Search

The pressure-temperature-time (P-T-t) evolution of metamorphic rocks is directly related to geodynamics as different tectonic settings vary in their thermal architecture. The shapes of P-T paths and thermobaric ratios (T/P) of metamorphic rocks have been extensively used to distinguish different tectonic domains. However, the role of metamorphic timescales in constraining tectonic settings remains underutilized. This is because of the poorly understood relationship between them, and the difficulty in accurately constraining the onset and end of a particular metamorphic event. Here, we show why and how the intrinsic relationship between thermal regime, rheology and rate of motion controlled by the heat, mass and momentum conservation laws translate to differences in heating, cooling, burial, exhumation rates of metamorphic rocks and thereby, to the duration of metamorphism. We compare the P-T-t paths of the orogenic metamorphic rocks of different ages and in particular, analyse their retrograde cooling rates and durations. The results show that cooling rates of the metamorphic rocks are variable but are dominantly 100 °C/Ma) during the late Neoproterozoic to Phanerozoic. To seek what controlled this secular change in metamorphic cooling rates, we use thermomechanical modelling to calculate the P-T-t paths of crustal rocks in different types of continental orogenic settings and compare them with the rock record. The modelled P-T-t paths show that lithospheric peel-back driven orogenic settings, which are postulated as an orogenic mode operating under the hotter mantle conditions of late Archean to early Proterozoic, are characterised by longer durations of metamorphism and slower cooling rates (a few 10s of °C/Ma) as compared to the modern orogenic settings (a few 100s of °C/Ma) operating under relatively colder mantle conditions. This is because peel-back orogens feature: (1) hot lithospheres with very high crustal geotherms being sustained by high mantle heat-flow and profuse magmatism, and (2) distributed deformation patterns that limit vertical extrusion (exhumation) of the metamorphic rocks along localized deformation zones and instead, trap them in the orogenic core for a long time. In contrast, modern orogens mostly involve colder lithospheres and allow rapid exhumation through localized deformation, which facilitates faster cooling of hot, exhumed metamorphic rocks in a colder ambience. Thus, we propose that the secular change in metamorphic cooling rates indicates a changing regime of orogenesis and thereby, of plate tectonics through time. Predominance of the slower metamorphic cooling rates before the Neoproterozoic indicate the occurrences of peel-back orogenesis and truncated hot (collisional) orogenesis during that time, while the appearance of faster cooling rates since the late Neoproterozoic indicates the transition to modern style of orogenesis. A transition between these orogenic styles also accounts for the prolonged longevity (>100 million years) of many Precambrian orogenic belts as compared to the Phanerozoic ones. This study underscores the strength of timescales in combination with P-T paths to distinguish tectonic settings of different styles and ages. ISSN:1342-937X ISSN:1878-0571

International audience; Although the Helvetic nappes of the Western Alps have been widely studied, their style, amount, and timing of deformation during the Alpine orogeny remain a subject of controversy. The discussion partly arises from various interpretations of the external crystalline massifs geometry and of the cover/basement relationships. Here, we apply structural analysis based on new field data, microtectonics, and 3D geological modeling on the Aiguilles Rouges and Mont-Blanc massifs, to better quantify their tectonic evolution and their relationship with the nappe stacking. Our results show large thrusting of the Helvetic Mesozoic sedimentary cover above the Aiguilles Rouges basement towards the WNW. The basal contact of the Helvetic nappes, which we call the Helvetic Basal thrust (HBT), often corresponds to a décollement level localized above the Triassic unconformity, but that locally also affects the basement. We suggest that most of the subalpine ranges are klippes above the HBT, and estimate the shortening of the thrust from previously published cross-sections to be between 13 and 32 km. According to published ages, we argue that the HBT was active in the Oligo-Miocene, between ∼30 and ∼14 Ma. After ∼14 Ma and until ~6 Ma, the HBT is offset by late steep out-of-sequence faults, including back-thrusts and the Mont-Blanc shear zone that was previously a ramp of the HBT. The transition of the major thrust system from the HBT rooting above (east) of the Mont-Blanc to the Alpine sole thrust rooting below (west) of the Aiguilles Rouges occurred between 18 and 14 Ma.

