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1
Guzman, Oswaldo, Corina Campos, Merlus Ruiz, Isandra Angel, Riccardo Vassallo, and Nataly Aranda. "Geomorfología y Sedimentología del sector medio del valle de pueblo llano, Andes de Mérida, Venezuela." Revista Bases de la Ciencia. e-ISSN 2588-0764 4, no. 3 (December 31, 2019): 1. http://dx.doi.org/10.33936/rev_bas_de_la_ciencia.v4i3.1906.
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Un análisis geomorfológico y sedimentológico fue realizado en el sector medio del Valle de Pueblo Llano con la finalidad de comprender la génesis de los sedimentos y geoformas cuaternarias presentes en el área. Cuatro sectores con características morfológicas y sedimentológicas distintivas fueron identificados: (i) depósitos en masa de flujos de detritos con una expresión superficial cónica interpretados como abanicos aluviales, (ii) depósitos de flujos unidimensionales que constituyen terrenos relativamente planos con bajas pendientes característicos de terrazas fluviales, (iii) depósitos de diamicton que constituyen un conjunto de lomos y depresiones en forma de arco asociados a un complejo de morrenas frontales, y (iv) depósitos de flujos unidimensionales que conforman terrenos con forma de lomos asimétricos, asociados a condiciones fluvio-glaciares. Estos resultados ponen en evidencia que los glaciares asociados a la Glaciación Mérida en el Valle de Pueblo Llano, alcanzaron elevaciones al menos 300 m más bajas que las reportadas previamente en la literatura para los Andes de Mérida. Además, sugieren que otros valles glaciares presentes en los Andes de Mérida pudieron haber experimentado fenómenos similares.
Palabras clave: Andes de Mérida, Geomorfología y Sedimentología, Morrenas, Glaciación Mérida, Pueblo Llano.
Abstract:
A geomorphological and sedimentological analysis was carried out in the Middle reach of the Pueblo Llano Valley to understand sediment genesis and quaternary geoforms present in the area. Four zones with distinctive morphological and sedimentological characteristics were identified: (i) mass deposits of debris flow with a cone-shaped surface interpreted as alluvial fans, (ii) unidirectional flow deposits with relatively flat topography, with little slope, characteristic of fluvial terraces, (iii) arc-shaped diamicton deposits that constitute a set of crests and valleys, associated to a complex of frontal moraines, and (iv) unidirectional flow deposits that form terrains with the shape of asymmetric ridges, associated to a fluvio-glacial conditions. These results show that the glaciers of the Mérida Glaciation in the Pueblo Llano Valley reached elevations of at least 500 m lower than those previously reported in the literature for the Mérida Andes. In addition, they suggest that other glacial valleys present in the Andes of Mérida might have experienced similar phenomena.
Keywords: Mérida Andes, Geomorphology and Sedimentolology, Moraine complex, Mérida Glaciation, Pueblo Llano.
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Lanigan, David, John Stout, and William Anderson. "Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado." Aeolian Research 21 (June 2016): 131–37. http://dx.doi.org/10.1016/j.aeolia.2016.04.001.
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Toscas, Eliseu. "Sentimiento de pertenencia local y territorio en una colectividad del llano de Barcelona entre el antiguo régimen y el estado liberal: Sarria (1780-1860)." Estudios Geográficos 55, no. 216 (September 30, 1994): 503–29. http://dx.doi.org/10.3989/egeogr.1994.i216.503.
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En una colectividad del Llano de Barcelona y en una época de rápidos y trascendentales cambios (1780-1860), el autor confronta «parroquia» y «municipio» entendidos como marcos de referencia colectivos. Se pone el énfasis en la diferente percepción del espacio político según se trate del mundo oficial o de la vida cotidiana, y de los grupos dominantes o de las clases subalternas, realizando con ello una aportación al estudio de la génesis de las estructuras territoriales.
