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Copyright of Revista de la Asociación Geológica Argentina is the property of Asociacion Geologica Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of Volcanology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tafoni, produced by physicochemical weathering of sandstones, are abundant in the Cerro Colorado (Córdoba province, Argentina). Many of the rock shelters are decorated with rock art of high heritage significance. This art belongs to semisedentary communities from the Late Prehispanic Period (ca. 1550–350 AP). They include morphologies inherited from more humid ancient climates combined with current weathering processes. Evolutionary relief study established that tafoni formation is a product of inherited past wetter climates. Mineralogical and petrographic analyses were performed on samples collected from the sandstones and from various morphologies, weathering residues, and wall and ceiling concretions at four rock shelters, Cueva del Indio, Ricci, Quitilipi, and La Trampa. Gypsum and other salts that are not part of the unaltered rock but the result of weathering reveal the magnitude of hydroclastic and haloclastic processes. These activities form active granular disintegration, flaking, and spalling, and impinge on some painted panels. Mapping the distribution of weathering features and processes at each rock shelter enables the planning of interventions to mitigate and alleviate the effects caused by infiltration of water through rock discontinuities, fractures, and overhangs. It also allows decreasing the accumulation of dust and minimizing muddy water flowing over the paintings. These actions are aimed at retarding the progression of rock art degradation and the visible loss of some paintings. [ABSTRACT FROM AUTHOR]

The Quaternary Campo de la Piedra Pomez ignimbrite (CPPI) is a superbly exposed, partially indurated, rhyolitic ignimbrite emplaced on the southern Puna of Argentina. It is characterized by a variety of facies that record in unprecedented detail the flow dynamics of the parent pyroclastic density currents (PDCs). Detailed facies analysis and internal architecture defined using a sequential stratigraphy approach reveal that CPPI was formed by sustained PDCs, generated from a low fountain eruptive style (boiling over). The PDCs had overall flow conditions characterized by high particle concentration and limited capability to surmount topographic obstacles. The mobility of the PDCs was largely controlled by high pore pressure and the continuous supply at the source (sustained forced convection-dominated PDCs). The successive forestepping-backstepping stacking patterns identified in the CPPI reflect a marked unsteadiness of its parent PDCs due to a pulsating discharge rate at the source. The lateral facies variations in the CPPI record the non-uniform character of its parent PDCs as they flowed outward from the base of the collapsing fountain. Proximal-medial areas characterized by steady aggradation rates pass through to distal braided thalwegs with highly variable aggradation rates, to frontal edges characterized by the step aggradations of secondary decoupled pumice-rich lobes. Collectively, the facies variations in the CPPI record the complex dynamics of sustained PDCs that include pulsating discharge rate at the source, progressive modification of the original topography, and lateral flow transformations. [ABSTRACT FROM AUTHOR]

Crystalline domains in rhyolitic domes and coulees are commonly characterized by spherulites and lithophysae. Spherulites typically range from microscopic to a few centimeters in diameter. Larger spherulites, termed "megaspherulites," are rare but have been reported in the USA and Mexico. The uncommon nature of such structures supports the need for a study to explore the factors and special conditions that allow them to reach such a large size. In the Southern Puna of Argentina, El Viejo Coulee includes megaspherulites up to 4 m in diameter. We present observations from field work, petrography, scanning electron microscopy, bulk geochemistry, and Fourier transform infrared spectroscopy. The megaspherulites occur in obsidian lenses that differ in phenocryst content and composition from the foliated coherent facies that forms the rest of the coulee. The obsidian lacks vesicles and microlites and is unaltered. The megaspherulites comprise growth cones consisting of micropoikilitic texture where quartz encloses potassium feldspar. The growth cones are separated by interconal areas composed of lithophysae. We propose that the megaspherulites were formed above the glass transition temperature (Tg) and are the product of primary crystallization of rhyolitic melt. The exceptionally large size of the megaspherulites implies high diffusion rates which are favored by temperatures above Tg during crystallization. The large size also suggests scarcity of nucleation sites, which is consistent with the megaspherulites being hosted by unaltered microlite- and vesicle-free glass. The position of the obsidian lens at the base of the coulee may have played a critical role in maintaining the temperature above the Tg long enough to allow the crystallization of the megaspherulites. These conditions also favored crystallization in the most advanced stage where micropoikilitic texture replaced the fans of crystal fibers typical of spherulites. Crystallization of anhydrous quartz and feldspar in the growth cones led to the concentration of volatiles in the melt in the interconal areas, resulting in volatile exsolution and formation of vesicles that became nucleation sites for lithophysae. The study advances our understanding of some of the special processes that are involved in the cooling and solidification of rhyolitic magmas. Fundamentally, we find that the position of the obsidian at the base of the coulee was critically important because this position favored maintenance of the temperature above the Tg which, in turn, favored high diffusion rates. Also, the scarcity of nucleation sites in the obsidian melt allowed only a small number of spherulites to nucleate; those that nucleated therefore grew very large. The meter-scale megaspherulites may have taken ~ 55 years to create. [ABSTRACT FROM AUTHOR]

