ABSTRACT This contribution presents the study of an Ordovician subaqueous felsic succession, formed by the ~400 m-thick Upper Member of the Cordón de Lila Complex (CISL), northern Chile. From bottom to top, the succession starts with two dacitic sills that intruded into the sediments of the lowermost part of the Upper Member. Then, it is followed by a thick sedimentary deposit, two rhyolitic lavas, a volcanoclastic felsic breccia with pyroclastic clasts, and ends with a red rhyolitic lava. The first rhyolitic lava shows centimetric to metric folds with a north-northwestern vergence, evidence of flow in that direction. In the volcanoclastic breccia, an abundant pumice-and-fiamme-rich green matrix wraps around lithic clasts, giving the rock an eutaxitic texture at the outcrop scale. This matrix and texture evidence is characteristic of hot pyroclastic flows deposited under subaqueous conditions. The described section of the breccia is formed by four coarsening-up sequences, reflecting respectively four pulses of building up energy. The lack of internal erosional features points to a single and continuous explosive eruption. An accidental granite clast in the upper part of the breccia suggests a connection with a granitic body, possibly the Pingo-Pingo monzogranite. The geochemical character of the felsic succession is calc-alkaline. The tectonic setting diagram shows a within-plate setting for the succession. This suggests a shift from the arc position inferred for the Lower Member of the CISL to a forearc continental setting for the Upper Member of the CISL.

RESUMEN Este trabajo presenta una sucesión subacuática félsica ordovícica, formada por el miembro superior del Complejo ígneo-sedimentario del Cordón de Lila (CISL), el que posee un espesor de ~400 m. De base a techo, la sucesión incluye dos filones-manto dacíticos, intruidos en sedimentos de la parte inferior de dicho miembro. Luego presenta un intervalo de sedimentitas, dos lavas riolíticas y una brecha volcanoclástica félsica con clastos piroclásticos. La secuencia finaliza con una lava riolítica rojiza. El primer flujo de lava riolítica contiene pliegues métricos a centimétricos con vergencia hacia el nornoroeste, lo que indica un flujo en ese sentido. La brecha tiene una abundante matriz verdosa formada por fiamme y pómez soldadas que rodean a los clastos líticos, y otorgan a la brecha una conspicua textura eutaxítica. El tipo de matriz y la textura observadas son características de flujos piroclásticos calientes depositados en ambientes submarinos. La sección descrita de la brecha puede dividirse en cuatro secuencias granocrecientes, las cuales reflejan, respectivamente, cuatro pulsos de energía creciente. La ausencia de discontinuidades internas apunta a una única erupción explosiva. La presencia de un clasto accidental de granito en la brecha sugiere una conexión con un intrusivo granítico en profundidad, posiblemente el monzogranito Pingo-Pingo. La afinidad geoquímica de la sucesión es calcoalcalina. En el diagrama de ambientes tectónicos, las volcanitas del miembro superior caen dentro del campo de intraplaca. Esto sugiere un cambio desde un ambiente de arco volcánico para el miembro inferior del CISL a una posición de antearco continental para el miembro superior del CISL.

Resumen La ciudad de Morelia es la capital del estado de Michoacán de Ocampo (México) y su centro histórico cuenta con una declaratoria de zona de monumentos históricos, ésta fue publicada el 19 de diciembre de 1990. El 12 de diciembre de 1991 fue inscrita como patrimonio cultural de la Humanidad por la Organización de las Naciones Unidas para la Educación, la Ciencia y la Cultura (UNESCO). Entre las características de su centro histórico destaca la uniformidad de roca ignimbrítica color rosa, usada como material constructivo recubierto y sillares. Sin embargo, el problema de humedad por ascenso capilar afecta considerablemente a los inmuebles del Centro Histórico a través de dos factores principales: 1) la porosidad de la roca, que promedia los ~10 µm y tiene una conectividad del orden de 80 % y 2) niveles freáticos someros con una alta tasa de recarga acentuada durante el periodo de lluvias (mayo a junio). Entre las características de esta importante ciudad colonial se cuenta el resguardo común de acervos documentales y bibliotecas tanto públicas como particulares. Uno de ellos es el archivo de la Sección de Monumentos Históricos del Centro INAH Michoacán, integrado desde hace más de cuatro décadas y que concentra sistemáticamente los datos constructivos e intervenciones en inmuebles del siglo XVI al XIX de todo el estado. Este acervo ocupa un espacio específico en la planta baja del inmueble conocido como Palacio Federal de Morelia, donde la humedad por ascenso capilar es intensa. Para intentar minimizar o desaparecer la humedad que ponía en riego este importante acervo, se aplicó una metodología con materiales naturales, donde el uso de piedra pómez hizo eficiente el proceso de resguardo del acervo. Luego de una serie de pruebas, se observó que la piedra pómez P-HU muestra valores de densidad real ((r) en el rango de las rocas de composición riolítica, sin embargo, su densidad aparente (ρb) se encuentra en un rango < 1g/cm3, menor a la densidad del agua y directamente relacionada con su alta porosidad. Asimismo, la interconectividad entre poros es del orden de 70 %, donde se resalta que la dinámica hídrica de la pómez está relacionada y acotada únicamente por la porosidad accesible al agua. Con base en los resultados generales, las propiedades hídricas están vinculadas estrechamente con la distribución, el tamaño e interconexión de los poros de la pómez. En la práctica, el material en cuestión es altamente eficiente y permite proyectarlo como una opción confiable para la captura de humedad en espacios donde, particularmente, se resguardan libros o documentos de valor cultural o histórico; sin que sea la única aplicación de este material con posibilidades de éxito.

