The Bohemian Massif was consolidated during the Variscan orogeny (~400-300 Ma), which involved several oceanic subductions and collisions of continental micro-plates. The central part of the Bohemian Massif, the Moldanubian domain, shows a large accumulation of felsic high-pressure metamorphs. We present a numerical model of exhumation of these rocks due to continental collision and underthrusting. The key feature of the model is a felsic (light, rheologically weak and rich in radioactive elements) material in the lower crust of one of the colliding blocks. We examine the influence of the rate of convergence of the two blocks, radiogenic heating in the felsic lower crust and efficiency of erosion, on the model evolution and pressure-temperature conditions in the lower-crustal material. The models where the material is sufficiently weakened due to radiogenic heating show formation of an orogenic plateau, sedimentation in a foreland basin, and crustal thickening accompanied by gravity-driven exhumation of the lower crust and subsequent sub-horizontal flow in the middle crust. In colder and/or faster models, the thickening is dominated by folding. We correlate the tectonic style of these two types of models with differences between the high-grade rocks in the southern (Moldanubian) and northern (Sudetic) parts...

Study of the structural and metamorphic record of the eastern part of contact zone within Vepor and Gemer units in Central West Carpathians has interpreted the burial and exhumation in the evolution of alpine orogeny. The studied area is built by granitoid rocks of Vepor basement and metapelites of cover sequences both Vepor and Gemer units. Three structural fabrics have been identified in the area, which are correlated with so far described deformation stages. Higher metamorphosed rocks with presence of two generation garnets were found out within lower metamorphosed metapelites of cover sequences. From the garnet - biotite thermometry the metamorphic conditions for the rims were established to 550-580řC. Whereas muscovite and in some case chlorite, are the only metamorphic phases in neighbouring cover rocks. Three generations of white micas are documented within structural fabrics. The oldest muscovites, magmatic in origin (Ms1), younger phengites (Phg) present in fabrics S1 and youngest muscovites (Ms2) present in fabric S2. The study of quartz microstructures distinguished aggregates and from aggregates coming band microstructures. These are mostly found in deformed granitoids, sometimes also in cover quartzites and can have sigma-shape geometry. The aggregate microstructure, representing S1...

In September 2014, forty-three students were attacked and forcibly disappeared by police in the town of Iguala, Mexico. The Ayotzinapa Case, as it is known, caused international outcry and a domestic political crisis. In the following weeks, the surrounding countryside was discovered to be saturated with clandestine individual and mass graves, and a crisis emerged around bodily remains and their improper burial. As the willingness of the Mexican State to investigate became less and less credible, families of the disappeared —not just families of the students, but families of hundreds of other disappeared people across the country— took on the role of searching for their loved ones and caring for the name-less and unidentified dead they began to find. No longer waiting for authorities to act, kin of the disappeared began to symbolically and materially enact attributes of the State. What started as groups of people getting together on Sundays in the town of Iguala, to go to the hills in search of bodies in clandestine burials, grew in the following years into a nation-wide social movement. What does it mean to find a murdered body in Mexico today? What does it mean for it to become evidence? What work is done through the discovery by searching families of such bodies? The result of 32 months of ethnographic fieldwork in Mexico, between 2015 and 2021, this dissertation builds on anthropological scholarship on bureaucracy and forensic evidentiary practices to examine the encounters of relatives of the disappeared and State authorities. It analyses current regimes of justice and forensic expertise, interrogating how bodies in the ground are translated into terms legible to the law. This project investigates social processes of public truth production, forms of violence exerted by the State —through physical violence, forced disappearance, and bureaucratic violence— by bringing into conversation forensics alongside recent critical perspectives on bureaucracy, bearing in mind longstanding approaches to the anthropology of death and the anthropology of the State, to address how dead bodies become evidence and how truth claims circulate around and through them.

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The Pacific-North American plate boundary is typified by transpression and convergence, yet the relationship between interplate deformation and long-term crustal shortening is not fully understood. The continuous belt of rugged topography that extends along the entire plate boundary is generally associated with oblique tectonic plate motion, strong interplate coupling, and terrane accretion, but relating plate boundary orogenesis to variations in plate geometry and behavior requires detailed case studies. The northern San Gabriel Mountains along the San Andreas fault and the Chugach-Kenai Mountains above the Aleutian subduction zone are located along highly tectonically active sections of the Pacific-North American plate boundary and have not been studied from the context of long-term landscape development. To determine whether mountain building along these sections of the plate boundary reflects recent, rapid exhumation as observed in bordering mountain belts, low-temperature thermochronometry and topographic analyses were applied to each area. In the northern San Gabriel Mountains, apatite (U-Th)/He ages are >10 Ma along narrow crystalline ridges topped by low-slope erosional surfaces located within ~5 km of the San Andreas fault zone. In the Chugach-Kenai Mountains, the youngest apatite (U-Th)/He ages (~5 Ma) are an order of magnitude older than those from the Yakutat collision zone to the east, despite the presence of a continuous swath of glaciated, rugged topography between the two areas. Exhumation rates inferred from these ages are <1 mm/yr, suggesting that there has been minimal recent denudation in the northern San Gabriel and Chugach-Kenai Mountains. The lack of evidence for recent mountain building in both of these case studies implies that interplate deformation is heterogeneous and that other factors (secondary structures, climate) besides plate kinematics and topographic character must be considered for understanding landscape development. / Ph. D.

