Andean

The signature of the Ocloyic Orogeny (Ordovician). Many of the metamorphic and deformational events associated to low-grade units in NW Argentina have been linked with ancient orogenies, like the Pampean (Cambrian) and the Ocloyic (Ordovician) cycles. The lack of specific ages in the low-grade metamorphic rocks of the Famatina belt, as well as the absence of a detailed stratigraphic analysis, have led to ambiguous interpretations respect to the Paleozoic evolution of the southern segment of the Central Andes. Recent work allows recognition of two units within the low-grade 'metamorphic basement'; the Negro Peinado and the Achavil formations. Provenance analysis relates deposition of both units to the final stages of the Pampean cycle during the Cambrian, whereas an Ordovician (Ocloyic) synorogenic nature is suggested for the La Aguadita Formation, also traditionally included within the low-grade 'metamorphic basement'. Thus, as a whole, these units are younger than the traditionally correlated pre-Pampean Puncoviscana Formation. K-Ar ages obtained for Famatina indicate that low-grade metamorphism and deformation of these units are Ordovician, in contrast to a much older age (Proterozoic-Middle Cambrian) previously suggested. Ages of 457±9 Ma (whole rock) and 463±14 Ma (<2µm fraction) for the Negro Peinado Formation allow establishing a link with the climax of the Ocloyic Orogeny developed along western Gondwana during the early Paleozoic. Ages of 435±12 Ma (<2µm fraction) in the La Aguadita Formation and of 444±8 Ma (whole rock) in phyllonites of the Angulos shear zone are consistent with an extent into the earliest Silurian for this cycle. Additionally, a 359±7 Ma (<2µm fraction) age for the Negro Peinado Formation (Las Trancas shear zone) indicates local resetting within the age range assigned to the Achalian Orogeny (Late Silurian-early Carboniferous).

A number of glacial moraines are distributed from the eastern margin of the Torres del Paine drainage basin to near the present margin of the Patagonian Ice Fields, together with a set of regionally continuous lacustrine terraces related to glacial fluctuations. The geomorphology, supported by lake sediment evidence, indicates the existence of a single proglacial paleolake in this area, here referred to as the Great Tehuelche Paleolake. This concept helps to clarify the chronology of glacial events and leads to a better understanding of the evolution of the hydrologic system in the Torres del Paine area. Glacial advances previously referred to as A, B and C occurred during the Last Glacial Maximum and fed the Great Tehuelche Paleolake with meltwater, allowing it to reach its maximum extension. The discovery of thrombolites at Laguna Amarga suggests that the drainage of the paleolake towards the Última Esperanza Fjord took place at 7,113 Cal. yr BP, after the melting of an ice barrier that existed during the earlier glacial advance. This gave rise to the development of a complex fluvio-lacustrine hydrologic system that persists to the present day.

The Supreme Court of Justice of the United States in Association for Molecular Pathology vs Myriad Genetics, Inc rules out patents over isolated DNA as they were not different from products of nature, yet it maintains patents over synthetizes genes or DNAc. This decision has redefined the scope of the doctrine of products of nature on biotechnological invention as established by Diamond vs Chakrabarty. Coincidentally, the Supreme Court´s new interpretation is in harmony with the Andean Tribunal of Justice´ rulings. This article analyses the doctrine of products of nature in the light of Association for Molecular Pathology vs Myriad Genetics, Inc, its implications for the biotechnological industry and the jurisprudence of the Andean Tribunal of Justice.

