Orientador: George Luiz Luvizotto / Resumo: A formação das rias fluviais na Amazônia possui uma relação bem conhecida com o processo de avanço do nível do mar durante o Holoceno. Sugestões sobre a presença de controle estrutural e tectônico na gênese destas e de outros elementos do relevo amazônico tem sido levantadas por diversos autores, porém poucos elementos conclusivos foram apresentados até o momento. Este trabalho apresenta, no primeiro momento, uma série de evidências de diferentes fontes mostrando controle estrutural ao longo do ria do Tapajós e em áreas de terra firme adjacentes. A metodologia utilizada, é inovadora por integrar dados geomorfológicos, geológicos e geofísicos (sísmica, magnetometria e gravimetria) obtidos sem custo e disponíveis para grandes áreas, o que é uma grande vantagem em uma zona de difícil acesso como a Amazônia. Trata-se ainda de uma abordagem pouco usual dentro da geomorfologia na qual encontramos resultados muito promissores. Os resultados mostram a influência de elementos estruturais na configuração do relevo amazônico na região do baixo Tapajós. É proposto um modelo de horsts e grábens limitados por lineamentos com direção ENE-WSW com expressão regional. Em seguida apresentamos uma classificação para o canal do Tapajós baseado em variáveis morfométricas extraídas de perfil transversal. A classificação apresenta três trechos distintos para o canal do Tapajós no perímetro analisado, denominados Trecho do Canal Estreito, Baixo Trecho da Ria e Alto Trecho da Ria. Estes trechos possue... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The formation of the fluvial rias in the Amazon has a well-known relationship with the process of sea level transgression during the Holocene. Suggestions about the presence of structural and tectonic control in the genesis of these and other elements of the Amazonian relief have been raised by several authors, but few conclusive elements have been presented so far. This work presents, in the first moment, a series of evidences from different sources showing structural control along the Tapajós Ria and in adjacent land areas. The methodology used is innovative because it integrates geomorphological, geological and geophysical data (seismic, magnetometry and gravimetry) obtained at no cost and available for large areas, which is a great advantage in an area of difficult access such as the Amazon. It is also an unusual approach within geomorphology in which we find very promising results. The results show the influence of structural elements in the configuration of the Amazonian relief in the region of the lower Tapajós. A model of horsts and grabens limited by lineaments with regional expression is proposed. Next, we present a classification for the Tapajós channel based on morphometric variables extracted from transversal profiles. The classification presents three distinct sections for the Tapajós channel in the analyzed perimeter, here called Narrower Channel Reach, Lower Ria Reach and Higher Ria Reach. These reaches have statistical support and agreement with most of the s... (Complete abstract click electronic access below) / Doutor

O Planalto da Bocaina situa-se no flanco leste do Rift Continental do Sudeste do Brasil (RCSB), em uma das porções mais elevadas da Serra do Mar, com altitudes superiores a 2000 m, compondo, juntamente com o Planalto de Campos do Jordão, os altos blocos de planaltos cristalinos do sudeste do Brasil. A Bocaina apresenta uma sucessão de planaltos de relevo mais suavizado (planaltos isolados), separados por vales profundos, que perdem altura de NW para SE. A origem do desnivelamento desses planaltos tem sido associada ora à reativação de antigas zonas de cisalhamento por falhas com componente normal, ora à dissecação erosiva diferencial controlada por knickpoints, ou, ainda, à preservação de superfícies de erosão de idades diferentes. A presente pesquisa teve por finalidade analisar as diferentes hipóteses de modo a estabelecer a idade, estilo e magnitude dos eventos tectônicos e denudacionais, responsáveis pela atual distribuição dos planaltos isolados da Bocaina. A metodologia integra estudos geomorfológicos e estruturais, segundo uma abordagem morfotectônica, com apoio da análise de traços de fissão em apatita e determinações pelo método do radiocarbono. Esta análise constitui importante ferramenta para determinar histórias térmicas e idades de resfriamento, em escalas de tempo de 106 a 108 anos, e permite estimar taxas de denudação de blocos de embasamento. Modelos digitais de terreno e cartas morfométricas subsidiaram a análise morfotectônica. Os planaltos isolados são caracterizados por baixos valores de gradientes hidráulicos, declividade e amplitude do relevo. O condicionante tectônico no desnivelamento dos níveis topográficos e individualização desses planaltos é evidenciado pela estreita correlação entre estruturas rúpteis (falhas e fraturas), feições morfotectônicas (facetas triangulares, knickpoints, escarpas, capturas fluviais), distribuição dos principais alvéolos e padrão de drenagem. Diques registram fases distensivas desde a ruptura dos continentes no Eocretáceo até o Paleógeno. Regimes de esforços observados na Bocaina são compatíveis com o modelo tectônico