonic foraminifers, typical of heterozoan lithofacies. Several facies types can be distinguished based on different grain sizes and sedimentary structures. Large-scale geometries and stratigraphic facies relationships indicate that the La Escalera Formation was deposited on a homoclinal ramp attached to a deeply eroded, emergent relief to the south. A beach system developed at the southern margin, with backshore lagoons and local incursions of coarse terrigenous sediments. Seawards of the beach system was a submarine-dune belt that extended over several square kilometres at the northeastern end of the La Escalera Formation. Longshore currents shifted submarine dunes to the northeast. Maximum production of carbonate skeletons took place seawards of the dune field. From this factory area, skeletal debris was moved landwards and incorporated into the dunes and beaches, whereas other skeletal particles were transported downslope by storms and fed a facies belt with hummocky and swaley cross-stratified sediments. The finest-grained particles accumulated below a storm-wave base, along with significant planktic debris. Carbonate deposits change laterally westwards to terrigenous sediments formed in similar facies belts. Terrigenous influx limited carbonate production on the western part of the ramp by disturbing

  19. Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

    Science.gov (United States)

    Audin, Laurence; Lacan, Pierre; Tavera, Hernando; Bondoux, Francis

    2008-11-01

    The South America plate boundary is one of the most active subduction zone. The recent Mw = 8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, at a longer time scale, a recurrent Quaternary transtensive tectonic activity of the CFS is expressed by offset river gullies and alluvial fans. The presence of such extensional fault systems trending orthogonal to the trench along the Coastal Cordillera in southern Peru is interpreted to reflect a strong coupling between the two plates. In this particular case, stress transfer to the upper plate, at least along the coastal fringe, appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake. The seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones. However, after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern Peru, we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern Peru continental margin.

  20. Late Cretaceous-Cenozoic Evolution of the Central Andean Foreland Basin System in the Eastern Cordillera to Subandean Zone, Southern Bolivia

    Science.gov (United States)

    Calle, A.; Horton, B. K.; Anderson, R. B.; Long, S. P.

    2015-12-01

    Evaluation of foreland basin deposystems and provenance across southern Bolivia reveals punctuated growth of the central Andean orogenic wedge. New and published sedimentology, provenance data, stratigraphy, subcrop mapping, and apatite (U-Th)/He thermochronometry along two transects (19.5, 21°S) from the easternmost Eastern Cordillera (EC) to the western Subandean Zone (SAZ) shed light on Late Cretaceous-Miocene thrust belt and foreland basin dynamics. Sediment dispersal patterns are constrained by paleocurrents, detrital zircon U-Pb geochronology, sandstone petrography, and conglomerate clast compositions. Spatial and temporal changes in the Andean thrust belt are recorded in asymmetric foreland basin thicknesses, facies distributions, and provenance within the EC (Incapampa and Camargo synclines) and SAZ (El Rosal and Entre Rios synclines). The >4 km uppermost Cretaceous-lower Miocene EC succession and ~2.5 km upper Oligocene-Miocene SAZ clastic successions record a shift from fluvial backbulge to pedogenic forebulge deposition. Braided, meandering, and lacustrine foredeep deposition records the most-rapid subsidence, with a later shift to progradational braided and alluvial fan deposition in the wedge-top zone. Growth strata preserved in EC and SAZ wedge-top deposits suggest unsteady eastward advance of the deformation front. Distal foreland deposits show west-directed paleocurrents with >1 Ga detrital zircon populations. Emerging Andean sources are indicated by east-directed paleocurrents, 36-25 Ma), Interandean Zone (IAZ, ~22-7 Ma) and SAZ (<6 Ma) can be linked to eastward passage of a flexural forebulge, recorded as a 50-200 m thick condensed zone in EC and SAZ basin fill. Integrated assessment of basin architecture, provenance, and exhumation highlights the potential influence of pre-Cenozoic IAZ heterogeneities on orogenic wedge growth.

  1. TRANSGRESSIVE SEQUENCES ON FORELAND MARGINS: A CASE STUDY OF THE NEOGENE CENTRAL GUADALQUIVIR BASIN, SOUTHERN SPAIN

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    J. GABRIEL PENDÓN

    2004-07-01

    Full Text Available The Guadalquivir foreland basin, located between the Iberian basement northward and the Betic orogen to the South, represents the western sector of the earlier foredeep basin of the Betic Cordillera. Along the northern foreland margin, the sedimentary fill of this basin includes a Tortonian Basal Transgressive Complex (BTC, composed of five internal sequences bounded by transgressive surfaces. Two main parts are distinguished within each sequence: the lower transgressive lag deposits, and the upper stillstand/prograding sediments. Three facies associations were distinguished within this stratigraphic succession along the central sector of this basin margin: unfossiliferous conglomerates and coarse-grained sands (A, fossiliferous conglomerates and coarse-grained sands (B, and yellow medium-coarse-grained fossiliferous sands (C. A fourth facies association (D: blue silty marlstones and shales overlies the BTC. Deposits of alluvial sediments (facies association A and shallow-marine/foreshore sediments (facies association C, were recurrently interrupted by transgressive pulses (facies associations B and C. Every pulse is recorded by an erosional, cemented sandy-conglomerate bar with bivalves (Ostreidae, Isognomon, balanids, gastropods and other marine bioclasts; or their transgressive equivalents. The lateral facies changes in each individual sequence of the BTC are related to: (1 the influence on the northern foreland margin of the tectonic activity of the southern orogenic margin; (2 the palaeorelief formed by irregularities of the substrate which controls the sediment dispersal; and (3 the evolution stages of the sedimentary systems. 

  2. Morphotectonics of the Padul-Nigüelas Fault Zone, southern Spain

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    Jochen Hürtgen

    2014-02-01

    Full Text Available The Padul-Nigüelas Fault Zone (PNFZ is situated at the south-western mountain front of the Sierra Nevada (southern Spain in the Internal Zone of the Betic Cordilleras and belongs to a NW-SE trending system of normal faults dipping SW. The PNFZ constitutes a major tectonic and lithological boundary in the Betics, and separates the metamorphic units of the Alpujárride Complex from Upper Tertiary to Quaternary deposits. Due to recent seismicity and several morphological and geological indicators, such as preserved fault scarps, triangular facets, deeply incised valleys and faults in the colluvial wedges, the PNFZ is suspected to be a tectonically active feature of the south-eastern Granada Basin. We performed morphotectonic GIS analyses based on digital elevation models (DEM, cell size: 10 m to obtain tectonic activity classes for each outcropping segment of the PNFZ. We have determined the following geomorphic indices: mountain front sinuosity, stream-length gradient index, concavity index and valley floor width to height ratio. The results show a differentiation in the states of activity along the fault zone strike. The western and eastern segments of the PNFZ indicate a higher tectonic activity compared to the center of the fault zone. We discuss and critically examine the comparability and reproducibility of geomorphic analyses, concluding that careful interpretation is necessary, if no ground-truthing can be performed.

  3. Sulphide and sulphosalt mineralogy and paragenesis from the Sierra Almagrera veins, Betic Cordillera (SE Spain

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    Martínez Frías, J.

    1991-12-01

    Full Text Available The Sierra Almagrera vein-type mineralization contains base metal sulphides and Pb-Sb- Cu-Ag sulphosalts. The sulphides possess significant proportions of Ag, Sb (galena, Fe (sphalerite and Sb, Zn (chalcopyrite. Ore microscopy and electron microprobe have revealed a mineralogical and textural variation and confirmed the presence of bournonite, boulangerite and anomalous tetrahedrite. The average sulphosalt formulas are bournonite Cu0.98 Pb0. 96 Sb0.98 S3.04, boulangerite Pb4.8Sb3.8S11.34 and anomalous tetrahedrite Ag0.6Cu9.7 Zn3.6 Fe0. 44 Sb3.47 S13- The sequence of mineral deposition indicates the existance of four mineralizing stages and one supergene alteration: 1 Fe-(As; 2 Zn-Cu-Fe; 3 Pb-Sb-Cu-Ag; 4 Cu-Zn-Fe, and 5 carbonates, sulphates and supergene oxides. In broad terms, it is possible to establish the following conclusions: a there exist a mineralogical and textural variation with depth, the Pb-Sb-Cu-Ag stage reaching the maximum development; b a temperature decrease during the formation of sph. 1, linked to the progressive increase in Fe-content of the sphalerite has been detected; c the compositional homogeneity of the bournonite (and the fair lack of As in the tetrahedrite could indicate the existance of a possible tendancy to individually crystallise the Sb and As sulphosalts, according to the trend Bi → Sb → As.La mineralización filoniana de Sierra Almagrera presenta una interesante paragénesis caracterizada por la presencia de sulfuros de metales base y sulfosales de Pb-Sb-Cu-Ag. Se ha identificado una secuencialidad textural y química de las distintas fases minerales, según la cual los sulfuros poseen variaciones significativas de las proporciones de Ag, Sb (galena, Fe (esfalerita, y Sb, Zn (calcopirita, yen la que las sulfosales son fundamentalmente sulfoantimoniuros (bournonita: Cu0.98 Pb0. 96 Sb0.98 S3.04, boulangerita Pb4.8Sb3.8S11.34 y tetraedrita anómala Ag0.6Cu9.7 Zn3.6 Fe0. 44 Sb3.47 S13-. La secuencia de deposición mineral indica la existencia de cuatro etapas de mineralización y una de alteración supergénica: 1 Fe-(As; 2 Zn-Cu-Fe; 3 Pb-Sb-Cu-Ag; 4 Cu-Zn-Fe, y 5 carbonatos, sulfatos y óxidos supergénicos. De acuerdo con los datos obtenidos, se ha establecido que: a existe una variación mineralógica y textural con la profundidad, siendo la tercera etapa mineralizadora la que alcanza un mayor desarrollo; b se observa un decrecimiento de la temperatura (probablemente sin variación de presión, durante la formación de la esfalerita de primera generación (sph.I, atendiendo al incremento progresivo de su contenido en hierro, y c la homogeneidad composicional de la bournonita (junto con la ausencia de arsénico en la tetraedrita, podría indicar una tendencia de cristalización individualizada de las fases de Sb y As, de acuerdo con la tendencia normal: Bi → Sb → As.

  4. Suitability of the Betic Cordillera marly materials for the manufacture of pressed tile

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    Jiménez-Millán, J.

    2009-06-01

    Full Text Available This paper assesses the aptness of Carbonero Formation (in the Spanish province of Jaén marls for the manufacture of high added value ceramic construction materials. Lithologically speaking, the Carbonero Formation comprises three members: a a marly lower member; b a radiolaritic middle member; and c a turbiditic upper member. The samples studied were rich in phyllosilicates (> 39% and calcite. The quartz and feldspar contents were low ( 20 µm fraction was absent. Due to their low plasticity, most Carbonero Formation marls can only be pressure moulded. Their high linear shrinkage and water absorption values when fired at 800 to 1 000 ºC make them poorly suited for use in the ceramic industry. Blends of these marls with different proportions of supplementary materials may be apt for manufacturing light shades of pressed ceramic tile.Este trabajo evalúa las posibilidades cerámicas de las margas de la Formación Carbonero para fabricar materiales cerámicos de construcción de alto valor añadido. Litológicamente, la Formación Carbonero está formada por tres miembros: a Inferior Margoso, b Intermedio Radiolarítico y c Superior Turbidítico. Las muestras estudiadas son ricas en filosilicatos (> 39% y calcita. Los contenidos en cuarzo y feldespatos son bajos ( 20 µm está ausente. La plasticidad de las margas es baja, condicionando que su moldeo deba ser exclusivamente por presión. Los altos valores de contracción lineal y absorción de agua entre 800 y 1.000 ºC son poco apropiados para la industria cerámica. Las mezclas de estos materiales con diferentes proporciones de materiales complementarios permitirían la fabricación de baldosas cerámicas de color claro por prensado.

  5. Tomoceridae (Collembola, Entomobryomorpha from the southern Annamitic cordillera: redescription of Tomocerus ocreatus Denis, 1948 and description of a new species of Tomocerina Yosii, 1955

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    Daoyuan Yu

    2016-02-01

    Full Text Available Two species of Tomoceridae were found near Dalat, southern Vietnam. Tomocerus ocreatus Denis, 1948 is redescribed based on a neotype specimen. Previous records of Tomocerus ocreatus in non-type localities are reevaluated. A new species Tomocerina annamitica sp. nov. is described. The new species is mainly characterized by its small body size, pointed tenent hair, compound dental spines and the absence of intermediate teeth on mucro.

  6. Seismic anisotropy and velocity structure beneath the southern half of the Iberian Peninsula

    Science.gov (United States)

    Serrano, I.; Hearn, T. M.; Morales, J.; Torcal, F.

    2005-06-01

    Travel times of 11,612 Pn arrivals collected from 7675 earthquakes are inverted to image the uppermost mantle velocity and anisotropy structure beneath the southern half of the Iberian Peninsula and surrounding regions. Pn phases are routinely identified and picked for epicentral distances from 200 to 1200 km. The method used in this study allows simultaneous imaging of variations of Pn velocity and anisotropy. The results show an average uppermost mantle velocity beneath the study area of 8.0 km/s. The peninsular area covered by the Iberian massif is characterized by high Pn velocity, as expected in tectonically stable regions, indicating areas of the Hercynian belt that have not recently been reactivated. The margins of the Iberian Peninsula have undergone a great number of recent tectonic events and are characterized by a pronouncedly low Pn velocity, as is common in areas greatly affected by recent tectonic and magmatic activity. Our model indicates that the Betic crustal root might be underlined by a negative anomaly beneath the southeastern Iberian Peninsula. In the Atlantic Ocean, we find a sharp variation in the uppermost mantle velocities that coincides with the structural complexity of the European and African plate boundary in the Gulf of Cadiz. Our results show a very pronounced low-velocity anomaly offshore from Cape San Vicente whereas high velocities are distributed along the coast in the Gulf of Cadiz. In the Alboran Sea and northern Morocco, the direction of the fastest Pn velocity found is almost parallel to the Africa-Eurasia plate convergence vector (northwest-southeast) whereas to the north, this direction is almost parallel to the main trend of the Betic Cordillera, i.e. east-west in its central part and north-south in the curvature of the Arc of Gibraltar. This suggests that a significant portion of the uppermost mantle has been involved in the orogenic deformation that produced the arcuate structure of the Betic Cordillera. However, we

  7. First U-Pb detrital zircon ages from Numidian sandstones in Southern Apennines (Italy): Evidences of African provenance

    Science.gov (United States)

    Fornelli, Annamaria; Micheletti, Francesca; Langone, Antonio; Perrone, Vincenzo

    2015-05-01

    Two samples of quartz-rich sandstones collected in the Numidian Flysch of Southern Apennines (Italy) have been studied to highlight the provenance of detritus using radiometric dating by LA-ICP-MS of detrital zircons and to compare the obtained ages with those of the Betic and Maghrebian Chains. The provenance of quartzose detritus from European or African Plates is still debated in these Chains, accordingly the ages of the detrital zircons can contribute significantly to discriminate the origin of the quartzose supply. The U-Pb zircon ages (n = 47) vary from 3047 ± 13 Ma (Mesoarchean) to 516 ± 19 Ma (Cambrian). The predominance of Paleo-Proteozoic ages (2500-1600 Ma) and the lack of Hercynian and Alpine ones suggest a provenance of the Numidian supply from North-African cratonic areas during the early-middle Langhian, when the Numidian successions of Southern Apennines were deposited. In addition, a cluster of ages at 773 ± 24 Ma and 668 ± 12 Ma in one sample and at 664 ± 17 Ma in the other sample, calculated on zircon domains with magmatic zoning, testify to an important contribution from Neo-proterozoic "granitic" rocks widely outcropping in the North-African Craton. The age data on detrital zircons from Numidian sandstones in Southern Apennines overlap those found in the Numidian sandstones widespread in the Betic Cordillera and in the Maghrebian Chain from south Spain to Sicily. This suggests that the entire depositional zone in which Numidian Flysch deposited, was fed from a southerly source represented by the African Craton where Archean, Proterozoic and Cambrian rocks widely crop out from the Atlantic coast to the Hoggar and Tibesti Massifs. Finally, it must be outlined that a Meso-Archean zircon age (3047 Ma) has been found in the Numidian Flysch of the Southern Apennines whereas in the Numidian Flysch of the Maghrebian Chain, zircons older than Paleo-proterozoic (1840 Ma) have not yet been found.

  8. The 'Tortonian salinity crisis' of the eastern Betics (Spain)

    NARCIS (Netherlands)

    Krijgsman, W.; Garcés, Miguel; Agustí, Jorge; Raffi, I.; Taberner, C.; Zachariasse, W.J.

    2000-01-01

    The late Miocene depositional history of the Lorca and Fortuna basins, both occupying an internal position in the eastern Betics of Spain, is marked by a regressive sequence from open marine marls, via diatomites and evaporites, to continental sediments. Based on facies similarities, these

  9. Paleogene evolution of the External Betic Zone and geodynamic implications

    OpenAIRE

    Guerrera, F.; Mancheño, M. A.; Martín-Martín, M.; Raffaelli, G.; Rodríguez-Estrella, T.; Serrano, F.

    2014-01-01

    Interdisciplinary studies combining field data (geological and tectonic mapping, lithostratigraphic reconstructions, lithofacies characterization, correlations and sampling) and laboratory analyses (biostratigraphy, chronostratigraphy, clay mineralogy and sandstone petrography) of eight Senonian-Paleogene successions from the Sierra de La Pila and Sierra de El Carche areas (Murcia province, SE Spain) belonging to the External Betic Zone are presented. Field evidence of tectonic activity (slum...

  10. Un modelo de la historia de la vegetación de la Cordillera de La Costa de Chile central-sur: la hipótesis glacial de Darwin A model for the history of vegetation of the Coastal Range of central-southern Chile: Darwin's glacial hypothesis

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    CAROLINA VILLAGRÁN

    2001-12-01

    Andean and at high latitudes exist in south-central Chile, between 37 and 43° S. According to Darwin (1859, such "islands" are remnants of glacial populations, which were distributed at lower altitudes and latitudes during glacier advances. Also, in Chile there were expansions of the Andean and southernmost flora into the Longitudinal Valley of Los Lagos region during the last glaciation, which reversed during the Late-glacial (14, 600-10,000 14C years BP and Holocene (after 10,000 14C years BP. Considering this hypothesis, in this study we analyzed two palynological sequences from summits of the Coastal Range of Los Lagos region (Cordillera de Nahuelbuta and Cordillera de Sarao and both were correlated with published high and low altitude records from the Los Lagos and Los Canales regions. The records from the Coastal Range show the following chronological sequence: (1 at the lower and middle Holocene, after 9,040 14C years BP, the Cordillera de Sarao site documents the colonization of Magellanic moorlands and north-Patagonian forest elements, followed by north-Patagonian-Valdivian forest elements during the upper Holocene; (2 the Cordillera de Nahuelbuta site shows the development of conifer forest and Magellanic moorlands during the middle Holocene, ca. 5,430 14C years BP. Other palynological records from the Coastal Range (Cordillera Pelada and Cordillera de Piuchué show the development of both communities during the Late-glacial and lower Holocene. In contrast, the low altitude pollen records from the Los Lagos region indicate that conifers and magellanic moorland elements occupied the Longitudinal Valley during the Last Glacial Maximum (LGM, ca. 22,000 14C years BP. Various pollen profiles from Los Lagos and Los Canales regions evidenced for the late-glacial (14,600-10,000 14C years BP the rapid southern expansion of conifers and other north-Patagonian elements, following the deglaciation of these areas. During the Holocene, Valdivian forest elements invaded the

  11. La estructura del área de Sierra Espuña (contacto zonas internas-externas, sector oriental de la Cordillera Bética

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    A., Martín-Algarra

    1997-12-01

    Full Text Available Sierra Espuña is located in the Eastern Betic Cordillera. The contact between the Malaguide Complex (Internal Betic Zone and the External Betic Zone cropouts in this area. Sierra Espuña area is a great antiformal stack that is followed by a great synforme (Mula-Pliego Depression. In the upper part of the Malaguide Complex, two nappes, with numerous internal folding and minor thrusting, are recognized: the Morron de Totana Nappe (at the bottom and the Perona Nappe (at the top. This structure is the result of a complex polyphasic tectonics in which two main structural events are recognized: the Intraoligocene tectonic phase, and the Lower Miocene tectonic phase.Sierra Espuña se sitúa en el sector oriental de la Cordillera Bética. En este sector afloran principalmente terrenos pertenecientes al Complejo Maláguide (Zonas Internas Béticas en contacto con las Zonas Externas Béticas. Esta región se configura como un gran antiforme de mantos al S (Sierra Espuña, seguido al N por un gran sinforme (Depresión de Mula-Pliego. En la parte alta del complejo, se reconocen dos unidades con el rango de manto de corrimiento, con numerosos repliegues y escamaciones internas: el Manto de Morrón de Totana, en posición inferior, y el Manto de Perona, en posición superior. Esta estructura es el resultado de una tectónica polifásica muy compleja en la que se reconocen dos grandes eventos estructurales: la fase tectónica Intraoligocena, y la fase tectónica del Mioceno Inferior.

  12. Using nanogranite and glassy inclusions to unravel anatexis in the crustal footwall of the Ronda peridotites (Betic Cordillera, S Spain)

    Science.gov (United States)

    Bartoli, Omar; Acosta-Vigil, Antonio; Cesare, Bernardo; Remusat, Laurent; Tajčmanová, Lucie; Wälle, Markus; Heinrich, Christoph; Poli, Stefano; Bodnar, Robert J.

    2015-04-01

    The application of melt inclusion (MI) studies to migmatites and granulites is a recent, small-scale approach to a better understanding of melting in the continental crust [1]. Being trapped by growing peritectic phases at suprasolidus conditions, these MI represent a window into the pre-peak anatectic history of partially melted terranes, and may provide a wealth of microstructural and compositional information on crustal anatexis [2, 3, 4]. The crustal footwall of the Ronda peridotites consists of an inverted metamorphic sequence with migmatites and mylonites at the top. Mylonites represent strongly deformed former diatexites. To shed light on the nature and mechanisms of melting in the migmatites of the Ojén traverse, a detailed microstructural and geochemical study has been conducted on primary 2-10 µm MI hosted in peritectic garnet of i) metatexites at the bottom of the migmatitic sequence and ii) mylonitic former diatexites close to the contact with the mantle rocks. Both metatexites and mylonites have compositions corresponding to peraluminous greywackes. Phase equilibria modeling shows P-T conditions of equilibration of 4.5-5 kbar and 660-700 °C, and of 820-830 °C and 5.5-6.0 kbar for metatexites and mylonites, respectively. Clusters of MI in the metatexites are rounded and preferentially located at the core of small garnet crystals, whereas these clusters may have a sigmoidal to spiral-like shape in garnets of mylonites. MI show a variable degree of crystallization ranging from totally glassy to fully crystallized (i.e., nanogranites), consisting of Qtz+Pl+Kfs+Bt+Ms aggregates (often modal Kfs > Pl in mylonites). Piston cylinder remelting experiments led to the complete rehomogenization of nanogranites in metatexites at the conditions inferred for anatexis: 700 °C and 5 kbar. Rehomogenized nanogranites in metatexites and glassy MI in mylonites are all leucogranitic, although generally plot away from minimum melt compositions. Systematic compositional variations have been observed between MI in metatexites and mylonites. MI in metatexites show higher amounts of H2O and Na2O/K2O ratios, lower FeO content, and higher concentrations of those trace elements controlled by feldspars: Sr, Ba. MI in mylonites have higher concentrations of trace elements controlled by Bt (Cs, Rb and FRTE e.g. Zn, Sc) and accessory minerals (HFSE e.g. Zr, U, Th, and LREE). The compositions of MI in metatexites and mylonites are interpreted to record the composition of the anatectic melts produced from a peraluminous greywacke 1) on, and immediately after crossing, the fluid-saturated solidus of this metasedimentary rock, and 2) during syn-kinematic anatexis via biotite dehydration melting at increasing temperature, respectively. [1] Cesare et al. (2009) Geology, 37, 627-630. [2] Bartoli et al. (2013) Geology, 41, 115-118. [3] Bartoli et al. (2014) EPSL, 395, 281-290. [4] Acosta-Vigil et al. (2010) JPetrol 51, 785-821.

  13. Paleogene tectono-sedimentary evolution of the Alicante Trough (External Betic Zone, SE Spain) and its bearing on the timing of the deformation of the South-Iberian Margin

    OpenAIRE

    Guerrera, Francesco; Estévez Rubio, Antonio; López Arcos, Mariano; Martín Martín, Manuel; Martín Pérez, Juan Antonio; Serrano Lozano, Francisco

    2006-01-01

    The Paleogene Alicante Trough of the South-Iberian Margin (External Betic Zone) consists of a narrow sedimentary basin that has active margins located to the north-northwest (active mainly during the Eocene) and to the south-southeast (active during the Oligocene). Both margins, consisting of shallow unstable platforms, were the source areas for the external-platform slope (in the opposite margins) and deepbasin (in the middle) depositional realms. The southern margin, lost under the Mediterr...

  14. Organic-rich shales from internal Betic basins (SE Spain): potential source rocks analogs for the pre-Messinian Salt play in the western Mediterranean

    Energy Technology Data Exchange (ETDEWEB)

    Permanyer, A.; Jorge, R.; Baudino, R.; Gilbert, L.

    2016-07-01

    Southeastern Spain has a large number of Late Neogene basins with substantial evaporitic deposits that developed under an overall NNW-SSE compressional regime related to the African-European tectonic plates collision. Located in the Betic Cordillera, they can be considered as marginal Mediterranean basins that became gradually isolated during the Tortonian and Early Messinian due to tectonic uplift. Different evaporitic units accumulated in these basins during isolation and, in several cases, evaporitic conditions were associated to episodes of important organic matter accumulation. Results obtained from Late Tortonian to Early Messinian shales collected from boreholes, mines and outcrops in the internal Betic basins of Las Minas de Hellín, Cenajo and Socovos are presented. The organic matter was studied under fluorescence and scanning electron microscopy (SEM), and the main geochemical characteristics defined. They show a relation between organic-rich intervals with high potential of hydrocarbon generation, native sulfur, bio-induced dolomite and evaporitic deposits. These organicrich shales can be found before, during and after the evaporitic episodes. Results from the present study are compared with those previously obtained in the pre-evaporitic deposits of the Lorca Basin that showed high oil generation potential, a restricted-marine origin of the organic matter and a low degree of maturity. The occurrence of such potential source rocks in several basins points to a broad regional distribution. At a larger scale, in the Mediterranean Basin, organic-rich sediments were deposited before and during the Messinian Salinity Crisis. The studied examples could represent analogs for potential source rocks of the pre-Messinian salt play in the Western Mediterranean. (Author)

  15. Glacier surface mass balance and freshwater runoff modeling for the entire Andes Cordillera

    Science.gov (United States)

    Mernild, Sebastian H.; Liston, Glen E.; Yde, Jacob C.

    2017-04-01

    Glacier surface mass balance (SMB) observations for the Andes Cordillera are limited and, therefore, estimates of the SMB contribution from South America to sea-level rise are highly uncertain. Here, we simulate meteorological, snow, glacier surface, and hydrological runoff conditions and trends for the Andes Cordillera (1979/80-2013/14), covering the tropical latitudes in the north down to the sub-polar latitudes in the far south, including the Northern Patagonia Ice Field (NPI) and Southern Patagonia Ice Field (SPI). SnowModel - a fully integrated energy balance, blowing-snow distribution, multi-layer snowpack, and runoff routing model - was used to simulate glacier SMBs for the Andes Cordillera. The Randolph Glacier Inventory and NASA Modern-Era Retrospective Analysis for Research and Applications products, downscaled in SnowModel, allowed us to conduct relatively high-resolution simulations. The simulated glacier SMBs were verified against independent directly-observed and satellite gravimetry and altimetry-derived SMB, indicating a good statistical agreement. For glaciers in the Andes Cordillera, the 35-year mean annual SMB was found to be -1.13 m water equivalent. For both NPI and SPI, the mean SMB was positive (where calving is the likely reason for explaining why geodetic estimates are negative). Further, the spatio-temporal freshwater river runoff patterns from individual basins, including their runoff magnitude and change, were simulated. For the Andes Cordillera rivers draining to the Pacific Ocean, 86% of the simulated runoff originated from rain, 12% from snowmelt, and 2% from ice melt, whereas, for example, for Chile, the water-source distribution was 69, 24, and 7%, respectively. Along the Andes Cordillera, the 35-year mean basin outlet-specific runoff (L s-1 km-2) showed a characteristic regional hourglass shape pattern with highest runoff in both Colombia and Ecuador and in Patagonia, and lowest runoff in the Atacama Desert area.

  16. Luminescence dating of Pleistocene alluvial sediments affected by the Alhama de Murcia fault (eastern Betics, Spain) – a comparison between OSL, IRSL and post-IRIRSL ages

    DEFF Research Database (Denmark)

    Sohbati, Reza; Murray, Andrew S.; Buylaert, Jan-Pieter

    2012-01-01

    The ages of nine alluvial units, identified by the integration of data obtained from five trenches at the southern termination of the Alhama de Murcia Fault (AMF) (eastern Betics, Spain), are constrained using luminescence dating based on the Optically Stimulated Luminescence (OSL) from quartz......, Infrared Stimulated Luminescence (IRSL) at 50°C, and post-IR elevated temperature (225°C) IRSL signals from K-feldspar. All signals pass the routine tests associated with the Single Aliquot Regenerative (SAR) protocol, including the recycling ratio, recuperation, and dose recovery tests. The equivalent...... of anomalous fading to a great extent, the resulting age cannot be regarded as necessarily accurate because of the limitations of the fading correction model used, and the absence of independent age control for the old samples. Nevertheless, our luminescence ages provide the first age constraints...

  17. Variations of the crustal thickness in the Betic-Rif domain and their foreland regions, by P-Receiver Functions

    Science.gov (United States)

    Stich, D.; Mancilla, F.; Morales, J.; Martin, R.; Diaz, J.; Pazos, A.; Cordoba, D.; Pulgar, J. A.; Ibarra, P.; Harnafi, M.; Gonzalez-Lodeiro, F.

    2012-12-01

    To image the crustal structure of the Betic-Rif Range and the surrounding area we perform a P-receiver function study (PRF). We calculate PRFs at 110 broadband stations located in South Iberia Peninsula and North Morocco to obtain thickness and average Vp/Vs ratio for the Crust. The Crustal thickness values show strong lateral variations throughout the region. Crustal thicknesses vary between ~19 km and ~46 km. The Betic and Rif ranges are underlined by a thickened crust with crustal thicknesses between ~35 km and ~46 km, reaching the highest values in the contact between the Alboran Domain and External Zones. Southeast Iberia and Northeast Morocco are affected by significant crustal thinning, with crustal thicknesses ranging from ~19 km to ~30 km, with the shallowest Moho along the Mediterranean coast. The transition from thick to thin crust is coincident with the faults system of the Trans-Alboran Shear Zone. Toward the North, the Iberian Massif is an homogeneous domain of average 30-31 km crustal thickness and flat Moho discontinuity with low average Vp/Vs ratios ~1.72. Further south an extended domain, which includes the Atlas domain and its foreland regions, presents crustal thickness of 27-34km. Vp/Vs ratios in north Morocco show normal values of ~1.75 for most stations except for the Atlas domain, where several stations present low Vp/Vs ratios around 1.71. The obtained PRFs are migrated to depth building cross-section images to delineate the crustal mantle discontinuity (Moho) along the study area. In the migrated images, we include altogether ~11.200 PFRs to follow the Moho discontinuity from the Iberian Massif, in the North, along the Gribraltar arc towards the Moroccan Massif in the South. These images show how, in the North, the Iberian crust underthrust the Alboran domain along their contact with the observation of a slab, from the western limit until the 3°W longitude, reaching the maximum depth of ~70 km under the coast coincide with the

  18. Uplift history of a Betic fold nappe inferred from Neogene-Quaternary sedimentation and tectonics (in the Sierra Alhamilla and Almeria, Sorbas and Tabernas Basins of the Betic Cordilleras, SE Spain)

    NARCIS (Netherlands)

    Weijermars, R.; Roep, Th.B.; Eeckhout, B. van den; Postma, G.; Kleverlaan, K.

    2007-01-01

    Structural, stratigraphical and sedimentological studies of the Alhamilla region show that the Sierra Alhamilla was elevated relative to the surrounding basins by open folding towards the end of the Tortonian period (about 7 Ma ago) and before the onset of Messinian sedimentation. The main arguments

  19. La formación radiolarítica Jarropa: definición y significado en el Jurásico Subbético (Cordillera Bética

    Directory of Open Access Journals (Sweden)

    Vera, J. A.

    1997-08-01

    Full Text Available The Jarropa Radiolarite Formation is defined formally, for the first time, according to the international guide of stratigraphic nomenclature, and the holostratotype and two parastratotypes are described. This is a very characteristic Jurassic unit of the Subbetic (Betic Cordillera in which point out the presence of radiolarite levels, together with siliceous marlstones, marls and clays. Two members are differentiated: a lower member of green, radiolarites and siliceous marls, and an upper member of red, siliceous clays and marls, both being recognizable in most of the outcrops. The age of this formation in the holostratotype, known mainly from the study of their radiolarians, is Late Callovian-Oxfordian. In other stratigraphic sections (including some parastratotype is verified that the exact age of the bottom of the formation, and of the boundary between the two before described members are heterochronous, within the Uppermost Bajocian-Lowermost Kimmeridgian. They are pelagic sediments, deposited during the expansive phase of the Southern Iberian Continental Paleomargin, in areas far from the continent with thin continental crust. They have a great analogy with deposits outcropping in others Mediterranean Alpine domains (Apennines, Alps, Dinarids, etc. also accumulated during Jurassic extensive phases of continental margins adjacent to the Tethys. The depositional bathymetry is estimated in a few hundreds of meters, without a necessary relation with the calcite compensation depth (CCD.Se define formalmente, por primera vez, la «Formación Radiolarítica Jarropa» de acuerdo con las normas internacionales de nomenclatura estratigráfica, y se describen el holoestratotipo y dos paraestratotipos. Se trata de una unidad litoestratigráfica muy característica del Jurásico del Subbético (Cordillera Bética en la que destacan la presencia de niveles de radiolaritas, junto con margas y arcillas silíceas. Se diferencian dos miembros, uno

  20. GPS Crustal deformation in the Eastern Betics and the Lorca earthquake of 2011

    Science.gov (United States)

    Khazaradze, Giorgi; Echeverria, Anna; Asensio, Eva; Gárate, Jorge; Suriñach, Emma

    2013-04-01

    We present an updated crustal deformation field in the Eastern Betics, based on GPS observations of the CuaTeNeo network. This non-permanent network was established in 1996 to quantify the current tectonic deformation of the SE Betics. The network consists of 15 stable monuments distributed between Murcia and Almeria, which were observed five times (1997, 2002, 2006, 2009 and 2011). In general, the results show a velocity field lower than 2 mm/yr with a dominant trend oriented parallel to the Eurasia and Nubia relative plate convergence. Stations located farther inland exhibit lower velocity vectors. The calculated crustal deformation field presents clear evidence that the tectonic faults forming the Eastern Betic Shear Zone remain active. As it was evidenced by the May 11th 2011 Lorca earthquake of magnitude Mw5.2, which was caused by a reverse and sinistral slip of the Alhama de Murcia Fault. Our GPS observations, preceding the occurrence of the earthquake, are in agreement with this type of focal mechanism. Co-seismic deformation related to the earthquake was relatively small: offset of ~5mm to the North was detected at the continuous GPS station LORC located within the city.

  1. Along-strike variations of the External Betics basal detachment: Implications on the evolution of a curved FTB

    Science.gov (United States)

    Jiménez-Bonilla, Alejandro; Torvela, Taija; Balanyá, Juan Carlos; Expósito, Inmaculada; Díaz-Azpiroz, Manuel

    2017-04-01

    Analogue models have successfully tested the role of different parameters on the orogenic curvature. Among them: (1) along-strike variations of the frictional properties of the detachment layer, (2) the topography of the basement, (3) the syn-tectonic sedimentation and/or erosion and (4) the indenter shape. Previous works have pointed out that, across-strike the central Betic fold-and-thrust belt (FTB), northern branch of the Gibraltar Arc, a change on the structural style and on the topographic envelope (α) coincide with the pinch-out of Triassic evaporites and with a change in the basement dip (β) that induced changes on the wedge geometry and the basal friction (Jiménez-Bonilla et al., 2016). In this work, we tried to constrain the external orogenic wedge geometry to study the evolution of the western Betics FTB and, comparing it with the central Betics FTB, to delve into the structural variations along-strike the Betic chain. In the present work, field data together with reflection seismic interpretations permit us to constrain the across-strike variations on the structural style of the western Betics FTB. The internal FTB is deformed by SW-NE, kilometric-scale, and non-cylindrical folds detached within Triassic evaporites. The middle FTB is characterized by the profusion of allochtonous Triassic mudstones and evaporites and it is deformed into a dextral transpressive band. In the frontal FTB, a Middle Miocene package, the Olistostromic Unit, is deformed by foreland-verging thrusts overlying paleomargin-derived units. Accordingly, these differences on the structural style across the western Betics FTB could be attributable to the variations on the frictional properties of the detachment level. Regarding the wedge geometry, the topographic relief envelope (α) of the western Betics FTB is similar to that one of the central Betics. However, β is significantly lower than in the central Betics (ca. 2° vs >4°). Moreover, neither Triassic pinch-out nor basement

  2. Relación de las direcciones de karstificación y del termalismo con la fracturación en las Cordilleras Béticas.

    Directory of Open Access Journals (Sweden)

    Benavente Herrero, J.

    1985-08-01

    Full Text Available Based on the interpretation of aerial photographs (scales between 1:10,000 and 1:35,000 an analysis is made of the various karstic fracture systems within the Betic Cordilleras of Southern Spain. The age of the fractured materials is comprised between the Middle Triassic to the Pliocene, with lithologies that. though predominantly carbonatic, also include celestite, and gypsum-bearing evaporites, Besides their directional frequency, the methodologies employed also allowed an estimate of the length relationships among fracture systems.
    The resulta so obtained, tested against field observations, indicate that two fracture systems (N 130-160 E and N 5-35 E are predominant, characterized respective1y by a relatively greater length of its componental fractures and by having a bimodal directional frequency, On a regional scale both systems correlate well with important structural lineaments that appear to have been active either as strike-slip or normal faults. Another fracture system striking roughly N 70-100 E presents comparatively less evidence of karstification, in spite of its considerable tectonic and paleogeographic significance (i. e., it parallels the boundary between internal ad external realms of the cordilleras, the socalled Cádiz-Alicante fracture system, The intersection of these systems (especially those striking N 70-100 E and N 130160 E appears to be a major control of the location of the main thermal springs , as well as of the intense seismic activity of the area.
    From a methodological standpoint. the results obtained in this study cover a scale level about which no information was previously available, and confirm existing hypotheses -based on satellite imaginery and microtectonic analysis-s- concerning the occurrence of changes in the orientation of the maximum vector of compressive stress. The strike of the karstification lineaments here signaled coincide with those obtained in analogous studies in the portuguese

  3. Late Palaeozoic to Triassic formations unconformably deposited over the Ronda peridotites (Betic Cordilleras: Evidence for their Variscan time of crustal emplacement

    Directory of Open Access Journals (Sweden)

    Sanz de Galdeano, C.

    2016-06-01

    Full Text Available The age of the emplacement of the Ronda Peridotites has been widely debated during recent decades, and ages ranging from the Palaeozoic to the early Miocene have been proposed, although most of the current interpretations suggest an Oligocene-Miocene age. In this article, we describe two meta-sedimentary formations (the lower one formed by detrital sediments and the upper one by marbles that were unconformably deposited over the Ronda peridotites and now record low-grade metamorphism. The detrital formation contains layers of acidic rocks with an age of 269±9 Ma and the overlying marbles are assumed to be Triassic. The existence of these unconformable formations over the peridotites is crucial for the dating of the exhumation of the latter. The presence of peridotite clasts in the detrital formation indicates that peridotites were exposed during the Permian and other data suggest that peridotites were exhumed during the late Carboniferous. During the Alpine cycle, the peridotites operated as an element situated at the bottom of the tectonically higher Alpujarride/Sebtide unit (the Jubrique unit and forming part of it, then being incorporated to the Alpine thrusts of this unit.La edad del emplazamiento de las peridotitas de Ronda ha sido discutida ampliamente en las últimas décadas, con hipótesis que van desde el Paleozoico al Mioceno inferior, aunque la mayoría de las interpretaciones actuales sugiere una edad oligo-miocena. En este artículo, describimos la existencia de dos formaciones meta-sedimentarias (la inferior formada originalmente por sedimentos detríticos y la superior por carbonatos que se depositaron en discordancia sobre las peridotitas de Ronda y ahora registran un grado bajo de metamorfismo. La formación detrítica contiene capas de rocas ácidas con una edad de 269±9 Ma y los mármoles situados encima se atribuyen al Trías. La existencia de esas dos formaciones es crucial para la datación de la exhumación de las peridotitas. La presencia de clastos de peridotitas en la formación detrítica indica que aquellas estuvieron expuestas durante el Pérmico, otros datos sugieren que las peridotitas fueron exhumadas durante el Carbonífero superior. Durante el ciclo alpino, las peridotitas actuaron como un elemento ya antes situado en la base de la unidad Alpujárride/ Sébtide superior (unidad de Jubrique, formando parte de ésta.

  4. Late Pleistocene glacial fluctuations in Cordillera Oriental, subtropical Andes

    Science.gov (United States)

    Martini, Mateo A.; Kaplan, Michael R.; Strelin, Jorge A.; Astini, Ricardo A.; Schaefer, Joerg M.; Caffee, Marc W.; Schwartz, Roseanne

    2017-09-01

    The behavior of subtropical glaciers during Middle to Late Pleistocene global glacial maxima and abrupt climate change events, specifically in Earth's most arid low-latitude regions, remains an outstanding problem in paleoclimatology. The present-day climate of Cordillera Oriental, in arid northwestern Argentina, is influenced by shifts in subtropical climate systems, including the South American Summer Monsoon. To understand better past glacier-subtropical climates during the global Last Glacial Maximum (LGM, 26.5-19 ka) and other time periods, we combined geomorphic features with forty-two precise 10Be ages on moraine boulders and reconstructed paleo-equilibrium line altitudes (ELA) at Nevado de Chañi (24°S) in the arid subtropical Andes. We found a major glacial expansion at ∼23 ± 1.6 ka, that is, during the global LGM. Additional glacial expansions are observed before the global LGM (at ∼52-39 ka), and after, at 15 ± 0.5 and 12 ± 0.6 ka. The ∼15 ka glacial event was found on both sides of Chañi and the ∼12 ka event is only recorded on the east side. Reconstructed ELAs of the former glaciers exhibit a rise from east to west that resembles the present subtropical climate trajectory from the Atlantic side of the continent; hence, we infer that this climate pattern must have been present in the past. Based on comparison with other low-latitude paleoclimate records, such as those from lakes and caves, we infer that both temperature and precipitation influenced past glacial occurrence in this sector of the arid Andes. Our findings also imply that abrupt deglacial climate events associated with the North Atlantic, specifically curtailed meridional overturning circulation and regional cooling, may have had attendant impacts on low subtropical Southern Hemisphere latitudes, including the climate systems that affect glacial activity around Nevado de Chañi.

  5. Unidades tectónicas y estructura general de la Sierra de Gádor y zonas adyacentes (Cordillera Bética, provincia de Almería: implicaciones paleogeográficas

    Directory of Open Access Journals (Sweden)

    Delgado Salazar, F.

    2007-06-01

    Full Text Available In the Sierra de Gádor (Almeria province terrains belonging to the Internal Betic Zone crop out. According to stratigraphic, structural and petrologic features we have recognised five tectonic units. These units are called, from bottom to top, Gádor-Turón, Laujar, Murtas, Felix and Chirán unit. The lower fourth are ascribed to the Alpujárride Complex, whilst the last one is ascribed to the Maláguide Complex. We also discuss if the Felix unit may be included in the Intermediate Units. The Felix unit represents the Triassic palaeogeographic transition between the Alpujárride and the Maláguide, and it was located between both complexes during the alpine tectono-metamorphic evolution of the Betic Cordillera.En la Sierra de Gádor (provincia del Almería afloran rocas pertenecientes a la Zona Interna de la Cordillera Bética. En este sector hemos reconocido un total de cinco unidades tectónicas, en función de sus características estratigráficas, estructurales y petrológicas. Estas unidades se denominan, de abajo a arriba, unidad de Gádor-Turón, unidad de Laujar, unidad de Murtas, unidad de Felix y unidad de Chirán. Las cuatro más bajas las asignamos al Complejo Alpujárride, mientras que la más alta la asignamos al Complejo Maláguide. Se discute además la posible inclusión de la unidad de Felix dentro de las denominadas Unidades Intermedias. La unidad de Felix representa el tránsito paleogeográfico durante el Triásico entre el dominio Alpujárride y el Maláguide, y estaría situada entre ambos complejos durante la evolución tectono-metamórfica alpina de la Cordillera Bética.

  6. Holocene glacier fluctuations in the American Cordillera

    Science.gov (United States)

    Davis, P. Thompson

    In many areas of the American Rocky Mountains (Colorado, Wyoming, Utah, Idaho, Montana), Cascade Range (Washington, Oregon), and the Sierra Nevada (California), radiocarbon ages suggest that ice receded to near present limits before 10 ka BP. A pre-Altithermal readvance or stillstand left moraines ca. 1-3 km beyond and ca. 50-300 m below present glacier margins. At one locality on Glacier Peak in Washington, these deposits are perhaps dated to the early Holocene, but in general these deposits are probably at least 10 ka old. Glacial advances during the Altithermal (ca. 8 to 5 ka BP) elsewhere are rare; radiocarbon evidence for Altithermal glacial advances in the Colorado Front Range is questionable. The earliest radiocarbon-dated Neoglacial advances occurred about 5 ka BP in the Washington Cascades; moraines and related deposits believed to be of early Neoglacial age (i.e. 5 to 3 ka BP) elsewhere are poorly dated. For example, moraines believed to date to the early Neoglacial in Colorado (Triple Lakes) and Wyoming (Temple Lake) are actually late Pleistocene age, based on radiocarbon ages derived from lake sediments at the type localities. Although relative-age data (i.e. lichens, rock weathering, soils) from many areas suggest a three-fold Neoglacial sequence, little supporting radiocarbon evidence is available. However, tephrochronology distinguishes three Neoglacial advances near Mount Rainier in Washington. In most mountain ranges of the western United States, fresh, unweathered, sharp-crested moraines usually adjacent to present ice margins, or near headwalls in empty cirques, date to the Little Ice Age of the last several centuries. However, detailed photographic or other historical records of glacial fluctuations during the last century are rare, and detailed mass balance studies rarer still. Whether or not pre-Little Ice Age glacial fluctuations in the American Cordillera are synchronous must await better radiometric dating of local moraine sequences.

  7. Landsat TM and ETM+ derived snowline altitudes in the Cordillera Huayhuash and Cordillera Raura, Peru, 1986–2005

    Directory of Open Access Journals (Sweden)

    J. Ramage

    2011-05-01

    Full Text Available The Cordilleras Huayhuash and Raura are remote glacierized ranges in the Andes Mountains of Peru. A robust assessment of modern glacier change is important for understanding how regional change affects Andean communities, and for placing paleo-glaciers in a context relative to modern glaciation and climate. Snowline altitudes (SLAs derived from satellite imagery are used as a proxy for modern (1986–2005 local climate change in a key transition zone in the Andes. Clear sky, dry season Landsat Thematic Mapper (TM and Enhanced Thematic Mapper (ETM+ satellite images from 1986–2005 were used to identify snowline positions, and their altitude ranges were extracted from an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER digital elevation model (DEM. Based on satellite records from 31 glaciers, average snowline altitudes (SLAs, an approximation for the equilibrium line altitude (ELA, for the Cordillera Huayhuash (13 glaciers and Cordillera Raura (18 glaciers from 1986–2005 were 5051 m a.s.l. from 1986–2005 and 5006 m a.s.l. from 1986–2002, respectively. During the same time period, the Cordillera Huayhuash SLA experienced no significant change while the Cordillera Raura SLA rose significantly from 4947 m a.s.l. to 5044 m a.s.l.

  8. Late Miocene extension partitioning in the eastern Betics: from W- to E-directed extension between the Sorbas and Vera basins (SE Spain).

    Science.gov (United States)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, Jose Miguel; Azañon, Jose Miguel

    2014-05-01

    Late Miocene westward-directed extension in the Betics produced elongated core-complexes like Sierra Nevada and the Sierra de Filabres, tilted-block domains and associated basins. This extension represents the superficial manifestation of the rupture of the Tethyan slab and associated edge delamination along a lithospheric transform fault beneath the northern branch of the Gibraltar Arc orogenic system. However, crustal thinning at the eastern Betics occurs progressively towards the east suggesting an eastward-directed extension, probably related to the late Miocene opening of the Algero-Balearic basin. In order to define the kinematics and timing of such a heterogeneous extension at the eastern Betics we have carefully mapped a key area at the transition between the Sorbas and Vera basins. Field data indicate that extension in the area started at the southern margin of the Vera basin during the Serravallian (13.8 Ma) and continued until the Tortonian (approximately 8 Ma). This extension was characterized by a set of NE- to E-directed normal faults to the east, in the Vera basin, and a set of SW-directed normal faults to the west, towards the Sorbas basin. This opposite-directed extension is segmented by E-W to WNW-ESE strike-slip faults like the North Cabrera dextral transfer fault that accommodates NE- to E-directed extension to the north and SW-directed extension to the south. This structure resulted in westward tilted blocks that lead to Serravallian-Tortonian depocenters deepening towards the east at the Vera basin along the northern side of Sierra Cabrera. Meanwhile, at the western termination of Sierra Cabrera, westward-directed extension migrated SW-ward forming the Sorbas basin during the Tortonian (approximately 9-7.24 Ma). This extension was characterized by a listric fan of SW-directed normal faults highly segmented by E-W to NE-SW transfer. This extensional system produced tiled-blocks defining a Tortonian depocenter at the eastern margin of the Sorbas

  9. An enigmatic frog of the genus Atelopus (Family Bufonidae) from Parque Nacional Chirripó, Cordillera de Talamanca, Costa Rica.

    Science.gov (United States)

    Savage, Jay M; Bolaños, Federico

    2009-01-01

    A distinctive new species of Atelopus is described from Parque Nacional Chirrip6 Grande, Cordillera de Talamanca (3,400-3,500 m). It closely resembles populations of the Atelopus ignescens complex from the Andes of northern Ecuador and southern Colombia. It differs most significantly from these frogs in the pattern of spiculae and coni development on the throat, chest, hands and feet. The Costa Rican species appears to be an outlier of the complex inexplicably separated geographically from its nearest allies by an over land distance of about 1,600 km.

  10. Mountain front migration and drainage captures related to fault segment linkage and growth: The Polopos transpressive fault zone (southeastern Betics, SE Spain)

    Science.gov (United States)

    Giaconia, Flavio; Booth-Rea, Guillermo; Martínez-Martínez, José Miguel; Azañón, José Miguel; Pérez-Romero, Joaquín; Villegas, Irene

    2013-01-01

    The Polopos E-W- to ESE-WNW-oriented dextral-reverse fault zone is formed by the North Alhamilla reverse fault and the North and South Gafarillos dextral faults. It is a conjugate fault system of the sinistral NNE-SSW Palomares fault zone, active from the late most Tortonian (≈7 Ma) up to the late Pleistocene (≥70 ky) in the southeastern Betics. The helicoidal geometry of the fault zone permits to shift SE-directed movement along the South Cabrera reverse fault to NW-directed shortening along the North Alhamilla reverse fault via vertical Gafarillos fault segments, in between. Since the Messinian, fault activity migrated southwards forming the South Gafarillos fault and displacing the active fault-related mountain-front from the north to the south of Sierra de Polopos; whilst recent activity of the North Alhamilla reverse fault migrated westwards. The Polopos fault zone determined the differential uplift between the Sierra Alhamilla and the Tabernas-Sorbas basin promoting the middle Pleistocene capture that occurred in the southern margin of the Sorbas basin. Continued tectonic uplift of the Sierra Alhamilla-Polopos and Cabrera anticlinoria and local subsidence associated to the Palomares fault zone in the Vera basin promoted the headward erosion of the Aguas river drainage that captured the Sorbas basin during the late Pleistocene.

  11. Extension in a convergent tectonic setting: a lithospheic view on the Alboran system of SW Europe

    NARCIS (Netherlands)

    Vissers, R.L.M.

    2012-01-01

    The Betic Cordillera of southern Spain forms a clear example of a collisional orogen that has undergone large-scale late-orogenic extension while convergent motion of the bounding plates continued. The orogen provides a unique opportunity to study the tectonics of the system at different lithospheri

  12. Estudio sedimentológico del Keuper inferior, a partir del análisis de facies, en el sector central de la Cordillera Bética. Algunas consideraciones paleogeográficas

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    López Chicano, M.

    1989-12-01

    Full Text Available The lower Keuper of the central sector of Betic Cordillera shows a predominance of clays with variegated colours. They have intercalations of thin layers of sandstones (fine grain, gypsum and carbonates. Through sedimentological and stratigraphic analysis we can conclude that these materials are from a systems tract fluviocoastal further more it allows us to distinguish sorne different facies types which characterize the following subenvironments. They are set in a framework of mud flat, found on a vast tidal coastal lutitic plain. Terrigenous sediments (fine sands from the mainland are deposited on the lutitic plain by ephemeral streams. In this coastal environment there are subenvironments of salt marsh, salt pans, sabkha, coastal lagoons, etc. The distribution in time and space of these facies was mainly controlled by the climate and the frequent incursions of the sea over the coastal plain, facilited by the flat geographical nature of coastline.En el Keuper inferior del sector central de la Cordillera Bética hay un predominio de materiales arcillosos, de colores abigarrados, con niveles intercalados de areniscas de grano fino, yesos y carbonatos. A partir del análisis estratigráfico y sedimentológico se han interpretado estos materiales como pertenecientes a un cortejo fluviocostero. Este análisis ha permitido, previamente, diferenciar diversas asociaciones de facies que caracterizan varios ambientes sedimentarios. Esencialmente, se enmarcan en un mud flat, dentro de una extensa llanura costera parcialmente afectada por mareas. A ésta llegan sedimentos detríticos continentales (arenas finas mediante corrientes fluviales efímeras. Dentro de este mismo medio costero aparecen ambientes de marisma, salt pans, sabkha, laguna, etc. La evolución en el tiempo y en el espacio de estas facies está controlada principalmente por el clima y por las frecuentes ingresiones del mar sobre la llanura costera, las cuales están facilitadas por la

  13. Algunos aspectos de la estructura de la Zona Subbética (Cordilleras Béticas. España meridional

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    Hermes, Jacobus J.

    1985-08-01

    Full Text Available Analysis of sedimentation and tectonics of the Subbetic zone of the Betic Cordilleras leads to the conclusion that sedimentation and subsequent deformation are largely governed by a Wilson cycle (Wilson, 1966, 1968 that began the opening of the Tethyan rift in the Pangaea continent during the Pliensbachian, 180 Ma ago. The resulting ocean began to close again in the Cretaceous, a process that led to a collision between Iberia and African elements in the Burdigalian, which was followed by strike-slip movement along a shear zone between the two plates which continues to this day. It is argued that the collision led to general uplift of the Subbetic zone as shown by the termination of deep water pelagic and hemipelagic sedimentation in the entire zone, and that the subsequent strike-slip movements along a system of anastomosing faults loo to very intense deformation localized along separate fault zones, and to the opening of pull-apart basins with characteristic sedimentation sequences.

    El análisis de la sedimentación y la tectónica de la Zona Subbética (Cordilleras Béticas conduce a la conclusión de que la sedimentación y la deformación posterior han sido ampliamente determinadas por un ciclo de Wilson (Wilson, 1966, 1968; Mitchell y Reading, 1978 que comenzó con la apertura del Tethys en el continente de Pangaea durante el Pliensbaquiense, hace 180 ID. a. El océano resultante empezó a cerrarse de nuevo en el Cretácico. Este proceso condujo a la colisión entre Iberia y elementos africanos en el Burdigaliense y fue seguido por un movimiento de salto en dirección a favor de una zona de cizalla que aún continúa en la actualidad. La colisión provocó el levantamiento general del la Zona Subbética, como lo demuestra el cese de la sedimentación pelágica y hemipelágica profundas por toda ella. Los movimientos subsiguientes de salto en 'dirección a favor de un sistema de fallas anastomosadas produjeron una deformación muy

  14. Extensional Detachment faulting in melange rocks. Plurikilometres migration by W the External Zone (Cordillera Bética, Spain)

    Science.gov (United States)

    Roldán, Francisco Javier; Azañon, Jose Miguel; Rodríguez, Jose; Mateos, Rosa Maria

    2014-05-01

    The synthesis and correlation of units carried out in the continuous geological map (Roldán et al., 2012), has revealed a fragmentation of the carbonate outcrops belong to the Subbetic Domain (García-Hernández et al., 1980). Subbetic NW verging thrust and fold axial traces have not lateral continuity and Jurassic carbonate outscrops appear as klippes on the olistotromic unit. These ductile structures that can be observed in the internal structure of these jurassic blocks are unrelated to the brittle-ductile deformation bands observed at the basal pelitic levels. Basal detachments are rooted in: a) the Olistostromic unit, a Upper Langhian-Lower Serravallian breccia constituted by gypsum-bearing clay and marls; b) Cretaceous-Tertiary marly sedimentary rocks (Rodríguez-Fernández, et al., 2013) . In both kind of rocks, cataclastic structures allows to infer a top-to-the WSW displacement. Paleostress measurements, made on these detachments levels, are compatible with a extensional regime (Roldán et al., 2012). At the same time, the analysis and interpretation of subsurface data (seismic surveys and borehole testing) shows that the Subbetic Domain (External Subbetic, Molina 1987) are affected by westward low-angle normal faults. A balanced cross-section, based on morphological and cartographic data in the area between Sierra de Cabra and Sierra de Alta Coloma (Valdepeñas de Jaén), shows plurikilometric displacements which has been produced during Late Serravallian-Early Tortonian times. References: García-Hernández, M., López-Garrido, A.C., Rivas, P., Sanz de Galdeano, C., Vera, J.A. (1980): Mesozoic paleogeographic evolution of the zones of the Betic Cordillera. Geol. Mijnb. 59 (2). 155-168. Molina, J.M. (1987). Análisis de facies del Mesozoico en el Subbético. Tesis Doctoral, Univ. Granada. 518 p. Rodríguez-Fernández, J., Roldán, F. J., Azañón, J.M. y García-Cortés, A. (2013). El colapso gravitacional del frente orogénico a lpino en el Dominio Subb

  15. A new species of salamander (Bolitoglossa: Plethodontidae from the Cordillera Oriental of the Colombian Andes

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    Andrés R. Acosta-Galvis

    2012-01-01

    Full Text Available Eight species of salamanders are recognized to Cordillera Oriental of Colombia. Here we describe a new species of the genus Bolitoglossa, named Bolitoglossa guaneae sp. nov. The highest number of species of this genus is found in the cloud forests located in the western flank of the Cordillera Oriental.

  16. Climatic forcing of asymmetric orogenic evolution in the Eastern Cordillera of Colombia

    NARCIS (Netherlands)

    Mora, A.; Parra, M.; Strecker, M.R.; Sobel, R.A.; Hooghiemstra, H.; Torres, V.; Vallejo Jaramillo, J.

    2008-01-01

    New apatite fission-track data, paleoelevation estimates from paleobotany, and recently acquired geological data from the Eastern Cordillera of Colombia document the onset of increased exhumation rates in the northeastern Andes at ca. 3 Ma. The Eastern Cordillera forms an efficient orographic barrie

  17. Geochemistry and age relationships of metamorphosed mafic sills from Sierra de Enmedio and Sierra de Carrascoy (Eastern Betic zone, Southeastern Spain

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    Torres-Roldán, R. L.

    1989-12-01

    Full Text Available The presence of fairly abundant shallow-intrusive mafic bodies is a common feature of the almagride units, a recently defined group of tectonic elements of the Eastern Betic Zone whose paleogeographic and tectonic interpretation is particuIarly controversial. In this paper we focuse on the bulk geochemistry (including K/Ar data and possible age relationships of tbese rocks, and discuss them in view of their significance regarding possible tectonic framework of emplacement and subsequent crustal evolution. The analyses (49-55% SiO2 point to a derivation from tholeiitic magmas that interacted with continental crust, as indicated by enrichment in the less compatible elements, such as Ba, Rb, Th and K, whose amounts are similar to those of well known continental tholeiitic provinces. Thus, the magmatic event is inferred to have been generated in a tectonic environment comparable to that of continental rifts. Emplacement may have taken place in Upper Triassic to Middle Jurassic times, as bracketed by their intrusion within Triassic beds and one whole-rock KIAr date of 178±4 Ma from a less altered sample. Much younger analytical K/Ar ages, scattering between 41±5 and 57±2 Ma, are obtained from common samples, however, reflecting an Eocene or younger metamorphic event that caused partial recrystallisation under low-grade greenchist, to actinolite-pumpelIyite facies conditions. As compared to other mafic complexes in the Betics, the observed chemical evidence for crustal contamination makes the almagride metabasites more similar to those in the external zona (e.g. the so-calIed «opbites» than in tbe Nevado-Filábride Ensemble, thus being consistent with proposals that correlate these units with the Subbetic in the Murcia area.La frecuente presencia de cuerpos de metabasitas es una característica común de las unidades almágrides, un grupo de unidades tectónicas de la Zona Bética Oriental, de reciente definición, cuya interpretaci

  18. Serological survey of leptospiral infections in sheep, goats and dogs in Cordillera province, Bolivta.

    Science.gov (United States)

    Ciceroni, L; Bartoloni, A; Pinto, A; Guglielmetti, P; Valdez Vasquez, C; Gamboa Barahona, H; Roselli, M; Giannico, F; Paradisi, F

    1997-01-01

    A serological survey for antibodies to Leptospira spp. was conducted on sheep, goat and dog serum samples collected in three localities in Cordillera province in the southern part of the Santa Cruz Department (Bolivia) in 1992. A total of 98 sheep, 218 goats and 43 dogs were tested against 29 leptospiral serovars using the microscopic agglutination test. At the time of blood collection all of the examined animals appeared healthy and presented no clinical sign suggestive of leptospirosis. Antibody prevalences, as determined by positive results at a 1:100 dilution or higher, was 14.3% in sheep, 19.7% in goats, and 14.0% in dogs. Agglutinins against six serovars (poi. shermani, pomona, canicola, javanica, djasiman) were found in positive animals. The highest serological prevalence in sheep and goats was recorded for serovar poi, followed by pomona in sheep and shermani in goats. Titres to shermani were the commonest in dogs. The results of this survey indicate that leptospiral infection is common in south-east Bolivia and that serovars of several serogroups concur in the etiology.

  19. Downscaling reanalysis data to high-resolution variables above a glacier surface (Cordillera Blanca, Peru)

    Science.gov (United States)

    Hofer, Marlis; Mölg, Thomas; Marzeion, Ben; Kaser, Georg

    2010-05-01

    Recently initiated observation networks in the Cordillera Blanca provide temporally high-resolution, yet short-term atmospheric data. The aim of this study is to extend the existing time series into the past. We present an empirical-statistical downscaling (ESD) model that links 6-hourly NCEP/NCAR reanalysis data to the local target variables, measured at the tropical glacier Artesonraju (Northern Cordillera Blanca). The approach is particular in the context of ESD for two reasons. First, the observational time series for model calibration are short (only about two years). Second, unlike most ESD studies in climate research, we focus on variables at a high temporal resolution (i.e., six-hourly values). Our target variables are two important drivers in the surface energy balance of tropical glaciers; air temperature and specific humidity. The selection of predictor fields from the reanalysis data is based on regression analyses and climatologic considerations. The ESD modelling procedure includes combined empirical orthogonal function and multiple regression analyses. Principal component screening is based on cross-validation using the Akaike Information Criterion as model selection criterion. Double cross-validation is applied for model evaluation. Potential autocorrelation in the time series is considered by defining the block length in the resampling procedure. Apart from the selection of predictor fields, the modelling procedure is automated and does not include subjective choices. We assess the ESD model sensitivity to the predictor choice by using both single- and mixed-field predictors of the variables air temperature (1000 hPa), specific humidity (1000 hPa), and zonal wind speed (500 hPa). The chosen downscaling domain ranges from 80 to 50 degrees west and from 0 to 20 degrees south. Statistical transfer functions are derived individually for different months and times of day (month/hour-models). The forecast skill of the month/hour-models largely depends on

  20. Holocene denudation and landscape deformation in the Cordillera Blanca, Peru

    Science.gov (United States)

    Hodson, K. R.; Hall, S. R.; Michalak, M.; Farber, D.; Hourigan, J. K.

    2012-12-01

    Active orogenic systems are subject to a host of processes that influence their topographic and structural evolution. Broadly speaking, these processes can be divided into two general groups: tectonics and climate. Both are capable of inducing profound changes within an orogen, although many specifics regarding their forcings, interactions, and feedbacks remain unclear. Here, we address the evolution of the Cordillera Blanca Mountain Range of northern Peru: an elevated, high-relief, 200km long string of glaciated peaks along the spine of the Andes. The striking Cordillera Blanca Detachment Fault (CBDF) is actively facilitating the production of several kilometers of relief along the western flank of the range, and abundant records of past glaciations span from >440 ka to the present. Thus, tectonics (active faulting) and climate (glacial erosion) are operating in tandem to produce some of the highest topography in the western hemisphere, affording the opportunity to investigate their potential interactions. Through the use of cosmogenic 10Be, low temperature thermochronology and digital terrain analysis we characterize the rates of landscape change as well as the present morphology. Significant variation in range elevation (maximum, mean, modal and minimum), relief (local and within basins) and slope (maximum, mean and minimum) exist along the strike of the range, potentially reflecting variable displacement along the CBDF, varying degrees of glacial erosion along the mountain range, or some combination of the two. The morphology of the adjacent supradetachment basin varies as well, containing zones with distinct styles of faulting and basin growth likely defined by the segmentation history of the CBDF. New thermochronologic data extends the current dataset, which we combine with 10Be basin-averaged erosion rates from basins along the range. These two datasets constrain the exhumational and erosional history of the range-forming Cordillera Blanca Batholith from the

  1. Nazca plate subduction, mantle flow and Cordilleras formation

    Science.gov (United States)

    Capitanio, Fabio A.

    2013-04-01

    The Nazca-South America convergence represents a unique natural laboratory to probe our understanding of subduction, mantle flow and stress coupling at Andean-type margins. Here, it is shown that the most fundamental balance of forces associated with the downgoing slab, the upper plates and the mantle can account for the Nazca plate motions, although it does not adequately explain the variations of the Cordilleran tectonics found along the ~6000 km wide margin. Using three-dimensional numerical models it is shown that trench-parallel gradients in both the driving and resisting forces are an essential component of the force balance, and necessary to reproduce the macroscopic features observed. When along-trench buoyancy variations similar to the Nazca plate's are included, the slab dips and upper plate deformations observed in the Nazca slab, in the Cordilleras and South American continent interiors can be reproduced. The models show that gradients in the resisting shear force along the trench can be as relevant, as they modulate the trench retreat to form the concave Bolivian Orocline. Pressure gradients in the mantle follow the Nazca buoyancy gradients, and effectively rearrange the flow introducing a trench-parallel component, similar to what suggested by seismic anisotropy in this area. Although they introduce only secondary variations to the primary subduction and mantle flow dynamics, the regional features of the Nazca and South American plates exert a primary control at the margin-local scale. This suggests that far-field forces, e.g. from spreading Atlantic or large-scale convection, should play a minor role in the formation of the Cordilleras.

  2. Recent glacier retreat and climate trends in Cordillera Huaytapallana, Peru

    Science.gov (United States)

    López-Moreno, J. I.; Fontaneda, S.; Bazo, J.; Revuelto, J.; Azorin-Molina, C.; Valero-Garcés, B.; Morán-Tejeda, E.; Vicente-Serrano, S. M.; Zubieta, R.; Alejo-Cochachín, J.

    2014-01-01

    We analyzed 19 annual Landsat Thematic Mapper images from 1984 to 2011 to determine changes of the glaciated surface and snow line elevation in six mountain areas of the Cordillera Huaytapallana range in Peru. In contrast to other Peruvian mountains, glacier retreat in these mountains has been poorly documented, even though this is a heavily glaciated area. These glaciers are the main source of water for the surrounding lowlands, and melting of these glaciers has triggered several outburst floods. During the 28-year study period, there was a 55% decrease in the surface covered by glaciers and the snowline moved upward in different regions by 93 to 157 m. Moreover, several new lakes formed in the recently deglaciated areas. There was an increase in precipitation during the wet season (October-April) over the 28-year study period. The significant increase in maximum temperatures may be related to the significant glacier retreat in the study area. There were significant differences in the wet season temperatures during El Niño (warmer) and La Niña (colder) years. Although La Niña years were generally more humid than El Niño years, these differences were not statistically significant. Thus, glaciers tended to retreat at a high rate during El Niño years, but tended to be stable or increase during La Niña years, although there were some notable deviations from this general pattern. Climate simulations for 2021 to 2050, based on the most optimistic assumptions of greenhouse gas concentrations, forecast a continuation of climate warming at the same rate as documented here. Such changes in temperature might lead to a critical situation for the glaciers of the Cordillera Huaytapallana, and may significantly impact the water resources, ecology, and natural hazards of the surrounding areas.

  3. A new species of columnea (gesneriaceae) from the cordillera oriental of colombia

    OpenAIRE

    Amaya Marisol

    2012-01-01

    A new species of Columnea belonging to section Collandra (Gesneriaceae) is described and illustrated. The species is found in the Eastern Andes of Colombia (CordilleraOriental), in the Departamento of Santander.

  4. A NEW SPECIES OF COLUMNEA (GESNERIACEAE FROM THE CORDILLERA ORIENTAL OF COLOMBIA

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    Amaya Marisol

    2010-06-01

    Full Text Available A new species of Columnea belonging to section Collandra (Gesneriaceae is described and illustrated. The species is found in the Eastern Andes of Colombia (CordilleraOriental, in the Departamento of Santander.

  5. Las doleritas toleíticas triásicas del sector SE de la Cordillera Ibérica: petrología y geoquímica

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    Bastida Cuairán, J.