Abstract The city of Morelia is the capital of the state of Michoacán de Ocampo (Mexico) and its historic center has a declaration of zone of historical monuments, published on December 19, 1990. On 12 December 1991 it was registered as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). Among the characteristics of its historic center stands out the uniformity of pink ignimbrite rock, used as a construction material and ashlars. However, the problem of humidity due to capillary ascent considerably affects the buildings of the Historic Center through two main factors: 1) the porosity of the rock, which averages ~10 μm and has a connectivity of the order of 80 % and, 2) shallow water tables with a high rate of recharge accentuated during the rainy period (May to June). Among the characteristics of this important colonial city, there is the common protection of documentary collections and libraries both public and private. One of them is the archive of the Section of Historical Monuments of the Centro INAH Michoacán, integrated for more than four decades, which systematically concentrates the construction data and interventions in buildings from the sixteenth to the nineteenth century throughout the state. This collection occupies a specific space on the ground floor of the building known as the Palacio Federal de Morelia, where the humidity due to capillary ascent is intense. To try to minimize or disappear the humidity that put this important collection at risk, a methodology was applied with natural materials, where the use of pumice stone made the process of safeguarding the collection efficient. After a series of tests, it was observed that the P-HU pumice stone shows values of real density (ρr) in the range of rhyolitic composition rocks, however, its apparent density (ρb) is in a range < 1g/cm3, less than the density of water and directly related to its high porosity. Likewise, the interconnectivity between pores is 70 %, where it is highlighted that the water dynamics of the pumice stone is related and bounded only by the porosity accessible to water. Based on the overall results, water properties are closely linked to the distribution, size and interconnection of pumice pores. In practice, the material in question is highly efficient and allows it to be projected as a reliable option for moisture capture in spaces where, in particular, books or documents of cultural or historical value are protected; without it being the only application of this material with a chance of success.

ABSTRACT Kaolinitic clays have broad prospects in cement production and as a source of pozzolanic materials. The present paper focused on the petrographic and mineragraphic analysis of the Dumañuecos kaolinitic clay deposit, in the municipality of Manatí, Las Tunas province. In the petrographic and mineragraphic characterization of the rocks, polarized light and reflected light microscopy were used. Petrographic analysis revealed the presence of quartz, feldspars and tourmalines; as well as the predominance of granoblastic and cataclastic textures. It was established, through mineragraphic analysis, that the main mineralogical association is quartz + hematite + goethite + pyrite and cement and zonal textures predominate. The occurrence of feldspar spherules with a fibrous-radial internal structure and traces of feldspar phenocrysts indicate the possibility that the source rock of the reservoir is lava with a rhyolitic composition.

RESUMEN Las arcillas caoliníticas tienen amplias perspectivas en la producción de cemento y como fuente de materiales puzolánicos. Este estudio se enfocó al análisis petrográfico y mineragráfico del yacimiento de arcillas caoliníticas Dumañuecos, del municipio de Manatí, provincia de Las Tunas. En la caracterización petrográfica y mineragráfica de las rocas se empleó la microscopía de luz polarizada y de luz reflejada. El análisis petrográfico reveló la presencia de cuarzo, feldespatos y turmalinas; así como el predominio de las texturas granoblásticas y la cataclástica. Se estableció, mediante el análisis mineragráfico, que la asociación mineralógica principal es cuarzo + hematita + goethita + pirita y predominan las texturas de cemento y zonal. La ocurrencia de esférulas de feldespato con estructura interna fibroso-radial y huellas de fenocristales de feldespatos indican la posibilidad de que la roca madre del yacimiento sea una lava de composición riolítica.

ABSTRACT We report new paleomagnetic and rock magnetic data from 12 sites belonging to the Carmichael silicic ash-flow tuff volcanic succession. The base of this succession consists of volcanic breccias, lavas, and lithic tuffs of andesitic composition while the upper unit is composed of crystalline tuffs and welded tuffs both of rhyolitic composition, distributed in the northern central part of the Jalisco block. Their isotopic ages range between 61 and 83 Ma. The rock-magnetic experiments indicate to titanomagnetites with low titanium content as the main magnetic carrier, as well as the presence of titanomaghemites with minor magnetic contribution. Paleomagnetic directions were determined for eleven sites yielding eight normal and three reverse polarity magnetization. Considering all sites, the calculated average address is Dec = 344.7°, Inc = 43.2°, α95= 13.2, and N = 11, with a corresponding virtual geomagnetic pole of VGPlat, = 75.2°N, VGPlong= 186.6°E, A95= 11.7°. The paleomagnetic directions agree fits with expected ones and available mean paleodirections from nearby sites. Our results indicate the stability of the Jalisco block. The occurrence of rotational movements around a vertical axis is not sustained by paleomagnetic data. In addition, the transpressive tectonics previously reported for the northern continental boundary of the Jalisco block (which separates the Sierra Madre Occidental from the Trans-Mexican Volcanic Belt) is apparently not significant since it is not reflected in rotational movements of the Jalisco block.

RESUMEN Se reportan los resultados del estudio paleomagnético y de magnetismo de rocas provenientes de 12 sitios de la Sucesión VolcánicaCarmichaellocalizada en el bloque Jalisco, cuya base está formada por brecha, lava, toba lítica de composición andesítica y tobas de composición riolítica. La unidad superior está compuesta por toba cristalina y toba soldada de composición riolítica. La región estudiada se distribuye en la parte centro norte del bloque Jalisco (BJ), con edades isotópicas entre 61 y 83 Ma. Los resultados de magnetismo de rocas sugieren que la titanomagnetita de bajo contenido en titanio es el principal mineral portador de la remanencia magnética, así como presencia de titanomaghemitas con una influencia magnética menor. Se determinaron las direcciones paleomagnéticas en 11 de los sitios estudiados, y se encontraron 8 de polaridad normal y 3 de polaridad inversa. Las edades isotópicas permiten establecer una correlación con la escala de polaridades geomagnéticas de referencia para el periodo entre el Cretácico Tardío y el Paleoceno. Considerando a los sitios de polaridad inversa como antipodales, la dirección media calculada es de Dec = 344.7°, Inc = 43.2°, α95= 13.2° y N = 11, con un polo geomagnético virtual correspondiente de VGPlat= 75.2°N, VGPlong= 186.6°E, A95= 11.7°. El polo paleomagnético concuerda con los polos esperados según las curvas de referencia de deriva polar. Estos resultados sugieren que el BJ no ha experimentado movimientos rotacionales alrededor de un eje vertical ni desplazamientos latitudinales desde el Cretácico Tardío-Paleoceno hasta el Cuaternario lo que sugiere una cierta estabilidad del bloque Jalisco. Además, la tectónica transpresiva previamente reportada para la frontera continental norte del BJ, que separa la Sierra Madre Occidental de la Faja Volcánica Trans-Mexicana, parece no ser significativa dado que no se ve reflejada en movimientos rotacionales del bloque Jalisco.

