Geólogo / Las causas de los pulsos orogénicos de la cadena andina durante el Cenozoico, son aún un enigma, distintos autores han postulado que estos eventos, o fases compresivas, estarían gatillados por los cambios en el vector de velocidad de convergencia entre la placa oceánica subductante y la placa Sudaméricana, el movimiento hacia el oeste de Sudamérica por el centro de expansión Atlántico, o corrientes astenosféricas. Sin embargo, muchos modelos, numéricos y análogos, muestran que estos procesos, por sí solos, no explicarían el momento ni el rango latitudinal en que ocurren estos sucesos. Por otro lado, la placa oceánica que subduce bajo Sudamérica, no es homogénea, posee una compleja batimetría consistente en cadenas de montes submarinos, zonas de fracturas, plateaus oceánicos y centros de expansión activos e inactivos, estos rasgos batimétricos afectan hoy en día la tectónica del margen continental, produciendo mayor sismicidad en la zona del margen y hacia el interior del continente donde se le atribuyen sismos más profundos, como también la somerización de la placa subductante. Por lo que el esfuerzo que produce la subducción de estos elementos, afectaría la corteza continental con mayores tasas de deformación. El objetivo de esta memoria es generar un modelo de reconstrucción tectónica, que sea coherente con los rasgos batimétricos, la fábrica del suelo oceánico y las anomalías magnéticas, en las Placas Pacífico y Nazca, que pueda constreñir el tiempo y la latitud donde estos rasgos batimétricos llegaron a interactuar con el margen sudamericano, y así observar la relación espacio-temporal entre el arribo de estos rasgos batimétricos al margen de subducción, y las fases orogénicas que dieron origen a la Cordillera de los Andes durante el Cenozoico.

Made available in DSpace on 2015-02-24T19:48:42Z (GMT). No. of bitstreams: 1 ElissandraML_TESE.pdf: 4127116 bytes, checksum: 96a227a009bb7f315ba51270ad826be9 (MD5) Previous issue date: 2011-02-08 / The study of Brazilian sedimentary basins concentrates on their rift phase, whereas the Post-rift phase has been considered a tectonic quiescent period. The post-rift sequence of the Potiguar Basin, in the far northeastern Brazil, was once considered little deformed, however several studies have shown how that it was affected by major fault systems. The purpose of this thesis is to characterize the post-rift tectonic. The specific objectives are: to characterize the Neogene and Quaternary sedimentary units that outcrop of the Potiguar Basin; to show how the NW-SEtrending Afonso Bezerra Faults System deformed outcrop rocks in the Basin; to describe soft-sediment deformation in gravels of the Quaternary Alluvial Deposits from A?u River. Facies analyses, grain-size studies, luminescence dating, remote sensing, structural mapping, shallow geophysics (georadar), paleostress and petrography were carried out. The structural mapping and the georadar sections indicated that the Carnaubais and Afonso Bezerra fault systems formed fractures, silicified and non-silicified faults or deformation bands, affecting mainly the A?u, Janda?ra and Barreiras formations. The petrographic data indicate that the strong silicification resulted in a sealant character of the faults. Paleostress analysis indicates that two stress fields affected the Basin: the first presented N-S-trending compression, occurred from the Neocretaceous to the Miocene; the second stress field presents E-W-trending compression, acts from the Miocene to the present. It was verified once the Afonso Bezerra System Faults was reactivated in periods post-Campanian and affects all post-rift lithostratigraphic units of Potiguar Basin, including Quaternary sedimentary covers. The study about soft-sediment deformation structures indicates that they are similar in morphology and size to modern examples of seismically-induced deformation strutures in coarse sediments. TL and OSL ages indicate that sediment deposition and associated soft-sediment deformation occurred at least six times from ~352 Ka to ~9 Ka. Finally these studies demonstrate how recent is tectonics in the Basin Potiguar / Os estudos sobre as bacias sedimentares brasileiras se concentram em sua fase rifte, enquanto a fase p?s-rifte tem sido considerada um per?odo de pouca atividade. A sequ?ncia p?s-rifte da Bacia Potiguar, no extremo nordeste brasileiro, j? foi considerada pouco deformada, contudo, in?meros trabalhos v?m demonstrando como ela ? afetada por importantes sistemas de falhas. A finalidade geral desta tese ? caracterizar a tect?nica p?s-rifte na Bacia Potiguar. Os objetivos espec?ficos s?o: caracterizar as unidades sedimentares cenozoicas aflorantes e a tect?nica