Die Antarktis ist eine Schlüsselregion für die Entwicklung des Klimageschehens auf der Erde. Globale Satellitennavigationssysteme (GNSS) helfen dabei, die damit verbundenen geodynamischen Prozesse besser zu verstehen, indem mit wiederholten oder kontinuierlichen Messungen präzise Deformationsraten der festen Erde abgeleitet werden. Neben der Bestimmung von plattentektonischen Bewegungen zählt in den Polargebieten insbesondere die Erfassung des glazial-isostatischen Ausgleichs (GIA) zu den wichtigsten Anwendungsbereichen von GNSS. GIA beschreibt die Reaktion der festen Erde auf sich verändernde Eisauflasten und äußert sich in einer an der Erdoberfläche messbaren Deformation, welche größtenteils durch Umverteilungen des zähflüssigen Mantelmaterials innerhalb der Erde verursacht wird. Die mittels Satellitengravimetrie bestimmten Eismassenbilanzen, welche etwa bei Klimamodellierungen verwendet werden können, weisen große Fehlereinflüsse durch die Unsicherheiten der GIA-bedingten Massenumverlagerungen auf. Deshalb sind die GNSS-Ergebnisse für die Validierung der GIA-Modelle und darauf basierende Untersuchungen von großer Bedeutung. In der hier vorliegenden Arbeit wurde eine konsistente Prozessierung von allen verfügbaren, in der Antarktis auf Fels gemessenen GNSS-Daten durchgeführt. Die Daten wurden im Rahmen der internationalen Kooperation GIANT-REGAIN (Geodynamics In ANTarctica based on REprocessing GNSS dAta INitiative) zur Verfügung gestellt und die Ergebnisse dieser Arbeit stellen zugleich einen Beitrag dazu dar. Ein großes Problem der bisherigen GNSS-Untersuchungen der Antarktis war der beschränkte Umfang, sei es in Folge einer regionalen Analyse oder durch eine eingeschränkte Auswahl an GNSS-Stationen bei Auswertungen im kontinentalen oder globalen Maßstab. Einige wichtige Regionen wurden zudem nur sehr selten berücksichtigt, etwa die durch extreme Eismassenverluste gekennzeichnete Amundsensee-Region. Die verschiedenen GNSS-Untersuchungen verwendeten unterschiedliche Auswertestrategien, Eingangsmodelle und Referenzrahmen, weshalb sich die Raten nicht direkt miteinander vergleichen lassen. Eine Validierung der GIA-Modelle ist daher in den meisten Fällen nur eingeschränkt möglich. Mit der hier durchgeführten gemeinsamen Prozessierung von mehr als 250 GNSS-Stationen für den Zeitraum von 1995 bis 2017 konnten die bisherigen Limitierungen umgangen werden. Für fast alle Stationen ließen sich Deformationsraten bestimmen, welche einer einheitlichen Auswertung entstammen und sich daher direkt vergleichen und interpretieren lassen. Neben der Prozessierung der GNSS-Daten lag ein Fokus auch auf den dazugehörigen Metadaten. Deren korrekte oder unzureichende Erfassung kann einen signifikanten Einfluss auf die abgeleiteten Deformationsraten haben. Durch den Aufbau eines Datenmanagementsystems mit mehreren graphischen Schnittstellen wurde die Datenverwaltung deutlich effizienter gestaltet. Außerdem ließen sich damit viele Fehler detektieren und größtenteils beheben. Weitere Untersuchungsschwerpunkte waren die Optimierung der Realisierung des geodätischen Datums durch Anpassung der Datumsstationsauswahl, die Detektion von Ausreißern und Sprüngen in den Zeitreihen für eine zuverlässige Trendschätzung sowie die Behandlung offensichtlicher Probleme einiger Stationen. Zu den auffälligsten Problemen zählen die Auswirkungen von fehlerhaften Metadaten und von Eisablagerungen innerhalb der Antenne. In diesem Zusammenhang zeigte sich auch, dass automatisierte Verfahren zur Detektion von Ausreißern und Sprüngen sowie robuste Verfahren gegenüber diesen Anomalien für viele Stationen sehr gute Resultate liefern. Es gibt aber auch mehrere Stationen mit einer besonderen Charakteristik, für die eine manuelle Nachbearbeitung dringend anzuraten ist. Insbesondere die Eisablagerungen in den Antennen, welche bisher noch nicht genauer untersucht wurden, können von diesen Verfahren nicht adäquat berücksichtigt werden. Weiterhin wurden im Rahmen einer sorgfältigen Genauigkeitsabschätzung realistische Maße für die Unsicherheiten der GNSS-Deformationsraten abgeleitet. Die mit GNSS ermittelten Deformationsraten der Antarktis wurden im geodynamischen Kontext betrachtet. In der Ostantarktis fallen die vertikalen Deformationsraten sehr gering aus und umfassen nur wenige Millimeter pro Jahr, wobei das Vorzeichen häufig wechselt. Dagegen sind die vertikalen Deformationsraten in der Westantarktis deutlich größer und können mehrere Millimeter pro Jahr betragen. Eine Sonderstellung nehmen dabei die extremen Hebungsraten der Amundsensee-Region ein, welche in dieser Arbeit ausführlicher untersucht wurde. Die dort ermittelten GNSS-Raten von bis zu 62mm/a und die um den Effekt rezenter Eismassenänderungen reduzierten Raten von bis zu 45mm/a stellen weltweit die größten bisher gemessenen Hebungsraten aufgrund glazial induzierter Deformationen dar. Mit zunehmendem Abstand zu den großen Gletschern dieser Region werden die Raten schnell kleiner, woraus große Gradienten resultieren. Fast alle GIA-Modelle unterschätzen die aus GNSS abgeleiteten Hebungsraten um fast eine Größenordnung im Bereich der Gletscher der Amundsensee-Region. Die Ursache liegt mit hoher Wahrscheinlichkeit in der Kombination aus einer besonderen Rheologie (geringe Mächtigkeit der Lithosphäre und geringe Viskosität der Asthenosphäre) und großen Eismassenverlusten in den letzten Jahrzehnten begründet. Dadurch dominieren jüngere Ereignisse der Vereisungsgeschichte die rezenten Raten, weshalb die klassische Trennung von sofortigen (elastischen) und über Jahrtausende anhaltenden Deformationen in diesem Fall nicht zu funktionieren scheint. Ein geringer Einfluss von tektonischen Prozessen und besonders Vulkanismus kann nicht ausgeschlossen werden, signifikante Anteile sind aber sehr unwahrscheinlich. Die horizontalen Deformationsraten der Antarktis spiegeln hauptsächlich die plattentektonische Bewegung wider. Nach Abzug der anteiligen Bewegung der Antarktischen Platte (starres Modell) fallen die horizontalen Raten sehr gering aus, was auch auf die Relativgeschwindigkeiten zutrifft. Deshalb kann die Antarktische Lithosphärenplatte insgesamt als sehr stabil betrachtet werden. Nur zwischen der Antarktischen