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

Current climatic conditions in Central Andes (CA) (31-36° S) have triggered the reduction of glacier area. Although CA are geographically circumscribed to an area under the same macroclimatic domain, their rugged topography creates several topoclimates as response to the effects of elevation, slope and aspect (morphometric factors). This study explores the impact of morphometric factors on the evolution of the glacial surface located above of Maipo volcano (34°09’50’’ S; 69°49’53’’ W). Through the use of 11 LANDSAT images (MSS, TM and OLI), the spatio-temporal evolution of the glacier area was reconstructed (period 1976-2020). On this period, glacier area was reduced by 6±0.5 km2 (-0.14±0.01 km2a-1), equal to 63% of 1976 glacial area (9.6±0.5 km2). Fifty percent of the reduction occurred between 3,900 and 4,400 m elevation, with absolute losses towards lower elevations. In addition, it was detected that for every 100 m of ascent the relative area loss rate decreased 0.1 %a-1 (R2=0.81; p-value

The El Escorial marbles (Cushamen Metamorphic Complex) along with amphibolites form metamorphic septa within the permian granitoids of the Mamil Choique Formation (261-286 Ma). The metamorphism, determined in granulite facies migmatic gneisses septa cropping out 120 km southwest of El Escorial, occurs at 311±27 Ma (CHIME method in monazite). The marbles are calcitic (calcite >95%, R.I.: 0.5 to 2.5%) and show 87Sr/86Sr ratios between 0.70768 and 0.70825 (n=10). The data provided in this work, added to previous contributions, allow to constraints the sedimentation age of the silicic-carbonate successions of the Cushamen Metamorphic Complex between ca. 385 and 335 Ma. This suggests the existence of a mixed carbonate-siliciclastic platform at least in the southernmost portion of southwestern Gondwana between Middle Devonian and early Carboniferous (Middle Mississippian).

The offshore Talara Basin is the western extension of the hydrocarbon producing onshore fields since the mid-1800s area of Peru and is also located above the subduction zone of the active continental margin of South America. The offshore portion was evaluated using high quality 3D seismic where mapping horizons are all unconformities within the Eocene as well as the unconformities at the top Paleocene and top Cretaceous. Possible source rocks are the Cretaceous black marine shales of the Campanian Redondo Formation, the limestones of the Albian Muerto Formation, and the marine shales of the Paleogene. The primary target offshore is expected to be deep-water turbidites of Paleocene/Eocene age with a depositional source from the northeast from highlands created by the compressional uplift of the Andes. The main seals offshore are expected to be shales of the upper Eocene Lagunitos Formation and shales in the Chacra Formation, which are also seals in the onshore Litoral field. Thermal maturation modeling shows that two hydrocarbon kitchens exist in the offshore portion of the Talara basin, one in the north and another in the south. The probable Cretaceous source rocks reached the onset of maturity (VR=0.63%) at a depth of 3,250 to 3,285 m (10,663-10,778 ft) between 30 and 39 Ma (Late Eocene to Oligocene). Importantly, the Cretaceous source rocks stay within the oil window once they enter it in the late Eocene. Satellite studies show a large offshore present-day oil seep in the southern part of the basin and 3D seismic shows direct hydrocarbon indicators (DHIs) imaged as flat spots and bottom simulating reflectors (BSR). Basin modeling suggests hydrocarbon migration pathways would have been updip (to the east) into the onshore traps and would therefore have first filled the offshore traps along the migration pathway. We conclude that the Talara Basin offshore offers excellent exploration opportunities in a proven productive area where multiple prospects have been mapped.

Punctuated lake level drops at Lake General Carrera, Chile, over the last ~13 ka are recorded in multiple stacked deltas that differ in scale. Fifteen delta terrace suites are studied to examine the factors that influence deposit morphology. Surprisingly, the pronounced longitudinal precipitation gradient is inversely correlated with the observed variations in delta size. We find the drainage basins with long-term water storage in glaciers are associated with larger deltas. In these cases, the added contribution of rare, high-magnitude ice meltwater release events (> 600 m3/s) is suggested as the differential driver to enhance delta growth. The overall progradation rate is modest (0.2-1 m/yr), and appears to have slowed over time. For the youngest deltas, we estimate the range in the intermittency factor, a dimensionless measure of the frequency of floods, is 1x10-2 to 4x10-5. Our results illustrate the natural variability of delta growth in a small region (

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The Iglesia basin, in the San Juan Province, is the northern part of a Cenozoic piggy-back basin (the Iglesia-Calingasta-Uspallata basin), located above of the active flat-slab subduction zone of western Argentina. This basin is located between two mountain ranges, the Cordillera Frontal to the west and the Precordillera to the east, affected by thin and thick skinned tectonics, respectively. It is elongated in a north-south direction (70 km) and has a maximum width of 35 km. We have analyzed 17 seismic reflection lines corresponding to more than 500 km of interpreted sections. A strong reflection at 0.5-2 s is interpreted as indicative of shales and sandstones in the upper part of the Agua Negra Formation (Carboniferous); this represents a seismic basement for the Iglesia basin clearly separating stratified (shallower) from chaotic (deeper) reflectors. Several high angle faults have been recognized in the interpreted seismic lines affecting the Neogene fill and even the basement; some of them correlate with structures observed at the surface such us El Tigre Fault System. A 3D model shows the seismic top of basement smoothly deepening down to 3,650 m beneath the Pismanta area. The basement continues upward to the east with a steeper slope clearly defining an asymmetrical shape for the basin. Moreover, there are three depocenters of similar maximum depths around the geothermal hot spring of the Pismanta center. Some of the interpreted faults may be helping in the outflow process of meteoric water heated by a normal geothermal gradient. Considering earthquake data framework, our observations correlate with transpressive deformation likely associated with El Tigre Fault System, which affects Neogene and Pleistocene strata of the Iglesia Group.

Felidae entered South America from North America during the Ensenadan Stage/Age (Early to Middle Pleistocene). For Uruguay their fossil record is scarce but informative, although mostly correspond to large felids (Smilodon, Panthera onca). In this work describes fossil remain of a skull and a mandible assigned, based on morphology and statistical analysis, to Puma concolor. These materials were unearthed from Late Pleistocene sediments (Sopas Formation) from northern Uruguay. Based on these remains some paleobiological and paleoecological aspects are discussed. This specimen had a body mass of about 45 kg, with the potential capacity to hunt animals over 200 kg, which is in agreement with previous reports for other fossil puma remains. During Late Pleistocene, in the current territory of Uruguay, Puma concolor would have shared ecological niche with other large carnivore such as sabre-tooth cats (Smilodon populator, S. fatalis), the jaguar Panthera onca, the canid Protocyon troglodytes, and short-faced bears Arctotherium, feeding upon medium-sized animals in diverse environment.

The discovery of lithium in the Salar de Atacama in northern Chile in 1969 laid the foundations for the development of the world’s leading lithium brine deposit. The available background on the brine deposits located in the Atacama and Maricunga salt flats indicates reserves of 10,879,000 tons of lithium, to which resources are added for 3,335,100 tons of lithium identified in 9 additional Andean and pre-Andean salt flats. The future of exploration is also auspicious considering that there is information on the presence of lithium-bearing brines in another 13 salt flats and 36 identified prospective areas that have not yet been studied. The level of lithium reserves and resources identified and the encouraging expectations for exploration place Chile as a relevant player in the development of the lithium industry worldwide.