associada; evidenciar como o Sistema de Falhas de Afonso Bezerra deformou rochas aflorantes da Bacia; descrever deforma??o em sedimentos inconsolidados nos conglomerados dos Dep?sitos Aluviais quatern?rios do Rio A?u. An?lises de f?cies, estudos granulom?tricos, data??o por luminesc?ncia, sensoriamento remoto, mapeamento estrutural, geof?sica rasa (georadar), an?lises de paleotens?es e petrografia foram realizados. O mapeamento estrutural e as sec??es de georadar indicaram que os sistemas de falhas Carnaubais e Afonso Bezerra formaram juntas, falhas silicificadas e n?o-silicificadas e bandas de deforma??o, afetando principalmente as forma??es A?u, Janda?ra e Barreiras. Os dados petrogr?ficos indicam que a forte silicifica??o deu ?s falhas um car?ter selante. O estudo de paleotens?es indica dois campos de tens?es afetando a Bacia: o primeiro, com compress?o N-S, atuou do Neocret?ceo ao Mioceno; o segundo, com compress?o E-W, atua do Mioceno ao presente. Constatou-se que o Sistema de Falhas de Afonso Bezerra foi reativado em per?odos p?s-campanianos e afeta todas as unidades litoestratigr?ficas p?s-rifte da Bacia Potiguar, inclusive as coberturas quatern?rias. O estudo sobre deforma??o em sedimentos inconsolidados indica que esta ? similar na morfologia e no tamanho aos exemplos modernos de estruturas de deforma??o sismicamente induzida em sedimentos grossos. Idades por TL e LOE indicam que a deposi??o dos sedimentos e a deforma??o associada ocorreram pelo menos em seis eventos entre aproximadamente 352 Ka e 9 Ka. Enfim estes estudos demonstram qu?o recente ? a tect?nica na Bacia Potiguar

Made available in DSpace on 2015-03-13T17:08:16Z (GMT). No. of bitstreams: 1 SilvanaDSB_ate o cap3.pdf: 2368599 bytes, checksum: 4c29280234b51f854200d0bf377f8c62 (MD5) Previous issue date: 1998-08-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / A morpho-structural analysis was performed in the uplifted siliciclastic deposits of the Serra do Martins Formation along the Portalegre, Martins and Santana plateaux, in the southeastern and central regions of Rio Grande do Norte State. Due to the lack of biostratigraphic records, this formation has a disputable age.The adopted approach was based on the analysis of the drainage patterns and in the recognition of topographic surfaces and regional structures, subjected to neotectonic deformation and rejuvenation the present stress field. These events are recorded in the lineament arrays and as anomalous features of the landscape, such as the uplifted plateaux.The morpho-sculptural evolution of the studied blocks is expressed as erosive and accumulative processes. The former ones include erosional scarpments, cuestas and amphitheaters as the most characteristic features, while debris slopes represent acumulative examples. Such elements attest to the recent disequilibrium of the plateaux, and the absence of well developed alluvium terraces suggest an accelerated uplift process. The directions of the linear features observed in remote sensing products evidence the control of the basement structural trends, inherited from the pre-Cenozoic evolution. The NNE-SSW direction controls the main erosional features of the plateaux, while the N-S direction is a major drainage control, being also recognized in the Potiguar Basin. An E-W trend occurs as a less developed direction, reflecting either a system of mesozoic basic dykes or precambrian brittle structures. As regards to the drainage arrays, an arborescent, varying to a roughly N-S rectangular pattern, was identified in the Portalegre-Martins block. The Santana plateau displays rectilinear (northern border) and dendritic arborescent (southern border) patterns. In the sedimentary cover, the drainage pattern varies from rectangular to angular, reflecting inheritance from the crystaline basement. The most significative directions, N, NE and NW, mark the erosional fronts of the plateaux. Drainage anomalies, characterized by elbows or paralell confluencies, reinforce the arguments mentioned above. The data sets evidence the relationships between endogenous (lithology, structures) and exogenous features as the main controls of terrain dissecation, associated to vertical (epirogenesis) movements and horizontal tectonics. A final discussion addresses the relationships of the Serra do Martins Formation with the sedimentary record of Potiguar Basin, trying to establish chronostratigraphic links with the main evolutionary steps of this part of the Borborema Province, and possible mechanisms involved in the uplift of the plateaux and other stratigraphic units in the region / A an?lise morfo-tect?nica aqui apresentada teve por objetivo estudar os dep?sitos