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Darling, J. Andrew. "Notes on Obsidian Sources of the Southern Sierra Madre Occidental." Ancient Mesoamerica 4, no. 2 (1993): 245–53. http://dx.doi.org/10.1017/s0956536100000936.
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AbstractRecent fieldwork has identified a previously unknown obsidian source area in southern Zacatecas and northern Jalisco. Evidence of prehistoric use of surface gravel and nodule outcrops in the Huitzila-La Lobera source area includes raw-material extraction and the production of cores, large blade blanks, rough bifaces, and other artifacts. Unusual variability in color is characteristic of the sources and includes a banded variety described as “rainbow” obsidian. Characteristics of this source area are compared to the Llano Grande obsidian source area in Durango. Implications for understanding the distribution of obsidian from sources in the Sierra Madre Occidental to the cultures of the north Mesoamerican frontier are presented and discussed.
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Suquet, H., S. Chevalier, C. Marcilly, and D. Barthomeuf. "Preparation of porous materials by chemical activation of the Llano vermiculite." Clay Minerals 26, no. 1 (March 1991): 49–60. http://dx.doi.org/10.1180/claymin.1991.026.1.06.
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AbstractA mild acid attack of the Llano vermiculite produces porous materials suitable for use as cracking catalysts and/or catalysts supports. After HCl attack at 80°C (1 m), the number of acid sites measured by the Hammett indicator method is ∼0·50/nm2, and the specific surfaces are 245 m2/g after calcination at 550°C (4 h), and 55 m2/g after steaming at 750°C (4 h). The performance of leached (1 m HCl) vermiculite has been compared with another hydrocarbon cracking catalyst—γ-Al2O3. The leached vermiculite produces a definite higher conversion and higher C3, C4 and gasoline yields, but much lower coke production. By electron microscopy, infrared spectroscopy, X-ray powder diffraction and thermal analysis, it has been shown that the leached vermiculite samples are composed of more or less attacked layers retaining their original platy morphology, and non-crystalline hydrated silica. Chemical analyses indicate that octahedral cations are dissolved first.
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Bescos, A., and A. M. Camarasa. "Caracterización hidrológica del rio Arga (Navarra): el agua como recurso y como riesgo." Estudios Geográficos 59, no. 232 (July 6, 2018): 389. http://dx.doi.org/10.3989/egeogr.1998.i232.609.
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El agua constituye un elemento vital para el desarrollo de los ecosistemas naturales, así como de los enclaves humanos. La creciente ocupación antrópica de los valles aluviales está creando conflictos, cada vez más patentes, entre el uso del recurso y la prevención del riesgo. Estos problemas adquieren una dimensión considerable en el caso del río Arga, afluente del Ebro. Se trata de una cuenca de régimen pluvio-nival que presenta importantes reservas de agua. La población y las actividades económicas que en ella se asientan vienen experimentando una importante expansión desde los años 60, vinculada, sobre todo, al desarrollo industrial (Cuenca de Pamplona) y agrícola (llano aluvial). En los últimos treinta años este crecimiento ha supuesto un aumento considerable de las demandas hídricas, a la vez que del riesgo de inundación. El presente trabajo analiza los aspectos físicos que determinan el funcionamiento hidrológico de la cuenca del Arga, así como la presión antrópica sobre el llano aluvial. Se analiza la demanda hídrica y la ocupación de las zonas inundables, en un intento de caracterizar ambas facetas del agua: recurso y riesgo.
[fr] L'eau constitue im élément fondamental pour le déroulement des écosystèmes naturels autant que des enclaves humains. La croisant occupation anthropique des vallées alluviales est en train de produire des conflits, de plus en plus évidents, entre l'usage du ressource et la prévention du risque. On a trouvé ces problèmes, au bassin versant du fleuve Arga, un affluent de la rivière Ebro. Il s'agit d'un bassin de régime pluvio-nival qui présente des importants ressources d'eau. La population et les activités économiques que y sont installées ont expérimenté une puissante expansion, lié surtout, au développement industriel (Pamplona) et agricole (plaine alluvial). Dans les dernières trente années, cet accroissement a supposé un considérable augmentation des demandes hydriques, au même temps que le risque d'inondation. Le présente travail analyse les aspects physiques qui déterminent le fonctionement hydrologique du bassin versant du Arga autant que la pression humaine sur la plaine alluvial. On analyse la demande hydrique et l'occupation des zones inondables, en prétendant de caractériser la double facette de l'eau: ressource et risque.