Halbinsel und den Südlichen Shetlandinseln sowie in der Amundsensee-Region sind größere horizontale Raten vorzufinden, welche durch die Existenz einer separaten Lithosphärenplatte (Shetland-Platte) bzw. im Bereich der Amundsensee durch GIA verursacht werden. / Antarctica is a key region for the development of the climate on Earth. Global Navigation Satellite Systems (GNSS) help to better understand the associated geodynamic processes by deriving precise deformation rates of the solid Earth using repeated or continuous measurements. Besides the determination of plate tectonic movements, the determination of glacial isostatic adjustment (GIA) is one of the most important applications of GNSS in polar regions. GIA describes the response of the solid Earth to changing ice-loads. It manifests itself in a deformation measurable at the Earth's surface, which is mainly caused by redistributions of the viscous mantle material within the Earth. The ice-mass balances determined by satellite gravimetry, which serves as an input variable for climate modelling, are largely affected by errors due to the uncertainties of the GIA-induced mass redistributions. Therefore, GNSS results are very important for the validation of GIA models and studies based on them. In this thesis a consistent processing of all GNSS data was performed which were measured on bedrock in Antarctica. The data were made available within the international cooperation GIANT-REGAIN (Geodynamics In ANTarctica based on REprocessing GNSS dAta INitiative). In turn, the results of this work are a contribution to this project as well. A major problem of previous GNSS studies in Antarctica has been the limited coverage, resulting from either a regional analysis or a limited selection of GNSS sites for investigations on a continental or global scale. Moreover, some important regions were only very rarely considered, such as the Amundsen Sea embayment which is characterized by an extreme ice-mass loss. Various GNSS studies accomplished so far used different processing strategies, input models and reference frames, so that inferred rates cannot be compared directly. Therefore, in most cases a validation of the GIA models is only possible to a limited extent. Now, with the joint processing of more than 250 GNSS sites for the period from 1995 to 2017 the previous limitations could be circumvented. Deformation rates could be determined for almost all sites, which are derived from a homogeneous analysis and are, therefore, directly comparable and interpretable. Besides the processing of GNSS data another focus lies on the treatment of associated metadata. Their correct or insufficient acquisition can have a significant influence on the derived deformation rates. By setting up a data management system including various graphical interfaces the data handling has been made significantly more efficient. In addition, many errors were detected and could be corrected to a great extent. Further aspects of the investigations include the optimization of the geodetic datum definition by adjusting the fiducial site selection, the detection of outliers and jumps in the time series for a reliable trend estimation, and the handling of obvious problems of some sites. Erroneous metadata and ice deposits within the antenna are among the most problematic effects. In this context, it was also shown that automated methods for the detection of outliers and jumps as well as robust methods to mitigate or eliminate these anomalies provide very good results for many sites. However, there still exist several sites with special characteristics where manual revisions are strongly recommended for. Especially the ice deposits within the antennas, which have not been investigated in detail yet, cannot be adequately considered by these methods. Furthermore, realistic measures for the uncertainties of the GNSS deformation rates were derived by a careful accuracy estimation. The deformation rates determined with GNSS in Antarctica were analysed in a geodynamic context. In East Antarctica, the vertical deformation rates are very small with only a few millimeters per year and a frequently changing sign. In contrast, the vertical deformation rates in West Antarctica are much higher and can reach several millimeters per year. The extreme uplift rates in the area of the Amundsen Sea embayment play a special role and were investigated in more detail within this thesis. There, the GNSS rates reach values of up to 62mm/a and, reduced by the effect of recent ice-mass changes, of up to 45mm/a. They represent the largest measured uplift rates due to glacially induced deformations worldwide. With increasing distance to the large glaciers of this region, the rates decrease rapidly, resulting in large gradients. Nearly all GIA models underestimate the GNSS-derived uplift rates by almost an order of magnitude in that area. This is most likely due to the combination of a special rheology (small thickness of the lithosphere and low viscosity of the asthenosphere) and an extreme ice-mass loss during the last decades. As a result, more recent events in the ice-load history dominate the present-day rates, which is why the classical separation of immediate (elastic) deformations and those that persist over millennia does not seem to work in this case. A minor effect of tectonic processes and especially volcanism cannot be excluded but has most likely no significant influence. The horizontal deformation rates in Antarctica mainly reflect plate tectonic motion. After deducting the proportional motion of the Antarctic Plate, the horizontal rates are very small, which also applies to the relative velocities. Therefore, the Antarctic Plate can be considered as very stable overall. Only between the Antarctic Peninsula and the South Shetland Islands as well as in the Amundsen Sea embayment larger horizontal rates can be found, which are caused by a separate lithospheric microplate (Shetland Plate) or by the considerable GIA effect in the Amundsen Sea embayment, respectively.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 79-82. / by James Louis Muller. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Steven William Roecker. / Ph.D.