Key in understanding the geodynamics governing subduction and orogeny is reconstructing the paleogeography of ‘Greater India’, the Indian plate lithosphere that subducted since Tethyan Himalayan continental collision with Asia. Here, we discuss this reconstruction from paleogeographic, kinematic, and geodynamic perspectives and isolate the evolution scenario that is consistent with all three. We follow recent constraints advocating a ~58 Ma initial collision and update a previous kinematic restoration of intra-Asian shortening with a recently proposed model that reconciles long-debated large and small estimates of Indochina extrusion. Our new reconstruction is tested against paleomagnetic data, and against seismic tomographic constraints on paleo-subduction zone locations. The resulting restoration shows ~1000–1200 km of post-collisional intra-Asian shortening, leaving a 2600–3400 km wide Greater India. From a paleogeographic, sediment provenance perspective, Eocene sediments in the Lesser Himalaya and on undeformed India may be derived from Tibet, suggesting that all Greater Indian lithosphere was continental, but may alternatively be sourced from the contemporaneous western Indian orogen unrelated to India-Asia collision. A quantitative kinematic, paleomagnetic perspective prefers major Cretaceous extension and a ‘Greater India Basin’ opening within Greater India, but data uncertainty may speculatively allow for minimal extension. Finally, from a geodynamic perspective, assuming a fully continental Greater India would require that subduction rates close to 20 cm/yr was driven by a down-going lithosphere-crust assemblage more buoyant than the mantle, which seems physically improbable. We conclude that the Greater India Basin scenario is the only sustainable one from all three perspectives. We infer that old pre-collisional lithosphere rapidly entered the lower mantle sustaining high subduction rates, whilst post-collisional continental and young Greater India basin lithosphere did not, inciting the rapid India-Asia convergence deceleration ~8 Myr after collision. Subsequent absolute northward slab migration and overturning caused flat slab subduction, Tibetan shortening, arc migration and arc volume decrease.

In many mountain belts, deformation concentrates along mechanically weak fault zones inherited from earlier tectonic events. This work investigates the effects of two modes of structural weakening on the orientation of rifting and later tectonic inversion with respect to the imposed divergence/convergence direction in a high-resolution 3D finite difference model with a viscous-frictional rheology. In the first set of experiments, weakening consists in a decrease in frictional strength with increasing shear strain. The generated normal faults strike orthogonal to the imposed divergence direction. These faults are reactivated during tectonic inversion and absorb 50 to 70 percent of accumulated strain. In the second set of experiments, frictional strength is a decreasing function of shear strain rate. The generated faults are oblique to the divergence direction, implying oblique fault slip. Fault reactivation depends on the obliquity of the inverted rift to convergence direction, where larger obliquity leads to more intense fault reactivation. These new numerical results are compared to previous analogue and numerical models on the one hand, and natural examples of intracontinental mountain ranges due to tectonic inversion on the other hand. These comparisons demonstrate that both modes of frictional weakening should be taken into account when seeking to understand large-scale rifting and inversion tectonics., Financial support was provided by the Swiss National Science Foundation (grant 2-77297-15).