proposto para o RCSB durante o Cenozóico. Os eventos tectono-magmáticos no sudeste do Brasil tiveram um importante papel nos processos denudacionais registrados pela análise de traços de fissão em apatitas no Planalto da Bocaina. As idades corrigidas de traços de fissão em apatitas para 15 amostras variam entre 326±30 e 54±5 Ma, incluindo um significativo conjunto de idades mais velhas do que 200 Ma - as mais antigas obtidas na região da Serra do Mar até o momento. As idades apresentam uma tendência de decréscimo de noroeste para sudeste, do interior do continente em direção à costa, padrão também reconhecido em outras margens continentais passivas. Esse padrão é perpendicular à direção estrutural principal do embasamento pré-cambriano, sugerindo um importante condicionante estrutural. Idades contrastantes em um mesmo planalto isolado, ou similares em altitudes diferentes, sugerem uma evolução tectonotermal regional complexa, possivelmente associada à evolução do RCSB. Um modelo simples de recuo de escarpa não explicaria a distribuição espacial das idades de traços de fissão em apatitas no Planalto da Bocaina; falhas devem ter sido responsáveis pela acentuação dos desníveis topográficos entre os planaltos isolados. As histórias térmicas registram importantes eventos de resfriamento relacionados à ruptura continental, ao magmatismo alcalino neocretáceo e à geração e deformação do RCSB. As idades mais antigas de traços de fissão da Serra do Mar foram obtidas nas porções mais elevadas da Bocaina, que guardam estreita semelhança com a paisagem dos altos campos no Planalto de Campos do Jordão, evidenciando que tais áreas provavelmente constituíram, por um longo período de tempo, importante área fonte de sedimentos para as bacias do Paraná, Bauru e Santos. / The Bocaina Plateau is situated on the eastern flank of the Continental Rift of Southeastern Brasil (CRSB), in the highest portions of the Serra do Mar, reaching more than 2000 meters in altitude. This and the Campos do Jordão Plateau comprise the high blocks of crystalline massifs of Southeastern Brasil. The Bocaina presents a succession of NW-SE topographically decreasing low-relief plateaus (isolated plateaus), separated by deep valleys. The origin of the differences in altitude among these plateaus has been associated with (1) tectonic reactivation of ancient shear zones by normal faulting, (2) differential erosional dissection controlled by knickpoints, and (3) preservation of erosional surfaces of different ages. This study examines these hypotheses in order to establish the age, style and magnitude of the tectonic and denudational events that resulted in the current distribution of the isolated plateaus of Bocaina. Structural and geomorphological analyses have been carried out using a morphotectonic approach, aided by apatite fission track analysis and radiocarbon dating. Apatite fission track analysis is an important tool to obtain thermal histories and cooling ages, on scales of 106 to 108 years, and is commonly used to estimate denudation rates in basement blocks. Morphotectonic analysis was supported by digital terrain models and morphometric maps. The isolated plateaus are characterized by low hydraulic gradient, slope and relief. Tectonic conditioning in the accentuation of differences in altitude and individualization of the plateaus is evinced by clear correlation between brittle structures (faults and fractures), morphotectonic features (triangular facets, knickpoints, scarps, fluvial captures), distribution of main alluvial plains and drainage pattern. Dikes indicate distensional phases since continental break-up in the Early Cretaceous till the Paleogene. Stress regimes observed in Bocaina are compatible with the tectonic model for the CRSB during the Cenozoic. Tectonic and magmatic events in Southeastern Brazil played an important role in denudational processes as recorded by apatite fission track analysis in the Bocaina plateau. Corrected fission track ages for 15 samples range from 326±30 to 54±5 Ma, including a significant set greater than 200 Ma, the oldest such ages yet registered in the Serra do Mar. Ages decrease NW-SE from the continent coastwards, a trend also recognized in other passive continental margins. This pattern is perpendicular to the main structural grain of the Precambrian basement, suggesting important structural control. Contrasting ages within a single plateau and similar ages at different altitudes indicate complex regional tectono-thermal evolution, possibly related to the evolution of the CRSB. Fission track age distribution in the Bocaina plateau cannot be explained by the simple scarp-retreat model; faults must have accentuated differences in altitude among the isolated plateaus. Thermal histories show important cooling events related to continental break-up, Early Cretaceous alkaline magmatism and origin of the CRSB. The oldest fission track ages obtained in the Serra do Mar region (> 200 Ma) were found in the highest portions of the Bocaina plateau, where the landscape system is very similar to that of the Campos do Jordão plateau. These areas have probably been an important, persistent source of sediments for the Paraná, Bauru and Santos basins, for a very long time.

