Showing papers in "Journal of South American Earth Sciences in 2003"

TL;DR: In this article, velocities relative to the South American plate for five GPS stations on the Nazca plate were presented and used to estimate the modern Euler vector, with a pole at 55.88N, 92.58W with a rotation rate of 0.60 8/Myr.

TL;DR: A review of available data and previous interpretations, leads to the conclusion that rifting from the Ouachita embayment of Laurentia occurred in the Early Cambrian and collision with the Famatina arc on the western margin of Gondwana occurred in Middle-Late Ordovician as discussed by the authors.

TL;DR: In this article, a detailed survey of the provenance of the Patagonian Andes metamorphic complexes is presented, which includes the discovery of Proterozoic zircons.

TL;DR: In this article, large-scale, mostly N−S-striking normal faults and open cracks that run along the forearc of northern Chile have been documented, at least since the Pliocene, and they are interpreted as tensile fractures formed by either concomitant normal faults or coseismic extension.

TL;DR: In this paper, small outcrops of the basement of the Deseado Massif, consisting of weathered, altered granitoids and their metasedimentary host rocks, were dated by the U-Pb zircon method using thermal ionization mass spectrometry and ion microprobe (SHRIMP).

TL;DR: The pre-Andean basins were formed by continental extension and strike-slip movement before the development of the Mesozoic-Cenozoic Andean magmatic arc as mentioned in this paper.

TL;DR: In this paper, a regional balanced cross-section of the Patagonian Andes orocline was restored in four stages that represent the main events of compressive deformation.

TL;DR: Apatite fission-track analysis was used for the determination of thermal histories and ages in Precambrian areas of southeast Brazil as discussed by the authors, where the collected samples are from different geomorphologic blocks.

TL;DR: Llambias, Eduardo Jorge as discussed by the authors, Eduardo J. Jorge and Eduardo A. López-Gonzalez, 2013. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina.

TL;DR: In this paper, Sandstone petrography, geochemistry (major, trace, and rare earth elements [REE]), and Nd isotopic composition are presented for the siliciclastic Lower Caradoc Pavon Formation of the San Rafael block, central west Argentina.

TL;DR: The upper Cambrian-Tremadocian Santa Rosita Formation, the lowermost unit of the Santa Victoria Group in northwest Argentina, records part of the infill of a retroarc basin this paper.

TL;DR: The TIPA shear zone is a prominent tectonic element of the Las Termas belt of NW Argentina as discussed by the authors, which is characterized by NNW-SSE-trending ductile shear zones.

TL;DR: In this article, the Sierras Septentrionales of the southern Buenos Aires province were used to confirm that this region is the southern extension of the crystalline basement of the Rio de la Plata craton.

TL;DR: Basement orthogneisses, paragneisses and migmatites in the Sierras de Cordoba of the eastern sierras Pampeanas of central Argentina represent remnants of a Cambrian arc and accretionary prism that initially formed above a subduction zone along the early Cambrian margin of Gondwana as mentioned in this paper.

TL;DR: In this article, the major and trace-element, Sr-Nd isotopes, and mineral chemistry data were obtained for a collection of volcanic rock samples erupted by Cay and Maca Quaternary volcanoes, Patagonian Andes (∼45°S, Chile).

TL;DR: In the late Neoproterozoic, high-K, mafic-intermediate rocks represent voluminous bimodal magmatism in the Borborema Province, northeast Brazil as mentioned in this paper.

TL;DR: In this paper, the authors present the results of multidisciplinary research in the Ecuadorian coastal regions, with particular emphasis on the Santa Elena Peninsula, and conclude that the unusual high faunal concentrations and the change to dense vegetation cover (due to a rapid increase in precipitation in the lower Holocene) at 8000-6000 ǫ bp, caused the final collapse and extinction of most elements of the mammal megafauna.

TL;DR: In the Neuquen-Mendoza volcanic province of Argentina, two samples associated with skarn mineralization in the Cerro Nevazon area, two were dated by K/Ar in amphibole and one by Ar in plagioclase; together, they yield ages between 601±16 and 560±17 Ma as discussed by the authors.

TL;DR: In this article, the dating of 47 spots in 42 zircon crystals from three rock samples using sensitive high-resolution ion microprobe (SHRIMP II) leads to a much better understanding of Paleoproterozoic magmatic participation in the construction of the Dom Feliciano Belt from the Precambrian shield of Santa Catarina, Brazil.

TL;DR: Lower Cretaceous volcanism in the Coastal Range (29°20′-30°S) of Chile is mainly represented by highly porphyritic (20-30% phenocrysts) lavas with unzoned Ca-rich plagioclase (An57-54Ab40-42Or3-4), clinopyroxene (Wo40En43Fs17), magnetite, and minor idiomorphic, altered olivines as discussed by the authors.

TL;DR: In this paper, the stratigraphic and geodynamic interpretation of Upper Jurassic lithostratigraphic units is revised in north-central Mexico and the northern rim of the Gulf of Mexico Basin through updated ammonite and calpionellid biochronostratigraphy.

TL;DR: The Mazatan Sierra is the southernmost metamorphic core complex (MCC) of the Tertiary extensional belt of the western Cordillera as mentioned in this paper, and its structural and lithological features are similar to those found in other MCC in Sonora and Arizona.

TL;DR: Petrographic and mineralogical studies of a 45 m thick basaltic lava flow in southern Parana Basin (Rio Grande do Sul, Brazil) enables a detailed description of three structural levels: the lower vesicular zone (LVZ), inner massive zone (IMZ), and upper Vesicular Zone (UVZ).

TL;DR: The Curitiba Basin, Parana, lies parallel to the west side of the Serra do Mar range and is part of a continental rift near the Atlantic coast of southeastern Brazil.

TL;DR: In this article, a new geologic information supports an interpretation of the initiation of tectonic uplift in the eastern margin of the Eastern Cordillera of Colombia and the onset of deformation across the northern Andes during the Late Eocene-Early Oligocene deformation.

TL;DR: In this paper, the authors examined the focal mechanisms located around the Scotia plate by fault population analysis to calculate both the trends of the maximum horizontal shortening on the plate and the orientations of its associated faults.

TL;DR: The Gaviao block in the northern portion of the Sao Francisco craton, northeast Brazil, is one of the oldest Archean fragments of the South American platform as mentioned in this paper, formed over'stable' continental crust.

TL;DR: The Lower Paleozoic Silgara Formation in the southwestern Santander Massif was affected by Caledonian regional metamorphism, which created a sequence of metamorphic zones (sillimanite, staurolite, garnet, and biotite) as discussed by the authors.

TL;DR: The rare earth element (REE) patterns are different from the post-Archean Australian average shale (PAAS) standard when the data are normalized, the pattern obtained shows that the bentonite is LREE depleted as mentioned in this paper.

TL;DR: In this article, the authors present 40Ar/39Ar age determinations and chemical and Sr-Nd isotopic data for the tholeiitic dyke swarm cropping out at Arraial do Cabo peninsula at the eastern end of the Rio de Janeiro coastline.