silicicl?sticos soerguidos da Forma??o Serra do Martins, no contexto dos plat?s de Portalegre, Martins e Santana, situados nas por??es sudoeste e central do Estado do Rio Grande do Norte. A referida forma??o tem idade discut?vel, por n?o apresentar registros crono e/ou bioestratigr?ficos que a posicionem temporalmente. A sistem?tica de investiga??o adotada fundamentou-se na an?lise da rede de drenagem, no reconhecimento de superf?cies topogr?ficas e das estruturas regionais, submetidas a eventos e reativa??es neotect?nicas. Estes aspectos t?m reflexo direto no arranjo dos lineamentos e em fei??es an?malas identificadas na paisagem, p. ex., os plat?s soerguidos. A evolu??o morfo-escultural dos blocos estudados est? expressa atrav?s de processos erosivos e acumulativos. Dentre as fei??es dissecativas as escarpas de eros?o, cuestas e anfiteatros s?o as mais caracter?sticas, enquanto que os debris slopes constituem um exemplo acumulativo marcante. Estes elementos marcam o desequil?brio recente dos plat?s, onde a aus?ncia de expressivos terra?os aluvionares reflete um processo de r?pido soerguimento. As dire??es das fei??es lineares observadas nos produtos de sensoriamento remoto evidenciam o controle dos trends estruturais do embasamento, herdados da evolu??o pr?-Cenoz?ica. A orienta??o NNE-SSW controla fei??es erosionais dos plat?s, e o trend N-S condiciona o arranjo da drenagem, sendo tamb?m reconhecido na Bacia Potiguar. O trend E-W ocorre de forma menos intensa, refletindo o sistema de diques b?sicos mesoz?icos ou estruturas fr?geis precambrianas. No tocante ao arranjo da drenagem, o padr?o arborescente com varia??es para retangular com dire??o geral para norte foi identificado no bloco Portalegre-Martins. O plat? de Santana ordena-se em padr?es retil?neo (borda norte) e dendr?tico arborescente (sul). Na cobertura sedimentar o arranjo varia de retangular a angular, refletindo o arcabou?o herdado do embasamento cristalino. As dire??es mais significativas s?o N, NE e NW, marcando os trends erosivos. As anomalias de drenagem caracterizadas por deflex?es em cotovelo ou conflu?ncias em arranjo paralelo refor?am os argumentos acima expostos. Os estudos evidenciam a rela??o dos fatores end?genos (litologia, fei??es estruturais) em combina??o aos ex?genos, como condicionantes do maior ou menor grau de disseca??o do relevo, associados aos movimentos verticais (epirog?nese) e ? tect?nica horizontal. S?o discutidas as v?rias possibilidades de correla??o da Forma??o Serra do Martins com os sedimentos encontrados na Bacia Potiguar emersa, objetivando estabelecer poss?veis conex?es crono-estratigr?ficas com os v?rios epis?dios evolutivos desta por??o da Prov?ncia Borborema, e os prov?veis mecanismos envolvidos no soerguimento destes plat?s e de outras unidades estratigr?ficas regionais

Geólogo / El presente es un estudio sobre las rocas sedimentarias cenozoicas expuestas al sur de Balmaceda (46°S), denominadas Formación Oscuro, asignadas al Mioceno inferior medio. Se hizo un levantamiento estratigráfico de nueve secciones, abarcando una potencia aproximada de 1000 m. De acuerdo a las litologías observadas, se reconocen cuatro unidades en esta formación. Dos unidades inferiores, que tienen una composición volcaniclástica y se interpretan como depositadas en la parte distal de sistemas aluviales, separados entre sí por una paraconcordancia entre el Eoceno superior Mioceno inferior. Le sobreyacen en discordancia erosiva, dos unidades superiores de composición epiclástica y volcaniclástica, asociadas a la reactivación de sistemas fluviales trenzados y sinuosos durante el Mioceno medio. Se propone un nuevo esquema estratigráfico para estas unidades, abandonando el nombre de Formación Oscuro y agrupando estas unidades en tres formaciones: la unidad volcaniclástica inferior se define como Formación Estancia La Frontera (Eoceno inferior), la unidad volcaniclástica superior podría corresponder a la Formación Río Frías (Mioceno inferior), mientras que las dos unidades epiclásticas/volcaniclásticas superiores se agrupan dentro de la Formación El Portezuelo (Mioceno medio). Estas serían correlativas con las unidades argentinas aflorantes en la meseta del Guenguel y meseta del Chalía. El contraste en los ambientes sedimentarios observado en estas unidades se relaciona con los eventos de subducción de dorsales activas en el margen occidental de Sudamérica durante el Cenozoico. El primero tuvo lugar durante el Eoceno (Dorsal Farallón-Aluk) y el segundo desde el Mioceno hasta el presente (Dorsal de Chile). Esto ha provocado variaciones en el aporte sedimentario y la acomodación, regulando la sedimentación en el antepaís oriental de la Cordillera Patagónica.