O Planalto da Bocaina situa-se no flanco leste do Rift Continental do Sudeste do Brasil (RCSB), em uma das porções mais elevadas da Serra do Mar, com altitudes superiores a 2000 m, compondo, juntamente com o Planalto de Campos do Jordão, os altos blocos de planaltos cristalinos do sudeste do Brasil. A Bocaina apresenta uma sucessão de planaltos de relevo mais suavizado (planaltos isolados), separados por vales profundos, que perdem altura de NW para SE. A origem do desnivelamento desses planaltos tem sido associada ora à reativação de antigas zonas de cisalhamento por falhas com componente normal, ora à dissecação erosiva diferencial controlada por knickpoints, ou, ainda, à preservação de superfícies de erosão de idades diferentes. A presente pesquisa teve por finalidade analisar as diferentes hipóteses de modo a estabelecer a idade, estilo e magnitude dos eventos tectônicos e denudacionais, responsáveis pela atual distribuição dos planaltos isolados da Bocaina. A metodologia integra estudos geomorfológicos e estruturais, segundo uma abordagem morfotectônica, com apoio da análise de traços de fissão em apatita e determinações pelo método do radiocarbono. Esta análise constitui importante ferramenta para determinar histórias térmicas e idades de resfriamento, em escalas de tempo de 106 a 108 anos, e permite estimar taxas de denudação de blocos de embasamento. Modelos digitais de terreno e cartas morfométricas subsidiaram a análise morfotectônica. Os planaltos isolados são caracterizados por baixos valores de gradientes hidráulicos, declividade e amplitude do relevo. O condicionante tectônico no desnivelamento dos níveis topográficos e individualização desses planaltos é evidenciado pela estreita correlação entre estruturas rúpteis (falhas e fraturas), feições morfotectônicas (facetas triangulares, knickpoints, escarpas, capturas fluviais), distribuição dos principais alvéolos e padrão de drenagem. Diques registram fases distensivas desde a ruptura dos continentes no Eocretáceo até o Paleógeno. Regimes de esforços observados na Bocaina são compatíveis com o modelo tectônico proposto para o RCSB durante o Cenozóico. Os eventos tectono-magmáticos no sudeste do Brasil tiveram um importante papel nos processos denudacionais registrados pela análise de traços de fissão em apatitas no Planalto da Bocaina. As idades corrigidas de traços de fissão em apatitas para 15 amostras variam entre 326±30 e 54±5 Ma, incluindo um significativo conjunto de idades mais velhas do que 200 Ma - as mais antigas obtidas na região da Serra do Mar até o momento. As idades apresentam uma tendência de decréscimo de noroeste para sudeste, do interior do continente em direção à costa, padrão também reconhecido em outras margens continentais passivas. Esse padrão é perpendicular à direção estrutural principal do embasamento pré-cambriano, sugerindo um importante condicionante estrutural. Idades contrastantes em um mesmo planalto isolado, ou similares em altitudes diferentes, sugerem uma evolução tectonotermal regional complexa, possivelmente associada à evolução do RCSB. Um modelo simples de recuo de escarpa não explicaria a distribuição espacial das idades de traços de fissão em apatitas no Planalto da Bocaina; falhas devem ter sido responsáveis pela acentuação dos desníveis topográficos entre os planaltos isolados. As histórias térmicas registram importantes eventos de resfriamento relacionados à ruptura continental, ao magmatismo alcalino neocretáceo e à geração e deformação do RCSB. As idades mais antigas de traços de fissão da Serra do Mar foram obtidas nas porções mais elevadas da Bocaina, que guardam estreita semelhança com a paisagem dos altos campos no Planalto de Campos do Jordão, evidenciando que tais áreas provavelmente constituíram, por um longo período de tempo, importante área fonte de sedimentos para as bacias do Paraná, Bauru e Santos. / The Bocaina Plateau is situated on the eastern flank of the Continental Rift of Southeastern Brasil (CRSB), in the highest portions of the Serra do Mar, reaching more than 2000 meters in altitude. This and the Campos do Jordão Plateau comprise the high blocks of crystalline massifs of Southeastern Brasil. The Bocaina presents a succession of NW-SE topographically decreasing low-relief plateaus (isolated plateaus), separated by deep valleys. The origin of the differences in altitude among these plateaus has been associated with (1) tectonic reactivation of ancient shear zones by normal faulting, (2) differential erosional dissection controlled by knickpoints, and (3) preservation of erosional surfaces of different ages. This study examines these hypotheses in order to establish the age, style and magnitude of the tectonic and denudational events that resulted in the current distribution of the isolated plateaus of Bocaina. Structural and geomorphological analyses have been carried out using a morphotectonic approach, aided by apatite fission track analysis and radiocarbon dating. Apatite fission track analysis is an important tool to obtain thermal histories and cooling ages, on scales of 106 to 108 years, and is commonly used to estimate denudation rates in basement blocks. Morphotectonic analysis was supported by digital terrain models and morphometric maps. The isolated plateaus are characterized by low hydraulic gradient, slope and relief. Tectonic conditioning in the accentuation of differences in altitude and individualization of the plateaus is evinced by clear correlation between brittle structures (faults and fractures), morphotectonic features (triangular facets, knickpoints, scarps, fluvial captures), distribution of main alluvial plains and drainage pattern. Dikes indicate distensional phases since continental break-up in the Early Cretaceous till the Paleogene. Stress regimes observed in Bocaina are compatible with the tectonic model for the CRSB during the Cenozoic. Tectonic and magmatic events in Southeastern Brazil played an important role in denudational processes as recorded by apatite fission track analysis in the Bocaina plateau. Corrected fission track ages for 15 samples range from 326±30 to 54±5 Ma, including a significant set greater than 200 Ma, the oldest such ages yet registered in the Serra do Mar. Ages decrease NW-SE from the continent coastwards, a trend also recognized in other passive continental margins. This pattern is perpendicular to the main structural grain of the Precambrian basement, suggesting important structural control. Contrasting ages within a single plateau and similar ages at different altitudes indicate complex regional tectono-thermal evolution, possibly related to the evolution of the CRSB. Fission track age distribution in the Bocaina plateau cannot be explained by the simple scarp-retreat model; faults must have accentuated differences in altitude among the isolated plateaus. Thermal histories show important cooling events related to continental break-up, Early Cretaceous alkaline magmatism and origin of the CRSB. The oldest fission track ages obtained in the Serra do Mar region (> 200 Ma) were found in the highest portions of the Bocaina plateau, where the landscape system is very similar to that of the Campos do Jordão plateau. These areas have probably been an important, persistent source of sediments for the Paraná, Bauru and Santos basins, for a very long time.