ABSTRACT The Mondaca Volcano comprises a thick rhyolitic lava-field and a dome of similar composition, located near the Lontué River Valley headwaters in the northern part of the Southern Andes Volcanic Zone. It reaches a total volume of ~0.85 km3, and it is formed by 4 subunits, named Mondaca 1, 2, 3 and 4, which correspond to successive rhyolitic blocky lava flows, emitted from a rounded dome structure. They present well-preserved flow structures and, in the surroundings, restricted to the south and east of the dome, pyroclastic fall, as well as block and ash deposits are also exhibited. Downstream, along the Lontué River, a laharic deposit is recognized. The lahar was produced after the collapse of an ephemeral ~0.44 km3 lake generated after the river obstruction by viscous lavas, during the 1762 first eruptive phase. Proximal lahar facies are well exposed between 5 and 30 km from their source. The profuse agricultural activity has completely obliterated the lahar’s medium facies deposits along the Central Depression, but are well identified at the mouth of the Mataquito River, 180 km downstream, as a beige-coloured layer, interbedded within dark coastal beach-sands. The identification of overflows and super-elevation deposits formed during the debris flow emplacement along the Lontué River valley, allows to determine a high flow mobility, with estimated velocities that locally reached up to 114 km/h. Petrographic characteristics in addition to chemical composition of lavas from the volcano, pyroclasts and juvenile blocks of the laharic deposit, indicate that all they correspond to high K calcoalkaline rhyolites with subalkaline affinity. These backgrounds, together with the geographical continuity between the lavas and debris deposits along the Lontué and Mataquito rivers, verify facies correlation and common origin as the result of the 1762 Mondaca Volcano eruption complex evolution. Although it was a mainly effusive eruption that could not be observed from Curicó, the collateral consequences would have been catastrophic over a vast area to the south of that city, and evidences one of the largest volcanic disasters in Chilean history. Probably because of the low density polulation at that time, the consequences could have been minor.

RESUMEN El volcán Mondaca está constituido por un campo de gruesas lavas riolíticas y un domo, emplazado en las inmediaciones de las nacientes del valle del río Lontué, en la parte norte de los Andes del Sur. Alcanza un volumen total de ~0,85 km3, y está conformado por 4 subunidades, denominadas Mondaca 1, 2, 3 y 4, que corresponden a emisiones sucesivas de lava riolítica de bloques, cuya fuente es un domo redondeado. Presentan estructuras de flujo bien preservadas y, en las proximidades, al sur y al este del domo, se observan depósitos piroclásticos de caída y de flujos piroclásticos de bloques y cenizas, con escasa extensión areal. Aguas abajo, a lo largo del río Lontué, se reconoce un depósito lahárico generado por la obstrucción del río y el subsecuente colapso del lago efímero de ~0,44 km3 ahí formado el año 1762, durante las primeras fases eruptivas del volcán Mondaca. Las facies proximales del lahar se encuentran bien expuestas y son reconocibles entre los 5 y 30 km desde su fuente. El profuso desarrollo agrícola ha obliterado completamente los depósitos de facies medias del lahar, cuyas facies distales se identifican en la desembocadura del río Mataquito, 180 km aguas abajo, como una capa de color bayo, intercalada en arenas costeras oscuras. El desarrollo de zonas peraltadas durante su emplazamiento a lo largo del valle del río Lontué permite deducir una alta movilidad del flujo, con velocidades estimadas que, localmente, alcanzaron 114 km/h. Las características petrográficas y la composición química tanto de las lavas del volcán como de los piroclastos y bloques juveniles del depósito lahárico indican que corresponden a riolitas calcoalcalinas de alto K de afinidad subalcalina. Estos antecedentes, junto con la continuidad geográfica entre las facies de lavas y los depósitos de detritos a lo largo de los ríos Lontué y Mataquito, corroboran la correlación y origen como el resultado de la compleja evolución del volcán Mondaca, durante la erupción de 1762. Aunque fue una erupción fundamentalmente efusiva que no pudo ser apreciada desde Curicó, sus consecuencias colaterales afectaron una vasta zona de la depresión Central al sur de Curicó, lo que la califica como uno de los mayores desastres volcánicos en la historia de Chile. Probablemente, debido a la baja densidad poblacional en esa época, las consecuencias de esa erupción fueron menores.

Abstract The Chalupas Caldera is a rhyolitic volcano located in the Eastern Cordillera to the Southeast of the Cotopaxi Volcano in the Ecuadorian Andes. It is supposedly fed by a huge magmatic chamber below the caldera. For studying the Chalupas magmatic chamber, the tomographic models obtained by a Tarantola-Valette inversion and studied previously in the entire Ecuadorian region were used. The theoretical basis of the tomography method based on a Bayesian solution of the inverse problem is introduced. The process of the inverse problem regularization is obtained by an L-curve scheme to achieve an optimal solution. The seismic tomography images zoomed in the Chalupas region are well correlated with the main geological terranes and faults documented for the basement of Eastern Cordillera. Based on the tomographic images obtained, it can be assumed that there is not a magmatic chamber of considerable magnitude placed close to the surface underneath the Chalupas Caldera, since it does not present seismic and tomographic evidence to be able to assume a possible volcanic eruption before long. Furthermore, the images allow identifying that the seismic and thermal activity is located beneath the Cotopaxi Volcano as a vertical anomaly beneath the Northeast of Cotopaxi Volcano that corresponds to the phreatomagmatic activity observed in 2015.

Resumen La secuencia de rocas volcánicas y volcano-sedimentarias reportadas en el segmento superior de la Formación Bocas, subyacen sedimentos rojos de la Formación Jordán, está constituida por derrames de lavas máficas a intermedias y rocas piroclásticas félsicas interestratificadas con lodolitas, areniscas y areniscas tobáceas. En este trabajo se exponen nuevos datos de campo, petrográficos y geoquímicos de una secuencia volcánica máfica y volcanoclástica félsica. En cercanías al corregimiento Las Bocas, las rocas básicas presentan bajos contenidos TiO2 (1,04 - 1,65% peso) y P2O5 (0,3 - 0,7% peso) y altos contenidos de Al2O3 (15,79 - 15,92% peso), dentro de las series toleíticas; estas rocas se caracterizan por tener un leve enriquecimiento de LREE, anomalías positivas en Th, U y Zr y anomalías negativas en Nb, Ta y Ti con tendencias de ambiente MORB. Las rocas félsicas que corresponden a rocas piroclásticas de composición riolítica están enriquecidas en álcalis y LREE con anomalías negativas Ba, Sr, Nb, Ta y Ti y enriquecimiento moderado en LREE con un patrón característicos de intraplaca. Por otra parte, la geoquímica de los basaltos de la Formación Nogontova indica un ambiente de tipo MORB. Estos datos y los obtenidos para las rocas de la Formación Bocas sugieren un ambiente de extensión intracontinental (back arc) asociado a subducción.