Constituant la couche limite supérieure de la convection mantellique, la lithosphère terrestre est à l'interface entre les enveloppes externes et internes de notre Planète. Les interactions multiples entre celle-ci et le manteau sont à l'origine de déformations latérales (tectonique des plaques) et verticales (topographie dynamique) de la surface terrestre. Comprendre comment la formation et l'évolution d'instabilités convectives mantelliques renouvellent sans-cesse la surface est donc primordial pour améliorer nos interprétations d'un grand nombre d'observations de surface, telles que la formation de bassins sédimentaires, le mouvement des continents, la localisation des points chauds, la formation d'anomalies gravimétriques ou encore les variations du niveau marin.Cette thèse propose de développer des modèles numériques de convection mantellique générant defaçon auto-organisée de la tectonique des plaques en surface an d'étudier la façon dont le développement et la dynamique d'instabilités convectives telles que les panneaux de subduction ou les panaches mantelliques modifient la surface, dans un contexte de tectonique de surface approchant le régime terrestre.Dans une première partie, je m'intéresse à l'influence du couplage des mouvements de convection mantellique et de tectonique des plaques sur le développement de topographie dynamique (i.e. les mouvements verticaux de la lithosphère induits par la convection mantellique) à différentes échelles spatio-temporelles. Mes résultats suggèrent que la surface terrestre peut se déformer à toutes les échelles spatiales, du fait de mouvements convectifs de grande ampleur faisant intervenir le manteau entier (> 104 km) ou encore de convection à petite échelle sub-lithosphérique (< 500 km). Les variations temporelles de topographie dynamique s‘étendent de cinq à plusieurs centaines de millions d'années selon la nature des processus convectifs dont elles dérivent. En particulier, la dynamique d'initiation ou d'arrêt des zones de subduction contrôle l'existence d'échelles intermédiaires de topographie dynamique (longueurs d'onde variant entre 500 et 104 km). Ces résultats montrent donc que les interactions entre la dynamique de la lithosphère et la convection mantellique génèrent des motifs spatio-temporels de topographie dynamique complexes et cohérents par rapport aux observations terrestres.Dans un deuxième temps, cette thèse se focalise sur la dynamique des panaches mantelliques, et leurs interactions avec la surface. Je caractérise d'abord précisement le comportement des panaches générés dans nos modèles de convection à la lumière d'observations de surface. Puis, j'étudie la façon dont leurs interactions avec la tectonique de surface et les différentes échelles convectives modifient leurs mouvements latéraux. Enfin, la compréhension de la signature thermique des interactions entre panaches et rides océaniques me permet de proposer une reconstitution des mouvements relatifs entre le panache des Açores et la ride médio-Atlantique. / Earth's lithosphere, which is the upper boundary layer of mantle convection, represents the interface between the external and internal envelopes of our Planet. The multiple interactions between the mantle and lithosphere generate lateral (plate tectonics) and vertical (dynamic topography) deformations of Earth's surface. Understanding the influence of the dynamics of mantle convective instabilities on the surface is fundamental to improve our interpretations of a large range of surface observations, such as the formation of sedimentary basins, continental motions, the location of hotspots, the presence of gravity anomalies or sea-level variations.This thesis aims at developing numerical models of whole-mantle convection self-generating plate-like tectonics in order to study the impacts of the development and the dynamics of mantle convective instabilities (such as slabs or mantle plumes) on the continuous reshaping of the surface.First, I focus on the influence of the coupling between mantle convective motions and plate tectonics on the development of dynamic topography (i.e. surface vertical deformations induced by mantle convection) at different spatial and temporal scales. The results suggest that Earth's surface can deform over large spatial scales (> 104 km) induced by whole-mantle convection to small-scales (< 500 km) arising from small-scale sub-lithospheric convection. The temporal variations of dynamic topography range between five and several hundreds of millions of years depending on the convective instabilities from which they originate. In particular, subduction initiation and slab break-off events control the existence of intermediate scales of dynamic topography (between 500 and 104 km). This reflects that the interplay between mantle convection and lithosphere dynamics generates complex spatial and temporal patterns of dynamic topography consistent with constraints for Earth.A second aim of this thesis is to understand the dynamics of mantle plumes and their interactionswith surface. I first characterize in detail the behaviour of mantle plumes arising in models ofwhole-mantle convection self-generating plate-like tectonics, in light of surface observations. Then, I study how the interactions between surface plate tectonics and mantle convection affect plume motions. Finally, I use observations of the thermal signature of plume/ridge interactions to propose a reconstruction of the relative motions between the Azores mantle plume and the Mid-Atlantic Ridge.

Las cuencas sinorogénicas de Cuba se desarrollaron como consecuencia de la convergencia entre las placas del Caribe y Norteamericana. Dicha convergencia evolucionó desde un contexto de subducción-acreción durante el Cretácico tardío hasta un contexto de acreción-colisión durante el Paleógeno, y finalizó con la sutura del Orógeno Cubano a la Placa Norteamericana. En la evolución de las cuencas se distinguen dos estadios sinorogénicos y uno post-orogénico. Los estadios sinorogénicos están relacionados con la subducción-acreción del terreno Caribeana, que subdujo bajo el Arco Volcánico Caribeño quedando parcialmente acrecionado a éste durante el Campaniense Superior y el Maastrichtiense, y con la colisión entre el arco y el margen continental norteamericano durante el Paleógeno. El estadio post-orogénico se inició diacrónicamente durante el Eoceno, siendo más joven hacia el Este. El análisis tectonoestratigráfico de las cuencas constituye, conjuntamente con el estudio del magmatismo y del metamorfismo, una de las principales herramientas para definir la evolución del Orógeno Cubano. En Cuba hemos diferenciado cuencas contraccionales, extensionales y de desgarre que se originaron sincrónicamente. Las cuencas contraccionales se desarrollaron en la parte norte del orógeno y pueden interpretarse como un sistema de cuencas de antepaís que incluye cuencas transportadas y de antefosa. Las cuencas transportadas evolucionaron desde un contexto de antearco (Arco Volcánico Caribeño) en el Cretácico tardío hasta un contexto de colisión durante el Paleógeno. Las cuencas de antefosa se desarrollaron hacia el norte del cinturón orogénico como resultado de la flexión litosférica asociada al peso del orógeno. La sedimentación sinorogénica en las cuencas contraccionales comenzó durante el Cretácico tardío (Campaniense) y finalizó después del Eoceno Inferior en Cuba occidental, del Eoceno Medio en Cuba central, y del Eoceno Superior en Cuba oriental. Ésta se produjo principalmente en medios marinos e incluye secuencia olistostrómicas y flyschoides que registran la evolución de la convergencia. Por otra parte, las cuencas extensionales estuvieron relacionadas con la