Thesis (doctoral)--Freie Universität Berlin, 2002. / "January 2003"--P. [2] of cover. Lebenslauf. Includes bibliographical references (p. 137-142). Also available via the World Wide Web.

The Llano Uplift of central Texas contains the largest exposure of Mesoproterozoic rocks along southern Laurentia and is thus crucial to the understanding of orogenesis and plate reconstructions along a portion of one of the largest orogens in the world. Most of the current understanding of the Mesoproterozoic tectonic evolution of southern Laurentia comes from the southeastern portion of the Llano Uplift. To fully characterize the tectonic evolution Llano Uplift, detailed mapping is necessary in the less-studied western Llano Uplift. The Mesoproterozoic Llano Uplift exposes mid-crustal, poly-deformed and metamorphosed schists and gneisses and abundant pre- to post-tectonic granites through an erosional window of Phanerozoic sedimentary rocks. Three lithologic groups were mapped in the western Llano Uplift, from structural highest to lowest these are the Valley Spring Gneiss (VSG), Lost Creek Gneiss (LCG) and Packsaddle Schist (PS). The VSG consists of pelitic schists and pink quartzofeldspathic schists and gneisses. The LCG is a thick, homogeneous package of medium- to coarse-grained augen granite gneiss, interpreted to be a deformed, coarse-grained, porphyritic pluton. The PS consists of a heterogeneous package of interlayered quartzofeldspathic gneisses, amphibolites and minor marbles. These lithologies are consistent with the PS and VSG domains described in the southeastern Llano Uplift (Mosher, 1998; Reese et al., 2000). The exotic Coal Creek Domain (CCD) of the southeastern Llano Uplift is not observed in the western Llano Uplift. The western Llano Uplift, including the VSG, LCG and PS, records a deformational history that resulted in multiple fold generations (F1-F5) and is characterized by a penetrative axial planar foliation (S1-S5). F2s are isoclinal folds of S0 (primary layering) and S1 that locally fold F1 axial planes and have steeply plunging and generally easterly trending hinge lines. F3 folds are locally developed, nearly colinear and coplanar with F2s, tight to open, and fold all previous structures (F1/F2) and fabrics (S1/S2). F4s are open folds with northeast-trending axial traces that occur on a regional-scale. F5s are open to tight folds of all previous structures, with hinge lines that are primarily southeast trending and steeply plunging. S0 to S3 orientations vary from north to east dipping because of reorientation by younger folds. S4 foliations strike to the northeast and S5 foliations are northwest striking and nearly vertically dipping. Late left-lateral shear zones (D6) with generally an easterly trend and boudinage affects the VSG, LCG and VSG in this study area and is commonly associated with unfoliated granite material. Four generations of intrusive granitic sills and dikes are documented and provide relative and absolute age constraints on deformation. The oldest recognized deformation (D1-D3) is constrained between 1253 +5/-3 Ma and 1126 +5/-4 Ma (Roback, et al., 1999). D4 and D5 deformation are constrained between 1126 +5/-4 Ma and 1076 ± 5 Ma (Roback, et al., 1999). Although a change in metamorphic conditions is documented to have occurred between D2 and D3, metamorphic fabrics and assemblages indicate granulite facies conditions during D1, D2 and D3. Amphibolite facies metamorphism occurred during D4 and presumably D5. Deformation in the eastern Llano Uplift has a similar polyphase deformational history to that recorded here for the western Llano Uplift. Deformation in the eastern Llano Uplift is similarly constrained between ca. 1238 to 1091 Ma. In addition, the youngest fold generation (F5) can be directly correlated in orientation and timing from the western to the eastern Llano Uplift, and is constrained between ca. 1119 and 1091 Ma in the eastern uplift. Both the western and eastern Llano Uplift contain late shear zones and extensional structures. Structural differences between the western and eastern Llano Uplift include differences in style and orientation of all but the latest (D5 and D6) structures. In addition, dip of fabrics and, therefore, structural stacking of lithologic domains is opposite, and no mylonite zones were identified in the west. In conclusion, the lithologic domains appear to correlated across the Llano Uplift based upon gross lithologic similarities and the tectonic evolution is similar to the well-studied eastern Llano Uplift, though the kinematics and orientations differ. These conclusions may require that the kinematics of deformation in the southeastern uplift were controlled by the presence of the exotic island arc terrane (CCD) whereas the kinematics of deformation in the western uplift were controlled by continent-continent collision. / text