Abstract The sequence of volcanic and volcano-sedimentary rocks reported in the upper segment of the Bocas Formation, underlying red sediments of the Jordán Formation, is constituted by mafic lava spills and felsic pyroclastic interstratified with mudstones, sandstones and tuffaceous sandstones. This work presents new data field, petrographic and geochemical of one sequence mafic volcanic and felsic volcanoclastic. Near to township of Las Bocas, the basic rocks have low TiO. (1.04 - 1.65% weight) and P.O. (0.3 - 0.7% weight) and high content of Al.O. (15.79 - 15.92% weight), within the tolerance series; these rocks are characterized by a slight enrichment of LREE, positive anomalies in Th, U and Zr and negative anomalies in Nb, Ta and Ti with MORB environment trends. The felsic rocks that correspond to pyroclastic rocks of rhyolitic composition are enriched in alkalis and LREE with negative anomalies Ba, Sr, Nb, Ta and Ti and moderate enrichment in LREE with a characteristic intraplate pattern, on the other hand, the geochemistry of the basalts of the Nogontova Formation indicates a MORB-type environment, these data and those obtained for the rocks of the Bocas Formation suggest a rifting (back arc) environment associated with subduction.

Abstract Throughout history, what has identified the city of San Luis Potosí is a stone extracted from the slopes of the San Miguelito mountain range, which borders the extreme south-south-west of the valley; this stone of a striking pink color characterizes its most emblematic and ancient buildings. Cultural festivals have been designed to make it clear that this is a city with a "quarry soul". Nothing, however, has been said about the history of these rhyolitic rock deposits that allowed the city to gradually cover itself with a unique and, indeed, characteristic face. In this article we approach the evolution of the San Luis quarries, their location and their history, which goes back to the founding years of the city, and how carelessness, ignorance and rapacity are destroying the quarries that fed the local architecture for more than four hundred years.

Resumen A lo largo de la historia, a San Luis Potosí se le ha identificado como una ciudad en cuyas construcciones más emblemáticas y antiguas se ha empleado una cantería de color rosa extraída de las faldas de la sierra de San Miguelito, en el extremo sur-surponiente del valle. Festivales culturales se han diseñado para hacer patente que ésta es una ciudad con "alma de cantera". Nada, sin embargo, se ha dicho sobre la historia de estos yacimientos de roca riolítica que le permitieron a la ciudad irse forrando con un rostro único y, en efecto, característico. En el presente artículo nos acercamos al devenir de las canteras de San Luis, su ubicación y su historia, que se remonta a los años fundacionales de la ciudad, y cómo el descuido, la ignorancia y la rapacidad están acabando con las canteras que alimentaron la arquitectura local por más de 400 años.

Resumen Los estudios del registro geológico del Jurásico en los Andes Septentrionales de Colombia apuntan a que en este lapso se desarrolló de forma simultánea la actividad magmática, el metamorfismo y la sedimentación en este sector de la corteza. En el Macizo de Santander (Cordillera Oriental de Colombia) han quedado registrados vestigios de esta actividad magmática cuyos remanentes actuales se reconocen en mayor medida por la presencia de cuerpos ígneos plutónicos (Grupo Plutónico de Santander). Los nuevos estudios paleontológicos en lodolitas de la Formación Bocas han permitido la identificación preliminar de las especies de conchostracos Shipingia hebaozhaiensis, Euestheria buravasi y Laxitextella multireticulata de una edad correspondiente al Triásico Tardío. La geocronología U/Pb en circones ígneos de una ignimbrita y una toba riolítica de la Formación Jordán indica edades de acumulación de 199,37±0,34 Ma y 198,49± 0,33 Ma, lo que posibilita asignar su edad al Jurásico Temprano. Estos nuevos resultados sugieren que los registros de la actividad volcánica en la Formación Jordán son coetáneos con el desarrollo y la génesis del Grupo Plutónico de Santander (de edad ~202-195 Ma).

Abstract The geological information of the Jurassic record in the Northern Andes of Colombia indicates that during this time, magmatic activity, metamorphism, and sedimentation developed simultaneously. In the Santander Massif (Eastern Cordillera of Colombia), vestiges of this magmatic activity can be recognized by the presence of igneous plutonic bodies (Santander Plutonic Group). New paleontological studies in rocks from the sedimentary record of the Bocas Formation allowed for preliminary identification of conchostracans species: Shipingia hebaozhaiensis, Euestheria buravasi, and Laxitextella multireticulata of the Late Triassic age. U/Pb geochronology in ignimbrite and rhyolitic tuff of the Jordan Formation yielded ages of 199.37 ± 0.34 Ma and 198.49 ± 0.33 Ma defining an Early Jurassic age for this unit. These results indicate that the lithological record of volcanic origin within the Jordan Formation is contemporary with the development and genesis of the Santander Plutonic Group (age ~ 202-195 Ma).