El distrito Casposo se ubica en el borde oriental de la Cordillera Frontal, departamento de Calingasta, en el oeste de la provincia de San Juan, Argentina. El mismo se conforma de un extenso sistema de vetas epitermales de baja sulfuración, dentro del cual se desarrolla una mina en explotación (actualmente inactiva). Desde el inicio de sus actividades en el año 2011 y hasta el 2015, esta mina produjo un total de 283.200 oz de Au y 9,5 Moz de Ag. La geología del yacimiento está caracterizada por afloramientos de una secuencia marina (Formación La Puerta), depositada entre el Carbonífero y el Pérmico temprano, que fue intensamente deformado durante la fase orogénica San Rafael (Pérmico inferior). Sobre esta secuencia, y mediante una importante discordancia angular (Superficie San Rafael), tuvo lugar un importante magmatismo representado por el Grupo Choiyoi, de naturaleza subalcalina que evolucionó desde términos calcoalcalinos hacia composiciones shoshoníticas. Entre los 269,7 Ma y los 256,7 Ma (Pérmico medio a superior) este magmatismo presentó su mayor intensidad y volumen, resultando en una potente secuencia piroclástica con presencia de discordancias intraformacionales (Sección inferior y superior), que es intruída por cuerpos subvolcánicos (denominados Dacita Casposo y Andesita Cerro Pelado). Este vulcanismo evolucionó de manera sincrónica a la intrusión de importantes cuerpos plutónicos de grandes dimensiones como la Granodiorita Casposo, que potencialmente podrían representar las partes más profundas del mismo sistema magmático, aunque una importante falla N-S separa ambos ambientes. Durante las etapas terminales de este periodo, entre los 263,6 Ma y los 256,7 Ma, se habría instalado el sistema hidrotermal responsable de la formación del yacimiento, en cercana asociación con un conjunto de cuerpos subvolcánicos denominados Dique Félsico e Intrusivo Félsico. Luego del emplazamiento de la mineralización, y mediante un período de actividad magmática nula de ~ 12 Ma, ocurrió una reactivación del magmatismo a partir de los 249,7±2 Ma (Triásico Medio) que resultó en la intrusión de una sucesión de familias de diques de composiciones intermedias a ácidas (denominados Diques Básicos, Diques Riolíticos Porfíricos y Diques de Aplitas). El yacimiento abarca un área de aproximadamente 100 km2 formado por vetas que exhiben una marcada zonación composicional: las puramente silíceas concentradas en la zona de operaciones de mina (Mercado, Aztec, B Vein, Inca), vetas cuarzo-carbonáticos (Cerro Norte, Lucía), y las puramente carbonáticas con pulsos silíceos (Oveja Negra, Aurora, Casposo Norte, Leñador y Julieta). Las texturas predominantes son las de relleno de espacios abiertos, como los bandeados coloformes con desarrollo de ginguros, crustiformes, cocardas, masivas y brechas con cemento de sulfuros. Del detallado análisis estructural realizado sobre las secciones transversales y plantas de la zona de mina, se determinó un vector de máxima apertura NE-SO actuando en simultáneo a la formación de la mineralización (control sin-mineral), que luego habría sido afectada por al menos dos eventos posteriores de fallamiento (control post-mineral). A partir del análisis de detallado de la mineralogía y textura de la veta Inca, se discriminaron 9 pulsos que fueron agrupados en 6 episodios principales, siendo 5 de ellos de naturaleza hidrotermal y 1 de del tipo tectónico-hidrotermal. Los pulsos P1 y P2 son estériles. En el pulso P3 precipitan cuarzo-calcedonia con textura bandeada coloforme, y adularia subrómbica a pseudoacicular, con minerales de mena alojadas en bandas oscuras tipo ginguro. La mena se compone de electrum (10% Au – 90% Ag) y plata nativa, sulfosales como tetraedrita (rica en Ag), pirargirita y polibasita, teluros y seleniuros (naumanita y hessita) y sulfuros de metales base (esfalerita, galena y calcopirita). En el P4 precipitan sulfuros finos a gruesos junto a un cuarzo macizo, los minerales de mena se corresponden con sulfosales como la tetraedrita, y sulfuros de metales base. La evolución de los pulsos continúa hacia una composición donde predominan las arcillas verdes y las texturas brechosas en el P5. Continuo, aparece otro pulso silíceo y estéril (P6), con grandes cristales de adularia subrómbica. La secuencia sigue con un cuarzo microcristalino negro, masivo, de grano fino que posee la particularidad de exhibir molibdenita mostrando una extraña textura dendrítica (P7). En el pulso P8 actúan en simultáneo una componente hidráulica y otra tectónica, que generaron una brecha de matriz negra donde el cemento es masivo y posee anomalías de Mo; en ocasiones presenta pátinas azuladas que tiñen los clastos de los pulsos previos. Por último, se reconoce un evento menor que forma finas vetillas de carbonatos (P9). La mineralización se habría originado a partir del ascenso de soluciones cloruradas reducidas, con pH neutro a levemente alcalino, con salinidades del 7% NaCl eq. y con evidencias de ebullición; en tanto que los datos de isótopos estables establecen un origen producto de mezcla entre aguas meteóricas y magmáticas. La presencia de calcita de hábito hojoso, texturas de reemplazo de cuarzo y adularia pseudoacicular, bandeados coloformes y brechas, sumado a la coexistencia entre inclusiones fluidas ricas en fase vapor y líquido, evidencian a la ebullición como el factor responsable para la depositación metalífera. Por último, por las características observadas se puede clasificar ala Veta Inca como un sistema epitermal clásico de baja sulfuración, aunque ciertos atributos como las salinidades moderadas, la elevada