La chaîne Himalayenne est l'un des exemples les plus spectaculaires de déformation active à la surface de notre planète. Au cours des derniers siècles, de nombreux séismes majeurs (Mw > 7.5) ont affecté cette zone et le lourd bilan humain du séisme de Gorkha en 2015 a une nouvelle fois rappelé l’importance de parvenir à mieux estimer l’aléa sismique de cette région. Bien que les structures lithologiques et tectoniques semblent montrer au premier ordre une cylindricité le long des 2500 km de l'arc Himalayen, de nombreuses études, menées principalement au Népal, ont permis de mettre en évidence des variations latérales structurales, thermochronologiques, morphologiques, gravimétriques, sismologiques ou géodésiques. Le rôle de ces variations latérales sur la segmentation sismique reste cependant mal contraint. La taille maximale et la probabilité d’occurrence de ces méga-séismes sont donc toujours matière à débat.Ainsi, le comportement sismique de l’Himalaya du Bhoutan reste énigmatique. Pour certains les faibles taux de sismicité observés actuellement font de ce royaume une zone asismique de 350 km de long. Pour d’autres, à l’instar de l’Himalaya du Népal, la faible sismicité observée est associé à une forte accumulation de contrainte susceptible de générer des séismes majeurs. L'objectif de ce travail de thèse est d’améliorer notre connaissance de cette région en quantifiant la déformation à différentes échelles spatiales et temporelles via des études morphotectoniques et paléosismologiques.La première partie de cette thèse vise à quantifier les mouvements verticaux à l’ouest Bhutan et le long du Main Frontal Thrust, structure la plus frontale située au sud Bhoutan. Trois campagnes de terrain ont été réalisées permettant l'échantillonnage (1) de terrasses alluviales le long du front afin de quantifier et d'étudier les variations du soulèvement Holocène, (2) de bassins versants pour l'étude de la dénudation court-terme (< 20 ka) dérivée des cosmonucléides ($^{10}$Be) et (3) de terrasses alluviales dans le Moyen-Pays pour quantifier l’incision Holocène. Les vitesses verticales obtenues au front sont comparables à celle proposées le long du reste de l’arc himalayen, suggérant une cinématique relativement simple. Par contre, nos résultats indiquent une variation de la géométrie du chevauchement himalayen (Main Himalayan Thrust) entre l’est Népal et l’ouest Bhoutan.La seconde partie porte sur plusieurs études paléosismologiques le long du front ouest et centre Bhoutanais. Six sites différents ont été étudiés au cours de trois campagnes de terrain. La datation et la modélisation de charbons détritiques a permis de mettre en évidence l'occurrence d’au moins cinq séismes majeurs durant les derniers 2700 ans, faisant du Bhoutan une zone sismiquement aussi active que le Népal. A une échelle régionale, cette étude apporte donc de nouvelles contraintes et contribue au débat sur la possibilité d’occurrence d'un séisme de magnitude 9 le long de l'arc Himalayen. / The Himalayan arc is one of the most active intra-continental mountain belts in the world. Over the last centuries, several major earthquakes (Mw > 7.5) have struck this arc. The dramatic effects of the Gorkha earthquake sequence in 2015 pointed once again the crucial need to improve seismic hazard assessment of this area.Geological explorations of the Himalayas since the late 19th century have emphasized a 2500-km-long roughly cylindrical structure, with striking continuity of main units and thrust faults. However recent geophysical and geological investigations have revealed lateral variations. The relationship between these variations and earthquakes segmentation along the arc remains poorly constraint. The maximum size and the occurrence probability of such earthquakes are still a matter of debate.For instance, the seismic behavior of Bhutan remains enigmatic. The present-day low seismicity rate observed in this area can reflect two opposite fault behaviors: an aseismic creeping zone or a zone of stress accumulation for future great earthquakes as the others parts of Himalayas. The main objective of this thesis is to bring new constraints on the deformation of the Bhutan Himalayas, at different space- and time-scales, through morphotectonic and paleoseismological approaches.The first part of this thesis focuses on the vertical deformation assessment along a N-S transect in western Bhutan and along the Main Frontal Thrust, which is the southern-most thrust in southern Bhutan. In the past three years, we have carried out three fieldwork campaigns to sample (1) frontal terraces to assess Holocene uplift rates, (2) watershed basins to quantify short term denudation rates (< 20 ky) derived from cosmonuclides $^{10}$Be and (3) hinterland alluvial terraces to quantify the Holocene incision rate. Frontal Holocene uplift rates obtained in Bhutan are consistent with those obtained in the others parts of Himalayas. Furthermore, our results reveal a variation in the geometry of the Main Himalayan Thrust between eastern Nepal and western Bhutan.The second part focuses on several paleoseismic studies along the west and central bhutanese Himalayan front. Different sites were investigated during three fieldwork campaigns. Detritic charcoals sampling and modeling suggest the occurrence of at least five surface-rupturing earthquakes during the last ~2700 years. These results demonstrate that the present-day low seismicity rate observed in Bhutan is not representative of the seismic activity at longer time scale. At regional scale, they also take part of a broader discussion on the probability of occurrence of a magnitude 9 earthquake along the Himalayan arc.