Resumen Fueron caracterizados los cuerpos dómicos del área geotérmica de Paipa, Departamento de Boyacá, separados en tres sectores. El Alto Los Volcanes comprende dos zonas donde son evidentes cuatro elevaciones que sobresalen de la superficie, con afloramientos fuertemente meteorizados, pero con evidentes texturas volcánicas demarcadas por grandes fenocristales de feldespatos potásicos dentro de una masa fundamental blanca. En Quebrada Honda se presenta una estructura dómica donde dominan los megacristales de feldespatos, mientras que el Alto Los Godos comprende cinco cuerpos dómicos con textura porfirítica y cristales de feldespatos. Petrográficamente presentan características similares en los tres sectores, con presencia feldespato potásico (sanidina/anortoclasas) + plagioclasa (albita) + anfíbol (hornblenda) + biotita. Cantidades variables de caolinita se muestran especialmente para algunos reemplazamientos de feldespatos y como venas. Químicamente los cuerpos se clasifican como riolitas/traquidacitas, con firma química de magmas subalcalinos de serie calcoalcalina rica en potasio típico de arcos volcánicos. Los REE muestran un enriquecimiento de las LREE con promedios de (La/Sm)N entre 5,944 y 14,726 respecto a las HREE con valores de (Gd/Yb)N entre 0,626 y 2,318 y con una importante anomalía positiva de EuN/(SmN*GdN)1/2 entre 1,321 y 3,84. Dataciones Ar-Ar en anfíbol y feldespatos, dieron como resultado para el sector del Alto Los Volcanes y Quebrada Honda edades de 1,76 y 1,8 Ma respectivamente, por otro lado, para el Alto Los Godos se registraron para tres domos edades de 2,8, 2,7 y 2,6 Ma. Evidencias de cuerpos intrusivos sin aflorar fueron identificadas al norte y sur del área de trabajo a partir de la geomorfología y resultados geofísicos de otros autores. La cartografía en estos sectores no evidenció litología volcánica, la geomorfología y algunas relaciones con la geofísica adquirida en el área, permiten suponer que se tratan de intrusiones sin expresiones superficiales aumentando las posibilidades de aporte de calor al sistema geotérmico.

Abstract The domes of the geothermal area of Paipa were characterized in three sectors. The Alto Los Volcanes is formed by two zones where four elevations are evident that protrude from the surface, with strongly weathered outcrops but with evident volcanic textures demarcated by big potassium feldspar crystals in a white matrix. In Quebrada Honda there is a domic structure dominated by feldspar megacrystals while the Alto Los Godos is formed by five domes with porphyritic texture and feldspar crystals. Petrographically similar characteristics are present in the three sectors, with the presence of potassium feldspar (sanidine/anortoclase) + plagioclase (albite) + amphibole (hornblende) + biotite. Variable amounts of kaolinite are shown especially for some feldspar replacements and as veins. Chemically, the domes are classified as rhyolites/trachidacites, with a chemical signature of subcalcaline magmas of calcoalkaline series rich in potassium typical of volcanic arcs. The REE shows an enrichment of the LREE with averages of (La/Sm)N between 5.944 and 14.726 respect to the HREE with values of (Gd/Yb)N between 0.626 and 2.318 and with an important positive anomaly of EuN/(SmN*GdN)1/2 between 1.321 and 3.84. Data Ar-Ar in amphibole and feldspar, gave as a result for the sector of Alto Los Volcanes and Quebrada Honda ages of 1.76 and 1.8 Ma respectively, on the other hand, for the Alto Los Godos were recorded for three domes ages of 2.8, 2.7 and 2.6 Ma. Evidences of intrusive bodies that have not emerged were identified in the north and south of the work area based on the geomorphology and geophysical results of other authors. The cartography in these sectors did not show volcanic lithology, the geomorphology and some relationships with the geophysics acquired in the area, allow us to suppose that they are intrusions without superficial expressions increasing the possibilities of heat contribution to the geothermal system.

Abstract This research seeks to identify groundwater recharge and discharge areas in the administrative aquifers of the Ayuquila-Armeria river basin in the states of Jalisco and Colima, Mexico. The Ayuquila-Armeria river basin is one of the 15 most important of the 100 rivers running across the Pacific slope, and is among the 43 most important rivers at the country level. The regional climate is warm-humid in lowlands and subhumid temperate in highlands, with a summer rainy season (June to October) and a dry season the rest of the year. The basin shows a striking relief: from sea level to 4260 m a.s.l. at Nevado de Colima. The identification of these areas was based on a multi-criteria analysis of surface indicators of recharge and discharge areas supported by the flow systems theory (FST). This allows a systemic view of the environment, integrating various elements of nature, in addition to acknowledging groundwater and geological agent that causes a wide variety of processes and manifestations on the surface. The integration of Geographic Information Systems (GIS) and the Multi-Criteria Analysis (MCA) made possible to evaluate the potential recharge/ discharge at the regional level by analyzing physical variables such as lithology, soil, relief, slope, vegetation, precipitation, and a topographic humidity index. In the study area, the territory with high recharge potential ranges from 21% to 80%; the area with low and very low recharge potential, from 4% to 30%. The main potential recharge areas are located in the upper portion of mid-elevation and low mountains covered by pine-oak, oak, and tropical deciduous forests, and grasslands, and to a lesser extent, fir and mountain cloud forests. Soil types include mainly Regosol, Leptosol, Cambisol, Luvisol, Andosol, Umbrisol, and Phaeozem in slopes of 15%-30% covering units of rhyolitic tuff, andesite-basalt, andesite, lahar-pyroclastic rock, granite-granite diorite, and limestone. These areas are located mainly in Sierra de Cacoma-Manantl, Sierra Verde, Sierra de Quila, Sierra de Tapalpa, and the Nevado de Colima volcanic complex. For its part, discharge areas are found mainly in the coastal plains of Jalisco and Colima, associated with Calcisol, Arenosol, Fluvisol, Planosol, Gleysol, Solonchak, and Vertisol soils, and with with halophytic-hydrophytic grassland, bulrush, and mangrove vegetation. These are located in inlandlake areas in San Marcos, Sayula, and Zapotlán. Other discharge areas are the plains and intermontane valleys of Union de Tula and Autlán-El Grullo, as well as the bottom of V-valleys in certain areas of the basin. These can act as natural hydraulic boundaries of flow systems, limiting the amount of groundwater in each zone. The lateral alternation of recharge and discharge areas implies that the water recharged in a particular region may flow to a number of discharge areas, i.e., the water discharged in a given region may come from different regions. The above has important implications in the estimation of the availability estimated from the water balance, since groundwater may flow to more than one discharge area within the same “administrative” aquifer. This type of studies are a first approach providing innovative evidence to the systemic study of groundwater, i.e., the recharge-discharge areas. Their application positively supplements the results of the water balance used in the official evaluation of groundwater availability in Mexico.