apertura de la cuenca de Yucatán y se formaron en la parte sur del orógeno durante el Paleógeno. Estas cuencas evolucionaron inicialmente como cuencas de intra-arco y luego fueron incorporadas al orógeno como cuencas intramontanas. La sedimentación sinorogénica en las cuencas extensionales se produjo en ambientes marinos profundos e incluye series turbidíticas derivadas de la erosión de rocas volcánicas y metamórficas. Finalmente, las cuencas de desgarre pueden interpretarse como cuencas poligenéticas asociadas a corredores tectónicos que son oblicuos al orógeno. El relleno sedimentario sinorogénico de las cuencas de desgarre indica altas tasas de subsidencia e incluye series olistostrómicas y turbidíticas que presentan grandes cambios laterales de facies y de espesores. La formación coetánea de todos estos tipos de cuencas sugiere que diversos regímenes tectónicos (de compresión, de extensión y de desgarre) se produjeron durante la formación del Orógeno Cubano. Este hecho explica varias particularidades estructurales y evolutivas del orógeno, entre ellas la diferenciación de dominios estructurales, la partición de la deformación, y la segmentación del orógeno en bloques que evolucionaron de manera independiente. Tomando como referencia las cuencas de Cuba central (bloque de Las Villas), se ha logrado distinguir diferentes estilos estructurales en el Orógeno Cubano. Se reconocen tres dominios estructurales diferentes: (1) el Cinturón de Complejos Metamórficos, (2) la Zona Axial, y (3) el Cinturón de Deformación del Norte. La evolución estructural del Cinturón de Complejos Metamórficos incluye una fase compresional desarrollada durante el Cretácico tardío que es seguida por una fase extensional durante el Paleógeno. La compresión dio lugar a la formación de un prisma de acreción que fue parcialmente subducido, y la extensión produjo su exhumación en contextos de ante-arco e intra-arco. La Zona Axial fue intensamente deformada y acortada desde el Cretácico tardío hasta el Eoceno. La compresión se produjo en una fase inicial y a continuación tuvo lugar una deformación transpresiva durante el Eoceno Medio. El Cinturón de Deformación del Norte consiste en un sistema imbricado que se formó desde el Paleoceno hasta el Eoceno Medio. Los pliegues y las fallas se produjeron siguiendo una secuencia normal, con el transporte tectónico dirigido hacia el NNE. Algunas estructuras SO–NE son coetáneas con el sistema imbricado que se extiende en dirección NO–SE, formándose corredores tectónicos y/o fallas de transferencia que facilitaron un régimen de partición de la deformación mientras se producía la colisión. La sincronía de la compresión en el norte con la extensión en el sur es coherente con la apertura de la cuenca de Yucatán. La evolución desde regímenes de compresión-extensión hasta regímenes de transpresión está en consonancia con el aumento de la oblicuidad de la colisión entre las placas del Caribe y Norteamericana. Particularmente, la zona de fallas La Trocha ha actuado como una zona de transferencia siniestra que separa los bloques de Las Villas y Camagüey en Cuba central. Las estructuras que conforman dicha zona de fallas (fallas La Trocha, Zaza-Tuinicú, Cristales y Taguasco) son consistentes con la rotación en sentido horario de la convergencia y del acortamiento en Cuba central. Desde el Paleoceno hasta el Eoceno Inferior, un acortamiento en dirección SSO–NNE produjo transtensión en la falla La Trocha y transpresión en la falla Zaza-Tuinicú. Posteriormente, durante el Eoceno Medio, el acortamiento rotó hacia una dirección SO–NE, dando como resultado una componente normal en la falla La Trocha y transpresión en las fallas Zaza-Tuinicú y Cristales. A partir del Eoceno Superior Cuba central ha estado soldada a la Placa Norteamericana. La deformación post-soldadura ha producido transtensión en las fallas La Trocha y Taguasco, y es consistente con un acortamiento en dirección OSO–ENE que refleja la actividad del límite transformante de Caimán. La cinemática de las placas y la evolución estructural de la zona de fallas La Trocha indican que la Cuenca Central es una cuenca de desgarre poligenética y que la formación de este sistema (es decir, zona de fallas – cuenca de desgarre) fue una consecuencia de la colisión oblicua que ocurrió durante el Paleógeno entre el Arco Volcánico del Caribe y el margen de las Bahamas (Placa Norteamericana). La formación de los principales corredores tectónicos cubanos fue coetánea con la orogenia, lo que conllevó a la segmentación del orógeno en una serie de bloques estructurales que evolucionaron de manera independiente. La edad y evolución de la deformación sugieren que dichos corredores actuaron como importantes límites tectónicos y que evolucionaron en correspondencia con la rotación de la convergencia entre las placas. La segmentación del orógeno está también soportada por la sedimentación sinorogénica, que abarca intervalos de tiempo diferentes en cada bloque, lo que sugiere que la soldadura del orógeno a la Placa Norteamericana se produjo en una secuencia O–E (más joven hacia el Este). La segmentación del Orógeno Cubano y la evolución diferenciada de sus partes sugieren que el Caribe noroccidental evolucionó como un sistema de microplacas durante su transferencia desde la Placa del Caribe hasta la Placa Norteamericana. Asimismo, se sugiere que el límite de placas activo migró en dirección Este durante la convergencia. A partir del análisis tectonoestratigráfico de las cuencas sinorogénicas, y de sus implicaciones estructurales y tectónicas, se ha podido establecer una serie de criterios y/o recomendaciones para la exploración de hidrocarburos en Cuba. En este sentido, se sugiere que las características de los sistemas petroleros cubanos están fuertemente controladas por la estructura del orógeno. Se han diferenciado tres sistemas de plays principales; los cuales están asociados al cinturón plegado cubano, a las estructuras de desgarre principales, y al sistema de antepaís respectivamente. Se sugiere que los yacimientos por descubrir en los sistemas de plays asociados al cinturón plegado y a las estructuras de desgarre pueden contener crudos de cualquier calidad en función de las características primarias y la madurez de la roca madre, del tipo y magnitud de la migración, de la superposición o no de distintos sistemas petroleros, y/o de la ocurrencia de procesos secundarios. Asimismo, se estima que dichos yacimientos serán mayoritariamente pequeños en cuanto al volumen de sus reservas y estarán vinculados a trampas de tipo estructural; dúplex, zonas triangulares y retrocabalgamientos en el sistema de plays del cinturón plegado, y a anticlinales fallados, estructuras en flor y sellos contra falla en el sistema de plays asociado a estructuras de desgarre. En cambio, se sugiere que los yacimientos no descubiertos en el sistema de plays del antepaís podrán tener crudos de alta calidad y grandes volúmenes de reservas. No obstante, se debe considerar que, aunque el sistema de plays asociado al antepaís es actualmente el que mayor interés atrae por su valoración de riesgo/recompensa, las características geoquímicas y estructurales del Orógeno Cubano sugieren que las otras áreas no deben ser descartadas. / The synorogenic basins of Cuba are a consequence of the convergence between the Caribbean and North American plates. This convergence evolved from a subduction-accretion setting during the Late Cretaceous to an accretion-collision setting during the Paleogene, and ended with the welding of the Cuban Orogen to the North American Plate. Two synorogenic and one postorogenic stages are distinguished in the evolution of these basins. The synorogenic stages are related to the