    1999-12-01

    Full Text Available The tholeiitic dolerites that crop out in three diapirs of the SE of the Iberian Chain (Alfarp, Quesa and Lugar Nuevo de Fenollet, Valencia, are the expression of evolved (low Ni, Cr and mg* values basic magmas, injected into poorly lithified sediments (lutites, marls and gypsum which represent the Upper Triassic (Keuper facies-Hettangian boundary, developing sills with reduced thickness. Their mineral and whole-rock geochemical compositions indicate a continental tholeiitic affinity and certain similarities to a MORB composition and, on the other hand, show that the Alfarp dolerites represent the less evolved compositions, whereas the Fenollet dolerites show a significantly greater differentiation. These rocks are the expression of a shallow magmatism, related to the initial stages of the mesozoic rifting that affected the intersection of the Celtiberian Rift with the Betic Graben. This magmatism is clearly different of the isochronous tholeiitic magmatism (dolerites which crops out at the Pyrenees and Betic.Las doleritas toleíticas aflorantes en diapiros triásicos del SE de la Cordillera Ibérica (Alfarp, Quesa y Lugar Nuevo de Fenollet, SE de Valencia representan líquidos diferenciados (valores bajos en Ni, Cr y mg* emplazados como sills, de escaso espesor, por debajo de sedimentos (arcillas, margas y yesos, poco consolidados, del límite Triásico superior-Hettangiense. Su composición mineral y geoquímica, con afinidad toleítica continental y similitud a MORB, evidencia el carácter menos diferenciado de las doleritas de Alfarp, respecto a las de Quesa, siendo las doleritas aflorantes en Fenollet las que presentan una composición más evolucionada. Estas doleritas son la expresión de un magmatismo poco profundo, asociado al inicio del rifting mesozoico, desarrollado en la zona de intersección del rift celtibérico y el borde NE del surco bético. Este magmatismo presenta claras diferencias respecto a las doleritas toleíticas, menos

  6. P and S Wave Finite-frequency Imaging of the Cordillera-craton Boundary Zone in Western Canada

    Science.gov (United States)

    Gu, Y. J.; Chen, Y.; Hung, S. H.

    2016-12-01

    The Western Canada Sedimentary Basin (WCSB) marks a boundary zone and a strong seismic lateral velocity gradient in the upper mantle between the Precambrian North American craton and the Phanerozoic Cordillera. While much of the tectonic imprints are buried below thick sediments, seismic data coverage in this region has been greatly improved to unravel the underlying structure, owing to a growing number of regional broadband arrays. In this study we conduct a high-resolution survey of the mantle P- and S-wave velocities in the WCSB using a multi-scale parameterization and the finite-frequency theory. Our models suggest respective increases of 4% and 6% of Vp and Vs velocities across the Cordilleran Deformation Front (CDF) toward the craton interior. This sharp gradient resides to the west of the CDF, which may imply the over-thrusting of the crustal terranes of the Cordillera onto the craton edge. Significant along-strike variation in the lithospheric basal geometry and dip could reflect secular tectonic modifications such as episodic shortening/extension and convective erosion. The results of our finite-frequency tomography indicate vertically continuous high velocities at least down to 200 km beneath the crustal domains of the Precambrian Buffalo Head Terrane (BHT), Hearne craton and Medicine Hat Block (MHB). The lithosphere beneath the southern Hearne province could extend down to 280 km, nearly 70 km deeper than those of its neighboring cratons of similar ages. The velocity anomalies and their intricate variations/reversals within the mantle lithosphere may be evidence for a multi-stage formation of western Laurentia during Precambrian plate convergence. On the other hand, destruction processes since formation, e.g., convective removal and thermomagmatic erosion, may also have played key roles in shaping the mantle lithosphere beneath the western margin of the North American craton.

  7. Continental underthrusting and obduction during the Cretaceous closure of the Rocas Verdes rift basin, Cordillera Darwin, Patagonian Andes

    Science.gov (United States)

    Klepeis, Keith; Betka, Paul; Clarke, Geoffrey; Fanning, Mark; Hervé, Francisco; Rojas, Lisandro; Mpodozis, Constantino; Thomson, Stuart

    2010-06-01

    The Patagonian Andes record a period of Cretaceous-Neogene orogenesis that began with the compressional inversion of a Late Jurassic rift called the Rocas Verdes basin. Detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of ˜148 Ma, suggesting that the basin opened approximately simultaneously along its length during the Late Jurassic. Structural data and U-Pb isotopic ages on zircon from granite plutons near the Beagle Channel (55°S) show that basin inversion involved two stages of shortening separated by tens of millions of years. An initial stage created a small (˜60 km wide) thrust wedge that placed the basaltic floor of the Rocas Verdes basin on top of adjacent continental crust prior to ˜86 Ma. Structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in Cordillera Darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of ˜35 km beneath a coeval volcanic arc. A subsequent stage of out-of-sequence thrusting, culminating in the Paleogene, shortened basement and Upper Jurassic igneous rock in the internal part of the belt by at least ˜50 km, forming a bivergent thrust wedge. This latter period coincided with the exhumation of rocks in Cordillera Darwin and expansion of the fold-thrust belt into the Magallanes foreland basin. This orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi-oceanic rift basin.

  8. La cordillera como elemento significativo que permite entender la condición del narrador en Al oído de la cordillera

    OpenAIRE

    2015-01-01

    La obra de Ignacio Piedrahíta es un relato de viaje que narra la travesía de un hombre desde Colombia hasta Tierra del Fuego en la Argentina. A través del recorrido el narrador reflexiona sobre sí a partir de la observación de la naturaleza. De allí que este trabajo busque: primero destacar cómo el espacio-tiempo de la cordillera, estructura la forma y el contenido de la obra; segundo, entender la cordillera como un texto permite los efectos de meditación y de narrativa de la experiencia del ...

  9. A regional view of fluctuations in glacier length in southern South America

    NARCIS (Netherlands)

    Lopez, P.; Chevallier, P.; Favier, V.; Pouyaud, B.; Ordenes, F.; Oerlemans, J.

    2010-01-01

    Fluctuations in the length of 72 glaciers in the Northern and Southern Patagonia Icefield (NPI and SPI, respectively) and the Cordillera Darwin Icefield (CDI) were estimated between 1945 and 2005. The information obtained from historical maps based on 1945 aerial photographs was compared to ASTER an

  10. A new species of Andean semiaquatic lizard of the genus Potamites (Sauria, Gymnophtalmidae from southern Peru

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    Germán Chávez

    2012-01-01

    Full Text Available We describe a new lizard species of the genus Potamites from the montane forests of the Cordillera de Vilcabamba (Cusco region and Apurimac River valley (Ayacucho region, between 1500 and 2000 meters of elevation, in southern Peru. The new species is distinguishable from all other species of the genus mainly byhighly keeled scattered scales on dorsum and females lacking femoral pores.

  11. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    NARCIS (Netherlands)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J.J.; Lodolo, Emanuele

    2015-01-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known a

  12. Paleogene depositional patterns in the Magdalena Valley and Cordillera Oriental: Implications for deformational phases

    Energy Technology Data Exchange (ETDEWEB)

    Ressetar, R.; Allen, R.B.; Alfonso, C.A. (Univ. of South Carolina, Columbia (United States)); Sarmiento, L. (Instituto Colombiano de Petroleos, Bucaramanga (Colombia)); Ramirez, C.; Laverde, F. (Hocol-Shell, Cartagena (Colombia))

    1993-02-01

    The Paleogene rocks of the Magdalena Valley and the Cordillera Oriental of Colombia represent the synorogenic sedimentary fill of the ancestral Andean foreland basin. Although detailed correlation of the Paleogene is hampered by poor biostratigraphic control, recent field studies document variations between the Upper and Middle Magdalena Valleys in vertical facies succession and paleocurrent direction, suggesting independent depositional systems separated by the Girardot fold belt. In the northern Upper Magdalena Valley, the Paleogene Gualanday Group lies unconformably to paraconformably on marine Upper Cretaceous and Paleocene rocks. Lower and upperconglomeratic units in the Gualanday Group grade eastward into finer grained fluvial sandstones in the western Cordillera Oriental. North of the Girardot belt, conglomerates occur only in the lower part of the Paleogene and grade northeastward into fluvial sandstones. These unconformably overlie rocks as old as Neocomian in a series of en echelon structures on the west flank of the Cordillera Oriental. The structural trends and thickness of the Cretaceous here suggest inversion of the marine depocenter prior to Paleogene deposition. Previous reports of early Paleogene uplift of the Quetame Massif south of Bogota indicate that similar processes acted elsewhere in the Cordillera Oriental. These studies show that the Cordillera Oriental underwent at least one phase of uplift prior to the main inversion in the Neogene.

  13. Comparison of terrane accretion in modern Southeast Asia and the Mesozoic North American Cordillera

    Science.gov (United States)

    Silver, Eli A.; Smith, Randall B.

    1983-04-01

    The western part of the North American Cordillera has been divided into numerous suspect terranes. Some of these terranes have traveled hundreds to thousands of kilometres between the time of their formation and their final incorporation into the accretionary belt of the Cordillera. Most of the terranes appear to be relics of island arcs, oceanic plateaus and islands, continental margin fragments, and complex accretionary terranes, the latter including melange belts, ophiolite fragments, and thrust-faulted forearc provinces. Because the terranes have complex histories and diverse stratigraphies, it has been difficult to envisage an actualistic setting for the Mesozoic Cordillera. Here we propose an analogy with the tectonic setting of the Indo-Pacific region, from the Tonga trench on the east to eastern Indonesia on the west. This region comprises several distinct island arcs, several large oceanic plateaus, numerous accretionary terranes, melange zones, ophiolite fragments, and a variety of continental fragments, all moving toward the central collision zone. Like the Cordillera, this part of the Indo-Pacific region is undergoing oblique convergence, driven by relatively high rates of movement between the oceanic plates and the collision zone. Also analogous to the Cordillera is the formation of a foreland fold and thrust belt, developing between the collision zone and the Australian continent, and a zone of basement-rooted foreland folds, suggestive of an early Laramide style of deformation. *Present address: Sohio Petroleum Company, Denver, Colorado 80202

  14. Late Cenozoic Deformation of the Coastal Cordillera, Northern Chilean Forearc, 18- 25°S

    Science.gov (United States)

    Allmendinger, R. W.; González, G.; Loveless, J. P.; Carrizo, D.

    2007-12-01

    Overlying the only part of the South American continental crust that is in direct contact with the subducting Nazca Plate, the Coastal Cordillera of northern Chile and southern Peru should provide the most complete geological record of the coupling between the two plates. This record of coupling is exquisitely preserved in the hyperarid Atacama Desert. This preservation is both one of the major advantages and major challenges of working in this region: On the positive side, exposure of geomorphic surfaces is complete and unencumbered by erosion or vegetation, and brittle saline soils preserve subtle deformation features that would quickly be obliterated in more humid environments. On the negative side, ancient geomorphic features are just as fresh as Recent one and the lack of organic material precludes radiocarbon dating, a traditional tool of paleoseismology. During the last several years, we have concentrated on documenting three fundamental characteristics of late Cenozoic forearc deformation: (1) NS shortening on reverse faults striking at a high angle to, and dextral-reverse faults striking oblique to, the continental margin; (2) N-striking normal faults of the forearc and their reactivation, locally, as reverse faults; and (3) extensive suites of tension cracks. Reverse faults striking at a high angle to the margin are present between 19 and 21.5°S, straddling the topographic symmetry plane that marks the axis of the Bolivian orocline. Limited dating of tuffs and surfaces shows that these structures have been active for at least the last 6 Ma. At least 5 of these structures -- Atajaña, Pisagua, Iquique north and south, and Barranco Alto -- cut the Pleistocene marine terraces of the coastal platform, producing 20 to 50 m of vertical offset. A forearc crustal earthquake just south of Pisagua in March 2007 demonstrates that margin parallel shortening continues to the present and that permanent deformation occurs during the interseismic part of the plate

  15. Hydraulic brecciation on top of the Alboran Domain and its relationship with Lower Miocene deposits (Western Betics)

    OpenAIRE

    Suades, Enric; Crespo Blanc, Ana

    2010-01-01

    Al oeste de las Cordilleras Béticas, se describen unos cuerpos de brechas dentro del Complejo Maláguide, muy similares a las brechas del Mioceno inferior del grupo Viñuela. La distribución, geometría interna y características petrográficas de dichos cuerpos muestran que pueden haberse formado durante procesos cataclásticos acompañados por fracturación hidráulica. Se sugiere que estos cuerpos de brechas tectónicas nutren las brechas sedimentarias del grupo Viñuela

  16. Investigation of a measles outbreak in Cordillera, northern Philippines, 2013

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    Paola Katrina Ching

    2016-07-01

    Full Text Available Introduction: Measles is a highly infectious viral illness that remains one of the leading causes of death among children worldwide. In the Philippines, decreasing routine vaccination coverage from 2007 to 2011 led to local measles outbreaks. A team investigated a measles outbreak reported in Cordillera of the Philippines in May 2013. Methods: Measles case data with symptom onset from 2 February to 27 May 2013 were obtained from official sources and verified on site. Data included age, sex, residential address, signs and symptoms and vaccination status. Active case-findings were also conducted for contacts of these cases. The living environments of the cases were investigated. A survey was conducted with the cases and caregivers to understand their knowledge and attitudes about measles. Results: There were 50 measles cases identified with an age range from six months to 32 years (median: 16 years. Thirty-two were male (64%. Twenty (40% were hospitalized with one death. Thirty-two (64% cases were laboratory confirmed, and 36 (72% received a single dose of measles vaccine. Overcrowded living environments were observed among many cases. The majority of respondents (46/48, 96% knew about measles, but there were misconceptions about the cause of measles and how it can be prevented and managed. Conclusion: This measles outbreak occurred in an area with low immunization coverage. Achieving 95% measles immunization coverage and strengthening routine immunization strategies to address high-risk populations are recommended. Also, we recommend health education campaigns to include components that address misconceptions about measles.

  17. Investigation of a measles outbreak in Cordillera, Northern Philippines, 2013

    Science.gov (United States)

    Zapanta, Ma Justina; de los Reyes, Vikki Carr; Tayag, Enrique; Magpantay, Rio

    2016-01-01

    Introduction Measles is a highly infectious viral illness that remains one of the leading causes of death among children worldwide. In the Philippines, decreasing routine vaccination coverage from 2007 to 2011 led to local measles outbreaks. A team investigated a measles outbreak reported in Cordillera of the Philippines in May 2013. Methods Measles case data with symptom onset from 2 February to 27 May 2013 were obtained from official sources and verified on site. Data included age, sex, residential address, signs and symptoms and vaccination status. Active case-findings were also conducted for contacts of these cases. The living environments of the cases were investigated. A survey was conducted with the cases and caregivers to understand their knowledge and attitudes about measles. Results There were 50 measles cases identified with an age range from six months to 32 years (median: 16 years). Thirty-two were male (64%). Twenty (40%) were hospitalized with one death. Thirty-two (64%) cases were laboratory confirmed, and 36 (72%) received a single dose of measles vaccine. Overcrowded living environments were observed among many cases. The majority of respondents (46/48, 96%) knew about measles, but there were misconceptions about the cause of measles and how it can be prevented and managed. Conclusion This measles outbreak occurred in an area with low immunization coverage. Achieving 95% measles immunization coverage and strengthening routine immunization strategies to address high-risk populations are recommended. Also, we recommend health education campaigns to include components that address misconceptions about measles. PMID:27766180

  18. Present-day geodynamics of the northern North American Cordillera

    Science.gov (United States)

    Finzel, Emily S.; Flesch, Lucy M.; Ridgway, Kenneth D.

    2014-10-01

    Diffuse continental deformation results from interactions at plate boundaries, buoyancy forces generated by gradients in gravitational potential energy, and loads applied to the base of the lithosphere. Using finite element models, we calculate a deviatoric stress field associated with buoyancy forces, and then perform an iterative inversion to calculate deviatoric stress fields associated with boundary forces in the northern North American Cordillera. Our results reveal the presence of two distinct geodynamic domains. In the outboard domain, approximately equal magnitudes of boundary and buoyancy forces can account for the observed deformation along the Aleutian megathrust. In contrast, large boundary forces related to subduction of the Pacific and Yakutat slabs dominate the force-balance in south-central Alaska and combine with relatively small buoyancy forces to reproduce the observed kinematic indicators. In the inboard domain, encompassed by interior and northern Alaska and western Canada, boundary and buoyancy forces alone cannot reproduce the observed deformation. Therefore, we infer that deviatoric stresses due to basal tractions from a deeper mantle convection cell contribute to surface deformation in the inboard domain. Low effective lithospheric viscosity in south-central Alaska and the balancing effect of an independent geodynamic system driven by basal tractions in northern Alaska combine to confine the anomalously large Yakutat-related boundary deviatoric stresses to south-central Alaska. Deviatoric stresses associated with flat-slab subduction of the Yakutat microplate are a factor of two greater than boundary force estimates for the Andean and Indian-Eurasian convergent margins, where buoyancy and boundary forces are roughly equal in magnitude and dominate the force-balance.

  19. Nueva especie de rana (Atelopus de Los Farallones de Cali, Cordillera Occidental de Colombia

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    Kattan Gustavo

    1986-06-01

    Full Text Available Durante la realización de colecciones herpetológicas en el Departamento del Valle del Cauca, fue encontrada una especie no descrita de Atelopus (Anura: Bufonidae en los farallones de Cali, a 2600 m de altura. Esta es la primera especie en este género que se encuentra a elevaciones superiores a 2000 m en la Cordillera Occidental. Se conocen varias especies de Atelopus en las Cordilleras Central y Oriental de Colombia y en los Andes ecuatorianos (COCHRAN y GOIN 1970; PETERS 1973; RIVERO 1963 y probablemente futuras colecciones herpetológicas continuaran revelando nuevas especies en las partes altas de la Cordillera Occidental.

  20. Geologic evolution of the Cordillera Darwin orogenic core complex, Southern Andes

    Science.gov (United States)

    Nelson, E. P.

    1981-08-01

    Located in the east-west trending Andes of Tierra del Fuego is a structural culmination exposing deeper crustal levels than in surrounding areas, termed an orogenic core complex because of the localization there of relatively high-grade metamorphism, intense polyphase deformation, and differential uplift. Strongly deformed and regionally metamorphosed pre-Late Jurassic basement rocks mainly of sedimentary origin are unconformably overlain by a cover sequence of Upper Jurassic silicic-intermediate volcanic rocks (Tobifera Formation) and Lower Cretaceous clastic sedimentary rocks (Yahgan Formation). The D1 and D2 phases produced major and minor fold structures, extension and intersection lineations, and axial planar and transposition foliations in complex patterns similar to those in other collision-type orogens. The Darwin and Beagle suites show affinities with S- and I-type granitic suites respectively.

  1. Deformation style and controlling geodynamic processes at the eastern Guadalquivir foreland basin (Southern Spain)

    Science.gov (United States)

    Marín-Lechado, C.; Pedrera, A.; Peláez, J. A.; Ruiz-Constán, A.; González-Ramón, A.; Henares, J.

    2017-06-01

    The tectonic structure of the Guadalquivir foreland basin becomes complex eastward evolving from a single depocenter to a compartmented basin. The deformation pattern within the eastern Guadalquivir foreland basin has been characterized by combining seismic reflection profiles, boreholes, and structural field data to output a 3-D model. High-dipping NNE-SSW to NE-SW trending normal and reverse fault arrays deform the Variscan basement of the basin. These faults generally affect Tortonian sediments, which show syntectonic features sealed by the latest Miocene units. Curved and S-shaped fault traces are abundant and caused by the linkage of nearby fault segments during lateral fault propagation. Preexisting faults were reactivated either as normal or reverse faults depending on their position within the foreland. At Tortonian time, reverse faults deformed the basin forebulge, while normal faults predominated within the backbulge. Along-strike variation of the Betic foreland basin geometry is supported by an increasing mechanical coupling of the two plates (Alborán Domain and Variscan basement) toward the eastern part of the cordillera. Thus, subduction would have progressed in the western Betics, while it would have failed in the eastern one. There, the initially subducted Iberian paleomargin (Nevado-Filábride Complex) was incorporated into the upper plate promoting the transmission of collision-related compressional stresses into the foreland since the middle Miocene. Nowadays, compression is still active and produces low-magnitude earthquakes likely linked to NNE-SSW to NE-SW preexiting faults reactivated with reverse oblique-slip kinematics. Seismicity is mostly concentrated around fault tips that are frequently curved in overstepping zones.

  2. Changes in basal dip and frictional properties controlling orogenic wedge propagation and frontal collapse: the External central Betics case

    Science.gov (United States)

    Jiménez-Bonilla, Alejandro; Torvela, Taija; Balanyá, Juan-Carlos; Díaz-Azpiroz, Manuel; Expósito, Inmaculada

    2016-04-01

    Orogenic wedges and their key component, thin-skinned fold-and-thrust belts (FTBs), have been extensively studied through both field examples and modelling. The overall dynamics of FTBs are, therefore, well understood. One of the less understood aspects is: what is the combined influence of across-strike changes in the detachment properties and the basement topography on the behaviour of an orogenic wedge, as the deformation progresses towards the foreland? In this study, we use field data combined with reflection seismic interpretation and well data from the External Zones of the Central Betics FTB, S Spain, to identify a basement "threshold" coinciding with a thinning out of a weak substrate (Triassic evaporites) in the wedge basal detachment. The basal changes influenced the tempo-spatial (4D) local wedge dynamics at ~Early Langhian times, leading to stagnation of FTB propagation, topographic build-up and subsequent collapse of the FTB front, which was enhanced by arc-parallel stretching. This development led to a formation of an important depocentre filled with a thick Langhian mélange unit and later sediments deposited in the NW-migrating foreland basin. This case study illustrates the importance of across-strike changes in wedge basal properties to the stability of the FTB front, especially in terms of the collapse/extensional structures.

  3. GPS deformation rates in the Bajo Segura Basin (NE of the Eastern Betic Shear Zone, SE Spain)

    Science.gov (United States)

    Jesús Borque, María; Sánchez-Alzola, Alberto; Estévez, Antonio; García-Tortosa, Francisco J.; Martín-Rojas, Iván; Molina, Sergio; Alfaro, Pedro; Rodríguez-Caderot, Gracia; de Lacy, Clara; García-Armenteros, Juan Antonio; Avilés, Manuel; Herrera, Antonio; Rosa-Cintas, Sergio; Gil, Antonio J.

    2014-05-01

    The Bajo Segura Basin, located in the NE end of the Eastern Betic Shear Zone, is one of the areas with highest seismic activity of the Iberian Peninsula. It is bounded by the Crevillente Fault to the north and the Bajo Segura Fault to the south, and it is characterized by a Late Miocene to Quaternary folded cover. We estimate the present-day deformation of the study area from a GPS network with 11 sites. Observation campaigns were carried out four times (June 1999, September 2001, September 2002 and September 2013). We used the 6.2 version of GIPSY-OASIS software to process GPS data in Precise Point Positioning mode (PPP). In order to obtain the position time series in the whole period of these episodic campaigns, all the GPS observations from 1999 to 2013 campaigns were processed with an identical standard procedure. We compared our velocity field estimation with respect to GEODVEL tectonic model to obtain the residual velocity field of the Bajo Segura Basin. We estimated a ~N-S shortening with deformation rates varying between 0.2 and 0.6 mm/yr. These results are consistent with local geological deformation rates although slightly higher. They also fit well with regional geodetic data estimated for the Western Mediterranean.

  4. Evaporite deposits of Bogota area, Cordillera Oriental, Colombia

    Science.gov (United States)

    McLaughlin, Donald H.

    1972-01-01

    Four evaporite-bearing stratigraphic zones are known in Cretaceous strata of the Cordillera Oriental of Colombia north and east of Bogota. The easternmost and oldest zone is probably of Berriasian to Valanginian age. The next oldest is probably late Barremian to early Aptian in age. The third appears to be Aptian. The westernmost and best known sequence in the Sabana de Bogota is Turonian to early Coniacian in age. This youngest sequence contains the thickest salt deposits known in Colombia and is probably the most widespread geographically. Most of the rock salt exposed in the three accessible mines (at Zipaquira, Nemocon, and Upin) has a characteristic lamination of alternating slightly argillaceous and highly argillaceous salt layers of varied but moderate thickness. Black, calcareous claystone, commonly very pyritic, is interbedded conformably with the laminated salt in many places throughout the deposits. Fragments of black claystone derived from the thinner interbeds are ubiquitous in all deposits, both as concordant breccia zones and as isolated clasts. Anhydrite is scarce at Zipaquira and apparently even rarer at Nemocon and Upin. Gypsum is produced at three small deposits in the oldest evaporite zone where it probably was concentrated by leaching of salt initially associated with it. The two intervening evaporite zones are not exposed, but their existence and distribution are indicated by brine springs and locally by "rute," a distinctive black, calcareous mud formed by the leaching of salt beds. Fossils show that the youngest salt-claystone zone, in the Sabana de Bogota, is contemporary with associated hematitic sandstone and siltstone, and with carbonaceous and locally coaly claystone. Although evidence is poor, this same facies relation probably exists within the other three evaporite zones. All salt deposits in this study probably are associated with anticlines, a relation best exemplified by the deposits on the Sabana de Bogota. Within these

  5. Transverse Zones in the Eastern Cordillera (Colombia): An example in the Zipaquira Anticline

    Science.gov (United States)

    Garcia Delgado, H. S.; Jimenez, G.

    2014-12-01

    Lateral connectors are expressed in map view by along-strike terminations of thrust faults and ramp anticlines; by curves and offsets in strike; and by along-strike changes in angle and direction of plunge, dip of fold limbs, direction of vergence, stratigraphic level of detachment, and structural style. Such lateral connectors could be formed from reactivated transform faults, transverse faults or lateral ramps. The Zipaquira Anticline (ZA) is a salt-cored structure, with a NE-SW axial axis direction, a clear defined map-view curvature. The Neusa Transverse Zone (NTZ) controls the kinematicof faults and folds. The Zipaquirá Transverse Zone (ZTZ) is located to the southern of the ZA. This transverse zone is a key feature in the area, controlling the ZA and allowing the ascend of diapirs and salt sheets to shallow deeps. Our study was focused on Cretaceous marine sediments and Cenozoic transitional to continental sedimentary sequence around the ZA. 224 oriented cores were collected using a gas portable drill. At each site we collected 10 cores, spaced in order to try to average out secular variation. All samples were oriented using a magnetic compass, corrected to account for the local magnetic field declination. Cores were cut into standard cylindrical specimens and magnetic fabric, rock magnetic and paleomagnetic measurements were done in the shielded room of the paleomagnetic laboratory of in the IAG in the Sao Paulo University. We measured the low-field (AMS) in a Kappabridge (MFK1-FA, AGICO). All samples were thermally demagnetized up to 680°C by a shielded oven, and the natural remanent magnetization (NRM) of the specimens was measured. Magnetic mineralogy analyses were carried out to identify and characterize the main magnetic carriers. The ZA is an important example of natural connection between multiple factors controlling deformation and geological evolution. Interaction between salt, transverse zones and folding, the ZA could be considered as a scale

  6. Datacion U-PB por LA-ICP-MS de diques graniticos del ciclo pampeano, sierra de Mojotoro, Cordillera Oriental LA-ICP-MS U-Pb age from granitic dikes fr om the Pampean cycle, Sierra de Mo/otoro, Cordillera Oriental

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    Pamela A Aparicio González

    2011-03-01

    Full Text Available El objetivo del presente trabajo es dar a conocer los resultados de dataciones U-Pb por el método LA-ICP-MS sobre circones procedentes de diques de pórfido granítico que intruyen a la Formación Chachapoyas (nom. nov. en la sierra de Mojotoro, en el noroeste de Argentina. Para ello, se analizaron 20 circones euhedrales de morfologías prismáticas aciculares y transparentes. Los resultados obtenidos son concordantes en ocho granos de circones permitiendo definir una edad de cristalización para el dique de 533 ± 2 Ma. Si se asocian los nuevos datos con otros de rocas ígneas de edades similares localizadas en otros sectores de la Cordillera Oriental, se confirma un evento magmàtico ácido ocurrido en el Cámbrico inferior.A zircon U-Pb age obtained with the LA-ICP-MS method is presented for a granite porphyry from Chachapoyas Formation (nom. nop., sierra de Mojotoro, NW Argentina. 20 euhedral zircons with acicular prismatic and transparent morphology were analyzed. The data obtained is concordant in eight zircons grains and show a crystallization age of 533 ± 2 Ma. The new data could be associated with igneous rocks of similar ages located in the Eastern Cordillera, and suggest an acid magmatic event during the Lower Cambrian. This outcrop represents the southern expression of the Pampean magmatic arc in the NW of Argentina.

  7. Ethno–botanical survey of edible wild fruits in Benguet, Cordillera administrative region, the Philippines

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    Racquel Tan Chua-Barcelo

    2014-05-01

    Conclusions: Benguet province in the Cordillera region provides a diversity of edible wild fruits. The data gathered from the study signifies that collection, processing and utilization of edible wild fruits are still part of the daily activities of the people in Benguet.

  8. Stress field evolution above the Peruvian flat-slab (Cordillera Blanca, northern Peru)

    Science.gov (United States)

    Margirier, A.; Audin, L.; Robert, X.; Pêcher, A.; Schwartz, S.

    2017-08-01

    In subduction settings, the tectonic regime of the overriding plate is closely related to the geometry of the subducting plate. Flat-slab segments are supposed to increase coupling at the plate interface in the Andes, resulting in an increase and eastward migration of the shortening in the overriding plate. Above the Peruvian flat-slab, a 200 km-long normal fault trend parallel to the range and delimits the western flank of the Cordillera Blanca. In a context of flat subduction, expected to produce shortening, the presence of the Cordillera Blanca normal fault (CBNF) is surprising. We performed a systematic inversion of striated fault planes in the Cordillera Blanca region to better characterize the stress field above the Peruvian flat-slab. It evidences the succession of different tectonic regimes. NE-SW extension is predominant in most of the sites indicating a regional extension. We suggest that the Peruvian flat-slab trigger extension in the Western Cordillera while the shortening migrated eastward. Finally, we propose that flat-slab segments do not increase the coupling at the trench neither the shortening in the overriding plate but only favor shortening migration backward. However, the stress field of the overriding plate arises from the evolution of plate interface properties through time due to bathymetric anomaly migration.

  9. Petrografic description of some igneous rocks from the Cordillera of South Mendoza, in the Argentine

    NARCIS (Netherlands)

    Kuenen, Ph.H.

    1926-01-01

    Comparatively little is yet known of the intricate igneous history of the Cordillera of South Mendoza. Almost all the knowledge we have is due to the field- and stratigraphical work of Dr. H. Gerth of Leiden (bibl. 1 and 2), and the petrographic studies of Dr. H. G. Backlund (bibl. 3 and 4) on the

  10. Can cosmic ray exposure dating reveal the normal faulting activity of the Cordillera Blanca Fault, Peru?

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    L.L. Siame

    2006-12-01

    Full Text Available The build-up of in situ-produced cosmogenic 10Be within bedrock scarps and escarpments associated to the Cordillera Blanca Normal Fault, Peru, was measured to evaluate, through Cosmic Ray Exposure dating, its normal faulting activity. The highest mountain peaks in Peru belong to the 210 km-long, NW- striking, Cordillera Blanca. Along its western border, the Cordillera Blanca Normal Fault is responsible for a vertical relief over 4.4 km, whose prominent 2 km high escarpment is characterized by ~1 km-high triangular facets corresponding to vertical displacements cumulated during the last 1-2 million years. At a more detailed scale, this fault system exhibits continuous geomorphic evidence of repeated displacements, underlined by 2 to 70 m-high scarps, corresponding to vertical displacements cumulated since Late Pleistocene and Holocene periods. Although microseismicity occurs along the Cordillera Blanca Normal Fault, no major historical or instrumental earthquake has been recorded since the beginning of the Spanish settlement in the 16th century. To evaluate the vertical slip rate along the major 90 km-long central segment of the Cordillera Blanca Normal Fault, the Quaternary fault escarpment (i.e., triangular facet, as well as the bedrock fault scarp, have been sampled for 10Be Cosmic Ray Exposure dating. Even if the uppermost part of the triangular facets have been resurfaced by the Last Glacial Maximum glaciers, our results allow to estimate a vertical slip-rate of 3±1 mm/yr, and suggest at least 2 seismic events during the last 3000 years.

  11. Flow in the western Mediterranean shallow mantle: Insights from xenoliths in Pliocene alkali basalts from SE Iberia (eastern Betics, Spain)

    Science.gov (United States)

    Hidas, Károly; Konc, Zoltán.; Garrido, Carlos J.; Tommasi, Andréa.; Vauchez, Alain; Padrón-Navarta, José Alberto; Marchesi, Claudio; Booth-Rea, Guillermo; Acosta-Vigil, Antonio; Szabó, Csaba; Varas-Reus, María. Isabel; Gervilla, Fernando

    2016-11-01

    Mantle xenoliths in Pliocene alkali basalts of the eastern Betics (SE Iberia, Spain) are spinel ± plagioclase lherzolite, with minor harzburgite and wehrlite, displaying porphyroclastic or equigranular textures. Equigranular peridotites have olivine crystal preferred orientation (CPO) patterns similar to those of porphyroclastic xenoliths but slightly more dispersed. Olivine CPO shows [100]-fiber patterns characterized by strong alignment of [100]-axes subparallel to the stretching lineation and a girdle distribution of [010]-axes normal to it. This pattern is consistent with simple shear or transtensional deformation accommodated by dislocation creep. One xenolith provides evidence for synkinematic reactive percolation of subduction-related Si-rich melts/fluids that resulted in oriented crystallization of orthopyroxene. Despite a seemingly undeformed microstructure, the CPO in orthopyroxenite veins in composite xenoliths is identical to those of pyroxenes in the host peridotite, suggesting late-kinematic crystallization. Based on these observations, we propose that the annealing producing the equigranular microstructures was triggered by melt percolation in the shallow subcontinental lithospheric mantle coeval to the late Neogene formation of veins in composite xenoliths. Calculated seismic properties are characterized by fast propagation of P waves and polarization of fast S waves parallel to olivine [100]-axis (stretching lineation). These data are compatible with present-day seismic anisotropy observations in SE Iberia if the foliations in the lithospheric mantle are steeply dipping and lineations are subhorizontal with ENE strike, implying dominantly horizontal mantle flow in the ENE-WSW direction within vertical planes, that is, subparallel to the paleo-Iberian margin. The measured anisotropy could thus reflect a lithospheric fabric due to strike-slip deformation in the late Miocene in the context of WSW tearing of the subducted south Iberian margin

  12. Analogue modelling of inclined, brittle-ductile transpression: Testing analytical models through natural shear zones (external Betics)

    Science.gov (United States)

    Barcos, L.; Díaz-Azpiroz, M.; Balanyá, J. C.; Expósito, I.; Jiménez-Bonilla, A.; Faccenna, C.

    2016-07-01

    The combination of analytical and analogue models gives new opportunities to better understand the kinematic parameters controlling the evolution of transpression zones. In this work, we carried out a set of analogue models using the kinematic parameters of transpressional deformation obtained by applying a general triclinic transpression analytical model to a tabular-shaped shear zone in the external Betic Chain (Torcal de Antequera massif). According to the results of the analytical model, we used two oblique convergence angles to reproduce the main structural and kinematic features of structural domains observed within the Torcal de Antequera massif (α = 15° for the outer domains and α = 30° for the inner domain). Two parallel inclined backstops (one fixed and the other mobile) reproduce the geometry of the shear zone walls of the natural case. Additionally, we applied digital particle image velocimetry (PIV) method to calculate the velocity field of the incremental deformation. Our results suggest that the spatial distribution of the main structures observed in the Torcal de Antequera massif reflects different modes of strain partitioning and strain localization between two domain types, which are related to the variation in the oblique convergence angle and the presence of steep planar velocity - and rheological - discontinuities (the shear zone walls in the natural case). In the 15° model, strain partitioning is simple and strain localization is high: a single narrow shear zone is developed close and parallel to the fixed backstop, bounded by strike-slip faults and internally deformed by R and P shears. In the 30° model, strain partitioning is strong, generating regularly spaced oblique-to-the backstops thrusts and strike-slip faults. At final stages of the 30° experiment, deformation affects the entire model box. Our results show that the application of analytical modelling to natural transpressive zones related to upper crustal deformation

  13. The Miocene-Pliocene unconformity in the North Betic corridor. The expression of the reflector "M" in the Atlantic

    Science.gov (United States)

    Sierro, Francisco J.; Ledesma, Santiago; A: Flores, Jose; Garcia-Castellanos, Daniel; Hernandez-Molina, Javier

    2014-05-01

    The Miocene Pliocene boundary is associated in the Mediterranean to a major flooding of Atlantic water that terminated with the Messinian salinity crisis. In many seismic profiles all over the Mediterranean margins this event is linked to an erosion surface that separates the Messinian evaporitic units from the overlying open marine Pliocene sediments. This unconformity originally identified as reflector "M" can be traced to the deep basins as a paraconformity / local erosional surface that has been usually named as Horizon M. This erosive surface in Mediterranean continental margins has been linked to a pronounced drawdown of base level triggered during the Messinian. In consequence, this unconformity should be only expressed in the Mediterranean. However, a significant unconformity has been recognized in the Guadalquivir basin and in the Gulf of Cadiz in the Atlantic side of Iberia that is identified as a Messinian canyon deepening towards the Atlantic. Recently, the cyclostratigraphic and biostratigraphic analyses of various logs recovered by different oil and gas exploration companies over the last decades allowed us to accurately date this major discontinuity in the Guadalquivir basin and the Gulf of Cadiz, as well as to compare sedimentary cycles in the Atlantic with those of the Mediterranean. The astronomical tuning of these cycles unambiguously links this discontinuity in the Atlantic with the Miocene Pliocene boundary, raising important questions about the origin of this major event. We explore the potential origins for this discontinuity, including the tectonic vertical motions of the Betic-Guadalquivir system, or the presence of a seaway undergoing intense bottom-current circulation between the Mediterranean and the Atlantic.

  14. Regional Analysis of the Hazard Level of Glacial Lakes in the Cordillera Blanca, Peru

    Science.gov (United States)

    Chisolm, Rachel E.; Jhon Sanchez Leon, Walter; McKinney, Daene C.; Cochachin Rapre, Alejo

    2016-04-01

    The Cordillera Blanca mountain range is the highest in Peru and contains many of the world's tropical glaciers. This region is severely impacted by climate change causing accelerated glacier retreat. Secondary impacts of climate change on glacier retreat include stress on water resources and the risk of glacial lake outburst floods (GLOFs) from the many lakes that are forming and growing at the base of glaciers. A number of GLOFs originating from lakes in the Cordillera Blanca have occurred over the last century, several of which have had catastrophic impacts on cities and communities downstream. Glaciologists and engineers in Peru have been studying the lakes of the Cordillera Blanca for many years and have identified several lakes that are considered dangerous. However, a systematic analysis of all the lakes in the Cordillera Blanca has never before been attempted. Some methodologies for this type of systematic analysis have been proposed (eg. Emmer and Vilimek 2014; Wang, et al. 2011), but as yet they have only been applied to a few select lakes in the Cordillera Blanca. This study uses remotely sensed data to study all of the lakes of the Glacial Lake Inventory published by the Glaciology and Water Resources Unit of Peru's National Water Authority (UGRH 2011). The objective of this study is to assign a level of potential hazard to each glacial lake in the Cordillera Blanca and to ascertain if any of the lakes beyond those that have already been studied might pose a danger to nearby populations. A number of parameters of analysis, both quantitative and qualitative, have been selected to assess the hazard level of each glacial lake in the Cordillera Blanca using digital elevation models, satellite imagery, and glacier outlines. These parameters are then combined to come up with a preliminary assessment of the hazard level of each lake; the equation weighting each parameter draws on previously published methodologies but is tailored to the regional characteristics

  15. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constriction domain of conjugate strike-slip faults: the Palomares and Polopos fault zones (eastern Betics, SE Spain)

    Science.gov (United States)

    Giaconia, F.; Booth-Rea, G.; Martínez-Martínez, J. M.; Pérez-Peña, V.; Azañón, J. M.

    2012-04-01

    Segments of the Quaternary sinistral Carboneras and Palomares fault zones, striking NE-SW and NNE-SSW, respectively, terminate in the Sierra Cabrera antiform together with the conjugate dextral WNW-ESE striking Polopos fault zone. In the constriction domain between these fault zones a pop-up structure occurs formed by the North and the South Cabrera reverse faults that bound the northern and the southern hillslopes, respectively. In order to test the Quaternary activity and relief control of these fault zones, here we present new qualitative and quantitative geomorphic analyses for the Sierra Cabrera using the following indices: mountain-front sinuosity, valley floor width-to-height ratio, drainage basin asymmetry factor, basin hypsometric curve and integral, and the SLk index. These analyses were performed with the aid of several maps such as the SLk and the minimum bulk erosion map. Qualitative observations carried out on the drainage network highlight the existence of a Late Miocene fold-related drainage network and a following late Miocene to Plio-Quaternary fault-related one. Integrating the mountain-front sinuosity and the valley floor width-to-height ratio for each mountain front we estimated the uplift rates associated to each of them. Fault-related mountain-fronts with a N50-60°E strike have reverse kinematics and uplift rates larger than 0.5 m ky-1 (e.g. North and South Cabrera reverse faults), whereas those with N20-30°E and N90-100°E strikes show oblique strike-slip kinematics and show lower uplift rates, between 0.05 and 0.5 m ky-1 (e.g. the Palomares and the Polopos fault segments). Furthermore, these faults produce knickpoints, complex basin hypsometric curves, high SLk anomalies and highly eroded basins above the fault traces. The estimated uplift rates are larger than those obtained from other authors for strike-slip faults in the eastern Betics that range between 0.1 and 0.05 m ky-1 (e.g. Palomares and southern Carboneras strike-slip fault

  16. Crustal Seismicity and Recent Faults in Southern Peru

    Science.gov (United States)

    David, C.; Comte, D.; Tavera, H.; Audin, L.; Herail, G.

    2004-12-01

    Most seismological studies in southern Peru have been focused on the downgoing slab seismicity in order to constrain the Wadati-Benioff zone. This study deals with the intra-continental seismicity of the southern Peru forearc (17,3° S - 18,5° S) in a post-seismic context (Arequipa thrust earthquake, Mw=8.4, 23 June, 2001). It is difficult to identify historical crustal earthquake from available catalogues, however some crustal events teleseismically recorded can be found since 1976; they exhibit normal focal mechanism solutions in the southern Peru volcanic arc and inverse focal mechanism solutions in the Central Depression. Following a notable increase of shallow crustal seismicity located close to the Western Cordillera after the 23 June 2001, a temporary seismic network was deployed between January and March 2003 in order to study the Wadati-Benioff zone and monitoring the crustal seismicity in southern Peru. From the about 1700 events locally recorded by the local network, 300 crustal earthquakes were identified in the Peruvian forearc between Tacna and Moquegua. This crustal seismicity is distributed along a lineament located at depths between 0 and 60 km, dipping at about 45° from the Western Cordillera towards the coast, almost perpendicular to the subducting slab; this behaviour was previously observed in northern Chile and in southern Peru, north of the study zone (16° S). In the Central Depression, seismic activity is not superficial occurring between 25-60 km depth and it is mostly characterized by inverse focal mechanism solutions. Superficial faults situated in the Central Depression and in the Coastal Cordillera can not be associated with the seismic activity observed in this area. However, in the Pre-Cordillera, crustal seismicity occurs at depths between 0-15 km and can be correlated with shallow fault systems recognized by satellite images and on the field. For examples, the Incapuquio fault system which was a transpressive system in Cretaceous

  17. The Columbia Plateau Revealed; Low Temperature Thermochronology Across the Canadian Cordillera and Links to Lithospheric Delamination.

    Science.gov (United States)

    Guest, B.; Bacque, D.; Miles, N.; Stockli, D. F.

    2014-12-01

    Active deformation and mountain building in the Canadian Cordillera ceased in the Paleogene, a period during which this orogen was among the highest on earth. The present morphology, relief and altitude of the mountains and the foothills in the adjacent foreland belt are the result of a feedback relationship between erosion and isostatic compensation. Our low temperature thermochronology data (U-Th/He ages on zircon and apatite) were collected from 5 sample-transects spanning the Intermontane, Omineca, Foreland, and Foothills belts along a Jasper-Vancouver transect. The data show rapid cooling (>15℃/Ma) from >180℃ to RMT) during the Eocene (56 - 33 Ma). In the Foreland and Foothills belts to the east of the RMT the data show modest cooling (~4℃/Ma) during the latest Cretaceous to Early Eocene (~80Ma - 55 Ma) followed by rapid cooling (~15℃/Ma) between ~55 Ma and ~45 Ma transitioning to slower cooling (~1℃/Ma) after 45 Ma. This cooling pattern is consistent with rapid regional uplift and exhumation across the interior belts of the Cordillera during a regional transition from contraction to extension in the early to middle Eocene. At the same time in the Foreland and Foothills belts, during a period of accelerated cooling, contraction was continuing. The combination of rapid exhumation and extension in the interior belts and rapid exhumation and contraction in the Foreland and Foothills belts is similar to what is observed around the Altiplano and Tibetan plateaus. This suggests that the Canadian Cordillera is a fossil plateau (Columbia Plateau) that formed in the Eocene. The lack of a mantle lithosphere beneath the interior belts of the Canadian Cordillera (west of the RMT) and the regional extent of rapid exhumation suggests that the Columbia Plateau formed in response to a large-scale lithosphere removal event; possibly wholesale delamination.

  18. Oblique transpression in the western thrust front of the Colombian Eastern Cordillera

    Science.gov (United States)

    Acosta, J.; Lonergan, L.; Coward, M. P.

    2004-11-01

    New kinematic data reveal that the main faults of the western foothills of the Colombian Eastern Cordillera are a series of left-lateral to oblique thrusts that are offset by steeply dipping, northwest-trending, left-lateral, strike-slip faults. Kinematic data were collected from the main structures that dominate the 350-km length of the western foothills of the Eastern Cordillera, north of Bogota (La Salina-Bituima, Cambrás, Dos Hermanos-Alto del Trigo, and Bucaramanga faults). These data indicate that transpression is responsible for the Cenozoic formation of the folds and thrusts that deform the Mesozoic and Cenozoic sedimentary sequences of the Middle Magdalena Valley. Kinematic and structural data suggest that the La Salina-Bituima fault changed from a reverse fault to a fault with a left-lateral, strike-slip sense of displacement during middle to late Miocene times. As it propagated, a transpressive zone was generated in the western foothills of the Eastern Cordillera, with the development of arcuate, oblique-reverse secondary faults on the leading edge of the Magdalena basin (e.g. Cambrás, Dos Hermanos). This development implies that during the Neogene (?), the tectonics of the western foothills were dominated by nonplanar deformation with shortening accompanied by significant left-lateral, strike-slip displacements. These new data indicate that the oblique convergence vector imposed by convergence among the Nazca, Caribbean, and South American plates is not fully partitioned in space but instead must be distributed in a diffuse zone of transpressional deformation along the western margin of the Eastern Cordillera and its associated foreland basin.

  19. Three new species of Eleutherodactylus (Amphibia: Leptodactylidae from high elevations of the cordillera Central of Colombia

    Directory of Open Access Journals (Sweden)

    Lynch John D.

    1996-11-01

    Full Text Available A new species of the Eleutherodactylus orcesi group, the smallest member of the group, is described from the Páramo de los Valles (Tolima. It is very similar to E. slmoterus. From the same locality, a new species of dwarf Eleutherodactylus, lacking a tympanum, is described. It appears to be a member of the E. myersi group. Lastly, a new large black Eleutherodactylusis described from páramo and subpáramo habitats of the Cordillera Central. This species is distributed from Antioquia to Cauca. With these three species, fifteen species of Eleutherodactylus are known for páramo and subpáramo habitats of the Cordillera Central north of the Macizo de Pasto. These 15 species be long to tour species groups.Se describe una especie nueva del grupo de Eleutherodactylus orcesi del Páramo de los Valles (Tolima. Esta especie es muy parecida a E. simoterus pero se distingue por su tamaño (la especie nueva es la más pequeña del grupo. Se describe también una especie enanita del Páramo de los Valles que posiblemente es una especie del grupo de Eleutherodactylus myersl. La especie es muy distinta porque carece de tímpano. Finalmente, se describe una especie grande y negra que se encuentra desde Antioquia hacia Cauca en la Cordillera Central. Con estas especies, tenemos 15 especies de Eleutherodactylus conocidas de los páramos y subpáramos de la Cordillera Central al norte del Macizo de Pasto, que pertenecen a cuatro grupos de especies.

  20. Cretaceous and Tertiary terrane accretion in the Cordillera Occidental of the Andes of Ecuador

    Science.gov (United States)

    Hughes, Richard A.; Pilatasig, Luis F.

    2002-02-01

    New field, geochronological, geochemical and biostratigraphical data indicate that the central and northern parts of the Cordillera Occidental of the Andes of Ecuador comprise two terranes. The older (Pallatanga) terrane consists of an early to late (?) Cretaceous oceanic plateau suite, late Cretaceous marine turbidites derived from an unknown basaltic to andesitic volcanic source, and a tectonic mélange of probable late Cretaceous age. The younger (Macuchi) terrane consists of a volcanosedimentary island arc sequence, derived from a basaltic to andesitic source. A previously unidentified, regionally important dextral shear zone named the Chimbo-Toachi shear zone separates the two terranes. Regional evidence suggests that the Pallatanga terrane was accreted to the continental margin (the already accreted Cordillera Real) in Campanian times, producing a tectonic mélange in the suture zone. The Macuchi terrane was accreted to the Pallatanga terrane along the Chimbo-Toachi shear zone during the late Eocene, probably in a dextral shear regime. The correlation of Cretaceous rocks and accretionary events in the Cordillera Occidental of Ecuador and Colombia remains problematical, but the late Eocene event is recognised along the northern Andean margin.

  1. THE PAIPA VOLCANO, EASTERN CORDILLERA OF COLOMBIA, SOUTH AMERICA (PART II: PETROGRAPHY AND MAJOR ELEMENTS PETROLOGY

    Directory of Open Access Journals (Sweden)

    Cepeda Héctor

    2005-08-01

    Full Text Available Paipa volcano products are mainly pyroclastic pumice and ash flow tuffs, lava domes and pyroclastic block and ash flow tuffs. They are classified as alkaline rhyolites and trachytes and high-K calcalkaline rhyolites. Chemical data show SiO2 values between 68 and 72%, and alkalis (Na2O+K2O content of 7%-10%. Essential minerals are phenocrysts and glomerocrysts of anorthoclase, sanidine up to 1,5 cm and anorthoclase-mantled plagioclase; accessory minerals are red biotite, and hastingsite while trace minerals are augite, zircon, sphene and magnetite. Crystals have disequilibrium textures, such as dissolution embayments, corrosion and reabsortion borders, normal, inverse, oscillating and patchy zonation, together with fibrous borders intercalated with euhedral borders. In correlation with published data of Iza volcanic rocks, Paipa rocks chemical composition confirms that acid and alkaline magmas that have erupted in the Eastern Cordillera of Colombia during the Neogene are strongly different from the calc-alkaline magmas that erupt in the westward active arc (Central Cordillera. Detailed structural, geochemical and geophysical research has to be done in future research to establish the geodynamic framework that governs the volcanism of the Eastern Cordillera.

  2. 18,000 years of environmental change in the Eastern Cordillera of the Bolivian Andes

    Science.gov (United States)

    Williams, J. J.; Gosling, W. D.; Coe, A. L.; Brooks, S. J.

    2010-12-01

    Mountainous regions are considered to be early warning sites for climatic change because narrow vertical species ranges mean even small temperature/precipitation variation can result in species movement. This is especially true in the tropical Andes where the complex topography of the Andean valleys allows biodiverse woodland to be separated from grassland and snow dominated peaks by just a few kilometers, with microclimates clearly playing an important role. To begin to predict the likely impacts of future climatic changes and to help protect Andean woodlands, an understanding of baseline ecological conditions and previous responses to longer-term climatic shifts is vital. The Cochabamba Basin and surrounding mountain peaks is situated within the Eastern Andean Cordillera on the margin between the Altiplano and Yungas cloud forest. We present here multi-proxy data from two high elevation (>3400 m) lake sediment records which reveal sub-500 year ecosystem response to climatic shifts since the last glacial period and the impact of pre-Hispanic human populations. The sediment cores recovered from Lakes Challacaba (17°33’ S, 65°34’ W, 3400 m) and Khomer Kocha (17°16’ S, 65°43’ W, 4153 m) span the last c. 4000 and c. 18,000 years respectively. The two sites are only 35 km apart but are positioned within very different climatic and vegetation zones; Challacaba is within a cold and seasonally dry valley, and Khomer Kotcha is located on the steep slopes above the Yungas cloud forests. Analysis of pollen, chironomid, charcoal, geochemical and physical proxies from within the sediment cores provided insight into the drivers of environmental change at a local and regional scale. The Challacaba and Khomer Kocha records are the first from the eastern flank of the Bolivian Andes to record the last 4000 years and help to fill a gap in our understanding of vegetation succession and subsequent climatic variability since the late glacial. Our results suggest that, prior

  3. A Lost Realm in the Internal Domains of the Betic-Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution.

    Science.gov (United States)

    Martín-Algarra; Messina; Perrone; Russo; Maate; Martín-Martín

    2000-07-01

    The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late-Variscan two-mica cordierite-bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T=510&j0;-530 degrees C and P=5-6 kbar) to low-temperature amphibolite facies (T>550&j0;C and P<3 kbar). Such a plutonic rock suite is unknown in any Betic-Rif unit or in the basement of the Alboran Sea, and the metamorphic evolution in the orthogneisses is different from (and older than) that of Alpujarride-Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphic rocks very similar to those studied characterize the basements of some Kabylia and Calabria-Peloritani units. Therefore, the source area is a currently lost continental-crust realm of Calabria-Peloritani-Kabylia type, located to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-latest Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorogenic basins formed on the Malaguide-Ghomaride Complex. This provenance analysis demonstrates that all these domains constituted a single continental-crust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.

  4. The El Abra stadlal in the Eastern Cordillera of Colombia (South America)

    Science.gov (United States)

    Kuhry, P.; Hooghiemstra, H.; van Geel, B.; van der Hammen, T.

    The El Abra stadial is a climatic cooling event defined in the Eastern Cordillera of Colombia, which corresponds both in timing and intensity to the Younger Dryas climatic oscillation of the northern North Atlantic region. The stadial was preceded by the relatively warm Guantiva interstadial and followed by the warm Holocene. Colder climatic conditions during the El Abra stadial caused a 400 m lowering of the upper Andean forest limit below its altitudinal location during the preceding Guantiva interstadial. Translated in temperature change, this represents a drop in mean annual temperature of approximately 2 to 3°C. The lowering of the upper forest limit and inferred temperature change for the El Abra stadial, compared to Late Holocene conditions, are in the order of 600 m and 4°C, respectively. The transition of the Guantiva interstadial to the El Abra stadial has been radiocarbon dated at 11,210 ± 90 BP and 10,820 ± 60 BP. Climatic warming may have started shortly after 10,380 ± 90 BP, and near present-day temperatures were reached at least as early as 8920 ± 100 BP. Maximum cooling was probably attained between 10,800 BP and 10,300 BP. Further (AMS) radiocarbon dating is planned to establish more exactly the timing of the El Abra stadial. A glacial advance of El Abra age, the Bocatoma stade, has been recognized in the highest part of the Colombian Eastern Cordillera, the Sierra Nevada del Cocuy. During this advance, glaciers extended some 700 m lower than at present. A climatic cooling event of El Abra age, associated with shifts of the upper Andean forest limit and glacial advances, has also been recognized in other parts of Andean Colombia, including the Central Cordillera and the Sierra Nevada de Santa Marta.

  5. Integrating Multiple Geophysical Methods to Quantify Alpine Groundwater- Surface Water Interactions: Cordillera Blanca, Peru

    Science.gov (United States)

    Glas, R. L.; Lautz, L.; McKenzie, J. M.; Baker, E. A.; Somers, L. D.; Aubry-Wake, C.; Wigmore, O.; Mark, B. G.; Moucha, R.

    2016-12-01

    Groundwater- surface water interactions in alpine catchments are often poorly understood as groundwater and hydrologic data are difficult to acquire in these remote areas. The Cordillera Blanca of Peru is a region where dry-season water supply is increasingly stressed due to the accelerated melting of glaciers throughout the range, affecting millions of people country-wide. The alpine valleys of the Cordillera Blanca have shown potential for significant groundwater storage and discharge to valley streams, which could buffer the dry-season variability of streamflow throughout the watershed as glaciers continue to recede. Known as pampas, the clay-rich, low-relief valley bottoms are interfingered with talus deposits, providing a likely pathway for groundwater recharged at the valley edges to be stored and slowly released to the stream throughout the year by springs. Multiple geophysical methods were used to determine areas of groundwater recharge and discharge as well as aquifer geometry of the pampa system. Seismic refraction tomography, vertical electrical sounding (VES), electrical resistivity tomography (ERT), and horizontal-to-vertical spectral ratio (HVSR) seismic methods were used to determine the physical properties of the unconsolidated valley sediments, the depth to saturation, and the depth to bedrock for a representative section of the Quilcayhuanca Valley in the Cordillera Blanca. Depth to saturation and lithological boundaries were constrained by comparing geophysical results to continuous records of water levels and sediment core logs from a network of seven piezometers installed to depths of up to 6 m. Preliminary results show an average depth to bedrock for the study area of 25 m, which varies spatially along with water table depths across the valley. The conceptual model of groundwater flow and storage derived from these geophysical data will be used to inform future groundwater flow models of the area, allowing for the prediction of groundwater

  6. The Early Andean Magmatic Province (EAMP): 40Ar/ 39Ar dating on Mesozoic volcanic and plutonic rocks from the Coastal Cordillera, northern Chile

    Science.gov (United States)

    Oliveros, Verónica; Féraud, Gilbert; Aguirre, Luis; Fornari, Michel; Morata, Diego

    2006-10-01

    The Early Andean Magmatic Province (EAMP), consists of about 150 000 km 3 of volcanic and plutonic units in the Coastal Cordillera of northern Chile and southern Peru and represents a major magmatic Mesozoic event in the world, for which the precise age of the thick volcanic series was unknown. Thirty 40Ar/ 39Ar analyses were carried out on primary mineral phases of volcanic and plutonic rocks from northern Chile (18°30'-24°S). Reliable plateau and "mini plateau" ages were obtained on plagioclase, amphibole and biotite from volcanic and plutonic rocks, despite widespread strong alteration degree. In the Arica, Tocopilla and Antofagasta (700 km apart) regions, the ages obtained on lava flows constrain the volcanic activity between 164 and 150 Ma and no N-S migration of volcanism is observed. The uppermost lava flows of the volcanic sequence at the type locality of the La Negra Formation extruded at ca. 153-150 Ma, suggesting the end of the volcanic activity of the arc at that time. The oldest volcanic activity occurred probably at ca. 175-170 Ma in the Iquique area, although no plateau age could be obtained. The plutonic bodies of the same regions were dated between ca. 160 and 142 Ma, indicating that they were partly contemporaneous with the volcanic activity. At least one volcanic pulse around 160 Ma is evidenced over the entire investigated reach of the EAMP, according to the ages found in Arica, Tocopilla, Michilla and Mantos Blancos regions. The episodic emplacement of huge amounts of subduction related volcanism is observed throughout the whole Andean history and particularly during the Jurassic (southern Peru, northern Chile and southern Argentina). These events probably correspond to periodic extensional geodynamic episodes, as a consequence of particular subduction conditions, such as change of obliquity of the convergence, change in the subduction angle, slab roll back effect or lower convergence rate, that remain to be precisely defined.

  7. ASPECTOS ECOLOGICOS DE UNA POBLACION DE ROEDORES EN LA CORDILLERA ORIENTAL COLOMBIANA

    OpenAIRE

    2013-01-01

    Distribution, abundancy, demographic structure, type of spatial pattems and home range of a population ofThomasomys laniger (Thomas, 1895) (RODENTIA: CRICETIDAE) from Valledel Frailejón (Frailejon valley) in Chingaza Natural National Park, on the Oriental mountain chain (cordillera Oriental) in Department of Cundinamarca, were studied from January to December of 1992.· The variation ofthe population pattems according to seasonality based on frecuency of capture ofmice in diferent trapping pha...

  8. Orogeny and drainage in the Lerma Valley region (Eastern Cordillera, Salta, Argentina) during the late Pleistocene

    OpenAIRE

    Gustavo González Bonorino; Liliana Del Valle Abascal

    2016-01-01

    En el Pleistoceno tardío, luego de la incipiente elevación de las serranías subandinas, la contracción retornó al interior del orógeno. En aquel tiempo un piedemonte conectaba los contrafuertes occidentales de la Cordillera Oriental (sierras de Lesser y Obispo) con la llanura subandina, a través de la región que hoy7 ocupan el valle de Lerma y la serranía Mojotoro-Castillejo. La contracción dio origen a las elevaciones interiores en la sierra de Vaqueros y los Cerrillos de San Miguel, y luego...

  9. Surgimiento de nuevas formas de violencias urbanas en Pereira : Caso Organización la Cordillera

    OpenAIRE

    2012-01-01

    El presente trabajo de investigación contiene la presentación de los resultados de la indagación sobre el fenómeno de nuevas violencias urbanas. El estudio se realizó en la ciudad de Pereira (Risaralda), sobre las nuevas formas de organización criminal, representada por la Organización la Cordillera, en el manejo del narcotráfico, narcomenudeo y violencia cotidiana en los barrios marginales de la ciudad. Específicamente, el estudio se centra en indagar las neo violencias monopolizadas por est...

  10. Evolución geoquímica y temporal del magmatismo básico mesozoico en las Zonas Externas de las Cordilleras Béticas

    Directory of Open Access Journals (Sweden)

    Aguirre, L.

    1995-08-01

    Full Text Available The Mesozoic basic magmatism found in the External Zones of the Betic Cordilleras (ZECB is represented either as «ophites» forming small dimension tectonic blocks intercalated in the Keuper gypsum-rich, clay sediments, or also as lava ilow bodies, most of them with pillow structures, within the Jurassic sedimentary rocks. Geochemical characteristics of these rocks indicate sorne differences between these two magmatic series. Two different chemical affinities have been carried out within the «ophites»: a with modal orthopyroxene and tholeiitic affinity; and b with modal olivine and transitionalalkaline affinity. Chemical characteristics of this last group are similar to those of the volcanic rocks from the Jurassic sediments. The field relationships found in sorne «ophite» outcrops al!ow us to deduce that the tholeiitic rocks are mostly present as extrusive rocks. However, their older whole-rock K-Ar ages range between 182 ± 9 and 187 ± 4 M.a., and do not correctly represent Upper Triassic ages. Transitional-alkaline «ophites» occur as subvolcanic rocks and their older obtained radiometric age is 137 ± 4 M.a. Al! these radiometric ages obtained may be intepreted as a result of the hybridization between the age of the Triassic magmatism and the very low- to low-grade metamorphism present in these rocks. This metamorphism is responsable for the new formed secondary paragenesis, made of prehnite + pumpel! yite + sericitie + mafic phyl!osicates. Radiometric age obtained in sorne intra-Jurassic volcanic rocks range between 155 ± 3 to 166 ± 4 M.a. These new radiometric data and field relationships are used to define the Mesozoic magmatic evolution in the ZECB. Tholeiitic magmatism was generated during an initial Triassic distensive stage. After this magmatic event, and as a consequence of an increment of the distensive regime, with important continental crust thickening, transitionalalkaline magmatism occurS. This

  11. Exhumation history of the southern Altiplano plateau (southern Bolivia) constrained by apatite fission track thermochronology

    Science.gov (United States)

    Ege, H.; Sobel, E. R.; Scheuber, E.; Jacobshagen, V.

    2007-02-01

    Although the structural geometry of the Cenozoic Altiplano-Puna plateau in the central Andes is well defined, the temporal evolution of this contractile deformation is poorly constrained. To address this shortcoming, we used apatite fission track thermochronology (AFT) to quantify the cooling and exhumation history along a transect at 21°S in southern Bolivia, through the deformed intermontane Altiplano basin, the doubly vergent thrust belt of the Eastern Cordillera and the inner foreland thrust belt east of the plateau (Interandean Zone). Thermal history modeling combined with published balanced cross sections and stratigraphic data constrain exhumation histories. Exhumation started during the late Eocene (40-36 Ma) in the central Eastern Cordillera, possibly due to bivergent thrusting and Cretaceous rift structure inversion. During the early Oligocene (33-27 Ma), exhumation spread across the study area as the current boundary thrusts of the Eastern Cordillera were activated. The inner west vergent thrust system became active in irregular order until circa 20 Ma, whereas the east vergent Interandean thrust belt formed by eastward propagating deformation since circa 30 Ma. Plateau exhumation continued at ˜0.2 mm/yr until shortening terminated by 11-7 Ma. Shortening within the plateau since circa 30 Ma did not evolve by lateral accretion of thrust wedges; the propagating deformation style is spatially confined to the foreland thrust belt, which initiated coeval to plateau deformation (Interandean Zone) but propagated mainly after circa 10 Ma (Subandean Zone). Early Oligocene plateau-wide tectonically driven exhumation suggests that subduction-related processes had already thermally weakened the continental lithosphere prior to the 27-25 Ma onset of volcanic activity.

  12. Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

    NARCIS (Netherlands)

    Sissingh, W.

    2008-01-01

    This paper integrates the sequence stratigraphic and tectonic data related to the Neogene geodynamic and palaeogeographic development of the African-Iberian plate boundary zone between Spain and Morocco. Though the dating of individual tectonostratigraphic sequences and their delimiting sequence

  13. Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

    NARCIS (Netherlands)

    Sissingh, W.

    2008-01-01

    This paper integrates the sequence stratigraphic and tectonic data related to the Neogene geodynamic and palaeogeographic development of the African-Iberian plate boundary zone between Spain and Morocco. Though the dating of individual tectonostratigraphic sequences and their delimiting sequence bou

  14. Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

    NARCIS (Netherlands)

    Sissingh, W.

    2008-01-01

    This paper integrates the sequence stratigraphic and tectonic data related to the Neogene geodynamic and palaeogeographic development of the African-Iberian plate boundary zone between Spain and Morocco. Though the dating of individual tectonostratigraphic sequences and their delimiting sequence bou

  15. Estratigrafía y facies volcánicas y volcaniclásticas de la Formación Valle del Cura: magmatismo paleógeno en la Cordillera Frontal de San Juan Stratigraphy and volcanic facies of the of the Valle del Cura Formation: Paleogene volcanism in the Frontal Cordillera of San Juan

    Directory of Open Access Journals (Sweden)

    V.D. Litvak

    2005-06-01

    del Cura Formation represent an important Eocene volcano-sedimentary episode composed of thick beds of tuff, coarse conglomerate, coarse to middle lithic sandstone, volcanic sandstone and scarce shale. The volcanic levels include rhyolitic lavas and high-grade ignimbrites that represent strongly welded and high-temperature pyroclastic flows. The formation also includes thick pyroclastic flow deposits composed of crystalline, lithic and/ or glassy tuff, lapilli tuff, and even coarse facies such as volcanic breccia and agglomerate. Volcanic epiclastic facies interbedded within the pyroclastic deposit represent the reworked primary pyroclastic material. These pyroclastic flow deposits show features that reflect the proximity of its eruptive centre, which might be located in the southern end of the cordillera de la Brea. The Valle del Cura Formation can be correlated with the equivalent units exposed farther north at Río de la Sal and Río Blanco (Macho Muerto and, chronologically, with the Bocatoma Unit intrusives that crop out to the west in Chile, emplaced along the Eocene magmatic front. By contrast, the Valle del Cura Formation represents intense volcanic activity developed in a back-arc setting.

  16. New isotopic ages and the timing of orogenic events in the Cordillera Darwin, southernmost Chilean Andes

    Science.gov (United States)

    Hervé, F.; Nelson, E.; Kawashita, K.; Suárez, M.

    1981-10-01

    The Cordillera Darwin, a structural culmination in the Andes of Tierra del Fuego, exposes an orogenic core zone that has undergone polyphase deformation and metamorphism. Some of the classic problems of orogenic zones have remained unanswered in the Cordillera Darwin: the age of deformed plutonic rocks, the distinction of structurally reactivated basement and metamorphosed cover rocks, and the timing of orogenic events. This study addresses and partially answers these questions. A well-constrained Rb-Sr isochron age of157±8m.y. and an initial 87Sr/ 86Sr ratio of 0.7087 obtained from a pre-tectonic granitic suite suggest a genetic relation between this suite and Upper Jurassic silicic volcanic rocks in the cover sequence (Tobifera Formation), and also suggest involvement of continental crust in formation of these magmas. A poorly constrained Rb-Sr isochron age of240±40m.y. obtained from supposed basement schists is consistent with field relations in the area which suggest a late Paleozoic/early Mesozoic metamorphism for these pre-Late Jurassic rocks. However, because of scatter in the data and the uncertainties involved in dating metasedimentary rocks, the significance of the isotopic age is dubious. Compilation of previously published ages in the area [9] with new mineral ages reported here indicate that "early Andean" orogenic events occurred between 100 and 84 m.y. ago, and that subduction-related magmatism has contributed, probably discontinuously, to the crustal evolution of the region throughout the Mesozoic.

  17. Ethno-botanical survey of edible wild fruits in Benguet, Cordillera administrative region, the Philippines.

    Science.gov (United States)

    Chua-Barcelo, Racquel Tan

    2014-05-01

    To conduct a survey on the common name/s, traditional uses and cultural importance of the edible wild fruits in different municipalities of Benguet, Cordillera administrative region. Interviews using questionnaires with barangay leaders and indigenous people were conducted with 176 key informants from June 2011 to July 2013. A total of 36 fruit species were found in different municipalities of Benguet. These fruit species belong to 27 genera and 20 families. Among the 13 municipalities of Benguet, Kibungan has the highest number of species. There are many uses of wild fruits which ranged from food (snack/dessert/table food), forage (especially for birds, monkeys and wild animals such as cloud rat and grass eaters), offertory, processed/preserved (as jam, jellies, candies, juice and wine), condiment or ingredient (for cooking), source of dye or ink, decoration (to garnish food) and as medicine to common ailments or health problems. Based on the inventory and calculated cultural importance index, Garcinia binucao (balokok) belonging to Clusiaceae is the most abundant fruit, hence it is the commonly used fruit for various purposes such as food, forage, processing/preservation and condiment/ingredient; Vaccinium myrtoides (ayusip) for offerings and as source of dye/ink; Saurauia elegans (uyok) for decoration, and, Antidesma bunius (bugnay) for medicine. Benguet province in the Cordillera region provides a diversity of edible wild fruits. The data gathered from the study signifies that collection, processing and utilization of edible wild fruits are still part of the daily activities of the people in Benguet.