Resumen Esta investigación busca identificar las zonas de recarga y descarga del agua subterránea en la cuenca del río Ayuquila-Armería en los estados de Jalisco y Colima. La identificación de estas zonas se logró mediante un análisis multicriterio con la teoría de los sistemas de flujo (TSF). Esta teoría permite obtener una visión sistémica del ambiente, integrando diversos elementos de la naturaleza, además de reconocer el agua subterránea como agente geológico causante de una gran variedad de procesos y manifestaciones en la superficie a través de condiciones naturales contrastantes entre la zona de recarga y descarga de agua subterránea. La integración de los Sistemas de Información Geográfica (SIG) y el Análisis Multicriterio (AMC) permitió identificar los sitios con mayor potencial de recarga y descarga analizando geología, suelo, topoformas, pendiente, vegetación e índice topográfico de humedad (ITH). La superficie con alto potencial de recarga varía de 21% a 80%, mientras que la superficie de descarga, de 4% a 30%. Las principales zonas potenciales de recarga son la sierra de Cacoma-Manantlán, la sierra Verde, la sierra de Quila, la sierra de Tapalpa y el complejo volcánico del Nevado de Colima. Por su parte, las zonas de descarga se encuentran principalmente en las planicies costeras de Jalisco y Colima, así como en una zona de lagos interiores en San Marcos, Sayula y Zapotlán. Otras zonas de descarga las constituyen las planicies y los valles intermontanos de Unión de Tula y Autlán-El Grullo, así como los fondos de valles en V en determinadas zonas de la cuenca.

RESUMEN Las rocas volcánicas y piroclásticas de la Formación Noreán al NW del Macizo de Santander, consisten de lavas desde andesíticas hasta riolíticas y de tobas vítreas, líticas y cristalinas respectivamente. También hay diques y cuerpos hipoabisales principalmente andesíticos. Geoquímicamente las rocas volcánicas y piroclásticas exhiben semejanzas químicas, son de la serie calco-alcalina y presentan anomalías negativas de Nb, P y Ti y positivas de Pb, que sugieren una génesis relacionada con subducción. Los resultados geocronológicos por el método U-Pb en circón arrojaron edades de 192,4 ± 2,2 Ma en una lava de andesita basáltica, 184,9 ± 2,0 Ma en una lava andesítica y 175,9 ± 1,1 Ma en una lava riolítica, las cuales indican la ocurrencia de eventos volcánicos en la Formación Noreán desde el Jurásico Inferior hasta el Medio. Las herencias encontradas en los circones sugieren que el arco volcánico se emplazó en un basamento Meso-Neoproterozoico. La Formación Noréan representa un magmatismo de arco continental y es correlacionable con la Formación Saldaña y con las Vulcanitas de Pitalito del Valle Superior del Magdalena, con las unidades volcánicas jurásicas de la Sierra Nevada de Santa Marta y con la Formación La Quinta de la Serranía de Perijá.

ABSTRACT The volcanic and pyroclastic rocks of the Norean Formation located to the NW of the Santander Massif, are composed by lavas that range from andesitic to rhyolitic, together with glass, lithic and crystal tuffs. Mainly andesitic dikes and hypabyssal bodies are also present. Geochemically, the volcanic and pyroclastic rocks exhibit chemical similarities, belong to the calc-alkaline series and have negative anomalies of Nb, P and Ti and a positive anomaly of Pb, suggesting a subduction-related genesis. LA-ICP-MS U-Pb zircon geochronology resulted in ages of 192.4 ± 2.2 Ma in a basaltic andesite, 184.9 ± 2.0 Ma in an andesitic lava and 175.9 ± 1.1 Ma in a rhyolitic lava, indicating the occurrence of volcanic events in this section of the Noreán Formation from the Lower to the Middle Jurassic. Zircon inheritance suggests that the volcanic arc was emplaced in a Meso-Neoproterozoic basement. The Noreán Formation represents a continental arc magmatism, and can be correlated with the Saldaña Formation and the Pitalito Volcanites of the Upper Magdalena Valley, with Jurassic volcanic units of the Sierra Nevada de Santa Marta and with La Quinta Formation in the Serranía de Perijá.

ABSTRACT: The Serra Geral Formation belongs to the Paraná-Etendeka Magmatic Province (PEMP) and its geochemical and petrographic characteristics are not homogeneous. Many studies segment this group into six basaltic and two rhyolitic magma-types. It is believed that its extrusion occurred through crustal fissures in the Cretaceous, but some authors described the presence of conduits in the shape of basaltic ring structures (BRS) in the Água Vermelha region in the North of the province. The BRS rocks, based on textures and structures, were divided into four groups-central flow, basal flow, main ring dyke and lava flow-with a very similar petrography, composed of plagioclase (labradorite-bytownite), clinopyroxene (augite) and oxide (titanomagnetite) with intergranular texture. The whole-rock analyses of the basal and lava flows allow classifying them as tholeiitic basalts of the Paranapanema magma-type. Geochemical data interpretation suggests an enriched magma source, with low degree of partial melting, high depth of melt generation and without significant crustal contamination. The BRS experienced fractional crystallization on shallow magma chamber, influenced by successive new injections from different parental magmas which would be responsible for the pulses of effusion and explosion. Thus, the singularities of the BRS of Água Vermelha are important to comprehend the evolution of the PEMP.