subduction-accretion of Caribeana, which was subducted beneath the Caribbean Volcanic Arc during the Late Campanian-Maastrichtian, and to the collision between the volcanic arc and the North American continental margin during the Paleogene. The postorogenic stage started during the Eocene and developed diachronically (younger eastward). The tectono-stratigraphic analysis of sedimentary basins is, in conjunction with the study of magmatism and metamorphism, a major tool in order to define the evolution of the Cuban Orogen. In Cuba, contractional, extensional and strike-slip basins evolved synchronously. Contractional basins evolved in the northern part of the orogen and may be interpreted as a foreland basin system that includes piggyback and foredeep basins. Piggyback basins evolved from a forearc setting (Caribbean Volcanic Arc) in the latest Cretaceous to a Paleogene collision setting. Foredeep basins developed northward of the orogenic belt as a consequence of the lithospheric flexion linked to the orogenic load. Synorogenic sedimentation in contractional basins started during the latest Cretaceous (Campanian) and ended after the Early Eocene in western Cuba, the Middle Eocene in central Cuba, and the Late Eocene in eastern Cuba. It occurred mainly in deep-marine environments and includes olistostromic and flyschoid series that record the evolution of convergence. Extensional basins were related to the opening of the Yucatan Basin and were formed in the southern part of the orogen during the Paleogene. These basins formerly evolved as intra-arc basins and then were incorporated to the orogen as hinterland basins. Synorogenic sedimentation in the extensional basins occurred in deep-marine environments and includes flyschoid series, which resulted from erosion of volcanic and metamorphic rocks. Strike-slip basins may be interpreted as polygenetic basins linked to major oblique tectonic corridors. Syntectonic record of the strike-slip basins suggests high subsidence rates. It includes olistostromic and flyschoid series that show large lateral changes in facies and thicknesses. The coeval formation of contractional, extensional and strike-slip basins suggests that different tectonic regimes occurred during the formation of the Cuban Orogen, explaining several structural features of the orogen as the differentiation of structural domains, the strain-partitioning, and the different evolution of some blocks. Based on a tectono-stratigraphic analysis of the sedimentary basins of central Cuba (Las Villas block), three structural domains are differentiated in the Cuban Orogen: (1) the Metamorphic Complexes Belt, (2) the Axial Zone, and (3) the Northern Deformation Belt. The structural evolution of the Metamorphic Complexes Belt includes a latest Cretaceous compressional phase followed by a Paleogene extensional phase. Contraction created an accretionary prism that was partially subducted, and extension produced exhumation in intra-arc and forearc settings. The Axial Zone was strongly deformed and shortened from the latest Cretaceous to the Eocene. Compression occurred in an initial phase and subsequent transpressive deformation took place in the Middle Eocene. The Northern Deformation Belt consists of a thin-skinned thrust fault system formed during the Paleocene to the Middle Eocene; folding and faulting occurred in a piggyback sequence with tectonic transport towards the NNE. Some major SW–NE structures are coeval with the Cuban NW–SE striking folds and thrusts, and form tectonic corridors and/or transfer faults that facilitated strain-partitioning regime attending the collision. The synchronicity of compression in the north with extension in the south is consistent with the opening of the Yucatan Basin. The evolution from compression–extension to transpression is in keeping with the increase in obliquity in the collision between the Caribbean and North American plates. Particularly, the La Trocha fault zone acted as a major left-lateral transfer zone, constituting a limit between the Las Villas and Camagüey blocks in central Cuba. Some faults that are included in this fault zone (La Trocha, Zaza-Tuinicú, Cristales and Taguasco faults) were consistent with the clockwise rotation of convergence and shortening in central Cuba. From the Paleocene to the Early Eocene, a SSW-NNE shortening produced transtension in the La Trocha fault and transpression in the Zaza-Tuinicú fault. Subsequently, during the Middle Eocene, shortening shifted to a SW-NE direction, resulting in the normal component of the La Trocha fault and transpression in the Zaza-Tuinicú and Cristales faults. Since the Late Eocene, central Cuba has been welded to the North American Plate. The post-welding deformation gave rise to transtension of the La Trocha and Taguasco faults. This deformation is consistent with a WSW-ENE shortening and reflects activity in the transform boundary of the Cayman Trough. Plate-kinematics and the structural evolution of the La Trocha fault zone indicate that the related Central Basin is a strike-slip polygenetic basin and that the formation of this system (i.e., fault zone – strike-slip basin) was a consequence of the Paleogene oblique collision between the Caribbean Volcanic Arc and the Bahamas Borderland (North American plate). The formation of the Cuban tectonic corridors was coeval with the orogeny, which led to the segmentation of the orogen into a number of structural blocks that evolved in different way. Age and evolution of deformation suggest that the Cuban corridors acted as important tectonic limits that evolved in accordance with rotation of the convergence between the Caribbean and North American plates. Segmentation of the orogen is also supported by the synorogenic sedimentation, which embraces different time spans in each block, suggesting that welding of the orogen to the North American Plate progressed from W to E. The segmentation of the orogen and different evolution of the Cuban blocks lend support to the evolution of the NW-Caribbean as a dynamic microplate system and to the eastward migration of the active transform plate boundary during the convergence. Based on the tectono-stratigraphic analysis of the Cuban basins, we were able to establish a set of criteria and/or recommendations for hydrocarbon exploration in Cuba. In this direction, it is suggested that the major features of the Cuban petroleum systems are strongly controlled by the structure of the orogen. Three major play systems are differentiated, which are linked to the Cuban fold-and-thrust belt, to the major strike-slip structures, and to the foreland basin respectively. The undiscovered oil fields in the plays linked to the fold-and-thrust belt and to the strike-slip structures could contain different oil types depending on the primary features and maturity of the source rocks, the migration type, the occurrence and superposition of different petroleum systems, and/or the occurrence of secondary processes. It is also estimated that these oil fields will be mostly small in volume of resources and will be linked to structural traps; duplexes, triangle zones and backthrusts in the plays related to the fold-and-thrust belt, and faulted anticlines, flower structures and seals-faults in the plays linked to the strike-slip structures. By contrast, the undiscovered oil fields in the plays linked to the foreland could contain high-quality oils and large volumes of resources. However, we should be borne in mind that, despite the risk-reward assessment of the play system linked to the foreland is attractive, geochemical and structural features of the Cuban Orogen suggest that other regions and play systems should not be dismissed.