  18. Subduction system and flat slab beneath the Eastern Cordillera of Colombia

    Science.gov (United States)

    Chiarabba, Claudio; De Gori, Pasquale; Faccenna, Claudio; Speranza, Fabio; Seccia, Danilo; Dionicio, Viviana; Prieto, Germán. A.

    2016-01-01

    Seismicity at the northern terminus of the Nazca subduction is diffused over a wide area containing the puzzling seismic feature known as the Bucaramanga nest. We relocate about 5000 earthquakes recorded by the Colombian national seismic network and produce the first 3-D velocity model of the area to define the geometry of the lithosphere subducting below the Colombian Andes. We found lateral velocity heterogeneities and an abrupt offset of the Wadati-Benioff zone at 5°N indicating that the Nazca plate is segmented by an E-W slab tear, that separates a steeper Nazca segment to the south from a flat subduction to the north. The flat Nazca slab extends eastward for about 400 km, before dip increases to ˜50° beneath the Eastern Cordillera, where it yields the Bucaramanga nest. We explain this puzzling locus of intermediate-depth seismicity located beneath the Eastern Cordillera of Colombia as due to a massive dehydration and eclogitization of a thickened oceanic crust. We relate the flat subducting geometry to the entrance at the trench at ca. 10 Ma of a thick - buoyant oceanic crust, likely a volcanic ridge, producing a high coupling with the overriding plate. Sub-horizontal plate subduction is consistent with the abrupt disappearance of volcanism in the Andes of South America at latitudes > 5°N.

  19. Un nuevo Eleutherodactylus (Anura, Leptodactylidae de la Cordillera de Mérida, Andes de Venezuela

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    Chacón-Ortiz, A.

    2004-06-01

    Full Text Available A new frog of the genus Eleutherodactylus is described from the Cordillera de Mérida, Venezuelan Andes. The species is distinguished from others by its moderate size, first finger equal or shorter than second, basal webbing on toes, and dominant colour immaculate brown or with a few spots. The species is compared with the groups unistrigatus and conspicillatus, but not assigned to either of them. A distribution map and a sonogram (of the song are presented. Comments about current knowledge of frogs of the genus Eleutherodactylus in Venezuela are provided.Se describe una nueva rana del género Eleutherodactylus de la Cordillera de Mérida, Andes de Venezuela. La especie se distingue del resto de congéneres por su tamaño moderado, primer dedo de la mano igual o más corto que el segundo, palmeadura pedal basal, y color dominante marrón uniforme o con pocas manchas. Se compara la especie con los grupos unistrigatus y conspicillatus, pero no se asigna a ninguno de ellos. Se presenta un mapa de distribución y un sonograma del canto. Se comenta brevemente sobre el conocimiento actual de las ranas del género Eleutherodactylus en Venezuela.

  20. Imaging Lithospheric-scale Structure Beneath Northern Altiplano in Southern Peru and Northern Bolivia

    Science.gov (United States)

    Kumar, A.; Wagner, L. S.; Beck, S. L.; Zandt, G.; Long, M. D.

    2014-12-01

    The northern Altiplano plateau of southern Peru and northern Bolivia is one of the highest topographic features on the Earth, flanked by Western and Eastern Cordillera along its margin. It has strongly influenced the local and far field lithospheric deformation since the early Miocene (Masek et al., 1994). Previous studies have emphasized the importance of both the crust and upper mantle in the evolution of Altiplano plateau (McQuarrie et al., 2005). Early tomographic and receiver function studies, south of 16° S, show significant variations in the crust and upper mantle properties in both perpendicular and along strike direction of the Altiplano plateau (Dorbath et. al., 1993; Myers et al., 1998; Beck and Zandt, 2002). In order to investigate the nature of subsurface lithospheric structure below the northern Altiplano, between 15-18° S, we have determined three-dimensional seismic tomography models for Vp and Vs using P and S-wave travel time data from two recently deployed local seismic networks of CAUGHT and PULSE. We also used data from 8 stations from the PERUSE network (PERU Subduction Experiment). Our preliminary tomographic models show a complex variation in the upper mantle velocity structure with depth, northwest and southeast of lake Titicaca. We see the following trend, at ~85 km depth, northwest of lake Titicaca: low Vp and Vs beneath the Western Cordillera, high Vs beneath the Altiplano and low Vp and Vs beneath the Eastern Cordillera. This low velocity anomaly, beneath Eastern Cordillera, seems to coincide with Kimsachata, a Holocene volcano in southern Peru. At depth greater than ~85 km: we find high velocity anomaly beneath the Western Cordillera and low Vs beneath the Altiplano. This high velocity anomaly, beneath Western Cordillera, coincides with the well-located Wadati-Benioff zone seismicity and perhaps represents the subducting Nazca slab. On the southeast of lake Titicaca, in northern Bolivia, we see a consistently high velocity anomaly

  1. Strong lateral strength contrasts in the mantle lithosphere of continents: A case study from the hot SW Canadian Cordillera

    NARCIS (Netherlands)

    Hardebol, N.J.; Beekman, F.; Cloetingh, S.A.P.L.

    2013-01-01

    This study aims at quantifying the 3-D variability in lithosphere strength of the south-eastern Canadian Cordillera and adjacent craton to the east. Strength is calculated in a forward manner, starting from rheological laws of brittle and ductile deformation. The work flow calculates a temperature m

  2. DNA Barcoding Survey of Anurans across the Eastern Cordillera of Colombia and the Impact of the Andes on Cryptic Diversity.

    Science.gov (United States)

    Guarnizo, Carlos E; Paz, Andrea; Muñoz-Ortiz, Astrid; Flechas, Sandra V; Méndez-Narváez, Javier; Crawford, Andrew J

    2015-01-01

    Colombia hosts the second highest amphibian species diversity on Earth, yet its fauna remains poorly studied, especially using molecular genetic techniques. We present the results of the first wide-scale DNA barcoding survey of anurans of Colombia, focusing on a transect across the Eastern Cordillera. We surveyed 10 sites between the Magdalena Valley to the west and the eastern foothills of the Eastern Cordillera, sequencing portions of the mitochondrial 16S ribosomal RNA and cytochrome oxidase subunit 1 (CO1) genes for 235 individuals from 52 nominal species. We applied two barcode algorithms, Automatic Barcode Gap Discovery and Refined Single Linkage Analysis, to estimate the number of clusters or "unconfirmed candidate species" supported by DNA barcode data. Our survey included ~7% of the anuran species known from Colombia. While barcoding algorithms differed slightly in the number of clusters identified, between three and ten nominal species may be obscuring candidate species (in some cases, more than one cryptic species per nominal species). Our data suggest that the high elevations of the Eastern Cordillera and the low elevations of the Chicamocha canyon acted as geographic barriers in at least seven nominal species, promoting strong genetic divergences between populations associated with the Eastern Cordillera.

  3. Glacial areas, lake areas, and snowlines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Directory of Open Access Journals (Sweden)

    M. N. Hanshaw

    2013-02-01

    Full Text Available Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far, yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975–2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 ± 1.70 km2 yr−1 (22-yr average, 1988–2010, with 95% confidence interval. The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 ± 0.18 km2 yr−1 since 1980 (31-yr average, 1980–2011, also with 95% confidence interval; Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000–2011 as compared to the preceding decade (1990–2000; Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61% of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84% of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 yr provide an important spatiotemporal assessment of climate

  4. Glacial areas, lake areas, and snowlines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, M. N.; Bookhagen, B.

    2013-02-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 ± 1.70 km2 yr-1 (22-yr average, 1988-2010, with 95% confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 ± 0.18 km2 yr-1 since 1980 (31-yr average, 1980-2011, also with 95% confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61% of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84% of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 yr provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further studies

  5. Glacial areas, lakes areas, and snowlines from 1975-2012: Status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, Maiana Natania

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: First, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 +/- 1.70 km2/yr (22-year average, 1988-2010, with 95 % confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 +/- 0.18 km2/yr since 1980 (31-year average, 1980-2011, also with 95 % confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61 % of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84 % of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 years provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further

  6. A Middle Miocene (13.5-12 Ma) deformational event constrained by volcanism along the Puna-Eastern Cordillera border, NW Argentina

    Science.gov (United States)

    Aramayo, Alejandro; Guzmán, Silvina; Hongn, Fernando; del Papa, Cecilia; Montero-López, Carolina; Sudo, Masafumi

    2017-04-01

    The features of Middle Miocene deposits in the Puna-Eastern Cordillera transition (Valles Calchaquíes) indicate that Cenozoic deformation, sedimentation and volcanism follow a complex spatiotemporal relationship. The intense volcanic activity recorded in the eastern Puna border between 14 and 11.5 Ma coincides with the occurrence of one of the most important deformation events of the Neogene tectonic evolution in the region. Studies performed across the Puna-Eastern Cordillera transition show different relationships between volcanic deposits of ca. 13.5-12.1 Ma and the Oligocene-Miocene Angastaco Formation. In this paper we describe the ash-flow tuff deposits which are the first of this type found concordant in the sedimentary fill of Valles Calchaquíes. Several analyses performed on these pyroclastic deposits allow a correlation to be made with the Alto de Las Lagunas Ignimbrite (ca. 13.5 Ma) of the Pucarilla-Cerro Tipillas Volcanic Complex located in the Puna. Outcrops of the ca. 13.5 Ma pyroclastic deposits are recognised within the Puna and the Valle Calchaquí. However, in the southern prolongation of the Valle de Hualfín (Tiopampa-Pucarilla depression) that separates the Puna from the Valle Calchaquí at these latitudes, these deposits are partially eroded and buried, and thus their occurrence is recorded only by abundant volcanic clasts included in conglomerates of the Angastaco Formation. The sedimentation of the Angastaco Formation was aborted at ca. 12 Ma in the Tiopampa-Pucarilla depression by the Pucarilla Ignimbrite, which unconformably covers the synorogenic units. On the contrary, in the Valle Calchaquí the sedimentation of the Angastaco Formation continued until the Late Miocene. The different relationships between the Miocene Angastaco Formation and the ignimbrites with ages of ca. 13.5 and ca. 12 Ma reveal that in this short period ( 1.5 m.y.) a significant deformation event took place and resulted in marked palaeogeographic changes, as

  7. Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, M. N.; Bookhagen, B.

    2014-03-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. Additionally, we have estimated the snow-line altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota (1988 glacial area: 361 km2) have been declining at a rate of 3.99 ± 1.15 km2 yr-1 (22 year average, 1988-2010, with 95% confidence interval (CI), n = 8 images). Since 1980, the Quelccaya Ice Cap (1980 glacial area: 63.1 km2) has been declining at a rate of 0.57 ± 0.10 km2 yr-1 (30 year average, 1980-2010, with 95% CI, n = 14). Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2010) as compared to the preceding decade (1988-1999) with an average increase from 37.5 to 42.3 × 10-3 km2 yr-1 km-2 (13%). Third, glaciers with lower median elevations are declining at higher rates than those with higher median elevations. Specifically, glaciers with median elevations around 5200 m a.s.l. are retreating to higher elevations at a rate of ~1 m yr-1 faster than glaciers with median elevations around 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% of lakes connected to glacial watersheds have either remained stable or shown a roughly synchronous increase in lake area, while 42% of lakes not connected to glacial

  8. Fajas oblicuas de deformación neotectónica en Precordillera y Cordillera Frontal (31° 30´ - 33° 30´ LS: controles paleotectónicos Oblique belts of neotectonic deformation in Precordillera and Frontal Cordillera (31 30´ - 33 30´ ls: Paleotectonic controls

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    J.M. Cortés

    2006-12-01

    Full Text Available La Precordillera Sur y las Cerrilladas Pedemontanas de Mendoza, son dos unidades morfotectónicas principales en la vertiente oriental de los Andes centrales, a los 31º30' - 33º30' de latitud sur. Allí, dos cinturones de deformación transpresiva y orientación noroeste, denominados fajas Barreal-Las Peñas y Río Mendoza-Tupungato, se desarrollaron como consecuencia de la gradual somerización de la placa de Nazca en los últimos 20 Ma. Su orientación y compleja geometría estructural resulta de la interferencia de la deformación andina tardío-cenozoica con la estructura de orientación noroeste del rift triásico de la cuenca Cuyana y antiguas zonas de sutura colisional de edad paleozoica. Este trabajo demuestra que los rasgos paleotectónicos del substrato triásico-paleozoico de la Precordillera Sur y del margen oriental de la Cordillera Frontal controlan la configuración morfotectónica y la distribución y reactivación de gran parte de la estructura neotectónica del margen andino a estas latitudes.The Southern Precordillera and Cerrilladas Pedemontanas of Mendoza, Argentina, are two major morphotectonic units in the eastern side of the Central Andes at 31º30' - 33º30' South latitude. There, two regional NW striking structures, called the Barreal - Las Peñas and Río Mendoza - Tupungato belts were developed as a consequence of gradual flattening of the Nazca plate in the last 20 M.yrs. Their orientation and complex structural geometry result from the interference of the Late Cenozoic Andean deformation with the NW-trending rift structure of the Triassic Cuyo basin and ancient collisional suture zones of Paleozoic age. This work demonstrates that paleotectonics features in the Triassic-Paleozoic substratum of the Southern Precordillera and the eastern margin of the Cordillera Frontal control the morphotectonic configuration and neotectonic structural distribution and rejuvenation of the Andes at these latitudes.

  9. Lake records of Northern Hemisphere South American summer monsoon variability from the Cordillera Oriental, Colombia: Initial results from Lago de Tota and Laguna de Ubaque

    Science.gov (United States)

    Escobar, J.; Rudloff, O.; Bird, B. W.

    2013-12-01

    The lack of terrestrial paleoclimate records from the Northern Hemisphere Andes with decadal resolution has meant that our understanding of abrupt South American summer monsoon (SASM) variability during the Holocene is almost exclusively based on data from Southern Hemisphere sites. In order to develop a more integrated and complete picture of the SASM as a system and its response during rapid climate changes, high-resolution paleoclimate records are needed from the Northern Hemisphere Andes. We present initial results from analysis of lake sediment cores that were collected from Lago de Tota (N 5.554, W 72.916) and Laguna de Ubaque (N 4.500, W 73.935) in the Eastern Cordillera of the Colombian Andes. These sediment cores were collected in July 2013 as part on an ongoing paleoclimate research initiative in Colombia. Located in the Boyacá Provence, Lago de Tota is the largest high-altitude lake (3010 masl) in the Northern Hemisphere Andes and the second largest Andean lake in South America. As such, hydrologic changes recorded in the lake's sediment record reflect regional climate responses. Lago de Ubaque (2070 masl) is a small east facing moraine-dammed lake near the capital of Bogotá that contains finely laminated clastic sediments. The initial sedimentological and chronological results demonstrate that Lago de Tota and Laguna de Ubaque have excellent potential for resolving Northern Hemisphere SASM variability at decadal time scales or better. Such records will provide important counterparts to high-resolution paleoclimate records from the Southern Hemisphere Andes.

  10. La Cordillera de los Andes: presentación de los problemas geomorfológicos

    Directory of Open Access Journals (Sweden)

    1974-01-01

    érites sont souvent déblayées sur les pentes fortes par le ruissellement et les divers glissements et éboulements. El alzamiento en bóveda del Ponto-plioceno ha dado a los .Andes su volumen montañoso actual y ha llevado a más de 4000 m superficies de erosión elaboradas durante e! Terciario. Estas superficies o 'puna' son muy probablemente poligénicas y policíclicas. Están dominadas por grandes cordilleras que son generalmente horsts que delimitan los sectores de surrección máxima, horsts que son posteriores a la elaboración de la superficie de las mesetas. Esta superficie está deformada tanto sobre los bordes de las cuencas interiores como sobre los flancos de la montaña donde ella ha sido disectada y reducida a bandas. Algunas veces esta superficie ha podido desaparecer debido a su recorte en lo alto de los flancos de los grandes valles, sobretodo en los dos extremos de la cadena. A un nivel inferior, se desarrollaron aplanamientos menores durante el Plioceno y posiblemente durante el Cuaternario antiguo, en sectores que habían permanecido relativamente estables: son los 'glacis' de erosión en lazos del altiplano perú-boliviano o las superficies de abrasión retocadas en 'glacis' sobre los abombamientos costeros perú-chilenos. Algunos grandes valles están adaptados a las grandes direcciones estructurales consecutivas a los movimientos del fin de Terciario (la adaptación del conjunto va acompañada a menudo de numerosas inadaptaciones locales. Otros valles siguen antiguas direcciones estructurales, anteriores al alzamiento andino. El Cuaternario está marcado por una serie de períodos fríos acompañados de glaciaciones en la montaña. Se ha podido determinar lar existencia de cuatro glaciaciones distintas de las cuales una al menos remonta al Cuaternario antiguo. Las glaciaciones recientes son contemporáneas de las glaciaciones del Cuaternario reciente de Europa y de América del Norte. Sus causas hay que buscarlas, para las latitudes medias, en un

  11. Geochronology, geochemistry and tectonic evolution of the Western and Central cordilleras of Colombia

    Science.gov (United States)

    Villagómez, Diego; Spikings, Richard; Magna, Tomas; Kammer, Andreas; Winkler, Wilfried; Beltrán, Alejandro

    2011-08-01

    Autochthonous rocks of the pre-Cretaceous continental margin of NW South America (the Tahami Terrane) are juxtaposed against a series of para-autochthonous rock units that assembled during the Early Cretaceous. Allochthonous, oceanic crust of the Caribbean Large Igneous Province collided with and accreted onto the margin during the Late Cretaceous. We present the first regional-scale dataset of zircon U-Pb LA-ICP-MS ages for intrusive and metamorphic rocks of the autochthonous Tahami Terrane, Early Cretaceous igneous para-autochthonous rocks and accreted oceanic crust. The U-Pb zircon data are complemented by multiphase 40Ar/ 39Ar crystallization and cooling ages. The geochronological data are combined with whole rock major oxide, trace element and REE data acquired from the same units to constrain the tectonic origin of the rock units and terranes exposed in the Western Cordillera, Cauca-Patía Valley and the Central Cordillera of Colombia. The Tahami Terrane includes lower Paleozoic orthogneisses (~ 440 Ma) that may have erupted during the active margin stage of the Rheic Ocean. Basement gneisses were intruded by Permian, continental arc granites during the final assembly of Pangea. Triassic sedimentary rocks were subsequently deposited in rift basins and partially melted during high-T metamorphism associated with rifting of western Pangea during 240-220 Ma. Continental arc magmatism during 180-145 Ma is preserved along the whole length of the Central Cordillera and was followed by an Early Cretaceous out-board step of the arc axis and the inception of the Quebradagrande Arc that fringed the continental margin. Back-stepping of the arc axis may have been caused by the collision of buoyant seamounts, which were coeval with plateau rocks exposed in the Nicoya Peninsular of Costa Rica. Rapid westward drift of South America closed the Quebradagrande basin in the late Aptian and caused medium-high P-T metamorphic rocks of the Arquía Complex to exhume and obduct onto

  12. Remains of early Ordovician mantle-derived magmatism in the Santander Massif (Colombian Eastern Cordillera)

    Science.gov (United States)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Cottle, John M.; Hart, Craig J. R.

    2012-10-01

    An Early Ordovician magmatic event has been documented in the Santander Massif (north-Eastern Cordillera, Colombia). Three U/Pb laser ablation ages of 477 ± 2 Ma (Arenig), were obtained from metamorphosed and foliated calc-alkaline diorites. The 176Hf/177Hf values in zircons from these meta-diorites, yielded epsilon Hf values (ɛHft) > 0 (Mean = 2 ± 1, at 477 Ma). These data allow interpretation of the origin of these zircons from a radiogenic initial Hf isotope source, which is characteristic of the Earth's mantle. This, together with the fact that the rocks have been affected subsequently by tectonometamorphic processes, suggests that the early Ordovician diorites have been emplaced in a supra-subduction tectonic setting, related to onset of the Iapetus Ocean closure.

  13. Graptolitos ordovícicos en el Sur de la Cordillera frontal de Mendoza

    Directory of Open Access Journals (Sweden)

    Hugo Tickyj

    2009-04-01

    Full Text Available En el flanco sudoriental de la Cordillera Frontal mendocina aflora un conjunto plegado de metasedimentitas conocido como Formación Las Lagunitas, cuyos afloramientos se extienden entre los ríos Diamante por el sur y Tunuyán por el norte, alcanzando un ancho máximo de 15 km a la latitud del volcán Maipo. El perfil estudiado en el arroyo Cortaderas (34º23'S está compuesto por una secuencia silicoclástica marina integrada por tres conjuntos litológicos, que de este a oeste son: a areniscas gruesas a medias, bien seleccionadas, y areniscas conglomerádicas, b vaques de grano grueso a fino y c areniscas finas a medias, con intercalaciones de pelitas negras laminadas. En la última unidad fueron colectados graptolitos en regular estado de preservación. Su estudio sistemático permitió definir una asociación correspondiente a la Biozona de Climacograptus bicornis, por lo que la Formación Las Lagunitas es asignada al Ordovícico Superior (Sandbiano o Caradociano. La completa extensión cronoestratigráfica de la Formación Las Lagunitas no ha sido establecida, debido a que en el perfil estudiado no es clara la relación entre la unidad portadora de graptolitos y el resto de la secuencia. Este registro de graptolitos en el sur de la Cordillera Frontal mendocina constituye un aspecto novedoso para el análisis del Ordovícico, con implicancias en el contexto de la evolución tectónica de las cuencas sedimentarias ordovícicas del oeste argentino.Outcrops of a folded sedimentary unit known as the Las Lagunitas Formation lie along the southeastern part of the Frontal Cordillera of Mendoza Province. The main exposures of the unit lie between the Diamante River in the south and Tunuyán in the north, reaching 15 km wide at the latitude of the Maipo volcano. At the Cortaderas Creek (34º23'S the studied section is a marine siliciclastic sequence comprising three lithological units: a well-sorted, coarse- to medium-grained sandstones and

  14. Holocene Paleoglacier History of Glaciar Dalla Vedova, Cordillera DARWIN, Tierra del Fuego, Chile

    Science.gov (United States)

    Reynhout, S.

    2015-12-01

    Southernmost South America is unique in its position immediately north of the present-day Antarctic Convergence, making it ideally suited for the evaluation of Antarctic influences on terrestrial paleoclimate. Here we present a glacial geomorphic interpretation of the paleoglacial history of Glaciar Dalla Vedova in Bahía Blanca, Cordillera Darwin, Chile (53°S). This interpretation is further constrained by radiocarbon dating, cosmogenic dating, dendrochronology, and historical photogrammetry. Preliminary field work suggests that Holocene glacier fluctuations have been constrained to within 3 km of the present glacier boundary, punctuated by rapid recent glacier retreat over the past century. By comparing the observed chronology with the record contained further north in Patagonia, we will evaluate possible mechanisms of regional climate variability over the Holocene across southernmost South America.

  15. Precambrian crust beneath the Mesozoic northern Canadian Cordillera discovered by Lithoprobe seismic reflection profiling

    Science.gov (United States)

    Cook, Frederick A.; Clowes, Ronald M.; Snyder, David B.; van der Velden, Arie J.; Hall, Kevin W.; Erdmer, Philippe; Evenchick, Carol A.

    2004-04-01

    The Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike. They are interpreted as stratified Proterozoic rocks, including ˜1.8-0.7 Ga supracrustal rocks and their basement. The layering was discovered on two new deep seismic reflection profiles in the Yukon (Line 3; ˜650 km) and northern British Columbia (Line 2; ˜1245 km in two segments) that were acquired as part of the Lithoprobe Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) transect. In the Mackenzie Mountains of the eastern Yukon, the layering in Line 3 is visible between 5.0 and 12.0 s (˜15 to 36 km depth). It is followed southwestward for nearly 650 km (˜500 km across strike) and thins to less than 1.0 s (˜3.0-3.5 km thickness) near the Moho at the Yukon-Alaska international boundary. In the northern Rocky Mountains of British Columbia, the upper part of the layering on Line 2 correlates with outcrops of Proterozoic (1.76-1.0 Ga) strata in the Muskwa anticlinorium. At this location, the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for ˜700 km (˜300 km across strike). It disappears as a thin taper at the base of the crust ˜150 km east of the coast of the Alaskan panhandle. The only significant disruption in the layering occurs at the Tintina fault zone, a late to postorogenic strike-slip fault with up to 800 km of displacement, which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles (˜300 km apart). The base of the layered reflection zone coincides with the Moho, which exhibits variable character and undulates in a series of broad arches with widths of ˜150 km. In general, the mantle appears to have few reflections. However, at the southwest end of Line 3 near the Alaska

  16. The Unusual Nature of Recent Snowpack Declines in the North American Cordillera

    Science.gov (United States)

    Pederson, Gregory T.; Gray, Stephen T.; Woodhouse, Connie A.; Betancourt, Julio L.; Fagre, Daniel B.; Littell, Jeremy S.; Watson, Emma; Luckman, Brian H.; Graumlich, Lisa J.

    2011-07-01

    In western North America, snowpack has declined in recent decades, and further losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff-generating areas of the Colorado, Columbia, and Missouri River drainages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

  17. The magmatic history of the Vetas-California mining district, Santander Massif, Eastern Cordillera, Colombia

    Science.gov (United States)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Valencia, Víctor; Hart, Craig J. R.

    2013-08-01

    The Vetas-California Mining District (VCMD), located in the central part of the Santander Massif (Colombian Eastern Cordillera), based on U-Pb dating of zircons, records the following principal tectono-magmatic events: (1) the Grenville Orogenic event and high grade metamorphism and migmatitization between ˜1240 and 957 Ma; (2) early Ordovician calc-alkalic magmatism, which was synchronous with the Caparonensis-Famatinian Orogeny (˜477 Ma); (3) middle to late Ordovician post-collisional calc-alkalic magmatism (˜466-436 Ma); (4) late Triassic to early Jurassic magmatism between ˜204 and 196 Ma, characterized by both S- and I-type calc-alkalic intrusions and; (5) a late Miocene shallowly emplaced intermediate calc-alkaline intrusions (10.9 ± 0.2 and 8.4 ± 0.2 Ma). The presence of even younger igneous rocks is possible, given the widespread magmatic-hydrothermal alteration affecting all rock units in the area. The igneous rocks from the late Triassic-early Jurassic magmatic episodes are the volumetrically most important igneous rocks in the study area and in the Colombian Eastern Cordillera. They can be divided into three groups based on their field relationships, whole rock geochemistry and geochronology. These are early leucogranites herein termed Alaskites-I (204-199 Ma), Intermediate rocks (199-198 Ma), and late leucogranites, herein referred to as Alaskites-II (198-196 Ma). This Mesozoic magmatism is reflecting subtle changes in the crustal stress in a setting above an oblique subduction of the Panthalassa plate beneath Pangea. The lower Cretaceous siliciclastic Tambor Formation has detrital zircons of the same age populations as the metamorphic and igneous rocks present in the study area, suggesting that the provenance is related to the erosion of these local rocks during the late Jurassic or early Cretaceous, implying a local supply of sediments to the local depositional basins.

  18. Timing and Style of Deformation in the Floresta Massif, Axial Eastern Cordillera, Colombia

    Science.gov (United States)

    Saylor, J.; Stockli, D. F.; Mora, A.

    2009-12-01

    The Floresta Massif is one of the largest exposures of Paleozoic and Pre-Cambrian rocks in the Eastern Cordillera. Estimates for the age of onset of shortening-related deformation in the Eastern Cordillera range from late Cretaceous to late Miocene (e.g., Hoorn et al., 1995; Bayona et al., 2008; Parra et al., 2009). The massif is typically interpreted as being exhumed along a high-angle reverse fault (the Soapaga fault) that reactivated Mesozoic extensional structures (e.g., Kammer and Sanchez, 2006). We examined these dual linked issued with new zircon U/Th-He (ZHe) data, new geological mapping and previously published apatite fission track (AFT) data from the Floresta Massif and the associated footwall strata. Previously, an overturned Paleozoic - Cretaceous sequence was mapped emplaced on Tertiary strata along the Soapaga fault. However, new geologic mapping identifies two previously unrecognized thrusts which place, from west to east, Paleozoic strata on Jurassic strata (Fault 3), Jurassic strata on Cretaceous strata (Fault 2) and Cretaceous strata on Tertiary strata (along the previously identified Fault 1). These results are confirmed by AFT and ZHe data. ZHe ages show no resetting in the Tertiary footwall strata, but show partial resetting in the Cretaceous strata and full resetting in the Jurassic and Paleozoic strata. Similarly, AFT data show older ages in the Cretaceous strata than in the Jurassic or Paleozoic strata. Fully reset ZHe ages from Jurassic strata show that exhumation of the Floresta Massif was ongoing by at least the early Oligocene (~ 30 Ma). However, this deformation post-dates an older episode of deformation associated with partially reset ZHe ages in the Cretaceous strata. Based on a decrease in lag time in detrital ZHe data, we infer that the earlier episode of deformation occurred in the mid - late Eocene (45 - 35 Ma).

  19. Growth and gravitational collapse of a mountain front of the Eastern Cordillera of Colombia

    Science.gov (United States)

    Kammer, Andreas; Montana, Jorge; Piraquive, Alejandro

    2016-04-01

    The Eastern Cordillera of Colombia is bracketed between the moderately east-dipping flank of the Central Cordillera on its western and the gently bent Guayana shield on its eastern side. It evolved as a response to a considerable displacement transfer from the Nazca to the Southamerican plate since the Oligocene break-up of the Farallon plate. One of its distinctive traits refers to its significant shortening by penetrative strain at lower and folding at higher structural levels, approximating a wholesale pure-shear in analogy to a vice model or a crustal welt sandwiched between rigid buttresses. This contrasting behavior may be explained by the spatial coincidence between Neogene mountain belt and a forebulge that shaped the foreland trough during a Cretaceous subduction cycle and was very effective in localizing a weakening of the backarc region comprised between two basin margin faults. In this paper we examine a two-phase evolution of the Eastern mountain front. Up to the late Miocene deformation was restrained by the inherited eastern basin margin fault and as the cordilleran crust extruded, a deformation front with an amplitude similar the present structural relief of up to 10.000 m may have built up. In the Pliocene convergence changed from a roughly strike-perpendicular to an oblique E-W direction and caused N-S trending faults to branch off from the deformation front. This shortening was partly driven by a gravitational collapse of the Miocene deformation front, that became fragmented by normal faults and extruded E on newly formed Pliocene thrust faults. Normal faults display displacements of up to 3000 m and channelized hydrothermal fluids, leading to the formation of widely distributed fault breccias and giving rise to a prolific Emerald mineralization. In terms of wedge dynamics, the Pliocene breaching of the early formed deformation front helped to establish a critical taper.

  20. Ethno-botanical survey of edible wild fruits in Benguet, Cordillera administrative region, the Philippines

    Science.gov (United States)

    Chua-Barcelo, Racquel Tan

    2014-01-01

    Objective To conduct a survey on the common name/s, traditional uses and cultural importance of the edible wild fruits in different municipalities of Benguet, Cordillera administrative region. Methods Interviews using questionnaires with barangay leaders and indigenous people were conducted with 176 key informants from June 2011 to July 2013. Results A total of 36 fruit species were found in different municipalities of Benguet. These fruit species belong to 27 genera and 20 families. Among the 13 municipalities of Benguet, Kibungan has the highest number of species. There are many uses of wild fruits which ranged from food (snack/dessert/table food), forage (especially for birds, monkeys and wild animals such as cloud rat and grass eaters), offertory, processed/preserved (as jam, jellies, candies, juice and wine), condiment or ingredient (for cooking), source of dye or ink, decoration (to garnish food) and as medicine to common ailments or health problems. Based on the inventory and calculated cultural importance index, Garcinia binucao (balokok) belonging to Clusiaceae is the most abundant fruit, hence it is the commonly used fruit for various purposes such as food, forage, processing/preservation and condiment/ingredient; Vaccinium myrtoides (ayusip) for offerings and as source of dye/ink; Saurauia elegans (uyok) for decoration, and, Antidesma bunius (bugnay) for medicine. Conclusions Benguet province in the Cordillera region provides a diversity of edible wild fruits. The data gathered from the study signifies that collection, processing and utilization of edible wild fruits are still part of the daily activities of the people in Benguet. PMID:25183144

  1. Ethno-botanical survey of edible wild fruits in Benguet, Cordillera administrative region, the Philippines

    Institute of Scientific and Technical Information of China (English)

    Racquel Tan Chua-Barcelo

    2014-01-01

    Objective: To conduct a survey on the common name/s, traditional uses and cultural importance of the edible wild fruits in different municipalities of Benguet, Cordillera administrative region. Methods: Interviews using questionnaires with barangay leaders and indigenous people were conducted with 176 key informants from June 2011 to July 2013. Results: A total of 36 fruit species were found in different municipalities of Benguet. These fruit species belong to 27 genera and 20 families. Among the 13 municipalities of Benguet, Kibungan has the highest number of species. There are many uses of wild fruits which ranged from food (snack/dessert/table food), forage (especially for birds, monkeys and wild animals such as cloud rat and grass eaters), offertory, processed/preserved (as jam, jellies, candies, juice and wine), condiment or ingredient (for cooking), source of dye or ink, decoration (to garnish food) and as medicine to common ailments or health problems. Based on the inventory and calculated cultural importance index, Garcinia binucao (balokok) belonging to Clusiaceae is the most abundant fruit, hence it is the commonly used fruit for various purposes such as food, forage, processing/preservation and condiment/ingredient; Vaccinium myrtoides (ayusip) for offerings and as source of dye/ink; Saurauia elegans (uyok) for decoration, and, Antidesma bunius (bugnay) for medicine. Conclusions: Benguet province in the Cordillera region provides a diversity of edible wild fruits. The data gathered from the study signifies that collection, processing and utilization of edible wild fruits are still part of the daily activities of the people in Benguet.

  2. Graptolitos ordovícicos en el Sur de la Cordillera frontal de Mendoza

    Directory of Open Access Journals (Sweden)

    Hugo Tickyj

    2009-04-01

    Full Text Available En el flanco sudoriental de la Cordillera Frontal mendocina aflora un conjunto plegado de metasedimentitas conocido como Formación Las Lagunitas, cuyos afloramientos se extienden entre los ríos Diamante por el sur y Tunuyán por el norte, alcanzando un ancho máximo de 15 km a la latitud del volcán Maipo. El perfil estudiado en el arroyo Cortaderas (34º23'S está compuesto por una secuencia silicoclástica marina integrada por tres conjuntos litológicos, que de este a oeste son: a areniscas gruesas a medias, bien seleccionadas, y areniscas conglomerádicas, b vaques de grano grueso a fino y c areniscas finas a medias, con intercalaciones de pelitas negras laminadas. En la última unidad fueron colectados graptolitos en regular estado de preservación. Su estudio sistemático permitió definir una asociación correspondiente a la Biozona de Climacograptus bicornis, por lo que la Formación Las Lagunitas es asignada al Ordovícico Superior (Sandbiano o Caradociano. La completa extensión cronoestratigráfica de la Formación Las Lagunitas no ha sido establecida, debido a que en el perfil estudiado no es clara la relación entre la unidad portadora de graptolitos y el resto de la secuencia. Este registro de graptolitos en el sur de la Cordillera Frontal mendocina constituye un aspecto novedoso para el análisis del Ordovícico, con implicancias en el contexto de la evolución tectónica de las cuencas sedimentarias ordovícicas del oeste argentino.

  3. K-Ar geochronology of the late cenozoic volcanic rocks of the Cordillera Occidental, southernmost Peru

    Science.gov (United States)

    Tosdal, Richard M.; Farrar, Edward; Clark, Alan H.

    1981-05-01

    Twenty-four K-Ar radiometric ages are presented for late Cenozoic continental volcanic rocks of the Cordillera Occidental of southernmost Perú (lat. 16° 57'-17° 36'S). Rhyodacitic ignimbrite eruptions began in this transect during the Late Oligocene and continued episodically through the Miocene. The development of andesitic-dacitic strato volcanoes was initiated in the Pliocene and continues to the present. The earliest ignimbrite flows (25.3-22.7 Ma) are intercalated in the upper, coarsely-elastic member of the Moquegua Formation and demonstrate that this sedimentary unit accumulated in a trough, parallel to Andean tectonic trends, largely in the Oligocene. More voluminous ash-flow eruptions prevailed in the Early Miocene (22.8-17.6 Ma) and formed the extensively preserved Huaylillas Formation. This episode was coeval with a major phase of Andean uplift, and the pyroclastics overlie an erosional surface of regional extent incised into a Paleogene volcano-plutonic arc terrain. An age span of 14.2-8.9 Ma (mid-Late Miocene) is indicated for the younger Chuntacala Formation, which again comprises felsic ignimbrite flows, largely restricted to valleys incised into the pre-Huaylillas Formation lithologies, and, at lower altitudes, an extensive aggradational elastic facies. The youngest areally extensive ignimbrites, constituting the Sencca Formation, were extruded during the Late Miocene. In the earliest Pliocene, the ignimbrites were succeeded by more voluminous calcalkaline, intermediate flows which generated numerous large and small stratovolcanoes; these range in age from 5.3 to 1.6 Ma. Present-day, or Holocene, volcanism is restricted to several large stratovolcanoes which had begun their development during the Pleistocene (by 0.7 Ma). The late Oligocene/Early Miocene (ca. 22-23 Ma) reactivation of the volcanic arc coincided with a comparable increase in magmatic activity throughout much of the Cordilleras Occidental and Oriental of the Central Andes.

  4. Crustal shortening and Eocene extension in the southeastern Canadian Cordillera: Some thermal and rheological considerations

    Science.gov (United States)

    Liu, Mian; Furlong, Kevin P.

    1993-06-01

    Metamorphic core complexes in the southeastern Canadian Cordillera were formed during Eocene crustal extension, shortly (within a few millions of years) after Late Jurassic-Paleocene crustal shortening. Thermal-rheological modeling, constrained by geological and geochronological studies of the Valhalla core complex and other core complexes in this region, is used to investigate two major problems concerning the formation of these core complexes: (1) the dynamic links between crustal shortening and extension and (2) the cooling history and unroofing rates during extension. Thermal-rheological effects associated with crustal shortening are integrated through the history of crustal compression, since crustal shortening in this region was a long and slow process and cannot be treated as an instantaneous event. Our results suggest that crustal shortening may have played an important role in Eocene extension in the southeastern Canadian Cordillera by (1) producing a thickened and therefore unstable crust and (2) thermally weakening the lithosphere. However, heat generated by crustal shortening is not enough to account for the thermal state of the Valhalla complex, and additional heat sources at depth may be necessary. We then investigate thermal evolution during extension in both a simple shear model and a progressive pure stretching model. We show that the geotherm in an extensional region is time-and space-dependent and is affected by many variables including the preextensional thermal history and the mode of extension. Thus caution needs to be exercised when inferring unroofing rates from thermochronologic data. The cooling history of the Valhalla core complex may be explained by unroofing at rates of 1-2 mm/yr.

  5. Measurements of light absorbing particulates on the glaciers in the Cordillera Blanca, Peru

    Directory of Open Access Journals (Sweden)

    C. G. Schmitt

    2014-10-01

    Full Text Available Glaciers in the tropical Andes have been rapidly losing mass since the 1970s. In addition to the documented increase in air temperature, increases in light absorbing particulates deposited on glaciers could be contributing to the observed glacier loss. Here we report on measurements of light absorbing particulates sampled from glaciers during three surveys in the Cordillera Blanca in Peru. During three research expeditions in the dry seasons (May–August of 2011, 2012 and 2013, two hundred and forty snow samples were collected from fifteen mountain peaks over altitudes ranging from 4800 to nearly 6800 m. Several mountains were sampled each of the three expeditions and some mountains were sampled multiple times during the same expedition. Collected snow samples were melted and filtered in the field then later analyzed using the Light Absorption Heating Method (LAHM, a new technique that measures the ability of particulates on filters to absorb visible light. LAHM results have been calibrated using filters with known amounts of fullerene soot, a common industrial surrogate for black carbon (BC. As sample filters often contain dust in addition to BC, results are presented in terms of effective Black Carbon (eBC. During the 2013 survey, snow samples were collected and kept frozen for analysis with a Single Particle Soot Photometer (SP2. Calculated eBC mass from the filter analysis and the SP2 refractory Black Carbon (rBC results were well correlated (r2 = 0.92. These results indicate that a substantial portion of the light absorbing particulates in the more polluted areas were likely BC. The three years of data show that glaciers in the Cordillera Blanca Mountains close to human population centers have substantially higher levels of eBC (as high as 70 ng g−1 than remote glaciers (as low as 2.0 ng g−1 eBC, indicating that population centers can influence local glaciers by sourcing BC.

  6. Functional subtypes of renal α1-adrenoceptor in diabetic and non-dia-betic 2K1C Goldblatt renovascular hypertension

    Institute of Scientific and Technical Information of China (English)

    A ARMENIA; Munavvar Abdul SATTAR; Nor Azizan ABDULLAH; Md Abdul Hye KHAN; Edward James JOHNS

    2008-01-01

    Aim: This study investigates the subtypes of the α-adrenoceptor mediating the adrenergically-induced renal vasoconstrictor responses in streptozotocin-induced diabetic and non-diabetic 2-kidney one clip (2K1C) Goldblatt hypertensive rats. Methods: The renal blood flow responses to renal nerve stimulation, noradrenaline, phenylephrine, and methoxamine were measured in the absence and presence of nitrendipine, 5-methylurapidil, chloroethylclonidine and BMY 7378. Results: The renal vasoconstrictor responses were markedly attenuated by nitrendipine and 5-methylurapidil in the diabetic rats (all P<0.05). In the non-diabetic rats, these responses were markedly attenuated by nitrendipine, 5-methylurapidil, and BMY 7378 (all P<0.05). In both experimental groups, chloroethylclonidine markedly accentuated the renal vasoconstrictions caused by all the adrenergic stimuli (all P<0.05). Conclusion: These observations indicate that α1A-adrenoceptor subtypes play a major role in mediating adrenergically-induced renal vasoconstriction in the dia-betic 2K1C Goldblatt hypertensive rats. In the non-diabetic 2KIC Goldblatt hy-pertensive rats, contributions of α1A and α1D-adrenoceptor subtypes were proposed. Apart from post-synaptic α1-adrenoceptors, both in the diabetic and non-diabetic 2K1C Goldblatt hypertensive rats, the potential involvement of presynaptic α1-adrenoceptors is also suggested.

  7. Petrografia y geoquimica de las rocas intrusivas aflorantes entre los municipios de Mistrato y Belen de Umbria (Departamento de Risaralda, Cordillera Occidental Colombiana)

    National Research Council Canada - National Science Library

    Vallejo Hincapie, Diego Felipe; Salazar Rios, Andres Felipe; Toro Toro, Luz Mary

    2011-01-01

    Las rocas Intrusivas objeto de estudio afloran en los municipios de Mistrato y Belen de Umbria, Departamento de Risaralda, sobre el flanco oriental de la Cordillera Occidental y al oeste del Sistema...

  8. A new species of broad-headed eleutherodactylus from the cordillera occidental of Colombia (Amphibia, Leptodactylidae A new species of Broad-Headed Eleutherodactylus from the Cordillera Occidental of Colombia (Amphibia, Leptodactylidae

    Directory of Open Access Journals (Sweden)

    Lynch John D.

    1986-12-01

    Full Text Available The broad-headed eleutherodactyline frogs have been studied by Lynch(1975, 1981. Although frogs of this assembly are easily identified (Lynch,1975, 1976, 1981, the assembly is not a natural group (Lynch, 1986.Recently, Rivero (1984 described a new species, E. sernai, from westernAntioquia, Colombia. Although Rivero associated E. sernai with thebiporcatus group, the species appears to be a member of the sulcatus group(because it possesses the plesiornorphic condition of the mandibular musclesadductors and the trigeminal nerve mandibular ramus. However, this characteristicis not sufficient to place E. sernai within the sulcatus group; theassignment will be defended in a future paper on the osteology of the variousspecies of the group. For the moment, the sulcatus group contains thefollowing species: E. cerasies Lynch, E. cornutus (Jimenez de la Espada,E. helonotus (Lynch, E. ingeri (Cochran and Gain, E. ruizi Lynch, E.sernai Rivero, and E. sulcatus Se describe Eleutherodactylus cadenai sp. nov. de las selvas de la vertiente occidental de la Cordillera Occidental de Colombia (corregimiento .de Murrí, Municipio de Frontino, Antioquia.  La especie parece tener un ancestro común con Eleutherodactylus ingeri de los bosques nublados de la Cordillera Oriental de Colombia y las dos tienen parentescos con Eleutherodactylus ruizi de las cordilleras Central y Occidental de Colombia.

  9. Three new species of Pristimantis (Lissamphibia, Anura from montane forests of the Cordillera Yanachaga in Central Peru

    Directory of Open Access Journals (Sweden)

    William E. Duellman

    2007-12-01

    Full Text Available We describe three additional new species of Pristimantis from the Cordillera Yanachaga, a part of the Andes in central Peru. Analyses of DNA sequences of the mitochondrial rRNA genes show that onespecies is a close relative of P. bipunctatus (P. conspicillatus Group, another is a close relative of P. stictogaster (P. peruvianus Group, and the third is related to several species in the P. unistrigatus Group. The first two species are morphologically similar to their closest relatives but occur at lower elevations. Twenty-nine species of Pristimantis and Phrynopus are known from the vicinity of the Cordillera Yanachaga. The number of species, especially of Pristimantis, is high in the humid montane forestin comparison with other sites in humid montane forests in Peru, but the number is lower than on the western slopes of the Andes in Ecuador.

  10. Paleomagnetism and magnetic fabric of the Eastern Cordillera of Colombia: Evidence for oblique convergence and non-rotational reactivation of a Mesozoic intra-continental rift

    Science.gov (United States)

    Jiménez Díaz, G.; Speranza, F.; Faccenna, C.; Bayona, G.; Mora, A.

    2012-12-01

    The Eastern Cordillera of Colombia (EC) is a double-verging mountain system inverting a Mesozoic rift, and bounded by major reverse faults that locally involve crystalline and metamorphic Precambrian-Lower Paleozoic basement rocks, as well as Upper Paleozoic-Cenozoic sedimentary and volcanic sequences. In map view the EC is a curved mountain belt with a regional structural strike that ranges from NNE in the southern part to NNW in the northern part. The origin of its curvature has not been studied or discussed so far. We report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) investigation of the EC, in order to address to test its non-rotational vs. oroclinal nature. Fifty-eight sites were gathered from Cretaceous to Miocene marine and continental strata, both from the southern and northern parts of the EC; additionally, we examined the southern Maracaibo plate, at the junction between the Santander Massif and the Merida Andes of Colombia (Cucuta zone). Twenty-three sites reveal no rotation of the EC range with respect to stable South America. In contrast, a 35°±9° clockwise rotation is documented in four post-Miocene magnetically overprinted sites from the Cucuta zone. Magnetic lineations from AMS analysis do not trend parallel to the chain, but are oblique to the main strike of the orogenic belt. By also considering GPS evidence of a ~1 cm/yr ENE displacement of central-western Colombia accommodated by the EC, we suggest that the late Miocene-recent deformation occurred by a ENE oblique convergence reactivating a NNE rift zone. Our data show that the EC is a non-rotational chain, and that the locations of the Mesozoic rift and the mountain chain roughly correspond. One possible solution is that the oblique shortening is partitioned in pure dip-slip shear characterizing thick-skinned frontal thrust sheets (well-known along both chain fronts), and by range-parallel right-lateral strike-slip fault(s), which have not been identified

  11. Nuevas manifestaciones ígneas básicas en el flanco occidental de la cordillera oriental, colombia

    OpenAIRE

    2012-01-01

    Se describen y localizan nuevas manifestaciones ígneas básicas en la parte central del flanco occidental de la Cordillera Oriental, las cuales se presentan generalmente a manera de diques y silos.  De acuerdo con los análisis preliminares de los resultados petrográficos y geoquímicos, las rocas corresponden a gabros similares a los reportados anteriormente al sur del área.

  12. Thermal and exhumation history of the Coastal Cordillera arc of northern Chile revealed by thermochronological dating

    Science.gov (United States)

    Juez-Larré, Joaquim; Kukowski, Nina; Dunai, Tibor J.; Hartley, Adrian J.; Andriessen, Paul A. M.

    2010-11-01

    The thermal and erosional history of convergent plate boundaries is important for understanding the links between subduction, arc magmatism, genesis of ore deposits, topography and climate of orogenic belts. Unlike the continent-continent collision that formed many of the largest orogenic belts known today, the Central Andes of South America is a unique case where an oceanic-continent collision has given rise to the Earth's longest and second tallest orogenic belt. Over the last thirty years a plethora of models have been suggested in an attempt to explain how a plateau-type orogen formed at the leading edge of western South America. In the Central Andes most research have focussed attention on the study of the evolution of the arc and backarc, since continuous subduction erosion of the forearc has left little trace of the interplate dynamics that initiated the orogenic belt. In this article, we present a new insight into the thermal and exhumation history of the forearc along the Coastal Cordillera of northern Chile based on biotite K-Ar, apatite fission-track, and apatite/zircon (U-Th)/He dating. We collected diorite samples in a 2 km thick crustal section at the coastal cliff (~ 22°S), and a sea level isoelevation profile between 21 and 27°S. Results from all three dating methods show that the cooling of Coastal Cordillera took place shortly after emplacement during a period of rifting in Jurassic times. Cooling took place in two episodes, mainly in Late Jurassic-Early Cretaceous (~ 118-152 Ma) but also during Late Cretaceous (60-80 Ma) due to the resumption of compression, rift closure, arc uplift, exhumation, eastward migration of magmatic arc activity, and thermal relaxation. The youngest apatite (U-Th)/He ages reveal a cooling event, never reported previously, between 40 and 50 Ma (Eocene). This thermal event affected a > 500 km long and > 1 km thick section of the Coastal Cordillera in northern Chile. Rock cooling recorded in the Eocene cannot be

  13. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    Science.gov (United States)

    Zech, R.; Kull, Ch.; Kubik, P. W.; Veit, H.

    2007-10-01

    Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

  14. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia deduced from 10Be surface exposure dating

    Directory of Open Access Journals (Sweden)

    H. Veit

    2007-10-01

    Full Text Available Surface exposure dating (SED is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM in the Eastern Cordilleras occurred at ~22–25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase. Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

  15. Petrographic and Geochemical Characterization of the Cambumbia STOCK in Andean Central Cordillera, Colombia

    Science.gov (United States)

    Rojas Lequerica, S.; Jaramillo Mejía, J.; Concha Perdomo, A.

    2012-12-01

    The Cambumbia Stock is located on the western flank of the Central Cordillera of the northern Andes. The goals of this study were to petrographic and geochemically characterize the Cambumbia igneous body and to establish its petrogenetic history. 41 samples were collected, 28 for petrographic analysis and 14 for elementary chemical determination by ICP-MS. Petrographically the samples were classified as hornblende and pyroxene-gabbros varying to diorites, gabbronorites and tonalites, the rock texture varies from medium to coarse granular grain, with local microporfiritic texture. It was concluded from the major elements analysis that the samples correspond to the sub-alkaline series with low K content, mainly in the calc-alkaline series, within the gabbros and diorites fields. By using the SiO2 vs TiO2 (Jaramillo, 1980), Th/Yb vs Ta/Yb (Pearce, 1984) (Fig. 1) and Zr/117-Th-Nb/16 (Wood, 1979) diagrams it was determined that these rocks were generated in two geotectonic environments: one type MOR (extension) and other island arc (subduction, compression). Petrographic and geochemical comparisons between the rocks of Cambumbia Stock and Diorite and Gabbro El Pueblito (Giraldo, 2009) (located about 25 km to the north-west) may postulate a possible genetic link between them. Recently, a U/Pb age was obtained by the Universidad de Caldas in zircon in 2009 (not published data), yielded an age of 233.41 ± 3.4 Ma (Middle Triassic). This age is consistent with the global event of the extension and fragmentation of Pangea supercontinent. In addition, the mantle nature of the source and the petrogenetic evolution of the magmatic system were established. References GIRALDO, M.I., (2009): Esquema geodinámica de la parte noroccidental de la cordillera Central de Colombia. (Thesis). p.56-68. Universidad Nacional de Colombia, Medellín. JARAMILLO, J.M. (1980): Petrology and geochemistry of the Nevado del Ruiz Volcano northern Andes, Colombia (Thesis). 167 p. University of Houston

  16. Constraining the crustal root geometry beneath the Rif Cordillera (North Morocco)

    Science.gov (United States)

    Diaz, Jordi; Gil, Alba; Carbonell, Ramon; Gallart, Josep; Harnafi, Mimoun

    2016-04-01

    The analyses of wide-angle reflections of controlled source experiments and receiver functions calculated from teleseismic events provide consistent constraints of an over-thickened crust beneath the Rif Cordillera (North Morocco). Regarding active source data, we investigate now offline arrivals of Moho-reflected phases recorded in RIFSIS project to get new estimations of 3D crustal thickness variations beneath North Morocco. Additional constrains on the onshore-offshore transition are derived from onland recording of marine airgun shots from the coeval Gassis-Topomed profiles. A regional crustal thickness map is computed from all these results. In parallel, we use natural seismicity data collected throughout TopoIberia and PICASSO experiments, and from a new RIFSIS deployment, to obtain teleseismic receiver functions and explore the crustal thickness variations with a H-κ grid-search approach. The use of a larger dataset including new stations covering the complex areas beneath the Rif Cordillera allow us to improve the resolution of previous contributions, revealing abrupt crustal changes beneath the region. A gridded surface is built up by interpolating the Moho depths inferred for each seismic station, then compared with the map from controlled source experiments. A remarkably consistent image is observed in both maps, derived from completely independent data and methods. Both approaches document a large modest root, exceeding 50 km depth in the central part of the Rif, in contrast with the rather small topographic elevations. This large crustal thickness, consistent with the available Bouguer anomaly data, favor models proposing that the high velocity slab imaged by seismic tomography beneath the Alboran Sea is still attached to the lithosphere beneath the Rif, hence pulling down the lithosphere and thickening the crust. The thickened area corresponds to a quiet seismic zone located between the western Morocco arcuate seismic zone, the deep seismicity area

  17. Recent evolution and degradation of the bent Jatunraju glacier (Cordillera Blanca, Peru)

    Science.gov (United States)

    Emmer, Adam; Loarte, Edwin C.; Klimeš, Jan; Vilímek, Vít

    2015-01-01

    This article brings new insight into the recent evolution and degradation of the bent Jatunraju glacier in the northern part of the Cordillera Blanca, Peru. Analysis of topographical maps, aerial photos and satellite images covering a period of 66 years and a field survey performed in June 2013 and May 2014 helped to describe the geomorphological setting and ongoing processes. Recent evolution and degradation processes are also deduced from surface movements. Historical geodetic measurements (1967-1968; 1977-1984) and current LANDSAT images (2001-2013) were used to estimate surface velocities and changes in surface velocities over time. Our investigation showed that the most significant changes happened at an altitude of between 4300 and 4450 m asl. A significant decrease in surface velocities and increase in debris thickness indicate that this part of Jatunraju turned from a debris-covered glacier into an ice-cored rock glacier during the analyzed period. Particular parts of the article describe the cycle of formation and extinction of supraglacial lakes and the melting of buried (debris-covered) ice. A scenario of future evolution is outlined and discussed as well. We assume that ice degradation within the debris-covered glacier will continue and that the altitude of its presence will increase hand-in-hand with the changing environment.

  18. Glacier Retreat in the Cordillera Quimza Cruz (Tres Cruces), Bolivia from 1975 to present

    Science.gov (United States)

    Klein, A. G.; Kincaid, J. L.; Brooks, R. M.

    2008-12-01

    The glaciers in the Cordillera Quimza Cruz (Tres Cruces) and two smaller Bolivian massifs represent the southernmost tropical glaciers found along the eastern margin of the Andes. Their marginal location makes them of particular interest. The extent of glaciers in the mid 1970s was determined though digitization of the published glacier inventory of Bolivia. In 1975, extent of glaciers in the Tres Cruces region was approximately 55.4 square kilometers. More recent extents were determined from Landsat and ASTER satellite images. Cloud-free Landsat images from 1986, 1992 and 2000 were georegistered and surface reflectances were computed. Normalized Difference Snow Index (NDSI) images were then computed and thresholded to create binary maps of snow- and glacier-covered pixels. From 1975 through 2000, the Tres Cruces Region lost a significant amount of its glacier area. Of the area identified as being glacier covered in 1975 only 27.4 square kilometers (49%) were identified as containing snow and ice in Landsat images from 2000. The glacier retreat time series is being updated as part of an ongoing undergraduate research program. More recent retreat mapped from multiple ASTER images from 2000-2006 indicates that glacier recession is continuing. Changes in glacier hypsometries indicate that much of the areal loss has occurred at lower altitudes. The influence of aspect on glacier retreat is the next area of investigation.

  19. TranSCorBe Project: A high-resolution seismic-passive profile to study the variation of the crustal and upper mantle structures under the Betic mountain ranges

    Science.gov (United States)

    Morales, José; Martín, Rosa; Stich, Daniel; Heit, Benjamín; Yuan, Xiaohui; Mancilla, Flor; Benito, José; Carrion, Francisco; Serrano, Inmaculada; López-Comino, Jose Angel; Abreu, Rafael; Alguacil, Gerardo; Almendros, Javier; Carmona, Enrique; Ontiveros, Alfonso; García-Quiroga, Daniel; García-Jerez, Antonio

    2014-05-01

    The goal of this project is to study the crustal and upper mantle structures under the Betic mountain ranges and their variations between the different geological domains. We deployed 50 broadband and short period seismic stations during 18 months following two profiles. We collect teleseismic events to perform a high-resolution P-to-S and S-to-P receiver function analysis. The main profile (TranSCorBe), of 160 km length, starts near the coast in Mazarrón (Murcia) and follows a NW-SE direction, crossing the Cazorla mountain range. It probes, from south to north, the Alboran domain (metamorphic rocks), the External zones (sedimentary rocks) and the Variscan terrains of the Iberian Massif. The spacing between stations is around 3-4 km. This inter-station distance allows us mapping with high accuracy the variations of the crust and upper mantle discontinuities in the Betic Range and their transition to the Iberian Massif. A second profile (HiRe II) with a larger spacing between seismic stations, is a continuation of a previously installed HiRe I profile, a NS profile starting near the Mediterranean coast in Adra (Almería) through Sierra Nevada Mountains. HiRe II profile prolongs HiRe I profile until the Variscan intersecting with TranSCorBe profile near Cazorla.

  20. Provenance of the late Proterozoic to early Cambrian metaclastic sediments of the Sierra de San Luis (Eastern Sierras Pampeanas) and Cordillera Oriental, Argentina

    Science.gov (United States)

    Drobe, Malte; López de Luchi, Mónica G.; Steenken, André; Frei, Robert; Naumann, Rudolf; Siegesmund, Siegfried; Wemmer, Klaus

    2009-10-01

    Provenance studies have been performed utilising major and trace elements, Nd systematics, whole rock Pb-Pb isotopes and zircon U/Pb SHRIMP data on metasedimentary rocks of the Sierra de San Luis (Nogolí Metamorphic Complex, Pringles Metamorphic Complex, Conlara Metamorphic Complex and San Luis Formation) and the Puncoviscana Formation of the Cordillera Oriental. The goal was the characterisation of the different domains in the study area and to give insights to the location of the source rocks. An active continental margin setting with typical composition of the upper continental crust is depicted for all the complexes using major and trace elements. The Pringles Metamorphic Complex shows indications for crustal recycling, pointing to a bimodal provenance. Major volcanic input has to be rejected due to Th/Sc, Y/Ni and Cr/V ratios for all units. The ɛNd (540 Ma) data is lower for the San Luis Formation and higher for the Conlara Metamorphic Complex, as compared to the other units, in which a good consistency is given. This is similar to the TDM ages, where the metapsammitic samples of the San Luis Formation are slightly older. The spread of data is largest for the Pringles Metamorphic Complex, again implying two different sources. The whole rock 207Pb/ 206Pb isotopic data lies in between the South American and African sources, excluding Laurentian provenances. The whole rock Pb-Pb data is almost indistinguishable in the different investigated domains. Only the PMC shows slightly elevated 208Pb/ 204Pb values. Possible source rocks for the different domains could be the Quebrada Choja in the Central Arequipa-Antofalla domain, the Southern domain of the Arequipa-Antofalla basement, the Brazilian shield or southern Africa. Zircon SHRIMP data point to a connection between the Puncoviscana Formation and the Conlara Metamorphic Complex. Two maxima around 600 Ma and around 1000 Ma have been determined. The Nogolí Metamorphic Complex and the Pringles Metamorphic Complex

  1. Present and future water resources supply and demand in the Central Andes of Peru: a comprehensive review with focus on the Cordillera Vilcanota

    Science.gov (United States)

    Drenkhan, Fabian; Huggel, Christian; Salzmann, Nadine; Giráldez, Claudia; Suarez, Wilson; Rohrer, Mario; Molina, Edwin; Montoya, Nilton; Miñan, Fiorella

    2014-05-01

    Glaciers have been an important element of Andean societies and livelihoods as direct freshwater supply for agriculture irrigation, hydropower generation and mining activities. Peru's mainly remotely living population in the Central Andes has to cope with a strong seasonal variation of precipitations and river runoff interannually superimposed by El Niño impacts. Direct glacier and lake water discharge thus constitute a vital continuous water supply and represent a regulating buffer as far as hydrological variability is concerned. This crucial buffer effect is gradually altered by accelerated glacier retreat which leads most likely to an increase of annual river runoff variability. Furthermore, a near-future crossing of the 'peak water' is expected, from where on prior enhanced streamflow decreases and levels out towards a new still unknown minimum discharge. Consequently, a sustainable future water supply especially during low-level runoff dry season might not be guaranteed whereas Peru's water demand increases significantly. Here we present a comprehensive review, the current conditions and perspectives for water resources in the Cusco area with focus on the Vilcanota River, Cordillera Vilcanota, Southern Peru. With 279 km2 the Cordillera Vilcanota represents the second largest glacierized mountain range of the tropics worldwide. Especially as of the second half of the 1980s, it has been strongly affected by massive ice loss with around 30% glacier area decline until present. Furthermore, glacier vanishing triggers the formation of new lakes and increase of lake levels and therefore constitutes determining hazardous drivers for mass movements related to deglaciation effects. The Vilcanota River still lacks more profound hydrological studies. It is likely that its peak water has already been or might be crossed in near-future. This has strong implications for the still at 0.9% (2.2%) annually growing population of the Cusco department (Cusco city). People mostly

  2. Dinámica e implicancia del aluvión de la laguna 513, Cordillera Blanca, Ancash, Perú Dinamics and implications of the laguna 513 Aluvion, Cordillera Blanca, Ancash Perú

    Directory of Open Access Journals (Sweden)

    Patricio Valderrama

    2012-09-01

    Full Text Available La Cordillera Blanca, al norte de Perú, es la zona con más actividad geodinámica externa en Perú. En ella ocurrieron grandes flujos de detritos de origen glaciar, varios de ellos fueron grandes desastres y cobraron miles de vidas. El 11 de abril del 2010, la laguna 513, ubicada en el centro de la Cordillera Blanca, sufrió un desembalse parcial por la caída de un gran bloque de hielo y rocas del nevado Hualcán (5500 m.s.n.m.. Este evento pese a ser de dimensiones considerables, no generó grandes pérdidas ni afectó alguna ciudad importante. Mediante simulaciones numéricas de flujo se estudió su dinámica, se determinó sus volúmenes y su turbulencia así como también explicamos e papel de la morfología de la zona en la desaceleración del flujo, su encausamiento en un valle fluvial y su posterior comportamiento como crecida de río. Las simulaciones realizadas mediante FLO2D se validan mediante comparaciones con imágenes de satélite post evento y datos de campo.The Cordillera Blanca in northern Peru is the most external geodynamics active areas in Perú. There have been occurred the biggest glacier source debris flow in the Peruvian history, most of them became on major disasters and claimed thousands of lives. On April 11th, 2010, the Laguna 513, located in the center of the Cordillera Blanca, suffered a partial GLOF due a massive rock and ice fall from Nevado Hualcán (5500 masl. This event, despite being of considerable size, did not generate large losses or affect any major city. Using numerical simulations we study the dynamics of the consequent GLOF and debris flow. We determined the volume and turbulence as well as also explained the role of the geomorphology of the area in the flow deceleration process and the river flood subsequent behavior. The FLO 2D simulations are validated with post event satellite image and field data.

  3. Slope deformations in high-mountain regions as observed by InSAR: Examples from the Cordillera Blanca, Peru

    Science.gov (United States)

    Frey, Holger; Strozzi, Tazio; Caduff, Rafael; Huggel, Christian; Klimeš, Jan; Vilímek, Vít; Wiesmann, Andreas; Kääb, Andreas; Cochachin, Alejo; Plummer, Stephen

    2016-04-01

    Steep topography, the world's highest concentration of tropical glaciers, numerous glacial lakes and strong seismic activity combined with a densely populated valley bottom in the Rio Santa basin characterize the Cordillera Blanca in Peru. Besides glacier-related processes, a variety of landslide types and processes is present outside the glaciated areas, favoured by the steep terrain, geological conditions, sparse vegetation, intense precipitation, and strong seismicity. This combination of high hazard potentials and vulnerabilities results in a long list of natural disasters. Information on surface displacements is very valuable for early detection of emerging hazard potentials and their assessment. Interferometric processing of SAR data (InSAR) provides the possibility to remotely detect different types of surface displacement processes, also in remote locations where no other monitoring data are available. This contribution, developed under the ESA-funded S:GLA:MO project (sglamo.gamma-rs.ch), shows the potential of InSAR products for hazard assessments and glaciological investigations in high-mountain regions. We present a selection of different surface displacements as observed in the Cordillera Blanca based on InSAR data: a landslide zone near the Rampac Grande village, where in 2009 a landslide caused casualties and property loss; a landslide at the entry of the Santa Cruz Valley, northern Cordillera Blanca, where the displacement history could be reconstructed over five years; surface displacements at the interior moraine slopes surrounding Laguna Palcacocha, a major glacier lake above the city of Huaraz, which are compared to and complemented by geophysical investigations in the field; surface displacements at the moraine damming Laguna Safuna Alta, a glacier lake in the northern part of the Cordillera Blanca; glacier velocities across the entire Cordillera Blanca, revealing ice flow velocities of more than 200 m yr-1 at certain locations at the end of

  4. Paleontologic and stratigraphic relations of phosphate beds in Upper Cretaceous rocks of the Cordillera Oriental, Colombia

    Science.gov (United States)

    Maughan, Edwin K.; Zambrano O., Francisco; Mojica G., Pedro; Abozaglo M., Jacob; Pachon P., Fernando; Duran R., Raul

    1979-01-01

    Phosphorite crops out in the Cordillera Oriental of the Colombian Andes in rocks of Late Cretaceous age as strata composed mostly of pelletal carbonate fluorapatite. One stratum of Santonian age near the base of the Galembo Member of the La Luna Formation crops out at many places in the Departments of Santander and Norte de Santander and may be of commercial grade. This stratum is more than one meter thick at several places near Lebrija and near Sardinata, farther south it is locally one meter thick or more near the base of the Guadalupe Formation in the Department of Boyaca. Other phosphorite beds are found at higher stratigraphic levels in the Galembo Member and the Guadalupe Formation, and at some places these may be commercial also. A stratigraphically lower phosphorite occurs below the Galembo Member in the Capacho Formation (Cenomanian age) in at least one area near the town of San Andres, Santander. A phosphorite or pebbly phosphate conglomerate derived from erosion of the Galembo Member forms the base of the Umir Shale and the equivalent Colon Shale at many places. Deposition of the apatite took place upon the continental shelf in marine water of presumed moderate depth between the Andean geosyncline and near-shore detrital deposits adjacent to the Guayana shield. Preliminary calculations indicate phosphorite reserves of approximately 315 million metric tons in 9 areas, determined from measurements of thickness, length of the outcrop, and by projecting the reserves to a maximum of 1,000 meters down the dip of the strata into the subsurface. Two mines were producing phosphate rock in 1969; one near Turmeque, Boyaca, and the other near Tesalia, Huila.

  5. Documenting and describing the redox evolution of the Neoproterozoic ocean: lessons from the Canadian Cordillera (Invited)

    Science.gov (United States)

    Johnston, D. T.; Poulton, S. W.; Langmuir, C. H.; MacDonald, F. A.; Chen, Z.; Knoll, A.

    2009-12-01

    The geological record of the Neoproterozoic preserves evidence for large-scale perturbations in Earth’s climate and changes in tectonic configuration. During the terminal Proterozoic, and within the context of these changes, Earth’s fluid envelope achieved a level of oxygenation that allowed for the evolution and subsequent radiation of complex multi-cellular life. As such, better constraining the geochemical evolution of the oceans and atmosphere throughout the entire Neoproterozoic will allow for a more mechanistic understanding of the links between changing environmental chemistry and biological innovation. Further, it will provide information on the relative timing of these changes and, where robust dates are available, estimates on the absolute rates of change (both chemical and biological). To this end, our ongoing work has focused on constructing high stratigraphic resolution geochemical records through mixed lithological packages of sedimentary rocks from eastern Alaska and the Canadian Cordillera. Here, we present detailed chemostratigraphic reconstructions of redox sensitive proxies, including Fe-speciation and trace element budgets, that provide an integrated window into Neoproterozoic marine oxidant budgets. These oxidant budgets then allow for the modeling of the relative influence of different aerobic and anaerobic microbial processes on the overall carbon cycle. Taken together, it is this cascade of microbial processes that drives remineralization reactions, the sum of which serves to counter-act organic carbon export, which is ultimately responsible for the buildup of O2. This simple framework serves as the foundation for our interpretation of Neoproterozoic biogeochemistry and informs our view of late Precambrian marine ecosystems. This approach can be further applied to more specific, and perhaps even more anomalous intervals of Neoproterozoic Earth history, including the Cryogenian Bitter Springs event and the Ediacaran Shuram anomaly; both

  6. Fluid flow along North American Cordillera detachments determined from stable isotope and high resolution chemical analyses

    Science.gov (United States)

    Quilichini, A.; Teyssier, C.; Mulch, A.; Nachlas, W.

