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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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
This thesis develops tools aimed at the study and prediction of climate effects on land-surface hydrology (in particular streamflow), which require a minimum amount of site specific data. This minimum data requirement allows studies to be performed in areas that are data sparse, such as the developing world. ¶ ...
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Sobehrad, Susan Je. "Pre-Cretaceous erosional surface of the Llano Uplift region, Central Texas." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-3915.
Historical research reveals a repeating pattern of uplift, erosion, and deposition in the region of the Llano Uplift, central Texas. This report examines the topography of the pre-Cretaceous landscape. The data consist of points, in three dimensions, that are located on the erosional surface, as determined by three methods. Category I data lie upon the contact between Cretaceous strata and underlying Paleozoic sediments or Precambrian basement; Category II data are defined in the subsurface from well logs; and Category III data are topographic high points where the Cretaceous has eroded away, but the underlying unit has not eroded (an exhumed surface). Digital mapping procedures were used to create triangulated irregular networks, three dimensional scenery, and topographic profiles. The digitally reconstructed surface is compound, consisting of higher, older erosional surfaces, incised into by rejuvenated stream activity to create lower, younger surfaces. This valley/divide topography, which is regional in extent, could not have been visualized without modern GIS technology. text
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Singh, Manish K. "Correlation & biostratigraphy of surface and shallow subsurface sections of the Barnett Shale, Llano Uplift, south-central, Texas." 2007. http://digital.library.okstate.edu/etd/umi-okstate-2434.pdf.
McCraw, David J. "A geologic summary of the Llano de Albuquerque: A diachronous ~1.5-1.65 (?) Ma geomorphic surface complex marking the cessation of Santa Fe Group deposition in the western Albuquerque Basin." In 67th Annual Fall Field Conference. New Mexico Geological Society, 2016. http://dx.doi.org/10.56577/ffc-.83.