A comprehensive morphostratigraphic and chronological study of the complete set of Holocene tephras from Tafí and Santa María valleys (northwestern Argentina), including analyses of compositional characteristics, is presented. Five ash tephras are recognized: V0 (El Rincón), V1a (Carreras 1a ash), V1b (Carreras 1b ash), V2a (Carreras 2 ash), and V2b (El Paso 3 ash). Two of them (V1b and V2b) are described for the first time in the study area. The new 14C and accelerator mass spectrometry ages presented, along with the previously published information, allows for the establishment of a chronological framework. The V0 tephra was deposited in the Early Holocene (about 10,000 yr BP), V1a and V1b were deposited in the Middle Holocene (about 4200 and 3500 yr BP, respectively), and V2a and V2b were deposited in the Late Holocene (after about 800 yr BP). The mineralogical, textural, and geochemical characterizations of the five tephras suggest that their tephra provenance was mainly from the back-arc region. However, the determination of the exact source of each tephra requires more accurate high-resolution tephrochronological studies. At least five major eruptions affected the Tafí and Santa María valleys in the last 10,000 yr. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Ciencias Agrícolas is the property of Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Mexicana de Ciencias Agrícolas is the property of Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil compaction is a problem recently identified as one of the main constraints on the maize surface of the municipality of Villaflores in the region of The Frailesca, Chiapas, due to this, it needs to be studied with greater precision. The objective of this study was to characterize the problem of compaction on the mechanized surface cultivated with corn in the New Mexico commn. We studied 177 plots, in which the apparent density, organic matter and texture were determined at the depths of 0-20 and 20-40 cm. The owners of the properties were interviewed to obtain information about their cultivation practices and corn productivity levels. The results show that 83.3% of the studied area presented superficial compaction and 94.6% compaction in the subsoil (plow floor). The producers pointed out that in years with critical periods of drought the yields are reduced by 58%, which is correlated with the decrease of the porosity as a result of the compaction. The main causes of the compaction were the intensive tillage with machinery 100% of the sites, the very low content of 100% organic matter and the type of soil (luvisols and acrisols). The attention of the compaction problem requires a comprehensive corrective and preventive strategy that should take as a central element the elevation of the contents of organic matter, to reverse the current unsustainable management of the land. [ABSTRACT FROM AUTHOR]