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references. / This thesis investigates lithospheric dynamics of Earth's subduction zones and Martian tectonic provinces on multiple time scales ranging from short-term earthquake deformation to long-term tectonic loading. In Chapter 2, I use geodetic observations to constrain the postseismic viscoelastic deformation following the 1960 M9.5 Valdivia, Chile earthquake and quantify its stress loading on the rupture zone of the 2010 M8.8 Maule, Chile earthquake. Results of analysis reveal that the post-1960 viscoelastic process might have contributed to the triggering of the 2010 earthquake. Chapter 3 presents numerical experiments to investigate elastoplastic deformation and faulting in the overriding plates of subduction zones caused by the movement of subducted seamounts. Numerical simulations show that a group of normal faults would first appear on the seaward side of a subducted seamount, followed by a group of thrust faults on the landward side of the seamount. In Chapter 4, I use the most recent Martian gravity and topography data to constrain spatial variations in lithospheric flexural deformation for various tectonic regions on Mars. The effective lithospheric thickness is estimated to be relatively small for the plain regions in the southern highland, but relatively large for the impact basins in the northern lowland as well as for volcanic montes in the Tharis province. The regional variations in the estimated effective lithospheric thickness might reflect both spatial and temporal changes in the thermal state of Mars. / by Min Ding. / Ph. D.

Abstract not available

[Truncated abstract] Banded iron formations of the ~27702405 Ma Hamersley Province of Western Australia were locally upgraded to high-grade hematite ore during the Early Palaeoproterozoic by a combination of hypogene and supergene processes after the initial rise of atmospheric oxygen. Ore genesis was associated with the stratigraphic break between Lower and Upper Wyloo Groups of the Ashburton Province, and has been variously linked to the Ophthalmian orogeny, late-orogenic extensional collapse, and anorogenic continental extension. Small spot PbPb dating of in situ baddeleyite by SHRIMP (sensitive highresolution ion-microprobe) has resolved the ages of two key suites of mafic intrusions constraining for the first time the tectonic evolution of the Ashburton Province and the age and setting of iron-ore formation. Mafic sills dated at 2208 ± 10 Ma were folded during the Ophthalmian orogeny and then cut by the unconformity at the base of the Lower Wyloo Group. A mafic dyke swarm that intrudes the Lower Wyloo Group and has close genetic relationship to iron ore is 2008 ± 16 Ma, slightly younger than a new syneruptive 2031 ± 6 Ma zircon age for the Lower Wyloo Group. These new ages constrain the Ophthalmian orogeny to the period <2210 to >2030 Ma, before Lower Wyloo Group extension, sedimentation, and flood-basalt volcanism. The ~2010 Ma dykes present a new maximum age for iron-ore genesis and deposition of the Upper Wyloo Group, thereby linking ore genesis to a ~21002000 Ma period of continental extension similarly recorded by Palaeoproterozoic terrains worldwide well after the initial oxidation of the atmosphere at ~2320 Ma. The Lower Wyloo Group contains, in ascending order, the fluvial to shallow-marine Beasley River Quartzite, the predominantly subaqueously emplaced Cheela Springs flood basalt and the Wooly Dolomite, a shelf-ramp carbonate succession. Field observations point to high subsidence of the sequence, rather than the mainly subaerial to shallow marine depositional environment-interpretation described by earlier workers. Abundant hydro-volcanic breccias, including hyaloclastite, peperite and fluidal-clast breccia all indicate quench-fragmentation processes caused by interaction of lava with water, and support the mainly subaqueous emplacement of the flood basalt which is also indicated by interlayered BIF-like chert/mudstones and below-wave-base turbiditic mass-flows.