relación Ag/Au, la presencia de sulfosales como tetraedrita, pirargirita y polibasita, y la presencia de esfalerita pobre en Fe, evidencian un estado de sulfuración intermedia., The Casposo district is located on the eastern edge of the Cordillera Frontal, Calingasta department, in the west of the San Juan province, Argentina. It consists of a larguest system of low sulfidation epithermal veins, within which there is an operating mine (currently inactive). Since the beginning of its activities in the year 2011 and until 2015, this mine produced a total of 283.200 oz of Au and 9,5 Moz of Ag. The geology of the deposit is characterized by outcrops of a marine sequence (La Puerta Formation), deposited between the Carboniferous and Early Permian, which was intensely deformed during the San Rafael orogenic phase (Lower Permian). Over this sequence, and through an important angular unconformity (San Rafael Surface), an important magmatism took place, represented by the Choiyoi Group, of subalkaline nature that evolved from calcalkaline to shoshonitic compositions. Between 269,7 Ma and 256,7 Ma (middle to upper Permian) this magmatism reached its highest intensity and volume, resulting in a thick pyroclastic sequence with the presence of intraformational unconformities (lower and upper section), which is intruded by subvolcanic bodies (Dacite Casposo and Andesita Cerro Pelado). This volcanism evolved synchronously with the intrusion of important large plutonic bodies such as the Casposo Granodiorite, which could potentially represent the deepest parts of the same magmatic system, although a major N-S fault separates both environments. During the terminal stages of this period, between 263,6 Ma and 256,7 Ma, the hydrothermal system responsible for the formation of the deposit would have been installed, in close association with a set of subvolcanic bodies called Felsic Dike and Felsic Intrusive. After the emplacement of the mineralization, and through a period of null magmatic activity of ~ 12 Ma, a reactivation of magmatism occurred from 249,7±2 Ma (Middle Triassic) that resulted in the intrusion of a succession of families of dykes of intermediate to acid compositions (Basic Dykes, Porphyritic Rhyolitic Dykes and Aplite Dykes). The deposit covers an area of approximately 100 km2 formed by veins that shows a marked compositional zoning: purely siliceous veins concentrated in the area of mine operations (Mercado, Aztec, B Vein, Inca), quartz-carbonate veins (Cerro Norte, Lucía), and purely carbonate veins with siliceous pulses (Oveja Negra, Aurora, Casposo Norte, Leñador and Julieta). The predominant textures are those of open space filling, such as colloform banding with the development of ginguros, crustiforms, cocards, massive and breccias with sulfide cement. From the detailed structural analysis carried out on the cross-sections and plans of the mine area, a vector of maximum NE-SW opening was determined, acting simultaneously with the formation of mineralization (syn-mineral control), which would have been affected by at least two subsequent faulting events (post-mineral control). From the detailed analysis of the mineralogy and texture of the Inca vein, 9 pulses were discriminated and grouped into 6 main episodes, being 5 of them of hydrothermal nature and 1 of tectonic-hydrothermal type. Pulses P1 and P2 are barren. Pulse P3 precipitates quartz-chalcedony with colloform banded texture, and subrhombic to pseudo-acicular adularia, with ore minerals hosted in dark gingurobands. The ore consists of electrum (10% Au - 90% Ag) and native silver, sulfosalts such as tetrahedrite (Ag-rich), pyrargyrite and polybasite, tellurides and selenides (naumanite and hessite) and base metal sulfides (sphalerite, galena and chalcopyrite). In P4, fine to coarse sulfides precipitate along with massive quartz, the ore minerals correspond to sulfosalts such as tetrahedrite, and base metal sulfides. The evolution of the pulses continues towards a composition dominated by green clays and brecciated textures in P5. Continuously, another siliceous and barren pulse appears (P6), with large crystals of subrhombic adularia. The sequence continues with a black, massive, fine-grained microcrystalline quartz that has the particularity of exhibiting molybdenite showing a strange dendritic texture (P7). In the P8 pulse, a hydraulic and a tectonic component act simultaneously, generating a black matrix breccia where the cement is massive and has Mo anomalies; sometimes it shows bluish patinas that stain the clasts of the previous pulses. Finally, a minor event that forms fine carbonate veins (P9) is recognized. The mineralization would have originated from the ascent of reduced chloride solutions, with neutral to slightly alkaline pH, with salinities of 7% NaCl eq. and with evidence of boiling, while the stable isotope data establish an origin product of mixing between meteoric and magmatic waters. The presence of platycalcite, quartz replacement textures and pseudoacicular adularia, colloform banding and breccias, along with the coexistence between vapor and liquid phase rich fluid inclusions, evidence boiling as the responsible factor for the ore deposition. Finally, due to the characteristics observed, the Inca Vein can be classified as a classic low sulfidation epithermal system, although certain attributes such as moderate salinities, high Ag/Au ratio, the presence of sulfosalts such as tetrahedrite, pyrargyrite and polybasite, and the presence of Fe-poor sphalerite, evidence an intermediate sulfidation state., Facultad de Ciencias Naturales y Museo