The Himalayan orogen provides an incredible natural laboratory to test models for continent-continent collision. The highest peaks of the Himalayas are composed of the Greater Himalayan Sequence (GHS), which is bound by a north-dipping low angle detachment fault above (South Tibetan detachment; STD) and by a thrust fault below (Main Central thrust; MCT). Assuming simultaneous movement on these features, the GHS can be modeled as a southward extruding wedge or channel. Channel flow models describe the coupling between mid-crustal flow, driven by gradients in lithostatic pressure between the Tibetan Plateau and the Indian plate, and focused denudation on the range front. Although the general geometry and shear sense criteria for these bounding shear zones has been documented, prior to this investigation, relatively few attempts had been made to quantify the spatial and temporal variation in flow path history for rocks from an exhumed section of the proposed mid-crustal channel. Results from this investigation demonstrate that mid-crustal flow at high deformation temperatures was distributed throughout the proposed channel. As these rocks began to exhume to shallower crustal conditions and therefore lower temperatures, deformation began to become partitioned away from the core of the channel and into the bounding shear zones. Based on these results a new method (Rigid Grain Net) to measure the relative contributions of pure and simple shear (vorticity) is proposed. Detailed thermobarometric analysis was conducted on rocks from the highest structural level in the Khumbu region, Nepal to construct pressure-temperature-time-deformation paths during the tectonic evolution of the GHS between ~32-16 Ma. Another aspect of the project suggests that the most active feature of the region is the N-S trending Ama Drime Massif (ADM). By combining new structural interpretation with existing remote sensing data this investigation proposes that the ADM is being exhumed during extension that is coupled with denudation in the trans-Himalayan Arun River gorge. Together these data provide important insights into the dynamic links between regional-scale climate and crustal-scale tectonics. / Ph. D.

L’architecture crustale et l’évolution de la partie profonde des marges passives peu-magmatiques sont encore mal comprises. En prenant comme chantier principal les marges Australie-Antarctique, cette thèse montre que l’enregistrement de la déformation dans les sédiments met en évidence une évolution polyphasée des marges distales. Cette évolution polyphasée implique le développement de multiples systèmes de détachement présentant une organisation hors-séquence et menant à une architecture finale symétrique des domaines exhumés. Cette organisation des systèmes de failles est liée à des cycles de délocalisation / relocalisation de la déformation influencés par l’apport magmatique, par un niveau de découplage et par la remontée asthénosphérique. L’interaction faille / magma apparait particulièrement importante dans l’évolution des marges distales. Cette étude a permis de mieux caractériser la rupture lithosphérique, qui peut se définir comme un événement tectono-magmatique progressif. / The crustal architecture and evolution of the deepest part of magma-poor rifted margins is currently not well understood. Taking the Australia-Antarctica margins as main study area, this thesis shows that the record of the deformation in sediments highlights a clear polyphase evolution of distal margins. This polyphase evolution implies the development of multiple detachment systems presenting an out-of-sequence organization and leading to a final symmetric architecture of the exhumed domains. This organization of fault systems is linked to cycles of delocalisation / re-localisation of the deformation influenced by the magmatic supply, by a decoupling level and by the asthenospheric uplift. Fault / magma interaction appears particularly important during the evolution of distal margins. This study allowed a better characterization of the lithospheric breakup, which can be defined as a progressive tectono-magmatic event.

Cette thèse est centrée sur la caractérisation des traceurs des fluides qui interagissent avec les roches du socle et les roches sédimentaires dans les systèmes riftés hyper-amincis exposés dans la Téthys alpine, les Pyrénées et Ibérie-Terre Neuve. L’étude de ces fluides est basée sur les observations géologiques, les analyses géochimiques et les données géophysiques. Deux types de fluides ont été identifiés : les fluides associés à la croûte continentale, avec une signature caractérisée par Si et Ca, ainsi que les fluides liés au manteau en exhumation, avec une signature caractérisée par Si, Mg, Fe, Mn, Ca, Ni, Cr et V. La percolation des fluides est fortement liée à la formation des failles de détachement et à l’évolution des systèmes hyper-amincis. Le flux de fluides dans ces systèmes a des implications importantes pour les changements rhéologiques, pour la nature des sédiments et pour les modifications chimiques des réservoirs de la Terre. / This thesis focus in the identification of geochemical tracers and effects of fluid that interact with basement and sedimentary rocks in hyperextended systems. The investigation of such fluids is based on geological observation, geochemical analyses and geophysical data from fossil hyperextended rift systems exposed in the Alps and in the West Pyrenees, and the present-day distal margins of Iberia and Newfoundland. Two types of fluids were identified during this study. The first type, referred to as continental crust-related fluids, has a signature of Si and Ca. The second type, referred to as mantle-related fluids, has a signature of Si, Mg, Fe, Mn, Ca, Ni, Cr and V. The fluid percolation is strongly related to the formation of extensional detachment faults and the evolution of hyperextended systems. Fluid flow in these systems has major implications for the nature of sediments, rheological changes and chemical modifications of the Earth’s reservoirs throughout its evolution.