Understanding spatial and temporal variations in strain accumulation and release along plate boundaries is a fundamental problem in tectonics. Short-term and long-term slip rates are expected to be equal if the regional stress field remains unchanged over time, yet discrepancies between modern geodetic (decadal time scale) slip rates and long-term geologic (10^3 to 10^6 years) slip rates have been observed on parts of the Pacific-North American plate boundary system. Contemporary geodetic slip rates are observed to be ~2 times greater than late Pleistocene geologic slip rates across the southern Walker Lane. I use a combination of GPS geodesy, detailed field geologic mapping, high-resolution LiDAR geodetic imaging, and terrestrial cosmogenic nuclide geochronology to investigate the observed discrepancy between long- and short-term slip rates. I find that the present day slip rate derived from GPS geodesy across the Walker Lane at ~37.5°N is 10.6 ± 0.5 mm/yr. GPS data suggest that much of the observed discrepancy occurs west of the White Mountains fault zone. New dextral slip rates on the White Mountains fault zone of 1.1 ± 0.1 mm/yr since 755 ka, 1.9 +0.5/-0.4 mm/yr since 75-115 ka, 1.9 +0.5/-0.4 mm/yr since 38.4 ± 9.0 ka, and 1.8 +2.8/-0.7 mm/yr since 6.2 ± 3.8 ka are significantly faster than previous estimates and suggest that slip rates there have remained constant since the middle Pleistocene. On the Lone Mountain fault I calculate slip rates of 0.8 ± 0.1 mm/yr since 14.6 ± 1.0 ka and 0.7 ± 0.1 mm/yr since 8.0 ± 0.5 ka, which suggest that extension in the Silver Peak-Lone Mountain extensional complex has increased dramatically since the late Pleistocene.

Les causes de l’activité sismique à l’intérieur des plaques tectoniques sont encore mal comprises, que ce soit l’origine des contraintes responsables des séismes ou leur relation avec la variation dans le temps et dans l’espace de l’activité sismique.<p>Les contraintes à l’intérieur des plaques résultent de l’action de forces de longueurs d’onde différentes, qui se superposent et s’additionnent. En utilisant une nouvelle méthode (Camelbeeck et al. 2013), déterminant les contraintes générées localement (échelle de 10 à 100 km), nous estimons l’importance relative de cette composante locale du champ de contrainte. En comparant ces contraintes locales avec les contraintes déduites des mécanismes au foyer des tremblements de terre en Europe occidentale, nous suggérons que celles-ci semblent jouer un rôle non-négligeable dans l’occurrence de l’activité sismique. C’est le cas dans des régions où les contraintes locales étaient déjà reconnues, mais également dans des régions précédemment identifiées comme dominées par les contraintes à plus grandes longueurs d’onde.<p>Le champ de contrainte généré localement est constant à l’échelle de temps des catalogues sismiques, ce qui ne permet pas d’expliquer l’occurrence dans le temps des séismes. Il est cependant modifié par les variations des contraintes locales générées par l’activité séismique elle-même, ce qui explique les séquences de répliques des séismes de Roermond (13/04/1992, Mw=5.4) et d’Alsdorf (22/07/2002, Mw= 4.7) dans le graben de la Roer. Nous y suggérons également l’importance de ces variations à une échelle de temps plus longue (millier d’années) à partir des données de paléoséismologie.<p>Pour mieux comprendre les relations spatio-temporelles des séismes, nous avons également analysé dans quelle mesure l’occurrence de l’activité sismique dans le graben de la Roer est un processus de Poisson, ou si l’activité future est localisée à proximité des séismes du passé, ou située dans des régions dénuées de séismes à ce jour. L’emploi des méthodes linéaires classiques et de méthodes non-linéaires dans cette région mais aussi dans les îles britanniques et dans le sud de la Norvège montrent que les séismes du passé ne peuvent expliquer les taux d’activité sismique actuellement mesurés. Une partie de l’activité sismique correspond ainsi à une activité de background, indépendante de l’occurrence des séismes du passé. La méthode des multifractales permet aussi de caractériser régionalement l’importance, la variété et continuité des processus responsables de l’activité sismique sans pour autant en identifier les causes. <p>Notre travail nous a permis d’identifier l’importance relative de certaines causes de l’activité sismique, par exemple l’importance des variations locales des contraintes générées par l’activité séismique elle-même, mais n’a pas permis par exemple d’identifier l’origine de l’activité de background, clairement mise en évidence par l’analyse multifractale./<p><p> / Doctorat en sciences, Spécialisation géologie / info:eu-repo/semantics/nonPublished

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study investigates the crustal structure, and assesses the qualitative and quantitative impacts of crust-mantle dynamics on subsidence pattern, past and present-day thermal field and petroleum system evolution at the southern South African continental margin through the application of a multi-disciplinary and multi-scale geo-modelling procedure involving both conceptual and numerical approaches. The modelling procedure becomes particularly important as this margin documents a complex interaction of extension and strike-slip tectonics during its Mesozoic continental rifting processes. Located on the southern shelf of South Africa, the Western Bredasdorp Basin (WBB) constitutes the focus of this study and represents the western section of the larger Bredasdorp sub-basin, which is the westernmost of the southern offshore sub-basins. To understand the margin with respect to its present-day structure, isostatic state and thermal field, a combined approach of isostatic, 3D gravity and 3D thermal modelling was