    2009-12-01

    Fluid flow is likely a major parameter controlling the dynamics of extensional detachment zones. Buoyancy-driven fluid flow is generated by high heat flow beneath the detachment zone, where heat is advected by crustal thinning and magma intrusions. This hydrothermal convective flow is focused in the detachment zone for the duration of activity of the detachment at relatively high temperature (300-500°C), resulting in very significant fluid-rock interaction and isotopic exchange. Quantifying sources and fluid flux in detachments is a challenge because permeability of ductilely deforming rocks is poorly understood. In order to solve these problems, we studied two different Eocene extensional systems in the North American Cordillera: the quartzitic detachment which borders the Kettle dome metamorphic core complex (WA), and the quartzo-feldspathic Bitterroot shear zone along the Idaho batholith (MT). The Kettle Dome detachment provides a continuous section of ~200 m thick quartzite mylonite where high-resolution sampling (~5 m) indicates that Deuterium isotopic ratios that are obtained from synkinematic muscovite grains are consistent with a meteoric fluid source (-130 per mil). In the Bitterroot shear zone, Coyner (2003) reported similar Deuterium isotopic ratios (down to -140 per mil) in muscovite from mylonites and ultramylonites. Microprobe analyses were obtained for white mica porphyroclasts by performing transects perpendicular to the basal (001) cleavage in order to determine intragrain chemical zoning. Preliminary results for the Kettle dome indicate increasing phengite composition with depth, suggesting enhanced activity of the Tschermak exchange. The variations of the phengitic signature in muscovite indicates that temperature diminuish downsection, which is contradictory with the results obtained by the Qz-Ms oxygen isotope thermometer along the Kettle section. Our recent work provides geologic data for numerical models that address the permeability of

  7. New method for assessing the potential hazardousness of glacial lakes in the Cordillera Blanca, Peru

    Directory of Open Access Journals (Sweden)

    A. Emmer

    2014-02-01

    Full Text Available This paper presents a new and easily repeatable objective method for assessing the potential hazardousness of glacial lakes within the Peruvian region of Cordillera Blanca (excluding ice-dammed lakes, which do not reach significant volumes in this region. The presented method was designed to meet four basic principles, which we considered as being crucial. These are: (a principle of regional focus; (b principle of objectivity; (c principle of repeatability; and (d principle of multiple results. Potential hazardousness is assessed based on a combination of decision trees for clarity and numerical calculation for objectivity. A total of seventeen assessed characteristics are used, of which seven have yet to be used in this context before. Also, several ratios and calculations are defined for the first time. We assume that it is not relevant to represent the overall potential hazardousness of a particular lake by one result (number, thus the potential hazardousness is described in the presented method by five separate results (representing five different glacial lake outburst flood scenarios. These are potentials for: (a dam overtopping resulting from a dynamic slope movement into the lake; (b dam overtopping following the flood wave originating in a lake situated upstream; (c dam failure resulting from a dynamic slope movement into the lake; (d dam failure following the flood wave originating in a lake situated upstream; and (e dam failure following a heavy earthquake. All of these potentials theoretically range from 0 to 1. The presented method was verified on the basis of assessing the pre-flood conditions of seven lakes which have produced ten glacial lake outburst floods in the past and ten lakes which have not. A comparison of these results showed that the presented method successfully identifies the potentially hazardous lakes.

  8. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    Science.gov (United States)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

    2015-12-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from E-W in the Patagonian Andes to N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin controlled

  9. Soil charcoal analysis as a climato-stratigraphical tool: The key case of Cordillera Real, northern Andes

    Energy Technology Data Exchange (ETDEWEB)

    Di Pasquale, G. [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Impagliazzo, S., E-mail: stefania.impagliazzo@unina.i [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Lubritto, C. [CIRCE, Dipartimento di Scienze Ambientali, II Universita di Napoli, and INNOVA, via Vivaldi, 43, 81100 Caserta (Italy); Marziano, M. [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Passariello, I. [CIRCE, Dipartimento di Scienze Ambientali, II Universita di Napoli, and INNOVA, via Vivaldi, 43, 81100 Caserta (Italy); Ermolli, E. Russo [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy)

    2010-04-15

    The present study represents the first attempt of reconstructing fire history through soil charcoal dating. The investigated area is located in the Guandera Biological Reserve (western Cordillera Real, northern Ecuador). Six AMS radiocarbon dating, performed at the base of five soil profiles allowed a fire phase to be identified during the Pleistocene-Holocene transition. A strong correspondence was highlighted between the age of the Guandera fires and the El Abra stadial, which is considered the Younger Dryas equivalent in South America. This local evidence of fires contributes to define the geographic area in which the El Abra stadial was recorded and suggests a wider use of the soil charcoal analysis.

  10. Late Quaternary geomorphic history of a glacial landscape - new sedimentary and chronological data from the Cordillera de Cochabamba (Bolivia)

    Science.gov (United States)

    May, J.-H.; Preusser, F.; Zech, R.; Ilgner, J.; Veit, H.

    2009-04-01

    Throughout the Central Andes, glacial landscapes have long been used for the reconstruction of Late Quaternary glaciations and landscape evolution. Much work has focused on the Andes in Peru, Chile and the Bolivian Altiplano, whereas relatively little data has been published on glaciation history in the eastern Andean ranges and slopes. Even less is known with regard to the postglacial evolution of these glacial landscapes. In the Cordillera de Cochabamba (Bolivia), local maximum advances probably peaked around 20-25 ka BP and were followed by significant readvances between ~12-16 ka BP. This generally points to temperature controlled maximum glacial advances along the humid eastern slopes of the Central Andes, which is supported by glacier-climate-modelling studies. However, most studies include only marginal information with regard to the complex geomorphic and sedimentary situation in the Cordillera de Cochabamba. Furthermore, the chronological results are afflicted with several methodological uncertainties inherent to surface exposure dating and call for application of alternative, independent age dating methods. Therefore this study aims at i) documenting and interpreting the complex glacial geomorphology of the Huara Loma valley in the Cordillera de Cochabamba (Bolivia), ii) analyzing the involved units of glacial sediments, and iii) improving the chronological framework by applying optically stimulated luminescence (OSL) and radiocarbon dating (14C). For this purpose, geomorphic mapping was combined with field documentation of sedimentary profiles. The involved sediments were subject to geochemical and mineralogical analysis in order to deduce information on their erosional and weathering histories. In addition, the interpretation of OSL ages from glacial and proglacial sediments integrated several methodological procedures with regard to sample preparation and statistical analysis of the measurements in order to increase the degree of confidence. These

  11. Mapping Glacier Dynamics and Proglacial Wetlands with a Multispectral UAV at 5000m in the Cordillera Blanca, Peru

    Science.gov (United States)

    Wigmore, O.; Mark, B. G.

    2015-12-01

    The glaciers of the Cordillera Blanca, Peru are rapidly retreating as a result of rising temperatures, transforming the hydrology and impacting the socio-economic and environmental systems of the Rio Santa basin. Documenting the heterogeneous spatial patterns of these changes to understand processes of water storage and flow is hindered by technologic and logistic challenges. Highly complex topography, cloud cover and coarse spatial resolution limit the application of satellite data while airborne data collection remains costly and potentially dangerous. However, recent developments have made Unmanned Aerial Vehicle (UAV) technology a viable and potentially transformative method for studying glacier dynamics and proglacial hydrology. The extreme altitudes (4000-6700m) of the Cordillera Blanca limit the use of 'off the shelf' UAVs. Therefore we developed a low cost multispectral (visible, near-infrared and thermal infrared) multirotor UAV capable of conducting fully autonomous aerial surveys at elevations over 5000m within the glacial valleys of the Cordillera Blanca. Using this platform we have completed repeat aerial surveys (in 2014 and 2015) of the debris covered Llaca Glacier, generating highly accurate 10-20cm DEM's and 5cm orthomosaics using a structure from motion workflow. Analysis of these data reveals a highly dynamic system with some areas of the glacier losing as much as 16m of vertical elevation, while other areas have gained up to 5m of elevation over one year. The magnitude and direction of these changes appears to be associated with the presence of debris free ice faces and meltwater ponds. Additionally, we have mapped proglacial meadow and wetland systems. Thermal mosaics at 10-20cm resolution are providing novel insights into the hydrologic pathways of glacier meltwater including mapping the distribution of artesian springs that feed these wetland systems. The high spatial resolution of these UAV datasets facilitates a better understanding of the

  12. Rhyolitic calderas and centers clustered within the active andesitic belt of Ecuador's Eastern Cordillera

    Energy Technology Data Exchange (ETDEWEB)

    Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: pmothes@igepn.edu.ec

    2008-10-01

    In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.

  13. A distinctive new subspecies of Scytalopus griseicollis (Aves, Passeriformes, Rhinocryptidae) from the northern Eastern Cordillera of Colombia and Venezuela

    Science.gov (United States)

    Avendaño, Jorge Enrique; Donegan, Thomas M.

    2015-01-01

    Abstract We describe a new subspecies of Pale-bellied Tapaculo Scytalopus griseicollis from the northern Eastern Cordillera of Colombia and Venezuela. This form differs diagnosably in plumage from described subspecies Scytalopus griseicollis griseicollis and Scytalopus griseicollis gilesi and from the latter in tail length. It is also differentiated non-diagnosably in voice from both these populations. Ecological niche modelling analysis suggests that the new subspecies is restricted to the Andean montane forest and páramo north of both the arid Chicamocha valley and the Sierra Nevada del Cocuy. PMID:26085800

  14. Paleoatimetry of southern Tibet and the central Andes

    Science.gov (United States)

    Quade, J.; Dettinger, M. P.; DeCelles, P. G.; Leary, R.; Kapp, P. A.

    2011-12-01

    Here we explore a variety of isotopic systems to reconstruct paleoatitude in southern Tibet and the central Andes. A multi-system approach is essential since the necessary mineral archives are not always available, and because diagenetic resetting of some systems clearly occurs. In the central Andes at ~24°S, carbonate is rare due to hyperaridity, and where present, evaporation in soils and lakes completely alters the primary meteoric signal. Waters of hydration of volcanic glass are a much more promising target in this region given the prevalence of volcanic tuffs. We have analyzed the δD value of a suite of modern and ancient glasses back to 34 Ma that show little change in elevation in the western Cordillera of the Andes. By contrast, the eastern Cordillera of the Andes rose in the last 15 Ma. This pattern is consistent with gradual eastward propagation of the whole orogen at this latitude, including the trench, forearc, magmatic arc, and foreland. The paleoaltimetry of Tibet poses quite different challenges to those in South America. Volcanic glass archives are so far unavailable, whereas carbonate archives are common but in some cases diagenetically reset. We have focused on records of conventional δ18O values and clumped isotope thermometry. One must treat both archives with great caution due to resetting, especially clumped isotopes. Available evidence suggests that southern Tibet has been near current elevations since the early Miocene. For the pre- Miocene we present new isotopic/paleosol records found along the suture zone of India and Asia that we believe partly chronicle the rise of the suture zone from near sea-level to >4000 m today.

  15. Shortening Record in the Central Andean Plateau of Southern Peru: Basement Inversion, Thin-skinned Thrusting, and Geomorphic Response

    Science.gov (United States)

    Perez, N.; Horton, B. K.; McQuarrie, N.; Stübner, K.; Ehlers, T. A.

    2015-12-01

    Variations in the inherited structural architecture along western South America influence the timing, magnitude, and style of Andean deformation and topographic evolution. New results from mapping, balanced cross-section construction, apatite and zircon (U-Th)/He thermochronology, and geomorphology spanning the Altiplano, Eastern Cordillera and Subandean zone of southern Peru define the role of Triassic rift inversion on Cenozoic deformation style, thrust belt kinematics, exhumation timing, and spatial variation of canyon incision. A minimum of 130 km (38%) shortening along a 200 km transect accommodated by thin- and thick-skinned structures involved selective reactivation of Triassic normal faults that fed slip to shallower detachments of thin-skinned fold-thrust systems. Map relationships define unique structural domains defined by inherited normal faults. In the Eastern Cordillera, new zircon (U-Th)/He results from a Triassic pluton reveal Oligocene-Miocene (~26-18 Ma) cooling, consistent with previously reported exhumation from ~40 km along strike to the NW. However, rapid ~15 Ma cooling revealed by new apatite (U-Th)/He data is ~11 Myr older than equivalent rocks in a similar structural setting ~40 km to the NW. This suggests a potential middle Miocene shift from synchronous to diachronous exhumation along strike. Modern fluvial profiles constructed along the Eastern Cordillera show a reduction in knickpoint elevations from SE to NW, suggesting more youthful uplift toward the NW, comparable to the spatial trend in apatite (U-Th)/He ages. The deformation front reached the Subandean zone by ~15 Ma, after the majority of reported deformation in the Eastern Cordillera and Altiplano. These variations in exhumation over such distances are consistent with multiple potential scenarios: a northward propagating wave of uplift, spatial variations in climatically driven incision, interactions with mantle dynamics, or complex structural geometries.

  16. Miocene orographic uplift forces rapid hydrological change in the southern central Andes

    Science.gov (United States)

    Rohrmann, Alexander; Sachse, Dirk; Mulch, Andreas; Pingel, Heiko; Tofelde, Stefanie; Alonso, Ricardo N.; Strecker, Manfred R.

    2016-10-01

    Rainfall in the central Andes associated with the South American Monsoon and the South American Low-Level Jet results from orographic effects on atmospheric circulation exerted by the Andean Plateau and the Eastern Cordillera. However, despite its importance for South American climate, no reliable records exist that allow decoding the evolution of thresholds and interactions between Andean topography and atmospheric circulation, especially regarding the onset of humid conditions in the inherently dry southern central Andes. Here, we employ multi-proxy isotope data of lipid biomarkers, pedogenic carbonates and volcanic glass from the Eastern Cordillera of NW Argentina and present the first long-term evapotranspiration record. We find that regional eco-hydrology and vegetation changes are associated with initiation of moisture transport via the South American Low-Level Jet at 7.6 Ma, and subsequent lateral growth of the orogen at 6.5 Ma. Our results highlight that topographically induced changes in atmospheric circulation patterns, not global climate change, were responsible for late Miocene environmental change in this part of the southern hemisphere. This suggests that mountain building over time fundamentally controlled habitat evolution along the central Andes.

  17. Volcanism subprogram: Volcanological interpretation of the northern part of the Occidental Cordillera of Bolivia, utilizing ERTS imagery

    Science.gov (United States)

    Brockmann, C. E. (Principal Investigator); Kussmaul, S.

    1973-01-01

    The author has identified the following significant results. In the present study, 6 ERTS-1 images have been interpreted on a 1:1 million scale (black and white) with the respective field reconnaissance. The area studied is located in the region bordering with Chile and includes the western part of the Bolivian Altiplano, the volcano Cordillera (western cordillera) and the northern part of Chile to the Pacific Coast. The greater part of this region is formed by Pliocene/Pleistocene volcani rock, which is discordant with the Tertiary sediments with intercalations of calcareous tuff. The ERTS-1 imagery permits the tracing of regional boundaries of the great volcanic formations and the alinements of the volcanic bodies along the fault zones. They also permit a clear examination of the volcanic apparatus, including their secondary forms, such as lava flows, parasitic cones, and lava domes. Because of the great scale, it is not possible to identify either the small structures or those of low relief. On the basis of the interpretation of the images, it is possible to give an idea of the relative age of the volcanoes.

  18. Tectonic and unroofing history of Neogene Manantiales foreland basin deposits, Cordillera Frontal (32°30'S), San Juan Province, Argentina

    Science.gov (United States)

    Pérez, Daniel J.

    2001-12-01

    The Miocene Manantiales foreland basin is located in Cordillera Frontal of San Juan, between 32°30' and 33°S. The unroofing study of the synorogenic Miocene deposits provides information about the structural evolution of Cordón de La Ramada fold-and-thrust belt. These Tertiary deposits are represented by the Chinches Formation and comprise seven members (Tc0-Tc6). They are the result of the uplift of Mesozoic sequences that crop out in La Ramada fold-and-thrust belt of the Cordillera Principal. Quaternary deposits unconformably overlying the Chinches Formation are composed of granitic and rhyolitic blocks, and represent the final uplift of the Cordón del Espinacito and a series of out-of-sequence thrusts. The unroofing studies also provide sufficient information to establish the out-of-sequence timing of the deformation at this latitude. Initial deposition of the Tertiary deposits can be dated at about 20 Ma, or early Miocene. Andesitic lavas dated in 9.2±0.3, 10.7±0.7, and 12.7±0.7 Ma unconformably overlie the structure of La Ramada fold-and-thrust belt. These facts constrain the uplift of the High Andes between 20 and 10 Ma at this latitude. The unconformity between Tertiary and Quaternary deposits suggests final uplift during Pliocene-Pleistocene times.

  19. A new species of semiarboreal toad of the Rhinella festae group (Anura, Bufonidae) from the Cordillera Azul National Park, Peru

    Science.gov (United States)

    Cusi, Juan C.; Moravec, Jiří; Lehr, Edgar; Gvoždík, Václav

    2017-01-01

    Abstract A new semiarboreal species of the Rhinella festae group is described from montane forests of the Cordillera Azul National Park between 1245 and 1280 m a.s.l. in the Cordillera Oriental, San Martín region, northern Peru. The new species is morphologically and genetically compared with members of the Rhinella acrolopha group (former genus Rhamphophryne) and members of the R. festae group. The new species is characterized by its large size (female SVL 47.1–58.3 mm, n = 4), eight presacral vertebrae, fusion of the sacrum and coccyx, long protuberant snout, snout directed slightly anteroventral in lateral view, cranial crests moderately developed, absence of occipital crest, presence of tympanic membrane, dorsolateral rows of small conical tubercles extending from parotoid gland to groin, hands and feet with long digits, fingers basally webbed and toes moderately webbed. Phylogenetically it is a member of the R. festae group which is most closely related to R. chavin and R. yanachaga from Peru. Morphologically the new species shares similarities with R. tenrec and R. truebae, members of the R. acrolopha group from Colombia. PMID:28769671

  20. ZONIFICACIÓN AGROECOLÓGICA DE LA CORDILLERA DE GUANIGUANICO

    Directory of Open Access Journals (Sweden)

    F. Soto

    2007-01-01

    Full Text Available El desarrollo de un país necesita de una planificación de la actividad agrícola, que si se quiere que sea económicamente rentable, debe ceñirse a la realidad ecológica de las áreas de producción. En este sentido, la zonificación agroecológica es una de las principales herramientas para disminuir los riesgos a los que está sometida la agricultura. Teniendo en cuenta estos elementos, se procedió a realizar la zonificación agroecológica de la cordillera de Guaniguanico. Se tuvo información de ocho estaciones meteorológicas y 62 pluviómetros de la red del Instituto Nacional de Recursos Hidráulicos, con lo cual se llevó a cabo la zonificación climática; se estudiaron 371 000 ha, en las que se obtuvo información de más de 500 perfiles con planillas completas, lo que permitió caracterizar los suelos desde los puntos de vista físico, químico y mineralógico. Se utilizaron diferentes Sistemas de Información Geográfica (SIG, para establecer las relaciones entre los distintos parámetros estudiados y llegar a la zonificación agroecológica. A partir del análisis de la información sobre el comportamiento de los cultivos, se establecieron las bases para la zonificación, tomándose como elementos fundamentales del clima la temperatura y la lluvia; ambos se combinaron y se definieron los potenciales de rendimiento para cada condición. El otro elemento discriminante fue el suelo; en primer lugar, se tuvieron en cuenta los tipos de suelo y su aptitud para el cultivo y posteriormente se consideró la profundidad efectiva.

  1. Structural analysis of the Cordillera Blanca detachment: Geometry, kinematics and fault rocks

    Science.gov (United States)

    Shaw, C. A.; Jessup, M. J.; Hughes, C. A.; Newell, D. L.

    2015-12-01

    The Cordillera Banca Detachment (CBD) in the north-central Peruvian Andes is recognized as a rare example of active extension parallel to the direction of shortening within a convergent orogenic setting. Despite longstanding interest in the geodynamic significance of the CBD relatively little work has been done to characterize the basic geometry, kinematics and evolution of the detachment or the petrology and distribution of brittle and ductile tectonites within the fault zone. This contribution presents preliminary results of a basic structural analysis of the CBD based on field observations, laboratory results, and GIS analysis. Basic structural observations of fault geometry and kinematics are needed to constrain the regional geodynamic role of the CBD. The NNW topographic trace of the CBD is defined by faceted ridges up to 2000 m in height. The lower slopes of the facets are locally cut by steep fault scarps that offset quaternary glacial moraines, debris fans and colluvium. The shear zone comprises both brittle and ductile tectonites including mylonite series rocks, pseudotachylyte, and breccia - often highly silicified. Highly polished mirrored surfaces are observed locally. Deformation mechanisms show a consistent progression from plastic in structurally lower positions to brittle in structurally higher positions. Evidence for overprinting deformation mechanisms is preserved in many samples. The shear zone ranges up to about 200 m thick. The average orientation of mylonitic foliation and fault slip surfaces (strike/dip = 140/30) and lineations/slickenlines (plunge-trend = 35-235) is quite consistent along the ~200 km detachment, but some systematic variation along strike may be related to concave fault segments or corrugations. Slip indicators are nearly down-dip with a minor left-lateral or right-lateral component in some locations. Offsets in marker horizons constrain total offset between about 4500 m near the central section of the fault to near zero

  2. Cenozoic tectonic and climatic events in southern Iberian Peninsula: Implications for the evolutionary history of freshwater fish of the genus Squalius (Actinopterygii, Cyprinidae).

    Science.gov (United States)

    Perea, Silvia; Cobo-Simon, Marta; Doadrio, Ignacio

    2016-04-01

    Southern Iberian freshwater ecosystems located at the border between the European and African plates represent a tectonically complex region spanning several geological ages, from the uplifting of the Betic Mountains in the Serravalian-Tortonian periods to the present. This area has also been subjected to the influence of changing climate conditions since the Middle-Upper Pliocene when seasonal weather patterns were established. Consequently, the ichthyofauna of southern Iberia is an interesting model system for analyzing the influence of Cenozoic tectonic and climatic events on its evolutionary history. The cyprinids Squalius malacitanus and Squalius pyrenaicus are allopatrically distributed in southern Iberia and their evolutionary history may have been defined by Cenozoic tectonic and climatic events. We analyzed MT-CYB (510 specimens) and RAG1 (140 specimens) genes of both species to reconstruct phylogenetic relationships and to estimate divergence times and ancestral distribution ranges of the species and their populations. We also assessed their levels of genetic structure and diversity as well as the amount of gene flow between populations. To investigate recent paleogeographical and climatic factors in southern Iberia, we modeled changes-through-time in sea level from the LGM to the present. Phylogenetic, geographic and population structure analyses revealed two well-supported species (S. malacitanus and S. pyrenaicus) in southern Iberia and two subclades (Atlantic and Mediterranean) within S. malacitanus. The origin of S. malacitanus and the separation of its Atlantic and Mediterranean populations occurred during the Serravalian-Tortonian and Miocene-Pliocene periods, respectively. These divergence events occurred in the Middle Pliocene and Pleistocene in S. pyrenaicus. In both species, Atlantic basins possessed populations with higher genetic diversity than Mediterranean, which may be explained by the Janda Lagoon. The isolation of S. malacitanus was

  3. Pollen-based 17-kyr forest dynamics and climate change from the Western Cordillera of Colombia: no-analogue associations and temporarely lost biomes

    NARCIS (Netherlands)

    Velásquez-R., C.A.; Hooghiemstra, H.

    2013-01-01

    A 17 kyr long pollen record from the unexplored Western Cordillera of Colombia (Páramo de Frontino; 3460 m elevation) shows vegetation change and inferred climate dynamics at ~ 125 yr resolution. The cold and wet Lateglacial showed well-defined stadials and interstadials. At the transition to the Ho

  4. Pollen-based 17-kyr forest dynamics and climate change from the Western Cordillera of Colombia: no-analogue associations and temporarely lost biomes

    NARCIS (Netherlands)

    Velásquez-R., C.A.; Hooghiemstra, H.

    2013-01-01

    A 17 kyr long pollen record from the unexplored Western Cordillera of Colombia (Páramo de Frontino; 3460 m elevation) shows vegetation change and inferred climate dynamics at ~ 125 yr resolution. The cold and wet Lateglacial showed well-defined stadials and interstadials. At the transition to the

  5. La vegetación azonal paramunade la Cordillera Oriental colombiana: síntesis fitosociológica preliminar

    Directory of Open Access Journals (Sweden)

    Rangel Churio Orlando

    2006-06-01

    Full Text Available El presente estudio aplica el uso de herramientas sistematizadas y los conceptos clásicos de la fitosociología en la identificación, caracterización y síntesis preliminar de las unidades de vegetación azonal presentes en la cordillera Oriental, revisando las propuestas anteriores de clasificación y analizando conjuntamente la información obtenida de 500 levantamientos realizados en la cordillera por numerosos investigadores entre 1976 y 2001 abarcando el área comprendida entre las regiones paramunas de Almorzadero al norte, Sumapaz al sur y occidente y la Sierra Nevada del Cocuy al oriente, distribuidos entre los límites con la vegetación de bosque altoandino (3.000 m hasta el superpáramo (4.435 m, incluyendo algunas localidades extrazonales (2.800 m. Se diferenciaron en total 136 unidades de vegetación distribuidas en seis clases, cinco órdenes, 17 alianzas, 61 asociaciones, 13  subasociaciones y 34 variantes, además, de 14  comunidades, agrupadas en cuatro tipos principales
    de vegetación: acuática y de ribera, cojines de pantano, herbácea de pantanos y turberas, y arbustiva de matorrales y chuscales. Los páramos del centro de la cordillera comparten la mayor riqueza de alianzas (diez,
    seguidos por los de la región Sur (nueve y los de Chingaza (ocho; la mayor riqueza de asociaciones se concentra en los páramos del sur y centro de la cordillera y en la región de la Sierra Nevada del Cocuy (25, 21 y 18 respectivamente. La vegetación de cinco alianzas presenta distribución restringida, tres de ellas existentes
    en la región de Tota, una en el centro de la cordillera y la restante en la región de Chingaza; el mayor número
    de asociaciones con distribución restringida se presenta en los páramos del Centro de la cordillera (diez, en la
    región de Tota (siete y en la región Sur (cinco. La vegetación de las alianzas Ditricho-Isoetion y Oreobolio-Plantagion posee amplia distribución a lo largo de

  6. New thermo and geochronological constraints on the Pliocene-Pleistocene eruption history of the Paipa-Iza volcanic complex, Eastern Cordillera, Colombia

    Science.gov (United States)

    Bernet, Matthias; Urueña, Cindy; Amaya, Sergio; Peña, Mary L.

    2016-11-01

    The Paipa-Iza volcanic complex is the only volcanic edifice in the Eastern Cordillera of Colombia. Zircon fission-track and Usbnd Pb data from deposits of two eruption epochs presented in this study constrain the time of volcanic activity between 5.9 Ma in the late Miocene and at least 1.8 Ma during the early Pleistocene. These ages correspond to 3.6 to 4.7 Ma zircon fission-track ages reported from tephra deposits of the Tierra Negra region to the southwest of the Paipa-Iza volcanic complex in the Eastern Cordillera. A 4 Myr period of volcanic activity is longer than the previously documented 2.5 Ma to 1.9 Ma activity in the Paipa-Iza area. Therefore, our data show that the Paipa-Iza volcanic complex was active during the entire Pliocene phase of rapid surface uplift, when the Eastern Cordillera reached its present-day elevation. Unclear is if the magma chamber of the Paipa-Iza volcanic complex was passively uplifted with the rest of the Eastern Cordillera, or if magmatism contributed to surface uplift. Hydrothermal activity and steep thermal gradients in the study area today indicate that a magma chamber is still present at depth. In both the zircon fission-track and Usbnd Pb data of this study the recycling of zircon from underlying Mesozoic sedimentary rocks is evident in the wide age spectra. The fission-track data show that many recycled zircons were affected at least by partial annealing, but further research is needed for constraining the thermal impact of the Paipa-Iza volcanism on the Eastern Cordillera.

  7. Timing of uplift in the Argentine Frontal Cordillera (34-32.5°S), through (U-Th)/He Thermochronology

    Science.gov (United States)

    Graber, N. R.; Hoke, G. D.; Metcalf, J. R.

    2010-12-01

    We use the apatite (U-Th)/He low temperature thermochronometer to study the rock uplift history in the Frontal Cordillera of Argentina between 32.5-34°S, where an abrupt transition in the subduction angle of the Nazca Plate occurs. The Andes in our study area are composed of three major physiographic and tectonic provinces, which have been uplifted as the deformation front stepped eastward over the last 20 Ma. From west to east they are the Principal Cordillera, Frontal Cordillera and Precordillera. The thin-skinned Aconcagua fold-thrust-belt, which today comprises the Principal Cordillera was active between ~20-8 Ma. The thick-skinned Frontal Cordillera began uplifting around 9 Ma. Finally, in the northern part of the study area, uplift and deformation of the Precordillera commenced between 5-2 Ma. South of 33°S, in the absence of the Precordillera, the total amount of crustal shortening is half that of the north, despite similar average and peak range elevations. Remnants of a regionally extensive paleolandscape are preserved in both areas. Two age-elevation profiles were collected from the granitic Permo-Triassic Choiyoi Group in the headwaters of the Rio Tunuyán (south of 33°S) and Rio Mendoza (north of 33°S). In the Tunyán area, 7 samples were collected between 2600 and 4500 m, with paleolandscape remnants at an elevation of ~5000 m. Total local relief in the Río Mendoza sampling area is 2800 m, from which the lower 1400 m were sampled between elevations of 2100 and 3500 m. We aim to constrain 1) the timing of the initiation of deformation-related exhumation of the proximal foredeep associated with the Aconcagua fold and thrust belt and 2) the rate of rock uplift induced river incision of the Rio Mendoza and Rio Tunyán as a proxy for surface uplift.

  8. Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson Glacier

    Science.gov (United States)

    Chisolm, R. E.; Mckinney, D. C.; Gomez, J.; Voss, K.

    2012-12-01

    Tropical glaciers are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glacier mass balance. This study presents GPR data taken in July 2012 at the Arteson glacier in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson glacier, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson glacier. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson glacier, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating glacier are key to assessing the flood risk from this dynamic three-lake system. Because the glacier mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson glacier and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of

  9. Glacier Mass Balance in the Cordillera Vilcanota, Glacier Suyuparina, Cusco - Peru

    Science.gov (United States)

    Sikos, Felipe; Giráldez, Claudia; Schauwecker, Simone; Molina, Edwin; Haeberli, Wilfried; Drenkhan, Fabian; Salzmann, Nadine; Rado, Maxwell; Chaparro, Nicacio; Samata, Jaime; Flores, Andrés; Saito, Carlos; Montoya, Nilton

    2017-04-01

    The Cordillera Vilcanota is the second most glaciated mountain range in Peru, and concentrates approximately 279 km2 of ice extent which corresponds to 25% of Peruvian glaciers. These glaciers have shrunk about 33% within the last 40 years and are a direct indicator of climate change impacts. Hydroclimatic changes in this region pose hazards and consecutive risks for local and regional livelihoods, socioeconomic activities and water supply. Therefore, it is important to understand high-mountain climatic and hydroglacial parameters and dynamics. In 2010/11, the first mass balance measurements were made on the Suyuparina glacier and the adjacent Quisoquipina glacier. In 2013, we have continued measurements through the present, of which we present some of the results for Suyuparina glacier. The net point mass balance for the hydrological year 2013-2014 in the lower zone is highly variable with values between +0.2 m w.e. (accumulation) and up to -6 m w.e. (ablation).; whereas for the hydrological year 2014-2015 values range from +0.004 m w.e. (accumulation) to -0.047 m w.e. (ablation) depending on the particular microtopography (e.g. ice cliffs) of the glacier. In the accumulation zone, the average for two stakes was +1.4 m w.e. for the hydrological year 2012-2013 and 1.3 m w.e.,in 2013-2014, +1.2 m w.e. for 2014-2015; and +0.7 m w.e in 2015-2016, respectively. The water equivalent gain has been gradually reduced in the last estimate, depending exclusively on the rainfall regime. The velocity of the glacial flow from October 2013 to November 2014 is in the range of 10 to 20 m per year. The glacier retreat in the front corresponds to 48.49 m for the period 2010-2014. Total glacier area of Suyuparina has decreased by 7% from about 1.21 km2 in 2009 to 1.13 km2 in 2013. A seasonal pattern can be observed in the point mass balance, indicating less ablation in the wet season (December-May), continuous ablation in the dry period, and a high horizontal ablation due to its

  10. PIPER ANDAKIENSIS (PIPERACEAE UNA ESPECIE NUEVA DE LA VERTIENTE AMAZÓNICA DE LA CORDILLERA ORIENTAL DE COLOMBIA

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    WILLIAM TRUJILLO-C.

    2015-01-01

    Full Text Available Se describe e ilustra Piper andakiensis W. Trujillo & Callejas, sp. nov. (Piperaceae procedente del piedemonte oriental de la cordillera Oriental en la jurisdicción de los departamentos de Caquetá y Putumayo (SE de Colombia. La especie nueva se distingue por sus hojas basalmente lobadas y oblicuas sobre un lado, con lobos divergentes y más cortos que el pecíolo, la lámina foliar gruesa y cartácea, con tallos, haz de la hoja, pecíolos y pedúnculos glabros y con crecimientos epidérmicos en pecíolos y márgenes peciolares; se discuten sus relaciones taxonómicas, se presentan comentarios sobre su distribución y ecología y se ilustran sus caracteres diagnósticos.

  11. A new colorful species of Pristimantis (Anura: Craugastoridae) from the eastern flank of the Cordillera Central in Colombia .

    Science.gov (United States)

    Rivera-Prieto, Diego A; Rivera-Correa, Mauricio; Daza, Juan M

    2014-12-22

    We describe a new species of Pristimantis from the humid forests on the eastern flank of the northern Cordillera Central in Colombia (6º 23' 19.3554" N, 75º 1' 24.0594" W; ca. 1150 m.a.s.l.). Pristimantis jaguensis sp. nov. is characterized by an extraordinary variation in color and is readily distinguished from congeneric species by lacking nuptial pads, discoidal fold and conical calcar tubercles; flanks and belly white to cream without blotches as well as iris yellow ocher to copper with thick brown reticulation and cream sclera. Molecular phylogenetic analyses recovered the new species in a clade with species mostly distributed in Ecuador. Our finding suggests that new taxa can still be discovered in the Middle Magdalena River valley of Colombia despite the extensive sampling this region has received during the last decades. 

  12. Review Article: Lake and breach hazard assessment for moraine-dammed lakes: an example from the Cordillera Blanca (Peru

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    A. Emmer

    2013-06-01

    Full Text Available Glacial lake outburst floods (GLOFs and related debris flows represent a significant threat in high mountainous areas across the globe. It is necessary to quantify this threat so as to mitigate their catastrophic effects. Complete GLOF hazard assessment incorporates two phases: the probability of water release from a given glacial lake is estimated through lake and breach hazard assessment while the endangered areas are identified during downstream hazard assessment. This paper outlines a number of methods of lake and breach hazard assessment, which can be grouped into three categories: qualitative, of which we outline eight; semi-quantitative, of which we outline two; and quantitative, of which we outline three. It is considered that five groups of critical parameters are essential for an accurate regionally focused hazard assessment method for moraine-dammed lakes in the Cordillera Blanca. These comprise the possibility of dynamic slope movements into the lake, the possibility of a flood wave from a lake situated upstream, the possibility of dam rupture following a large earthquake, the size of the dam freeboard (or ratio of dam freeboard, and a distinction between natural dams and those with remedial work. It is shown that none of the summarised methods uses all these criteria with, at most, three of the five considered by the outlined methods. A number of these methods were used on six selected moraine-dammed lakes in the Cordillera Blanca: lakes Quitacocha, Checquiacocha, Palcacocha, Llaca, Rajucolta, and Tararhua. The results have been compared and show that each method has certain advantages and disadvantages when used in this region. These methods demonstrate that the most hazardous lake is Lake Palcacocha.

  13. Petrology and chemistry of late Cretaceous volcanic rocks from the southernmost segment of the Western Cordillera of Colombia (South America)

    Science.gov (United States)

    Spadea, P.; Espinosa, A.

    1996-03-01

    This paper presents new data on the petrology and chemistry of the igneous rocks composing the Mesozoic basement of southernmost Western Cordillera of Colombia along the Ricaurte-Altaquer section. The studied sequence includes variably metamorphosed submarine lavas, breccias, tuffs and dykes of basalt to andesite composition, and minor, shallow quartz microdiorite intrusives. A Campanian age is recorded by radiolarian faunas from chert strata capping the lavas. Two different tholeiitic suites and a younger calc-alkaline suite, represented by hornblende andesite, are distinguished. One tholeiitic suite, represented by plagioclase and pyroxene phyric lavas, evolves from basalt to basaltic andesite. It is characterized by the occurrence of diopsidic pyroxene as early crystallising phase, by depletion in high-field strength elements, particularly Nb and by relative enrichment in light REE and Th. The second tholeiitic suite, which includes aphyric or poorly phyric lavas of basalt to dacite composition, differs from the first group in having moderately low {FeO tot}/{MgO} ratio and lower P 2O 5 content for a given SiO 2, and higher {Ti}/{Zr}and{Y}/{Zr} ratios. The pyroxene chemistry of the two suites also differs. The primary geochemical characteristics of the two suites suggest a similarity with tholeiitic suites generated in island-arc environment. The hornblende andesite has mineralogical and chemical characteristics of calc-alkaline lavas erupted in an oceanic setting in an evolved island-arc. Petrologic and geochemical evidence suggests that the volcanic rocks from the Ricaurte-Altraquer section are similar to the island-arc tholeiite volcanics from the upper Macuchi Formation of northern Ecuador and can be correlated partly with this unit. Conversely, they are petrochemically dissimilar from the typical Diabase Group volcanic rocks, characterized by transitional MORB lavas, extensively present to the north in the Western Cordillera of Colombia.

  14. Coarse Grain Progradation in a Foreland basin: Application of Detrital Zircon Double Dating to Cenozoic Stratigraphy, Eastern Cordillera, Colombia.

    Science.gov (United States)

    Odoh, S.; Saylor, J. E.; Higuera-Diaz, C.; Lapen, T. J.; Copeland, P.

    2015-12-01

    Progradation of coarse clastic material into distal foreland basins has been attributed to both 1) enhanced sediment production during rapid tectonic exhumation and 2) sediment reworking during tectonic quiescence. The Floresta and Medina basins in the Eastern Cordillera record deposition of alternating coarse- and fine-grained clastic strata in medial and distal (respectively) Cenozoic foreland basins. The Medina Basin records the continued eastward progradation of the deformation front in the Neogene. We use detrital zircon U-Pb (ZPb) and (U-Th)/He (ZHe) analyses from the Paleogene Floresta Basin and the entire Cenozoic Medina Basin record to evaluate the effects of episodic thrust-belt exhumation and wide-spread deposition of coarse-grained sediments in the adjacent foreland basin. Both ZPb and ZHe systems are applied to individual grains (double dating) to constrain source area and up-section variations in exhumation rates. Changes in exhumation rate or introduction of new sediment sources are recorded as changes in lag time (ZHe age - depositional age). Analysis of 6 samples from the Floresta Basin shows a decrease in lag time during deposition of the coarse-grained middle Eocene Picacho Formation and upper Paleocene Socha Sandstone suggesting that Paleogene deposition of coarse-grained intervals in this medial location corresponds to an increase in exhumation rate. However, initial results from the Medina basin are less clear as there is evidence for Paleocene volcanic input but no clear evidence for thrust-belt related sediment until the Oligocene-early Miocene. We interpret the evidence for different sediment sources for Eocene strata in the axial Eastern Cordillera (Floresta) versus the Eastern foothills (Medina) as indicative of separation of these two regions by an emergent forebulge. Exhumation rate and granularity appear to be inversely correlated in post-Oligocene strata, though confirmation of initial interpretations awaits larger samples sizes

  15. CARACTERIZACIÓN FÍSIOGRÁFICA DE LA PUNA DE SAJAMA, CORDILLERA OCCIDENTAL DE LOS ANDES (BOLIVIA

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    Fernando Javier Santa Cecilia Mateos

    2015-01-01

    Full Text Available Este artículo aproxima a la realidad física de la cordillera Occidental de los Andes. Un espacio geográfico donde los caracteres geológicos relacionados con el vulcanismo adquieren una relevancia especial en la configuración del paisaje andino. Los nevados y llanuras intermedias o altiplanos, son los dos elementos que constituyen la imagen de la puna andina, un territorio situado por encima de los 4.000 metros, ámbito intermedio entre los valles húmedos o yungas y las más altas cumbres de los Andes. A la singularidad volcánica habría que añadir la relacionada con el modelado glaciar, los aspectos hidrográficos y la biogeografia en esta área. El artículo toma como ejemplo de estudio la puna de Sajama en eldepartamento de Oruro, en la frontera boliviano-chilena.Abstract. This article approaches the physical reality of the Western Cordillera of the Andes. A geographical space where characters related geological volcanism are of particular importance in shaping the landscape Andean. The intermediate plains or mountains and plateaus, are the two elements that make up the image of the Andean puna, an area located above 4,000 meters, the middle ground between Yungas wet valley and the highest peaks of the Andes. A volcanic uniqueness should add that related to glacier modeling, hydrographic aspects and biogeography in this area. The article uses the example of the highlands of Sajama study in thedepartment of Oruro in Bolivian-Chilean border.

  16. Glacial and periglacial geomorphology and chronology around the Nevado de Chañi (Cordillera Oriental of Jujuy): implication for past climate in NW Argentina

    Science.gov (United States)

    Martini, M. A.; Strelin, J. A.; Kaplan, M. R.; Schaefer, J. M.

    2012-12-01

    steep active eroding valley walls. The minimum altitude and the local topographic context suggest that changes in the activity of rock glaciers correspond with local conditions (e.g., debris or talus supply) rather than climatic changes (e.g., temperature) around Chañi. Our geomorphological-based findings allow us to propose a preliminary correlation with other glaciated areas in the arid Andes and the northern Cordillera Oriental and with lake transgression phases recorded on the southern Bolivian Altiplano, during the late Pleistocene. The paleo-equilibrium line altitudes rise from east to west across the region indicating that the source of moisture came from the east and northeast during the past glaciations, which is similar to the present-day circulation scenarios along the north side of the Arid Diagonal.

  17. Cenozoic forearc basin sediments in Southern Peru (15-18°S): Stratigraphic and heavy mineral constraints for Eocene to Miocene evolution of the Central Andes

    Science.gov (United States)

    Decou, A.; von Eynatten, H.; Mamani, M.; Sempere, T.; Wörner, G.

    2011-05-01

    A large sedimentary forearc basin developed in Cenozoic times between the present-day Coastal Cordillera and the Western Cordillera of the Central Andes, called Moquegua basin in southern Peru. The basin is filled by Moquegua Group deposits (~ 50 to 4 Ma) comprising mostly siliciclastic mudstones, sandstones and conglomerates as well as volcanic intercalations. Several facies changes both, along orogenic strike and through time, are described and have led to subdivision into four sedimentary units (Moquegua A, B, C and D). In this paper we present a refined stratigraphic scheme of the Moquegua Group combined with the first provenance analysis of the Moquegua basin based on (i) semi-quantitative analysis of heavy mineral abundance, (ii) electron microprobe (EMP) and laser ablation (LA) ICP-MS analyses of single detrital amphibole and Fe-Ti oxide grains, and (iii) comparative analysis of the different potential source rocks to clearly identify the most likely sources. Results allow us to reconstruct sediment provenance and to relate changes of the erosion-sedimentation system in the Moquegua basin to the evolution of the Andean orogen. At ~ 50 to ~ 40 Ma the Moquegua basin was close to sea level and fed by low energy rivers transporting mainly metamorphic basement and Jurassic-Cretaceous sedimentary detritus from local and distal sources. The latter might be as far as the present Eastern Cordillera. From ~ 35 Ma on the distal sediment sources were cut off by the uplift of the Altiplano and Eastern Cordillera leading to higher energy fluvial systems and increasing importance of local sources, especially the relevant volcanic arcs. From 25 Ma on volcanic arc rocks became the predominant sources for Moquegua Group sediments. The 10 Ma time lag observed between the onset of uplift-induced facies and provenance changes (at ~ 35 Ma) and the onset of intense magmatic activity (at ~ 25 Ma) suggests that magmatic addition was not the main driver for crustal thickening and

  18. The High Andean Cordillera of central Argentina and Chile along the Piuquenes Pass-Cordon del Portillo transect: Darwin's pioneering observations compared with modern geology La Alta Cordillera de los Andes del centro de Argentina y Chile a lo largo de la transecta del Paso Piuquenes-Cordón del Portillo: Las observaciones pioneras de Darwin comparadas con la geología moderna

    Directory of Open Access Journals (Sweden)

    Laura Giambiagi

    2009-04-01

    Full Text Available The geological observations made by Darwin in 1835 during his crossing of the Andes from Santiago to Mendoza via the Piuquenes Pass and Cordón del Portillo are compared with the present geological knowledge of the Cordillera Principal and Cordillera Frontal at 33°-34°S. The analysis of the complex stratigraphy of the Cordillera Principal, the imbricated structure of the Aconcagua fold and thrust belt, as well as the stratigraphy and structure of the inter mountain foreland Tunuyán Basin, allows to assess the pioneer observations of Darwin. He recognized the old metamorphic basement and the granitoids and volcanic sequences of late Paleozoic to Triassic age of the Cordillera Frontal, established the Cretaceous age of the marine successions cropping out along the eastern Cordillera Principal and studied the conglomeratic deposits associated with the uplift of the Cordillera in the Alto Tunuyán Basin. Based on the study of clast provenance of the synorogenic deposits of the Alto Tunuyán Basin, Darwin recognized that the Cordillera Frontal was uplifted later than the Cordillera Principal. The present knowledge of this sector of the Andean Cordillera confirms his pioneer observations and show that Darwin was one of the first scientists ever in realizing that in an orogenic system the sequence of uplift and deformation proceeds from hinterland towards foreland, according to a process that is exceptionally well-illustrated along the Piuquenes-Cordón del Portillo transect.Las observaciones geológicas efectuadas por Darwin en 1935 durante su cruce de la Cordillera de Los Andes entre Santiago y Mendoza realizado en 1835 a través de los pasos del Portillo y Piuquenes son examinadas y comparadas con el conocimiento actual existente de las Cordilleras Principal y Frontal entre los 33°-34°S. El análisis de la compleja estratigrafía de la Cordillera Principal, la estructura de las diferentes láminas imbricadas de la faja plegada y corrida del

  19. Normal Faulting at the Western Margin of the Altiplano Plateau, Southern Peru

    Science.gov (United States)

    Schildgen, T. F.; Hodges, K. V.; Whipple, K. X.; Perignon, M.; Smith, T. M.

    2004-12-01

    Although the western margin of the Altiplano Plateau is commonly used to illustrate the marked differences in the evolution of a mountain range with strong latitudinal and longitudinal precipitation gradients, the nature of tectonism in this semi-arid region is poorly understood and much debated. The western margin of the Altiplano in southern Peru and northern Chile marks an abrupt transition from the forearc region of the Andes to the high topography of the Cordillera Occidental. This transition has been interpreted by most workers as a monocline, with modifications due to thrust faulting, normal faulting, and gravity slides. Based on recent fieldwork and satellite image analysis, we suggest that, at least in the semi-arid climate of southern Peru, this transition has been the locus of significant high-angle normal faulting related to the block uplift of the Cordillera Occidental. We have focused our initial work in the vicinity of 15\\deg S latitude, 71\\deg W longitude, where the range front crosses Colca Canyon, a major antecedent drainage northwest of Arequipa. In that area, Oligocene to Miocene sediments of the Moquegua Formation, which were eroded from uplifted terrain to the northeast, presently dip to the northeast at angles between 2 and 10º. Field observations of a normal fault contact between the Moquegua sedimentary rocks and Jurassic basement rocks, as well as 15-m resolution 3-D images generated from ASTER satellite imagery, show that the Moquegua units are down-dropped to the west across a steeply SW-dipping normal fault of regional significance. Morphology of the range front throughout southern Peru suggests that normal faulting along the range front has characterized the recent tectonic history of the region. We present geochronological data to constrain the timing of movement both directly from the fault zone as well as indirectly from canyon incision that likely responded to fault movement.

  20. Plantas Fósiles del Grupo Choiyoi, Cordillera Frontal a la Latitud del río Mendoza Fossil plants from the Choiyoi Group, Frontal Cordillera at the latitude of the Mendoza River

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    Magdalena Koukharsky

    2011-06-01

    Full Text Available En este trabajo se dan a conocer los primeros restos fósiles hallados en sedimentitas, cuyo componente clástico es de origen volcánico, intercaladas en la Formación Tambillos del Grupo Choiyoi, Cordillera Frontal de Mendoza. Los mismos consisten en abundantes improntas de Sphenophyta en estado de preservación regular a malo. En la zona estudiada, las rocas de la Formación Tambillos, que son dominantemente volcánicas ácidas y de edad pérmica temprana a media según correlaciones regionales, se depositaron sobre una discordancia erosiva labrada en lavas andesíticas intensamente propilitizadas que se atribuyen a la Formación Portezuelo del Cenizo. Los restos vegetales se encuentran a unos 23 metros de la base, contenidos en niveles de areniscas finas y pelitas depositadas en un ambiente fluvial (microdelta, en los bordes de un lago y fueron coetáneas con los primeros episodios de volcanismo riolítico en la región. Si bien la flora encontrada no permite definir la edad, las formas presentes son comunes en niveles del Carbonífero superior-Pérmico y Triásico de Argentina.In this contribution we report the discovery of the first fossil remains in sedimentary strata belonging to the Tambillos Formation, Choiyoi Group, Cordillera Frontal of Mendoza. In the studied area the Tambillos Formation, which is formed dominantly by acid volcanics rocks of alleged Early to the Middle Permian, were deposited over an erosive unconformity on top of propilytic andesites of the Portezuelo del Cenizo Formation. The vegetal remains were found about 23 meters from the base of the formation, hosted in fine-grained sandstones and shales that were deposited in a fluvial environment (microdelta, along the borders of a lake during the first episodes of the rhyolitic volcanism of the region. The fossil flora includes abundant, poorly preserved impressions of Sphenophyta that does not permit to assign a precise age, although these forms are common in the Upper

  1. Flujos de detritos recientes en la cordillera frontal de Mendoza: Un ejemplo de riesgo natural en la ruta 7 Recent debris flows in the Frontal Cordillera of Mendoza: an example of natural risk on the Road 7

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    Emmanuel Wick

    2010-06-01

    Full Text Available Se expone un estudio sobre los flujos de detritos ocurridos en enero de 2005, en el km 1.118,5 de la ruta nacional 7 en la provincia de Mendoza. La zona se ubica en la Cordillera Frontal, próxima al límite con la Precordillera. Se realizó un mapa geomorfológico detallado, sobre la base de una imagen Quickbird del año 2006. Además, se hicieron cálculos de volúmenes, velocidades y caudales, con mediciones en el campo y con ayuda de un sistema de información geográfico (SIG. El estudio de la geomorfología permitió proponer tres escenarios para el caso de un nuevo evento, a partir de los cuáles se creó un mapa de susceptibilidad a los flujos de detritos para el tramo de ruta analizado. Finalmente, se proponen medidas de protección y de mitigación ante la posibilidad de recurrencia de estos eventos en el sector.In this paper is presented a study dealing with the debris flows that reached the national road 7 in January 2005, in the km 1,118.5, Mendoza province. The area is located in the Frontal Cordillera near the limit of the Precordillera. A detailed geomorphologic map has been realized for this study using a Quickbird satellite imagery of the year 2006. Various calculations of volumes, velocities and peak discharges have been performed with the field data and using a geographic information system (GIS. The geomorphologic survey has permitted to propose three propagation scenarios in case of a new event. These allowed creating a map of debris flows susceptibility for the stretch of the road that has been studied. Finally, it has been proposed protection and mitigation measures, based on the results of the study, to protect the road from a new event.

  2. ANÁLISIS MORFOLÓGICO DE LAS ESPORAS DE SERPOCAULON (POLYPODIACEAE DE LA CORDILLERA CENTRAL DE COLOMBIA

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    Ramírez-valencia Valentina

    2013-07-01

    Full Text Available Serpocaulon A. R. Sm. es un género monofilético de Polypodiaceae, compuesto por42 especies neotropicales, cuya mayor riqueza de especies se encuentra en Colombia,principalmente en la Cordillera Central (21 taxones. Su delimitación infragenéricaaún no es precisa, debido a: a problemas nomenclaturales, b el desconocimiento desu distribución geográfica, c su diversidad y d los múltiples eventos de hibridaciónpresentes en el género. Con el fin de incrementar el conocimiento taxonómico deSerpocaulon, se describió la morfología de las esporas de 21 taxones registrados enla Cordillera Central de Colombia, a partir de microscopía de luz transmitida-MLT yelectrónica de barrido-MEB. Los especímenes analizados fueron obtenidos de herbariosregionales. Se evaluaron 15 caracteres morfológicos y se promediaron 25 esporas envista lateral y 25 en vista proximal por taxón. Se realizó un análisis de componentesprincipales (ACP con el fin de identificar la variabilidad de los taxones. Se registraronesporas mónadas, heteropolares, con simetría bilateral, y formas elipsoidales, subelipsoidalesa globulares en vista proximal y plano-convexas a cóncavo-convexas envista lateral. Todos los taxones estudiados presentan ornamentación verrugada, quevaría en tamaño, forma y distribución. Se observaron dos tipos de perisporio (plegadoy liso. Los resultados sugieren que las verrugas son un importante carácter en ladeterminación de las especies, así como en su definición infragenérica, y que el ACPes útil para identificar algunos patrones morfológicos. Finalmente, se sugieren cuatrogrupos morfológicos conformados por especies que coinciden con clados propuestospreviamente en estudios moleculares.

  3. ARTE EN LA ZONA DE HISTÉRESIS: QUEBRADA. LAS CORDILLERAS EN ANDAS DE GUADALUPE SANTA CRUZ Art in the Zone of Hysteresis: Quebrada. Las cordilleras en andas, by Guadalupe Santa Cruz

    Directory of Open Access Journals (Sweden)

    Cecilia Ojeda

    2007-12-01

    Full Text Available Este libro de Guadalupe Santa Cruz plantea el problema del desmedrado estatus del arte en un horizonte cultural dominado por la industria del entretenimiento. De este reconocimiento y del diseño vanguardista del libro en sí -concebido como un puente entre el arte y la vida, o como un instrumento de conocimiento privilegiado de lo real- surge una tensión característica del arte contemporáneo. Dicha tensión ha sido definida como el punto de histéresis de la obra artística en la que ésta tiende a conservar una propiedad en ausencia del estímulo que la ha generado, tensión artística que se examina en este ensayo.Quebrada. Las cordilleras en andas examines the issue of the artwork’s diminished status within a landscape dominated by the entertainment industry. From this knowledge and the vanguard design of the book itself -as an instrument of the real-arises a tension that is characteristic of contemporary art. This tension has been compared to the point of hysteresis of an element, in which like a magnetic material it, the work of art, preserves one of its properties in the absence of its stimulus. This essay examines how this tension is produced in the work by Guadalupe Santa Cruz.

  4. GPS crustal deformation of the Eastern Betics and its relationship with the Lorca earthquake; Deformacion cortical de las Beticas Orientales observada mediante GPS y su relacion con el terremoto de Lorca

    Energy Technology Data Exchange (ETDEWEB)

    Echeverria, A.; Khazaradze, G.; Asensio, E.; Garate, J.; Surinach, E.

    2012-07-01

    On May 11{sup t}h of 2011, a seismic series occurred near the city of Lorca (Murcia). The main earthquake of magnitude Mw 5.2 has been attributed to the Alhama de Murcia Fault, one of the most active faults in the SE Iberian Peninsula. We analyzed data from 5 GPS campaigns of the CuaTeNeo network conducted between 1997 and 2011. The velocities of the stations closest to the Alhama de Murcia Fault show the reverse and strike-slip direction of motion. Stations located on the southeastern side of the fault have the maximum velocities in the area (between 1.4 and 1.8 mm/yr), oriented towards NNW direction, obliquely to the trace of the fault. The kinematics of the fault and the strain rate directions obtained from the CuaTeNeo network GPS measurements matches the calculated focal mechanism of Lorca earthquake. Detailed analysis of the time-series from the continuous GPS station at the Lorca city allows the detection of co-seismic offset of {approx}6 mm to the North. Keywords: crustal deformation, GPS, Betics, Lorca earthquake. (Author) 20 refs.

  5. Geomorphic analysis of the Sierra Cabrera, an active pop-up in the constrictional domain of conjugate strike-slip faults: The Palomares and Polopos fault zones (eastern Betics, SE Spain)

    Science.gov (United States)

    Giaconia, Flavio; Booth-Rea, G.; Martínez-Martínez, J. M.; Azañón, J. M.; Pérez-Peña, J. V.

    2012-12-01

    The NNE-SSW sinistral Palomares and the conjugate dextral WNW-ESE striking Polopos fault zones terminate in the Sierra Cabrera antiform. In order to test the Quaternary activity and topographic relief control in the termination of these fault zones, here we present new qualitative and quantitative geomorphic analyses supported by a new structural map of the region. The main mountain fronts of the Cabrera antiform are formed by the North and South Cabrera reverse faults that merge laterally into the Palomares and Polopos faults, respectively. These faults produce knickpoints, stream deflections, complex basin hypsometric curves, high SLk anomalies and highly eroded basins in their proximity. Furthermore, the drainage network shows an S-shaped pattern reflecting progressive anticlockwise rotation related to the sinistral Palomares fault zone. The estimated uplift rates determined by the integration between mountain front sinuosity index and valley floor width to height ratio are larger than those obtained for strike-slip faults in the eastern Betics. These larger uplift rates with our geomorphic and structural dataset indicate that the topographic relief of the Sierra Cabrera antiform is controlled by reverse faults that form a pop-up structure in the constrictional domain between the larger Palomares-Polopos conjugate strike-slip faults. Existing GPS geodetic data suggest that the North and South Cabrera reverse faults probably accommodate a large part of Africa-Iberia convergence in the region.

  6. Mantle to Surface Fluid Transfer Above a Flat Slab Subduction Zone: Isotopic Evidence from Hot Springs in the Cordillera Blanca, Peru

    Science.gov (United States)

    Newell, D. L.; Jessup, M. J.; Hilton, D. R.; Shaw, C. A.; Hughes, C. A.

    2015-12-01

    Thermal springs in the Cordillera Blanca, Peru, provide geochemical evidence for deeply circulated hydrothermal fluids that carry significant mantle-derived helium. The Cordillera Blanca is a ~200 km-long NNW-SSE trending mountain range in the Peruvian Andes located above an amagmatic flat-slab subduction segment. The west side of the range is bounded by the Cordillera Blanca detachment that preserves a progression of top to the west ductile shear to brittle normal faulting since ~5 Ma. We report aqueous and stable isotope geochemical results from fluid and gas samples collected in 2013 and 2015 from 13 hot springs emanating from the Cordillera Blanca detachment and associated hanging wall faults. Most springs are vigorously bubbling (degassing), and range in temperature, pH, and conductivity from 17-89 °C, 5.95-8.87, and 0.17-21.5 mS, respectively. The hottest springs issue directly from the northern segment of the detachment. Geochemically, springs are CO2-rich, alkaline-chloride to alkaline-carbonate waters, with elevated trace metal contents including Fe, Cu, As, Zn, Sb, and Tl. Notably, As contents are ≤11 ppm, indicating that thermal waters may be adversely impacting local water quality. Water δ18O and δD, trends in elemental chemistry, and cation geothermometry collectively demonstrate mixing of hot (200-260 °C) saline fluid with cold meteoric recharge along the fault. Helium isotope ratios (3He/4He) for dissolved gases in the hot springs range from 0.62 to 1.98 RC/RA, indicating the presence of ~25% mantle-derived helium, assuming mixing of an asthenospheric end-member with the crustal helium reservoir. CO2/3He and carbon stable isotope ratios indicate a carbon source derived from mixing of crustal sources with minor mantle carbon. Overall, the volatile signature overlaps with orogen-wide datasets where crustal overprinting has modified mantle contributions at active arc volcanoes. Given the long duration since active magmatism in the Cordillera

  7. Distributed ice thickness and glacier volume in southern South America

    Science.gov (United States)

    Carrivick, Jonathan L.; Davies, Bethan J.; James, William H. M.; Quincey, Duncan J.; Glasser, Neil F.

    2016-11-01

    South American glaciers, including those in Patagonia, presently contribute the largest amount of meltwater to sea level rise per unit glacier area in the world. Yet understanding of the mechanisms behind the associated glacier mass balance changes remains unquantified partly because models are hindered by a lack of knowledge of subglacial topography. This study applied a perfect-plasticity model along glacier centre-lines to derive a first-order estimate of ice thickness and then interpolated these thickness estimates across glacier areas. This produced the first complete coverage of distributed ice thickness, bed topography and volume for 617 glaciers between 41°S and 55°S and in 24 major glacier regions. Maximum modelled ice thicknesses reach 1631 m ± 179 m in the South Patagonian Icefield (SPI), 1315 m ± 145 m in the North Patagonian Icefield (NPI) and 936 m ± 103 m in Cordillera Darwin. The total modelled volume of ice is 1234.6 km3 ± 246.8 km3 for the NPI, 4326.6 km3 ± 865.2 km3 for the SPI and 151.9 km3 ± 30.38 km3 for Cordillera Darwin. The total volume was modelled to be 5955 km3 ± 1191 km3, which equates to 5458.3 Gt ± 1091.6 Gt ice and to 15.08 mm ± 3.01 mm sea level equivalent (SLE). However, a total area of 655 km2 contains ice below sea level and there are 282 individual overdeepenings with a mean depth of 38 m and a total volume if filled with water to the brim of 102 km3. Adjusting the potential SLE for the ice volume below sea level and for the maximum potential storage of meltwater in these overdeepenings produces a maximum potential sea level rise (SLR) of 14.71 mm ± 2.94 mm. We provide a calculation of the present ice volume per major river catchment and we discuss likely changes to southern South America glaciers in the future. The ice thickness and subglacial topography modelled by this study will facilitate future studies of ice dynamics and glacier isostatic adjustment, and will be important for projecting water resources and

  8. On the lag time between internal strain and basement involved thrust induced exhumation: The case of the Colombian Eastern Cordillera

    Science.gov (United States)

    Mora, Andrès; Blanco, Vladimir; Naranjo, Julian; Sanchez, Nelson; Ketcham, Richard A.; Rubiano, Jorge; Stockli, Daniel F.; Quintero, Isaid; Nemčok, Michal; Horton, Brian K.; Davila, Hamblet

    2013-07-01

    Thrust sheets accumulate internal strain before they start moving along discrete fault planes. However, there are no previous studies evaluating the time difference between initiation of strain and fault displacement. In this paper we use observations from the Eastern Cordillera of Colombia to evaluate this interval. We utilize multiple thermochronometers and paleothermometers to refine the timing of deformation. Based on these new data we build time-temperature path estimates that together with geometric outcrop-based structural analysis and fluid inclusions allow us to assign relative timing to features associated with strain, such as cleavage, veins and certain types of fractures, and compare that with the timing of thrusting. We find that cleavage was only formed close to maximum paleotemperatures, almost coeval with the onset of thrust-induced denudation by the Late Oligocene. The corresponding structural level of fold-related veins suggest that they were formed later but still when the country rocks were at temperatures higher than 160 °C, mostly during the Early Miocene and still coexisted with the latest stages of cleavage formation. Our data show that the main period of strain hardening was short (probably a few million years) and occurred before first-order basement thrusting was dominant, but was associated with second-order folding.

  9. Late Quaternary Glacial Chronology in the Cordillera de Talamanca, Costa Rica, Investigated Using Cosmogenic Cl-36 Surface Exposure Dating

    Science.gov (United States)

    Li, Y.; Potter, R.; Horn, S.; Orvis, K. H.

    2015-12-01

    The role of the tropics in past and future climate change has garnered significant attention in recent decades, but debate still exists over climate linkages between the tropics and the middle and high latitudes. Glaciers in tropical mountains are highly sensitive indicators of climate, and glacial landforms left behind by past glacier fluctuations provide key evidence of paleoclimate trends and their forcing mechanisms. We investigated late Quaternary glacial chronology from two glaciated valleys on the Chirripó massif in the Cordillera de Talamanca, Costa Rica. Previous studies in this highland have constrained the most recent deglaciation to 12.4-9.7 ka cal BP based on radiocarbon dates on basal sediments of glacial lakes within the cirque at the head of the Morrenas Valley. However, no studies have been conducted to constrain the ages of the moraines located down valley. We dated the formation ages of these moraines in the Morrenas and Talari valleys using cosmogenic Cl-36 surface exposure dating. Our results indicate a major glacial event ~21-18 ka, broadly synchronous with the global Last Glacial Maximum (LGM). Glaciers during this period advanced 3.2-3.4 km down valley on both sides of the Chirripó massif. Our ages also suggest periods of glacial retreat or standstills ~18-10 ka before complete deglaciation of this highland ~10 ka. These results provide insight into the timing and extent of glacial events in this tropical highland that is of critical importance for reconstructing regional and global climate patterns.

  10. Flujos de detritos recientes en la cordillera frontal de Mendoza: Un ejemplo de riesgo natural en la ruta 7

    Directory of Open Access Journals (Sweden)

    Emmanuel Wick

    2010-06-01

    Full Text Available Se expone un estudio sobre los flujos de detritos ocurridos en enero de 2005, en el km 1.118,5 de la ruta nacional 7 en la provincia de Mendoza. La zona se ubica en la Cordillera Frontal, próxima al límite con la Precordillera. Se realizó un mapa geomorfológico detallado, sobre la base de una imagen Quickbird del año 2006. Además, se hicieron cálculos de volúmenes, velocidades y caudales, con mediciones en el campo y con ayuda de un sistema de información geográfico (SIG. El estudio de la geomorfología permitió proponer tres escenarios para el caso de un nuevo evento, a partir de los cuáles se creó un mapa de susceptibilidad a los flujos de detritos para el tramo de ruta analizado. Finalmente, se proponen medidas de protección y de mitigación ante la posibilidad de recurrencia de estos eventos en el sector.

  11. Plantas Fósiles del Grupo Choiyoi, Cordillera Frontal a la Latitud del río Mendoza

    Directory of Open Access Journals (Sweden)

    Magdalena Koukharsky

    2011-06-01

    Full Text Available En este trabajo se dan a conocer los primeros restos fósiles hallados en sedimentitas, cuyo componente clástico es de origen volcánico, intercaladas en la Formación Tambillos del Grupo Choiyoi, Cordillera Frontal de Mendoza. Los mismos consisten en abundantes improntas de Sphenophyta en estado de preservación regular a malo. En la zona estudiada, las rocas de la Formación Tambillos, que son dominantemente volcánicas ácidas y de edad pérmica temprana a media según correlaciones regionales, se depositaron sobre una discordancia erosiva labrada en lavas andesíticas intensamente propilitizadas que se atribuyen a la Formación Portezuelo del Cenizo. Los restos vegetales se encuentran a unos 23 metros de la base, contenidos en niveles de areniscas finas y pelitas depositadas en un ambiente fluvial (microdelta, en los bordes de un lago y fueron coetáneas con los primeros episodios de volcanismo riolítico en la región. Si bien la flora encontrada no permite definir la edad, las formas presentes son comunes en niveles del Carbonífero superior-Pérmico y Triásico de Argentina.

  12. Zircon-apatite U-Pb geochronology, zircon Hf isotope composition and geochemistry of granite batholith in the northern Mexico: Implications for Tectonomagmatic evolution of southern Cordillera.

    Science.gov (United States)

    Mahar, M. A.; Goodell, P.

    2015-12-01

    We present the zircon-apatite U-Pb ages and zircon Hf isotope composition of the granite batholith exposed at the western boundary of Chihuahua. Granidiorite samples were analyzed from both, north and south of the Rio El Fuerte and Sinforosa Lineament. Based on previous studies, the WWN-EES trending Sinforosa Lineament is proposed as the manifestation of a terrane boundary between Seri in the north and Tahue terrane in the south. Zircon U-Pb data indicate that the magmatism spans a time period of 36 Ma from 89 to 53 Ma to the north of the Sinforosa Lineament while granodiorites in the south of the Sinforosa Lineament are dated at 59 Ma. The U-Pb apatite ages are variable in the north of the Sinforosa Lineament and range from 86-51 Ma. These apatite dates are 1-28 Ma younger than the corresponding zircon U-Pb crystallization ages. This indicates variable cooling rates and moderate to shallow emplacement. In contrast, in the south of the Sinforosa Lineament, the U-Pb apatite ages (64-59 Ma) are indistinguishable from the zircon U-Pb age (59 Ma), indicating rapid cooling and shallow emplacement. Zircon morphology and U-Pb dating revealed the absence of inherited component in the zircon ages, as no inheritance of any age has been observed. Most of the northwestern Mexico is underlain by Precambrian-Paleozoic-Jurassic basement. However, in the study area, U-Pb dating does not support the involvement of the older basement in generating the granite magmas. The weighted mean initial ɛHf (t) isotope composition of granodiorites on both sides of the Sinforosa Lineament varies from +2 to +5. However, Hf isotope composition in the south of the Sinforosa Lineament is more heterogeneous and relatively evolved with weighted Mean ɛHf (t) = +1.45. The Hf isotope composition is consistent with the previously reported near bulk silicate Sr-Nd isotope values. We suggest that the magmatic rocks in this region are not derived from melting of a felsic older crust beneath the batholith. Instead, the magmatism is related to the mildly radiogenic arc system in the northwestern Mexico. However, partial melting of sub continental mantle wedge cannot be ruled out. The difference in U-Pb ages and initial Hf isotope composition implies that the Sinforosa Lineament might be a refined boundary between the Seri and Tahue Terranes.

  13. Upper plate deformation and seismic barrier in front of Nazca subduction zone : the Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

    OpenAIRE

    Audin, Laurence; Lacan, P.; Tavera, H.; Bondoux, Francis

    2008-01-01

    The South America plate boundary is one of the most active subduction zone. The recent Mw=8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, ...

  14. U/Pb ages on detrital zircons in the southern central Andes Neogene foreland (36°-37°S): Constraints on Andean exhumation

    Science.gov (United States)

    Sagripanti, Lucía; Bottesi, Germán; Naipauer, Maximiliano; Folguera, Andrés; Ramos, Victor A.

    2011-12-01

    U/Pb dating on detrital zircons was performed in the Pampa de Carrizalito depocenter of the Late Miocene foreland basin associated with the Southern Central Andes orogenic front. This reveals Andean and pre-Andean components in magmatic derived zircons inhomogeneously distributed through the sequence. Andean, Grenville, Pampean, Famatinian and Gondwanic components reveal a complex source distribution from either the Main Andes, Coastal Cordillera and basement foreland areas. These are discussed showing different patterns in the context of the Andean orogenic cycle. Cretaceous and Jurassic components that are partly related to Mesozoic batholiths, developed at the western slope of the Andes at these latitudes, have a very contrasting behavior through the sequence: While Jurassic grains are represented from base to top, Cretaceous ones dilute upwardly. This is explained through the progressive uplift of the Southern Central Andes that could have created a barrier to Cretaceous and Jurassic detritus, while the older ones could have had either an alternative source area represented by the inverted rift system of the Huincul Ridge in the foreland area and the Cordillera del Viento in the hinterland area or the reworking of Jurassic sedimentary sequences of the Neuquén basin. Finally, a progressive enrichment in pre-Andean components to the top of the sequence is interpreted as related to the development of a broken foreland and the consequent rapid expansion of the orogenic front at the time of development of a slab shallowing setting in the region as shown by previous works.