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Collins, Jamie L., Mark E. Everett, and Brann Johnson. "Detection of near-surface horizontal anisotropy in a weathered metamorphic schist at Llano Uplift (Texas) by transient electromagnetic induction." Physics of the Earth and Planetary Interiors 158, no. 2-4 (October 2006): 159–73. http://dx.doi.org/10.1016/j.pepi.2006.05.008.
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Coello, Juan J., Carolina Castillo, and Esther Martı́n González. "Stratigraphy, Chronology, and Paleoenvironmental Reconstruction of the Quaternary Sedimentary Infilling of a Volcanic Tube in Fuerteventura, Canary Islands." Quaternary Research 52, no. 3 (November 1999): 360–68. http://dx.doi.org/10.1006/qres.1999.2074.
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La Cueva del Llano is a volcanic tube of Pleistocene age on Fuerteventura Island, in the Canary Islands. Part of it is infilled with sediments of external origin. These deposits are exceptional in stratigraphic complexity and thickness compared with other known tube infillings, and they comprise nine stratigraphic units deposited in five phases. In Phase I, which has not been dated, sedimentation of cinder from a nearby cone occurred. Phase II began ca. 16,830 ± 900 14C yr B.P., whereas phase IV dates to 9280 ± 370 14C yr B.P. The interpretation of sedimentary features shows that phases III and V correspond to a dry climate, similar to the present one, whereas the climate was much wetter during phases II and IV. This paleoclimatic sequence agrees with those suggested by the study of deposits formed in other sedimentary environments, not only in Fuerteventura but on other islands of the Canary group and the Sud-Maroc region.
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Rozanski, Kazimierz, Ingeborg Levin, Jürgen Stock, Raul E. Guevara Falcon, and Fernando Rubio. "Atmospheric 14CO2 Variations in the Equatorial Region." Radiocarbon 37, no. 2 (1995): 509–15. http://dx.doi.org/10.1017/s003382220003099x.
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We present here first results of 14CO2 monitoring at two sampling sites in the equatorial region of the South American continent (station Aychapicho, Ecuador and station Llano del Hato, Venezuela). We also include the data for two other stations representing undisturbed marine atmosphere at mid-latitudes of both hemispheres, far from large continental sources and sinks of CO2 (station Izaña, Tenerife, Spain and station Cape Grim, Tasmania). Between 1991 and 1993, 14CO2 levels in the tropical troposphere were generally higher by 2–5‰ when compared to mid-latitudes of both hemispheres. This apparent maximum of 14C in the tropics can be explained by two major factors: 1) emissions of 14C-free fossil fuel CO2, restricted mainly to mid-latitudes of the northern hemisphere; and 2) 14C depletion due to gas exchange with circumpolar Antarctic upwelling water, influencing mainly mid- and high southern latitudes. The δ14C record so far available for the Aychapicho station provides direct evidence for a regional reduction of atmospheric 14CO2 levels due to gas exchange with 14C-depleted equatorial surface ocean in the upwelling regions and dilution with the 14C-depleted CO2 released in these areas. Recurrent ENSO events, turning on and off the 14C-depleted CO2 source in the tropical Pacific, lead to relatively large temporal variations of the atmospheric 14C level in this region.
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Alcover, J. A., J. C. Rando, F. García-Talavera, R. Hutterer, J. Michaux, M. Trias, and J. F. Navarro. "A reappraisal of the stratigraphy of Cueva del Llano (Fuerteventura) and the chronology of the introduction of the house mouse (Mus musculus) into the Canary Islands." Palaeogeography, Palaeoclimatology, Palaeoecology 277, no. 3-4 (June 2009): 184–90. http://dx.doi.org/10.1016/j.palaeo.2009.03.016.