On 13 June 2015, the London Volcanic Ash Advisory Centre (VAAC) warned the Buenos Aires VAAC about a possible volcanic eruption from the Nevados Ojos del Salado volcano (6879 m), located in the Andes mountain range on the border between Chile and Argentina. A volcanic ash cloud was detected by the SEVIRI instrument on board the Meteosat Second Generation (MSG) satellites from 14:00 UTC on 13 June. In this paper, we provide the first comprehensive description of this event through observations and numerical simulations. Our results support the hypothesis that the phenomenon was caused by wind remobilization of ancient pyroclastic deposits (ca. 4.5 ka Cerro Blanco eruption) from the Bolsón de Fiambalá (Fiambalá Basin) in northwestern Argentina. We have investigated the spatiotemporal distribution of aerosols and the emission process over complex terrain to gain insight into the key role played by the orography and the condition that triggered the long-range transport episode. Numerical simulations of windblown dust were performed using the ARW(Advanced Research WRF) core of the WRF (Weather Research and Forecasting) model (WRF-ARW) and FALL3D modeling system with meteorological fields downscaled to a spatial resolution of 2 km in order to resolve the complex orography of the area. Results indicate that favorable conditions to generate dust uplifting occurred in northern Fiambalá Basin, where orographic effects caused strong surface winds. According to short-range numerical simulations, dust particles were confined to near-ground layers around the emission areas. In contrast, dust aerosols were injected up to 5-6 km high in central and southern regions of the Fiambalá Basin, where intense ascending airflows are driven by horizontal convergence. Long-range transport numerical simulations were also performed to model the dust cloud spreading over northern Argentina. Results of simulated vertical particle column mass were compared with the MSG-SEVIRI retrieval product. We tested two numerical schemes: with the default configuration of the FALL3D model, we found difficulties to simulate transport through orographic barriers, whereas an alternative configuration, using a numerical scheme to more accurately compute the horizontal advection in abrupt terrains, substantially improved the model performance. [ABSTRACT FROM AUTHOR]

On the 13 June 2015, the London Volcanic Ash Advisory Centre (VAAC) warned the Buenos Aires VAAC about a possible volcanic eruption from the Nevados Ojos del Salado volcano (6879 m), located in the Andes mountain range on the border between Chile and Argentina. A volcanic ash cloud was detected by the SEVIRI instrument on board the Meteosat Second Generation (MSG) satellites from 14:00 UTC on 13 June. Further studies concluded that the phenomenon was caused by remobilization of ancient pyroclastic deposits (circa 4.5 Ka Cerro Blanco eruption) from the Bolsón de Fiambalá (Fiambalá Basin) in northwestern Argentina. In this paper, we provide the first comprehensive description of the dust episode through observations and numerical simulations. We have investigated the spatio-temporal distribution of aerosols and the emission process over complex terrain to gain insight into the key role played by the orography and the condition that triggered the long-range transport episode. Numerical simulations of windblown dust were performed using the WRF-ARW/FALL3D modeling system with meteorological fields downscaled to a spatial resolution of 2 km in order to resolve the complex orography of the area. Results indicated that favourable conditions to generate dust uplifting occurred in northern Fiambalá Basin, where orographic effects caused strong surface winds. According to short-range numerical simulations, dust particles were confined to near-ground layers around the emission areas. On the other hand, dust aerosols were injected up to 5-6 km high in central and southern regions of the Fiambalá Basin, where intense ascending airflows are driven by horizontal convergence. Long-range transport numerical simulations were also performed to model dust cloud spreading over northern Argentina. Results of simulated vertical particle column mass were compared with the MSG-SEVIRI retrieval product. We tested two numerical schemes: with the default configuration of the FALL3D model, we found difficulties to simulate transport through orographic barriers, whereas an alternative configuration, using a numerical scheme to more accurately compute the horizontal advection in abrupt terrains, substantially improved the model performance. [ABSTRACT FROM AUTHOR]

This paper presents a detailed geological map at the 1:20,000 scale of the Tocomar basin in the Central Puna (north-western Argentina), which extends over an area of about 80 km2 and displays the spatial distribution of the Quaternary deposits and the structures that cover the Ordovician basement and the Tertiary sedimentary and volcanic units. The new dataset includes litho-facies descriptions, stratigraphic and structural data and new 234U/230Th ages for travertine rocks. The new reconstructed stratigraphic framework, along with the structural analysis, has revealed the complex evolution of a small extensional basin including a period of prolonged volcanic activity with different eruptive centres and styles. The geological map improves the knowledge of the geology of the Tocomar basin and the local interplay between orogen-parallel thrusts and orogen-oblique fault systems. This contribution represents a fundamental support for in depth research and also for encouraging geothermal exploration and exploitation in the Puna Plateau region. [ABSTRACT FROM AUTHOR]