  15. Calculo Preliminar de la Tasa de Meteorización del Batolito Antioqueño, Cordillera Central, Colombia

    Directory of Open Access Journals (Sweden)

    Carolina Garcia

    2004-12-01

    Full Text Available Este trabajo es una estimación preliminar del tiempo necesario para generar la espesa capa de saprolito que caracteriza el perfil de meteorización actual de un batolito cuarzodiorítico cretácico que aflora en altiplanos de la Cordillera Central de Colombia, entre 5º50' y 7º00' de latitud Norte y 74º50' y 75º35' de longitud Oeste y a alturas entre 750 y 2700 m.Se utilizan datos obtenidos previamente mediante el análisis de la composición química de las aguas superficiales de cuatro cuencas con áreas diferentes, ubicadas sobre el Batolito Antioqueño, al este de Medellín. Los cáculos se hicieron con el método basado en la pérdida de componentes en solución utilizando diferentes valores de solutos. Al utilizar la pérdida de sílice se obtiene un tiempo de meteorización de unos 6 x 10 6 años, comparable con el obtenido mediante la datación de las cenizas volcánicas mas antiguas que recubren la topografía actual y que indican la fecha mínima de configuración de la superficie de erosión.A pesar de resultar de una serie de suposiciones simplificadoras, este resultado es interesante y justifica la realización de determinaciones mas detalladas. Confirma la larga preservación de superficies de erosión antiguas conformadas sobre un saprolito que desde hace varios millones de años no ha sido sometido a una erosión profunda, fenómeno poco común en una zona tectónicamente activa como la estudiada.

  16. Antisana volcano: A representative andesitic volcano of the eastern cordillera of Ecuador: Petrography, chemistry, tephra and glacial stratigraphy

    Science.gov (United States)

    Hall, Minard L.; Mothes, Patricia A.; Samaniego, Pablo; Militzer, Annemarie; Beate, Bernardo; Ramón, Patricio; Robin, Claude

    2017-01-01

    Antisana volcano is representative of many active andesitic strato-volcanoes of Pleistocene age in Ecuador's Eastern Cordillera. This study represents the first modern geological and volcanological investigation of Antisana since the late 1890's; it also summarizes the present geochemical understanding of its genesis. The volcano's development includes the formation and destruction of two older edifices (Antisana I and II) during some 400 + ka. Antisana II suffered a sector collapse about 15,000 years ago which was followed by the birth and growth of Antisana III. During its short life Antisana III has generated ≥50 eruptions of small to medium intensity, often associated with andesitic to dacitic lava flows and tephra, as well as with late Pleistocene and Holocene glacial advances. Throughout its long history Antisana's lavas have been characterized by a persistent mineral assemblage, consisting of 30-40 vol% phenocrysts of plagioclase, both clino- and orthopyroxene, and Fe-Ti oxides, with rare occurrences of olivine or amphibole, frequently in a microcrystalline to glassy matrix. This uniformity occurs despite the magma's progressive chemical evolution over ≥400 ka from early basic andesites (53-58 wt% SiO2) to intermediate and Si-rich andesites (58-62% SiO2), and recently to dacites (63-67% SiO2). Chemical diagrams suggest that crystal fractionation was the most likely magmatic process of evolution. The exception to this slowly evolving history was the short-lived emission at ∼210 ka of the Cuyuja lavas from Antisana II that generated a 73 km long andesitic lava flow. Contrasting with Antisana's general magmatic trend, Cuyuja lava (∼11 km3) is a high-Mg andesite with unusually high concentrations of incompatible elements. Antisana developed within the Chacana caldera complex, a large active siliceous center that began ∼3 Ma ago, however its lavas are chemically distinct from coeval lavas of Chacana.

  17. Late Pleistocene and Holocene Hydroclimate Variability in the Tropical Andes from Alpine Lake Sediments, Cordillera de Mérida, Venezuela

    Science.gov (United States)

    Larsen, D. J.; Abbott, M. B.; Polissar, P. J.

    2014-12-01

    The tropics play a major role in the global hydrologic cycle and changes to tropical rainfall patterns have critical implications for water resources and ecosystem dynamics over large geographic scales. In tropical South America, late Pleistocene and Holocene precipitation variability has been documented in geologic records and associated with numerous external and internal variables, including changes in summer insolation, South American summer monsoon strength, Pacific Ocean sea surface temperatures, continental moisture recycling, and other climate processes. However, there are few records from the northern hemisphere tropical Americas, a key region for understanding interhemispheric linkages and the drivers of tropical hydroclimate variability. Here, we present a ~13 ka record of coupled hydroclimate and environmental changes from Laguna Brava, a small (~0.07 km2), hydrologically closed lake basin situated at 2400 m asl in the Cordillera de Mérida, Venezuela. Sediment cores collected from varying water depths and proximity to shore are placed in a chronologic framework using radiocarbon ages from terrestrial macrofossils, and analyzed for a suite of physical, bulk geochemical, and stable isotopic parameters. Compound specific hydrogen isotope (D/H) measurements of terrestrial plant waxes (long-chain n-alkanes) show a sharp increase in the late Pleistocene, followed by a long-term trend toward more negative values that suggest a ~20‰ decrease in the D/H ratios of South American tropical precipitation during the Holocene. This pattern is consistent in sign and magnitude to other South American precipitation reconstructions from both hemispheres, indicating interhemispheric similarities in tropical hydroclimate variability. Superimposed on this continent-scale trend are changes in moisture balance and environmental conditions in the Venezuelan Andes. We reconstruct these parameters at Laguna Brava at multidecadal and centennial resolution and evaluate this

  18. Time-lapse and UAV Thermal Imaging of Glacial and Periglacial Environments in the Peruvian Andes (Cordillera Blanca, Peru)

    Science.gov (United States)

    McKenzie, J. M.; Wigmore, O.; Aubry-Wake, C.; Mark, B. G.; Hellstrom, R. A.; Lautz, L.

    2015-12-01

    In the tropics, the acquisition of high-resolution geospatial data of high-mountain glacial and periglacial systems presents unique challenges due to remote site access and very high elevations. For glaciers and hydrologic systems, a key variable of interest is surface temperature as it constrains glacier melt rates, traces hydrologic processes, and is needed for the calibration of energy budget models. We present results from two studies that acquired high resolution temperature data from the Cuchillacocha Glacier, Peru (9.24°S, 77.21°W). The glacier resides on the western drainage of the Cordillera Blanca with an elevation range of 4700 to 6096 m. In the first study we use high resolution time-lapse infrared imagery (5-10 minute interval over 3 days; 0.6 m2 pixel size) to observe diel changes in the surface energy budget of the glacier and to demonstrate how radiation from bare rock adjacent to the glacier may affect melt rates. In the second study we use a newly developed, inexpensive unmanned aerial vehicle (UAV) for high resolution multispectral mapping of the glacier (2 cm resolution orthomosaic and 5 cm resolution DEM). We present results showing how the time-lapse and the high-resolution UAV imagery can be combined to further strengthen our understanding of the Cuchillacocha Glacier's energy budget and possible insights about turbulent heat fluxes. While the new instruments provide unprecedented data acquisition capabilities, there is an outstanding need for proper data correction. Spatial/thermal control points and post-processing algorithms are needed to produce quantifiable datasets. For example, our post-processed time-lapse imagery has an r2 > 0.9 after emissivity, transmissivity and offset corrections.

  19. Paleozoic evolution of active margin basins in the southern Central Andes (northwestern Argentina and northern Chile)

    Science.gov (United States)

    Bahlburg, H.; Breitkreuz, C.

    The geodynamic evolution of the Paleozoic continental margin of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American margin at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin

  20. Provenance through the limit: integrated provenance from the Devonian sedimentary and basement rocks from the northern segment of the Eastern Cordillera of the Colombian Andes

    Science.gov (United States)

    Cardona, Agustin; Valencia, Victor; Lotero, Andrea; Villafañez, Yohana; Augustsson, Carita; Bayona, German; Ibañez, Mauricio

    2013-04-01

    The provenance record of sedimentary rocks is sometimes the only available archive of the geological evolution in continuously active continental margins where continuous exhumation, erosion and along strike fragmentation of continental margins destroy geological evidences. New integrated provenance constraints from segmented exposures of Devonian rocks of the northern segment of the Eastern Cordillera of Colombia are used to reconstruct overimposed Paleozoic, Mesozoic and Cenozoic paleogeographic scenarios of the northern Andes. Sandstones from deltaic to platform environments are characterized by very high quartz contents, stable to ultrastable heavy minerals and mostly angular fragments. U-Pb detrital zircon geochronology reveals prominent Silurian to Ordovician and Mesoproterozoic (Grenvillian) age populations with minor Devonian zircons. Tourmaline geochemistry and detrital quarz characterization suggest prominent low grade metamorphic sources. These provenance fingerprints can be related to the erosion of the older metasedimentary basement exposed in the same region and record the transition from a terrane collisional event to the formation of a new subduction zone before the final Late Paleozoic events that end in the agglutination of Pangea. The U-Pb detrital record of the Devonian and basement rocks of the Eastern Cordillera are also comparable with Early to Middle Paleozic Paleozoic rocks form the Northern segment of the eastern Peruvian Andes re-inforcing the view of along strike terrane thousand of kilometer transport along the Mesozoic proto-Andean margin. Petrographic and heavy mineral petrofacies and stratigraphic correlation between Devonian localities are also used as piercing points to document Cenozoic ten of kilometers strike slip displacements along the northern termination of the Eastern Cordillera.

  1. Kinematic evolution of Andean fold-thrust structures along the boundary between the Eastern Cordillera and Middle Magdalena Valley basin, Colombia

    Science.gov (United States)

    SáNchez, Javier; Horton, Brian K.; Tesón, Eliseo; Mora, AndréS.; Ketcham, Richard A.; Stockli, Daniel F.

    2012-06-01

    Surface and subsurface data support a kinematic reconstruction of Cenozoic fold-thrust deformation along the Eastern Cordillera-Magdalena Valley transition in Colombia. The La Salina fault (LSF) marks the boundary between west-vergent Eastern Cordillera structures and hinterland deposits of the Middle Magdalena Valley basin. Apatite fission track and (U-Th)/He thermochronological results for the west-directed LSF reveal initial hanging wall exhumation during middle Eocene-early Oligocene (45-30 Ma) shortening, renewed exhumation in the early middle Miocene (18-12 Ma), and accelerated late Miocene-Pliocene (12-3 Ma) exhumation. Vitrinite reflectance data suggest maximum burial of 4-6 km, helping constrain Cenozoic basin architecture. Mapping of the LSF reveals hanging wall Cretaceous-Eocene rocks in a broad anticline-syncline pair with limited faulting and footwall Eocene-Quaternary basin fill in a complex series of tight thrust-related folds. Limited displacement along the westernmost (frontal) thrust suggests that shortening is largely accommodated by east-directed thrusting within a broader triangle zone of a passive-roof duplex (and probable minor strike-slip deformation). In the preferred kinematic restoration, the most recent phase of shortening to transpressional deformation represents out-of-sequence reactivation of the LSF consistent with irregular crosscutting relationships among footwall structures. Earliest exhumation by 45-30 Ma in the Eastern Cordillera fold-thrust belt is correlated with increased sedimentary lithic fragments and high compositional maturity in sandstones of the adjacent Magdalena Valley basin. Exhumation since ˜15 Ma coincided with decreased compositional maturity and elevated accumulation rates for the Real Group. The compositional provenance shifts are attributed to westward advance of fold-thrust deformation into the proximal (eastern) segments of the Magdalena Valley basin.

  2. Una especie nueva de rana arbórea del género Hyloscirtus (Amphibia: Anura: Hylidae de la Cordillera del Cóndor

    Directory of Open Access Journals (Sweden)

    Ana Almendáriz

    2014-01-01

    Full Text Available Las ranas ecuatorianas del género Hyloscirtus incluyen 16 especies descritas, de las cuales 11 pertenecen al grupo H. larinopygion. Su distribución se limita a los flancos de la Cordillera de los Andes, tanto al oriente como al occidente. Una evaluación de la herpetofauna en el sector meridional de la Cordillera del Cóndor (bosques montanos sobre mesetas de arenisca en la provincia de Zamora Chinchipe, Ecuador, condujo al descubrimiento de una especie nueva del grupo que describimos aquí como Hyloscirtus condor sp. nov.; se analizan los renacuajos, las llamadas de anuncio y se estima las relaciones filogenéticas de la especie nueva y de las especies relacionadas en base a nuevas secuencias de los genes mitocondriales 12S, tRNA Val y 16S, con un total de hasta 2508 bp. Los resultados muestran que el grupo H. larinopygion está conformado por dos clados, uno distribuido en los Andes norte y centro de Ecuador y el otro al sur. La nueva especie pertenece al clado sur y es hermana de H. tapichalaca y de una especie aparentemente no descrita de la Provincia Morona Santiago. La especie nueva difiere de sus congéneres por su patrón de coloración dorsal, que consiste de puntos amarillo obscuro en un fondo canela. Es la especie más grande del grupo H. larinopygion y comparte con H. tapichalaca la presencia de una espina prepólica grande y curvada y brazos hipertrofiados. La especie nueva habita un área remota y bien conservada de la Cordillera del Cóndor. El descubrimiento de ésta y otras especies nuevas del mismo lugar denota la importancia biológica del área y motivan al desarrollo de planes de conservación.

  3. The analysis of remote sensing data to delineate landsystem tracts in proglacial valleys in the Río Santa Basin, Cordillera Blanca, Perú

    Science.gov (United States)

    Narro Perez, R. A.; Eyles, C.

    2016-12-01

    The Río Santa Basin is an important glacially-influenced basin of social, economic and cultural importance to the country of Perú. It produces a large portion of Peru's hydroelectricity, is an important agricultural area, and hosts two major mining complexes. The Río Santa receives its water from precipitation, glacial runoff from over 450 glaciers draining the Cordillera Blanca, and groundwater discharge. Despite being the largest tropical glacier ice field in the world, the area of glacial coverage in the Cordillera Blanca has decreased from 825 km2 in 1930 to 528 km2 in 2003. It is estimated that glacial runoff contributes 10-20% of the Río Santa's annual flow but during the dry season it can contribute up to 66% of water flow with groundwater supplying the remainder. The contribution of glacial meltwater makes the Río Santa less susceptible to discharge variability caused by inter-annual variation in precipitation. Due to decreased meltwater contributions, the urban centers and rural communities in the basin are expected to face severe water scarcity in the future, especially during the dry season. This poster will show the results of a remote sensing survey, using Google Earth and LiDAR data, to delineate landsystem tracts and components in several proglacial valleys in the Cordillera Blanca. The results of this survey allow detailed documentation of the geomorphological evolution of the landscape which will in turn allow a better understanding of the glacial history and subsurface geology of the area. These findings will better inform current hydrogeological models used to determine the sustainability of water resources in the Río Santa basin. Understanding the landsystem architecture, sedimentology and subsurface stratigraphy of the basin will also allow these models to more accurately predict the impact that future climate change will have on water resources and the people of the Río Santa basin.

  4. Assessing the variability of glacier lake bathymetries and potential peak discharge based on large-scale measurements in the Cordillera Blanca, Peru

    Science.gov (United States)

    Cochachin, Alejo; Huggel, Christian; Salazar, Cesar; Haeberli, Wilfried; Frey, Holger

    2015-04-01

    Over timescales of hundreds to thousands of years ice masses in mountains produced erosion in bedrock and subglacial sediment, including the formation of overdeepenings and large moraine dams that now serve as basins for glacial lakes. Satellite based studies found a total of 8355 glacial lakes in Peru, whereof 830 lakes were observed in the Cordillera Blanca. Some of them have caused major disasters due to glacial lake outburst floods in the past decades. On the other hand, in view of shrinking glaciers, changing water resources, and formation of new lakes, glacial lakes could have a function as water reservoirs in the future. Here we present unprecedented bathymetric studies of 124 glacial lakes in the Cordillera Blanca, Huallanca, Huayhuash and Raura in the regions of Ancash, Huanuco and Lima. Measurements were carried out using a boat equipped with GPS, a total station and an echo sounder to measure the depth of the lakes. Autocad Civil 3D Land and ArcGIS were used to process the data and generate digital topographies of the lake bathymetries, and analyze parameters such as lake area, length and width, and depth and volume. Based on that, we calculated empirical equations for mean depth as related to (1) area, (2) maximum length, and (3) maximum width. We then applied these three equations to all 830 glacial lakes of the Cordillera Blanca to estimate their volumes. Eventually we used three relations from the literature to assess the peak discharge of potential lake outburst floods, based on lake volumes, resulting in 3 x 3 peak discharge estimates. In terms of lake topography and geomorphology results indicate that the maximum depth is located in the center part for bedrock lakes, and in the back part for lakes in moraine material. Best correlations are found for mean depth and maximum width, however, all three empirical relations show a large spread, reflecting the wide range of natural lake bathymetries. Volumes of the 124 lakes with bathymetries amount to 0

  5. The organic matter of the Potosi basin (Cordillera Oriental, Bolivia) during the Upper Cretaceous-Lower tertiary: stratigraphic and palaeogeographic data

    Energy Technology Data Exchange (ETDEWEB)

    Blanc-Valleron, M.M.; Rouchy, J.M. (Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France)); Schuler, M.; Rauscher, R. (Strasbourg-1 Univ., 67 (France)); Camoin, G. (Aix-Marseille-1 Univ., 13 - Marseille (France))

    1994-12-01

    Palynological and Rock-Eval pyrolysis studies of the Chaunaca and El Molino Fm (Santonian to Thanetian, Cordillera Oriental, Bolivia) indicate that some facies have economic significance as potential oil source rocks. The occurrence of Pediastrum and Azolla testify a lacustrine environment. In the Upper Molino, the environmental interpretation of an almost monospecific association of dinocysts is discussed. The presence of Apectodinium quinquelatum indicates that the age of the upper part of the Upper El Molino Fm is likely to be Upper Thanetian. (authors). 22 refs., 5 figs.

  6. Flora y vegetación de suelos crioturbados y hábitats asociados en la Cordillera Blanca, Ancash, Perú

    OpenAIRE

    2011-01-01

    Entre los años 2006 y 2008, se llevaron a cabo estudios florístico y de vegetación de los suelos crioturbados y hábitats asociados en cuatro localidades de la Cordillera Blanca (Ancash, Perú) localizadas por encima de los 4500 m. Se realizaron recolectas botánicas además de transectos de intersección-línea, en los cuales se midió el espacio (en cm) ocupado por cada especie. Fueron determinadas 136 especies de plantas vasculares, agrupadas en 65 géneros y 26 familias. Las Magnoliópsi...

  7. THE STRATIGRAPHY OF THE UPPER BATHONIAN TO MIDDLE OXFORDIAN SUCESSION OF THE ARAGONESE BRANCH OF THE CORDILLERA IBÉRICA (SPAIN AND ITS EUROPEAN CONTEXT

    Directory of Open Access Journals (Sweden)

    KEVIN N. PAGE

    2004-03-01

    Full Text Available The Upper Bathonian-Middle Oxfordian succession of the Aragonese branch of the Cordillera Ibérica is one of the most completely developed in Europe and includes localities of international importance for Jurassic bio- and chronostratigraphy. Of particular importance are a potential stratotype for the Upper Bathonian of North West Europe and reference sections for a number of Submediterranean Province Middle Oxfordian biostratigraphic units. The intervening Callovian sequence, albeit locally strongly condensed, also includes faunas of key stratigraphical importance. The sequence of stratigraphically important ammonite faunas for this interval is here reviewed and placed in its European context.

  8. X-ray color maps of the zoned garnets from Silgará Formation metamorphic rocks,SantanderMassif, Eastern Cordillera (Colombia

    Directory of Open Access Journals (Sweden)

    Takasu Akira

    2010-12-01

    Full Text Available

    The metamorphic rocks of the Lower Paleozoic Silgará Formation of the Santander Massif, Eastern Cordillera (Colombia, were affected by a Barrovian-type metamorphism under low to high temperature and medium pressure conditions. These rocks contain garnet porphyroblasts, which show several kinds of chemical zoning patterns. The garnet grains behave as closed systems with respect to the rock matrix. Most of the observed zoning patterns are due to gradual changes in physicochemical conditions during growth. However, some garnet grains show complex zoning patterns during multiple deformation and metamorphic events.

  9. Southern California Particle Center

    Data.gov (United States)

    Federal Laboratory Consortium — At the Southern California Particle Center, center researchers will investigate the underlying mechanisms that produce the health effects associated with exposure to...

  10. Efecto de la zona de vida y la altitud en la mortalidad y adaptabilidad al primer ano de especies forest ales en la cordillera volcanica central, Costa Rica

    Directory of Open Access Journals (Sweden)

    Yorleny Badilla

    2002-01-01

    Full Text Available Se presenta los resultados de la mortalidad y adaptabilidad a los 6 y 12 meses de edad, de las especies forestales cipres (Cupressus lusitanica, eucalipto de altura (Eucalyptus globulus, pino patula (Pinus patula, pino radiata (Pinus radia- fa, roble encino (Quercus coopeyensis,jaul (Al- nus acuminata, cedro dulce (Cedrela tonduzii y tirra (Ulmus mexicana. De cada especie fueron plantadas 4 repeticiones dentro de cada una de las 3 zonas de vida de mayor representatividade la Cordillera Volcanica Central de Costa Rica, predesde los 1000 a los 2000 m de altitud. Se regis- tro una tendencia de mayor mortalidad conforme aumento la pluviosidad. Las 3 especies confferas mostraron desde los 6 meses la menor mortalidad «15% y mayor estabilidad en todas las zonas de pluvida; presentaron un alto potencial de reforesta- cion en toda la Cordillera Volcanica Central. Las especies cella dulce, tirra y jaul conformaron un grupo de especies con una mortalidad elevada, que se estabiliz6 hasta el ano de plantadas. Las especies eucalipto de altura y fable conformaron el grupo de mayor mortalidad (>50% y de adap- tabilidad mas lenta. Sin embargo, el eucalipto de altura mostro un buen crecimiento en sitios plu- viales. Un mayor cuidado de la calidad del mate- adaptrial de reforestaci6n y el empleo de tecnicas de plantaci6n como los camellones, la aporca y el drenaje, son esenciales para poder reforestar en nurszonas de altura con una elevada pluviosidad.

  11. Mineralización de talco asociada a los cuerpos ultramáficos de la Faja del Río de Las Tunas, Cordillera Frontal de Mendoza

    Directory of Open Access Journals (Sweden)

    Gargiulo, María Florencia

    2011-12-01

    Full Text Available Talc mineralization related to the ultramafic bodies of the Río de Las Tunas belt, Frontal Cordillera of Mendoza province. This contribution shows the main characteristics of the talc mineralization related to the Río de Las Tunas ultramafic bodies in the Salamanca Mining District, Frontal Cordillera of Mendoza province. According to the parageneses defined on the studied samples, three generations of talc were established: 1º crystallized in metaperidotites and related to the prograde stage of the regional metamorphism; 2º crystallized inreaction zones (mostly in the talc zone developed at the boundary between metaperidotites and their country-rocks.These reaction zones evidence a metasomatic process due to geochemical gradient between the ultramafic body and their country-rocks. This process was developed during the retrogression of the regional metamorphic cycle. 3º Talc present in shear-zones that cut across the ultramafic bodies. The extreme serpentinization of the ultramaficbodies is concentrated in shear-zones where the serpentine is subsequently replaced by talc ± carbonates related with a hydrothermal stage. Aqueous fluids relatively enriched in CO2 flowed through these shear-zones causing the cease of serpentine formation favoring the talc and/or carbonates. Mined talc deposits are those in shear zones and reaction zones. They are mostly industrial-, asbestine- or talcschist-type. The talc related to the hydrothermal stage can locally reach first and extra qualities.

  12. Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach

    Science.gov (United States)

    May, Jan-Hendrik; Zech, Jana; Zech, Roland; Preusser, Frank; Argollo, Jaime; Kubik, Peter W.; Veit, Heinz

    Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating ( 14C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29-25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20-18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~ 17-16 ka, followed by several smaller readvances until ~ 10-11 ka, and complete deglaciation at the end of the Early Holocene.

  13. Mineralogía de los materiales de la Formación de La Viñuela (Cordilleras Béticas

    Directory of Open Access Journals (Sweden)

    Galán, E.

    1984-12-01

    Full Text Available Mineralogy of several samples from the Viñuela Formation,Lower Burdigalian (Vélez Málaga, Cordilleras Béticas, has been studied. Materials are composed of abundant microfauna. and pebbles of micaschits, quartzites and other materials, from the Alpujárrides and Maláguides Nappes, cemented by a micritic matrix . Most samples contain zeolites (clinoptilolite, mordenite and analcime, and illite chlorite, interstratified clay minerals, montmorillonite and opal C-T. A diagenetic genesis for zeolites is suggested.

    Se ha estudiado la composición mineralógica de unas muestras de la serie tipo de la Formación de La Viñuela (norte de Vélez Málaga, Cordilleras Béticas, datadas como Burdigaliense inferior. Se trata de sedimentos marinos carbonatados micríticos, con abundante microfauna. que cementan cantos de micaesquistos, cuarcitas y otros materiales procedentes de los mantos alpujárrides y maláguides. En gran parto de estas muestras se han encontrado zeolitas (clinoptilolita, mordenita y analcima, así como illita, clorita, interestratificados, montmorillonita y ópalo C-T. Se atribuye a las zeolitas un origen diagenético.

  14. Tracing society in climate change: Societal negotiations and physical dynamics of water under climate change conditions in the Cordillera Blanca region, Peru

    Science.gov (United States)

    Neuburger, Martina; Gurgiser, Wolfgang; Maussion, Fabien; Singer, Katrin; Kaser, Georg

    2017-04-01

    Natural scientists observe and project changes in precipitation and temperature at different spatio-temporal scales and investigate impacts on glaciers and hydrological regimes. Simultaneously, social groups experience ecological phenomena as linked to climate change and integrate them into their understanding of nature and their logics of action, while political actors refer to scientific results as legitimization to focus on adaptation and mitigation strategies on global, national and regional/local level. However, natural and socio-political changes on various scales (regarding time and space) are not directly interlinked, but are communicated by energy and material flows, by discourses, power relations and institutional regulations. In this context, it remains still unclear how natural dynamics are (dis)entangled with societal processes in their historical dimensions and in their interrelations from global via national to regional and local scales. Considering the Cordillera Blanca region in Peru as an example, we analyze the intertwining of scales (global, national, regional, local) and spheres (natural, political, societal) to detect entanglements and disconnections of observed processes. Using the methodology of a time line, we present precipitation variability and glacier recession at different scales, estimate qualitative water availability and investigate the links to the implementation of international and national political programs on climate change adaptation in the Cordillera Blanca region focusing on water and agrarian programs. Finally, we include supposedly contradictory reports of rural population on climate change and related impacts on water availability and agricultural production to analyze the (dis)entanglement due to changing power relations and dominant discourses.

  15. Niche shifts and range expansions along cordilleras drove diversification in a high-elevation endemic plant genus in the tropical Andes.

    Science.gov (United States)

    Kolář, Filip; Dušková, Eva; Sklenář, Petr

    2016-09-01

    The tropical Andes represent one of the world's biodiversity hot spots, but the evolutionary drivers generating their striking species diversity still remain poorly understood. In the treeless high-elevation Andean environments, Pleistocene glacial oscillations and niche differentiation are frequently hypothesized diversification mechanisms; however, sufficiently densely sampled population genetic data supporting this are still lacking. Here, we reconstruct the evolutionary history of Loricaria (Asteraceae), a plant genus endemic to the Andean treeless alpine zone, based on comprehensive population-level sampling of 289 individuals from 67 populations across the entire distribution ranges of its northern Andean species. Partly incongruent AFLP and plastid DNA markers reveal that the distinct genetic structure was shaped by a complex interplay of biogeography (spread along and across the cordilleras), history (Pleistocene glacial oscillations) and local ecological conditions. While plastid variation documents an early split or colonization of the northern Andes by at least two lineages, one of which further diversified, a major split in the AFLP data correlate with altitudinal ecological differentiation. This suggests that niche shifts may be important drivers of Andean diversification not only in forest-alpine transitions, but also within the treeless alpine zone itself. The patterns of genetic differentiation at the intraspecific level reject the hypothesized separation in spatially isolated cordilleras and instead suggest extensive gene flow among populations from distinct mountain chains. Our study highlights that leveraging highly variable markers against extensive population-level sampling is a promising approach to address mechanisms of rapid species diversifications.

  16. Descripción de las larvas de dos centrolénidos (Anura: Centrolenidae del noroccidente de la Cordillera Oriental, Colombia

    Directory of Open Access Journals (Sweden)

    Marco Rada

    2007-01-01

    Full Text Available Se describen las larvas de dos especies de la familia Centrolenidae (Hyalinobatrachium ibama y Cochranella daidalea procedentes del flanco occidental de la cordillera Oriental en el departamento de Norte de Santander, Colombia. En la descripción de las larvas, además de las características morfológicas tradicionales, se incorporaron nuevos elementos de juicio como la longitud del tubo cloacal, la forma del rostro, el patrón de color y la posición del espiráculo, los cuales resultaron ser informativos y muy útiles en la diferenciación de las especies. Se proporciona una discusión acerca de la validez taxonómica de algunos de los caracteres morfológicos empleados usualmente en las descripciones y comparaciones de los renacuajos de la familia Centrolenidae.We describe herein the larvae of two species of the family Centrolenidae (Hyalinobatrachium ibama and Cochranella daidalea from the Department of Norte de Santander on the western flank of the Cordillera Oriental, Colombia. In order to provide an adequate description, we incorporate new elements such as: vent-tube length, snout shape, color pattern and spiracle position. A discussion about the taxonomic validity of some tadpole morphological characteristics traditionally used in descriptions and comparisons of the family Centrolenidae is provided.

  17. Southern Gothic Literature

    DEFF Research Database (Denmark)

    Bjerre, Thomas Ærvold

    2017-01-01

    Provides an outline of Southern Gothic Literature, offers an argument about its history and shape, and discusses the scholarly literature surrounding Southern Gothic. Oxford Research Encyclopedia is an online peer-reviewed encyclopedia for researchers, teachers, and students interested in all...... facets of the study of literature...

  18. Unraveling an antique subduction process from metamorphic basement around Medellín city, Central Cordillera of Colombian Andes

    Science.gov (United States)

    Bustamante, Andres; Juliani, Caetano

    2011-10-01

    varies between 400 and 555 °C at pressures of 5-6 kbar in the retrograde metamorphic path. The El Retiro rocks evidence strong decompression with narrow variation in temperature, showing pressure values between 8.7 and 2.7 kbar at temperatures of 740-633 °C. These metamorphic fragments of the basement in the Central Cordillera of the Colombian Andes could represent a close relationship with an antique subduction zone.

  19. Modelling cascading and erosional processes for glacial lake outburst floods in the Quillcay catchment, Huaraz, Cordillera Blanca, Peru

    Science.gov (United States)

    Baer, Patrick; Huggel, Christian; Frey, Holger; Chisolm, Rachel; McKinney, Daene; McArdell, Brian; Portocarrero, Cesar; Cochachin, Alejo

    2016-04-01

    Huaraz as the largest city in Cordillera Blanca has faced a major disaster in 1941, when an outburst flood from Lake Palcacocha killed several thousand people and caused widespread destruction. Recent studies on glacial lake outburst flood (GLOF) modelling and early warning systems focussed on Lake Palcacocha which has regrown after the 1941 event, from a volume of half a million m3 in 1974 to a total volume of more than 17 million m3 today. However, little research has been conducted so far concerning the situation of other lakes in the Quillcay catchment, namely Lake Tullparaju (12 mill. m3) and Cuchillacocha (2.5 mill. m3), which both also pose a threat to the city of Huaraz. In this study, we modelled the cascading processes at Lake Tullparaju and Lake Cuchillacocha including rock/ice avalanches, flood wave propagation in the lake and the resulting outburst flood and debris flows. We used the 2D model RAMMS to simulate ice avalanches. Model output was used as input for analytical 2D and 3D calculations of impact waves in the lakes that allowed us to estimate dam overtopping wave height. Since the dimension of the hanging glaciers above all three lakes is comparable, the scenarios in this study have been defined similar to the previous study at Lake Palcacocha. The flow propagation model included sediment entrainment in the steeper parts of the catchment, adding up to 50% to the initial flow volume. The results for total travel time as well as for inundated areas and flow depth and velocity in the city of Huaraz are comparable to the previous studies at Lake Palcacocha. This underlines the importance of considering also these lakes within an integral hazard analysis for the city of Huaraz. A main challenge for modelling GLOFs in the Quillcay catchment using RAMMS is the long runout distance of over 22 km combined with the very low slope gradient of the river. Further studies could improve the process understanding and could focus on more detailed investigations

  20. Origin of gem corundum in calcite marble: The Revelstoke occurrence in the Canadian Cordillera of British Columbia

    Science.gov (United States)

    Dzikowski, Tashia J.; Cempírek, Jan; Groat, Lee A.; Dipple, Gregory M.; Giuliani, Gaston

    2014-06-01

    The calcite marble-hosted gem corundum (ruby, sapphire) occurrence near Revelstoke, British Columbia, Canada, occurs in the Monashee Complex of the Omineca Belt of the Canadian Cordillera. Corundum occurs in thin, folded and stretched layers with green muscovite + Ba-bearing K-feldspar + anorthite (An0.85-1) ± phlogopite ± Na-poor scapolite. Other silicate layers within the marble are composed of: (1) diopside + tremolite ± quartz and (2) garnet (Alm0.7-0.5Grs0.2-0.4) + Na-rich scapolite + diopside + tremolite + Na,K-amphiboles. Non-silicate layers in the marble are either magnetite- or graphite-bearing. Predominantly pink (locally red or purple) opaque to transparent corundum crystals have elevated Cr2O3 (≤ 0.21 wt.%) and variable amounts of TiO2; rare blue rims on the corundum crystals contain higher amounts of TiO2 (≤ 0.53 wt.%) and Fe2O3 (≤ 0.07 wt.%). The associated micas have elevated Cr, V, Ti, and Ba contents. Petrography of the silicate layers show that corundum formed from muscovite at the peak of metamorphism (~ 650-700 °C at 8.5-9 kbar). Because the marble is almost pure calcite (dolomite is very rare), the corundum was preserved because it did not react with dolomite to spinel + calcite during decompression. The scapolite-bearing assemblages formed during or after decompression of the rock at ~ 650 °C and 4-6 kbar. Gem-quality corundum crystals formed especially on borders of the mica-feldspar layers in an assemblage with calcite. Whole rock geochemistry data show that the corundum-bearing silicate (mica-feldspar) layers formed by mechanical mixing of carbonate with the host gneiss protolith; the bulk composition of the silicate layers was modified by Si and Fe depletion during prograde metamorphism. High element mobility is supported by the homogenization of δ18O and δ13C values in carbonates and silicates for the marble and silicate layers. The silicate layers and the gneiss contain elevated contents of Cr and V due to the volcanoclastic

  1. EXPERIENCIAS DE CORDILLERA, ECOS DE FRÍO: RELATOS CRUZADOS ENTRE CHILE Y QUITO EN EL SIGLO XVI

    Directory of Open Access Journals (Sweden)

    Alejandra Vega

    2011-11-01

    Full Text Available La narración de la secuencia de la conquista del Perú nos enfrenta con la fijación de dos episodios diferentes aunque articulados: la jornada a Quito de Pedro de Alvarado en 1534 y la expedición a Chile de Diego de Almagro, entre 1535 y 1536, que incluyen, ambas, una travesía cordillerana. El presente artículo discute los ecos que pueden rastrearse de los relatos acerca de estas expediciones en un conjunto de obras redactadas en torno a 1550 (Gonzalo Fernández de Oviedo, Francisco López de Gómara, Pedro Cieza de León y Agustín de Zárate. A partir de convergencias y diferencias inesperadas en estos textos, se discute la importancia de la circulación oral de historias entre los conquistadores del Perú. Se plantea que la práctica social de la conversación oral permitió fijar, además de estas historias, una temprana conceptualización cristiana de los límites del Tawantinsuyu. En ella se concibió a Quito y Chile como las marcas fronterizas del espacio recién conquistado, permitiendo que ambos territorios se superpusieran al caracterizarse a partir a un mismo conjunto de imágenes sobre la experiencia de la cordillera.In the Hispanic narrative of the conquest of Peru, we can identify two different yet related episodes: Pedro de Alvarado's journey to Quito in 1534 and the expedition to Chile commanded by Diego de Almagro in 1535-1536. This article discusses the echoes than can be pinpointed in the accounts of both experiences in a corpus of texts written or printed around 1550 (Gonzalo Fernández de Oviedo, Francisco López de Gómara, Pedro Cieza de León and Agustín de Zárate. By tracing unexpected similarities and differences, this proposal discusses the importance of oral circulation of histories amongst Peruvian conquistadors. The features of conversation, as a social practice, allowed the register ofan early Christian conceptualization of the Tawantinsuyu territory. Here Quito and Chile became frontier marks of the

  2. Recurrencia en el desarrollo de cuencas de intraarco.: Cordillera Neuquina (37°30´- 38°S

    Directory of Open Access Journals (Sweden)

    A. Folguera

    2003-03-01

    Full Text Available Los Andes entre 36° y 39°S están caracterizados por la superposición de tres cuencas de intraarco a lo largo de los últimos 25 millones de años, de las cuales las primeras dos han sido separadas entre sí por fenómenos de inversión tectónica. El rasgo orogénico resultante de esta fase de deformación colapsó parcialmente durante los últimos dos ciclos de extensión. El primer evento extensional corresponde a la cuenca de Cura Mallín que se desarrolló entre 25 y 12 millones de años atrás (Oligoceno superior al Mioceno inferior-medio, fue invertida entre 12 y 8 Ma (Mioceno superior, con una cordillera resultante de poco más de 2000 metros de altura. El segundo ciclo se corresponde con la cuenca de Cola de Zorro, la cual comenzó a subsidir hace 5 millones de años (Plioceno inferior. La unidad correspondiente a la Formación Cola de Zorro se ha depositado desde su comienzo sobre la estructura compresiva del orógeno formado a partir de la inversión de la cuenca de Cura Mallín, como consecuencia de un colapso extensional del mismo o quizás de un relajamiento extensional de la estructura compresiva, que deprimió este rasgo por debajo de la cota de 1200 metros sobre el nivel del mar. A lo largo del límite internacional, existen aún remanentes de la estructura orogénica del Mioceno superior que fueron conservados como altos estructurales de la cuenca pliocena inferior. Estos altos facilitan el estudio de la estructura original. La recurrencia en la formación de cuencas de intraarco durante los últimos 25 millones de años estaría ligada a la migración promedio hacia la trinchera del frente volcánico durante el Terciario, como consecuencia del empinamiento de la placa de Nazca y a inestabilidades de la estructura orogénica derivadas de reorganizaciones mayores en el sistema subductivo entre las placas vecinas.

  3. Spatio-temporal assessment of WRF, TRMM and in situ precipitation data in a tropical mountain environment (Cordillera Blanca, Peru

    Directory of Open Access Journals (Sweden)

    L. Mourre

    2015-07-01

    Full Text Available The estimation of precipitation over the broad range of scales of interest for climatologists, meteorologists and hydrologists is challenging in high altitudes of tropical regions, where the spatial variability of precipitation is important while in situ measurements remain scarce largely due to operational constraints. Three different types of rainfall products – ground based, satellite derived, RCM outputs – are compared here during the hydrological year 2012/13 in order to retrieve rainfall patterns at time scales ranging from sub-daily to annual over a watershed of approximately 10 000 km2 in Peru. It is a high altitude catchment, located in the region of the Cordillera Blanca, with 41 % of its area above 4000 m a.s.l. and 340 km2 glaciated. Daily in situ data are interpolated using a kriging with external drift (KED algorithm; the satellite product is TRMM 3B42, which incorporates monthly gauge data; RCM outputs are obtained from WRF run with a Thompson microphysical scheme at three nested resolutions: 27, 9 and 3 km. The performances of each product are assessed from a double perspective. A local comparison with gauge data is first carried out when relevant (diurnal and seasonal cycles, statistics of rainfall occurrence; then the ability of each product to reproduce some well-known spatial features of rain fields at various time scales (from annual down to daily is analysed. WRF simulations largely overestimate the annual totals, especially at low spatial resolution, while reproducing correctly the diurnal cycle and locating the spots of heavy rainfall more realistically than either the ground-based KED or the TRMM products. The main weakness of the KED data is the production of annual rainfall maxima over the summit rather than on the slopes, induced by a lack of in situ data above 3800 m a.s.l. One main limitation of the TRMM product is its poor performance over ice-covered areas because ice on the ground behaves in a similar way as

  4. Application of terrestrial scanning LIDAR to study the evolution of Quisoquipina Glacier in the Cordillera Vilcanota, Cusco - Peru

    Science.gov (United States)

    Montoya, Nilton; Macedo, Nicolas; Sanchez, Olivier; Huggel, Christian; Giraldez, Claudia; Schauwecker, Simone; Drenkhan, Fabian; Frey, Holger; Molina, Edwin; Sikos, Felipe

    2017-04-01

    Tropical glaciers are highly sensitive to alterations in climate and therefore good indicators for global climate change. Glaciers located in Peru represent 71% of all tropical glaciers in the world, and have shown a significant area reduction of about 43% within the last 40 years mainly due to the increase in surface temperature. Tropical glaciers play a particular role as freshwater reservoirs and buffers to river discharge variability and water scarcity within a pronounced wet and dry season. Their monitoring is extraordinarily important but few studies exist on mass balance. The Cordillera Vilcanota, at the origin of the Rio Vilcanota-Urubamba, contains about 25% of all glaciers in Peru. In recent decades, glacier shrinkage has accelerated in this mountain range. Between 1988 and 2010, glacier area was reduced at an annual rate of about 4 km2 (1.1 %) from some 360 km2 to about 270 km2 (25%). A total volume loss of 40-45% (from 17-20 km3 to 9.2-12.4 km3) can be estimated for the period 1962-2006, with an accelerated rate since the 1980s. Terrestrial scanning LIDAR (LIght Detection And Ranging) surveys represent nowadays the most powerful tool to accurately map its inaccessible glacier surfaces. A laser scanner enables researchers to capture laser range data at a rate of thousands of x, y, z and laser-intensity points per second; such data can be used to construct a very accurate 3D model of the surveyed surface. We used a terrestrial LiDAR sensor (Optech ILRIS 3D-LR) for intensively monitoring the changes occurred at volume and front glacier: the Quisoquipina glacier. In August and October 2015, August and December 2016, four terrestrial scanning LIDAR surveys have been carried out in order to monitor the evolution of the glacier. The comparison between repeated surveys showed significant retreats in the front, area and volume of the glacier (e.g. lost volume 375000 m3 between august 2015 and December 2016, in 80812 m2 of area of study).

  5. COMPOSICIÓN Y ABUNDANCIA DE ANUROS EN DOS TIPOS DE BOSQUE (NATURAL Y CULTIVADO EN LA CORDILLERA ORIENTAL COLOMBIANA

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    GUTIÉRREZ-LAMUS DORIS L.

    2004-06-01

    Full Text Available Se determinaron la composición y la abundancia de las especies de anuros de unárea de bosque nativo y de un área de bosque de roble cultivado adyacentes haciendocomparaciones entres estos dos hábitats. Ambos bosques se encuentran dentro delSantuario de Fauna y Flora Guanentá, Alto Río Fonce en los límites entre losdepartamentos de Santander y Boyacá. El encuentro visual azaroso y la búsqueda alo largo de transectos fueron las técnicas empleadas para la búsqueda de individuosdurante diferentes horas del día y en diferentes meses durante un año. Se registraron14 especies (cinco géneros y cuatro familias, el género con mayor diversidad fueEleutherodactylus, dentro del cual se registran dos especies indescritas. El resto delas especies de anuros son endémicas de la zona centro-norte de la cordillera Oriental,a excepción de Gastrotheca nicefori que tiene una distribución más amplia. Seencontraron diferencias en la riqueza y la abundancia entre los bosques. El bosquenativo tiene una mayor diversidad y en él se registró el mayor número total deindividuos. Las búsquedas por encuentro casual permitieron una mejor detecciónde la riqueza al no dejar por fuera las especies raras. En el robledal la mayoría de lasespecies se encontraron por este método sobre el camino y no al interior del bosque,indicando un evidente efecto de borde. Eleutherodactylus merostictus, E. miyataiy Eleutherodactylus uisae son las especies más abundantes en los dos bosquesusando los dos tipos de muestreo y están presentes durante los meses de menorprecipitación, considerándose como especies generalistas en ocupación demicrohábitats. Así, las especies comunes y abundantes en el área ocupan fácilmenteel bosque cultivado, pero las especies raras o poco abundantes sólo se encuentranen el borde de los bosques o en el interior del bosque nativo.

  6. Southern Identity in "Southern Living" Magazine

    Science.gov (United States)

    Lauder, Tracy

    2012-01-01

    A fantasy-theme analysis of the editors' letters in "Southern Living" magazine shows an editorial vision of valuing the past and showcasing unique regional qualities. In addition, a content analysis of the visual representation of race in the magazine's formative years and recent past validates that inhabitants of the region were portrayed…

  7. Biomarker characterization of the record of the OAE1a (early Aptian) in Betic and Cantabrian basins (Spain)-Sedimentary implications

    Science.gov (United States)

    Quijano, María. Luisa; Castro, José Manuel; Pancost, Richard D.; de Gea, Ginés. A.; Najarro, María.; Aguado, Roque; Rosales, Idoia; Martín-Chivelet, Javier

    2010-05-01

    Molecular analyses of sedimentary organic matter are powerful tools in assessing the origin of organic matter and its thermal maturity as well as constraining ancient environmental conditions, such as as marine productivity, anoxia in bottom waters or the photic zone and sea surface temperatures. This communication presents the study of four sections recording the OAE1a (early Aptian) in Spain, which are located in two broad basins respectively located in the South and the North of Iberia: the Southern Iberian Palaeomargin (Carbonero - CAB, La Frontera - XF and Cau - CAU sections) and the Cantabrian Basin (Puente Nansa - PN section). These sections represent depositional settings ranging from platform (CAU, PN) to pelagic environments (CAB, XF). C-isotope profiles and biostratigraphic data are used to define the interval corresponding to the OAE 1a. Here we focus on the biomarker composition of the organic-rich facies, and the integration of these data with the sedimentology, stratigraphy and paleogeography. The study has been based mainly upon the analysis of samples with Gas Chromatography-Mass Spectrometry (GCMS). Four main groups of compounds are present in all sections: n-alkanes, isoprenoids, hopanes and steranes. n-Alkanes and isoprenoids (pristane and phytane) are dominant in most samples. To facilitate interpretation of these distributions, we have calculated the TAR (terrestrial aquatic ratio derived from the ratio of long to short chain compounds) and also the OEP (odd over even predominance of n-alkanes). The ratio of pristane to phytane and various isoprenoid/n-alkanes ratios have also been calculated. The hopanes are represented by a range of C27 to C35 components, with the specific isomers varying amongst the sections due to differences in thermal maturity. Steranes occur as a range of C27, C28 and C29 isomers, whereas diasteranes only occur in the most thermally mature section (CAB). Other compounds of interest include gammacerane and dinosterane

  8. Can cosmic ray exposure dating reveal the normal faulting activity of the Cordillera Blanca Fault, Peru? ¿Dataciones por exposición de rayos cósmicos revelan fallamiento activo normal en la falla de la Cordillera Blanca, Perú?

    Directory of Open Access Journals (Sweden)

    L.L. Siame

    2006-12-01

    Full Text Available The build-up of in situ-produced cosmogenic 10Be within bedrock scarps and escarpments associated to the Cordillera Blanca Normal Fault, Peru, was measured to evaluate, through Cosmic Ray Exposure dating, its normal faulting activity. The highest mountain peaks in Peru belong to the 210 km-long, NW- striking, Cordillera Blanca. Along its western border, the Cordillera Blanca Normal Fault is responsible for a vertical relief over 4.4 km, whose prominent 2 km high escarpment is characterized by ~1 km-high triangular facets corresponding to vertical displacements cumulated during the last 1-2 million years. At a more detailed scale, this fault system exhibits continuous geomorphic evidence of repeated displacements, underlined by 2 to 70 m-high scarps, corresponding to vertical displacements cumulated since Late Pleistocene and Holocene periods. Although microseismicity occurs along the Cordillera Blanca Normal Fault, no major historical or instrumental earthquake has been recorded since the beginning of the Spanish settlement in the 16th century. To evaluate the vertical slip rate along the major 90 km-long central segment of the Cordillera Blanca Normal Fault, the Quaternary fault escarpment (i.e., triangular facet, as well as the bedrock fault scarp, have been sampled for 10Be Cosmic Ray Exposure dating. Even if the uppermost part of the triangular facets have been resurfaced by the Last Glacial Maximum glaciers, our results allow to estimate a vertical slip-rate of 3±1 mm/yr, and suggest at least 2 seismic events during the last 3000 years.La acumulación in situ de 10Be cosmogénico en las rocas intrusivas de las escarpas de la falla normal de la Cordillera Blanca del Perú han sido medidas para evaluar, su actividad de fallamiento normal., con edades de exposición a los rayos cósmicos. Los más altos picos en el Perú conforman la Cordillera Blanca que se extiende con una longitud de 210 km según una orientación NO. A lo largo de su l

  9. 甲钴胺联合前列地尔治疗糖尿病周围神经病变的临床观察%Clinical Observation of Mecobalamin Alprostadil in the Treatment of Dia-betic Peripheral Neuropathy

    Institute of Scientific and Technical Information of China (English)

    车微娟

    2016-01-01

    Objective To observe and analysis of Mecobalamin Combined with prostaglandin PGE1 in the treatment of dia-betic peripheral neuropathy clinical efficacy and safety. Methods A total of 64 patients with diabetic peripheral neuropathy from May 2015 to March 2014, were randomly divided into observation group (33 cases) and control group (31 cases).Two groups of patients were given basic treatment and intravenous injection of alprostadil. On the basis of the observation group plus mecobalamin. Results Before treatment, the difference of temperature, pressure, vibration and the score of Toronto was not significant(P>0.05). After 2 weeks treatment, compared with the control group, the observation group was less than that of the observation group (P< 0.05). Conclusion Mecobalamin alprostadil can significantly improve patients feel, limb motor nerve reaction, improve the clinical efficacy.%目的:观察和分析甲钴胺联合前列地尔治疗糖尿病周围神经病变的临床效果和安全性。方法选择2014年3月-2015年5月该院收治的64例糖尿病周围神经病变患者,随机分为观察组31例和对照组33例。两组患者均给予基础治疗和前列地尔静脉注射。观察组在此基础上加用甲钴胺治疗。治疗2周后记录两组患者治疗前后的温度觉、压力觉、振动觉及多伦多评分变化。结果治疗2周后,与对照组相比,观察组温度觉、压力觉、振动觉异常案例少,多伦多评分低,差异有统计学意义(P<0.05﹚。结论甲钴胺联合前列地尔可显著改善患者四肢感觉、运动神经反应,提高临床疗效。

  10. Cretaceous Exhumation of the North American Cordillera Measured through Mineral Multi-Dating: Insights into Basin Filling Models and Orogenic Architecture

    Science.gov (United States)

    Painter, C. S.; Carrapa, B.; DeCelles, P. G.; Gehrels, G. E.; Thomson, S. N.

    2015-12-01

    Apatite fission track (AFT) thermochronology is an effective thermochronometer to measure source exhumation in the North American Cordillera, western U.S.A. We use a combination of thermochronology and geochronology to measure lag times, i.e., the difference in time between the cooling and depositional ages of a mineral crystal. These lag-time measurements using source exhumation ages, measured with AFT thermochronology, and depositional ages, measured with biostratigraphy and detrital zircon U-Pb geochronology, indicate constant to decreasing lag times of 0-5 m.y. throughout the Cretaceous. These lag times are consistent with rapid exhumation rates of ~0.9->1 km/m.y. One pitfall of using detrital thermochronology to measure source exhumation is assuring that the apatite crystals are exhumed apatites and not volcanic apatites introduced into the system from the volcanic arc. To do this we use U-Pb geochronology to remove samples contaminated with young arc derived apatites and keep those with old exhumed apatites. Five of the seven detrital AFT samples were significantly contaminated with young volcanic apatites, showing that U-Pb geochronology should be a routine step in measuring lag times. Our findings demonstrate that coarse-grained foreland basin deposits in the Cretaceous Western Interior, in both the proximal and distal settings, were deposited during times of active tectonism and exhumation and that sediments are not stored in wedge-top and proximal foredeep settings for long periods of time, i.e. >5 m.y., and then subsequently reworked distally. Exhumation rates of ~0.9->1 km/m.y. are not sustainable over the entire orogenic belt for the duration of the Sevier orogeny, indicated by the lack of deep-crustal material exhumed in the North American Cordillera. High exhumation rates were likely concentrated over the eastward-propagating Sevier fold-thrust belt, whereas the Nevadaplano and hinterland experienced much slower rates of exhumation. This variation in

  11. European Southern Observatory

    CERN Multimedia

    1970-01-01

    Professor A. Blaauw, Director general of the European Southern Observatory, with George Hampton on his right, signs the Agreement covering collaboration with CERN in the construction of the large telescope to be installed at the ESO Observatory in Chile.

  12. Southern African Business Review

    African Journals Online (AJOL)

    The Southern African Business Review is a refereed and accredited scientific journal of the College of Economic and Management Sciences of the University of ... The application of analytical procedures in the audit process: A South African ...

  13. University of Southern California

    Data.gov (United States)

    Federal Laboratory Consortium — The focus of the University of Southern California (USC) Children''s Environmental Health Center is to develop a better understanding of how host susceptibility and...

  14. Southern deepwater swamps

    Science.gov (United States)

    William H. Conner; Marilyn A. Buford

    1998-01-01

    The authors define, classify, and analyze the economic significance of southern deepwater swamps. They discuss the physical environment, vegetational communities, animal communities, management issues, and research needs for this complex resource.

  15. Earthquakes in Southern California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — There have been many earthquake occurrences in Southern California. This set of slides shows earthquake damage from the following events: Imperial Valley, 1979,...

  16. Southern hemisphere observations

    Science.gov (United States)

    Orchiston, Wayne

    Because of insurmountable problems associated with absolute dating, the non-literate cultures of the Southern Hemisphere can contribute little to Applied Historical Astronomy, although Maori traditions document a possible supernova dating to the period 1000-1770 AD. In contrast, the abundant nineteenth century solar, planetary, cometary and stellar observational data provided by Southern Hemisphere professional and amateur observatories can serve as an invaluable mine of information for present-day astronomers seeking to incorporate historical data in their investigations.

  17. Estratigrafía y facies volcánicas y volcaniclásticas de la Formación Valle del Cura: magmatismo paleógeno en la Cordillera Frontal de San Juan Stratigraphy and volcanic facies of the of the Valle del Cura Formation: Paleogene volcanism in the Frontal Cordillera of San Juan

    OpenAIRE

    V. D. Litvak; S. Poma

    2005-01-01

    En la región del Valle del Cura, Cordillera Frontal de San Juan, aflora una espesa secuencia de rocas volcánicas y volcaniclásticas, en facies piroclásticas y epiclásticas, que representa el desarrollo de un importante episodio volcano-sedimentario eoceno-oligoceno inferior. Esta unidad, la Formación Valle del Cura, incluye espesos paquetes de tobas, conglomerados gruesos, areniscas líticas medianas a gruesas, areniscas volcánicas y escasas pelitas. Los niveles volcánicos están formados por f...

  18. New Constraints on the Timing and Magnitude of Deformation and Basin Exhumation in the Eastern Cordillera of NW Argentina.

    Science.gov (United States)

    Trimble, J. D.; Carrapa, B.; Stockli, D. F.; Stutz, J.

    2008-12-01

    The Angastaco Basin is a ~20km wide and ~6km thick intramontane basin within the Eastern Cordillera (EC) of NW Argentina. The basin is bounded to the east and west by reverse faults that put basement rocks of the Paleozoic Puncoviscana and Cretaceous Santa Barbara Group on top of the Cenozoic sequence. Numerous faults and folds disrupt the basin internally. Some, if not most, of these structures seem to be the result of reactivation of previous normal faults related to the Salta Rift (Carrera et al. , 2006). Recent structural and thermochronological data from the EC of Argentina suggest tectonic deformation in the Eocene-Miocene (e.g., Coutand et al., 2006; Hogn et al., 2007). Data from the EC in Bolivia suggest that deformation ceased by ca. 10.7 Ma (McQuarrie et al., 2005). Therefore, different challenging questions remain open such as: (1) Are all the structures observed in the basin and along its margin a result of reactivation? (2) When was the timing and what was the magnitude of deformation within the basin and surrounding region? New detailed mapping and cross-sections in the Angastaco Basin reveal a number of faults and folds never before documented, including several km-scale west vergent folds interspersed with a complex arrangement of smaller, more angular, east-vergent faults and folds. Clear influence from both east and west-vergent deformation within the basin suggests interplay between the eastward propagation of EC related structures and westward reactivation of Santa Barbara System structures. A lack of structural continuity across the roughly E-W trending portions of Rio Calchaqui suggests that the river follows one or more unexposed strike- slip faults as it cuts across the Tertiary section from W to E. Minor offsets and lack of lateral continuity suggest that these faults are likely tear-faults coeval with deformation in the basin, although they may have been active during multiple pulses of tectonism. With an east-west trend, these structures

  19. Reducing risks from hazardous glacier lakes in the Cordillera Blanca (Peru): Six decades of experience and perspectives for the future

    Science.gov (United States)

    Portocarrero, Cesar; Cochachin, Alejo; Frey, Holger; González, Cesar; Haeberli, Wilfried; Huggel, Christian

    2016-04-01

    Outbursts from glacier lakes at various spatial and temporal scales have had marked geomorphological effects in many mountain ranges. In many glacierized Andean mountain regions substrates of human settlements made out of flood and debris-flow deposits are testimonies of such events. Examples in the Cordillera Blanca, Peru, are the towns of Caraz, Carhuaz or parts of Huaraz. Continued glacier shrinking since the end of the Little Ice Age caused the formation or enlargement of numerous lakes. The outburst of Laguna Palcacocha, destroying the centre of Huaraz and causing more than 1800 losses of life in December 1941, marked the beginning of systematic risk reduction work in Peru. Corresponding efforts included glacier and lake inventories, hazard assessments, definition of high-risk situations, and completion of engineering work for lake-level lowering in more than 30 cases. The latter comprises outlet reinforcements on morainic dams as well as artificial tunnels in bedrock thresholds. This work has been remarkably efficient as documented in the latest case of the Laguna Huallcacocha (Carhuaz-Ancash), where the earlier made installations withstood the erosive power of an impact wave from an ice avalanche in 2015. In the case of the Laguna 513, the impact wave and far-reaching flood caused by a rock/ice avalanche from Nevado Hualcán in April 2010 showed that the risk had been essentially reduced by the preventive lake-level lowering in the early 1990s but not to zero. Risk assessments, planning, construction and non-structural risk reduction efforts continue. Work is in progress to increase the safety of Laguna Palcacocha where extensive assessments and model calculations had been carried out. Risks related to rock/ice avalanches into lakes from steep icy slopes and related to de-buttressing processes as well as long-term permafrost degradation increases. Based on morphological indications and numerical modelling (GlabTop) an inventory of possible future lakes

  20. Efecto del secado de las muestras sobre la extracción selectiva de Fe y A1 activos en Andisoles del norte de la cordillera central Colombiana.

    Directory of Open Access Journals (Sweden)

    Jaramillo J. Daniel F.

    2000-12-01

    Full Text Available Muestras secadas al aire y sin secar de cinco perfiles de Andisoles del norte de la cordillera central colombiana fueron sometidas a extracción con oxalato ácido de amonio y con pirofosfato de sodio. En los extractos de oxalato se determinaron A1, Fe y Si y en los de pirofosfato A1 y Fe. El secado de las muestras redujo significativamente al 95% la cantidad de A1 y de Fe extraída con oxalato ácido, dificultando la clasificación de los suelos en el orden Andisol utilizando los parámetros de la taxonomía del USDA.

  1. Características físicas de la población prehispánica de la cordillera oriental: implicaciones etnogenéticas

    Directory of Open Access Journals (Sweden)

    José Vicente Rodríguez Cuenca

    2010-03-01

    Full Text Available Se recurre al análisis estadístico para examinar el grado de similitud o afinidad entre las series de cráneos de la cordillera oriental y otras muestras comparativas de Colombia y América. Se sugiere microevolución en esta región a partir de sus primeros pobladores, con tendencia a la braquicefalización; se plantea deriva genética como mecanismo evolutivo explicativo de la especificidad morfológica de la población de la Mesa de los Santos. No se corroboran las tesis de migraciones tardías hacia el territorio que ocuparon los Muiscas.

  2. Una nueva especie de rana terrestre del género Pristimantis (Amphibia: Craugastoridae, de la Cordillera de Kutukú, Ecuador

    Directory of Open Access Journals (Sweden)

    Jorge Brito M.

    2013-01-01

    Full Text Available Describimos una especie nueva de mediano tamaño (LRC en la hembra 38.7 mm; en machos de 23.8 a 26.4 mm de rana terrestre del género Pristimantis de los bosques sub-tropicales de la Cordillera de Kutukú, del sureste de Ecuador, a elevaciones de 1581-1820 m. Asignamos a Pristimantis almendariz sp. nov., al subgénero Hypodictyon, serie de especies ridens. La nueva especie difiere de otros miembros de la serie ridens por su patrón distintivo con manchas dorsales, membrana timpánica ausente, presencia de tubérculos cónicos agrandados en el párpado, tubérculo inter-orbital prominente, e iris plateado con reticulaciones negras.

  3. Tectonic and climatic controls on the Chuquibamba landslide (western Andes, southern Peru)

    Science.gov (United States)

    Margirier, A.; Audin, L.; Carcaillet, J.; Schwartz, S.; Benavente, C.

    2015-06-01

    The contribution of landslides to the Quaternary evolution of relief is poorly documented in arid contexts. In southern Peru and northern Chile, several massive landslides disrupt the arid western Andean front. The Chuquibamba landslide, located in southern Peru, belongs to this set of large landslides. In this area, the Incapuquio fault system captures the intermittent drainage network and localizes rotational landslides. Seismic activity is significant in this region with recurrent Mw 9 subduction earthquakes; however, none of the latest seismic events have triggered a major landslide. New terrestrial cosmogenic dating of the Chuquibamba landslide provides evidence that the last major gravitational mobilization of these rotational landslide deposits occurred at ~ 102 ka, during the Ouki wet climatic event identified on the Altiplano between 120 and 98 ka. Our results suggest that wet events in the arid and fractured context of the Andean forearc induced these giant debris flows. Finally, our study highlights the role of tectonics and climate on (i) the localization of large Andean landslides in the Western Cordillera and on (ii) the long-term mass transfer to the trench along the arid Andean front.

  4. Evolución tectono-magmática durante el Pérmico al Jurásico temprano en la Cordillera del Viento (37°05´S - 37°15´S: nuevas evidencias geológicas y geoquímicas del inicio de la cuenca Neuquina Tectono-magmatic evolution during the Permian to the Early Jurassic in the Cordillera del Viento (37°05´S - 37°15´S: new geological and geochemical evidences for the early stages of the Neuquén basin

    Directory of Open Access Journals (Sweden)

    E.J. Llambías

    2007-06-01

    podría explicar la forma no lineal de la cuenca Neuquina en la provincia del Neuquén.The southern extremity of the Cordillera del Viento is mainly composed of volcanic sequences, which form the basement of the Neuquén basin. The oldest rocks are the sediments in the Huaraco Formation, Andacollo Group, of Upper Carboniferous age. After being folded by the San Rafael orogenic phase during the Lower Permian, these sediments were intruded by granodioritic and monzogranitic plutons along with dikes and domes of rhyolitic nature. They were then covered in angular unconformity by rhyolitic ignimbrites, which are co-genetic with the intrusives. The resulting volcanic-plutonic complex is suggested to be correlative with the Permian Choiyoi Group exposed in the Cordillera Frontal and the Bloque de San Rafael geological provinces. This volcanic-plutonic complex was subjected to strong erosion during the Early to Middle Triassic. The development of an undulated erosion surface (Huarpican unconformity resulted in the exposure of the cupolas of the plutons. This surface support the Cordillera del Viento Formation (ex Groeber's Choiyoilitense, which consists of a volcanic sequence of andesitic to rhyolitic composition up to 1.300 meters thick. The next unit, the Milla Michicó Formation, was also deposited unconformably. This unit is composed of bedded flows of basalts, andesitic basalts and rhyolites with thickness up to 200 meters. The succession continued with the unconformable deposition of the La Primavera Formation, which is the oldest unit of the Cuyo Group. It is composed of marine sediments interbedded with basaltic flows at the base and rhyolitic ignimbrites in the upper levels. The thickness varies from a few meters up to 400 meters. The La Primavera Formation is covered in apparent conformity by the Los Molles Formation, which has limestones at the base and contains pelites with andesitic lahar intercalations deposited in a turbiditic regime. Regionally, the Huarpican

  5. The effects of lateral density gradients, slopes and buoyancy on channel flow: 1D analytical solutions and applications to the SE Canadian Cordillera

    Science.gov (United States)

    Gervais, Félix; Ranalli, Giorgio

    2017-08-01

    We present 1D analytical solutions for channel flow in orogens driven by various types of pressure gradients. Our calculations demonstrate that lateral density gradients in the upper crust, such as would occur across a suture zone separating arc rocks from pericratonic sediments provide a driving force for Poiseuille flow as large as topographic gradients observed in modern mountain belts. For cases for which the gradients are external (topographic and lateral density gradients) and internal (e.g. partial melting of channel material) to the channel, inclination decreases and increases the Poiseuille component of the average flow-velocity within the channel by the cosine and sine of the slope, respectively. The magnitude of the pressure gradient consequent upon the buoyancy generated by partial melting of metapelites in a channel with a 30° slope, such as would occur above an underthrusting basement ramp, is similar to that of topographic or lateral density gradients. Channel flow up a ramp could thus constitute an important exhumation mechanism in large hot orogens. Our calculations indicate that mid-crustal channel flow was a highly likely process in the Late Cretaceous-Paleocene setting of the southeastern Canadian Cordillera. The flow was first driven by the lateral density contrast between pericratonic sediments and the arc-related Intermontane terrane, then by combined effect of topographic gradient and melt-induced buoyancy of the Lower Selkirk Allochthon (part of the Shuswap Complex). Flow up the underthrusting basement ramp resulted in exhumation from mid- to upper-crustal levels. Channel flow then migrated downward to involve basement and overlying cover sequence rocks. Our results indicate that syn-convergent channel flow was a viable and very likely process in the southeastern Canadian Cordillera.

  6. Estructura de los mármoles alpujárrides situados entre Calahonda y Castell de Ferro (Cordillera Bética, provincia de Granada

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    Sanz de Galdeano, C.

    2009-12-01

    Full Text Available The marbles of the Calahonda-Castell de Ferro area present two systems of folds: the first one has a N70°E to E-W direction and the second, according to the observed superposed structures, is N-S. Both systems were deformed under plastic conditions. The strike of the first system is common in the Betic Internal Zone, linked to compression and nappe structuring. The second one, less represented, could be related with the westward drifting of the cited zone. A great number of faults and joints formed in later stages of deformation. The first ones correspond to the continuation of the westward translation of the Internal Zone. The rest of the deformations occurred during the middle Miocene and, particularly, from the Late Miocene onwards.

    Los mármoles de Calahonda-Castell de Ferro presentan dos sistemas de pliegues: uno de dirección N70°E a E-O y otro posterior N-S. Ambos se han formado en condiciones en las que los mármoles tenían una neta plasticidad. La dirección de los primeros pliegues es común en la Zona Interna Bética, ligada a etapas de compresión y emplazamientos de mantos. Los segundos pliegues podrían estar relacionados con el desplazamiento de dicha zona hacia el oeste. Buena parte de las fallas y diaclasas existentes son posteriores e ilustran sobre otras etapas de transcurrencia, exhumación, compresión y extensión. La transcurrencia es la continuación de la traslación hacia el oeste y las siguientes etapas se produjeron durante el Mioceno medio y sobre todo el superior.

  7. Devonian-Carboniferous unconformity in Argentina and its relation to the Eo-Hercynian orogeny in southern South America

    Science.gov (United States)

    López-Gamundí, O. R.; Rossello, E. A.

    1993-04-01

    The Devonian-Carboniferous contact in southern South America, characterized by a sharp unconformity, has been related to the Late Devonian-Early Carboniferous Eo-Hercynian orogeny. The Calingasta-Uspallata basin of western Argentina and the Sauce-Grande basin (Ventana Foldbelt) of eastern Argentina have been selected to characterize this unconformity. The Eo-Hercynian movements were accompanied in western Argentina by igneous activity related to a Late Devonian—Early Carboniferous magmatic arc mainly exposed today along the Andean Cordillera. This magmatic activity is partly reflected also in eastern Argentina (Ventana Foldbelt), where isotopic dates suggest a thermal event also related to the intrusions present to the west in the North Patagonian Massif and Sierras Pampeanas. The scarcity of Lower Carboniferous deposits in the stratigraphic record of southern South America suggests that the Early Carboniferous was a time interval dominated by uplift and erosion followed by widespread subsidence during the Middle and Late Carboniferous. The origin of the Eo-Hercynian orogeny can be linked with the convergence between the Arequipa Massif, and its southern extension, and the South American continent. Its effects are best represented along the ‘Palaeo-Pacific’ margin, although distant effects are discernible in the cratonic areas of eastern South America.