The hydrochemical and sedimentary features of water bodies are directly linked to climate conditions during genesis and evolution (Williamson et al., 2008). Lacustrine deposits record climatic signals spatially and temporally, so their study allows the reconstruction of these environmental conditions and their evolution (Lapridaet al., 2014). The high resolution of the lake sedimentary record has a key role in paleoenvironmental and paleoclimate understanding (Gierlowski-Kordesch and Kelts, 1994; Bohacs et al., 2000). Hence, paleolimnology is an interdisciplinary science developed from chemical, physical and biological information of sedimentary records of aquatic bodies that allows paleo-environmental reconstruction (García-Rodríguez, 2002). In particular, these studies are performed in current lakes by drilling and core extraction, which limits the interpretation of macro structures given that many cores are required to perform a comprehensive analysis of past environmental and climatic conditions. In this work we analyze the sedimentary sequence of the exposed profile of a paleolake where remains of an equine belonging to the Hippidion devillei species were found (Cerdeño et at., 2008). These remains correspond to dental material consisting in premolars and molars that constitute the first fossil record of a Pleistocene horse found in the province of Mendoza (Argentina) (32º S). The objective of our work is to understand the sedimentary regime and evolution of this high altitude-paleolake (2680 m) associated with the megafauna of South America. This paleolake, named as DL3, is preserved along the Arroyo Minero located in the northwest of Mendoza province, specifically in the north extreme of the El Plata range (Central Andes) (Fig. 1). This paleolake was naturally dammed by the PB3 rock avalanche (Fig. 2). The chronology of this collapse was established by terrestrial cosmogenic nuclides (TCN) dating, performed on surficial big boulders on the top of rock avalanche deposits. 36Cl isotope was used because of the volcanic composition of these blocks. An~ 115±23 Ka age (Moreiras et al., 2015) was determined after discarding a younger result from 4 dated samples (PB4.01 in Table 1). The total lake succession reaches 29 m in thickness, for this reason several profiles were analyzed considering the abrupt topography (Fig. 3). Each level was described considering grain size, sedimentary structures, and main facies according to the lithofacies code of Miall, (1978) (Table 3). Color of layers was determined with field humidity and was described according to the Munsell chart. Descriptions were documented by pictures taken with a digital camera (Sony DSC, zoom 15X). Three sections were a priori established in the whole lake sequence profile. A Lower section corresponding to the lowest 9 m.; the Medium section comprehends the following 10 m up, and the Upper section involves the last 10 m of the sequence. Data of the revealed profiles were used to draw the lacustrine stratigraphic sequence (Fig. 4). Sedimentary analysis shows a thick succession of alternating levels of sands and silts with thicker subordinate boulders and gravels in the profile base. The facies association a is composed by matrix supported gravels, stratified sands and laminated silt-clays (Gm-Sh-Fl) (Table 2) representing the lower 10 meters of the profile. It consists of the interbedding of clays and silts layers of 50-70 mm (Fig. 5a) with 60 mm - thick sand layers. The clays and silts are laminated (facies Fl), with reddish, light brown and green sheets of 0.5 to 1 mm in thickness (Fig. 5b and c); they can be massive (Fm) and present organic matter (OM) content. Sand levels are medium to fine in grain with yellow color. They can be massive (Sm facies) or show planar lamination (Sh facies) within 1-2 cm thick layers. The Sm facies can present CaCO3 nodules (Fig. 5e), associated with oxidized levels showing rain drop marks. The Sh facies presents lags of rhyolitic angular clasts of 5-30 cm in diameter (Fig. 5d), from local outcrops. Towards the top of the lower section we can observe matrix supported gravels (Gm facies) with angular to subangular blocks of 0.07 m in diameter of rhyolitic porphyries and vulcanites within a sabulitic matrix of coarse sand of equal composition, its base is erosive. The facies b association is composed by stratified sands and laminated silt-clays (facies Sh-Sr-Sp-Fl-Fr) that extend over 9 m of the exposed profile (Fig. 6a). The Sh facies is characterized in this case by lentiform levels (Fig. 6b) that may have superimposed load structures and silt cracks (Fig. 6e and f). The Sr facies have ripples of 2 cm in width and 1 cm in height (Fig. 6c). The Sp facies are characterized by 7 cm planar cross-bedding structures forming 0.5-1 cm sets and 2 cm cosets containing the found remains of the Hippidion devillei (Fig. 6d). Silts and clays (facies Fl) contain sand dikes (Fig. 6g) and mud drapes with cracks drying out at the tops. They can form ripples of 0.5 mm in height on inclined surfaces between 10-15°. We identified rework, cut and fill structures supported by silts in diffuse contact. In certain strata, the presence of a reverse fault is observed towards the top of this section. Concerning interpretation of the facies associations, the alternation of facies Sh-Sm with facies Fl suggests a zone of interaction of tractive flows probably sheet flood with processes of deposition by suspension (Young et al., 2003, Fisher et al., 2008). The presence of massive sandstones arranged in coarsening-thickening upward pattern and covered by levels rich in carbonate nodules indicates alteration of the fabric by pedogenetic processes (Retallack, 1994). This indirectly raises the possibility of a system with low sediment input. The deposit of clasts, possibly dealing with a hyper-concentrated flow without lamination, came from the outside or edge of this level. It is ruled out that it is a local fall since no deformation is observed at the base of said level. The angular blocks originating from the Choiyoi Group reinforce the hypothesis of sediment supply from the basin margin. Taking into account the described facies, and the scarce presence of organic matter, one can deduce a sub-environment of ephemeral sandy plain (Smoot and Lowenstein, 1991). While, interpretation of the facies b association with an alternation of facies Sh and Fl with greater contribution of fine sediments allows inferring a more central position in the system with greater dominion of decantation processes and lower contribution of coarse sediments from the margin of the basin through tractive processes (Gierlowski-Kordesch and Rust, 1994). The presence of Sr suggests tractive processes associated with sheet flood flows. The Fr facies suggest ripple formation by wave action in possible bodies of water seasonally generated (Gierlowski-Kordesch, 1998). Loading structures are interpreted as a result of alternating sediments of different densities and with different degrees of water saturation (Van Loon, 2009). The presence of wafers suggests the development of a thin sediment cover during the cessation of water and sediment supply (mud drapes) and subsequent erosion (wafers) during the subsequent flood event of the system (Fisher et al., 2008). The thin covering added to the presence of desiccation cracks is a robust evidence of the system's ephemeral regime (Smoot and Lowenstein, 1991). Sand dams are associated with possible seismites (Obermeier, 1996, Rodríguez-Pascua et al., 2000, Alfaro et al., 2010). The reverse type fault corresponds to the most central area of the playa (Fig. 4i) to which sliding structures (slumps) could have been extended. The dominion of the facies Fl towards the top of the succession allows inferring an ephemeral muddy plain (Smoot and Lowenstein, 1991). Facies associations correspond to two sub-environments: sandy and muddy plains that conform an ephemeral playa lake. The normal gradation trend of layers with presence of thick sediments (Gm) at the base and finer layers (Fl) towards the top of the succession suggest a decrease in the sedimentary contribution over time and a more central position in the basin. These findings are significant for Quaternary paleo environment record of the Central Andes. The predominance of arid climate conditions restricts development and preservation of organic matter. Thus, the use of commonly used techniques such as pollen determination or radiocarbon dating in Quaternary records is practically unfeasible in this region. For this reason, the study of paleolakes if they show well preserved successions, may be a response to this limitation in paleoclimate reconstruction in the Arid Andes.