performed by integrating potential field, seismic and well data. Complimenting the resulting configuration and thermal field of the latter by measured present-day temperature, vitrinite reflectance and source potential data, basin-scale burial and thermal history and timing of source rock maturation, petroleum generation, expulsion, migration and accumulation were forwardly simulated using a 3D basin modelling technique. This hierarchical modelling workflow enables geologic assumptions and their associated uncertainties to be well constrained and better quantified, particularly in three dimensions. At present-day, the deep crust of the WBB is characterised by a tripartite density structure (i.e. prerift metasediments underlain by upper and lower crustal domains) depicting a strong thinning that is restricted to a narrow E-W striking zone. The configuration of the radiogenic crystalline crust as well as the conductivity contrasts between the deep crust and the shallow sedimentary cover significantly control the present-day thermal field of the study area. In all respects, this present-day configuration reflects typical characteristics of basin evolution in a strike-slip setting. For instance, the orientations of the deep crust and fault-controlled basin-fill are spatially inconsistent, thereby indicating different extension kinematics typical of transtensional pull-apart mechanisms. As such, syn-rift subsidence is quite rapid and short-lived, and isostatic equilibrium is not achieved, particularly at the Moho level. Accompanied syn-rift rapid subsidence and a heat flow peak led to petroleum preservation in the basin since the Early Cretaceous. Two additional post-rift thermal anomalies related to the Late Cretaceous hotspot mechanism and Miocene margin uplift in Southern Africa succeeded the syn-rift control on maturation. This thermal maturity of the five mature source rocks culminated in four main generation and three main accumulation phases which characterise the total petroleum systems of the WBB. The Campanian, Eocene and Miocene uplift scenarios episodically halted source maturation and caused tertiary migration of previously trapped petroleum. Petroleum loss related to the spill point of each trap configuration additionally occurs during the Late Cretaceous-Paleocene and Oligocene-Early Miocene. The timing and extent of migration dynamics are most sensitive to the geological scenario that combined faulting, intrusive seal bypass system and facies heterogeneity. In fact, for models that do not incorporate facies heterogeneity, predicted past and present-day seafloor leakage of petroleum is largely underestimated. This complex interplay of generation and migration mechanisms has significant implications for charging of petroleum accumulations by multiple source rocks. Due to early maturation and late stage tertiary migration, the syn-rift source rocks particularly Mid Hauterivian and Late Hauterivian source intervals significantly control the extent of petroleum accumulation and loss in the basin. Lastly, the modelled 3D crustal configuration and Mezosoic to Cenozoic thermal regime of the WBB dispute classic uniform lithospheric stretching for the southern South African continental margin. Rather, this PhD thesis confirms that differential thinning of the lithosphere related to a transtensional pull-apart mechanism is the most appropriate for accurately predicting the evolution of basin and petroleum systems of the margin. Also, the presented 3D models currently represent the most advanced insights, and thus have clear implications for assessing associated risks in basin and prospect evaluation of the margin as well as other similar continental margins around the world. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die korsstruktuur en evalueer die kwalitatiewe en kwantitatiewe impakte van kors-mantel-dinamika op insinkingspatroon, die termiese veld en petroleumstels evolusie aan die suidelike Suid-Afrikaanse kontinentale grens, in die hede en die verlede, deur die toepassing van ’n multidissiplinêre en multiskaal-geomodelleringsprosedure wat beide konseptuele en numeriese benaderings behels. Die modelleringsprosedure veral is belangrik aangesien hierdie kontinentale grens ’n komplekse interaksie van uitbreidings- en strekkingsparallelle tektoniek gedurende die Mesosoïese vastelandskeurprosesse daarvan dokumenteer. Omdat dit op die suidelike platvorm van Suid-Afrika geleë is, maak die Westelike Bredasdorp Kom (WBK) die fokus van hierdie studie uit, en verteenwoordig dit die westelike deel van die groter Bredasdrop-subkom, wat die verste wes is van die suidelike aflandige subkomme. Om die grens met betrekking tot sy huidige struktuur, isostatiese staat en termiese veld te verstaan, is ’n kombinasie benadering bestaande uit isostatiese, 3D-gravitasie- en 3D- termiese modellering gebruik deur potensiëleveld-, seismiese en boorgatdata te integreer Ondersteunend totot die gevolglike konfigurasie en termiese veld van die laasgenoemde deur middel van hedendaagse temperatuur, soos gemeet, vitriniet-refleksiekoëffisiënt en bronpotensiaal data, komskaal-begrawing en termiese geskiedenis en tydsberekening van brongesteentematurasie, is petroleumgenerasie, -uitwerping, -migrasie en -akkumulasie in die toekoms gesimuleer deur gebruik te maak van ’n 3D-kommodelleringstegniek. Hierdie hierargiese modelleringswerkvloei maak dit moontlik om geologiese aannames en hulle geassosieerde onsekerhede goed aan bande te lê en beter te kwantifiseer, veral in drie dimensies. In die hede word die diep kors van die WBK gekarakteriseer deur ’n drieledige digtheidstruktuur (met ander woorde voorrift-metasedimente onderlê deur bo- en benedekors domeine) wat dui op ’n baie wesenlike verdunning, beperk tot ’n dun O-W-strekkingsone. Die