  8. Depositación atmosférica de nitrógeno en un transecto valle longitudinal-cordillera de Los Andes, centro-sur de Chile Atmospheric deposition of nitrogen in a transect from the Central Valley to Cordillera de Los Andes, south-central Chile

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    CARLOS E. OYARZÚN

    2002-03-01

    Full Text Available El aumento de las actividades agrícolas y ganaderas en el centro-sur de Chile puede producir elevadas emisiones de nitrógeno hacia la atmósfera (mayormente NH3. El amoniaco es transportado por corrientes de aire y depositado en el suelo y vegetación. El presente estudio evalúa la depositación atmosférica de compuestos nitrogenados (NO3- y NH4+ en la química de las precipitaciones en un transecto altitudinal de 66 km, desde los alrededores de la ciudad de Osorno (40º 35' S, 72º 57' O, 55 m de altitud hasta la cordillera de Los Andes, Parque Nacional Puyehue (40º 46' S, 72º 11' O, 1.120 m de altitud. En siete sitios, durante el período anual junio-1999 hasta mayo-2000, se registró la precipitación y mensualmente se colectaron muestras de agua para determinar: pH, conductividad y las concentraciones de NO3- y NH4+. La precipitación anual se incrementó desde 1.103 mm en la zona de Osorno hasta 6.799 mm en el sector Antillanca, Parque Nacional Puyehue. Los valores promedio anual del pH registraron escasa variación desde 6,3 en el valle central hasta 5,8 en la cordillera de Los Andes. La conductividad presentó los máximos valores en la proximidad de Osorno (22,9 myS cm-1 para descender a través del transecto en zonas intermedias y alcanzar en la Cordillera de los Andes un valor de 11,3 myS cm-1. Las concentraciones promedio de NO3-Nen la lluvia fluctuaron entre 52,3 myg L-1 en la zona agrícola-ganadera y 6,9 myg L-1 en los bosques del Parque Nacional Puyehue. Las concentraciones de NH4-N variaron entre 699,4 myg L-1 en el sector de Osorno y 37,8 myL-1 en la cordillera de Los Andes. Los valores de N-inorgánico poseen una marcada tendencia estacional en el sector agrícola, con valores máximos en primavera-verano y los mínimos en invierno. Las tasas anuales de depositación atmosférica de NO3-N fluctuaron entre 0,53 y 0,57 kg ha-1 año-1 y las de NH4-N fueron entre 6,4 y 2,8 kg ha-1 año-1 para los sitios agrícola-ganaderos de

  9. Petrography and geochemistry of magmatic units from the western cordillera of Ecuador (0 deg. 30`S): tectonic implications; Petrographie et geochimie des unites magmatiques de la cordillere occidentale d`Equateur (0 deg. 30`S): implications tectoniques

    Energy Technology Data Exchange (ETDEWEB)

    Cosma, L.; Mamberti, M.; Gabriele, P. [Lausanne Univ. (Switzerland). Institut de Mineralogie et Petrographie; Cosma, L.; Lapierre, H.; Jaillard, E.; Mambert, M. [Universite Joseph-Fourier, UPRES A-CNRS 5025, Grenoble I, 38 (France). Institut Dolomieu; Jaillard, E.; Laubacher, G. [ORSTOM, 75 - Paris (France). Dept. RED; Bosch, D. [Montpellier-2 Univ., CNRS-UMR 5567, 34 (France); Desmet, A. [Universite Henri Poincare, 54 - Vandoeuvre-les-Nancy (France). Lab. de Petrologie

    1998-12-31

    The cost and western Cordillera of Ecuador are made of accreted oceanic terranes, separated from from the continental margin by a suture zone containing tectonic slices of mafic rocks. The western Cordillera contains three distinct magmatic units. Ultramafic and mafic cumulates from the suture zone (San Juan slice) represent likely the plutonic roots of oceanic plateau basalts. The mafic cumulates are LREE depleted and Ta and Pb enriched (primitive mantle). Their Nd and Pb isotopic compositions suggest that they derived from an enriched OIB type mantle source. Pre-Coniacian arc-tholeiites present flat REE patterns, low Pb and Th contents, and high {xi}{sub Nd(T=100Ma)} (+7.5 to + 7.9) which are indicative of their derivation from a mantle source. These arc-tholeiites developed likely in an intra-oceanic setting. The Eocene calc-alkaline lavas differ from the arc-tholeiites because they are LREE-enriched and have lower {xi}{sub Nd(T=50Ma)} ratios. Their high Pb and Th contents are probably related to crustal assimilation during the magmas ascent. Their Pb isotopic compositions support involvement of subducted pelagic sediments in their genesis. These lavas represent likely the remnants of a continental calc-alkaline magmatic arc. The continental-arc setting of the Eocene lavas demonstrates that these volcanic rocks postdate the accretion of the western Cordillera, upon which they rest unconformably. Therefore, the accretion of the western Cordillera may have occurred in late Paleocene times, as for part of the oceanic terranes of coastal Ecuador. Nevertheless, the occurrence of a collisional event during late Santonian-early Campanian times is strongly suggested by: the arrival of detrital quartz on oceanic series of the western Cordillera by Campanian-Maastrichtian times, a regional unconformity locally dates early Campanian, the arc-jump observed on coastal Ecuador in Santonian times, and finally a thermal event recognised in the eastern Cordillera around 85-80 Ma

  10. The Balearic Islands in the Alpine Orogeny

    Energy Technology Data Exchange (ETDEWEB)

    Bourrouilh, R.

    2016-10-01

    The place of the Balearic Islands in the Alpine orogeny is examined using detailed sedimentology studies, stratigraphical studies from the Lower Devonian (Lochkovian) to modern times and a careful tectonic review of sedimentary formations from the Western Mediterranean. Despite being considered as the ultimate end of the north-eastern termination of the Betic Cordillera, the history of the Balearic archipelago seems to be closer to the tectonic opening of the Gulf of Valencia and to the Corsica-Sardinia rotation, and thus to the tectonic history of the Western Mediterranean Sea, than to the tectonics of the Betic Cordillera which appear as its symmetrical image with respect to this opening. (Author)

  11. Multiple glacial culminations from the Lateglacial to the late Holocene in central and southern Peru (Invited)

    Science.gov (United States)

    Licciardi, J. M.; Schaefer, J. M.; Rodbell, D. T.; Stansell, N.; Schweinsberg, A.; Finkel, R. C.; Zimmerman, S. R.

    2013-12-01

    Fluctuations in small tropical mountain glaciers serve as sensitive indicators of variations in past and present-day climate. Most of the world's modern tropical glaciers reside in the Peruvian Andes, where a growing number of well-dated glacial records have recently been developed. As additional records are documented, regional patterns of late Pleistocene to Holocene glacial activity have begun to emerge. Here we present a compilation of new and previously obtained 10Be surface exposure ages from boulders on well-preserved moraine successions in two glaciated Andean ranges: the Cordillera Vilcabamba of southern Peru (13°20'S, 72°32'W) and the Huaguruncho massif (10°32'S, 75°56'W), located in central Peru ~450 km northwest of the Vilcabamba. A high-resolution composite chronology that merges >100 10Be measurements on moraine sequences in five glaciated drainages of the Cordillera Vilcabamba reveals the occurrence of at least five discrete glacial culminations from the Lateglacial to the late Holocene. At the Huaguruncho massif, >20 10Be exposure ages obtained from moraine sequences in a south-facing cirque indicate at least three major glacial stages spanning the Lateglacial to the Little Ice Age. The moraine ages at Huaguruncho are broadly correlative with the Vilcabamba moraine chronologies, with some dated moraine belts exhibiting geomorphic expressions that closely resemble those of their coeval counterparts in the Vilcabamba. A recurring finding in both field areas is a mismatch between basal radiocarbon ages from bog and lake sediments and 10Be exposure ages on outboard moraines, which enclose the depositional basins. These age discrepancies suggest that cosmogenic 10Be production rates scaled to high altitudes in the tropics are substantially lower than previous estimates. While we anticipate that future refinements to scaled isotope production rates may significantly affect correlation of 10Be exposure ages in the high Andes with ages derived from

  12. Southern (In)hospitality

    Science.gov (United States)

    Hamilton, Kendra

    2005-01-01

    This article presents the results of "The Status of Race Equity and Diversity in Public Higher Education in the South," an analysis of trends in admissions, enrollment and completion at public colleges and universities in the 19 Southern and border states that maintained segregated systems of higher education in 1954. While work on the…

  13. "Pearl" southern highbush blueberry

    Science.gov (United States)

    ‘Pearl’ is a new southern highbush blueberry (Vaccinium spp. hybrid) developed and released by the United States Department of Agriculture-Agricultural Research Service. The new cultivar has several advantages for growers in the Southeastern U.S. over rabbiteye blueberry cultivars, the most widely ...

  14. 'Pearl' Southern Highbush Blueberry

    Science.gov (United States)

    ‘Pearl’ is a new southern highbush blueberry (Vaccinium spp. hybrid) developed and released by the United States Department of Agriculture Agricultural Research Service. The new cultivar has several advantages for growers in the Southeastern U.S. over rabbiteye blueberry cultivars, the most widely ...

  15. Multilingualism in Southern Africa.

    Science.gov (United States)

    Peirce, Bonny Norton; Ridge, Stanley G. M.

    1997-01-01

    Reviews recent research in multilingualism in Southern Africa, focusing on the role of languages in education, sociolinguistics, and language policy. Much of the research is on South Africa. Topics discussed include language of instruction in schools, teacher education, higher education, adult literacy, language contact, gender and linguistic…

  16. Southern Vietnam since 1975.

    Science.gov (United States)

    Dat, Bao

    1995-01-01

    Discusses social and political changes in southern Vietnam since the end of the Vietnam War. Describes anti-U.S. propaganda used in the schools and media in the years immediately following the war. Contends that younger Vietnamese look forward to a closer relationship with the United States and its people. (CFR)

  17. 'Biloxi' Southern Highbush Blueberry

    Science.gov (United States)

    'Biloxi' tetraploid southern highbush blueberry is a new cultivar developed and released by the Agricultural Reseach Service of the U.S. Department of Agriculture breeding programs in Beltsville, MD, and Poplarville MS. Plants of 'Biloxi' are upright, vigorous and productive. The fruit ripens earl...

  18. Guión de la excursión a la Cordillera Ibérica de la asignatura de Geología Histórica y Regional

    OpenAIRE

    Tent Manclús, José Enrique; Giannetti, Alice; Baeza Carratalá, José Francisco; Yébenes Simón, Alfonso

    2012-01-01

    Esta guía surge como documento complementario al campamento de prácticas de campo de la asignatura de Geología Histórica y Regional del Grado de Geología de la Universidad de Alicante. El objetivo principal de este campamento es el conocimiento de los materiales sedimentarios del Paleozoico, Triásico y Jurásico de la Cordillera Ibérica.

  19. Distribución, ecología y origen de las poblaciones de Vitrina pellucida (O. F. Müller, 1774 y Cepaea nemoralis (Linnaeus, 1758 (Gastropoda, Stylommatophora en las Cordilleras Béticas Orientales (Andalucía, España

    Directory of Open Access Journals (Sweden)

    Arrebola, J. R.

    2000-12-01

    Full Text Available The study of the chorology and ecology of the andalusian terrestrial malacofauna (South of the Iberian Peninsula, has showed the presence of a group of climatic relicts characteristics from the Eurosiberian region, in the Eastern Betics Mountains Chains. The ecology and distribution of two of these species (Vitrina pellucida O. F. Millier, 1774: and Cepaea nemoralis Linnaeus, 1758 is exposed, being the main limiting factor the typical mediterranean summer drought. The adaptative response of these species against the scarcity of water depends on its different ecophysiologies. Vitrina pellucida (eurithermic lives in low-lands where the availability of water along the year is constant, as well as in dry soils of high mountains because of the cold weather. Cepaea nemoralis (stenothermic lives only in habitats with wet soils and heavy vegetal cover placed below 1500 m. The absence of similar vegetation over this altitude and the extreme climate conditions of the High Mediterranean Mountains prevents its appearance, contrarily to the High Eurosiberian Mountains.

    [fr]
    L'étude de la chorologie et de l'écologie de la malacofaune terrestre d'Andalousie (sud de la Péninsule Ibérique, a permis de déterminer la présence, dans les cordillères Bétiques Orientales, d'un groupe de reliques climatiques propres à la région Euro-sibérienne. L'écologie et la distribution de deux de ces espèces (Vitrina pellucida O. F. Müller, 1774 et Cepaea nemoralis Linnaeux, 1758 sont exposées ici, et on montre que le principal facteur limitant est la sécheresse estivale caractéristique du climat méditerranéen. La réponse adaptative de dex deux espèces face à la rareté de l'eau durant l'été est déterminée par leurs écophysiologies différentes, Vitrina pellucida (eurytherme utilise aussi bien les écosystèmes des terres basses là où la disponibilité en eau est constante tout au long de l

  20. Reasons for an outstanding plant diversity in the tropical Andes of Southern Ecuador

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    Michael Richter

    2009-06-01

    Full Text Available Long-term field studies in the scope of a multidisciplinary project in southern Ecuador revealed extraordinary high species numbers of many organismic groups. This article discusses reasons for the outstanding vascular plant diversity using a hierarchical scale-oriented top-down approach (Grüninger 2005, from the global scale to the local microscale. The global scale explains general (paleo- ecological factors valid for most parts of the humid tropics, addressing various hypotheses and theories, such as the “greater effective evolutionary time”, constant input of “accidentals”, the “seasonal variability hypothesis”, the “intermediate disturbance hypothesis”, and the impact of soil fertility. The macroscale focuses on the Andes in northwestern South America. The tropical Andes are characterised by many taxa of restricted range which is particularly true for the Amotape-Huancabamba region, i.e. the so called Andean Depression, which is effective as discrete phytogeographic transition as well as barrier zone. Interdigitation of northern and southern flora elements, habitat fragmentation, geological and landscape history, and a high speciation rate due to rapid genetic radiation of some taxa contribute to a high degree of diversification. The mesoscale deals with the special environmental features of the eastern mountain range, the Cordillera Real and surrounding areas in southern Ecuador. Various climatic characteristics, the orographic heterogeneity, the geologic and edaphic conditions as well as human impact are the most prominent factors augmenting plant species diversity. On microscale, prevailing regimes of disturbance and environmental stresses, the orographic basement, as well as the general role on the various mountain chains are considered. Here, micro-habitats e.g. niches for epiphytes, effects of micro-relief patterns, and successions after small-sized disturbance events are screened. Direct effects of human impact are

  1. Paleomagnetic rotations and the kinematics of the Gibraltar arc

    Science.gov (United States)

    Platzman, E. S.

    1992-04-01

    Paleomagnetic investigations of a Mesozoic limestone sequence around the Gibraltar arc show that there have been large systematic rotations about a vertical axis and imply that there must have been a significant component of westward motion within the Betic-Rif orogenic belt. Rotations of the Late Jurassic and Late Cretaceous limestones in the Betic Cordillera of southern Spain are clockwise, with the exception of the unrotated Sierra Gorda, whereas the Jurassic sites in the Rif Mountains of Morocco are rotated counterclockwise, except in the area around Tetuan. These data are generally consistent with formation of the arc either by a westward-moving Alboran microplate or by extensional collapse of a collisional mountain chain. The former model, however, fails to recognize the nonrigid, nonplate-like character of the Alboran domain and lacks a definable driving mechanism. A model of a collapsing east-west-elongated ridge that takes into account the obliquity of the convergence along the active margin may provide mechanisms both for the observed rotations and for the large westward component of motion, and therefore can explain the geometry of the Gibraltar are.

  2. Detailed geologic field mapping and radiometric dating of the Abanico Formation in the Principal Cordillera, central Chile: Evidence of protracted volcanism and implications for Cenozoic tectonics

    Science.gov (United States)

    Mosolf, J.; Gans, P. B.; Wyss, A. R.; Cottle, J. M.

    2011-12-01

    Many aspects of the long-term evolution of intra-arc processes remain poorly understood, including temporal trends in magmatism, temporal and spatial patterns of volcanism, and styles of arc deformation. The Abanico Formation in the Principal Cordillera of central Chile is a thick, well-exposed section of volcanogenic strata providing a superb locale for the investigation of continental arc dynamics over a 60+ myr timescale. In this study, eight new litho-stratigraphic members of the Abanico Formation are described and mapped in the Río Tinguiririca river area. Mapping and field observations show the Abanico Formation measures up to ~2.5 km in composite stratigraphic thickness. The lower ~1.1 km of the section (> 46 Ma) is dominated by andesitic breccias interbedded with andesite, basaltic andesite, and olivine basalt lavas. The upper 1.4 km of the section (volcanics composed mainly of andesite, basaltic andesite, and basalt lavas. A strong deformational overprint has tilted, folded, and faulted the Abanico map units. Fold axes and reverse faults, both east and west directed, are generally N-S trending. Reverse faults achieve up to ~50 Ma of stratigraphic separation, placing Campanian strata on Miocene rocks with up to ~2 km of vertical throw. The Abanico Formation is also offset by numerous steeply-dipping, oblique-slip faults with 100+ meters of slip. The Abanico Formation is interpreted to have been emplaced within an active arc, with progressively more evolved material being erupted up section during the Campanian to Miocene, followed by more mafic volcanism during the Pliocene and Quaternary. Radiometric ages bounding intra-formational unconformities imply that shortening commenced no later than the early Miocene, with an older deformational episode possibly preceding it. Results of this study clearly demonstrate the age of the Abanico Formation extends from Campanian to Miocene, requiring a significant revision of the current mid-Tertiary age paradigm for

  3. Studies in Neotropical Paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: implications for the uplift history of the Central Andes.

    Science.gov (United States)

    Graham, A; Gregory-Wodzicki, K M; Wright, K L

    2001-09-01

    An assemblage of 33 fossil pollen and spores, recovered from the 3600-m high Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds considerably to our knowledge of three aspects of the region in late Neogene time: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevation of the Central Andes. The plant microfossils recognized are Isoetes, Lycopodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymenophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern spores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cavanillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that this flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano húmedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of ∼10° and 20°C. The Pislepampa flora probably represents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of ∼20°C, a mean annual precipitation between 1000 and 1500 mm, and that part containing most of the identified genera of fossil pollen is found at elevations ∼1200-1400 m. These conditions are thus inferred for the Pislepampa flora; however, because of the uncertainty of the magnitude of global climate change and of possible changes in the ecological range of plant genera, we estimate an error of at least ±1000 m for the paleoelevation estimate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from one-third to one

  4. A ~20,000 year history of glacial variability in the tropical Andes recorded in lake sediments from the Cordillera Blanca, Peru

    Science.gov (United States)

    Stansell, N.; Rodbell, D. T.; Moy, C. M.

    2010-12-01

    Pro-glacial lake sediments from the Cordillera Blanca, Peru contain continuous records of climate variability spanning the Last Glacial Maximum to present day. Here we present results from two alpine lake basins in the Queshgue Valley (9.8°S, 77.3°W) that contain high-resolution records of clastic sediment deposition for the last ~20,000 years. Radiocarbon-dated sediment cores were scanned at 0.5 to 1.0 cm resolution using a profiling x-ray fluorescence scanner for major and minor element distributions. In addition, we measured down-core variations in magnetic susceptibility, organic carbon, biogenic silica and calcium carbonate. Samples of bedrock and sediments from glacial moraines in the Queshgue watershed were analyzed using an ICP-MS in order to fingerprint and trace the source of glacial sediments deposited in the lakes. The bedrock is dominated by a combination of granodiorite with high Sr concentrations and meta-sedimentary rocks with high Zr values. Because the glacial sediments proximal to the modern glacier terminus are composed mostly of the granodiorite end-member, we interpret changes in Sr and clastic sediment concentrations in the lake sediment profiles as proxies for past glacial variability. Preliminary results indicate that glaciers retreated soon after ~14,500 cal yr BP and remained less extensive during the remaining late Glacial Stage and early Holocene. Gradually increasing clastic sediments through the middle and late Holocene indicate that glaciers became progressively larger, or more erosive towards present day. However, this overall Holocene trend of increasing glacier extent was interrupted by multiple periods of centennial- to millennial-scale ice margin retreat. For example, relative peaks in clastic sediments occurred from ~14,500 to 6000, 5600 to 5000, 4600 to 4200, 3600 to 3200, 2800 to 2700, 2400 to 2200, 1750 to 1550, 1100 to 900 cal yr BP, and during the Little Ice Age (~700 to 50 cal yr BP), while periods of low clastic

  5. Astrophysics in Southern Africa

    CERN Document Server

    Whitelock, Patricia A

    2007-01-01

    The government of South Africa has identified astronomy as a field in which their country has a strategic advantage and is consequently investing very significantly in astronomical infrastructure. South Africa now operates a 10-m class optical telescope, the Southern African Large Telescope (SALT), and is one of two countries short listed to host the Square Kilometre Array (SKA), an ambitious international project to construct a radio telescope with a sensitivity one hundred times that of any existing telescope. The challenge now is to produce an indigenous community of users for these facilities, particularly from among the black population which was severely disadvantaged under the apartheid regime. In this paper I briefly describe the observing facilities in Southern Africa before going on to discuss the various collaborations that are allowing us to use astronomy as a tool for development, and at the same time to train a new generation of astronomers who will be well grounded in the science and linked to ...

  6. Metamorfismo y deformación de la Formación Tobífera en la cordillera Riesco, región de Magallanes, Chile: evidencias para su evolución tectónica Metamorphism and deformation of the Tobifera Formation in the Cordillera Riesco, Region of Magallanes, Chile: Evidences for its tectonic evolution

    Directory of Open Access Journals (Sweden)

    G. Galaz

    2005-12-01

    Full Text Available La Formación Tobífera (150 Ma se deposita en parte contemporánea al Complejo Ofiolítico Sarmiento durante un ambiente geodinámico de rifting de la cuenca de Rocas Verdes. Posteriormente se depositan en concordancia sobre ella las unidades cretácicas de las Formaciones Zapata, Punta Barrosa y Cerro Toro. En Cordillera Riesco está compuesta por tobas silíceas, tobas soldadas silíceas, limolitas negras cuarcíferas y lutitas cuarcíferas, afectadas por una deformación milonítica, que desarrolla indicadores cinemáticos dúctiles inversos, con menor componente dextral, que sugiere un movimiento dextral-inverso para la zona de falla. La mineralogía metamórfica y la aplicación de geotermobarómetros reflejan que esta zona milonítica alcanzó condiciones P-T de 6,37 ± 1,1 kb y 399 ± 64°C, respectivamente. Esto sugiere que estas rocas alcanzaron una profundidad entre 19-26 km, posiblemente producto de un evento de subducción reversa que afectó a estas rocas. Además, determinan una facies esquistos verdes para asociaciones minerales en la matriz y facies prehnita-actinolita para asociaciones minerales en vetillas. Este último evento metamórfico sería de carácter retrógrado. Clastos deformados de la Formación Tobífera en brechas de la Formación Cerro Toro, evidencian que ésta se exhumó antes del Cretácico superior. La configuración actual de las estructuras en Cordillera Riesco posiblemente se debe a rotaciones hacia el oeste, producidas dentro del desarrollo de la faja plegada y corrida de Magallanes.The Tobífera Formation (150 Ma was in part deposited contemporaneously with the Sarmiento Ophiolitic Complex during the rifting stage of the Rocas Verdes Basin. Later, the Cretaceous Zapata, Punta Barrosa and Cerro Toro Formations were deposited conformably on top of the Tobìfera. In Cordillera Riesco, it is composed of siliceous tuffs, siliceous welded tuffs, quartzose black shales and siltstones. It is affected by a

  7. Climate change and permafrost stability in the eastern Canada Cordillera:The results of 33 years of measurements

    Institute of Scientific and Technical Information of China (English)

    Stuart; A.Harris

    2009-01-01

    Over the last 33 years,a network of climate stations has been set up at high altitude mountain permafrost sites from Plateau Mountain near Claresholm,Alberta,north to Sheldon Lake on the North Canol Road in the Yukon.Taken together with the data from the US National Weather Service and the Canadian Atmospheric Environment Service,the results indicate a cooling of mean annual air temperature south of Calgary,no significant change in Calgary,a slight warming at Jasper,and a major warming at Summit Lake,west of Fort Nelson.In contrast,the south eastern and central Yukon show only a minor warming trend that lies well within the limits of a sixty-year record measured by the Canadian Atmospheric Environment Service.Along the Mackenzie valley and on the North Slope of Alaska,the mean annual air temperature is rising.Permafrost is aggrading on Plateau Mountain,degrading at Summit Lake,and appears to be stable in southern Yukon and southern Alaska.This is in contrast to the warming occurring on the Arctic coastal plain and along the Mackenzie valley.It therefore appears that changes in climate vary considera-bly from place to place,and even where warming may occur,it may not continue indefinitely.There has been a northward shift of the arctic front due to a weakening of air pressure in the Yukon and Alaska relative to the continental tropical(cT) and maritime polar(mT) air masses to the south.Any actual changes that may be occurring appear to undergo amplification along the Mackenzie valley and Arctic coastal plain and reduction by buffering in the interior Yukon and Alaskan mountains,a result of mi-cro-environmental factors.Continued,careful monitoring of the climate is required and needs to be expanded in the National Parks in the mountains in order to provide data on the changes that may be taking place.Such measurements can provide a sound basis for interpreting ecological and other climate-related data.The existing climate models are not working satisfactorily because

  8. Climate change and permafrost stability in the eastern Canada Cordillera: The results of 33 years of measurements

    Institute of Scientific and Technical Information of China (English)

    Stuart A. Harris

    2009-01-01

    Over the last 33 years, a network of climate stations has been set up at high altitude mountain permafrost sites from Plateau Mountain near Claresholm, Alberta, north to Sheldon Lake on the North Canol Road in the Yukon. Taken together with the data from the US National Weather Service and the Canadian Atmospheric Environment Service, the results indicate a cooling of mean annual air temperature south of Calgary, no significant change in Calgary, a slight warming at Jasper, and a major warming at Summit Lake, west of Fort Nelson. In contrast, the south eastern and central Yukon show only a minor warming trend that lies well within the limits of a sixty-year record measured by the Canadian Atmospheric Environment Service. Along the Mackenzie valley and on the North Slope of Alaska, the mean annual air temperature is rising. Permafrost is aggrading on Plateau Mountain,degrading at Summit Lake, and appears to be stable in southern Yukon and southern Alaska. This is in contrast to the warming occurring on the Arctic coastal plain and along the Mackenzie valley. It therefore appears that changes in climate vary considerably from place to place, and even where warming may occur, it may not continue indefinitely. There has been a northward shift of the arctic front due to a weakening of air pressure in the Yukon and Alaska relative to the continental tropical (cT) and maritime polar (mT) air masses to the south. Any actual changes that may be occurring appear to undergo amplification along the Mackenzie valley and Arctic coastal plain and reduction by buffering in the interior Yukon and Alaskan mountains, a result of micro-environmental factors. Continued, careful monitoring of the climate is required and needs to be expanded in the National Parks in the mountains in order to provide data on the changes that may be taking place. Such measurements can provide a sound basis for interpreting ecological and other climate-related data. The existing climate models are not

  9. Geophysical Exploration of Disseminated and Stockwork deposits associated with plutonic intrusive: A Case study in the eastern flank of the western Cordillera, Colombia

    Science.gov (United States)

    Hernandez, O.; Alexander, G. C.; Pintor, I. M.

    2011-12-01

    Disseminated deposit exploration in the tropics suffers from difficult geological mapping due to thick vegetation, lack of rock outcrop, and extensive but variable saprolitic weathering. Geophysical exploration of these deposits normally includes magnetic, induced polarization and gamma ray spectrometry surveys. The largest RTP Total field magnetic anomaly highs are usually associated with the diorite porphyry intrusive bodies. Normally, diorites are less magnetic than the basaltic rocks. Therefore, where the magnetic anomaly highs are related to the intrusions they can be explained by the intensive mineralization of basic metals including magnetite that are associated with the porphyry intrusions. Regularly, the magnetic anomaly gradients help to delineate local discontinuities that can be interpreted as local faults and joints that can be mineralized. The gamma ray spectrometry is useful to determine the anomalous concentration of Potassium, Uranium and Thorium that can be interpreted in terms of alteration halos and linear discontinuities. The statistical analysis of the data also can determine the intermediate intrusive / extrusive nature of the porphyry intrusions. The use of gamma ray spectrometry helps to determine the concentration of elemental potassium, regardless of the associated potassium mineral species, enabling alteration mapping in a geological setting related to volcanic-associated massive sulphide base metals and gold. The induced polarization survey is useful in outlining sulphide distribution in porphyry deposits related to chargeability anomaly highs. The preliminary results of the geophysical exploration program of the eastern flank of the Western Cordillera in the Andes Mountains of Colombia are discussed.

  10. Time-scales of assembly and thermal history of a composite felsic pluton: constraints from the Emerald Lake area, northern Canadian Cordillera, Yukon

    Science.gov (United States)

    Coulson, Ian M.; Villeneuve, Mike E.; Dipple, Gregory M.; Duncan, Robert A.; Russell, James K.; Mortensen, James K.

    2002-05-01

    Knowledge of the time-scales of emplacement and thermal history during assembly of composite felsic plutons in the shallow crust are critical to deciphering the processes of crustal growth and magma chamber development. Detailed petrological and chemical study of the mid-Cretaceous, composite Emerald Lake pluton, from the northern Canadian Cordillera, Yukon Territory, coupled with U-Pb and 40Ar/ 39Ar geochronology, indicates that this pluton was intruded as a series of magmatic pulses. Intrusion of these pulses produced a strong petrological zonation from augite syenite, hornblende quartz syenite and monzonite, to biotite granite. Our data further indicate that multiple phases were emplaced and cooled to below the mineral closure temperatures over a time-scale on the order of the resolution of the 40Ar/ 39Ar technique (˜1 Myr), and that emplacement occurred at 94.3 Ma. Simple thermal modelling and heat conduction calculations were used to further constrain the temporal relationships within the intrusion. These calculations are consistent with the geochronology and show that emplacement and cooling were complete in less than 100 kyr and probably 70±5 kyr. These results demonstrate that production, transport and emplacement of the different phases of the Emerald Lake pluton occurred essentially simultaneously, and that these processes must also have been closely related in time and space. By analogy, these results provide insights into the assembly and petrogenesis of other complex intrusions and ultimately lead to an understanding of the processes involved in crustal development.

  11. Estrategias de talla en Cueva Corazón (Mave, Palencia. Un yacimiento del Musteriense Antiguo en las estribaciones meridionales de la Cordillera Cantábrica

    Directory of Open Access Journals (Sweden)

    Sánchez Yustos, Policarpo

    2011-06-01

    Full Text Available This article presents a study of the lithic record recently retrieved from Cueva Corazón in the context of a new research projects initiated in 2005. We have detected a variety of long, albeit highly fragmented, operational sequences. A remarkable technological standardization has also been observed, a trait clearly related to the use of good quality raw materials. These observations allow the inference of a complex web of territorial and social interactions. Moreover, Cueva Corazón, due to its chronology and strategic location, can become a future reference point for the study of the Early Mousterian on both sides of the Cantabrian Range.

    Este artículo estudia el registro lítico de Cueva Corazón en el marco de un proyecto de investigación iniciado en 2005. Hemos detectado una variedad y alargamiento de cadenas operativas líticas, frecuentemente fragmentadas, y una elevada estandarización tecnológica asociada a elaboradas estrategias de captación de materias primas de buena calidad. Este hecho permite inferir una complejidad de las redes territoriales y sociales. Por otro lado, su cronología y posición estratégica hacen de este enclave un lugar excepcional para conocer el Musteriense antiguo en ambos lados de la cordillera cantábrica.

  12. Orogenesis, high-T thermal events, and gold vein formation within metamorphic rocks of the Alaskan Cordillera

    Science.gov (United States)

    Goldfarb, R.J.; Snee, L.W.; Pickthorn, W.J.

    1993-01-01

    Mesothermal, gold-bearing quartz veins are widespread within allochthonous terranes of Alaska that are composed dominantly of greenschist-facies metasedimentary rocks. The most productive lode deposits are concentrated in south-central and southeastern Alaska; small and generally nonproductive gold-bearing veins occur upstream from major placer deposits in interior and northern Alaska. Ore-forming fluids in all areas are consistent with derivation from metamorphic devolatilisation reactions, and a close temporal relationship exists between high-T tectonic deformation, igneous activity, and gold mineralization. Ore fluids were of consistently low salinity, CO2-rich, and had ??18O values of 7 ???-12??? and ??D values between -15??? and -35???. Upper-crustal temperatures within the metamorphosed terranes reached at least 450-500??C before onset of significant gold-forming hydrothermal activity. In southern Alaska, gold deposits formed during latter stages of Tertiary, subduction-related, collisional orogenesis and were often temporally coeval with calc-alkaline magmatism. -from Authors

  13. Provencance of the late Proterozoic to early Cambrian metaclastic sediments ot the Sierra de San Luis (Eastern Sierras Pampeanas) and Cordillera Oriental, Argentina

    DEFF Research Database (Denmark)

    Drobe, M.; López de Luchi, M.; Steenken, A.

    2009-01-01

    /204Pb values. Possible source rocks for the different domains could be the Quebrada Choja in the Central Arequipa-Antofalla domain, the Southern domain of the Arequipa-Antofalla basement, the Brazilian shield or southern Africa. Zircon SHRIMP data point to a connection between the Puncoviscana...

  14. Petrology and geochemistry of the high-pressure Nilgiri Granulite Terrane, Southern India

    Science.gov (United States)

    Srikantappa, C.; Ashamanjari, K. G.; Raith, M.

    1988-01-01

    The Nilgiri granulite terrane in Southern India is predominantly composed of late Archaean medium- to coarse-grained enderbitic to charnockitic rocks. The dominant regional foliation strikes N60 to 70E with generally steep dips. Tight minor isoclinal folds have been observed in places. Granoblastic polygonal micro-structures are common and indicate thorough post-kinematic textural and chemical equilibration at conditions of the granulite facies (2.5 Ga ago). Late compressional deformation in connection with the formation of the Moyar and Bhavani shear zones to the north and south of the Nilgiri block, resulted in wide-spread development of weakly to strongly strained fabrics and was accompanied by minor rehydration. Enderbites and charnockites range from tonalitic to granodioritic in composition. A magmatogenic origin of the protoliths is inferred from their chemical characteristics which resemble those of the andesitic to dacitic members of Cordillera-type calc-alkaline igneous suites. A significant lithological feature of the Nilgiri granulite terrane are numerous extended bodies, lenses and pods of gabbroic and pyroxenitic rocks which are aligned conformable to the foliation of the enderbite-charnockite complex and which have also been deformed and metamorphosed at granulite facies conditions.

  15. Two Interesting Southern Objects

    Science.gov (United States)

    Gyulbudaghian, A. L.

    2016-06-01

    Two southern objects are studied. The first, the planetary nebula PK 349-01.1, is of interest because it has a chain of jets ejected from the central star. 12C(1-0) observations of the vicinity of this object reveal red- and blue-shifted molecular outflows. The second object is a star formation region consisting of two groups of IR stars. These groups have a trapezium-like configuration. Two stars in one of these groups are associated with a ring-shaped nebulae. This star formation region is associated with a new radial system of dark globules.

  16. Astrophysics in Southern Africa

    Science.gov (United States)

    Whitelock, Patricia

    2008-03-01

    The government of South Africa has identified astronomy as a field in which their country has a strategic advantage and is consequently investing very significantly in astronomical infrastructure. South Africa now operates a 10-m class optical telescope, the Southern African Large Telescope (SALT), and is one of two countries short listed to host the Square Kilometre Array (SKA), an ambitious international project to construct a radio telescope with a sensitivity one hundred times that of any existing telescope. The challenge now is to produce an indigenous community of users for these facilities, particularly from among the black population which was severely disadvantaged under the apartheid regime. In this paper I briefly describe the observing facilities in Southern Africa before going on to discuss the various collaborations that are allowing us to use astronomy as a tool for development, and at the same time to train a new generation of astronomers who will be well grounded in the science and linked to their colleagues internationally.

  17. Study of southern corn

    Directory of Open Access Journals (Sweden)

    Samavia Mubeen

    2017-07-01

    Full Text Available Southern corn leaf blight is considered the most devastating disease of maize crop, which causes noticeable reduction in crop yield. Inbred lines are useful because they are genotyped, multiple time phenotyping is possible, and genetic uniformity, genetic stability and its vigor make inbred lines suitable to study in diversified environment. In present investigation, 12 maize genotypes viz: NC-2703 (hybrid, NC-2003 (hybrid, SP-3 (inbred line, NCML-73 (inbred line, NRL-6 (inbred line, NRL-4 (inbred line, Soan-3 (variety, Rakaposhi (variety, Margala (variety, EV-1097 (variety, Local-Y (variety, Local-W (variety were tested against southern corn leaf blight under laboratory and field conditions. According to disease severity scale (0–5 inbreds SP-3 and NCML-73 were found highly resistant; Local-W moderately resistance and rest of the genotypes were least resistance in in vitro analysis. In field screening, Margala, NRL-4, EV-1097 showed maximum resistance followed by moderately resistant SP-3, NCML-73, NC-2703, NRL-6 and Local-Y maize genotypes. NC-2003, Rakaposhi and Soan-3 showed least resistance during field evaluation. Cochliobolus heterostrophus showed considerable effects on yield of crop. Significant difference was found in grain yield, plant height, ear height and ear weight while ear placement, ear per plant and infected ear data were non-significant. The results clearly showed the effect on maize genotypes and its yield.

  18. Large mass movements related to deglaciation effects in southern Peru (Cusco)

    Science.gov (United States)

    Giráldez, Claudia; Choquevilca, Walter; Fernández, Felipe; Frey, Holger; García, Javier; Haeberli, Wilfried; Huggel, Christian; Ludena, Sebastián; Rohrer, Mario; Suarez, Wilson

    2013-04-01

    The Andes of Peru are among the regions most severely affected by glacier and high-mountain hazards over the past 100 years. Large-scale disasters with thousands of people killed are on record, including ice/rock avalanches, debris flows, and glacier lake outburst floods (GLOF's). Effects of climate change such as glacier retreat and formation of glacier lakes have been one of the drivers of hazards in the past. Now, there is an increasing concern about the destabilizing effect that recent and further warming has a on perennially frozen bedrock and on steep glaciers in the steep flanks of high-mountain peaks, with potentially severe consequences to ice/rock avalanches, which may impact existing and new lakes, producing far-reaching outburst floods. Risks are also changing due to the socio-economic development in the Andean region and need to be considered using integrative approaches. Most research so far has concentrated on the Cordillera Blanca region where the most devastating disasters occurred during the 20th century. Very little is known about glacier and high-mountain hazards in the southern Peruvian Cordilleras of Cusco although some of the largest debris flows worldwide affected this region in recent years. In fact, very little is known about the nature, origin and exact dimensions of mass movements in this area, and long-term climatic records are neither available. Here we analyze these recent events in the Santa Teresa region based on field work, satellite images, available meteorological data, and numerical modeling of mass movements. These studies are part of a larger effort towards an integrative risk management. Most of the mass movements that caused disasters have their origin in glaciated catchments draining towards Santa Teresa with catchment sizes between about 100 and 300 km2, and glacier areas of 6 to 16 km2 per catchment. It is known that the enormous 1998 debris flow (ca. 25 million m3) that destroyed the Machu Picchu hydropower plant

  19. Los materiales hercínicos de la cordillera ibérica en el contexto del macizo ibérico

    Directory of Open Access Journals (Sweden)

    Liñán, E.

    1988-12-01

    Full Text Available The discontinuity observed between the paleozoic outcrops of the Iberian Mountains and the ones of the Iberian Massif, has been the greatest incovenient to include those ones in a general Hercynian Iberian model. Two hypothesis have been proposed to the respect. One initial hypothesis postulates the inclusion of the Iberian Mountains paleozoic racks in the West Asturian-Leonese Zone (Lotze, 1961; Julivert et al., 1974. Other one postulates a double inelusion: the occidental part of the Iberian Chaines into the West Asturian-Leonese Zone and the oriental part of the Iberian Chaines into the Cantabrian Zona (Liñán, 1983. In this work new geological data are provided for the geological conexion between Cantabrian Zone and the oriental part of the Iberian Chains; they can be summarised in three points. One of them is referred to the paralellism between the Narcea and Paracuellos antiforms. Those antiforms are divided by a tectonic accident, wich separates different Precambrian sequences. Another point deals with the close relation of the stratigraphical sequences of the Paleozoic racks between the Cantabrian region and Iberian region at both sides of the Narcea and Paracuellos antiforms. the last point refers to the study of small outcrops located in the northwest of the Iberian Chains, that show a probably more similar geological structure to the Cantabrian Zone wich was defined as a fold and thrust belt.La falta de continuidad de los afloramientos paleozoicos de la Cordillera Ibérica con los del Macizo Ibérico han venido constituyendo un serio obstáculo para la inclusión de aquéllos dentro de un esquema general para el hercínico ibérico. Dos hipótesis han sido hasta ahora planteadas: su conexión con la Zona Asturoccidental-Leonesa, o su doble conexión con esta zona y con la zona Cantábrica. En este trabajo se aportan nuevos datos geológicos que son congruentes con la prolongación tanto de la Zona Cantábrica como de la Zona

  20. Insights from analyzing and modelling cascading multi-lake outburst flood events in the Santa Cruz Valley (Cordillera Blanca, Perú)

    Science.gov (United States)

    Emmer, Adam; Mergili, Martin; Juřicová, Anna; Cochachin, Alejo; Huggel, Christian

    2016-04-01

    Since the end of Little Ice Age, the Cordillera Blanca of Perú has experienced tens of lake outburst floods (LOFs), resulting in the loss of thousands of lives and significant material damages. Most commonly involving glacial lakes, such events are often directly or indirectly related to glacier retreat. Here we analyze an event on 8th February 2012 involving four lakes and affecting two valleys (Santa Cruz and Artizón) in the northern part of the Cordillera Blanca. Using the combination of field data, satellite images, digital elevation model (DEM) and GIS-based modelling approaches, the main objectives are: (i) to better understand complex multi-lake outburst flood and related foregoing and induced geomorphological processes; and (ii) to evaluate and discuss the suitability, potentials and limitations of the r.avaflow model for modelling such complex process chains. Analyzing field geomorphological evidence and remotely-sensed images, we reconstruct the event as follows: a landslide from the recently deglaciated left lateral moraine of Lake Artizón Alto (4 639 m a.s.l.), characterized by steep slopes and a height of more than 200 m produced a displacement wave which overtopped the bedrock dam of the lake. The resulting flood wave breached the dam of the downstream moraine-/landslide-dammed Lake Artizón Bajo (4 477 m a.s.l.), decreasing the lake level by 10 m and releasing 3 x 105 m3 of water. Significant amounts of material were eroded from the steeper parts of the Artizón Valley (mean slope >15°) and deposited further downstream in the flatter part of the Santa Cruz Valley (mean slope Santa Cruz Valley. Some minor damages to the dam of Lake Jatuncocha were documented. Geomprohological evidence of the event was observed more than 20 km downstream from Lake Artizón Alto. The described multi-LOF event was employed as a particularly challenging test case for the currently developed, GIS-based two-phase dynamic mass flow model r.avaflow. Whilst the test

  1. ESTRUCTURA Y COMPOSICIÓN FLORÍSTICA DE CUATRO BOSQUES ANDINOS DEL SANTUARIO DE FLORA Y FAUNA GUANENTÁ-ALTO RÍO FONCE, CORDILLERA ORIENTAL COLOMBIANA

    Directory of Open Access Journals (Sweden)

    GALINDO-T. ROBINSON

    2003-12-01

    Full Text Available Se caracterizó la composición florística y la estructura de cuatro bosques andinosdel Santuario de Flora y Fauna Guanentá-Alto Río Fonce, zona de reserva forestallocalizada en la Cordillera Oriental de los Andes colombianos. En cada bosque semuestreó 0.1 ha y se censaron todos los individuos con DAP ≥ 1 cm. La riqueza deespecies se relacionó inversamente con la altitud: La Sierra (2400 m presentó 93especies, Chontales Bajo (2800 m 57, El Venado (3000 m 49 y Chontales Alto (3100m 45 especies. Los bosques situados a menor altitud presentaron una marcadadominancia del roble (Quercus humboldtii, con el 49 % y el 69 % del valor deimportancia (IVI, respectivamente. Los bosques situados a mayor altitud fueronmás heterogéneos y no presentaron dominancia de una especie particular: en ElVenado las especies más importantes fueron Graffenrieda uribei, Centroniadichromantha, Clusia elliptica y Ladenbergia macrocarpa (cada una con el 22 a27 % del IVI y en Chontales Alto fueron Ocotea calophylla, Clethra lanata,Paragynoxys neodendroides y Clusia aff. elliptica (cada una con el 20 a 29 % delIVI. En La Sierra y Chontales Bajo la familia con mayor importancia fue Fagaceae (49y 67% del VIF, respectivamente, seguida por Rubiaceae en La Sierra y porMelastomataceae en Chontales Bajo. La familia más importante en El Venado fueMelastomataceae (76 % del VIF, seguida por Clusiaceae (38 % del VIF, mientrasque en Chontales Alto fue Asteraceae (34 % del VIF, seguida por Lauraceae (31 %del VIF.

  2. Las bioconstrucciones de corales y sus facies asociadas durante el Malm en la Cordillera Ibérica Central (provincia de Zaragoza

    Directory of Open Access Journals (Sweden)

    Meléndez, A.

    1987-08-01

    Full Text Available The differents types of bioconstructions and associated facies in the Central Iberian Chain (Higueruelas Formation, Upper Kimmeridgian have been studied. Biohermes of different thickness (decimetric to metric and less lateral continuity are developped, highly colonized by corals, that are associated to oncolitic, bioclastic and oolitic of high energy facies, in marginal areas, near the litoral developpment. At the same time takes place an important set up of mud mounds, with a small coral colonisation, in protected arcas in a inner shelf, or in outer areas, where the action of the waves is not so effective. The environment protection is been generated in some places due to the appearance of oolitic barrier islands.Se estudian los diferentes tipos de bioconstrucciones de corales, y sus facies asociadas, presentes en el sector central de la rama aragonesa de la Cordillera Ibérica, en la Formación Higueruelas (Kimmeridgiense superior. Se desarrollan biohermos de potencias métricas a decimétricas y escasa continuidad lateral, intensamente colonizados por corales coloniales, que se encuentran asociados a facies oncolíticas, bioclásticas y oolíticas de alta energía en zonas marginales, próximas al desarrollo litoral. Al mismo tiempo tiene lugar una importante instalación de mud mounds, con escasa colonización de corales, en zonas protegidas dentro de la plataforma interna o en zonas más externas, donde la acción del oleaje no es efectiva. La protección del medio viene condicionada en algunos puntos por la aparición de islas barrera oolíticas.

  3. Flora y vegetación de suelos crioturbados y hábitats asociados en la Cordillera Blanca, Ancash, Perú

    Directory of Open Access Journals (Sweden)

    Asunción Cano

    2011-05-01

    Full Text Available Entre los años 2006 y 2008, se llevaron a cabo estudios florístico y de vegetación de los suelos crioturbados y hábitats asociados en cuatro localidades de la Cordillera Blanca (Ancash, Perú localizadas por encima de los 4500 m. Se realizaron recolectas botánicas además de transectos de intersección-línea, en los cuales se midió el espacio (en cm ocupado por cada especie. Fueron determinadas 136 especies de plantas vasculares, agrupadas en 65 géneros y 26 familias. Las Magnoliópsida (dicotiledóneas fueron las más diversas con 97 especies, seguidas de las Liliópsidas (Monocotiledóneas con 36. La mayor diversidad está concentrada en las familias Asteraceae y Poaceae (40,63%. Los géneros con mayor riqueza de especies fueron Senecio (18 y Calamagrostis (12. Se registraron 76 especies (54,82% en suelos crioturbados y hábitats asociados; mientras que 60 especies (44,11% fueron colectadas en la vegetación adyacente. El 95,56% de las especies reportadas fueron hierbas perennes. Se caracterizaron cuatro tipos de comunidades vegetales: a comunidad de suelos crioturbados propiamente dicha, b comunidad de suelos crioturbados asociada a pajonal, c comunidad de suelos crioturbados asociada a roquedal seco y d comunidad de suelos crioturbados asociadas a roquedal húmedo. Se indícan las especies características de cada comunidad.

  4. DIVERSIDAD FLORÍSTICA Y ESTRUCTURA DE REMANENTES DE BOSQUE ANDINO EN LA ZONA DE AMORTIGUACIÓN DEL PARQUE NACIONAL NATURAL LOS NEVADOS, CORDILLERA CENTRAL COLOMBIANA

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    Franco Marcela

    2010-06-01

    Full Text Available Se caracterizó la diversidad, la composición fl orística y la estructura de los bosquesde la Reserva Torre Cuatro, la cual hace parte de la zona amortiguadora del ParqueNacional Natural Los Nevados, Cordillera Central de los Andes colombianos. Losremanentes de bosque se subdividieron en tres zonas de acuerdo a la altitud: baja(2650-2900 m, media (3000-3300 m y alta (3400-3750 m, en cada una de las cualesse muestreó 0.1 ha y se censaron todos los individuos con DAP ≥ 2.5 cm. La riquezade especies encontrada para las tres zonas (62 para la baja, 69 para la media y 48para la baja fue superior al promedio registrado para otros bosques andinos situadosa altitudes similares. En todas las zonas la mayor proporción de individuos tuvieronalturas inferiores a 7.2 m. La composición fl orística y la fi sonomía de los bosquesmuestra que los de las zonas baja y media corresponden a los descritos para la franjaandina propiamente dicha, mientras que los de la alta a la franja alto andina. En todaslas zonas las familias con mayor importancia ecológica fueron Melastomataceae yAsteraceae, pero también se destacaron Cunoniaceae en la baja, Betulaceae en lamedia y Ericaceae en la alta. En todas las zonas unas pocas especies sobresalieron porsu mayor importancia ecológica en la comunidad (IVI; en las zonas baja y media lascinco especies con más IVI acumularon aproximadamente el 30% del mismo, mientrasque en la zona alta cerca del 47%. Las especies con más IVI fueron Weinmanniapubescens (32.7 en la zona baja, Alnus acuminata (29.9 en la media y Tibouchinaandreana (33.4 en la alta.

  5. Evidencias de deformación pleistocena en el sistema de falla de La Carrera (32º40'-33º15'ls, Cordillera Frontal de Mendoza

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    Casa Analía Laura

    2010-08-01

    Full Text Available Entre los 32º25' y 33º15' LS, el frente de levantamiento cenozoico de la Cordillera Frontal, muestra signos de reactivación pleistocena y está representado por el sistema de falla de La Carrera. En el margen oriental del cordón del Plata, la distribución de la deformación cuaternaria no es homogénea. A la latitud de la localidad de El Salto, dichas evidencias se concentran en un tramo comprendido entre los 32º55' y 33º05' LS, tanto en el frente serrano como en el piedemonte adyacente. En la montaña, la actividad neotectónica está asociada a la falla Río Blanco, que delimita el frente. En el piedemonte una ramificación de esta falla afectó un pedimento rocoso y su cobertura aluvial pleistocena, mientras que una segunda falla cuaternaria (falla El Salto ascendió tres niveles de pedimentos cuaternarios. Se presentan asimismo escarpas pedemontanas en el aluvio. En ese tramo montañoso, las cuencas de drenaje están poco desarrolladas; allí se han calculado bajos valores del índice de sinuosidad del frente (Smf y de la relación ancho del piso-alto del valle (Vf, y altos valores del índice de longitud-gradiente de cursos (SL. Este conjunto de evidencias sugiere una persistente actividad tectónica cuaternaria a lo largo de segmentos estructurales en el frente montañoso del cordón del Plata y en el área pedemontana asociada. Las evidencias identificadas a la latitud de El Salto, parecen ser la continuación norte de la falla La Aguadita y amplían el alcance de la deformación cuaternaria dentro del sistema de falla de La Carrera.

  6. Evolution of clay mineral assemblages in the Tinguiririca geothermal field, Andean Cordillera of central Chile: an XRD and HRTEM-AEM study

    Science.gov (United States)

    Vázquez, M.; Nieto, F.; Morata, D.; Droguett, B.; Carrillo-Rosua, F. J.; Morales, S.

    2014-08-01

    HRTEM textural evidence shows that clay minerals in the Tinguiririca geothermal field (Andean Cordillera, central Chile) are the result of direct alteration of former volcanic glass and minerals by hydrothermal fluids at similar temperatures to the present day. They show the classical pattern of diagenetic transformation from smectite at the top to illite at the bottom, with the progressive formation of corrensite and chlorite. The high fluid/rock ratio, disposability of necessary cations and absence of previous detrital phyllosilicates allow the consideration of this area as a natural laboratory to establish the extreme ideal conditions for very low-T reactions. Transformations from smectite to R1 illite-smectite (I-S) and from these to R3 mixed-layers occur respectively at 80-120 °C and 125-180 °C. In spite of ideal genetic conditions, the new-formed minerals show all the defective character and lack of textural and chemical equilibrium previously described in the literature for diagenetic and hydrothermal low-temperature assemblages. Chemistry of smectite-illite phases evolves basically through a diminution of the pyrophyllitic component toward a theoretical muscovite (Si4 + + □ -> Al3 ++ K+). However, a second chemical vector (Si4 ++ Mg2 + → Al3 ++ Al3 +), that is, decreasing of the tschermack component, also contributes to the evolution toward the less Si-more Al rich muscovite in relation to the original smectite. Residual Mg (and Fe) from the latter reaction is consumed in the genesis of chloritic phases. Nevertheless, as a consequence of the lack of chemical equilibrium (probably because of the short time-scale of the geothermal alteration processes), the composition of clay minerals is highly heterogeneous at the level of a single sample. Consequently, the respective fields of smectite, R1 I-S and R3 I-S overlap each other, making the distinction among these three phases impossible based exclusively on chemical data.

  7. Deformación cenozoica de la faja plegada y corrida del Aconcagua y Cordillera Frontal: entre los 33°30' y 33°45'S

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    L. B. Giambiagi

    2003-03-01

    Full Text Available Este trabajo presenta nuevos datos sobre la evolución tectónica de los Andes entre los 33º30´ y 33º45´S, los cuales han sido obtenidos a partir del estudio de la estructura de la faja plegada y corrida del Aconcagua y la evolución de la cuenca de antepaís del Alto Tunuyán. La deformación en la faja plegada y corrida comenzó durante el Mioceno temprano a medio con la inversión de antiguas estructuras de rift. Durante el Mioceno medio la deformación migró progresivamente hacia el este, involucrando a las secuencias mesozoicas. Esto generó una cuña orogénica adelgazada hacia el este. Esta faja fue sujeta a períodos de deformación en su sector frontal y períodos de deformación en su sector interno de manera tal de restaurar su ángulo crítico. La discordancia que separa a distintas unidades sinorogénicas neógenas, el cambio en las direcciones de paleocorrientes desde el oeste hacia el nordeste y la presencia de clastos derivados de zonas proximales aportaron evidencias del levantamiento de la Cordillera Frontal a partir de los 9 Ma. Este levantamiento continuó hasta los 6 Ma, luego del cual la faja plegada y corrida y la cuenca de antepaís continuaron deformándose. Las rocas volcánicas pliocenas inferiores a pleistocenas que cubren discordantemente la faja deformada indican que la principal deformación de la zona ocurrió antes del Plioceno bajo.

  8. Estructura duplex plegada en el frente montañoso de la Cordillera Principal, río Atuel, provincia de Mendoza

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    L.V. Dimieri

    2005-12-01

    Full Text Available El objetivo de este trabajo es obtener una reconstrucción estructural de los afloramientos del alto valle del Río Atuel, al sudoeste de la provincia de Mendoza. Esta región forma parte del frente montañoso de la Cordillera Principal que fue construido por medio de sistemas de corrimientos. Cercano a la localidad de El Sosneado, entre los arroyos Blanco y La Manga, la secuencia estratigráfica está compuesta por rocas Mesozoicas que van desde la Formación Auquilco hasta la Formación Malargüe. Esta pila sedimentaria es afectada por sistemas de corrimientos que se despegan de la Formación Auquilco (yeso cuya disposición en la zona de trabajo es moderadamente buzante al este. Este despegue está dirigido hacia el antepaís con sistemas de fallas y plegamiento asociado que se desarrollan encima del mismo. Estos sistemas de fallas parecen conectados con despegues de techo localizados principalmente en la Formación Huitrín y en la Formación Diamante, por lo tanto generando una geometría duplex. El frente de este duplex, que aflora en la margen occidental del Ao. La Manga, muestra a los estratos Mesozoicos invertidos. Esto sugiere que se trata de una estructura con características de un duplex antiformal que ha sido plegado. Una cuña tectónica basamental, que se propaga hacia el antepaís con retrocorrimientos en su frente y que está localizada en el subsuelo de esta región, es la responsable del volcado final de las estructuras descriptas.

  9. Geología y controles estructurales de las áreas de alteración del portezuelo de las Burras (Cordillera Frontal, San Juan

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    Constantino Karkanis

    2004-03-01

    Full Text Available Se describen las características estratigráficas, petrográficas y estructurales de la comarca del portezuelo de las Burras, localizada en la Cordillera Frontal (San Juan, Argentina. Está constituida por un basamento de sedimentitas de la Formación La Puerta (Carbonífero superior - Pérmico inferior y grandes espesores volcánicos y sedimentarios subordinados del Grupo Choiyoi (Pérmico - Triásico, niveles lávicos andesíticos de la Andesita Las Vizcachas (Mesozoico superior ? - Terciario ?, volcanitas de carácter más ácido de la Formación Arroyo de las Chinches (Oligoceno - Mioceno y de volcanitas andesíticas de la Formación Entrecordilleras (Mioceno superior - Pleistoceno. En relación intrusiva se ha identificado al Plutón Entrecordilleras (Neógeno y a otros cuerpos dacíticos pertenecientes presumiblemente a otra facies del mismo plutón. Los cursos del río Manantiales y arroyo Las Burras se disponen sobre una zona de fallamiento transcurrente senestral principal expresado por fallas sintéticas y antitéticas, donde el sector próximo al portezuelo de las Burras constituye un resalto de alivio de transferencia tectónica con características dilatantes. Éste habría controlado la circulación y emplazamiento de fluidos hidrotermales mineralizantes, responsables de las anomalías cromáticas, mineralógicas y geoquímicas detectadas, asociadas a alteraciones hidrotermales de tipo arcillosa y silícea, que alientan un interés sobre la posibilidad de alumbrar acumulaciones económicas de minerales preciosos.

  10. Caracterización de superficies de erosión mediante geomorfología cuantitativa, Altiplano Antioqueño, Cordillera Central de Colombia

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    Xavier Bustos

    2013-01-01

    Full Text Available En el presente trabajo se caracterizan treinta y cinco superficies de erosión (SE en la Cordillera Central de Colombia mediante geomorfología cuantitativa y análisis digital de terreno. Utilizando modelos digitales de elevación (MDE se derivaron las curvas hipsométricas para dichas superficies, y se comparan los resultados desde dos ópticas. Primero, mediante técnicas geoestadísticas utilizando subrutinas elaboradas bajo R, en combinación con el Lenguaje de Consulta Estructurado (SQL. Segundo, mediante sus respectivos valores de integral hipsométrica, lo que permitió discriminar el grado de madurez, juventud y vejez de las mismas. Desde un vista geomático este trabajo contribuye en el empleo de Bases de Datos Geográficas (Geodatabase lo que permite optimizar el tiempo y el número de cálculos en el procesamiento, todo esto fue integrado usando Sistemas de Información Geográfica (SIG. Los resultados obtenidos acá permiten caracterizar las superficies y relacionar su morfología con fenómenos físicos y climáticos tales como: levantamiento superficial del terreno, erosión, incisión de ríos y presencia de fallas. Adicionalmente, este enfoque multidisciplinario podría ser utilizado para caracterizar topo-formas remanentes a lo largo de Suramérica, las cuales son de vital importancia ya que contienen información de la interacción de procesos climáticos y tectónicos a lo largo del tiempo geológico.

  11. Teleseismic tomography of the southern Puna plateau in Argentina and adjacent regions

    Science.gov (United States)

    Bianchi, M.; Heit, B.; Jakovlev, A.; Yuan, X.; Kay, S. M.; Sandvol, E.; Alonso, R. N.; Coira, B.; Brown, L.; Kind, R.; Comte, D.

    2013-02-01

    We performed a teleseismic P wave tomography study using seismic events at both teleseismic and regional distances, recorded by a temporary seismic array in the Argentine Puna Plateau and adjacent regions. The tomographic images show the presence of a number of positive and negative anomalies in a depth range of 20-300 km beneath the array. The most prominent of these anomalies corresponds to a low-velocity body, located in the crust, most clearly seen in the center of the array (27°S, 67°W) between the Cerro Peinado volcano, the Cerro Blanco caldera and the Farallon Negro in the east. This anomaly (southern Puna Magmatic Body) extends from the northern most part of the array and follows the line with the highest density of stations towards the south where it becomes smaller. It is flanked by high velocities on the west and the east respectively. On the west, the high velocities might be related to the subducted Nazca plate. On the northeast the high velocity block coincides with the position of the Hombre Muerto basin in the crust and could be indicating an area of lithospheric delamination where we detected a high velocity block at 100 km depth on the eastern border of the Puna plateau, north of Galan. This block might be related to a delamination event in an area with a thick crust of Paleozoic metamorphic rocks at the border between Puna and Eastern Cordillera. In the center of the array the Southern Puna magmatic body is also flanked by high velocities but the most prominent region is located on the east and is interpreted as part of the Sierras Pampeanas lithosphere with high velocities. The position of the Sierras Pampeanas geological province is key in this area as it appears to limit the extension of the plateau towards the south.

  12. Andesita Cerro Bola: Nueva unidad vinculada al magmatismo mioceno de la Cordillera de Olivares, San Juan, Argentina (30°35´S; 69°30´O Cerro Bola Andesite: New unit linked to the Miocene magmatism of the Olivares Cordillera, San Juan (30°35' S ; 68°30' W

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    A.F. Wetten

    2005-03-01

    Full Text Available El área de estudio se halla en la zona de Tocota, inmediatamente al este de la Cordillera de Olivares, en el borde oriental de la Cordillera Frontal, provincia de San Juan. En ella se encuentran unidades ígneas y sedimentarias del ciclo gondwánico, las que fueron intruidas y cubiertas en relación discordante por cuerpos subvolcánicos y volcánicos asignados anteriormente al ciclo ándico en sentido amplio, los cuales constituyen el principal objeto del presente estudio. Estos cuerpos han sido mapeados a fin de poder caracterizarlos adecuadamente, en el contexto estratigráfico de la región. Los afloramientos de interés han sido reconocidos en el cerro Bola y alrededores, donde se observan distribuidos irregularmente, cubriendo un área superior a 5 km². Las rocas, de coloración gris clara y composición andesítica - fenoandesítica, presentan estructuras de domo y colada. Estos afloramientos serían correlacionables con la unidad volcánica Pircas (Mioceno, la que aflora al oeste, y conformarían un evento magmático posterior al de pórfidos de diferente composición situados tanto en el arroyo Chita como en el cerro Divisadero. La extensión del área involucrada, la uniformidad litológica, el bajo grado de alteración y una edad radimétrica obtenida por el método K/Ar, fueron considerados para proponer a estas volcanitas como una unidad litoestratigráfica de edad miocena superior, con la denominación de Andesita Cerro Bola.The study area is located in the region of Tocota Creek, close to the Cordillera Olivares, eastern border of the Frontal Range, San Juan province. In this place, igneous and sedimentary units belonging to the Gondwanic cycle, were recognized. These units were intruded and unconformably covered by subvolcanic and volcanic bodies, which were commonly referred to the Tertiary or Andean cycle. The study of these bodies is the main proposal of this work. These bodies had been mapped in order to characterize them

  13. 'El león de la cordillera'. Primo Capraro y el desempeño empresario en la región del nahuel Huapi, 1902-1932

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    Méndez Laura

    2009-01-01

    Full Text Available La historia económica de la Patagonia Norte vivió cambios radicales en el período 1902-1932. Bariloche, un pequeño pueblo de frontera sobre la cordillera de los Andes, se convirtió en un centro turístico internacional. Este artículo pretende explicar el proceso de transformación económica de este espacio social, a través del comportamiento empresario de Primo Capraro, un inmigrante italiano que se convirtió en el empresario más importante de la región.

  14. Identificación, caracterización y dinámica de las geoformas glaciales y periglaciales en la Cordillera de los Andes a través de sensores remotos

    OpenAIRE

    Falaschi, Daniel

    2015-01-01

    El presente trabajo de Tesis Doctoral tuvo el objetivo de estudiar los glaciares y glaciares de escombros en tres regiones montañosas a lo largo de la Cordillera de los Andes Argentina: Monte San Lorenzo (Provincia de Santa Cruz), Volcán Domuyo (Provincia de Neuquén), y Nevados de Cachi (Provincia de Salta). Cada uno de estos sitios presenta características climáticas propias, representativas de tres porciones particulares de los Andes: Andes Patagónicos Meridionales, Andes Centrales Meridion...

  15. Nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal: el caso de los pequeños propietarios forestales de la Cordillera de Nahuelbuta (Chile)

    OpenAIRE

    Sergio Monrroy-Concha; Jimmy M. Pincheira Ulbrich

    2013-01-01

    Se evaluó el nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal que poseen los pequeños propietarios forestales en dos territorios de la Cordillera de Nahuelbuta, en Chile. Para ello, se aplicó una encuesta a 53 personas (10% de las viviendas), que abordó cinco temas centrales: (1) uso del bosque nativo, (2) participación en redes sociales y acceso a la información, (3) conocimiento general de la Ley, (4) conocimiento respecto a la administración y (5) fomento de la Ley...

  16. Procedencia y evolución diagenética de las areniscas permo-triásicas de La Cordillera Ibérica (Sierra de Albarracín-Boniches-Talayuelas, provincias de Teruel y Cuenca)

    OpenAIRE

    Peña Zarzuelo, Antonio de la; Arribas, J.; Cruz, B. de la; Marfil, R.

    1987-01-01

    Las series detríticas rojas atribuidas al Permo-Triásico en esta zona de la Cordillera Ibérica comprenden una potente sedimentación terrígena depositada en ambiente fundamentalmente fluvial, controlada por la tectónica que, según ALVARO el al. (1982), representa las primeras etapas de relleno de cuencas de tipo semigraben del aulacógeno celtibérico. A partir de sondeos de testificación continua, realizados por la J. E. N. para una campaña de prospección de uranio, se ha l...

  17. Las adakitas de la Cordillera Patagónica: Nuevas evidencias geoquímicas y geocronológicas The adakites of the Patagonian Cordillera: new geochemical and geochronological evidences

    Directory of Open Access Journals (Sweden)

    V.A. Ramos

    2004-12-01

    0.61 Ma, consistent with melting of the trailing edge of the Nazca plate as ridge collision progressed to the north. Their chemistry contrasts with non-adakitic Miocene retroarc andesites in the Cerro Moyano (~50°15'S region, east of where the Chile ridge collided at ca. 14 Ma. A major difference in this southern region is the relative absence of large late Miocene plateau flows related to a slab window between the Nazca and Antarctic plates. This association suggests that Miocene slab melting in Patagonia required a thermal input from the asthenospheric mantle as well as a young, hot subducting plate. A similar case can be made between Austral Volcanic Zone adakites and extra-Andean Pliocene to Recent basalts.

  18. Ecosistemas presentes y pasados en la Quebrada Benjamín Matienzo (32º 35' - 32º 50' L. S. y 70º 06' L. O., Cordillera de Los Andes, Mendoza, Argentina Present and past ecosystems in the quebrada Benjamín Matienzo (32º 35' - 32º 50'S and 70º 06'W, cordillera de Los Andes, Mendoza, Argentina

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    Mónica C Wingenroth

    2012-09-01

    Full Text Available Los sedimentos de un perfil en la quebrada Benjamín Matienzo, cordillera de Los Andes (32º 35' - 32º 50' L. S. y 70º 06' L. O., aproximadamente a 3400 m de altura, fueron datados en 6400 años AP a los 572 cm de profundidad. El polen identificado en 174 eventos (capas hallados en dicho perfil se relacionó con el polen presente (1980-1981 / 1981-1982. Un total de siete ambientes se definieron en la quebrada, en base a las diferencias registradas entre la cantidad y calidad del polen local, sugiriendo cambios de la vegetación y/o producción de polen, en respuesta a las variaciones en la disponibilidad del agua y la temperatura. A partir de las diferencias detectadas entre la cantidad y calidad del polen alóctono, se infirieron las direcciones predominantes de los vientos que llegaron a Matienzo en cada evento pasado. A su vez para los eventos incluidos en los mencionados ambientes se sugirieron balances acumulativos de la masa de hielo positivos y negativos, derretimiento de las áreas periglaciales congeladas y los correspondientes ciclos solares y su actividad.Sediments from a profile in the quebrada Benjamín Matienzo, cordillera de Los Andes (32º35'-32º50'S and 70º06'W, 3400 m asl, were dated at the bottom of a 572 cm-depth core to 6400 years B.P. The pollen identified in 174 events (layers of the profile was related to the present pollen assemblage (1980-1981 / 1981-1982. Differences between the quantity and quality of the local pollen defined a total of seven environments in the quebrada Benjamín Matienzo and suggested changes in vegetation and/or pollen production due to water availability and temperature variations. In turn, differences between the quantity and quality of the allochthonous pollen were used to infer the predominant wind directions reaching the quebrada Benjamín Matienzo during each past event. In addition, positive and negative cumulative ice mass balance, melting of frozen periglacial areas and correspondence

  19. Geochemical and Textural Constraints on Wehrlite Formation by Melt-rock Reaction in the Shallow Subcontinental Lithospheric Mantle (Oran, Tell Atlas, N-Algeria)

    Science.gov (United States)

    Hidas, Károly; Garrido, Carlos J.; Marchesi, Claudio; Bodinier, Jean-Louis; Louni-Hacini, Amina; Azzouni-Sekkal, Abla; Konc, Zoltán; Dautria, Jean-Marie; Varas-Reus, Maria Isabel

    2017-04-01

    texture are both accompanied with a dispersion of olivine CPO. The lithological, textural and geochemical variations of these xenoliths indicate that wehrlite-forming melt-rock reactions took place in the shallow subcontinental lithospheric mantle beneath the southern limb of the Betic-Rif-Tell orogenic belt during the Neogene geodynamic evolution of the westernmost Mediterranean. REFERENCES 1. Platt, J.P., Behr, W.M., Johanesen, K., Williams, J.R., 2013. The Betic-Rif Arc and Its Orogenic Hinterland: A Review. Annual Review of Earth and Planetary Sciences 41, 313-357. 2. Hidas, K., Booth-Rea, G., Garrido, C.J., Martínez-Martínez, J.M., Padrón-Navarta, J.A., Konc, Z., Giaconia, F., Frets, E., Marchesi, C., 2013. Backarc basin inversion and subcontinental mantle emplacement in the crust: kilometre-scale folding and shearing at the base of the proto-Alborán lithospheric mantle (Betic Cordillera, southern Spain). Journal of the Geological Society 170, 47-55. 3. Frets, E.C., Tommasi, A., Garrido, C.J., Vauchez, A., Mainprice, D., Targuisti, K., Amri, I., 2014. The Beni Bousera peridotite (Rif Belt, Morocco): an oblique-slip low-angle shear zone thinning the Subcontinental Mantle Lithosphere. Journal of Petrology 55, 283-313. 4. Rampone, E., Vissers, R.L.M., Poggio, M., Scambelluri, M., Zanetti, A., 2010. Melt migration and intrusion during exhumation of the Alboran lithosphere: the Tallante mantle xenolith record (Betic Cordillera, SE Spain). Journal of Petrology 51, 295-325. 5. Hidas, K., Konc, Z., Garrido, C.J., Tommasi, A., Vauchez, A., Padrón-Navarta, J.A., Marchesi, C., Booth-Rea, G., Acosta-Vigil, A., Szabó, C., Varas-Reus, M.I., Gervilla, F., 2016. Flow in the western Mediterranean shallow mantle: Insights from xenoliths in Pliocene alkali basalts from SE Iberia (eastern Betics, Spain). Tectonics 35, 2657-2676. 6. Marchesi, C., Konc, Z., Garrido, C.J., Bosch, D., Hidas, K., Varas-Reus, M.I., Acosta-Vigil, A., 2017. Multi-stage evolution of the lithospheric mantle

  20. La cordillera de Nahuelbuta, ¿lugar de naturaleza o de cultura?: concepción del espacio montañés en fuentes españolas del siglo XVI

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    José Manuel Zavala Cepeda

    2008-07-01

    Full Text Available Este artículo analiza las percepciones hispanas del siglo XVI respecto del territorio mapuche situa- do en el área de la cordillera de Nahuelbuta y de los valles que derivan de ella. En particular, examina la manera como Alonso de Ercilla y Zúñiga y Miguel de Olaverría se refieren a lo que se designó el “Estado de Arauco”, las contradicciones presentes en el relato de Ercilla y las inferencias que se pueden hacer de sus respectivas descripciones. Se concluye que el espacio designado como el “Estado de Arauco” comprendió gran parte de la cordillera de Nahuelbuta y de los valles próximos y no solo el área costera de Arauco; con ello se pone de manifiesto la importancia del espacio montañés en las dinámicas interétnicas regionales del siglo XVI en relación a las tierras bajas, lo que ha sido subvalorado en la literatura historiográfica.