Терско-Каспийский прогиб – крупная структурно-тектоническая единица, расположенная на стыке двух разновозрастных и различных по составу элементов земной коры, которые из-за общей геодинами-ческой обстановки приобрели статус единого мегапрогиба с характерными литолого-стратиграфическими, термобарическими, геохимическими и нефтегенерационными характеристиками, что подтверждается гео-лого-геофизическими исследованиями и промышленными скоплениями в пределах пространства изуче-ния., The Terek-Caspian trough is a large structural-tectonic unit located at the junction of two elements of the Earth's crust of different ages and different composition, which, due to the general geodynamic condition, acquired the status of a united mega-trough with characteristic lithological and stratigraphic, thermo-baric, geochemical and oil-generating characteristics, which is confirmed by geological and geophysical studies and industrial accumula-tions within the study area.

The Himalaya are among the youngest and highest mountains in the world, but the exact timing of their uplift and origins of their biodiversity are still in debate. The Himalayan region is a relatively small area but with exceptional diversity and endemism. One common hypothesis to explain the rich montane diversity is uplift-driven diversification—that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We test this hypothesis in the Himalayan region using amphibians and reptiles, two environmentally sensitive vertebrate groups. In addition, analysis of diversification of the herpetofauna provides an independent source of information to test competing geological hypotheses of Himalayan orogenesis. We conclude that the origins of the Himalayan herpetofauna date to the early Paleocene, but that diversification of most groups was concentrated in the Miocene. There was an increase in both rates and modes of diversification during the early to middle Miocene, together with regional interchange (dispersal) between the Himalaya and adjacent regions. Our analyses support a recently proposed stepwise geological model of Himalayan uplift beginning in the Paleocene, with a subsequent rapid increase of uplifting during the Miocene, finally giving rise to the intensification of the modern South Asian Monsoon.

In this paper we present a series of thermo-mechanical experiments on continent-continent collision zones to investigate the role of lateral strength contrasts in terms of collision dynamics and orogen geometries. Our results show that differences in crustal rheology, may lead to a variety of different patterns of deformation and crustal geometries. Upper plate indentation forms a sequence of foreland propagating thrust units made of brittle upper crust on the lower plate. The strong deformation of the lower plate stands in stark contrast to the undeformed upper plate. In contrast, subduction of strong lithosphere beneath a weak upper plate forms a complex pattern of deformation. Deformation initiates on the lower plate and forms an antiformal stack made of brittle upper crust, before it indents the upper plate. Hence, deformation is present on both, the lower and upper plate, despite differences in initial strength. The outcome of this study has direct implications to natural collision zones, where differences in strength between the upper and lower plate exist. For example, along strike variability of upper vs. lower plate shortening in the Alps are likely to be controlled by contrasts in crustal strength. Furthermore, we suggest that the antiformal stack in the axial zone of the Pyrenees might indicate a strong lower plate at the onset of collision. Our results may therefore provide important constraints for the rheological state of continents during collision.

International audience; New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46°30’ and 47°30′S. The right lateral transtensional Marques–Zeballos Pass fault system (MZPRS) controlled the 800–1200 m uplift of the Andes at 16.1–18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10–15° westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148–178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif.The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge −1 segment (SCR −1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47°S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E–W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N–S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological “twin” of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in–depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3–4 Myr.

Swiss Journal of Geosciences, 106 (1), ISSN:1661-8734, ISSN:1661-8726

Evidence of two burial–exhumation cycles that took place during a single orogeny has been found in rocks belonging to the Piemonte unit of the Western Alps. An early high pressure event, which resulted from tectonic burial down to pressures of 1.5 GPa, was followed by exhumation to ca. 0.20–0.35 GPa as a result of extensional deformation. Renewed shortening culminated in a second burial episode down to pressures of 0.65–0.80 GPa, before the final exhumation took place. Existing geochronological data allow only ca. 13–19 Ma for the completion of both burial–exhumation cycles. Therefore, we suggest that the evolution of orogens is characterized by multiple short-lived burial–exhumation cycles related to orogen-scale alternance between shortening and extensional deformation.