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Piasecki, S., and C. Marcussen. "Oil geological studies in central East Greenland." Rapport Grønlands Geologiske Undersøgelse 130 (December 31, 1986): 95–102. http://dx.doi.org/10.34194/rapggu.v130.7949.
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Field work undertaken in central East Greenland during August 1985 was a follow-up of the oil geological studies by GGU expeditions to Jameson Land in 1982 and 1983 (Surlyk, 1983; Surlyk et al., 1984a). Three major subjects were covered by the field work. The Permian-Triassic boundary was studied along the western margin of the Jameson Land basin (Surlyk et al., 1984b). A series of closely sampled sections along the exposures of the eastern part of the Schuchert Dal was completed. The sampled material will be analysed with respect to source rock quality, maturity and stratigraphy. Secondly, the analysis of the regional maturity in southern Jameson Land based on the material from the 1982-83 expeditions indicates a specific surface maturation pattern (Piasecki, 1985; Thomsen, 1985) which had to be confirmed or rejected by analyses of further material from localities throughout the area. New material was collected along Hurry Inlet and in the southern llnd western parts of Jameson Land. Maturity studies will be supplemented by stratigraphical and geochemical analyses at these localities. The third target of the field work was to start oil geological studies of the area north of Kong Oscar Fjord, and to locate drill sites for shallow-core drilling in immature potential source rocks. The island of Traill ø was visited for two days of helicopter reconnaissance. Wollaston Forland was visited for two days at the end of the season in co-operation with geologists of a British Petroleum (BP) party working in this area. Material was collected for preliminary source rock studies and biostratigraphy.
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Aray Castellano, Jélime Cecilia, Pierre Lacan, Víctor Hugo Garduño Monroy, Jesús Ávila García, Joaquín Gómez Cortés, Franck A. Audemard M., Octavio Lázaro Mancilla, and William Bandy. "Geophysical characterization of a potentially active fault in the Agua Fría micro-graben, Los Azufres, Mexico." Boletín de la Sociedad Geológica Mexicana 73, no. 2 (August 1, 2021): A040121. http://dx.doi.org/10.18268/bsgm2021v73n2a040121.
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In this study, three geophysical techniques were used to identify, localize, and characterize a partly blind fault in the Llano Grande basin within the Agua Fría Graben. This tectonic basin is located in the Los Azufres Volcanic Complex, one of the major silicic volcanic centers in the Trans-Mexican Volcanic Belt. The 1 km wide Agua Fría graben could be considered as an analogous of the larger graben structures bounded by the Morelia-Acambay Fault System. Since it is filled by recent sediments, it represents a challenge for the recognition and characterization of active faults that lack clear surface expression. Newly collected magnetic data led to the identification of lineaments interpreted as structural discontinuities. Ground penetrating radar and seismic refraction surveys were carried out across one of these magnetic lineaments crossing the basin to characterize the nature and geometry of the inferred discontinuity. The ground penetrating radar profiles allowed the identification of buried deformational structures interpreted as the northern segment of the Agua Fría fault. The subsurface reflectors displaced 1 to 1.5 m by the fault indicate that this structure is potentially active. The opening of trenches based on these results makes it possible to confirm the interpretation of the geophysical profiles, to discuss the precision of the data and to validate their use for such studies. On seismic refraction profiles, the deformation zones are related to low P-wave velocity zones. These geophysical studies demonstrate the potential of such techniques to locate faults in the subsurface, partially characterize the width of the fault zone and the associated displacement within the uppermost of the subsurface. Our results may be applied to define ideal sites for paleoseismic excavations which are essential for the identification and description of historical and prehistoric earthquakes, and thus, for the characterization of the local seismic hazard.