Η περιοχής της διατριβής βρίσκεται στη ΝΑ Στερεά Ελλάδα μεταξύ του συστήματος τάφρων-ζωνών, του Κορινθιακού και του Νότιου Ευβοϊκού Κόλπου και η κατανόηση της τεκτονικής εξέλιξής της κρίνεται ιδιαίτερα σημαντική για την κατανόηση της πιθανής αλληλεπίδρασής τους ή ακόμη και της σύνδεσης τους. Για να σκιαγραφηθεί αυτή η σχέση έγινε τεκτονική ανάλυση στη Λεκάνη Θηβών όπου αναγνωρίσθηκαν τέσσερις (4) κύριες ρηξιγενείς ζώνες με μήκη που κυμαίνονται από ~18 έως ~27 km. Κάθε μια από τις ρηξιγενείς ζώνες αποτελείται από επιμέρους κύρια ρήγματα. Αναλύθηκαν συνολικά 10 κύρια ρήγματα με μήκος που κυμαίνεται από ~7 έως ~15 km. Τα ρήγματα και οι αντίστοιχες ρηξιγενείς ζώνες, που αυτά συνθέτουν, αποτελούν, κατά την εξέλιξη της Λεκάνης Θηβών, περιθώρια επιμέρους λεκανών. Η διατριβή συνεισφέρει στην κατανόηση της τεκτονικής εξέλιξής της περιοχής μελέτης, η οποία κρίνεται ιδιαίτερα σημαντική για την κατανόηση της πιθανής αλληλεπίδρασής των γειτονικών ρηξιγενών ζωνών, ή ακόμη και της σύνδεσης τους. Στόχοι της διατριβής αποτέλεσαν: (1) η αναγνώριση και λεπτομερής χαρτογράφηση των κύριων ρηξιγενών ζωνών της Λεκάνης Θηβών και η σύνδεσή τους με τις τεκτονικές και σεισμολογικές παρατηρήσεις στην περιοχή της ΝΑ Στερεάς Ελλάδας, (2) η κατανόηση του τρόπου σύνδεσης και εξέλιξης των ρηγμάτων, (3) η εκτίμηση του «βαθμού ενεργότητας» των ρηξιγενών δομών, και (4) η κατανόηση του ρόλου της ενεργού τεκτονικής στην εξέλιξη του αναγλύφου της περιοχής μελέτης. Οι σεισμοί, ως φυσικό φαινόμενο, έχουν την δυνατότητα να προκαλούν εκτεταμένες υλικές καταστροφές και πολλές φορές και την απώλεια ανθρώπινων ζωών, επιδρούν κατά κανόνα αρνητικά στην πρόοδο της οργανωμένης κοινωνίας. Συνεπώς, ο καθορισμός των ενεργών τεκτονικών διεργασιών είναι σημαντικός για την κατασκευή μεγάλων τεχνικών έργων αλλά και για τη σχεδίαση της αντισεισμικής πολιτικής μιας περιοχής ή μιας χώρας. Το βασικό ‘’εργαλείο’’ της παρούσας μελέτης αποτέλεσε ένα ευρύ φάσμα ‘’τεχνικών’’ της Ενεργού Τεκτονικής και της Τεκτονικής Γεωμορφολογίας. Η ποσοτική μορφοτεκτονική ανάλυση των ρηξιγενών ζωνών με τη χρήση μορφομετρικών δεικτών, επιτρέπει τόσο την ακριβή χαρτογράφηση και ανάλυση των ρηγμάτων όσο και την εκτίμηση του ‘’βαθμού ενεργότητάς’’ τους. Τα όρια των ρηγμάτων και οι ζώνες μεταβίβασης που αναπτύσσονται μεταξύ των ρηγμάτων στις ρηξιγενής ζώνες αναλύθηκαν με την κατασκευή διαγραμμάτων κατανομής της μετατόπισης. Η διερεύνηση της σχέσης μεταξύ της μετατόπισης του ρήγματος με το επιφανειακό του μήκος, βοηθάει στην κατανόηση του τρόπου με τον οποίο αναπτύσσονται τα ρήγματα και των κλασματικών ιδιοτήτων της μετατόπισης σε σχέση με το μήκος. Επιπρόσθετα, η διερεύνηση της σχέσης μεταξύ αναγλύφου και λεκανών απορροής στη βάση των ρηξιγενών ζωνών, αποτελεί ένα ακόμα ‘’βήμα’’ για την κατανόηση της εξέλιξης του αναγλύφου των ρηξιγενών ορεογραφικών μετώπων. Τα νεοτεκτονικά στοιχεία που συλλέχθηκαν συμπληρώθηκαν με την εκσκαφή παλαιοσεισμολογικών τομών και την εφαρμογή μεθόδων και αρχών της Παλαιοσεισμολογίας και οδήγησαν στη διερεύνηση της σεισμικής ιστορίας του Ρήγματος Καπαρέλλιου, με γεωλογικές μεθόδους, ώστε να εκφράζεται αυτή με όρους ανάλογους της σεισμολογίας. Η χρήση των Γεωγραφικών Συστημάτων Πληροφοριών (G.I.S) αποτέλεσε ένα ‘’δυναμικό εργαλείο’’ συλλογής, διαχείρισης και απεικόνισης χωρικών δεδομένων που προέκυψαν από την εφαρμογή των παραπάνω μεθόδων στην περιοχή μελέτης. Η ποιοτική και ποσοτική ανάλυση του υδρογραφικού δικτύου της περιοχής μελέτης, έδειξε ότι η εξέλιξη των λεκανών απορροής επηρεάζεται σημαντικά από τη δράση των επιμέρους ρηξιγενών ζωνών, και σε μικρότερο βαθμό και από τις τοπικές γεωλογικές και υδρογεωλογικές συνθήκες της περιοχής. Ο υπολογισμός της ασυμμετρίας των κύριων λεκανών απορροής της περιοχής μελέτης υπολογίσθηκε με το Συντελεστή Ασυμμετρίας (Αf) και το Συντελεστή Εγκάρσιας Τοπογραφικής Συμμετρίας (Τ). Κατά μήκος των ρηξιγενών ζωνών υπολογίσθηκαν οι μορφοτεκτονικοί δείκτες: δείκτης ευθυγράμμισης ορεογραφικού μετώπου (Smf), δείκτης λόγου πλάτους κοιλάδας προς ύψος κοιλάδας (Vf), δείκτης σχήματος λεκάνης απορροής (Bs) και δείκτης μήκους-κλίσης ρέματος (SL). Οι τιμές των μορφοτεκτονικών δεικτών καταδεικνύουν ότι όλες οι ρηξιγενείς ζώνες είναι ενεργές και υπόκεινται σε υψηλό ρυθμό ανύψωσης σύμφωνα με τα διεθνώς παραδεκτά δεδομένα. Η ανάλυση με μεθόδους της Τεκτονικής Γεωμορφολογίας, που πραγματοποιήθηκε στις τέσσερις ρηξιγενής ζώνες της περιοχής μελέτης, οδηγεί στο