[cat] Aquesta tesi doctoral descriu la cinemàtica dels Pirineus Basco-Cantàbrics, més concretament de la Plataforma Burgalesa, mitjançant la integració de i) geologia de superfície; ii) interpretació de línies sísmiques i pous; i iii) estudis paleomagnètics de rotacions d'eix vertical. La integració d'aquest conjunt de dades permet comprendre la relació entre la Plataforma Burgalesa i les conques d'avantpaís de l'Ebre i del Duero durant la orogènia Pirenaica. Les principals contribucions de la tesi són: i) Presentar un model estructural, el qual honora tots les restriccions imposades per l'estratigrafia, la preconfiguració de l'àrea prèvia a la deformació contractiva i les dades tant superficials com profundes. Aquest model permet comprendre com és la transició entre la deformació pel·licular present a l'est de la zona d'estudi i la deformació no pel·licular present a l'oest. ii) Reinterpretació de l'estructura de Zamanzas localitzada al nord de la Plataforma Burgalesa mitjançant el treball combinat entre geologia de superfície i les dades aportades per els pous d'exploració. iii) Aportar noves dades de vint-i-sis estacions de paleomagnetisme repartides per a la zona d'estudi i que permeten caracteritzar el patró de rotacions d'eix vertical. El resultat final és el de proposar un nou model per a l'evolució de la Plataforma Burgalesa que honra les restriccions imposades tant per la geologia de superfície com les dades d'exploració profunda disponibles fins a la data. Aquest model està caracteritzat per presentar deformació no pel·licular al sector oest mentre que quan el nivell de desenganxament augmenta de potència els encavalcaments es desenganxen i deformen la cobertora presentant un estil estructural pel·licular. Aquesta tesi ha demostrat que la pre-configuració tant de la conca extensiva pròpiament dita com la del seu voltant, tenen una forta implicació en el desenvolupament i estructuració de la Plataforma Burgalesa durant la Orogènia Pirenaica. És durant aquesta etapa en la qual es produeixen rotacions tant horàries com antihoràries en els diferents sectors mostrejats., [eng] This PhD Thesis describes the kinematics of the Burgalesa Platform in the Basque-Cantabrian Pyrenees by the integration of i) surface geology; ii) seismic and well data; and iii) vertical axis rotation paleomagnetic studies. The integration of all the data allow to understand the relationship between the Burgalesa Platform and the Ebro and Duero foreland basins during the Pyrenean Orogeny. The principal contribution of the Thesis is to present a new structural model, that fits all the constraints imposed by the stratigraphy, the pre-configuration of the area prior to the contractive deformation and both the deep and the surface data. This model allows to understand the transition between thin-skinned and the thick-skinned tectonics. The combined work between surface geology and well data has allowed to reinterpret the Zamanzas structure located at the northern boundary of the Burgalesa Platform. Previously, this structure had been interpreted as a set of extensional faults. This Thesis pointed out the mismatches and reinterpret the Zamanzas structure as a popup generated during the Pyrenean Orogeny. The combined interpretation of wells and seismic sections allow to partially comprehend the structure of the area during the extensional event as well as the result of the Pyrenean Orogeny occurred later. This study allowed to determine the distribution of the Lower Cretaceous depocenters during the North Atlantic and the Bay of Biscay opening. Moreover, during this stage salt mobilisation triggered by extension generated areas where the Triassic salt layer was thickened as demonstrated by the well data and the outcropping diapirs. This process accentuated the development of the depocenters. The extensional event also generated the onlap sedimentary geometries in the syn-rift sediments. The extensional model proposed is a combined model with the development of cover forced folding with salt migration at the southern boundary. The Triassic salt decoupled the extension between the basement and the cover and contractional structures were developed such as the back-thrust in the Huidobro area that produced the duplication of the Mesozoic. The early stages of the Pyrenean Orogeny resulted in the development of the San Pedro Structure, with north-directed and basement-involved thrusts, later fossilised by the Duero foreland sediments. To the north, the Burgalesa Platform, characterised by south-directed thrusts rooted into the Triassic salts, was southwards displaced until the San Pedro act as a backstop forcing the Burgalesa Platform to extrude laterally towards the southeast overriding the Ebro Foreland Basin. The paleomagnetic study focussed on determine the possible vertical axis rotations along the Pyrenees, denotes that the amount of sites that some areas have is not present in the Burgalesa Platform and vicinities that lack of sites. For that reason, another objective of this Thesis is to provide new paleomagnetic sites for the study area. The study carried out is made up of twenty-six new sites widely distributed and that allow to characterise the vertical axis rotation pattern. The results obtained reveals that i) the magnetisation of the Cenozoic sediments is prior to deformation and that ii) clockwise and counter clockwise rotation occurred in the Burgalesa Platform and adjacent areas. The evolution models previously proposed for the Burgalesa Platform were based either from surface geology of from geophysical data thus fitting some of the constraints. Because any model integrated all the observations and available data, a new model explaining the Burgalesa Platform evolution has been proposed. This model is characterised by presenting thick-skinned deformation at the western sector whereas, thin-skinned at the eastern one when the Triassic salt layer thickens point in which the thrusts are detach the cover from the basement. The results of this Thesis demonstrate that the pre-configuration of the extensional basin and its vicinities have a strong implication in the development and evolution of the Burgalesa Platform during the Pyrenean Orogeny. Finally, during this evolution, clockwise and counter clockwise rotations occurred in the different sectors as shown by the paleomagnetic studies carried out during this Thesis.

