Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The seabed included in the Chilean Exclusive Economic Zone (EEZ) has proper conditions to originate and host different ore deposits, but its geological knowledge is scarce and scattered. The existent studies are very limited in terms of geochemical and mineralogical analyses. The most significant non-energetic mineral resources off Chile correspond to Fe-Mn nodules and crusts, phosphorite deposits, gold and titanium placer deposits and massive sulfide deposits. Fe-Mn nodule sites occur in abyssal plains and seamounts, and around volcanic islands, at depths from 2,890 to 4,332 m, and can contain important concentrations of Cu and Ni (up to 1.38% Cu+Ni) and Co (up to 0.53%). Co-rich Fe-Mn crust occurrences have been reported around the Rapanui and Salas y Gómez islands, with Cu+Ni contents up to 0.3%. Phosphorite sites occur in Holocene sedimentary beds of the continental shelf off Peru and northern Chile, with P2O5 average content of 22.6%. Gold placer deposits are found in beaches and channels of southern Chile and may extend offshore probably in submarine canyons. Titanium placer deposits have been evaluated in different beaches of Chile and could also be continued offshore. Platinum anomalies have been found in channels and bays of southernmost Chile. No samples of Volcanogenic Massive Sulfide (VMS) mineralization are known in the Chilean EEZ to date. However, samples of hydrothermal vents, with potential for polymetallic VMS type mineralization, have been recovered around the Rapanui Island, and several seamount and volcanic island chains indicate favorable conditions for formation and preservation of these ore-deposits. The available geological information on the seabed of the Chilean EEZ is insufficient to estimate the real potential of its non-energetic mineral resources.

In this work, we present two new records of Lagostomus from the late Miocene of Argentina. A right mandible from the Huachipampa Formation (Loma del Camello, San Juan Province) is assigned to Lagostomus telenkechanum, previously recorded in the Arroyo Chasicó Formation (Chasicoan Stage/Age, late Miocene; Arroyo Chasicó, Buenos Aires Province). A skull fragment from the Cerro Azul Formation (Salinas Grandes de Hidalgo, La Pampa Province) is referred to L. pretrichodactyla, previously recorded in several units assigned to the Huayquerian Stage/Age (late Miocene) in Catamarca and Mendoza provinces, and sediments of uncertain age in Buenos Aires Province. The presence of L. telenkechanum in the Huachipampa Formation supports a Chasicoan age for this unit, which corroborates previous hypotheses, and extends the area of distribution of this species. The presence of L. pretrichodactyla in the Cerro Azul Formation suggests a late Miocene age (probably Messinian) for this unit, at least at Salinas Grandes de Hidalgo, supporting previous hypothesis. These new records allow recognizing the biostratigraphic value of Lagostomus to a higher geographic scale than previously considered.

A middle Hettangian marine gastropod assemblage is reported from the Kenai Peninsula of south-central Alaska supplying new paleontological evidence of this group in Lower Jurassic rocks of North America. Pleurotomaria pogibshiensis sp. nov. is described from the middle Hettangian marine succession informally known as Pogibshi formation, being the first occurrence of the genus in the Kenai Peninsula and the oldest occurrence of the genus in present-day Alaska and North America. One species of the genus Lithotrochus, namely Lithotrochus humboldtii (von Buch), is also reported for the first time from the Kenai Peninsula. Lithotrochus has been considered as endemic to South America for a time range from the early Sinemurian to the late Pliensbachian. The newest occurrence of Lithotrochus in rocks of the Pogibshi formation extends the paleobiogeographical and chronostratigraphical distribution of the genus into the present-day Northern Hemisphere. However, the Southern Hemisphere affinities are consistent with the hypothetical interpretations (although supported both by paleobiogeographical and paleomagnetic data) that the Peninsular terrane of south-central Alaska is far-traveled and may have originated at much more southerly paleolatitudes than its present-day position. Two other Early Jurassic caenogastropods typical of the Andean region of South America and of the Tethyan epicontinental seas are described for the first time in the Pogibshi formation, and these are Pseudomelania sp. and Pictavia sp. The new gastropod assemblage reported here shows close affinities with coeval South American and European gastropod faunas, supplying new evidence to interpret their distribution during the Early Jurassic.