συμπέρασμα ότι όλες οι ζώνες μπορούν να χαρακτηρισθούν σαν υψηλής ενεργότητας. Από την ανάλυση των αποτελεσμάτων των παλαιοσεισμολογικών τομών διαπιστώθηκε ότι το Βόρειο Ρήγμα Καπαρελλίου παρουσιάζει συνεχή τεκτονική δραστηριότητα. Σε μια περιοχή όπως ο ευρύτερος Αιγιακός χώρος, η μελέτη του αναγλύφου με τη χρήση μορφοτεκτονικών παραμέτρων μπορεί να αποτελέσει οδηγό για την κατανόηση των επιφανειακών επιπτώσεων των σεισμών επί του ανάγλυφου. / The study area is located in the easternmost sector of the Gulf of Corinth, the Beotia area in SE Central Greece, which is an area with active normal faults located between two major rift structures of Central Greece, the Gulf of Corinth and the South Gulf of Evia. The Gulf of Corinth is an active rift with high rates of uplift and high seismicity, on the contrary the South Gulf of Evia is an area with low rates of uplift, compared with the Gulf of Corinth, moderate seismicity but with strong seismic events. The research is focused on four fault zones, which are described from west to east: the Neochori-Leontari, the Livadostras-Kaparelli, the Erithres-Dafnes and the Kallithea-Asopia fault zones with lengths from ~18 km to ~27 km. Each one of the fault zones consist from a number of discrete main faults with lengths ranging from ~7 to ~15 km. The purpose of this study is to analyze the drainage pattern and landscape evolution in order to evaluate the tectonic activity and the fault growth within the actively deformed easternmost sector of the Gulf of Corinth. In order to achieve this aim, a variety of morphotectonic parameters is used additionally with detailed mapping of faults to refine geometry and evolution of fault systems in the study area. In addition, we used G.I.S. techniques to estimate the morphotectonic parameters. In addition, three palaeoseismological trenches were excavated across the Kaparelli fault scarp, in order to understand the seismic history of the Kaparelli normal fault that ruptured during the March 1981 Gulf of Corinth earthquakes. All faults or fault zones analyzed in this study control a basin and range topography accommodating the current extension in the South Sterea Hellas region. These faults follow two trends: ENE to NE and WNW to E-W. The former fault system prevails in western Greece, with Rio Graben as a typical structure controlled by these faults. In eastern Peloponnese and south Sterea Hellas this fault system appears to be weaker. The Livadostras, Neochori and Dafnes faults belong to this fault trend. The WNW to E-W trending faults control a series of typical grabens, like the Gulf of Corinth, Tithorea, Sperchios-Atalanti as well as the Thiva graben. The Kaparelli, Leontari, Tanagra, Kallithea, Asopia, Kirikion and Erithres faults belong to this fault trend. All mentioned faults are organized in fault zones. It is also commonly observed that faults belonging to the two fault trends show a physical or mechanical linkage and thus in the same fault zone both fault trends are included. The results of this study shows that vertical motions and tilting associated with normal faulting influence the drainage geometry and its development. Values of stream-gradient indices (SL) are relatively high close to the fault traces of the studied fault zones suggesting high activity. Mountain-front sinuosity (Smf) mean values along the fault zones ranges from 1.08 to 1.26. Valley floor width to valley height ratios (Vf) mean values along the studied fault zones range between 0.5 and 1.6. Drainage basin shape (BS) mean values along the fault zones range from 1.87 to 3.54. Drainage density (Dd) mean values along the studied fault zones range from 1.56 to 5.65. All these morphotectonic parameters and geomorphological data suggest that the analyzed normal faults are highly active. Although fault zones controlling the Thiva Basin show lateral growth both westwards and eastwards, in several cases the tendency for eastward lateral growth is more predominant. The analyzed trenches expose evidence of at least three events, for the past 10,000 years, with the 1981 event included. Displacements per event on different fault segments within the trenches vary between 0.7 and 1 m. Average vertical displacements associated with interpreted paleoearthquakes at the trench site are in the order of 2.7 m. Average slip rates derived from the trenches is in the order of c. 0,3 mm/yr.