[spa] Los experimentos de multi-sísmicas realizados en el marco de la iniciativa del proyecto ALCUDIA incluyen una incidencia normal y sísmica gran angular de los conjuntos de datos de reflexión sísmica. Estos limitan las estructuras internas, la estructura detallada de la corteza y litosfera y, proporcionan el conocimiento necesario de las propiedades físicas a lo largo de la Zona Central Ibérica. Las imágenes sísmicas de incidencia normal se presentan de Sur a Norte: las estructuras de la Zona Ossa-Morena (Unidad Central), el ondulante domino Ibérico Central, los cuerpos intrusivos graníticos (Granitos de Mora, complejo Anatético de Toledo, etc.) hasta la falla de Toledo, justo al Sur de la cuenca del Tajo. La zona de estudio está caracterizada por una topografía ondulada debido a una serie de sinclinales y anticlinales. La imagen muestra una corteza inferior débilmente reflectante, ~13-18 km de espesor. La topografía sinodal refleja los pliegues, los sistemas de cabalgamientos imbricados, y fallas extensionales lístricas observados por los datos de sísmica de incidencia normal. A niveles más profundos las imágenes revelan estructuras arqueadas y laminares que sugieren estructuras como boundinage. Estas características son interrumpidas hacia el Sur, muy probablemente debido a la existencia de la zona de sutura. La expresión más profunda del afloramiento de la zona de sutura, está ligeramente desplazada hacia el Norte con respecto a su localización en superficie y, esta es vista como un cabalgamiento profundo de una fina capa de corteza inferior. Hacia el límite norte del perfil, debajo la falla de Toledo, una banda de reflectividad buzando hacia norte sugiere un adelgazamiento de la corteza inferior hacia el Norte. La discontinuidad de Mohorovicic se delimita como una fuerte disminución de la reflectividad a la base de la corteza inferior, localizada a unos ~31-33 km de profundidad (10.5 s tempo doble). Los datos de gran ángulo de sísmica de reflexión adquiridos a principios de mayo de 2012, tenían como objetivo proporcionar las distribuciones de las propiedades físicas (velocidades P y S, densidades, y el coeficiente de Poisson) de la corteza bajo la zona de estudio. Este perfil fue diseñado para ser casi coincidente con el perfil de incidencia normal. Los modelos de velocidad de P y S obtenidos revelan importantes variaciones laterales de velocidad en la corteza superior, que son coherentes con la observación de los afloramientos en superficie. La corteza inferior se identifica por un fuerte aumento de la velocidad a ~13 km y ~20 km de profundidad en Zona Central Ibérica y en la Cuenca del Tajo, respectivamente. La base de la corteza está fuertemente limitada por grandes amplitud de las llegadas de PmP y SmS y se encuentra a ~31 km en el extremo sur y a ~35,5 km por debajo del extremo norte del perfil de sísmica de gran ángulo. La sísmica de gran ángulo también se utilizó para producir low-fold stacks para las ondas P y las S. Esto se hizo para tomar una mirada más cercana a la discontinuidad de Moho, y para ser capaces de estimar la estructura interna y generar sismogramas sintéticos donde las fases PmP y SmS serían cualitativamente comparables a las fases observadas en los registros sísmicos. Esto dio lugar restricciones clave en la estructura de la discontinuidad de Moho bajo la Zona Central Ibérica y la Cuenca del Tajo en el orógeno Varisco del Macizo Central Ibérico. Las imágenes revelan una profundización gradual de ~31 km (10,2 s) en la Zona Central Ibérica a ~35,5 km (11,8 s) debajo de la cuenca del Tajo para la discontinuidad de Moho. Los datos sísmicos de gran ángulo y los resultados derivados de ellos son compatibles con las imágenes de incidencia normal., [eng] The multi-seismic experiments carried out under the ALCUDIA research initiative include a normal incidence and a wide-angle seismic reflection datasets. These constrain the internal architecture, the detailed crustal and lithospheric structure and, provide the necessary knowledge on physical properties across the Central Iberia Zone. The normal incidence seismic images from south to north: the suture zone of Ossa-Morena Zone (the Central Unit), the undulating Central Iberian domain, the intruded granitic bodies (the Mora Granite, the Toledo Anatectic complex, etc) up to the Toledo Fault, just south of the Tajo Basin. The study area is characterized by undulating topography characterized by a series of synclines and anticlines. The image shows a weakly reflective upper crust, ~13-18 km thick. The sinusoidal topography reflects the folding, the imbricate thrust systems, and listric extensional faults imaged by the normal incidence data. At deeper levels the image reveals arcuate and laminated events suggesting boudinage like structures. These features are disrupted in the south most probably due to the existence of the suture zone. The deep expression of the outcropping suture zone, is slightly displaced to the north with respect to its surface position and, it is imaged as an under-thrusting of a thin slice of lower crust. Towards the northern end of the transect, beneath the Toledo fault, a north dipping band of reflectivity suggest a significant thinning of the lower crust to the north. The Mohorovicic discontinuity is delineated as a sharp decrease in reflectivity at the base of the lower crust, located at ~31-33 km depth (10.5 s two-way travel-time). The wide-angle seismic reflection data acquired in early May 2012, was aimed to provide the distributions of the physical properties (P- and and S-wave velocities, densities, and Poisson’s ratio) of the crust beneath the study area. It was designed to be nearly coincident with the normal incidence profile. The obtained P- and S- wave velocity models reveal significant lateral velocity variations in the upper crust, which are consistent with the observation from the surface outcrops. The lower crust is identified by a sharp increase in velocity at ~13 km and ~20 km beneath the Central Iberian Zone and the Tajo Basin, respectively. The base of the crust is strongly constrained by the high amplitude PmP and SmS arrivals and it is located at ~31 km in the southern end and at ~35.5 km below the northern end of the wide-angle transect. The wide-angle was also used to produce low-fold P- and S-wave wide-angle stacks. This was done to take a closer look to the Moho discontinuity, and to be able to estimate the internal structure and generate synthetic seismograms in which the PmP and SmS would be qualitatively comparable to the phases observed in the shot records. This place key constraints on the structure of the Moho discontinuity beneath the Central Iberian Zone and the Tajo Basin in the Variscan orogen of the central Iberian Massif. The images reveal gradual deepening from ~31 km (10.2 s) in the Central Iberian Zone to ~35.5 km (11.8 s) beneath the Tajo Basin for the Moho discontinuity. The wide-angle seismic data and the results derived from it are compatible with the normal incidence images.