An anisotropy of magnetic susceptibility (AMS) transect was carried out across the Fuegian Andes, in Argentina, with the aim of studying its tectonic evolution. Two-hundred and forty oriented samples were collected from 27 sites distributed between the Paso Garibaldi to the north and the Canal Beagle to the south. The study was restricted to the Upper Jurassic Lemaire Formation, with a single site located in the Lower Cretaceous Yahgán Formation. Studied rocks comprised basaltic, andesitic, volcaniclastic and sedimentary rocks affected by low-grade metamorphism. AMS measurements were complemented with thin section analyses of representative samples in order to characterize the microstructures and metamorphic assemblages. In general, the magnetic fabric shows dominant oblate shapes and a large variation in the anisotropy degree from 1.04 up to 2. The anomalously high values were observed to be associated to growth of secondary pyrrhotite, which was identified by rock magnetic tests. Magnetic foliation was generally consistent with slaty cleaveage as observed in the field, confirming the tectonic origin of the magnetic fabric. Three geographic domains were distinguished in the study region on the basis of the pattern of the AMS axes distribution. In the northern domain, from Paso Garibaldi to Valle Carbajal, the orientation of the maximum susceptibility axis (k 1 ), or magnetic lineation, is N-S to NE-SW with moderate plunge towards the S-SW and coincides with previous determination of mineral lineations associated with the Andean deformation and very low grade metamorphism. The magnetic fabric pattern can be correlated with the main deformational phase responsible for the development of slaty cleavage (main Andean deformational phase) and the tectonic transport due to progression of the Fuegian fold and thrust belt in the Late Cretaceous. A different character is shown along the Valle Carbajal domain, where subvertical E-W magnetic foliation planes and roughly E-W to ESE-WNW subhorizontal magnetic lineations are more difficult to correlate with the main folding phase and suggest its relation to an E-W, possibly localized, strike-slip regime during the main deformational and metamorphic phase. The magnetic fabrics in the third domain, close to the Canal Beagle, displays a more heterogeneous character with both E-W and N-S striking foliations; in this case a population of subhorizontal E-W magnetic lineation (k 1 ) suggests the existence of a significant component of strike-slip deformation.