Los estudios paleoecológicos en la Patagonia brindan información de los cambios experimentados por la vegetación y el clima durante el Holoceno. La evolución climática de esta región ofrece una oportunidad única para el estudio de los posibles mecanismos e interacciones entre los agentes responsables de la variabilidad ambiental y los cambios en los ecosistemas. La dinámica de los ecosistemas boscosos está modulada por la ocurrencia de disturbios. Los incendios son uno de los disturbios más importantes en ecosistemas templados boscosos, y su estudio permite contrastar de manera independiente las inferencias sobre los cambios ocurridos en los ecosistemas. Además, en la Patagonia los cambios ambientales y de vegetación posglacial han sido en gran medida determinados por los cambios en la temperatura y la posición e intensidad de los vientos del oeste (westerlies). Con el objetivo de reconstruir los cambios en la vegetación y en los patrones de diversidad vegetal durante el Holoceno, en relación con la dinámica posglacial, a los disturbios naturales y antrópicos en la cuenca del lago Argentino, se analizó el contenido polínico y de partículas de carbón de una secuencia sedimentaria de la península Avellaneda (Argentina). La reconstrucción de la vegetación basada en el registro polínico fósil sugiere cambios no cíclicos en la diversidad vegetal durante el Holoceno. Las comunidades arbustivo-gaminosas frías, altamente diversas, que dominaron hasta el Holoceno Temprano, fueron desplazadas hacia pisos altitudinales mayores a lo largo del Holoceno y reemplazadas por estepas y bosques menos diversos. Por otro lado, el Holoceno Temprano y Medio se caracterizaron por tener oscilaciones de balance hídrico opuestos entre comunidades andinas y extrandinas desarrolladas entre los 48-50° S. Sin embargo, los períodos de mayor actividad de incendios ocurren en forma sincrónica en ambos tipos de comunidades ubicadas al este de los Andes. El Holoceno Tardío se caracteriza por presentar indicadores con señales diversas dependiendo de la ubicación geográfica de los registros paleoecológicos. Por último, el estudio detallado de la representación polínica actual a lo largo del gradiente de vegetación altitudinal, permitió describir y evaluar las relaciones entre los conjuntos polínicos y la vegetación, lo cual contribuyó a una mejor compresión de los cambios encontrados en el registro polínico fósil.

Lakes located downwind of active volcanoes serve as a natural repository for volcanic ash (tephra) produced during eruptive events. In this study, sediment cores from four lakes in Cajas National Park, southern Ecuador, situated approximately 200 km downwind of active volcanoes in the Northern Andes Volcanic Zone, were analysed to document the regional history of tephra fall extending back around 3,000 a cal BP. The ages of the lacustrine sedimentary sequences were constrained using a total of 20 AMS radiocarbon ages on plant remains. The tephra layers were correlated among the lakes based on their radiocarbon age, elemental composition, colour, and grain morphology. We found five unique tephra layers, each at least 0.2 cm thick, and further constrained their ages by combining the results from two age-depth modelling approaches (clam and rbacon). The tephra layers were deposited 3,034±621, 2,027±41, 1,557±177, 733±112, and 450±70 a cal BP. The ages of all but the youngest tephra layer overlap with those of known eruptions from Tungurahua. Some tephra layers are missing as macroscopic layers in several cores, with only two of the five tephra layers visible in the sediment of three lakes. Likewise, previous studies of lake sediment cores from the region are missing the four youngest tephra layers, further highlighting the need to sample multiple lakes to reconstruct a comprehensive history of fallout events. The newly documented stratigraphic marker layers will benefit future studies of lake sediments in Cajas National Park.

En el Cordón de Lila y la Sierra de Almeida, región de Antofagasta, norte de Chile, afloran rocas plutónicas graníticas pertenecientes a un batolito cambro-ordovícico (490-460 Ma) que forma parte del arco magmático famatiniano. Los plutones que lo constituyen son de composición granodiorítica y monzogranítica, respectivamente. Los primeros ocupan una posición occidental en tanto que los segundos, oriental. La diferencia geoquímica entre ambos tipos de rocas es el enriquecimiento en sílice y K de las segundas respecto de las primeras. La mayoría de las granodioritas son metaluminosas o están en el límite entre el campo metaluminoso y el campo peraluminoso. Los monzogranitos son marcadamente peraluminosos. La composición química de los plutones (elementos mayores, en trazas y elementos de las tierras raras) permite inferir un origen común para ambos grupos, a partir de un magma máfico que evolucionó por cristalización fraccionada. Las diferencias de composición entre ambos, en particular su carácter meta- o peraluminoso, puede ser explicado por diferentes grados de interacción del magma con las rocas corticales félsicas.

Prof. Hubert Miller passed away February 26, 2020, near his hometown München in Bavaria.

Introduction. Water stress has been recorded as one of the main environmental factors responsible for seasonal fluctuations in passion fruit yields. However, there is a shortage of information on the influence of water stress on different components of growth. Objective. To evaluate the controlled deficit irrigation (RDC) technique in the passion fruit cultivation (Passiflora edulis Sims) and its possible effects on plant nutrition, efficient use of water, crop productivity and fruit quality. Materials and methods. An trial was conducted during the years 2013 and 2014 in the Experimental Field of the Institute of Agronomy, Universidad Central de Venezuela, Maracay, Venezuela; under tropical dry forest conditions. The statistical design was randomized blocks with three irrigation treatments (R1= 100 % of Eto (reference evapotranspiration), R2= 66 % of Eto, and R3= 33 % of Eto), in the non-critical phenological phases of the crop, four replications and twelve plants per experimental unit. Flowering and fructification were defined as critical phases. Nutritional variables (N, P, K, Ca and Mg content in leaf tissue, and N, K and Ca content in sap), production efficiency (efficient water use, kg fruit plant-1and kg fruit ha-1) and fruit quality ( physical and chemical variables) were evaluated. Results. The application of RDC did not affect the nutritional variables or the crop yield. As regard to fruit quality, only significant differences were presented for percentage (%) of peel and juice, however, the values with R2, the values were not limiting in both variables. Conclusion. The restriction of the water supply in non-critical phases did not affect the agronomic performance of the plant.