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Kyle, J. Richard, Daniel F. Stockli, Earle F. McBride, and Brent A. Elliott. "Covering the Great Unconformity in southern Laurentia during Rodinia breakup: Detrital zircon studies of provenance evolution during Cambrian marine transgression (Llano Uplift, Texas)." GSA Bulletin, August 23, 2022. http://dx.doi.org/10.1130/b36389.1.
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The Llano Uplift in central Texas, USA, exposes the southernmost expanse of Laurentian crystalline basement in North America and the overlying lower Paleozoic strata deposited on the Great Unconformity. Systematic detrital zircon (DZ) U-Pb provenance analysis of the Hickory Sandstone—the basal unit of the Cambrian Riley Formation that onlaps the Mesoproterozoic core of the Llano Uplift—yielded locally variable DZ U-Pb signatures with ages ranging from 1800 Ma to 485 Ma (n >1700). The Hickory Sandstone zircons are dominated by 1550−1300 Ma (50%) and 1300−1000 Ma (46%) ages. These two dominant Mesoproterozoic DZ age components likely were sourced from local Grenville metamorphic and igneous basement of the Llano Province (1300−1000 Ma) and from the extra-regional Granite-Rhyolite Province basement to the north and northwest of the Grenville Front, which suggests both local sourcing and a regional drainage system supplying sediment to the southern Laurentian margin during the Cambrian. This interpretation is supported by a minor component of 1800−1600 Ma zircons, sourced from the Yavapai-Mazatzal Province, and zircons with Early Cambrian ages that were likely sourced from the Wichita Igneous Province, which is located to the northwest and to the north of the Llano Uplift, respectively. Documented NNW-trending topographic ridges in the Mesoproterozoic basement surface of the Llano Uplift could have funneled aeolian and fluvial sand supply to the southern Laurentian coast that was reworked in the marginal marine environment. Samples from the western Llano Uplift are dominated by regionally sourced, early Mesoproterozoic Granite-Rhyolite Province DZ ages, whereas samples from the eastern Llano Uplift exhibit a dominant locally sourced Grenville signature. Hickory Sandstone samples also contain a small number of Neoproterozoic (850−600 Ma) and Cambrian (541−487 Ma) zircons. Sources for Neoproterozoic zircons likely were located along the Laurentian continental margins and derived from extension-related magmatism associated with the breakup of Rodinia. Cambrian zircons are most common in Hickory Sandstone samples on the southern and western flanks of the Llano Uplift. Some are reasonably sourced from the Wichita Igneous Province to the north, but the younger Cambrian zircons suggest sources to the west. Upper Hickory strata are dominated (>60%) by 1550−1300 Ma grains with up to 10% >1600 Ma Paleoproterozoic grains. Upper Cambrian sandstones of the Wilberns Formation also contain a significant contribution of >1600 Ma grains, which suggests a possible enlargement of the fluvial headwaters over time extending into older Laurentian provinces to the north and northwest. Differences among DZ populations over relatively limited distances may have been related to NW-oriented ridge and corridor landforms that developed on the Great Unconformity surface, which were products of the Proterozoic tectonic and lithologic architecture affected by aeolian and fluvial processes at this unusual stage in Earth history. Paleocurrent data and atypical detrital grain characteristics for a Hickory Sandstone locality in the southeastern Llano Uplift and its DZ age similarities with Cambrian sandstones of the Argentine Precordillera suggest a common provenance prior to or during Rodinia breakup.
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Moraru, Manuela, Adriana Perez-Portilla, Karima Al-Akioui Sanz, Alfonso Blazquez-Moreno, Antonio Arnaiz-Villena, Hugh T. Reyburn, and Carlos Vilches. "FCGR Genetic Variation in Two Populations From Ecuador Highlands—Extensive Copy-Number Variation, Distinctive Distribution of Functional Polymorphisms, and a Novel, Locally Common, Chimeric FCGR3B/A (CD16B/A) Gene." Frontiers in Immunology 12 (May 24, 2021). http://dx.doi.org/10.3389/fimmu.2021.615645.