konfigurasie van die radiogeniese kristallyne kors, sowel as die konduktiwiteitskontraste tussen die diep kors en die vlak sedimentêre dekking, beheer grotendeels die hedendaagse termiese veld van die studiearea. Hierdie hedendaagse konfigurasie weerspieël in alle opsigte tipiese eienskappe van kom-evolusie in ’n skuifskeur omgewing. Byvoorbeeld, Die oriëntasies van die diep kors en verskuiwingbeheerde komsedimentasie byvoorbeeld is ruimtelik inkonsekwent en dui daardeur op verskillende ekstensiekinematika, tipies van transtensionale tensiemeganisme. As sulks, is sin-rift-versakking taamlik vinnig en kortstondig, en word isostatiese ekwilibrium nie by die Moho-vlak, in die besonder, bereik nie. Samehangende sin-rift vinnige versakking en hittevloeihoogtepunt het gelei tot petroleum behoud in die kom sedert die vroeë Kryt. Twee bykomende post-rift termiese anomalieë wat verband hou met die laat Kryt-“hotspot” meganisme en die Mioseense kontinentale grensopheffing in Suidelike Afrika het die sin-rift-beheer met maturasie opgevolg. Hierdie termiese maturiteit van die vyf gematureerde brongesteentes het in vier hoofgenerasie- en drie hoofakkumulasie fases, wat die totaliteit van die petroleumstelsels van die WBK karakteriseer, gekulmineer. Die Campaniese, Eoseense en Mioseense opheffings senarios het episodies bronmaturasie gestop en tersiêre migrasie van petroleum wat vroeër opgevang was veroorsaak. Addisioneel vind petroleumverlies gekoppel aan die spilpunt van elke opvanggebiedkonfigurasie tydens die laat Kryt-Paleoseen en Oligoseenvroeë Mioseen plaas. Die tydstelling en omvang van migrasiedinamika is die sensitiefste vir die geologiese scenario wat verskuiwing, seëlomseilingstelsel en fasiesheterogeniteit kombineer. Trouens, vir modelle wat nie fasiesheterogeniteit inkorporeer nie, is voorspellings van vroeëre en huidige seebodemlekkasie van petroleum grotendeels onderskattings. Hierdie komplekse wisselwerking van generasie- en migrasiemeganismes het beduidende implikasies vir die laai van petroleumakkumulasies deur veelvoudige brongesteentes. Vanweë vroeë maturasie en laatstadiumtersiêre migrasie, oefen die sin-rift-brongesteentes, veral middel Hauterivium- en laat Hauteriviumbronintervalle, beduidende beheer oor die omvang van petroleumakkumulasie en -verlies in die kom uit. Laastens weerspreek die gemodelleerde 3D-korskonfigurasie en Mesosoïese-tot-Senosoïesetermiese regime van die WBK ’n klassieke uniforme litosferiese rekking vir die suidelike Suid- Afrikaanse kontinentale grens. Inteendeel, hierdie PhD-proefskrif bevestig dat ’n differensiële verdunning van die litosfeer, gekoppel aan ’n transtensiemeganisme, die beste geskik is om ’n akkurate voorspelling oor die evolusie van kom- en petroleumstelsels van die kontinentale grens mee te maak. Verder, verteenwoordig die 3D-modelle, wat hier aangebied word, tans die mees gevorderde insigte, en het hierdie modelle dus duidelike implikasies vir die assessering van verwante risiko’s in kom- en petroleum teikene valuering van die kontinentale grens, so wel as van ander soortgelyke kontinentale grense regoor die wêreld.

Paleomagnetic data from 25 sites (5 samples per site) in andesite flows of the Gringo Gulch Volcanics in Santa Cruz County, Arizona, were analyzed to determine a lower Paleocene paleomagnetic pole. Alternating-field demagnetization to 500 oe peak field was sufficient to erase secondary viscous components. The mean direction of magnetization (inclination = -58.8°, declination = 167.5 °) was obtained by averaging the site mean directions of the 25 sites, which are all reversed. The resultant lower Paleocene pole position is at lat. 77.0 °N, 1on. 201.0 °E (dp = 1.2 °, dm = 1.7 °).

Controls on denudation in the eastern Bolivian Andes are evaluated by synthesis of new and existing denudation estimates from basin-morphometry, stream - powered fluvial incision, landslide mapping, sediment flux, erosion surfaces, thermochronology, foreland basin sediment volumes, and structural restorations. Centered at 17.5 °S, the northeastern Bolivian Andes exhibit high relief, a wet climate, and a narrow fold- thrust belt. In contrast, the southeastern Bolivian Andes have low relief, a semi-arid climate, and a wide fold-thrust belt. Basin -morphometry indicates a northward increase in relief and relative denudation. Stream-power along river profiles shows greater average incision rates in the north by a factor of 2 to 4. In the south, profile knickpoints with high incision rates are controlled by fold-thrust belt structures such as the surface expressions of basement megathrusts, faults, folds, and lithologic boundaries. Landslide and sediment-flux data are controlled by climate, elevation, basin morphology, and size and show a similar trend; short -term denudation-rate averages are greater in the north (1- 9 mm/yr) than the south (0.3-0.4 mm/yr). Long-term denudation-rate estimates including fission track, basin fill, erosion surfaces, and structural restorations also exhibit greater values in the north (0.2-0.8 mm/yr) compared to the south (0.04-0.3 mm/yr). Controls on long-term denudation rates include relief, orographic and global atmospheric circulation patterns of precipitation, climate change, glaciation, and fold-thrust belt geometry and kinematics. The denudation synthesis supports two conclusions: 1) denudation rates have increased towards the present 2) an along-strike disparity in denudation (greater in the north) has existed since at least the Miocene and has increased towards the present. Denudation rates and controls suggest that Bolivian mountain morphology is controlled by both its orientation at mid-latitude, and the feedbacks between uplift, kinematics, orographic effects on precipitation, glaciation, and the increased erosion that accompanies orogenesis.