  1. Fires in Southern California

    Science.gov (United States)

    2007-01-01

    In what seemed like the blink of an eye, wildfires ignited in the paper-dry, drought-stricken vegetation of Southern California over the weekend of October 20, 2007, and exploded into massive infernos that forced hundreds of thousands of people to evacuate their communities. Driven by Santa Ana winds, fires grew thousands of acres in just one to two days. The fires sped down from the mountains into the outskirts of coastal cities, including San Diego. Dozens of homes have burned to the ground, and at least one person has died, according to local news reports. Several of the fires were burning completely out of control as of October 22. This image of the fires in California was captured at 1:55 p.m. U.S. Pacific Daylight Time on October 22, 2007. Places where MODIS detected actively burning fires are outlined in red. Thick streamers of smoke unfurl over the Pacific Ocean. The brownish plumes are clouds of dust. Fires northwest of Los Angeles seemed calmer at the time of this image than they were the previous day.

  2. NEW BIOSTRATIGRAPHIC DATA ON THE FRAZZANO' FORMATION (LONGI-TAORMINA UNIT: CONSEQUENCES ON DEFINING THE DEFORMATION AGE OF THE CALABRIA-PELORITANI ARC SOUTHERN SECTOR

    Directory of Open Access Journals (Sweden)

    PAOLA DE CAPOA

    1997-11-01

    Full Text Available New biostratigraphic data on the Frazzanò Flysch Formation are presented. This unit is the topmost formation of the stratigraphic succession characterizing the Longi-Taormina Unit, which in turn represents the lowest tectonic unit of the Peloritani Mountains and the only unit in the entire southern sector of the Calabria-Peloritani Arc in which cenozoic terrains have been recognized. The age of the Frazzanò Fm., which as yet has not been well defined, is essential to ascertain the time period during which the tectogenetic phase responsible for the stacking (superposition of the nappes in the Peloritani Mountains occurred . Coltro (1967 reported foraminiferal assemblages of Late Eocene age, but subsequently ages ranging between the Middle Eocene and the Oligocene have been pro posed, none of them supported by new biostratigraphic data. The identification of some coccolithid taxa which appear in the Late Oligocene and Early Miocene allowed us to attribute an age not older than Upper Oligocene to the levels that mark the transition between the Frazzanò Fm.and the underlying Militello Formation, and an age not older than Early Aquitanian to the most recent beds of the Frazzanò Formation. Therefore, the tectogenetic phase responsible for the superposition of the nappes in the Peloritani Mountains, very likely started during the Aquitanian. While these data agree with the evolution of homologous units recognised in the Betic and Rifian sectors, they challenge the Late Oligocene age ascribed to the basal levels of the Stilo-Capo d'Orlando Formation, which lies unconformably over all the tectonic units of the Calabria-Peloritani Arc and pro vides a chronological upper limit to their overthrusting.    

  3. Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ

    Science.gov (United States)

    Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela

    2017-01-01

    The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. Warm periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic

  4. Evolución de las cuencas sinorogénicas de la Cordillera Principal entre 35°- 36° S, Malargüe

    Directory of Open Access Journals (Sweden)

    J. Silvestro

    2005-12-01

    Full Text Available La faja plegada y corrida de Malargüe se encuentra localizada en el extremo sur de la Cordillera Principal a los 35°-36° S. Los estratos de crecimiento preservados en cuencas sintectónicas registraron la cinemática de plegamiento de la faja plegada durante el Cenozoico. La cuenca Pinchera-Ventana, ubicada en el sector oeste del área, está rellena por dos secuencias volcaniclásticas cubiertas por basaltos. En el sector occidental de esta cuenca, las secuencias se adelgazan hacia los anticlinales de La Valenciana y Torrecillas en el oeste y hacia los retrocorrimientos de La Brea en el este, desarrollando discordancias progresivas observadas en el campo. En el sector oriental de la cuenca, el arreglo de facies, la composición de los clastos y la presencia de discordancias sugieren una proveniencia desde el anticlinal Bardas Blancas en el oeste. Dataciones radimétricas de los niveles andesíticos basales (15,1 Ma y de los basaltos al techo (6,7 Ma limitan la edad de esta cuenca al Mioceno medio y superior. La cuenca Malargüe desarrollada en el sector oriental del área de estudio, está rellena por dos secuencias sintectónicas volcaniclásticas, cubiertas por una secuencia postectónica. El análisis sísmico de las secuencias de crecimiento muestra un arreglo divergente relacionado al levantamiento del anticlinal Malargüe en el oeste de la cuenca y un triángulo de crecimiento hacia el este relacionado al levantamiento del anticlinal Chacay. La datación de niveles andesíticos basales en 5,04 Ma y la secuencia postectónica al tope, limitan la edad de la cuenca entre el Mioceno superior y Cuaternario. Estas observaciones indican que los depocentros sedimentarios migraron hacia el antepaís conjuntamente con el avance de la faja plegada en igual sentido.

  5. Variación de la diversidad florística en un mosaico sucesional en la cordillera Central andina (Antioquia, Colombia

    Directory of Open Access Journals (Sweden)

    Diego Giraldo Cañas

    2000-01-01

    Full Text Available Se estudió la variación de la diversidad florística en cinco remanentes de diferentes estadios sucesionales en un bosque húmedo secundario de la cordillera Central de los Andes colombianos, localizado a una altura de 750-1100 m s.m. Se emplearon transectas de 50 m x 2 m, siendo el área total analizada de 2000 m². Sólo fueron considerados los individuos con un DAP ³ 2,54 cm. Los análisis estructurales revelaron la existencia de 837 individuos pertenecientes a 145 especies, distribuidas en 60 familias. Las familias más diversas fueron Leguminosae (14 especies, Melastomataceae (12, Rubiaceae (10 y Arecaceae, Clusiaceae y Lauraceae con 7 especies cada una. Los géneros más ricos fueron Miconia (7 especies e Inga (6 especies. Cerca del 74% de las especies estuvieron representadas por menos de tres individuos, mostrando una distribución muy homogénea. El índice de equidad de Pielou mostró valores cercanos a uno, mientras que el índice de Simpson reveló baja dominancia, contrario a lo que se espera para bosques secundarios. La similitud florística se estimó a partir del índice de Czekanowski, el cual arrojó valores inferiores al 16% entre remanentes. Esto demuestra la gran variación en la composición florística del área estudiada. Los análisis de regresión lineal mostraron que no había relación entre la edad de los remanentes y la diversidad, el número de especies, la equidad y la dominancia de las especies. Esto sugiere que los estadios sucesionales más avanzados no son necesariamente más diversos que los estadios más jóvenes. En el área de estudio, el equilibrio del número de especies es alcanzado tempranamente en el proceso sucesional. Sin embargo, los remanentes se encuentran en desequilibrio taxonómico, lo que fue demostrado con la fuerte variación en la composición florística entre remanentes. Este estudio demuestra que hay un equilibrio entre extinción e inmigración locales

  6. Late Paleozoic to Early Jurassic tectonic development of the high Andean Principal Cordillera, El Indio Region, Chile (29 30°S)

    Science.gov (United States)

    Martin, Mark W.; Clavero R, Jorge; Mpodozis M, Constantino

    1999-01-01

    Regional mapping (1:50,000) and U-Pb and K-Ar geochronology in the El Indio region refines the knowledge of the distribution, lithostratigraphy, and age of the sedimentary, volcanic, and intrusive rocks that comprise the regionally extensive Pastos Blancos Group which is equivalent to the Choiyoi Group of the Argentine Frontal Cordillera. The Pastos Blancos Group (which we elevate to Group status herein) includes at least two diachronous volcanic-sedimentary sequences: an older felsic volcanic and volcaniclastic unit, the Guanaco Sonso sequence, that is Permian in age, and a younger bimodal volcanic and volcaniclastic unit, the Los Tilos sequence that is Middle Triassic to Early Jurassic. Sedimentary rocks of the Los Tilos sequence are transitional upward into the overlying Early to Middle Jurassic shallow marine limestones of the Lautaro Formation. Intrusions that make up the regionally extensive Permian to Early Jurassic plutons of the Chollay and Elqui-Limarı´ batholiths that were previously mapped as a single plutonic association, the Ingaguás Complex, include in the El Indio region at least three discrete intrusive units. These include: Early Permian (280-270 Ma) biotite granites, Early to Middle Triassic (242-238 Ma) silica-rich leucocratic granites and rhyolitic porphyries that made up the bulk of the Chollay Batholith, and a younger Late Triassic-Early Jurassic unit (221-200 Ma) of mainly intrusive rhyolitic porphyries, extrusive domes, and subordinate mafic intrusions and both felsic and mafic dikes, which are coeval with volcanic rocks of the Los Tilos sequence. Our data show that latest Paleozoic to Early Jurassic intrusive, volcanic, and sedimentary rocks in the El Indio region of the High Andes of Chile between 29-30°S likely formed during extension driven processes after the cessation of Carboniferous-Early Permian subduction along the western edge of Gondwana. These processes began by Late Permian time, but instead of recording a single and

  7. The relationship between carbonate facies, volcanic rocks and plant remains in a late Palaeozoic lacustrine system (San Ignacio Fm, Frontal Cordillera, San Juan province, Argentina)

    Science.gov (United States)

    Busquets, P.; Méndez-Bedia, I.; Gallastegui, G.; Colombo, F.; Cardó, R.; Limarino, O.; Heredia, N.; Césari, S. N.

    2013-07-01

    The San Ignacio Fm, a late Palaeozoic foreland basin succession that crops out in the Frontal Cordillera (Argentinean Andes), contains lacustrine microbial carbonates and volcanic rocks. Modification by extensive pedogenic processes contributed to the massive aspect of the calcareous beds. Most of the volcanic deposits in the San Ignacio Fm consist of pyroclastic rocks and resedimented volcaniclastic deposits. Less frequent lava flows produced during effusive eruptions led to the generation of tabular layers of fine-grained, greenish or grey andesites, trachytes and dacites. Pyroclastic flow deposits correspond mainly to welded ignimbrites made up of former glassy pyroclasts devitrified to microcrystalline groundmass, scarce crystals of euhedral plagioclase, quartz and K-feldspar, opaque minerals, aggregates of fine-grained phyllosilicates and fiammes defining a bedding-parallel foliation generated by welding or diagenetic compaction. Widespread silicified and silica-permineralized plant remains and carbonate mud clasts are found, usually embedded within the ignimbrites. The carbonate sequences are underlain and overlain by volcanic rocks. The carbonate sequence bottoms are mostly gradational, while their tops are usually sharp. The lower part of the carbonate sequences is made up of mud which appear progressively, filling interstices in the top of the underlying volcanic rocks. They gradually become more abundant until they form the whole of the rock fabric. Carbonate on volcanic sandstones and pyroclastic deposits occur, with the nucleation of micritic carbonate and associated production of pyrite. Cyanobacteria, which formed the locus of mineral precipitation, were related with this nucleation. The growth of some of the algal mounds was halted by the progressive accumulation of volcanic ash particles, but in most cases the upper boundary is sharp and suddenly truncated by pyroclastic flows or volcanic avalanches. These pyroclastic flows partially destroyed the

  8. Erythrineae (Fabaceae in southern Africa

    Directory of Open Access Journals (Sweden)

    E. F. Franklin Hennessy

    1991-12-01

    Full Text Available The two genera represented in the flora of southern Africa.  Erythrina L. and  Mucuna Adans. are revised. Keys to the indigenous species and the commonly cultivated exotic species are provided.

  9. Invertebrate diversity in southern California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This shapefile displays mean invertebrate diversity within 5 minute grid cells. The Shannon Index of diversity was calculated from Southern California Coastal Water...

  10. Alport syndrome in southern Sweden

    DEFF Research Database (Denmark)

    Persson, U; Hertz, Jens Michael; Wieslander, J

    2005-01-01

    The aim of the present investigation is to study the epidemiology of Alport syndrome in southern Sweden, to search for mutations in the COL4A5 gene and to estimate the mutation frequency.......The aim of the present investigation is to study the epidemiology of Alport syndrome in southern Sweden, to search for mutations in the COL4A5 gene and to estimate the mutation frequency....

  11. Alport syndrome in southern Sweden

    DEFF Research Database (Denmark)

    Persson, U; Hertz, Jens Michael; Wieslander, J

    2005-01-01

    The aim of the present investigation is to study the epidemiology of Alport syndrome in southern Sweden, to search for mutations in the COL4A5 gene and to estimate the mutation frequency.......The aim of the present investigation is to study the epidemiology of Alport syndrome in southern Sweden, to search for mutations in the COL4A5 gene and to estimate the mutation frequency....

  12. Banking in southern Europe

    Directory of Open Access Journals (Sweden)

    Lazarević Žarko

    2014-01-01

    Full Text Available The nations discussed here (Italy, Spain, Portugal and Greece have in common - with the exception of Italy, that is - that they used to be on the margins of European economic and social developments. Only Italy succeeded in industrialising itself already prior to World War I. This fundamental trait also determined the developmental path of modern-era banking. Hereby, two important points in the course of development of banking in the Southern European countries need to be emphasised. To begin with, if the lands of the North-Western Europe were large capital exporters, then the South European nations were the importers of this capital. The role of foreign capital, i.e., foreign banks, was great and irreplaceable in the development of banking. The second element in common was a large role of state in the economy in general. Under the circumstances of underdeveloped entrepreneurial environment, the state, through its economic activities, would become the driving force of overall economic and social development. This was also or especially the case with banking. Role played by the state only began to diminish towards the end of the 1980s, in the course of the processes of deregulation and liberalisation both at the international level as well as within the then European Economic Community or subsequent European Union. Already during the preparatory processes prior to the admission into the European Economic Community, Spain, Greece and Portugal, and, however, Italy as well, but due to European Directives it had to abide by, began comprehensive processes of restructuring their national banking systems. Since the second half of the 1980s, banking systems were subjected to liberalisation, deregulation and privatisation.

  13. Migración boyacense en la cordillera central, 1876-1945: Del altiplano cundiboyacense a los espacion de homogeneización antioqueña

    Directory of Open Access Journals (Sweden)

    2004-01-01

    Full Text Available L'article propose un point de vue historico-sociologique sur le processus migratoire « cundiboyacense » dans la cordillère central colombienne. Il rend compte de l'évolution historique et des phases de la migration, des processus socio-culturels, interprète les éléments déterminants du phénomène et explique le profil de son contact culturel avec l'élément d'ascendance antioquien dans la zone. L'espace andin choisi - les villes de Líbano et Murrillo dans le département de Tolima et la zone du désert de Letras et Manizales dans le département de Caldas - permet d'étudier le rôle historique de la migration inter-régionale du point de vue de son apport démographique, culturel et économique et de la confluence des différents éléments ethniques, et régionaux depuis la deuxième moitié du XIXème siècle. L'étude met en valeur l'importance des facteurs locaux - le manque de terre, la disposition au travail et les violences -, les facteurs externes - les offres de terre et de journaliers -, et les motivations personnelles - contacts personnels et modes de vie - comme autant d'éléments qui entrèrent en interaction durant les différentes phases migratoires et les circonstances historiques liées à la distribution de terres en friche et à l'expansion de la culture du café dans la cordillère centrale colombienne. El artículo ofrece un enfoque histórico-sociológico sobre el proceso migracional cundiboyacense en la cordillera central colombiana. Explica la evolución histórica y las fases de la migración, sus procesos socioculturales, interpreta las determinantes del fenómeno, y explica el perfil de su contacto y consecuente adaptación e integración con el elemento de ascendencia antioqueña en la zona de asentamiento. El espacio andino escogido -municipios del Líbano y Murillo en el departamento del Tolima y la zona del páramo de Letras y Manizales en el departamento de Caldas- permite estudiar el papel hist

  14. Lizards on ice: evidence for multiple refugia in Liolaemus pictus (Liolaemidae) during the last glacial maximum in the Southern Andean beech forests.

    Science.gov (United States)

    Vera-Escalona, Iván; D'Elía, Guillermo; Gouin, Nicolás; Fontanella, Frank M; Muñoz-Mendoza, Carla; Sites, Jack W; Victoriano, Pedro F

    2012-01-01

    Historical climate changes and orogenesis are two important factors that have shaped intraspecific biodiversity patterns worldwide. Although southern South America has experienced such complex events, there is a paucity of studies examining the effects on intraspecific diversification in this part of the world. Liolaemus pictus is the southernmost distributed lizard in the Chilean temperate forest, whose genetic structure has likely been influenced by Pleistocene glaciations. We conducted a phylogeographic study of L. pictus in Chile and Argentina based on one mitochondrial and two nuclear genes recovering two strongly divergent groups, Northern and Southern clades. The first group is distributed from the northernmost limit of the species to the Araucanía region while the second group is distributed throughout the Andes and the Chiloé archipelago in Southern Chile. Our results suggest that L. pictus originated 751 Kya, with divergence between the two clades occurring in the late Pleistocene. Demographic reconstructions for the Northern and Southern clades indicate a decrease in effective population sizes likely associated with Pleistocene glaciations. Surprisingly, patterns of genetic variation, clades age and historical gene flow in populations distributed within the limits of the Last Glacial Maximum (LGM) are not explained by recent colonization. We propose an "intra-Andean multiple refuge" hypothesis, along with the classical refuge hypothesis previously proposed for the biota of the Chilean Coastal range and Eastern Andean Cordillera. Our hypothesis is supported by niche modelling analysis suggesting the persistence of fragments of suitable habitat for the species within the limits of the LGM ice shield. This type of refuge hypothesis is proposed for the first time for an ectothermic species.

  15. Lizards on ice: evidence for multiple refugia in Liolaemus pictus (Liolaemidae during the last glacial maximum in the Southern Andean beech forests.

    Directory of Open Access Journals (Sweden)

    Iván Vera-Escalona

    Full Text Available Historical climate changes and orogenesis are two important factors that have shaped intraspecific biodiversity patterns worldwide. Although southern South America has experienced such complex events, there is a paucity of studies examining the effects on intraspecific diversification in this part of the world. Liolaemus pictus is the southernmost distributed lizard in the Chilean temperate forest, whose genetic structure has likely been influenced by Pleistocene glaciations. We conducted a phylogeographic study of L. pictus in Chile and Argentina based on one mitochondrial and two nuclear genes recovering two strongly divergent groups, Northern and Southern clades. The first group is distributed from the northernmost limit of the species to the Araucanía region while the second group is distributed throughout the Andes and the Chiloé archipelago in Southern Chile. Our results suggest that L. pictus originated 751 Kya, with divergence between the two clades occurring in the late Pleistocene. Demographic reconstructions for the Northern and Southern clades indicate a decrease in effective population sizes likely associated with Pleistocene glaciations. Surprisingly, patterns of genetic variation, clades age and historical gene flow in populations distributed within the limits of the Last Glacial Maximum (LGM are not explained by recent colonization. We propose an "intra-Andean multiple refuge" hypothesis, along with the classical refuge hypothesis previously proposed for the biota of the Chilean Coastal range and Eastern Andean Cordillera. Our hypothesis is supported by niche modelling analysis suggesting the persistence of fragments of suitable habitat for the species within the limits of the LGM ice shield. This type of refuge hypothesis is proposed for the first time for an ectothermic species.

  16. The Southern Ocean CIRCLE initiative

    Science.gov (United States)

    Murphy, E. J.; Ellis-Evans, J. C.

    2003-04-01

    The circumpolar Southern Ocean is the principal ocean connection between the Atlantic, Pacific and Indian Oceans, and exerts a profound influence on world climate through ocean circulation and its major role in the global carbon cycle. It is a major repository of biodiversity and also the only ocean system where significant marine living resources are yet to be fully exploited. However, this key component of the Earth System is still poorly understood, in part due to the logistical problems of a harsh, remote location and the circumpolar nature of the environment. Circumpolar patterns of variability have now been recognized and the current challenge is to understand how, at a circumpolar scale, this variability is generated, its impact on the regional biogeochemical cycles, its interaction with ecosystem processes and the links to global scale processes. Many of these scientific issues can only be addressed by Southern Ocean scale studies, and although a range of national and international research programmes are already targeting particular aspects, the research effort is largely uncoordinated. The European Polar Board is sponsoring a pan-European initiative (Southern Ocean CIRCLE) to coordinate the currently disparate Southern Ocean research effort and this initiative aims to address climate variability, biogeochemical cycling and ecosystem dynamics with particular reference to the links between these aspects in the circumpolar Southern Ocean. This poster outlines the development of the SO CIRCLE initiative, the major areas of science and proposals for implementation. It also outlines how SO CIRCLE will link to other programmes with a Southern Ocean component (e.g. CLIVAR, CliC, GLOBEC, SOLAS). A key aspect of the initiative will be to coordinate European scientific effort in the Southern Ocean with that of the wider international community.

  17. Southern Dust Devils

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 9 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth. Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. In our final dust devil image we are again looking at the southern hemisphere of Mars. These tracks occur mainly on the northeast side of the topographic ridges. Of course, there are many exceptions, which makes understanding the dynamics that initiate the actual dust devil cyclone difficult. Image information: VIS instrument. Latitude -47.6, Longitude 317.3 East (42.7 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed

  18. Tectonic implications of a paleomagnetic study of the Sarmiento Ophiolitic Complex, southern Chile

    Science.gov (United States)

    Rapalini, A. E.; Calderón, M.; Singer, S.; Hervé, F.; Cordani, U.

    2008-06-01

    A paleomagnetic study was carried out on the Late Jurassic Sarmiento Ophiolitic Complex (SOC) exposed in the Magallanes fold and thrust belt in the southern Patagonian Andes (southern Chile). This complex, mainly consisting of a thick succession of pillow-lavas, sheeted dikes and gabbros, is a seafloor remnant of the Late Jurassic to Early Cretaceous Rocas Verdes basin that developed along the south-western margin of South America. Stepwise thermal and alternating field demagnetization permitted the isolation of a post-folding characteristic remanence, apparently carried by fine grain (SD?) magnetite, both in the pillow-lavas and dikes. The mean "in situ" direction for the SOC is Dec: 286.9°, Inc: - 58.5°, α95: 6.9°, N: 11 (sites). Rock magnetic properties, petrography and whole-rock K-Ar ages in the same rocks are interpreted as evidence of correlation between remanence acquisition and a greenschist facies metamorphic overprint that must have occurred during latest stages or after closure and tectonic inversion of the basin in the Late Cretaceous. The mean remanence direction is anomalous relative to the expected Late Cretaceous direction from stable South America. Particularly, a declination anomaly over 50° is suggestively similar to paleomagnetically interpreted counter clockwise rotations found in thrust slices of the Jurassic El Quemado Fm. located over 100 km north of the study area in Argentina. Nevertheless, a significant ccw rotation of the whole SOC is difficult to reconcile with geologic evidence and paleogeographic models that suggest a narrow back-arc basin sub-parallel to the continental margin. A rigid-body 30° westward tilting of the SOC block around a horizontal axis trending NNW, is considered a much simpler explanation, being consistent with geologic evidence. This may have occurred as a consequence of inverse reactivation of old normal faults, which limit both the SOC exposures and the Cordillera Sarmiento to the East. The age of tilting

  19. Support for the Confederate Battle Flag in the Southern United States: Racism or Southern Pride?

    National Research Council Canada - National Science Library

    Joshua D. Wright; Victoria M. Esses

    2017-01-01

    ... in the Southern United States. We evaluate these two competing views in explaining attitudes toward the Confederate battle flag in the Southern United States through a survey of 526 Southerners...

  20. Geología y controles estructurales de las áreas de alteración del portezuelo de las Burras (Cordillera Frontal, San Juan Geology and structural controls on areas of alteration of Portezuelo de las Burras (Cordillera Frontal, San Juan, Argentina

    Directory of Open Access Journals (Sweden)

    Constantino Karkanis

    2004-03-01

    Full Text Available Se describen las características estratigráficas, petrográficas y estructurales de la comarca del portezuelo de las Burras, localizada en la Cordillera Frontal (San Juan, Argentina. Está constituida por un basamento de sedimentitas de la Formación La Puerta (Carbonífero superior - Pérmico inferior y grandes espesores volcánicos y sedimentarios subordinados del Grupo Choiyoi (Pérmico - Triásico, niveles lávicos andesíticos de la Andesita Las Vizcachas (Mesozoico superior ? - Terciario ?, volcanitas de carácter más ácido de la Formación Arroyo de las Chinches (Oligoceno - Mioceno y de volcanitas andesíticas de la Formación Entrecordilleras (Mioceno superior - Pleistoceno. En relación intrusiva se ha identificado al Plutón Entrecordilleras (Neógeno y a otros cuerpos dacíticos pertenecientes presumiblemente a otra facies del mismo plutón. Los cursos del río Manantiales y arroyo Las Burras se disponen sobre una zona de fallamiento transcurrente senestral principal expresado por fallas sintéticas y antitéticas, donde el sector próximo al portezuelo de las Burras constituye un resalto de alivio de transferencia tectónica con características dilatantes. Éste habría controlado la circulación y emplazamiento de fluidos hidrotermales mineralizantes, responsables de las anomalías cromáticas, mineralógicas y geoquímicas detectadas, asociadas a alteraciones hidrotermales de tipo arcillosa y silícea, que alientan un interés sobre la posibilidad de alumbrar acumulaciones económicas de minerales preciosos.The main stratigraphical, petrographical and structural features of the Portezuelo de Las Burras altered area, located in the Cordillera Frontal (San Juan Province, Argentina, are described. The area is composed of the La Puerta Formation (Upper Carboniferous - Lower Permian, thick volcanic and subordinate sedimentary layers of the Choiyoi Group (Permian - Triassic, levels of andesitic lava of Andesita Las Vizcachas (Upper

  1. Evolución de las cuencas sinorogénicas de la Cordillera Principal entre 35°- 36° S, Malargüe Evolution of the foreland basins in the Cordillera Principal, at 35º - 36º S. Malargüe

    Directory of Open Access Journals (Sweden)

    J. Silvestro

    2005-12-01

    Full Text Available La faja plegada y corrida de Malargüe se encuentra localizada en el extremo sur de la Cordillera Principal a los 35°-36° S. Los estratos de crecimiento preservados en cuencas sintectónicas registraron la cinemática de plegamiento de la faja plegada durante el Cenozoico. La cuenca Pinchera-Ventana, ubicada en el sector oeste del área, está rellena por dos secuencias volcaniclásticas cubiertas por basaltos. En el sector occidental de esta cuenca, las secuencias se adelgazan hacia los anticlinales de La Valenciana y Torrecillas en el oeste y hacia los retrocorrimientos de La Brea en el este, desarrollando discordancias progresivas observadas en el campo. En el sector oriental de la cuenca, el arreglo de facies, la composición de los clastos y la presencia de discordancias sugieren una proveniencia desde el anticlinal Bardas Blancas en el oeste. Dataciones radimétricas de los niveles andesíticos basales (15,1 Ma y de los basaltos al techo (6,7 Ma limitan la edad de esta cuenca al Mioceno medio y superior. La cuenca Malargüe desarrollada en el sector oriental del área de estudio, está rellena por dos secuencias sintectónicas volcaniclásticas, cubiertas por una secuencia postectónica. El análisis sísmico de las secuencias de crecimiento muestra un arreglo divergente relacionado al levantamiento del anticlinal Malargüe en el oeste de la cuenca y un triángulo de crecimiento hacia el este relacionado al levantamiento del anticlinal Chacay. La datación de niveles andesíticos basales en 5,04 Ma y la secuencia postectónica al tope, limitan la edad de la cuenca entre el Mioceno superior y Cuaternario. Estas observaciones indican que los depocentros sedimentarios migraron hacia el antepaís conjuntamente con el avance de la faja plegada en igual sentido.The Andean fold-and-thrust belt of Malargüe is located in the foothills of Cordillera Principal at 35º-36º S. The geometry and age of the growth strata preserved in syntectonic

  2. Deformación cenozoica de la faja plegada y corrida del Aconcagua y Cordillera Frontal: entre los 33°30' y 33°45'S Cenozoic deformation of the Aconcagua fold and thrust belt and Cordillera Frontal: between 33º30´ to 33º45´ S

    Directory of Open Access Journals (Sweden)

    L. B. Giambiagi

    2003-03-01

    Full Text Available Este trabajo presenta nuevos datos sobre la evolución tectónica de los Andes entre los 33º30´ y 33º45´S, los cuales han sido obtenidos a partir del estudio de la estructura de la faja plegada y corrida del Aconcagua y la evolución de la cuenca de antepaís del Alto Tunuyán. La deformación en la faja plegada y corrida comenzó durante el Mioceno temprano a medio con la inversión de antiguas estructuras de rift. Durante el Mioceno medio la deformación migró progresivamente hacia el este, involucrando a las secuencias mesozoicas. Esto generó una cuña orogénica adelgazada hacia el este. Esta faja fue sujeta a períodos de deformación en su sector frontal y períodos de deformación en su sector interno de manera tal de restaurar su ángulo crítico. La discordancia que separa a distintas unidades sinorogénicas neógenas, el cambio en las direcciones de paleocorrientes desde el oeste hacia el nordeste y la presencia de clastos derivados de zonas proximales aportaron evidencias del levantamiento de la Cordillera Frontal a partir de los 9 Ma. Este levantamiento continuó hasta los 6 Ma, luego del cual la faja plegada y corrida y la cuenca de antepaís continuaron deformándose. Las rocas volcánicas pliocenas inferiores a pleistocenas que cubren discordantemente la faja deformada indican que la principal deformación de la zona ocurrió antes del Plioceno bajo.This paper presents new insights into the tectonic evolution of the Andes Mountains at 33º30´ to 33º45´ South Latitude. This has been achieved studying the structure of the Aconcagua fold and thrust belt and the evolution of the Alto Tunuyán foreland basin. Thrusting and uplift of the fold and thrust belt began during the Early-Middle Miocene by the inversion of ancient rift structures. Deformation migrated progressively eastward, during middle Miocene times, involving the Mesozoic sequences. This generated a low angle eastward-tapering wedge that was subjected to periods of

  3. Regeneración Natural del Roble Negro (Colombobalanus excelsa, Fagaceae en Dos Poblaciones de la Cordillera Oriental de los Andes, Colombia Natural Regeneration of Black Oak (Colombobalanus excelsa, Fagaceae in Two Populations from the Cordillera Oriental of the Colombian Andes

    Directory of Open Access Journals (Sweden)

    César Augusto Parra Aldana

    2011-12-01

    Full Text Available Colombobalanus excelsa es una especie endémica de la zona andina de Colombia, con cuatro poblaciones aisladas que forman rodales homogéneos denominados robledales negros. Se encuentra en categoría vulnerable de amenaza, debido principalmente a la conversión del bosque para usos agropecuarios; observaciones en campo indican que la regeneración natural bajo su propia cobertura es escasa. Se propone responder las siguientes preguntas: 1. ¿La estructura del bosque evidencia deficiencias en la regeneración natural de dos poblaciones de roble negro localizadas en la cordillera oriental de los Andes? 2. ¿El reclutamiento de fhmoreno@unal.edu.co está limitado por la disponibilidad y viabilidad de las semillas en las dos poblaciones estudiadas? Con este objetivo se establecieron 16 transectos permanentes de 0,1 ha para evaluar la estructura de adultos (DAP>10 cm y de la regeneración natural. Durante un año se realizó monitoreo sobre las épocas de fructificación, lluvia de semillas, germinación y banco de semillas. Los resultados muestran un suministro extremadamente bajo de renuevos y propágulos de roble negro, lo cual potencialmente puede poner en riesgo la persistencia de estos bosques. Esta situación obedece a diversos factores involucrados en el proceso de regeneración: desde baja producción de semillas de los árboles adultos, altos niveles de depredación pre-dispersión, alta proporción de semillas vacías, baja viabilidad de las semillas sanas, hasta alta mortalidad de las semillas sanas y viables que llegan al suelo. Si bien todos estos factores actúan en cascada, el último de ellos es quizás el que ejerce un efecto más dramático en el bajo éxito reproductivo de esta especie.Colombobalanus excelsa is an endemic species of the Andean region of Colombia, with four isolated populations, forming pure stands called black oak forests. It has been classified in the threat category ''Vulnerable'', mainly due to conversion of

  4. Treasures of the Southern Sky

    CERN Document Server

    Gendler, Robert; Malin, David

    2011-01-01

    In these pages, the reader can follow the engaging saga of astronomical exploration in the southern hemisphere, in a modern merger of aesthetics, science, and a story of human endeavor. This book is truly a celebration of southern skies.  Jerry Bonnell, Editor - Astronomy Picture of the Day The southern sky became accessible to scientific scrutiny only a few centuries ago, after the first European explorers ventured south of the equator. Modern observing and imaging techniques have since revealed what seems like a new Universe, previously hidden below the horizon, a fresh astronomical bounty of beauty and knowledge uniquely different from the northern sky. The authors have crafted a book that brings this hidden Universe to all, regardless of location or latitude. Treasures of the Southern Sky celebrates the remarkable beauty and richness of the southern sky in words and with world-class imagery. In part, a photographic anthology of deep sky wonders south of the celestial equator, this book also celebrates th...

  5. GRANDE SERTÃO: Cordilleras

    Directory of Open Access Journals (Sweden)

    Bairon Oswaldo Vélez Escallón

    2012-01-01

    latinoamericana madura. ¿Esas obras aceptan sin tensiones o resistencias esa filiación? Este trabajo explora estos temas y problemas al menos en tres niveles imbricados y en extrema tensión: la acción, la narración y la transcripción o pasaje al texto.

  6. Influence of Unusual Climatic Conditions on the Rapid Rising of Water Level of the Palcacocha Lake and Its Connection with the Emergency Situation in the Cordillera Blanca, Perú.

    Science.gov (United States)

    Vilca, Oscar

    2017-04-01

    Influence of Unusual Climatic Conditions on the Rapid Rising of Water Level of the Palcacocha Lake and Its Connection with the Emergency Situation in the Cordillera Blanca, Perú. Oscar Vilca, Ricardo Durán, Cesar Portocarrero and Benjamín Morales National Institute for Research on Glaciers and Mountain Ecosystems - INAIGEM The climate alterations in 2016 have led to important issues within the Cordillera Blanca. These unusual climate events were evidenced by the rising temperature and the dropping relative humidity between December 2015 and January 2016 this was mainly influenced by the Niño phenomenon (ENSO), as well as subsequent events, like the one that occurred in november 2016, which had no presence of the ENSO, but was more severe, and has had direct influence on accelerated glacier fusion, this resulted the sudden growth of the water flow of the glacier basins of the Cordillera Blanca. Palcacocha was declared a dangerous lake due to its historical growth records. Currently, a partial monitoring to the water level of this lake is performed, and records are registered on a daily basis, with a methodology that includes analysis, quality control and the elaboration of a daily time line of the lake levels (december 2015 - december 2016). Subsequently, by using an area-volume curve, the levels are converted into volume, which can finally be inferred as water flows of net contribution to the lake. The accelerated increase of the level of the lake corresponds to the water flow contributed by glacier fusion, as that period (November 2016) did not record precipitation. The record observed has shown maximum thrust sheets of 22 mm (06/11/216) and 30mm (27/11/2016). This sudden increase of water flows in all the sub-basins with glaciers has caused concern and alarmed the population since the general perception in november pointed to a "drought", the most critical case being, the one that occurred in Jancapampa, where the river flows reached historic maximum levels

  7. An Introduction: Around Southern Modernisms

    Directory of Open Access Journals (Sweden)

    Cunha Leal, Joana

    2016-07-01

    Full Text Available In this special issue you will find a discussion on southern modernisms stemming from an exploratory research project funded by the Portuguese Science Foundation (FCT between 2014 and 2015. As a project, southern modernisms had a theoretical and historiographical focus driven to discuss the resonances of the two words associated in its title, as well as the disquieting effect of their combination in the fields of visual arts and architecture. The first word – modernisms – stood against the standardized canon of modernism, thus bonding the research to the critical revision of that concept occurring in art history since the closing decades of the 20th century; the second word based the project in southern Europe, meaning that Portugal, Spain, Italy and Greece would set the ground for selecting case studies.

  8. Estructura y composición florística de tres robledales en la región norte de la cordillera central de Colombia

    Directory of Open Access Journals (Sweden)

    Juan D León

    2009-12-01

    Full Text Available La alta diversidad florística que albergan los ecosistemas andinos está siendo amenazada por fuertes presiones de origen antrópico. Uno de estos ecosistemas son los robledales, bosques dominados por la especie Quercus humboldtii, que se encuentra seriamente amenazada en Colombia porque su madera es valiosa comercial y dendroenergéticamente. En este estudio, se caracterizó la composición florística y la estructura de tres robledales de los Andes colombianos, con el fin de determinar su similaridad. En cada sitio, se estableció una parcela permanente (5 000 m² donde se muestrearon todos los árboles con D ≥ 10 cm. En los tres sitios, la especie dominante fue Q. humboldtii, pero la similitud florística entre ellos no fue alta. La estructura por clases de tamaño para los tres sitios fue en forma de J invertida, aunque varió la abundancia de individuos por clase diamétrica. Los resultados indican que los robledales estudiados difieren en su composición florística y estructura a pesar de presentar características biofísicas similares. Las diferencias encontradas se deben posiblemente, a los diferentes factores que interactúan en cada sitio como la historia de uso, intensidad y duración de las perturbaciones antrópicas pasadas, topografía, fauna y clima local, que se ven reflejados en los parámetros estructurales de la vegetación.Structure and floristic composition of three oak forests in the northern region of the Central Cordillera in Colombia. Andean ecosystems harbor a high floristic diversity, which is being threatened by human disturbances such us deforestation and by the expansion of the agricultural frontier. One of these ecosystems are the Andean oak forests dominated by Quercus humboldtii, a threatened species in Colombia. We assessed the floristic composition and structure of three Andean oak forests located in three localities (San Andrés de Cuerquia, Belmira and Guarne of Antioquia. The main goal was to determine

  9. Gestión, protección y despoblación en las Reservas de la Biosfera de la Cordillera Cantábrica

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    Santos González, J.

    2016-12-01

    Full Text Available Our study analyses the current status of the Biosphere Reserves on the Cantabrian Mountains, especially the relationships that they have with other Protected Natural Areas with which very often coincide. These relationships concerns management bodies and one of their main problems that has to do with their negative demographic dynamic that has led to an intense depopulation and aging of their local population. Although twelve reserves have been declared, there are still many areas which have not been named reserves but they potentially could. This tells us that we are still far from a Biosphere Reserve of the Great Cantabrian Mountain Range. The management is different depending on the regions: in Asturias, it is the regional administrative department which performs its management; in Galicia, the provincial administrative department and in Castilla and León, it’s the local government who is in charge of its management. Depopulation is one of the most serious problems suffered almost by every Cantabrian reserves and as a process has not stopped yet. The status of the Biosphere Reserve has yet to find its place in the context of other figures that are clearly under protection. In general, the aim of our study is to underline the importance of separating this figure from other more consolidated concerning Protected Natural Areas, and also, to raise awareness about the serious process of aging and depopulation expressed in their territories.Se analiza la situación actual de las Reservas de la Biosfera de la Cordillera Cantábrica, en especial las relaciones que tienen con los Espacios Naturales Protegidos, con los que a menudo coinciden, las relativas a sus órganos de gestión y a uno de sus principales problemas actuales: su dinámica demográfica negativa que ha desembocado en una intensa despoblación y envejecimiento. Aunque se han declarado doce reservas, aún hay muchas zonas que potencialmente lo podían ser, por lo que aún se est

  10. Evaluation of metasomatic changes in an interlayered blueschist-greenschist sequence (Coastal Cordillera, Chile) by combining geochemical data with equilibrium assemblage diagrams

    Science.gov (United States)

    Halama, Ralf; Konrad-Schmolke, Matthias

    2014-05-01

    In the Coastal Cordillera of Central Chile, a spectacular sequence of interlayered blueschists and greenschists occurs in coastal outcrops near Pichilemu. Three explanations are generally proposed to interpret the interlayering of metamorphic rocks that represent distinct metamorphic facies: 1. Differences in the pressure-temperature (P-T) conditions of equilibration and late-stage tectonic juxtaposition, 2. Chemical differences between the layers inherited from the protolith, and 3. Differences in the degree of metasomatic overprint during metamorphism. Investigations of such interlayered sequences can shed light on the mobility of elements and fluid-rock interaction during metamorphism. To identify the processes responsible for interlayering, geochemical analyses were combined with petrologic investigations involving the calculation of isothermal and isobaric binary phase diagrams using the THERIAK-DOMINO [1] software. Major mineral phases in blueschist and greenschist layers are amphibole, white mica, chlorite, and albite with subordinate amounts of titanite, epidote, hematite and apatite. The mineralogy of blueschist and greenschist layers is similar, albeit the modal proportions differ, causing the distinct colouring. Peak P-T conditions of blueschists reach 370±20 °C at 10±1 kbar [2]. The layering on a cm-to-dm scale and the similar mineralogy suggest that both blueschist and greenschist layers experienced a similar P-T evolution. For adjacent blueschist-greenschist pairs, blueschists have consistently higher Si and Na contents, whereas greenschists are relatively enriched in Al, Mg and total Fe. However, the observed major element geochemical trends are inconsistent with magmatic differentiation. For several blueschist-greenschist pairs, ratios of incompatible trace elements, which are indicative of the protolith composition and considered as relatively immobile during low-T metamorphism (Th/Yb, Nb/Yb), are near identical. These features point to

  11. Curved thrusts from associated basin depocenters. Basement Paleozoique the morphologyc control. The Rides Prerifaines in the Volubilis Basin (Rif Cordillera, Morocco)

    Science.gov (United States)

    Roldán, Francisco Javier; Galindo, Jesus; Ruano, Patricia; Chalouan, Ahmed; Pedrera, Antonio; Ahmamoud, Mfedal; Ruiz, Ana; Sanz, Carlos; Benmakhlouf, Mohammed; Lopez, Angel Carlos; Gonzalez, Lourdes

    2014-05-01

    The Volubilis Basin is located between two structural arcs formed by the Prerif Ridges that developed during and after sedimentation (Roldán et al., 2013). The arcs correspond with WSW-verging anticline culminations, limited by NE-SW strike-slip lateral ramps (Chalouan et al., 2006). Sedimentary infill took place during two stages of ridge formation and propagation. The first stage occurred in the Middle Miocene-Early Tortonian? and was determined by the deposition of the Nappe Prérifaine in the northern part of the basin, and continental and marine sediments over the Prerif Ridges. The second one, Late Miocene in age (Tortonian-Messinian), corresponds to the sedimentation of calcarenites and bioclastic limestones at the basin edges, with a lateral transition to white and blue marls towards the center of the basin (Faugères 1978). There is clear evidence of synsedimentary deformation, suggesting the interaction of sedimentation and tectonics. Geophysical data allow us to characterize the stratigraphic architecture of the Volubilis Basin and the geometry of the top of the Paleozoic basement. An approximately N-S Tortonian-Messinian asymmetric depocenter is located close to the front of the eastern arc. This research illustrates the nucleation, progressive thrust bending and segmentation, and the propagation of folds interacting with sedimentation. Thrust nucleation agrees with Paleozoic basement highs under the detachment surface (Roldán et al., 2013). The progressive development of these tectonic structures conditioned the formation, segmentation and final continentalization of the Volubilis Basin, which can be considered as a piggy-back basin (Roldán et al., 2009). References: Chalouan, A., Galindo-Zaldívar, J., Akil, M., Marín, C., Chabli, A., Ruano, P., Bargach, K., Sanz de Galdeano, C., Benmakhlouf, M., Ahmamou, M. and Gourari, I. (2006). Tectonic wedge escape in the southwestern front of the Rif Cordillera (Morocco) . In: Tectonics of the Western

  12. Southern Ocean Iron Experiment (SOFex)

    Energy Technology Data Exchange (ETDEWEB)

    Coale, Kenneth H.

    2005-07-28

    The Southern Ocean Iron Experiment (SOFeX) was an experiment decades in the planning. It's implementation was among the most complex ship operations that SIO has been involved in. The SOFeX field expedition was successful in creating and tracking two experimentally enriched areas of the Southern Ocean, one characterized by low silicic acid, one characterized by high silicic acid. Both experimental sites were replete with abundant nitrate. About 100 scientists were involved overall. The major findings of this study were significant in several ways: (1) The productivity of the southern ocean is limited by iron availability. (2) Carbon uptake and flux is therefore controlled by iron availability (3) In spite of low silicic acid, iron promotes non-silicious phytoplankton growth and the uptake of carbon dioxide. (4) The transport of fixed carbon from the surface layers proceeds with a C:N ratio that would indicate differential remineralization of nitrogen at shallow depths. (5) These finding have major implications for modeling of carbon export based on nitrate utilization. (6) The general results of the experiment indicate that, beyond other southern ocean enrichment experiments, iron inputs have a much wider impact of productivity and carbon cycling than previously demonstrated. Scientific presentations: Coale, K., Johnson, K, Buesseler, K., 2002. The SOFeX Group. Eos. Trans. AGU 83(47) OS11A-0199. Coale, K., Johnson, K. Buesseler, K., 2002. SOFeX: Southern Ocean Iron Experiments. Overview and Experimental Design. Eos. Trans. AGU 83 (47) OS22D-01. Buesseler, K.,et al. 2002. Does Iron Fertilization Enhance Carbon Sequestration? Particle flux results from the Southern Ocean Iron Experiment. Eos. Trans. AGU 83 (47), OS22D-09. Johnson, K. et al. 2002. Open Ocean Iron Fertilization Experiments From IronEx-I through SOFeX: What We Know and What We Still Need to Understand. Eos. Trans. AGU 83 (47), OS22D-12. Coale, K. H., 2003. Carbon and Nutrient Cycling During the

  13. Metamorfismo y deformación de la Formación Tobífera en la cordillera Riesco, región de Magallanes, Chile: evidencias para su evolución tectónica

    Directory of Open Access Journals (Sweden)

    G. Galaz

    2005-12-01

    Full Text Available La Formación Tobífera (150 Ma se deposita en parte contemporánea al Complejo Ofiolítico Sarmiento durante un ambiente geodinámico de rifting de la cuenca de Rocas Verdes. Posteriormente se depositan en concordancia sobre ella las unidades cretácicas de las Formaciones Zapata, Punta Barrosa y Cerro Toro. En Cordillera Riesco está compuesta por tobas silíceas, tobas soldadas silíceas, limolitas negras cuarcíferas y lutitas cuarcíferas, afectadas por una deformación milonítica, que desarrolla indicadores cinemáticos dúctiles inversos, con menor componente dextral, que sugiere un movimiento dextral-inverso para la zona de falla. La mineralogía metamórfica y la aplicación de geotermobarómetros reflejan que esta zona milonítica alcanzó condiciones P-T de 6,37 ± 1,1 kb y 399 ± 64°C, respectivamente. Esto sugiere que estas rocas alcanzaron una profundidad entre 19-26 km, posiblemente producto de un evento de subducción reversa que afectó a estas rocas. Además, determinan una facies esquistos verdes para asociaciones minerales en la matriz y facies prehnita-actinolita para asociaciones minerales en vetillas. Este último evento metamórfico sería de carácter retrógrado. Clastos deformados de la Formación Tobífera en brechas de la Formación Cerro Toro, evidencian que ésta se exhumó antes del Cretácico superior. La configuración actual de las estructuras en Cordillera Riesco posiblemente se debe a rotaciones hacia el oeste, producidas dentro del desarrollo de la faja plegada y corrida de Magallanes.

  14. Threatened plants of Southern Africa

    CSIR Research Space (South Africa)

    Hall, AV

    1980-05-01

    Full Text Available Lists are provided of 1 915 vascular plant taxa regarded to be either extinct or variously threatened in southern Africa, the region south of (but excluding) Angola, Zimbabwe and Mozambique. These include 39 recently extinct taxa} 105 endangered...

  15. Range Extent for southern sea otters 2016

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The GIS shapefile "Range extent of southern sea otters 2016" is a simple polyline representing the geographic distribution of the southern sea otter (Enhydra lutris...

  16. Geological Evidence That Resolves the Baja-BC Controversy: Detrital Zircons Indicate That Vancouver Island Was Adjacent to Southern California in the Late Cretaceous

    Science.gov (United States)

    Guest, B.; Matthews, W.; Coutts, D. S.; Bain, H.; Hubbard, S. M.

    2015-12-01

    The Baja-BC hypothesis is at the center of a great earth sciences controversy. It stems from paleomagnetic observations that require large-scale displacements of continental crust from low latitudes (Baja, California) to moderate latitudes (British Columbia). Many geologists dispute the scale of the displacements due to a lack of corroborating geological evidence. We provide a robust, geological dataset that confirms the paleomagnetic observations. Detrital zircons from Cretaceous to Paleocene sandstone of the Nanaimo Group, which crops out in western Vancouver Island and the Gulf Islands of southwest British Columbia, are analyzed. The data show a clear transition from local 300 Ma grains in the Maastrichtian-Paleogene. An identical pattern is observed in detrital zircon datasets from southern California forearc basin deposits, and schists interpreted as the subducted remnants of forearc deposits. With a high-n dataset (n=3041) we are able to rule out possible >300 Ma source regions in Canada and the northern United States, and uniquely tie Nanaimo Group rocks to the Mojave-Sonora region of SW United States. This implies that at the end of the Cretaceous, Vancouver Island and western mainland BC were adjacent to southern California and northwestern Mexico, requiring 1900 km of displacement during the latest Cretaceous and Paleocene, consistent with paleomagnetic results. An implication of this result is that the western Coast Batholith of southwest BC was positioned between the northern Peninsular Ranges and southern Sierra Nevada batholiths in the late Cretaceous, and likely represents a displaced segment of a once continuous Cordilleran arc batholith. These results have broad implications for our understanding of episodic arc magmatism in the Cordillera, the tectonic evolution of western North America, Laramide orogenesis, the development and extent of the Nevadaplano, and the onset of Basin and Range extension.

  17. Sedimentary record of regional deformation and dynamics of the thick-skinned southern Puna Plateau, central Andes (26-27°S)

    Science.gov (United States)

    Zhou, Renjie; Schoenbohm, Lindsay M.; Sobel, Edward R.; Carrapa, Barbara; Davis, Donald W.

    2016-01-01

    The Puna Plateau, adjacent Eastern Cordillera and the Sierras Pampeanas of the central Andes are largely characterized by thick-skinned, basement-involved deformation. The Puna Plateau hosts ∼N-S trending bedrock ranges bounded by deep-seated reverse faults and sedimentary basins. We contribute to the understanding of thick-skinned dynamics in the Puna Plateau by constraining regional kinematics of the poorly understood southern Puna Plateau through a multidisciplinary approach. On the southeastern plateau, sandstone modal composition and detrital zircon U-Pb and apatite fission-track data from Cenozoic strata indicate basin accumulation during the late Eocene to early Oligocene (∼38-28 Ma). Provenance analysis reveals the existence of a regional-scale basin covering the southern Puna Plateau during late Eocene to early Oligocene time (∼38-28 Ma) that was sourced from both the western plateau and the eastern plateau margin and had a depocenter located to the west. Petrographic and detrital zircon U-Pb data reveal erosion of proximal western and eastern sources after ∼12 Ma, in mid-late Miocene time. This indicates that the regional basin was compartmentalized into small-scale depocenters by the growth of basement-cored ranges continuing into the late Miocene (∼12-8 Ma). We suggest that the Cenozoic history of the southern Puna Plateau records the formation of a regional basin that was possibly driven by lithospheric flexure during the late Eocene to early Oligocene, before the growth of distributed basement-cored ranges starting as early as the late Oligocene.

  18. Unprecedented Fires in Southern Africa

    Science.gov (United States)

    2002-01-01

    The fires that raged across southern Africa this August and September produced a thick 'river of smoke' over the region. NASA-supported studies currently underway on the event will contribute to improved air pollution policies in the region and a better understanding of its impact on climate change. This year the southern African fire season peaked in early September. The region is subject to some of the highest levels of biomass burning in the world. The heaviest burning was in western Zambia, southern Angola, northern Namibia, and northern Botswana. Some of the blazes had fire fronts 20 miles long that lasted for days. In this animation, multiple fires are burning across the southern part of the African continent in September 2000. The fires, indicated in red, were observed by the Advanced Very High Resolution Radiometer (AVHRR) instrument on board the NOAA-14 satellite. The fires generated large amounts of heat-absorbing aerosols (the dark haze), which were observed with the Earth Probe Total Ozone Mapping Spectrometer (TOMS) instrument. These observations were collected as part of a NASA-supported field campaign called SAFARI 2000 (Southern African Regional Science Initiative). The recent six-week 'dry-season' portion of this experiment was planned to coincide with the annual fires. SAFARI 2000 planners tracked the changing location of fires with daily satellite maps provided by researchers at NASA's Goddard Space Flight Center. 'Every year African biomass burning greatly exceeds the scale of the fires seen this year in the western United States,' says Robert Swap of the University of Virginia, one of the campaign organizers. 'But the southern African fire season we just observed may turn out to be an extreme one even by African standards. It was amazing how quickly this region went up in flames.' The thick haze layer from these fires was heavier than campaign participants had seen in previous field studies in the Amazon Basin and during the Kuwati oil fires

  19. Cenozoic back-arc magmatism of the southern extra-Andean Patagonia (44° 30' - 52° S: A review of geochemical data and geodynamic interpretations

    Directory of Open Access Journals (Sweden)

    M. D'Orazio

    2004-12-01

    Full Text Available Huge amounts of basaltic s.l. lavas were persistently erupted along the eastern side of the Andean Cordillera, throughout Cenozoic time, forming extensive plateaus, hundreds of monogenetic scoria cones and other volcanic structures in a continental back-arc setting. The igneous products exposed in the southern sector of the extra-Andean Patagonia (44° 30' - 52° S are dominantly mafic with minor slightly evolved compositions and rare highly differentiated products. The many published chemical analyses of these rocks, indicate that the mafic lavas range from strongly silica - undersaturated basanites to oversaturated basaltic andesites, and that most of the lavas have a typical within-plate geochemical signature. However, a number of lavas, generally erupted in the western-central sectors of Patagonia, are characterized by different distributions of the incompatible elements with high LILE/HFSE and LREE/HFSE ratios. The REE distribution modelling suggests a low degree of melting of a deep (> 70 km garnet-bearing source for the alkaline magmas, and a higher degree of melting of the same source, or an even higher degree of melting of an enriched source, for the subalkaline magmas. The available Sr-Nd-Pb isotope compositions clearly attest to a major geographic variation: the southernmost lavas have lower 87Sr/86Sr and higher 143Nd/144Nd and 206Pb/204Pb ratios with respect to those erupted to the north. On the whole, the Sr-Nd-Pb isotope compositions of the southern Patagonia lavas fall within the typical range of within-plate continental magmas; in addition the Pb isotope ratios fall in the range of the Southern Hemisphere Dupal Pb isotope anomaly. The geochemical variations of the southern Patagonia lavas are discussed in terms of different geochemical components: depleted and enriched sub-slab asthenosphere, enriched continental lithospheric mantle, continental crust and subducted materials. The geodynamic significance is interpreted with in the

  20. Alpine tectonics and rotation pole evolution of Iberia

    Science.gov (United States)

    de Jong, Koen

    1990-12-01

    The geological evolution of the Betic Cordilleras and Pyrenees reflects the Cretaceous and Tertiary rotation pole and kinematic evolution of the Iberian and African plates. New constraints on the Alpine tectonic evolution of the Iberian plate are provided by P- T- t data and regionally consistent stretching lineations from the metamorphic parts of the Betic Cordilleras. High-pressure low-temperature metamorphism in the Betic Cordilleras resulted from continent-continent collision which caused subduction to a maximum depth of 37 km. A preliminary 116 ± 10 Ma radiometric age for this event corresponds to the initiation of seafloor spreading to the west of Iberia which lasted until about 80 Ma. Intracontinental thrusting in the Betics between 99 Ma and 83 Ma took place after subduction ended. E-W to ESE-WNW trending stretching lineations indicate the direction of thrusting, which resulted in extensional strains of 200-600%. The timing of thrusting in the Betics coincides with a 95-80 Ma tectonic phase in northern Africa, during which E-W stretching lineations were formed. The stretching lineations are coincident with the 110-80 Ma motion vector of Africa-Iberia with respect to Eurasia. Thrusting in the Betics and deformation in northern Africa was driven by convergence of Africa-Iberia and Eurasia. Cretaceous deformation is further recorded by terrigeneous sedimentation in the Mauritanian Flysch and by the tectosedimentary evolution of the Malaguide Complex. Crustal thinning, magmatism and metamorphism in the Pyrenees during the 110-85 Ma period is governed by a left-lateral strike-slip of Africa-Iberia with respect to Eurasia around the same rotation pole as thrusting in the Betics. During the 80-54 Ma period the rotation pole was situated west of Gibraltar, near the previous active collision zone. This inhibited large-scale overthrusting and related penetrative deformation in northern Africa and the Betic Cordilleras. Deformation was instead transferred to the

  1. Charnockitic magmatism in southern India

    Indian Academy of Sciences (India)

    H M Rajesh; M Santosh

    2004-12-01

    Large charnockite massifs cover a substantial portion of the southern Indian granulite terrain. The older (late Archaean to early Proterozoic) charnockites occur in the northern part and the younger (late Proterozoic) charnockites occur in the southern part of this high-grade terrain. Among these, the older Biligirirangan hill, Shevroy hill and Nilgiri hill massifs are intermediate charnockites, with Pallavaram massif consisting dominantly of felsic charnockites. The charnockite massifs from northern Kerala and Cardamom hill show spatial association of intermediate and felsic charnockites, with the youngest Nagercoil massif consisting of felsic charnockites. Their igneous parentage is evident from a combination of features including field relations, mineralogy, petrography, thermobarometry, as well as distinct chemical features. The southern Indian charnockite massifs show similarity with high-Ba–Sr granitoids, with the tonalitic intermediate charnockites showing similarity with high-Ba–Sr granitoids with low K2O/Na2 ratios, and the felsic charnockites showing similarity with high-Ba–Sr granitoids with high K2O/Na2O ratios. A two-stage model is suggested for the formation of these charnockites. During the first stage there was a period of basalt underplating, with the ponding of alkaline mafic magmas. Partial melting of this mafic lower crust formed the charnockitic magmas. Here emplacement of basalt with low water content would lead to dehydration melting of the lower crust forming intermediate charnockites. Conversely, emplacement of hydrous basalt would result in melting at higher fH2O favoring production of more siliceous felsic charnockites. This model is correlated with two crustal thickening phases in southern India, one related to the accretion of the older crustal blocks on to the Archaean craton to the north and the other probably related to the collision between crustal fragments of East and West Gondwana in a supercontinent framework.

  2. Megaconferences: view from Southern Africa

    CSIR Research Space (South Africa)

    Turton, A

    2009-02-01

    Full Text Available specifically to the following events: United Na- tions Water Conference in Mar del Plata (1977), Dublin Conference (1992), United Nations Confe- rence on Environment and Development in Rio de Janeiro (1992), Bonn Consultation (2001), Jo- hannesburg Summit... based on first-hand experience. 12 Megaconferences: View from Southern Africa 251 0 2 4 6 8 10 12 14 Mar del Plata, 1977 Dublin, 1992 Rio de Jane iro, 1992 Marrakech, 1997 The Hague, 2000 Bonn, 2001 Johannesburg, 2002 Japan...

  3. Southern Great Plains Safety Orientation

    Energy Technology Data Exchange (ETDEWEB)

    Schatz, John

    2014-05-01

    Welcome to the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ARM) Southern Great Plains (SGP) site. This U.S. Department of Energy (DOE) site is managed by Argonne National Laboratory (ANL). It is very important that all visitors comply with all DOE and ANL safety requirements, as well as those of the Occupational Safety and Health Administration (OSHA), the National Fire Protection Association, and the U.S. Environmental Protection Agency, and with other requirements as applicable.

  4. Caracterización y evolución metamórfica de las rocas ultramáficas de la faja del río de las Tunas, Cordillera Frontal de Mendoza Characteristics and metamorphic evolution of the ultramafic rocks from Río de Las Tunas Belt, Frontal Cordillera of Mendoza.

    Directory of Open Access Journals (Sweden)

    M. Florencia Gargiulo

    2011-12-01

    Full Text Available Se presenta el estudio petro-mineralógico y químico de metaperidotitas y serpentinitas de la faja máfica-ultramáfica del río de Las Tunas, Cordillera Frontal de Mendoza. Las metaperidotitas preservan relictos de Ol, Cpx, Spls.l. (castaño-rojizo y escaso Opx con diferentes proporciones modales, que permiten inferir protolitos de dunitas, dunitas espinélicas, dunitas clinopiroxénicas, wehrlitas, clinopiroxenitas olivínicas y clinopiroxenitas. La secuencia de cristalización observada en los minerales de reemplazo de las fases primarias: Srp+Mgt(±Brc±Chl→àTr±Tlc→�}Ath→à±Spls.s./Ple(verde±Opx, evidencia el proceso de serpentinización inicial seguido de aumento del grado metamórfico hasta alcanzar condiciones equivalentes a la transición entre la facies de anfibolita de alto grado y la facies de granulita. Un segundo evento de serpentinización manifestado por texturas pseudomórficas según Amp y Chl y texturas no pseudomórficas y de recristalización, junto con las secuencias a FeChr→àCrMgtà→Mgt y b Spls.s./Ple(verdeà→Mgt, indican condiciones posteriores de bajo grado vinculadas a la etapa retrógrada del ciclo de metamorfismo regional. Durante esta etapa también se desarrollan zonas de reacción entre los cuerpos ultramáficos y su roca de caja, como consecuencia de un proceso metasomático entre las litologías en contacto. De manera relativamente simultánea, se genera también la carbonatización penetrativa de cuerpos ultramáficos cercanos a los niveles carbonáticos del Complejo Guarguaráz. Durante el estadío final del ciclo metamórfico, se emplazan cuerpos ígneos gondwánicos en el área de estudio, que aportan las condiciones físico-químicas que favorecen la movilización de elementos y la concentración de minerales, además de potenciar el desarrollo de los procesos metasomáticos. Un nuevo evento de serpentinización restringido en zonas de cizalla, concentra la alteración extrema y

  5. El neopaleozoico de la Sierra de Castaño (Cordillera Frontal andina, San Juan, Argentina: Reconstrucción tectónica y paleoambiental The neopaleozoic of the Sierra de Castaño (Andean Cordillera Frontal, San Juan, Argentina: Tectonic and paleoenviromental reconstruction

    Directory of Open Access Journals (Sweden)

    Pedro Busquets

    2013-01-01

    Full Text Available Se efectúa el análisis estratigráfico de la secuencia neopaleozoica aflorante en la Sierra de Castaño (Cordillera Frontal de la provincia de San Juan, donde han sido reconocidas tres unidades estratigráficas. La basal corresponde a la Formación Cerro Agua Negra (Carbonífero tardío-Pérmico temprano?, formada por areniscas y pelitas depositadas en ambiente marino de plataforma somera y litoral. Sobre ella se dispone la Formación San Ignacio, compuesta por sedimentitas silicoclásticas (desde conglomerados hasta pelitas, calizas estromatolíticas-microbiales, rocas volcánicas, en su mayoría de composición mesosilícica y ácida, y depósitos volcanoclásticos. Estas últimas rocas, probablemente depositadas hacia fines del Carbonífero tardío o en el Pérmico más temprano, cubren en discordancia angular a las de la Formación Cerro Agua Negra en la Sierra de Castaño. Dentro de la Formación San Ignacio fueron identificadas 3 asociaciones de facies sedimentarias. La inferior (AFa está formada por brechas, conglomerados brechosos y areniscas líticas, sedimentadas en sistemas aluviales y fluviales entrelazados que rellenaron una irregular topografía labrada sobre la Formación Cerro Agua Negra. La asociación de facies media (AFb, compuesta por conglomerados, areniscas y pelitas, desarrolla ciclos granodecrecientes de escala métrica muy probablemente originados en sistemas fluviales de alta sinuosidad. La asociación de facies superior (AFc comprende calizas estromatolíticas microbiales, pelitas, niveles de volcanitas y piroclastitas, originadas en cuerpos de aguas someros sujetos a recurrente actividad volcánica. La Formación San Ignacio permite caracterizar el pasaje entre las sucesiones no volcánicas de la Formación Cerro Agua Negra y el intenso magmatismo representado en el Grupo Choiyoi (Pérmico medio-Triásico Inferior. Además demuestra la existencia de dos eventos mayores de deformación tectónica en la regi

  6. El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas The Cenozoic of the upper Teno River, Cordillera Principal, Central Chile: stratigraphy, plutonism and their relation with deep structures

    Directory of Open Access Journals (Sweden)

    José Piquer

    2010-01-01

    Full Text Available La evolución geológica cenozoica del sector central de la Cordillera Principal a ~35°S, se encuentra íntimamente relacionada con la evolución de estructuras profundas, las cuales habrían controlado, en distintas etapas de su historia, tanto la depositación de secuencias volcano-sedimentarias como el ascenso y emplazamiento de cuerpos intrusivos. Estudios estratigráficos en el entorno de estas estructuras, permiten confirmar la edad cenozoica de un conjunto de rocas piroclásticas y sedimentarias que subyacen concordantemente a lavas andesíticas de la Formación Abanico (asignada al Eoceno Tardío-Mioceno Temprano a Medio. Se determinó la existencia de cuatro fases intrusivas principales (diorita, granodiorita, pórfido riodacítico y pórfido dacítico, en ese orden de intrusión, cuyos productos afloran siguiendo una franja de orientación norte-sur. La granodiorita fue datada en 7,8±0,4 Ma (K-Ar en biotita. Pórfidos riodacíticos, considerados como facies marginales de la unidad anterior, se dataron en 7,9±0,4 Ma (K-Ar en fenocristales de plagioclasa. Se reconocieron dos estructuras de importancia regional: el Corrimiento El Fierro, y, más al oeste, se definió el Sistema de Fallas Infiernillo-Los Cipreses. En la caracterización de esta última estructura, se utilizó la modelación magnética de secciones como complemento a la información geológica. Se interpreta que el ascenso de las distintas fases intrusivas mencionadas fue controlado por el Sistema de Fallas Infiernillo-Los Cipreses. Este, al igual que el Corrimiento El Fierro, habría actuado como una falla normal de borde de cuenca durante el Eoceno Tardío-Moceno Medio, controlando la depositación de productos volcánicos y sedimentarios de la Formación Abanico. Ambas fallas fueron reactivadas en modo inverso durante un importante episodio de contracción tectónica y de elevada presión de fluidos inducida por circulación de magmas, en el Mioceno Tard

  7. Southern Appalachian Regional Seismic Network

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M. [Memphis State Univ., TN (United States). Center for Earthquake Research and Information

    1994-08-01

    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.

  8. Atmospheric Chemistry Over Southern Africa

    Science.gov (United States)

    Gatebe, Charles K.; Levy, Robert C.; Thompson, Anne M.

    2011-01-01

    During the southern African dry season, regional haze from mixed industrial pollution, biomass burning aerosol and gases from domestic and grassland fires, and biogenic sources from plants and soils is worsened by a semi-permanent atmosphere gyre over the subcontinent. These factors were a driver of several major international field campaigns in the 1990s and early 2000s, and attracted many scientists to the region. Some researchers were interested in understanding fundamental processes governing chemistry of the atmosphere and interaction with climate change. Others found favorable conditions for evaluating satellite-derived measurements of atmospheric properties and a changing land surface. With that background in mind a workshop on atmospheric chemistry was held in South Africa. Sponsored by the International Commission for Atmospheric Chemistry and Global Pollution (ICACGP; http://www.icacgp.org/), the workshop received generous support from the South African power utility, Eskom, and the Climatology Research Group of the University of the Witwatersrand, Johannesburg, South Africa. The purpose of the workshop was to review some earlier findings as well as more recent findings on southern African climate vulnerability, chemical changes due to urbanization, land-use modification, and how these factors interact. Originally proposed by John Burrows, president of ICACGP, the workshop was the first ICACGP regional workshop to study the interaction of air pollution with global chemical and climate change. Organized locally by the University of the Witwatersrand, the workshop attracted more than 60 delegates from South Africa, Mozambique, Botswana, Zimbabwe, France, Germany, Canada, and the United States. More than 30 presentations were given, exploring both retrospective and prospective aspects of the science. In several talks, attention was focused on southern African chemistry, atmospheric pollution monitoring, and climate processes as they were studied in the field

  9. Crustal transects across the Rif domains in North Morocco, from the RIFSIS seismic survey

    Science.gov (United States)

    Gil de la Iglesia, A.; Gallart, J.; Diaz Cusi, J.; Carbonell, R.; Levander, A.; Palomeras, I.; Harnafi, M.