Newly described outcrops, excavations and sediment cores from the region of Última Esperanza, Magallanes, contain tephra derived from the large late-glacial explosive R1 eruption of the Reclús volcano in the Andean Austral Volcanic Zone. New radiocarbon dates associated to these deposits refine previous estimates of the age, to 14.9 cal kyrs BP (12,670±240 14 C yrs BP), and volume, to >5 km 3 , of this tephra. The geographic and stratigraphic distribution of R1 also place constraints on the evolution of the ice-dammed proglacial lake that existed east of the cordillera in this area between the termination of the Last Glacial Maximum (LGM) and the Holocene. This proglacial lake generated wavecut terraces, and also caves, such as the Cueva de Milodón, along the highest prominent terrace. The current elevation of these terraces depends on the total amount of post-glacial isostatic rebound, which is unknown. Due to differential rebound, the highest prominent lake terraces decrease in height from west-to-east, from ~170 m a.s.l. on Península Antonio Varas west of Seno Última Esperanza, to ~150 m a.s.l. around Lago Sofía, and down to ~125 m a.s.l. along their easternmost margin. The presence of thick deposits of R1 tephra in some of the caves around Lago Sofía implies that the proglacial lake had already dropped below its highest level prior to the time of this eruption, and, in fact, even earlier, prior to 16.1 cal kyrs BP (13,560±180 14 C yrs BP), when land mammals first occupied these caves. The depositional environment of R1 in a core from Dumestre bog suggests that the lake level was in fact <80 m a.s.l. at the time of this eruption. The original lake may have drained to this level across the low elevation pass between Fiordo Obstrucción and Seno Skyring, and subsequently into Seno Otway and the Pacific Ocean, when Canal Jerónimo opened up prior to the R1 eruption. Another suite of cores, from the Eberhard site, indicate that the lake persisted at >70 m a.s.l. until 12.8 cal kyrs BP (10,695±40 14 C yrs BP). However, a 14.2 cal kyrs BP (12,125±85 14 C yrs BP) Mylodon pelvis from a nearby site, located at only ~7 m a.s.l., suggests that the lake could have emptied, for at least a brief period, to this low level at this time. This latter datum, combined with the lack of any prominent terraces between the highest ones (170-125 m a.s.l.) and much lower ones (at only 30 m a.s.l. on Península Antonio Varas and 20 m a.s.l. along the coast north and south of Puerto Natales), suggests abrupt changes in the lake level after the R1 eruption. The likely mechanism for producing these changes in Última Esperanza was the catastrophic failure and subsequent re-sealing of an ice dam in Paso Kirke, the only below sea-level pathway west to the Pacific north of Fjordo Obstrucción. The final stage of lake drainage, from the lower terrace level (20-30 m a.s.l.) occurred at 10.3 cal kyrs BP. : [82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97] 2011 RESuMEn. Evolución de lagos proglaciales embalsados por hielo en Última Esperanza, Chile: Implicancias de la explosión volcánica tardiglacial R1 del volcán Reclús, Zona Volcánica Austral Andina. En este trabajo reportamos hallazgos de tefras derivadas de la gran explosión volcánica tardiglacial R1 del volcán Reclús situado en la Zona Volcánica Austral Andina, a partir de nuevos afloramientos, excavaciones y testigos sedimentarios de lagos y pantanos, obtenidos en la región de Última Esperanza, Magallanes. Nuevas fechas asociadas a estos depósitos permiten refinar su edad a 14,9 ka cal AP (12.670±240 14 C años AP) y su volumen a >5 km 3 . Además, la ubicación geográfica y estratigráfica de R1 permite acotar la evolución del lago proglacial represado por hielo que se desarrolló al este de la cordillera al intervalo temporal entre el término del Último Máximo Glacial y el Holoceno. Este lago proglacial generó terrazas y cuevas, producto de la acción del oleaje, como la Cueva de Milodón, a lo largo de la terraza más alta y conspicua. La altitud actual de estas terrazas depende de la cantidad total de rebote isostático posglacial, el cual se desconoce. Debido a las variaciones en el rebote isostático posglacial, las terrazas lacustres más altas y prominentes disminuyen en altitud de oeste a este, desde ~170 m s.n.m. en la Península Antonio Varas, al oeste del Seno Última Esperanza, a 150 m s.n.m. alrededor del lago Sofía y descienden hasta ~125 m s.n.m. a lo largo de su margen más oriental. La presencia de grandes depósitos de la tefra R1 en algunas de las cuevas alrededor del lago Sofía indican que el lago proglacial ya había descendido, con respecto a su nivel más alto, antes de la erupción de R1 y de hecho incluso antes de 16,1 ka cal AP (13.560±180 14 C años AP) que es cuando los mamíferos terrestres ocuparon por primera vez estas cuevas. El ambiente deposicional de R1, en el registro sedimentario del pantano Dumestre, sugiere incluso que el nivel del lago era inferior a 80 m s.n.m. durante el momento de esta erupción. Probablemente el lago proglacial original habría drenado a este nivel a través de sectores de baja altitud ubicados entre fiordo Obstrucción y seno Skyring, siguiendo hacia el seno Otway para desembocar en el Océano Pacífico, una vez que el canal Jerónimo ya estaba libre de hielo antes de la erupción de R1. Otro grupo de testigos, del sitio Eberhard, indican que el lago persistió a >70 m s.n.m. hasta 12,8 ka cal AP (10.695± 14 C años AP). Sin embargo, a 14,2 ka cal AP (12.125± 14 C años AP), la pelvis de Mylodon de un sitio cercano, ubicado a 7 m s.n.m., sugiere que el lago podría haberse vaciado temporalmente durante este período. Este último dato, combinado con la ausencia de terrazas prominentes entre las más altas (170-125 m s.n.m.) y las más bajas (a solo 30 m s.n.m. en la Península Antonio Varas y 20 m s.n.m. a lo largo de la costa norte y sur de Puerto Natales), sugiere cambios abruptos en el nivel del lago proglacial después de la erupción de R1. Probablemente el mecanismo que ocasionó estos cambios en Última Esperanza fue la ruptura catastrófica y el subsecuente resellamiento del dique de hielo que bloqueaba el Paso Kirke, el único paso al Océano Pacífico bajo el nivel del mar al norte del fiordo Obstrucción. El drenaje final del lago, desde la terraza inferior (20-30 m s.n.m.), ocurrió a los 10,3 ka cal AP.