En este trabajo se estudia el régimen sedimentario de un paleolago donde fueron encontrados restos que constituyen el primer registro fósil de un équido perteneciente a la especie Hippidion devillei, en la provincia de Mendoza (Argentina). Los niveles lacustres donde se encontró el material dentario compuesto por premolares y molares fueron analizados en detalle mediante perfiles estratigráfico-sedimentológicos realizados a distintos niveles en la comarca de Uspallata al pie del Cordón del Plata. En esta sucesión principalmente limo-arenosa de 29 m de espesor total se describieron las estructuras sedimentarias, la granulometría de los depósitos y las facies principales. Este paleolago, represado por una avalancha de rocas pleistocena (~115Ka) permite reconstruir parcialmente el paleoambiente donde vivió el equino. Se trató de un sistema efímero de tipo barreal con períodos de llenado y secado.

Abstract The Amazcala caldera is 30 km northeast of Queretaro City, Mexico, in the central sector of the Mexican Volcanic Belt. It is 14 x 11 km in size and was active from 7.3 to 6.6 Ma. The first caldera event was the Ezequiel Montes Pumice, which was a widespread grey pumice-fall sequence of coarse to fine lapilli, with thicknesses from <1 to ~ 43 m. Colón ignimbrite was next in the evolution of the caldera and consisted mostly of dense pyroclastic density current deposits interbedded with pumice-fall lapilli and minor dilute pyroclastic density current deposits. Several rhyolitic domes form the rim of the caldera, some of which have associated pumice fall and pyroclastic density current deposits. The rim domes still preserve aphyric obsidian, named as Rim Dome Obsidian. A 4 x 2 km intra-caldera lava dome represents the last caldera event, but lacks preserved obsidian. All caldera products are peralkaline rhyolites with chemical characteristics of comendites. A correction of Na2O and K2O was necessary because of secondary hydration of glasses in pumice deposits. This correction process could also be applied in similar weathered or devitrified volcanic deposits at other localities. Al2O3, K2O, Fe2O3, and most REE (except La, Ce) and Y remain practically unchanged from the earliest caldera unit (Ezequiel Montes Pumice) to the last analyzed caldera unit (Rhyolitic Dome Obsidian), and Ba, Sr, La, P2O5 markedly decrease from Ezequiel Montes Pumice to Rhyolitic Dome Obsidia, whereas HFSE Th, Nb, Zr, and TiO2 slightly increase from Ezequiel Montes Pumice to Rhyolitic Dome Obsidian; that is, from pre-caldera collapse to post-caldera collapse. Comparing Amazcala units with calc-alkaline mafic lavas of the area, either pre- or post-caldera, HFSE, REE, and Th are markedly enriched in the Amazcala caldera products. In contrast, Ba, Sr, P2O5, and TiO2 are strongly depleted in the Amazcala units with respect to the mafic rocks. These data suggest a very efficient fractional crystallization process of possible parental mafic magmas. All caldera products are enriched in HFSE, LILE and REE, in particular Nb, Th, Zr and REE, suggesting an input from the fertile mantle during a pulse of continental intra-arc extension in the central sector of the Mexican Volcanic Belt. Amazcala caldera comendites have similar chemical signatures than other caldera comendites at extensional settings within the western sector of the Mexican Volcanic Belt, and with comendites within continental rifts, such as the Kenya rift in Africa.

Resumen La caldera de Amazcala está ubicada a 30 km al NE de la Ciudad de Querétaro, México, en el sector central del Cinturón Volcánico Mexicano. Mide 14 x 11 km y estuvo activa entre 7.3 y 6.6 Ma. El primer evento de la caldera fue la erupción de la Pómez Ezequiel Montes, que consiste en una secuencia de depósitos de caída de lapilli grueso a fino de pómez gris con amplia distribución y espesores de < 1 a ~ 43 m. La ignimbrita Colón fue el siguiente evento en la evolución de la caldera y consiste sobre todo en depósitos de corrientes piroclásticas de densidad intercaladas con depósitos de caída de lapilli de pómez y de corrientes piroclásticas de densidad diluidos menores. Varios domos riolíticos forman el anillo de la caldera, algunos de ellos asociados a depósitos de caída de lapilli gruesos de pómez y de corrientes piroclásticas de densidad menores. Los domos del anillo aún conservan obsidiana afírica, roca que se denominó como Obsidiana de Domo del Anillo. El último evento de la caldera está representado por un gran domo de riolita intra-caldera de 4 x 2 km, pero sin obsidiana preservada. Todos los productos de la caldera son riolitas hiperalcalinas con características químicas de comenditas. Fue necesario realizar una corrección de Na2O y K2O por la hidratación secundaria en el vidrio de los depósitos de pómez. Esta corrección podría aplicarse en depósitos volcánicos similares, alterados o devitrificados de otros lugares. Al2O3 , K2O, Fe2O3 , y la mayoría de los REE (excepto La, Ce) e Y permanecen prácticamente sin cambio desde la primera unidad de la caldera (Pómez Ezequiel Montes) hasta la última unidad analizada (Domos de Obsidiana del Anillo), y Ba, Sr, La, P2O5 se empobrecen notoriamente de Pómez Ezequiel Montes a Domos de Obsidiana del Anillo, es decir, de antes del colapso caldérico a después del colapso. Comparando las unidades de Amazcala con lavas máficas del área, ya sean pre-caldera o post-caldera, HFSE, REE y Th están marcadamente enriquecidos en los productos de Amazcala. En contraste, Ba, Sr, P2O5 y TiO2 están fuertemente empobrecidos en las unidades de Amazcala con respecto a las rocas máficas. Estos datos sugieren un eficiente proceso de cristalización fraccionada de un posible magma parental máfico. Todos los productos de la caldera están enriquecidos en HFSE, LILE y REE, en particular Nb, Th, Zr y REE, sugiriendo una incorporación de magma proveniente del manto fértil durante un pulso de extensión intra-arco en el sector central del Cinturón Volcánico Mexicano. Las comenditas de la caldera de Amazcala poseen una firma química similar a la de comenditas de otras calderas en regímenes tectónicos extensionales en el Cinturón Volcánico Mexicano, y con comenditas de rift continentales como las del Rift de Kenia en África.