    2013-12-01

    In October 2011, two 300 km-long NS and EW wide-angle seismic transects were carried out in N Morocco, across main domains of Rif cordillera, in a joint effort from Spanish-Moroccan-USA scientists. Main goal of the RIFSIS survey was to achieve, for the first time, detailed crustal velocity-depth models on the southern flank of the Gibraltar Arc System. This asymmetric, arcuated system surrounding the Alboran Sea and composed by the Betic ranges on the N and the Rif cordillera on the S has undergone a complex tectonic evolution since Miocene times. Different types of evolutionary models have been proposed in the last decades, poorly constrained by the available geophysical results, specially on the southern flank, where crustal depths around 30 km have been proposed from inversion modeling of potential field datasets, in contrast with greater values up to 40 km depths and significant lateral variations from RF analysis. In the RIFSIS survey, almost 1000 Texans stations were deployed along the two profiles and 3 shots of 1 T were detonated along each one. The NS transect was extended northwards in Spain by a 75 km long segment in the Betics, and southwards it connects with an analogous profile recorded in 2010 across the Atlas Mountains (SIMA project), hence providing a 700 km long continuous seismic transect sampling the different tectonic domains. The high density of recording stations allows building up of vertical seismic sections focused on the Moho PmP reflections that reveal important variations along this transect. An extensive analysis based on travel time forward modeling has also been performed and main results are presented here. The interpreted crustal structure differentiates two sedimentary layers on top of the basement, inferred from the observed first arrivals at short offsets, followed by upper, mid and lower crustal levels constrained by reflected phases visible in the record sections. The bottom of the crust is well defined from PmP phases

  10. ESTRUCTURA, DIVERSIDAD Y DINÁMICA DE LA VEGETACIÓN EN EL ECOTONO BOSQUE-PÁRAMO: REVISIÓN DE LA EVIDENCIA EN LA CORDILLERA DE MÉRIDA

    Directory of Open Access Journals (Sweden)

    Luis Daniel LLAMBÍ

    2015-07-01

    Full Text Available En los Andes tropicales, el límite altitudinal de los bosques corresponde a una compleja zona de transición entre el bosque paramero y el páramo andino. En el límite inferior de esta zona ocurre a su vez una transición gradual entre el bosque y las selvas nubladas. La ordenación del territorio en estos ecosistemas se ha convertido en un tema prioritario en virtud de la creciente amenaza que representan para su conservación las actividades agropecuarias y la minería. En este trabajo se revisaron las investigaciones realizadas en la Cordillera de Mérida (Venezuela sobre los cambios en la estructura, diversidad y respuesta a disturbios de la vegetación a lo largo del ecotono bosque-páramo. Los resultados de estas investigaciones documentan la alta riqueza de especies y formas de vida que caracterizan la vegetación del ecotono, así como una alta tasa de recambio de especies a lo largo del gradiente de elevación. Así mismo, estudios sobre la dinámica sucesional de la vegetación en áreas intervenidas por la agricultura en diferentes posiciones a lo largo de la transición, indican que las leñosas del bosque muestran una capacidad mucho menor de colonización de las áreas perturbadas que las especies dominantes del páramo. Con base en la evidencia disponible, se discuten elementos estructurales que pueden servir de base para la delimitación de los ecosistemas presentes en la zona de transición y se enfatiza la necesidad de diseñar estrategias de conservación y restauración asistida que partan de interpretar el ecotono bosque-páramo como una unidad dinámica integrada.Vegetation Structure, Diversity and Dynamics in the Forest-Paramo Ecotone: A Review of the Evidence in the Cordillera de MéridaIn the tropical Andes, the mountain treeline corresponds to a complex transition zone between páramo forests and páramos. In the lower limit of this ecotone there is a more or less gradual transition between mountain cloud forests and

  11. Modification of Thickened Orogenic Crust by a Subducting Ridge: Disruption of the Andean Lower Crust of Southern Peru by the Subducting Aseismic Nazca Ridge

    Science.gov (United States)

    Bishop, B.; Beck, S. L.; Zandt, G.; Wagner, L. S.; Long, M. D.; Tavera, H.

    2015-12-01

    The subduction of oceanic plateaus or aseismic ridges represent significant perturbations to the long term development of subduction systems and associated orogenies, the consequences of which are variable and determined by the physical characteristics of both the overriding and subducting plates. Flat subduction of the ~18 km oceanic crust of the aseismic Nazca Ridge under the 50 km to 65 km continental crust of the Peruvian Andes provides an opportunity to investigate these consequences. Through analysis of 2233 teleseismic P-wave receiver functions from 55 broadband seismometers deployed in southern Peru for the PULSE, CAUGHT and PeruSE seismic experiments we have identified the South American continental Moho and subducted Nazca oceanic Moho to a higher degree of detail than previously possible in the region.We find that the continental Moho beneath the Western and Eastern Cordilleras of the Peruvian Andes is at a depth >60 km to the north and south of the subducted Nazca Ridge but at 500 km from the trench.

  12. Resistivity distribution from mid-crustal conductor to near-surface across the 1200 km long Liquiñe-Ofqui Fault System, southern Chile

    Science.gov (United States)

    Held, Sebastian; Schill, Eva; Pavez, Maximiliano; Díaz, Daniel; Muñoz, Gerard; Morata, Diego; Kohl, Thomas

    2016-12-01

    Mid-crustal conductors are a common phenomenon in magnetotelluric studies. In the Andean Cordillera of southern Chile, they appear to concentrate along major fault zones. A high-resolution, broad-band magnetotelluric survey including 31 stations has been carried out along two profiles perpendicular to (1) the Liquiñe-Ofqui Fault Systems (LOFS) and (2) the Villarrica-Quetrupillán-Lanín volcanic lineament running parallel to the Mocha-Villarrica Fault Zone (MVFZ). The survey aimed at tracing one of the known conductors from mid-crustal depth to near-surface along these faults. Directionality and dimensionality were analysed using tensor decomposition. Phase tensors and induction arrows reveal two major geoelectric strike directions following the strike of LOFS and MVFZ. 2-D inversion shows low resistivity zones along both fault systems down to a depth of >10 km, where the brittle-ductile transition is expected. Along the LOFS, the two anomalies are linked to (1) Lake Caburgua, where the LOFS broadens to about 2 km of lateral extension and seems to represent a pull-apart structure, and (2) the intersection with the Villarrica-Quetrupillán-Lanín volcanic lineament, where seismic activity was observed during the latest eruption in March 2015. A connection of the mid-crustal conductor to the ESE-WNW-striking fault zones is indicated from the presented data.

  13. Constraining the Late Mesozoic and Early Tertiary Tectonic Evolution of Southern Mexico: Structure and Deformation History of the Tierra Caliente Region.

    Science.gov (United States)

    Cabral-Cano; Draper; Lang; Harrison

    2000-07-01

    We analyze the structure and assess the deformation history of the Tierra Caliente Metamorphic Complex (TCMC) of southern Mexico, where Laramide accretion of exotic terranes is in debate. The TCMC consists of a south-plunging antiform fault that is bounded on both its eastern and western flanks. Tierra Caliente Metamorphic Complex rocks show at least two phases of compressional deformation. The first and most prominent records a mean tectonic transport direction of 068 degrees. This phase is responsible for east-verging asymmetrical folding and thrusting of both metamorphic and superjacent sedimentary rocks. The second phase has an average transport direction of 232 degrees and is restricted to the western portion of the TCMC. A third phase is responsible for normal faulting. Lack of discernible deformation before Late Cretaceous time indicates that the main deformation phase is coincident with Laramide orogenesis elsewhere in the North American Cordillera. The stratigraphy, structure, and deformational history of the TCMC do not require accretion of exotic terranes. We explain the Mesozoic tectonostratigraphic evolution of the TCMC in terms of deposition and deformation of Mesozoic volcanic and sedimentary strata over the attenuated continental crust of the North American plate.

  14. Estratigrafía y facies volcánicas y volcaniclásticas de la Formación Valle del Cura: magmatismo paleógeno en la Cordillera Frontal de San Juan

    Directory of Open Access Journals (Sweden)

    V.D. Litvak

    2005-06-01

    Full Text Available En la región del Valle del Cura, Cordillera Frontal de San Juan, aflora una espesa secuencia de rocas volcánicas y volcaniclásticas, en facies piroclásticas y epiclásticas, que representa el desarrollo de un importante episodio volcano-sedimentario eoceno-oligoceno inferior. Esta unidad, la Formación Valle del Cura, incluye espesos paquetes de tobas, conglomerados gruesos, areniscas líticas medianas a gruesas, areniscas volcánicas y escasas pelitas. Los niveles volcánicos están formados por flujos lávicos e ignimbritas de alto grado de composiciones riolíticas, las cuales representan flujos piroclásticos de alta temperatura y alto grado de soldadura. La Formación Valle del Cura también incluye espesos niveles de flujos piroclásticos primarios formados por tobas cristalinas, líticas y/o vítreas, tobas lapillíticas e inclusive facies gruesas como aglomerados y brechas volcánicas. Vinculados a estos depósitos piroclásticos se interdigitan facies epiclásticas de composición dominante volcánica, que representan el retrabajo del material piroclástico primario. Los depósitos ignimbríticos muestran evidencias que indican su proximidad respecto al centro de emisión, el cual se encontraría en el extremo sur de la cordillera de la Brea. Esta secuencia se puede correlacionar con secuencias equivalentes que afloran hacia el norte en el río de la Sal y en las nacientes del río Blanco, en Macho Muerto, y cronológicamente, con los intrusivos mesosilíceos de la Unidad Bocatoma que afloran en territorio chileno -a la misma latitud- y que están emplazados a lo largo del frente magmático eoceno. En constraste, la Formación Valle del Cura representa una intensa actividad volcanodesimentaria sinorogénica depositada en una cuenca de retroarco.

  15. Geothermal resources of southern Idaho

    Science.gov (United States)

    Mabey, Don R.

    1983-01-01

    The geothermal resource of southern Idaho as assessed by the U.S. Geological Survey in 1978 is large. Most of the known hydrothermal systems in southern Idaho have calculated reservoir temperatures of less than 150?C. Water from many of these systems is valuable for direct heat applications, but is lower than the temperature of interest for commercial generation of electricity at the present time. Most of the known and inferred geothermal resources of southern Idaho underlie the Snake River Plain. However, major uncertainties exist concerning the geology and temperatures beneath the plain. By far the largest hydrothermal system in Idaho is in the Bruneau-Grand View area of the western Snake River Plain with a calculated reservoir temperature of 107?C and an energy of 4.5? 10 20 joules. No evidence of higher temperature water associated with this system has been found. Although the geology of the eastern Snake River Plain suggests that a large thermal anomaly may underlie this area of the plain, direct evidence of high temperatures has not been found. Large volumes of water at temperatures between 90? and 150?C probably exist along the margins of the Snake River Plain and in local areas north and south of the plain. Areas that appear particularly promising for the occurrence of large high-temperature hydrothermal systems are: the area north of the Snake River Plain and west of the Idaho batholith, the Island Park area, segments of the margins of the eastern Snake River Plain, and the Blackfoot lava field.

  16. Cystic echinococcosis in Southern Israel.

    Science.gov (United States)

    Ben-Shimol, Shalom; Sagi, Orli; Houri, Ohad; Bazarsky, Elina; Berkowitz, Anat; Bulkowstein, Shlomi; Barrett, Chiya; Greenberg, David

    2016-01-01

    The aim of this retrospective, population-based study was to characterize demographically and clinically cystic-echinococcosis (CE) in southern Israel, between 2005 and 2012. Newly-diagnosed (nd-CE) and past-diagnosed (pd-CE, diagnosed before the study) cases were defined. Two populations live in southern-Israel, receiving medical treatment at a single hospital: the Jewish and the Bedouin populations (resembling resource-rich and resource-poor populations, respectively). 126 CE cases were identified; 55 nd-CE and 71 pd-CE. Mean annual nd-CE incidence per 100,000 in the Bedouin and Jewish populations were 2.7 ± 1.2 and 0.4 ± 0.3, respectively (Pborn outside Israel. Liver and lung involvement were recorded in 85.7% and 15.1% of overall-CE, respectively. Abdominal pain, cough, fever, eosinophilia and asymptomatic disease were documented in 63.6%, 32.7%, 27.3%, 41.5% and 12.7% of nd-CE, respectively. Serology sensitivity for first test and any positive test were 67.3% and 83.3%, respectively. Computed tomography, ultrasonography and X-ray diagnosis were documented in 79.2%, 58.4% and 17.0% of overall-CE, respectively, with ultrasonography mainly used in liver-CE and X-ray in lung-CE. Treatment included surgery and albendazole in 50.0% and 55.3% of CE, respectively. We conclude that CE is endemic in southern-Israel among the Bedouin population, while disease is probably mainly imported in the Jewish population. Liver involvement and eosinophilia rates were high compared with those of other endemic regions, possibly due to differences in the timing of diagnosis. These findings may help developing treatment and prevention strategies.

  17. Efecto del Compost de Biosólidos en la producción de plantines de Austrocedrus Chilensis (ciprés de la cordillera Effect of Biosolids Compost on seedling production of Austrocedrus Chilensis (ciprés de la cordillera

    Directory of Open Access Journals (Sweden)

    Gustavo Basil

    2009-06-01

    Full Text Available La utilización de compost de residuos urbanos como sustrato en contenedores es una alternativa interesante a nivel económico y ambiental, dado que reduciría el uso de turba y «tierra negra» en la producción de plantines, y la disposición de residuos en vertederos. En el presente trabajo se estudió el efecto de 0, 30 y 50% de compost de biosólidos en el crecimiento inicial (primer año de ciprés de la cordillera, y el efecto durante los dos años siguientes de un tratamiento único con 50% de compost en el crecimiento posterior y el estado nutricional de los plantines. Se determinó diámetro y altura a 18, 25 y 37 meses, biomasa aérea y radicular a 25 y 37 meses, y concentración foliar de C, N, P, K, Ca y Mg a 37 meses. A pesar de que los tres tratamientos iniciales fueron homogeneizados al año en un único tratamiento con 50% de compost, se encontraron diferencias significativas de diámetro, altura y biomasa aérea y radicular entre los tratamientos originales en todas las fechas analizadas, correspondiendo los mayores valores a los tratamientos con compost. Al finalizar el ensayo, las concentraciones foliares de nutrientes fueron muy similares en todos los plantines, excepto Mg que fue mayor en el tratamiento original con 50% de compost. Los resultados muestran la importancia de los primeros meses de crecimiento en el desarrollo posterior de los plantines de ciprés y el valor potencial de los compost de biosólidos como sustrato para la producción de esta especie en contenedores.Using composts of urban waste, including biosolids, as substrates for containerized plant production is a sound economic and environmental alternative, since it could reduce the use of peat- and «black earth»-based media, and the disposal of organic wastes in landfills. The objectives of this work were to study the effect of 0, 30 and 50% biosolids compost on the initial growth (first year of cypress (Austrocedrus chilensis D. Don, and the effect

  18. Las sedimentitas que apoyan en no concordancia sobre el "granito rojo"en el angosto de la Quesera (Cordillera Oriental, Salta: una revisión crítica a más de 60 años de los trabajos pioneros de J. Keidel The sedimentary units unconformably overlying the red granite at Angosto de La Quesera (Cordillera Oriental, Salta and their stratigraphical interpretation: a critical revision more than 60 years after the pioneering work by J. Keidel

    Directory of Open Access Journals (Sweden)

    R.A. Astini

    2005-09-01

    Full Text Available A más de 60 años de la obra de J. Keidel se discute la edad y naturaleza de los depósitos paleozoicos apoyados sobre el "granito rojo" en el angosto de La Quesera, (Cordillera Oriental, provincia de Salta, perteneciente al batolito de Santa Rosa de Tastil. Trabajos recientes han puesto en duda las interpretaciones acerca de la discordancia descripta por dicho autor y reasignado parte de la estratigrafía al Grupo Mesón cámbrico. Este trabajo pretende aclarar las relaciones estratigráficas ratificando la naturaleza discordante de las unidades suprayacentes al granito y su edad ordovícica. Keidel (1943 no sólo describió con acierto la estratigrafía y las relaciones de yacencia en la zona sino que realizó observaciones puntuales que al día de hoy no pueden ser desestimadas. La estratigrafía aflorante en el angosto está constituida por las Formaciones Cardonal, Devendeus y Saladillo. Se discute el arreglo y el significado estratigráfico de las unidades expuestas en esta región y compara con unidades estratigráficas expuestas en las regiones vecinas, a los efectos de proponer un marco de correlación estratigráfico para el borde occidental de la Cordillera Oriental. Se descarta la existencia del Grupo Mesón y la suposición de magmatismo concomitante con su sedimentación. La situación particular de esta región hace que en una misma superficie se amalgamen los efectos de la orogenia tilcárica e irúyica y, además, se verifique una importante actividad de la fase diastrófica intra-ordovícica denominada fase tumbaya. La propuesta de un hiato de extensión reducida para la discordancia tilcárica es desestimada.After more than 60 years since the work by J. Keidel, the age and characteristics of the Paleozoic deposits that overlie the red granites of the Santa Rosa de Tastil pluton at Angosto de La Quesera (Cordillera Oriental, Salta province are discussed. Recent work has questioned the unconformity described by that author and

  19. The Southern Sky Redshift Survey

    Science.gov (United States)

    da Costa, L. Nicolaci; Willmer, C. N. A.; Pellegrini, P. S.; Chaves, O. L.; Rité, C.; Maia, M. A. G.; Geller, M. J.; Latham, D. W.; Kurtz, M. J.; Huchra, J. P.; Ramella, M.; Fairall, A. P.; Smith, C.; Lípari, S.

    1998-07-01

    We report redshifts, magnitudes, and morphological classifications for 5369 galaxies with m_B Complejo Astronomico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan; the European Southern Observatory, La Silla, Chile, partially under the bilateral ESO-Observatório Nacional agreement; Fred Lawrence Whipple Observatory; Laboratório Nacional de Astrofísica, Brazil; and the South African Astronomical Observatory.

  20. Rural migration in southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Mosser, D.; Soden, D.L.

    1993-08-01

    This study reviews the history of migration in two rural counties in Southern Nevada. It is part of a larger study about the impact of a proposed high-level nuclear waste repository on in- and out-migration patterns in the state. The historical record suggests a boom and bust economic cycle has predominated in the region for the past century creating conditions that should be taken into account by decision makers when ascertaining the long-term impacts of the proposed repository.

  1. Change in the pattern of crustal seismicity at the Southern Central Andes from a local seismic network

    Science.gov (United States)

    Nacif, Silvina; Lupari, Marianela; Triep, Enrique G.; Nacif, Andrés; Álvarez, Orlando; Folguera, Andrés; Gímenez, Mario

    2017-06-01

    Shallow seismicity in the Southern Central Andes is associated with interplate earthquakes due to the subduction of the Nazca plate beneath the South American plate and neotectonic activity, mainly located in the retro-arc region. However, this pattern changes drastically south of 34°S within the transition zone at the Southern Central Andes where crustal seismicity associated with mountain-building processes concentrates at the fore-arc and intra-arc region. In order to define more accurately this transition we used data from a high density-seismic network over the Chilean fore-arc and axial Andean sector ( 33-34.5°S). We obtained a constraint data set of 77 seismic events located mostly in the Principal Cordillera western flank in the first 10 km of the upper crust. This cluster implies an abrupt change in the pattern of seismicity at the Southern Central Andes with a set of structures in the fore-arc and intra-arc accommodating shortening. This change in the locus of crustal seismicity and particularly its location on the fore-arc and intra-arc south of 34°S is discussed on the light of different hypotheses among which changes in the precipitation pattern and erosion along the Andes were favored. Focalized erosion associated with direction of prevailing Pacific winds south of 34°S could determine subcritical conditions that could be adjusted by out-of-sequence deformation causing crustal earthquakes in the fore-arc region, becoming the retro-arc zone nearly fossilized from a deformational point of view. Additionally, trench sediments associated with this change in the precipitation pattern could also favor decoupling of the subduction zone inhibiting retro-arc seismicity, although it does not explain activation of fore-arc structures south of 34°S and their absence north of this latitude. Finally, inhomogeneous distribution of seismicity through the fore-arc zone south of 34°S is discussed on the light of variable elastic thicknesses.

  2. Southern Africa CTA Site Proposal

    CERN Document Server

    Krüger, P P

    2012-01-01

    Southern Africa has some of the world's best sites for air Cherenkov telescopes. South Africa has only one viable site, which is south of Sutherland and also close to the Southern African Large Telescope (SALT). This site has very good infrastructure and is easy to access, but only 47% of the night-time has a cloudless sky usable for observations. Namibia, which already hosts the H.E.S.S telescope, has a number of potential sites with much less cloud coverage. The H.E.S.S. site is one of the highest of these sites at 1840 m a.s.l. with about 64% of the night-time cloudless. It also has very low night sky background levels and is relatively close (about 100 km) to Windhoek. Moving further away from Windhoek to the south, the cloud coverage and artificial night sky brightness becomes even less, with the site at Kuibis (between Keetmanshoop and Luderitz) at 1640 m a.s.l. having clear night skies 73% of the time. Even though this site seems remote (being 660 km from Windhoek by road), it is close to the national ...

  3. Atmospheric chemistry over southern Africa

    Science.gov (United States)

    Gatebe, Charles K.; Levy, Robert C.; Thompson, Anne M.

    2012-03-01

    Changing Chemistry in a Changing Climate: Human and Natural Impacts Over Southern Africa (C4-SAR); Midrand, South Africa, 31 May to 3 June 2011 During the southern African dry season, regional haze from mixed industrial pollution, biomass burning aerosol and gases from domestic and grassland fires, and biogenic sources from plants and soils is worsened by a semipermanent atmospheric gyre over the subcontinent. These factors were a driver of several major international field campaigns in the 1990s and early 2000s and attracted many scientists to the region. Some researchers were interested in understanding fundamental processes governing chemistry of the atmosphere and interaction with climate change. Others found favorable conditions for evaluating satellite- derived measurements of atmospheric properties and a changing land surface. With that background in mind a workshop on atmospheric chemistry was held in South Africa. Sponsored by the International Commission on Atmospheric Chemistry and Global Pollution (ICACGP; http://www.icacgp.org/), the workshop received generous support from Eskom, the South African power utility; and the Climatology Research Group of the University of the Witwatersrand, Johannesburg, South Africa.

  4. Southern Living and Southern Voices: Models of Regional Magazine Success and Failure.

    Science.gov (United States)

    English, John W.

    This paper examines the phenomenon of magazine success and failure as demonstrated by two regional magazines, "Southern Living" and "Southern Voices." The former, a combination of articles about food, travel, sports, and other positive aspects of southern life, was quickly accepted by its readers and advertisers and began…

  5. Evolución tectono-magmática durante el Pérmico al Jurásico temprano en la Cordillera del Viento (37°05´S - 37°15´S): nuevas evidencias geológicas y geoquímicas del inicio de la cuenca Neuquina Tectono-magmatic evolution during the Permian to the Early Jurassic in the Cordillera del Viento (37°05´S - 37°15´S): new geological and geochemical evidences for the early stages of the Neuquén basin

    OpenAIRE

    E.J. Llambías; H. A. Leanza; O. Carbone

    2007-01-01

    El extremo sur de la cordillera del Viento está constituido en mayor parte por las secuencias volcánicas que conforman el basamento de la cuenca Neuquina. Las rocas más antiguas corresponden a sedimentitas de la Formación Huaraco del Grupo Andacollo de edad carbonífera superior. Después de haber sido plegadas por la fase orogénica San Rafael en el Pérmico Temprano, estas sedimentitas fueron intruidas por plutones pérmicos de granodiorita y monzogranito junto con diques y domos de riolita. Las...

  6. Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion

    Science.gov (United States)

    Schindlbeck, J. C.; Kutterolf, S.; Freundt, A.; Straub, S. M.; Vannucchi, P.; Alvarado, G. E.

    2016-11-01

    Pacific drill sites offshore Central America provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the Neogene. The temporal distribution of tephra layers established by tephrochonostratigraphy in Part 1 indicates a nearly continuous highly explosive eruption record for the Costa Rican and the Nicaraguan volcanic arc within the last 8 Myr. The widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large-magnitude explosive eruptions along the southern Central American Volcanic Arc (CAVA). We observe three pulses of enhanced explosive volcanism between 0 and 1 Ma at the Cordillera Central, between 1 and 2 Ma at the Guanacaste and at >3 Ma at the Western Nicaragua segments. Averaged over the long-term the minimum erupted magma flux (per unit arc length) is ˜0.017 g/ms. Tephra ages, constrained by Ar-Ar dating and by correlation with dated terrestrial tephras, yield time-variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion. The peak rate at >2.3 Ma near Osa particularly relates to initial Cocos Ridge subduction which began at 2.91 ± 0.23 Ma as inferred by the 1.5 Myr delayed appearance of the OIB geochemical signal in tephras from Barva volcano at 1.42 Ma. Subsequent tectonic re-arrangements probably involved crustal extension on the Guanacaste segment that favored the 2-1 Ma period of unusually massive rhyolite production.

  7. A new perspective of the climatological features of upper-level cut-off lows in the Southern Hemisphere

    Science.gov (United States)

    Pinheiro, Henri Rossi; Hodges, Kevin Ivan; Gan, Manoel Alonso; Ferreira, Nelson Jesuz

    2017-01-01

    This study presents a detailed view of the seasonal variability of upper-level cut-off lows (COLs) in the Southern Hemisphere. The COLs are identified and tracked using data from a 36-year period of the European Centre for Medium Range Weather Forecast reanalysis (ERA-Interim). The objective identification of the COLs uses a new approach, which is based on 300 hPa relative vorticity minima, and three restrictive criteria of the presence of a cold-core, stratospheric potential vorticity intrusion, and cut-off cyclonic circulation. The highest COL activity is in agreement with previous studies, located near three main continental areas (Australia, South America, and Africa), with maximum frequencies usually observed in the austral autumn. The COL mean intensity values show a marked seasonal and spatial variation, with maximum (minimum) values during the austral winter (summer), a unique feature that has not been observed previously in studies based on the geopotential. The link between intensity and lysis is examined, and finds that weaker systems are more susceptible to lysis in the vicinity of the Andes Cordillera, associated with the topographic Rossby wave. Lysis and genesis regions are close to each other, confirming that COLs are quasi-stationary systems. Also, COLs tend to move eastward and are faster over the higher latitudes. The mean growth/decay rates coincide with the major genesis and lysis density regions, such as the significant decay values across the Andes all year. As a consequence of using vorticity for the tracking method a longer lifetime of COLs is detected than in other studies, but this does not affect the total frequency of occurrence. Comparisons with other studies suggest that the differences in seasonality are due to uncertainties in the reanalyses and the methods used to identify COLs.

  8. Propuestas de prospección de bajo coste para la detección de campamentos romanos de campaña. El área occidental de la Cordillera Cantábrica como caso de estudio

    Directory of Open Access Journals (Sweden)

    MENÉNDEZ BLANCO, A., GONZÁLEZ ÁLVAREZ, D., ÁLVAREZ MARTÍNEZ, V. y JIMÉNEZ CHAPARRO, J.I.

    2013-01-01

    Full Text Available En este trabajo se expone y discute el método arqueológico experimentado para la localización y estudio de campamentos romanos de campaña situados en áreas de montaña. A partir de una propuesta de trabajo desarrollada en el área occidental de la Cordillera Cantábrica, valoramos las potencialidades de distintas técnicas para la detección de evidencias arqueológicas relacionadas con la conquista romana de este territorio. Por medio de herramientas diversas, como la documentación cartográfica y la fotografía aérea disponibles en libre acceso a través de internet, la atención a la toponimia o a las tradiciones orales del folklore, junto a la prospección convencional en superficie, se ha desarrollado con éxito un protocolo para la identificación de castra aestiva con unos costes reducidos que podría ser transferible a otros espacios montañosos.

  9. Ensayo de zonación sismotectónica en la Cordillera Ibérica. Depresión del Ebro y borde sur Pirenáico

    Directory of Open Access Journals (Sweden)

    Simon, J. L.

    1987-12-01

    Full Text Available Spatial relations between recent (Pliocene and Quaternary structures and seismic activity in the Iberian Chain, Ebro Basin and Outer Pyrenean Sierras are analysed. Starting from these relations, a seismotectonic zonation defining four main regions (Eastern Iberian Chain, Middle Iberian Chain, Outer Pyrenean Sierras-Carneros-Demanda Massif and Central sector of the Ebro Basin is stablished. Several zones and subzones with homogeneous characteristics from the seismotectonic point of view are differenciated within each of these four main regions. This zonation is the basis of an attempt to calculate seismic risk with a deterministic criterion.Se analizan las relaciones espaciales entre estructuras recientes (pliocenas y cuaternarias y actividad sísmica en el área de la Cordillera Ibérica, Depresión del Ebro y Sierras Exteriores Pirenaicas. A partir de ellas se realiza una zonación sismotectónica, definiendo cuatro regiones principales (Ibérica Oriental, Ibérica central, Sierras Exteriores-Macizo de Cameros-Demanda y sector central de la Depresión del Ebro y, en cada una de ellas, diferentes zonas y subzonas con características homogéneas desde el punto de vista sismotectónico. Esta zonación constituye la base de un ensayo de cálculo de riesgo sísmico con criterio determinista.

  10. A new catfish species of the genus Trichomycterus (Siluriformes: Trichomycteridae from the río Orinoco versant of Páramo de Cruz Verde, Eastern Cordillera of Colombia

    Directory of Open Access Journals (Sweden)

    Carlos DoNascimiento

    Full Text Available A new Trichomycterus is described from a highland tributary of the río Meta (Orinoco basin, along the east flank of Páramo de Cruz Verde, Eastern Cordillera of Colombia. The new species is distinguished from most of its congeners by having a reduced posterior cranial fontanel, restricted to the parieto-supraoccipital, cleithrum pierced by several foramina, and an unique combination of four irregular rows of conic teeth in premaxilla and dentary, 13-14 opercular odontodes, 41-43 interopercular odontodes, 6-7 branchiostegal rays, 40 or 41 free vertebrae, 14-18 ribs, first ray of pectoral fin slightly projected as a short filament, 7-8 branched pectoral-fin rays, dorsal-fin origin at same level of pelvic-fin insertion, anal-fin origin posterior to dorsal-fin base, caudal-fin margin slightly rounded, a single upper hypural plate (3+4+5, and coloration pattern consisting in ground color dark brown with a thin mid-lateral dark stripe. Phylogenetic relationships of the new species based on the shared presence of derived features related to posterior cranial fontanel and cleithrum are discussed. The new species is also compared to the only two described species from Andean tributaries of río Orinoco basin.

  11. Fajas oblicuas de deformación neotectónica en Precordillera y Cordillera Frontal (31° 30´ - 33° 30´ LS: controles paleotectónicos

    Directory of Open Access Journals (Sweden)

    J.M. Cortés

    2006-12-01

    Full Text Available La Precordillera Sur y las Cerrilladas Pedemontanas de Mendoza, son dos unidades morfotectónicas principales en la vertiente oriental de los Andes centrales, a los 31º30' - 33º30' de latitud sur. Allí, dos cinturones de deformación transpresiva y orientación noroeste, denominados fajas Barreal-Las Peñas y Río Mendoza-Tupungato, se desarrollaron como consecuencia de la gradual somerización de la placa de Nazca en los últimos 20 Ma. Su orientación y compleja geometría estructural resulta de la interferencia de la deformación andina tardío-cenozoica con la estructura de orientación noroeste del rift triásico de la cuenca Cuyana y antiguas zonas de sutura colisional de edad paleozoica. Este trabajo demuestra que los rasgos paleotectónicos del substrato triásico-paleozoico de la Precordillera Sur y del margen oriental de la Cordillera Frontal controlan la configuración morfotectónica y la distribución y reactivación de gran parte de la estructura neotectónica del margen andino a estas latitudes.

  12. Petroglifos en rocas de la Cordillera de la Costa así como en los raudales de los ríos de la selva virgen venezolana. La interpretación por Alejandro de Humboldt y observaciones actuales

    Directory of Open Access Journals (Sweden)

    Ursula Thiemer-Sachse

    2003-04-01

    Full Text Available Article in Spanish, Abstracts in English, German and Spanish.Indian Petroglyphs on rocks of the Venezuelan Cordilleras mountain chain as well as Región de los Raudales, the tropical forest headwaters. A. v. Humboldt’s petroglyph interpretations and present observations. Throughout the world the interpretation of petroglyphs and other prehistoric rock art is a difficult endeavor. Some of the factors contributing to these puzzles include, among others: a lack of knowledge about the circumstances (such as rituals and the concomitant ideas that played key roles in the creation of the petroglyphs. Even the famous nineteenth-century German explorer Alexander von Humboldt, who first saw South American petrogpyphs while mapping the river system connecting the Amazon and Orinoco rivers in Venezuela, ventured to decipher and analyze the complicated artwork as part of his interest in ancient civilizations. Since the time of Humboldt numerous other researchers have attempted to decode and provide a culturally-situated analysis of petroglyph’s meanings.

  13. El Transporte Terrestre a través de la Cordillera Cantábrica en Tiempos de Felipe II. Un Estudio a partir de la Correspondencia de Simón Ruiz con Laredo

    Directory of Open Access Journals (Sweden)

    Oscar LUCAS VILLANUEVA

    2012-12-01

    Full Text Available El presente trabajo analiza las condiciones y costes del transporte terrestre en tiempos de Felipe II en el ámbito de las relaciones comerciales entre Castilla y el espacio atlántico septentrional, a partir de la información proporcionada por las cartas comerciales del mercader Simón Ruiz. Los datos nos indican que las dificultades geográficas no fueron tan determinantes para el tráfico a través de la Cordillera Cantábrica como se había pensado hasta ahora. El artículo también aborda la cuestión de los costes que comportaban las operaciones de traslado de mercancías desde los puertos a los mercados del interior peninsular. Las fuentes nos permiten un detallado análisis de los mismos así como un cálculo de su cuantía en proporción a la suma total de la operación, relativizando la importancia de los mismos, lo que favorecería los traslados de mercancías por vía terrestre para distancias relativamente grandes.

  14. Características de la fauna de braquiópodos del Toarciense superior en el Sector Central de la Cordillera Ibérica (noroeste de España

    Directory of Open Access Journals (Sweden)

    García Joral, F.

    1984-04-01

    Full Text Available Studying brachiopod faunas from the Upper Toarcian beds of the Iberian Range (Central Sector, bring out the few number of species and the local range for the majority of them. In relation with that, populations show characteristics (polymorphism, gregarism and generalism that suggest an unstable environment, probably produced by the progressive isolation of the basin, the shallowing trend and the tectosedimentary instability quoted by differents authors, As a consequence of this situation there is a faunistic turnover for the brachiopods at this time, that could be the origin of some lineages developped in the Western European Dogger.

    En el estudio de la fauna de braquiópodos del Toarciense superior del Sector Central de la Cordillera Ibérica destacan el bajo. número de especies que la componen y el ámbito local de la mayoría de ellas. En relación con esto, las poblaciones muestran unas características (polimorfismo, gregarismo y forma generalizada que sugieren un ambiente inestable, provocado probablemente por el aislamiento progresivo de la cuenca, la tendencia somerizadora y la inestabilidad tectosedimentaria que han señalado diversos autores. La consecuencia de esta situación es una renovación faunística para el grupo en esta edad, que puede haber dado origen a algunas de las ramas filéticas que se desarrollan en el Dogger de Europa Occidental.

  15. New Moho map of southern Norway

    DEFF Research Database (Denmark)

    Stratford, Wanda Rose; Thybo, Hans; Faleide, J.-I.

    2009-01-01

    A recent seismic refraction study across southern Norway has revealed that the up to 2469 m high Southern Scandes Mountains are not isostatically compensated by a thick crust. Rather, the Moho depths are close to average for continental crust with elevations of ~1 km. Evidence from new seismic data...

  16. The Southern Alberta Information Resources (SAIR Project

    Directory of Open Access Journals (Sweden)

    Kathy Crewdson

    2008-06-01

    Full Text Available The Southern Alberta Information Resources (SAIR Project is a collaborative online bibliography of published resources significant to southern Alberta. This paper introduces the partners, briefly summarizes the purpose of the project, describes the progress and challenges encountered thus far, and discusses the intended project outcomes and impacts.

  17. Southern Forest Resource Assessment - Summary of Findings

    Science.gov (United States)

    David N. Wear; John G. Greis

    2002-01-01

    The Southern Forest Resource Assessment (SFRA) was initiated in spring 1999 to address broad questions concerning the status, trends, and likely future of southern forests. A descriptive assessment such as SFRA can be used to highlight the major dynamics and uncertainties at play within a region's forested ecosystems, thereby focusing public discourse. Because...

  18. [Japanese encephalitis in Southern Europe].

    Science.gov (United States)

    Cleton, Natalie; Koopmans, Marion; Braks, Marieta; Van Maanen, Kees; Reusken, Chantal

    2014-07-01

    In 2012, a fragment of the Japanese encephalitis virus (JEV) genome was isolated from a pool of Culex pipiens mosquitoes caught in 2010 and 2011 in Northern Italy. JEV has a broad geographical distribution in South and Southeast Asia and Oceania, and is the most important cause of viral encephalitis in Asia in humans and also causes encephalitis in horses and fertility problems in pigs. However, recently isolated JEV genome fragments in mosquitoes in Italy could be an indication of repeated introduction of JEV, enzootic circulation of JEV or a related virus in Southern Europe. Until more information is available, Japanese encephalitis remains a travel-related infectious disease for travellers to JEV endemic and epidemic areas outside of Europe.

  19. Discussing epigenetics in Southern California

    Science.gov (United States)

    2012-01-01

    With the goal of discussing how epigenetic control and chromatin remodeling contribute to the various processes that lead to cellular plasticity and disease, this symposium marks the collaboration between the Institut National de la Santé et de la Recherche Médicale (INSERM) in France and the University of California, Irvine (UCI). Organized by Paolo Sassone-Corsi (UCI) and held at the Beckman Center of the National Academy of Sciences at the UCI campus December 15–16, 2011, this was the first of a series of international conferences on epigenetics dedicated to the scientific community in Southern California. The meeting also served as the official kick off for the newly formed Center for Epigenetics and Metabolism at the School of Medicine, UCI (http://cem.igb.uci.edu). PMID:22414797

  20. Coccidioidomycosis in southern sea otters

    Science.gov (United States)

    Thomas, Nancy J.; Pappagianis, Demosthenes; Creekmore, Lynn H.; Duncan, Ruth M.

    1994-01-01

    Disseminated coccidioidomycosis was diagnosed postmortem in six southern sea otters (Enhydra lutris nereis) found dying or dead along the Pacific Coast of California at San Luis Obispo County.  These otters were found during winter or summer 1992, 1993, and 1994.  Coccidioides immitis was identified by its morphology in tissue impression smears and by histopathology, and was confirmed by culture.  Positive serologic results were obtained from four of five sea otters tested.  The lungs, pleura, tracheobronchial lymph nodes, liver, and spleen were involved in each case.  There was meningeal involvement in half of the affected animals.  Coccidioidomycosis has been reported in a wild sea otter only once previously, in 1976, and that otter was also found on the coast of San Luis Obispo County.

  1. Southern Energy Efficiency Center (SEEC)

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Robin; Sonne, Jeffrey; Withers, Charles; Cummings, James; Verdict, Malcolm; Roberts, Sydney

    2009-09-30

    The Southern Energy Efficiency Center (SEEC) builds collaborative partnerships with: state and local governments and their program support offices, the building delivery industry (designers, contractors, realtors and commissioning agents), product manufacturers and their supply chains, utilities and their program implementers, consumers and other stakeholders in order to forge a strong regional network of building energy efficiency allies. Through a project Steering Committee composed of the state energy offices and building industry stakeholders, the SEEC works to establish consensus-based goals, priorities and strategies at the regional, state and local levels that will materially advance the deployment of high-performance “beyond code” buildings. In its first Phase, SEEC will provide limited technical and policy support assistance, training, certification and education to a wide spectrum of the building construction, codes and standards, and the consumer marketplace.

  2. Ciclos tectónicos, volcánicos y sedimentarios del Cenozoico del sur de Mendoza-Argentina (35°-37°S y 69°30'W Cenozoic tectonic, volcanic and sedimentary cycles in southern Mendoza Province, Argentina (35°-37°S y 69°30'W

    Directory of Open Access Journals (Sweden)

    Ana María Combina

    2011-01-01

    Full Text Available En este trabajo se describe la estratigrafía sedimentaria y volcánica asociada a los procesos de deformación de las unidades con edades del Cretácico Tardío al Plioceno Tardío aflorantes en el sur de Mendoza, Argentina, entre los ríos Atuel y Barrancas en el ámbito de la Cordillera Principal. Se proponen tres ciclos tectovolcano-sedimentarios, limitados por discordancias regionales generadas por la acción de las Fases Incaica, Quechua, Pehuenche y Diaguita. El primer ciclo comprende las unidades volcánicas y sedimentarias del Cretácico Superior hasta el Oligoceno Superior (Formaciones Roca y Pircala-Coihueco y el Ciclo Eruptivo Molle. El segundo abarca desde el Oligoceno Tardío al Mioceno Tardío (Formación Agua de la Piedra y las Andesitas Huincán. Por último, el tercer ciclo comprende desde el Mioceno Tardío al Plioceno (Formaciones Butaló, Pincheiras, Loma Fiera, Río Diamante y las Andesitas La Brea.This article describes the volcanic and sedimentary stratigraphy and their associated proces-ses with the Andean deformation during the Late Cretaceous to Late Pliocene. The studied área is located between the Atuel and Barrancas rivers and the Main Cordillera, in southern Mendoza, Argentina. Three tectovolcano-sedimentary cycles limited by regional discordances (Inca, Quechua, Pehuenche and Diaguita are proposed. The first comprises Upper Oligocene to Upper Miocene volcanic and sedimentary units (Roca and Pircala-Coihueco formations and the Volcanic Cycle Molle. The second extends from the Late Oligocene to Late Miocene (Agua de la Piedra Formation and the Huincán Andesites volcanic cycle. Finally, the third cycle ranges from the Late Miocene to Pliocene (Butaló, Pincheiras, Loma Fiera and Rio Diamante formations and La Brea Andesites.

  3. The severe zonda wind event of 11 July 2006 east of the Andes Cordillera (Argentine): a case study using the BRAMS model

    Science.gov (United States)

    Norte, Federico Augusto; Ulke, Ana Graciela; Simonelli, Silvia Carmen; Viale, Maximiliano

    2008-11-01

    The zonda is a wind that exhibits the so-called foehn effect: a warm, dry, strong wind related to adiabatic compression upon descending in the lee of the Andes. This phenomenon occurs mostly in winter and spring over the entire length of the extratropical Andes. It is frequently detected near the cities of Mendoza and San Juan, the most important urban regions of western Argentina. The aim of this work is to understand why a zonda wind event, occurring on 11 July 2006, reached and maintained the higher category Z4 during several hours. A secondary aim is to evaluate the ability of a Brazilian regional atmospheric modeling system (BRAMS) model to represent the features of this extreme episode and to explore if it can be used to predict a zonda event. The difference found with respect to other severe zonda wind episodes analyzed was that the wind registered the highest category (Z4) with extreme gusts during a long period. This condition was registered in particular on southern plain areas of San Juan province. The phenomenon had a great impact on the community, with residences and buildings being affected or destroyed, trees being felled, power supply and communications being shutdown, and several rural and urban fires being reported. The event was characterized through surface and upper-level information and model results. The synoptic surface and upper-air conditions were those typically associated with a severe zonda wind occurrence: a surface cold front approaching the region, driven by a 500 hPa trough, a strong upper-air jet stream, and a deep low-pressure surface system at higher latitudes over the Atlantic Ocean. The North West Argentine Low in central west Argentina during the following hours could be observed centered approximately at 31°S 66°W. in a few lower latitude than the location observed by National Center of Environmental Prediction (NCEP) reanalysis. On the other hand, it is the authors’ impression that the BRAMS model achieved an acceptable

  4. Attempts of whole-rock K/Ar dating of mesozoic volcanic and hypabissal igneous rocks from the Central Subbetic (Southern Spain: A case of differential Argon loss related to very low-grade metamorphism

    Directory of Open Access Journals (Sweden)

    Sanz de Galdeano, C.

    1988-04-01

    Full Text Available 12 samples of basic intrusives within Triassic rocks «ophites» and 11 samples of volcanic and associated intrusives within Jurassic to Early Cretaceous sequences of the Subbetic Zone were subjected to whole-rock K/Ar dating in combination with chemical/petrological analysis. Satisfactory results were obtained only from a number of samples of volcanic rocks, however, analytical ages commonly agree, within about 10 relative percent, with those deduced from stratigraphic location. «Ophite» samples, on the other hand, may reveal considerably lower analytic ages than the volcanics and show much stronger scattering, even among samples collected within a small area. It is argued that the inferred loss of Ar results from very-low-grade alpine metamorphic alteration, which affected the «ophites» more intensely than the higher volcanic rocks. Other post-emplacement chemical changes, such as the degree of secondary oxidation of Fe, are also distintive among the two groups of samples, and are to some extent consistent with the above view in that the alteration environment of the ophites should have produced conditions for more penetrative fluid-rock interactions and homogeneous recrystallization. Overall, the magmatic activity from which the ophitic rocks originated might have started in the Late Triassic and continued in the Lower Jurassic. 80th, the «ophites» and the volcanics are though to be the result of magmatic events Collowing tensional to transtensive crustal movements affecting the external basins of the Betic Cordilleras Crom Late Triassic to Early Cretaceous times.Doce muestras de cuerpos básicos intrusivos en rocas triásicas («ofitas» y 11 muestras de volcanitas y rocas intrusivas asociadas en secuencias jurásico-cretáceas de la zona Subbética han sido objeto de datación radiométrica K/Ar (roca total en combinación con análisis químico-petrográfico. Las edades analíticas obtenidas son 's

  5. The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

    Science.gov (United States)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Litvak, Vanesa D.; Poma, Stella; Alonso, Ricardo N.; Hinton, Richard

    2016-10-01

    The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29-31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U-Pb dating of magmatic zircon, combined with Ar-Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous (~ 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene (~ 26 Ma) to Early Miocene (~ 17 Ma), and Late Miocene (~ 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian-Triassic (P

  6. Paleontologia y ambientes del Triásico Medio en el sector noroccidental de la Cordillera Ibérica (provs. de Soria y Guadalajara, España

    Directory of Open Access Journals (Sweden)

    García-Gil, S.

    1991-04-01

    Full Text Available The Triassic of the NW Iberian Ranges consists of two carbonatic formations equivalent to the Upper Carbonatic Formation of the Muschelkalk Facies and pass laterally into siliciciastic deposits to the NW. Fossillocalities have been found in both formations. Taphonomic and sedimentologic studies allow for the interpretation as autochthonous associations of the infaunal Bivalves of shallow water marine environments with siliciciastic input. Three faunal associations have been distinguished: 1. Costatoria-Lyriomyophoria association, found in the lower carbonatic formation and the equivalent siliciciastic formation; 2. «Teruel Fauna» association, found in the upper carbonatic formation; 3. Lingula-Pseudocorbula association, found near the top of the upper carbonatic Formation. The «Teruel Fauna» is well represented in the Iberian Ranges, and always occur in the «Royuela Marls and Limestones» Formation, and our fossil localities are its most Northwestern record in the Iberian Ranges up to now, thus extending the presence of the endemic «Sephardic Faunas» during the Ladinian.El Triásico Medio del sector noroccidental de la Cordillera Ibérica está compuesto por dos formaciones carbonáticas, que se corresponden con la unidad carbonática superior del Muschelkalk, y que hacia el NW pasan lateralmente a una formación terrígena. El registro fósil se encuentra en ambos tipos de formaciones. Tanto el estudio tafonómico como sedimentológico, permiten inferir la presencia de elementos acumulados que podrían corresponder a asociaciones autóctonas, compuestas en su mayoría por bivalvos infaunales de medios marinos someros y sometidos a fuerte influencia de terrígenos. Se caracterizan en la zona tres asociaciones faunísticas: 1. Asociación CostatoriaLyriomyophoria, que aparece tanto en la formación carbonática inferior como en la formación terrígena equivalente; 2. Asociación «Fauna de Terue!», que aparece en la

  7. Interpretación paleoambiental de los depósitos de la Formación Saldeño (Cretácico superior, en la alta Cordillera de Mendoza, Argentina

    Directory of Open Access Journals (Sweden)

    MA Tunik

    2003-09-01

    Full Text Available La Formación Saldeño aflora en la Alta Cordillera de Mendoza, en una franja de continuidad meridianal, desde las estribaciones del Mesón de San Juan (33° 33´ LS hasta el área de la Laguna del Diamante (34° 06´ LS. Esta unidad está compuesta por 250 metros de pelitas, areniscas, conglomerados y calizas y puede ser dividida en tres secciones. La sección inferior está integrada por conglomerados, sabulitas y areniscas que fueron depositadas en un ambiente de abanicos aluviales. Las otras dos secciones, están integradas por pelitas, areniscas y rocas calcáreas y reflejan el desarrollo de una planicie carbonática fangosa que es reemplazada por una planicie de marea con características restringidas. La sección conglomerádica basal carece de relación genética con las otras dos y serían depósitos de borde de cuenca residuales, mientras que las secciones media y superior corresponden a depósitos relacionados con la ingresión marina maastrichtiana que alcanzó la región cordillerana proveniente desde el sudeste. En la sección marina se han identificado ciclos somerizantes y se hallaron por primera vez fósiles marinos en esta unidad. La edad de la misma es maastrichtiana obtenida a partir del hallazgo de nanofósiles calcáreos y palinoflora.

  8. Nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal: el caso de los pequeños propietarios forestales de la Cordillera de Nahuelbuta (Chile

    Directory of Open Access Journals (Sweden)

    Sergio Monrroy-Concha

    2013-06-01

    Full Text Available Se evaluó el nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal que poseen los pequeños propietarios forestales en dos territorios de la Cordillera de Nahuelbuta, en Chile. Para ello, se aplicó una encuesta a 53 personas (10% de las viviendas, que abordó cinco temas centrales: (1 uso del bosque nativo, (2 participación en redes sociales y acceso a la información, (3 conocimiento general de la Ley, (4 conocimiento respecto a la administración y (5 fomento de la Ley. Los resultados mostraron que: (1 el bosque nativo es usado para obtener productos madereros y no madereros, (2 las redes sociales y especialmente la radio son fundamentales para la transferencia de información, (3 tanto el conocimiento general de la Ley como (4 el nivel de conocimiento respecto de la administración de la Ley es insuficiente, y (5 se desconocen los trámites que deben efectuarse para obtener los beneficios de la Ley. Se concluye que: (1 el nivel de conocimiento de la Ley es insuficiente, (2 es fundamental estimular el uso de los instrumentos de esta Ley en la totalidad del territorio, de modo de garantizar el uso sustentable del recurso, y (3 la difusión de los beneficios de la Ley debe considerar las formas de comunicación tradicionales, el nivel de educación y la cultura de los espacios rurales

  9. Southern company energy storage study :

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, James; Bhatnagar, Dhruv; Black, Clifton; Jenkins, Kip

    2013-03-01

    This study evaluates the business case for additional bulk electric energy storage in the Southern Company service territory for the year 2020. The model was used to examine how system operations are likely to change as additional storage is added. The storage resources were allowed to provide energy time shift, regulation reserve, and spinning reserve services. Several storage facilities, including pumped hydroelectric systems, flywheels, and bulk-scale batteries, were considered. These scenarios were tested against a range of sensitivities: three different natural gas price assumptions, a 15% decrease in coal-fired generation capacity, and a high renewable penetration (10% of total generation from wind energy). Only in the elevated natural gas price sensitivities did some of the additional bulk-scale storage projects appear justifiable on the basis of projected production cost savings. Enabling existing peak shaving hydroelectric plants to provide regulation and spinning reserve, however, is likely to provide savings that justify the project cost even at anticipated natural gas price levels. Transmission and distribution applications of storage were not examined in this study. Allowing new storage facilities to serve both bulk grid and transmission/distribution-level needs may provide for increased benefit streams, and thus make a stronger business case for additional storage.

  10. Nearshore marine fish assemblages in southern California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fish benthic trawls were completed by the Southern California Coastal Water Research Project (SCCWRP). Data from 425 fisheries independent trawls ranging from 2-215...

  11. Waterfowl production survey: Southern Alberta: July 1989

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Production and Habitat Survey for southern Alberta during 1989. The primary purpose of the survey is to provide information on...

  12. Waterfowl production survey: July 1997: Southern Manitoba

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Production and Habitat Survey for southern Manitoba during 1997. The primary purpose of the survey is to provide information on...

  13. Southern Watersheds Common Reedgrass Monitoring Plan

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Southern Watersheds Common Reedgrass Project is an interagency effort to increase public awareness of the common reedgrass problem, demonstrate effective control...

  14. Southern Great Plains Atmospheric Radiation Measurement Site

    Data.gov (United States)

    Federal Laboratory Consortium — The Southern Great Plains Atmospheric Radiation Measurement Site (SGP-ARM) is the oldest and largest of DOE's Arm sites. It was established in 1992. It consists of...

  15. Experimental late brood surveys: Southern Saskatchewan: 1991

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the late brood surveys for southern Saskatchewan during 1991. Survey methods, weather and habitat conditions, production indices, and tables...

  16. South African southern ocean research programme

    CSIR Research Space (South Africa)

    SASCAR

    1987-01-01

    Full Text Available This document describes the South African National Antarctic Research Programme's (SANARP) physical, chemical and biological Southern Ocean research programme. The programme has three main components: ecological studies of the Prince Edward Islands...

  17. Waterfowl breeding population survey: Southern Saskatchewan: 2000

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Breeding Population and Habitat Survey for southern Saskatchewan during 2000. The primary purpose of the survey is to provide...

  18. Southern Watersheds Common Reedgrass Project Progress Report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Southern Watersheds includes the drainages of the Northwest River, the North Landing River, and Back Bay in the southeastern corner of Virginia. Common reedgrass...

  19. Southern Hemisphere Ice Limits, 1973-1978

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Weekly Southern Ocean ice limits, have been digitized from U.S. Navy Fleet Weather Facility ice charts, at the Max-Planck Institut fur Meteorologie, Hamburg....

  20. Waterfowl production survey: Southern Alberta: 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Production and Habitat Survey for southern Alberta during 1981. The primary purpose of the survey is to provide information on...

  1. Waterfowl breeding pair survey: Southern Alberta: 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Breeding Population and Habitat Survey for southern Alberta during 1981. The primary purpose of the survey is to provide...

  2. Waterfowl breeding population survey: Southern Manitoba: 1983

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Breeding Population and Habitat Survey for southern Manitoba during 1983. The primary purpose of the survey is to provide...

  3. Marine Invertebrate assemblages in southern California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a point file of invertebrate site clusters calculated from benthic trawls completed by the Southern California Coastal Water Research Project (SCCWRP). Data...

  4. Fish assemblages in southern California kelp forests.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a point file of fish assemblages calculated from diver surveys in kelp forests in Southern California. Visual census data was combined for two separate...

  5. Training traditional birth attendants in southern Sudan.

    Science.gov (United States)

    Haarsager, Mary

    2008-01-01

    Traditional birth attendants are currently the principal service providers to pregnant women in southern Sudan. A training program provides education to promote maternal and newborn health as well as birth preparedness and establishes mechanisms for supportive supervision.

  6. Waterfowl production survey: Southern Alberta: 1979

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Production and Habitat Survey for southern Alberta during 1979. The primary purpose of the survey is to provide information on...

  7. Waterfowl production survey for southern Manitoba: 1991

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Production and Habitat Survey for southern Manitoba during 1991. The primary purpose of the survey is to provide information on...

  8. Waterfowl breeding population survey: Southern Saskatchewan: 1983

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the Waterfowl Breeding Population and Habitat Survey for southern Saskatchewan during 1983. The primary purpose of the survey is to provide...

  9. Climate Prediction Center Southern Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and Sea Surface Temperature (SST)Indices. It contains Southern Oscillation Index which is standardized sea level...

  10. Census summary of southern sea otter 2016

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The GIS shapefile "Census summary of southern sea otter 2016" provides a standardized tool for examining spatial patterns in abundance and demographic trends of the...

  11. Southern Ocean - South African cooperative research programme.

    CSIR Research Space (South Africa)

    SANCOR

    1979-05-01

    Full Text Available South African research in the Southern Ocean has already produced some important and illuminating results. Most of these efforts, however, were of an individual and uncoordinated nature. Due to increasing interest in the ocean- in South Africa...

  12. Arctic and Southern Ocean Sea Ice Concentrations

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly sea ice concentration for Arctic (1901 to 1995) and Southern oceans (1973 to 1990) were digitized on a standard 1-degree grid (cylindrical projection) to...

  13. Star forming regions of the southern galaxy

    Science.gov (United States)

    Kuiper, T. B. H.; Er, J. W., the molecular gas, a

    1987-01-01

    A catalog of southern dust cloud properties is being compiled to aid in the planning and analysis of radio spectral line surveys in the southern hemisphere. Ultimately, images of dust temperature and column density will be produced. For the interim, a list of the 60 and 100 micron fluxes was prepared for the cores and adjacent backgrounds of 65 prominent dust clouds. Dust temperatures and column densities were derived.

  14. 77 FR 17122 - Indiana Southern Railroad, LLC-Temporary Trackage Rights Exemption-Norfolk Southern Railway Company

    Science.gov (United States)

    2012-03-23

    ... Surface Transportation Board Indiana Southern Railroad, LLC--Temporary Trackage Rights Exemption--Norfolk Southern Railway Company Norfolk Southern Railway Company (NSR), pursuant to a written trackage rights agreement (Agreement), has agreed to grant overhead temporary trackage rights to Indiana Southern Railroad...

  15. La Peligrosa caldera (47° 15‧S, 71° 40‧W): A key event during the Jurassic ignimbrite flare-up in Southern Patagonia, Argentina

    Science.gov (United States)

    Sruoga, P.; Japas, M. S.; Salani, F. M.; Kleiman, L. E.

    2014-01-01

    Pyroclastic and lava vent-facies, from the Late Jurassic El Quemado Complex, are described at the southern Lake Ghío, in the Cordillera Patagónica Austral. Based on the comprehensive study of lithology and structures, the reconstruction of the volcanic architecture has been carried out. Four ignimbrites and one rhyolitic lava unit, affected by oblique-slip normal faults have been recognized. The evolution of La Peligrosa Caldera has been modeled in three different stages:1) initial collapse, consisting of a precursory downsag subsidence, related to a dilatational zone, which controlled the location of the caldera, 2) main collapse, with the emplacement of large volume crystal-rich ignimbrites and megabreccias, under a progressive subsidence controlled by a pull-apart structure related to a transtensional regime and 3) post-collapse, in which lava flows and associated domes were emplaced under an oblique-extensional regime. The caldera records a remarkable change from transtension to oblique extension, which may represent an important variation in regional deformation conditions during Jurassic times. La Peligrosa Caldera may be considered a key event to understand the eruptive mechanisms of the flare-up volcanism in the Chon Aike Silicic Province.

  16. The Southern Ocean: Source and sink?

    Science.gov (United States)

    Strugnell, J. M.; Cherel, Y.; Cooke, I. R.; Gleadall, I. G.; Hochberg, F. G.; Ibáñez, C. M.; Jorgensen, E.; Laptikhovsky, V. V.; Linse, K.; Norman, M.; Vecchione, M.; Voight, J. R.; Allcock, A. L.

    2011-03-01

    Many members of the benthic fauna of the Antarctic continental shelf share close phylogenetic relationships to the deep-sea fauna adjacent to Antarctica and in other ocean basins. It has been suggested that connections between the Southern Ocean and the deep sea have been facilitated by the presence of a deep Antarctic continental shelf coupled with submerging Antarctic bottom water and emerging circumpolar deep water. These conditions may have allowed 'polar submergence', whereby shallow Southern Ocean fauna have colonised the deep sea and 'polar emergence', whereby deep-sea fauna colonised the shallow Southern Ocean. A recent molecular study showed that a lineage of deep-sea and Southern Ocean octopuses with a uniserial sucker arrangement on their arms appear to have arisen via polar submergence. A distantly related clade of octopuses with a biserial sucker arrangement on their arms (historically placed in the genus Benthoctopus) is also present in the deep-sea basins of the world and the Southern Ocean. To date their evolutionary history has not been examined. The present study investigated the origins of this group using 3133 base pairs (bp) of nucleotide data from five mitochondrial genes (12S rRNA, 16S rRNA, cytochrome c oxidase subunit I, cytochrome c oxidase subunit III, cytochrome b) and the nuclear gene rhodopsin from at least 18 species (and 7 outgroup taxa). Bayesian relaxed clock analyses showed that Benthoctopus species with a high-latitude distribution in the Southern Hemisphere represent a paraphyletic group comprised of three independent clades. The results suggest that the Benthoctopus clade originated in relatively shallow Northern Hemisphere waters. Benthoctopus species distributed in the Southern Ocean are representative of polar emergence and occur at shallower depths than non-polar Benthoctopus species.

  17. Extensional deformation of the Guadalquivir Basin: rate of WSW-ward tectonic displacement from Upper Tortonian sedimentary rocks

    Science.gov (United States)

    Roldán, Francisco J.; Azañón, Jose Miguel; Rodríguez-Fernández, Jose; María Mateos, Rosa

    2016-04-01

    The Guadalquivir Basin (Upper Tortonian-Quaternary sedimentary infilling) has been considered the foreland basin of the Betic Orogen built up during its collision with the Sudiberian margin. The basin is currently restricted to its westernmost sector, in the Cadiz Gulf, because the Neogene-Quaternary uplift of the Betic Cordillera has produced the emersion of their central and eastern parts. The upper Tortonian chronostratigraphic unit is the oldest one and it was indistinctly deposited on the South Iberian paleomargin and the External units from the Betic Cordillera. However, these rocks are undeformed on the Sudiberian paleomargin while they are deeply affected by brittle deformation on the External Betic Zone. Outcrops of Upper Tortonian sedimentary rocks on External Betic Zone are severely fragmented showing allocthonous characters with regard to those located on the Sudiberian paleomargin. This post- Upper Tortonian deformation is not well known in the External Zones of the Cordillera where the most prominent feature is the ubiquity of a highly deformed tecto-sedimentary unit outcropping at the basement of the Guadalquivir sedimentary infilling. This tecto-sedimentary unit belongs to the Mass Wasting Extensional Complex (Rodríguez-Fernández, 2014) formed during the collision and westward migration of the Internal Zone of the Betic Cordillera (15-8,5 Ma). In the present work, we show an ensemble of tectonic, geophysical and cartographic data in order to characterize the post-Upper Tortonian deformation. For this, seismic reflection profiles have been interpreted with the help of hidrocarbon boreholes to define the thickness of the Upper Tortonian sedimentary sequence. All these data provide an estimation of the geometrical and kinematic characteristics of the extensional faults, direction of movement and rate of displacement of these rocks during Messinian/Pliocene times. References Rodríguez-Fernández, J., Roldan, F. J., J.M. Azañón y Garcia-Cortes, A

  18. Emigration dynamics in southern Africa.

    Science.gov (United States)

    Milazi, D

    1995-01-01

    This review of the dynamics of international migration in Southern Africa focuses on four aspects of labor migration: 1) while migrant workers suffer from discrimination and lack of protection, there are few alternatives for them; 2) the regulations imposed by the Chamber of Mines in South Africa favor the mining industry at the expense of the workers; 3) worker supplier states have few options for negotiating a commercialized migration policy to achieve economic benefits; and 4) foreign mine workers must unionize in order to escape perpetual subordination. The review opens with a consideration of how migrant mine workers from Botswana, Lesotho, and Swaziland have provided a source of cheap labor which has enhanced the economic prosperity of South Africa. The role of the Chamber of Mines in regulating the supply of labor and employment policy for its members is described. Attention is then turned to Lesotho where land pressure has exacerbated poverty levels. Large-scale migration has led the citizens of Lesotho to consider it a place to live or retire to, not a place to work. Labor migration from Lesotho is organized, is supported by the government, is recurrent, and remains a viable alternative despite faltering demand. The discussion of Lesotho includes a consideration of its political, economic, and demographic situation as well as of ecological factors. Briefer analyses are then provided for Botswana, Swaziland, and Mozambique. The receiving country, South Africa, is shown to be suffering a decline in economic growth which is marked by widespread unemployment. More than 250,000 Whites are prospective emigrants from South Africa. After considering the issues surrounding refugees, regional concerns created by changing economic and political scenarios, and labor strategies which could be adopted by supplier states, the report reiterates a series of recommendations which arose from two major conferences on the problem of unemployment. It is concluded that the

  19. Imaging the transition from flat to normal subduction: variations in the structure of the Nazca slab and upper mantle under southern Peru and northwestern Bolivia

    Science.gov (United States)

    Scire, Alissa; Zandt, George; Beck, Susan; Long, Maureen; Wagner, Lara; Minaya, Estela; Tavera, Hernando

    2016-01-01

    Two arrays of broad-band seismic stations were deployed in the north central Andes between 8° and 21°S, the CAUGHT array over the normally subducting slab in northwestern Bolivia and southern Peru, and the PULSE array over the southern part of the Peruvian flat slab where the Nazca Ridge is subducting under South America. We apply finite frequency teleseismic P- and S-wave tomography to data from these arrays to investigate the subducting Nazca plate and the surrounding mantle in this region where the subduction angle changes from flat north of 14°S to normally dipping in the south. We present new constraints on the location and geometry of the Nazca slab under southern Peru and northwestern Bolivia from 95 to 660 km depth. Our tomographic images show that the Peruvian flat slab extends further inland than previously proposed along the projection of the Nazca Ridge. Once the slab re-steepens inboard of the flat slab region, the Nazca slab dips very steeply (˜70°) from about 150 km depth to 410 km depth. Below this the slab thickens and deforms in the mantle transition zone. We tentatively propose a ridge-parallel slab tear along the north edge of the Nazca Ridge between 130 and 350 km depth based on the offset between the slab anomaly north of the ridge and the location of the re-steepened Nazca slab inboard of the flat slab region, although additional work is needed to confirm the existence of this feature. The subslab mantle directly below the inboard projection of the Nazca Ridge is characterized by a prominent low-velocity anomaly. South of the Peruvian flat slab, fast anomalies are imaged in an area confined to the Eastern Cordillera and bounded to the east by well-resolved low-velocity anomalies. These low-velocity anomalies at depths greater than 100 km suggest that thick mantle lithosphere associated with underthrusting of cratonic crust from the east is not present. In northwestern Bolivia a vertically elongated fast anomaly under the Subandean Zone

  20. New Apatite and Zircon (U-Th)/He Constraints on the Timing of Thrust-Related Exhumation in the Southern Bolivian (21˚S) Andes

    Science.gov (United States)

    Anderson, R. B.; Long, S. P.; Horton, B. K.; Calle, A.; Stockli, D. F.

    2014-12-01

    Data suggesting rapid middle Miocene uplift of the southern Altiplano prompts resolving disagreements over the geometry, magnitude, and timing of Andean deformation in southern Bolivia (21°S) in order to test geodynamic responses of the thrust belt predicted by the Cordilleran cyclicity model. New apatite and zircon (U-Th)/He data combined with published apatite fission track data (AFT), new 1:50:000-scale mapping, and in-progress drafting of a balanced cross-section provide new insight into the geometry and timing of deformation, and the timing and rates of exhumation. Mapping was focused along an east-west transect through the Subandean Zone (SAZ), Interandean Zone (IAZ), and Eastern Cordillera (EC). Regional-scale folds (~10-20 km wavelength, ~4-6 km amplitude) in the SAZ exhume rocks as deep as Carboniferous above a 10-12 km deep decollemont in Silurian rocks. In the IAZ, thinner (~1-4 km), closely-spaced thrust sheets exhume Devonian and Silurian rocks, and a regional-scale anticlinorium in the easternmost EC exhumes rocks as deep as Cambrian and Ordovician. 11 new apatite and 5 new zircon (U-Th)/He cooling ages provide timing constraints on the initiation of thrust-related exhumation. Zircon cooling ages (32.8±1.4 to 25.4±1.2 Ma) reveal initiation of exhumation in the easternmost EC as early as ~32 Ma, and an exhumed partial retention zone at the EC-IAZ boundary. Apatite ages in the IAZ range from 21.71±0.77 to 7.45±0.20 Ma, and consistently young to the east. Exhumation was previously thought to have begun in the IAZ at ~10 Ma, but our results show thrust-related exhumation as early as ~22 Ma, in agreement with published AFT data that show that deformation had propagated eastward into the IAZ by at least ~18 Ma. In the western SAZ, apatite cooling ages of 6.10±0.17 and 4.84±0.14 Ma demonstrate that thrust-related uplift and exhumation in the western SAZ had begun by at least the late Miocene. These new data show a consistent eastward propagation of

  1. Aplicación del análisis de paleoesfuerzos a regiones plegadas: la compresión terciaria en el sector de Cariñena-Belchite (borde norte de la Cordillera Ibérica

    Directory of Open Access Journals (Sweden)

    Casas Sainz, A. M.

    1996-12-01

    Full Text Available Palaeostress analysis from brittle mesostructures (mainly faults and stylolytes in the norther border of the Iberian Chain (Cariñena-Belchite area shows the existence of several compressional stress states, with σ1, axes oriented NNE-SSW, NW-SE, ESE-WSW. NNE compression direction is consistent with the main shortening direction, responsible for the formation of most macro-structures. Some NE and NW compression directions are due to deflection of the principal compression by larger reverse faults and folds. The deflected compression axes are then perpendicular to macro-structures. ESE compression is early with respect to the main compressional stage, and corresponds either to a intra-mesozoic compression or an Early Tertiary shortening stage. The results obtained in this study indicate that palaeostress analysis in fold-and-thrust areas, even when deformation is not very strong (in this area the total shortening is less than 15 % must be carefully interpreted, taking into account deflections of the stress fields due to larger macro-structures.La aplicación del análisis de paleoesfuerzos a las mesoestructuras frágiles (fundamentalmente fallas y picos estilolíticos del borde norte de la Cordillera Ibérica en el sector de Cariñena-Belchite ha dado como resultado la determinación de cuatro direcciones de compresión: NNE-SSW, NE-SW, NW-SE y ESE-WSW. La dirección de compresión NNE es compatible con la dirección de acortamiento principal responsable de la formación de la mayor parte de las macroestructuras. Las direcciones NE-SW y NW-SE responden a la desviación de la compresión principal por la existencia de fallas inversas o pliegues mayores, colocándose entonces perpendicular o paralela a estos últimos. La compresión ESE es anterior al resto de las compresiones y podría corresponder al Mesozoico o bien a las primeras etapas del Terciario. Los resultados o