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Fcγ receptors (FcγR), cell-surface glycoproteins that bind antigen-IgG complexes, control both humoral and cellular immune responses. The FCGR locus on chromosome 1q23.3 comprises five homologous genes encoding low-affinity FcγRII and FcγRIII, and displays functionally relevant polymorphism that impacts on human health. Recurrent events of non-allelic homologous recombination across the FCGR locus result in copy-number variation of ~82.5 kbp-long fragments known as copy-number regions (CNR). Here, we characterize a recently described deletion that we name CNR5, which results in loss of FCGR3A, FCGR3B, and FCGR2C, and generation of a recombinant FCGR3B/A gene. We show that the CNR5 recombination spot lies at the beginning of the third FCGR3 intron. Although the FCGR3B/A-encoded hybrid protein CD16B/A reaches the plasma membrane in transfected cells, its possible natural expression, predictably restricted to neutrophils, could not be demonstrated in resting or interferon γ-stimulated cells. As the CNR5-deletion was originally described in an Ecuadorian family from Llano Grande (an indigenous community in North-Eastern Quito), we characterized the FCGR genetic variation in two populations from the highlands of Ecuador. Our results reveal that CNR5-deletion is relatively frequent in Llano Grande (5 carriers out of 36 donors). Furthermore, we found a high frequency of two strong-phagocytosis variants: the FCGR3B-NA1 haplotype and the CNR1 duplication, which translates into an increased FCGR3B and FCGR2C copy-number. CNR1 duplication was particularly increased in Llano Grande, 77.8% of the studied sample carrying at least one such duplication. In contrast, an extended haplotype CD16A-176V – CD32C-ORF+2B.2 – CD32B-2B.4 including strong activating and inhibitory FcγR variants was absent in Llano Grande and found at a low frequency (8.6%) in Ecuador highlands. This particular distribution of FCGR polymorphism, possibly a result of selective pressures, further confirms the importance of a comprehensive, joint analysis of all genetic variations in the locus and warrants additional studies on their putative clinical impact. In conclusion, our study confirms important ethnic variation at the FCGR locus; it shows a distinctive FCGR polymorphism distribution in Ecuador highlands; provides a molecular characterization of a novel CNR5-deletion associated with CD16A and CD16B deficiency; and confirms its presence in that population.
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Razo-Paredes, Jose Trinidad, and Erika Toledo-Trejo. "Phytoremediation with Eichhornia crassipes and Cyperus papyrus in the Llano Dam in the Municipality of Villa del Carbón, State of Mexico." Journal Urban-Rural and Regional Economy, June 30, 2019, 17–20. http://dx.doi.org/10.35429/jurre.2019.4.3.17.20.
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The Llano dam is a body of surface water that has been used as a source of water for irrigation and tourist activities such as rowing and fishing tournaments; This dam is located in the municipality of Villa del Carbón in the State of Mexico and there is a history of contamination by enterobacteria and phosphorus (Razo J. et al; 2016). Due to the mentioned importance of this body of water, the objective of this work was to carry out phytoremediation through the use of islands based on recyclable material (PET) and with the plant species Eichhornia crassipes and Cyperus papyrus. The phytoremediation evaluation was performed over a period of three months considering 3 arm, center and curtain sampling zones. The presence of enterobacteria was evaluated as indicators of microbiological contamination and in terms of physicochemical parameters, temperature, dissolved oxygen, pH, hardness, sulfates, nitrates and phosphates were evaluated. The microbiological results showed absence of enterobacteria in the central area of the body in the last sampling, it should be noted that the behavior of the physicochemical parameters is very variable, the values of nitrates and phosphates are related to the presence of enterobacteria, when modified it has an effect on the microorganisms mentioned above. It is important to note that the lack of environmental education in both site administrators and visitors affected the efficiency of the islands as they were moved to the banks of the dam reducing the contact of the phytoremediation islands with water.