The kinematics and architecture of orogenic systems may be heavily influenced by climate, but little research has focused on the long-term effects of glacial erosion on orogenesis. Low-temperature thermochronometry and subsidiary structural, earthquake relocation, and offshore seismic reflection data from the St. Elias orogen are the basis for a new architectural model and demonstrate an association between glacial denudation and orogenic evolution. These data show that exhumation and deformation within the St. Elias orogen are focused across a thin-skinned fold and thrust belt on the windward flank, whereas the leeward flank functions as a deformational backstop. A previously unrecognized structure beneath the Bagley ice field separates these domains with south-side-up motion. This structure is interpreted to be a backthrust, making the orogen doubly-vergent. Suggestive of accelerated fault motion in response to climate change, bedrock cooling rates within the hanging wall of the backthrust and across the entire subaerial wedge accelerated ~ten-fold coeval with the onset of intense glacial conditions. Within the orogenic wedge, the zone of highest Quaternary exhumation (5 km/myr (±25%)) is focused around a narrow zone where the glacial equilibrium line altitude (ELA) intersects mean topography. This zone of rapid exhumation, not present prior to the onset of intense glacial conditions, cuts across the structural trend of the orogen and is more narrowly focused than the zone of orographic precipitation. Augmented glacial erosion around glacial ELA also coincided with a regional shift in deformation away from prominent forethrusts including the North American-Yakutat terrane suture (Chugach St. Elias fault) and the seaward deformation front (Pamplona zone). Accelerated denudation across the subaerial wedge thus appears to have forced the redistribution of strain along the backthrust and a series of forethrusts that lie beneath the zone of highest glacial flux, which in turn are systematically truncated by the backthrust. In a cause and effect response, the expansion of glaciers therefore appears to have resulted in an orogen scale structural reorganization and a narrowing of the orogenic wedge to preserve topographic slope. The focusing of long-term erosion around glacial ELA and the structural response of the orogenic wedge to Cenozoic climate change have not previously been observed in a real-world orogenic system and imply a high degree of coupling between climate and tectonics in this glacially-dominated orogen. Ph. D.

Artículo sobre el emplazamiento fallero en la zona de peridotitas de la Hispaniola (República Dominicana), estudiando si es la expresión orogénica de la polaridad reversa en la zona del Caribe en el cretácico medio. New structural data from central Hispaniola suggest that a mid-Cretaceous orogenicevent resulted in the obduction of peridotites onto the early Antillean arc. The MaimoŽn belt,which structurally underlies the peridotites, contains a shear zone composed of myloniticand phyllonitic schists formed by northward thrust emplacement of the peridotites. Penetrativedeformation decreases progressively to the northeast and is observed in the Neocomiansedimentary and volcanic rocks of the Los Ranchos Formation. The unconformablyoverlying, upper Albian Cenomanian limestones are not penetratively deformed, thusbracketing the obduction to Aptian-Albian time. This event is synchronous with chemicalchanges of the arc magmas in Hispaniola, Puerto Rico, and central Cuba. Thus, they mayboth be related to the postulated Greater Antillean polarity reversal.