A l’échelle continentale, la Cordillère des Andes présente d’importantes courbures. Une des plus importantes est la Courbure de la Patagonie, où le cours de l’orogène et de ses principales provinces tectoniques pivotent de près de 90°, passant d’une orientation N-S à 50°C à une orientation E-O en Terre de Feu. Malgré son importance, l’origine de la Courbure de la Patagonie et son implication dans les reconstructions paléogéographiques demeurent sujet à controverse: est-elle le résultat d’un plissement oroclinal, ou bien une caractéristique héritée? C’est dans ce contexte que j’ai réalisé une étude paléomagnétique et de susceptibilité d'anisotropie magnétique dans la région des Andes Australes. Les résultats obtenus suggèrent que la partie intérieure de cette courbure soit une caractéristique secondaire liée à l’évolution de la Péninsule Antarctique. / At the continental scale, the Andes presents significant curvatures. One of the largest is the curvature of Patagonia, where the orogen and its main tectonic provinces are rotated about 90 ° from an NS direction at 50 ° to an EO orientation in Tierra del Fuego. Despite its importance, the origin of the curvature of Patagonia and its involvement in paleogeographic reconstructions remain controversial: is the result of an oroclinal bending, or an inherited characteristic? It is in this context that I made a paleomagnetic and magnetic susceptibility anisotropy in the Austral Andes region. The results suggest that the inner part of the bend is a secondary feature linked to the evolution of the Antarctic Peninsula.In this thesis, I will present the results of a paleomagnetic and anisotropy of magnetic susceptibility (AMS) study of 146 sites sampled between 50 ° S and 55.5 ° S (85 sites in marine sedimentary rocks of the Cretaceous-Miocene of the Magallanes fold and thrust belt; 20 sites in sedimentary and volcanic rocks south of Cordillera Darwin, 41 sites in intrusive rocks of the Cretaceous-Eocene batholith. The AMS results in the sediments show that the magnetic fabric is controlled by tectonic processes, partially or completely obliterating the sedimentary fabric. In general, there is a good correlation between the orientation of the magnetic lineation and that of the fold axes except at Peninsula Brunswick. The wide variation in the orientation of magnetic fabrics within the batholith suggests an emplacement of intrusive without tectonic constraint. Paleomagnetic results obtained in Navarino Island and Hardy Peninsula, south of the Beagle Channel, show a post-tectonic remagnetization recording a counterclockwise rotation of more than 90 ° as that recorded by the intrusive rocks older than ~ 90Ma. The Upper Cretaceous to Eocene intrusive rocks record counterclockwise rotations of lower magnitude (45 ° -30 °). In contrast, the Magallanes fold and thrust belt mainly developed between the Eocene and Oligocene records little or no rotation. Spatial and temporal variations of tectonic rotations determined in this study support a model of deformation of the Austral Andes in two steps. The first step corresponds to the rotation of a volcanic arc by closing a marginal basin (the Rocas Verdes basin) and formation of Cordillera Darwin. During the propagation of deformation in the foreland, the curvature acquired by the Pacific border of the Austral Andes is accentuated by about 30 °. The tectonic reconstructions using the most recent Global Plate Tectonic model show the essential role of the convergence between the Antarctic Peninsula and South America in the formation of Patagonian orocline during the Late Cretaceous to the Eocene.